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A General Reference Work " : 


Prepared by a Staff of 


Illustrated zuith over Fifteen Hundred Engravings 





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COPYRIGHT, 1909, 1910. 1912, 1915. 1916, 1917. 1918, 1919, 1920. 1921 

Copyrighted in Great Britain 
All Rights Reserved 

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Authors and Collaborators 


President and General Manager, The Stirling Press, New York City 

Member, Society of Automotive Engineers 

Member, The Aeronautical Society 

Formerly Secretary, Society of Automotive Engineers 

Formerly Engineering Editor, The Automobile 


Automobile Engineer 

With Inter-State Motor Company, Muncie, Indiana 

Formerly Manager, The Ziegler Company, Chicago 


Editor, Automotive Engineering 

Formerly Managing Editor, Motor Life; Editor, The Commercial Vehicle, etc. 

Author of "What Every Automobile Owner Should Know" 

Member, Society of Automotive Engineers 

Member, American Society 6f Mechanical Engineers 


Late Editor, Motor Age, Chicago 
Formerly Managing Editor, The Light Car 
Member, Society of Automotive Engineers 
American Automobile Association 


Formerly Secretary and Educational Director, American School of Correspond- 
Formerly Instructor in Physics, The University of Chicago 
American Physical Society 


Late Lecturer, Automobile Division, Milwaukee Central Continuation School 
Editorial Representative, Commercial Car Journal and Automobile Trade Journal 
Member, Society of Automotive Engineers 
Member, Standards Committee of S. A. E. 
Formerly Technical Editor, The Light Car 


Authors and Collaborators— Continued 


Professor of Industrial Engineering, Pennsylvania State College 
American Society of Mechanical Engineers 


Specialist in Technical Advertising 
Member, Society of Automotive Engineers 
Formerly Associate Editor, The Automobile 


Consulting Mechanical Engineer, Chicago 
American Society of Mechanical Engineers 


Superintendent, Union Malleable Iron Company, East Moline, Illinois 


Formerly Dean and Head, Consulting Department, American School of Cor- 
Member, American Society of Mechanical Engineers 


Head, Automobile Engineering Department, American School of Correspond- 
Member, Society of Automotive Engineers 
Formerly Lecturer, Federal Association of Automobile Engineers, Chicago 


President, W. R. Howell and Company, London, England 


Associate Editor, Motor Age, Chicago 


Head, Publication Department, American Technical Society 

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Authorities Consulted 

THE editors have freely consulted the standard technical litera- 
ture of America and Europe in the preparation of these 
volumes. They desire to express their indebtedness, particu- 
larly^ to the following eminent authorities, whose well-known treatises 
should be in the library of everyone interested in the Automobile and 
allied subjects. 

Grateful acknowledgment is here made also for the invaluable 
co-operation of the foremost Automobile Firms and Manufacturers 
in making these volumes thoroughly representative of the very latest 
and best practice in the design, construction, and operation of Auto- 
mobiles, Commercial Vehicles, Motorcycles, etc.; also for the valu- 
able drawings, data, illustrations, suggestions, criticisms, and other 


Consulting Engineer 

First Vice-President, American Motor League 

Author of "Roadside Troubles" 


Late Consulting Engineer 

Past President of the American Society of Civil Engineers 

Author of "Artificial Flight," etc. 


Member, American Society of Mechanical Engineers 

Author of "Gas-Engine Handbook," "Gas Engines and Their Troubles," "The 
Automobile Pocket-Book," etc. 


Member, American Society of Mechanical Engineers 
Engineer, General Electric Company 
Author of "Elements of Gas Engine Design" 


Author of "Horseless Vehicles, Automobiles, and Motorcycles," "Gas, Gasoline, 
and Oil Engines," "Mechanical Movements, Powers, and Devices," etc. 


Associate Member, American Institute of Electrical Engineers 
Author of "The Storage Battery : A Practical Treatise on the Construction, 
Theory, and Use of Secondary Batteries" 

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Authorities Consulted— Continued 


Director, H. J. Willard Company Automobile School 
Author of "The Complete Automobile Instructor" 


Editor, The American Cyclopedia of the Automobile 

Author of "Motor Boats," "History of the Automobile," "Automobile Driving, 

Self-Taught," "Automobile Motors and Mechanism," "Ignition Timing 

and Valve Setting," etc. 


Mechanical Engineering Department, Columbia University 
Author of "Gas Engine Design" 

P. M. HELDT ** 

Editor, Horseless Age 

Author of "The Gasoline Automobile" 


Professor of Experimental Engineering, Sibley College, Cornell University 
Author of "Internal Combustion Engines" 


Author of "Light Motor Cars and Voiturettes," "Motor Repairing for Ama- 
teurs," etc. 


Professor of Mechanical and Electrical Engineering in University College, 

Author of "Gas and Petroleum Engines" 


Member, Institution of Automobile Engineers 
Author of "Motor-Car Mechanisms and Management" 


Professor of Experimental Engineering, Sibley College, Cornell University 
Author of "Internal Combustion Engines" 


Technical Director, The New York School of Automobile Engineers 
Author of "Motor-Car Principles" ** 

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Authorities Consulted— Continued 


Formerly Editor, Motor Age 

Author of "Automobile Troubles, and How to Remedy Them" 


Associate Member, Institute of Electrical Engineers 
Author of "Electric Ignition for Motor Vehicles" 


Member, American Society of Civil Engineers 
British Association for the Advancement of Science 
Chevalier Legion d'Honneur 
Author of "Artificial and Natural Flight," etc. 


Author of "Complete Automobile Record," "A B C of Motoring" 


Lecturer on Manufacture and Application of Industrial Alcohol, at the Poly- 
technic Institute, London 
Author of "Industrial Alcohol," etc. 


Consulting Engineer 

Author of "Modern Gas and Oil Engines" 


Head of Department of Electrical Engineering, Columbia University 
Past President, American Institute of Electrical Engineers 
Author of "Electric Lighting," Joint Author of "Management of Electrical 


Captain and Instructor in the Prussian Aeronautic Corps 
Author of "Airships Past and Present" 


Associate Member, Institute of Mechanical Engineers 
Author of "Petrol Motors and Motor Cars" 

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Authorities Consulted— Continued 


Director of Sibley College, Cornell University 

Author of "Manual of the Steam Engine," "Manual of Steam Boilers," etc. 


Motoring Editor, The London Sphere 
Author of "The Amateur Motorist" 


Major and Battalions Kommandeur in Badischen Fussartillerie 
Author of "Pocket-Book of Aeronautics" 


Professor of Steam Engineering, Massachusetts Institute of Technology 
Author of "Steam Boilers" 


Author of "Operation, Care, and Repair of Automobiles" 


Author of "Motor Boats," etc. 


Editor, Work and Building World 
Author of "Motorcycle Building" 


Author of "Self-Propelled Vehicles" 


Editor, The Encyclopedia of Motoring, Motor New8, etc. 


Author of "Ignition Devices," "Magnetos for Automobiles," etc. 


Consulting Electrical Engineer 

Associate Member, American Institute of Electrical Engineers 

Author of "Storage Battery Engineering" 

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THE period of evolution of the automobile does not 
span many years, but the evolution has been none 
the less spectacular and complete. From a creature 
of sudden caprices and uncertain behavior, it has become 
today a well-behaved thoroughbred of known habits and 
perfect reliability. The driver no longer needs to carry war 
clothes in momentary expectation of a call to the front. 
He sits in his seat, starts his motor by pressing a button 
with his hand or foot, and probably for weeks on end will 
not need to do anything more serious than feed his animal 
gasoline or oil, screw up a few grease cups, and pump up a 
tire or two. 

C, And yet, the traveling along this road of reliability and 
mechanical perfection has not been easy, and the grades 
have not been negotiated or the heights reached without 
many trials and failures. The application of the internal- 
combustion motor, the electric motor, the storage battery, 
and the steam engine to the development of the modern 
types of mechanically propelled road carriages has been a 
far-reaching engineering problem of great difficulty. 
Nevertheless, through the aid of the best scientific and me- 
chanical minds in this and other countries, every detail 
has received the amount of attention necessary to make it 
as perfect as possible. Road troubles, except in connection 
with tires, have become almost negligible and even the 
inexperienced driver, who knows barely enough to keep to 
the road and shift gears properly, can venture on long tour- 
ing trips without fear of getting stranded. The refinements 
in the ignition, starting, and lighting systems have added 
greatly to the pleasure in running the car. Altogether, the 
automobile as a whole has become standardized, and unless 
some unforeseen developments are brought about, future 
changes in either the gasoline or the electric automobile 
will be merely along the line of greater refinement of the 
mechanical and electrical devices used. 

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C, Notwithstanding the high degree of reliability already 
spoken of, the cars, as they get older, will need the atten- 
tion of the repair man. This is particularly true of the 
cars two and three seasons old. A special effort, therefore, 
has been made to furnish information which will be of value 
to the men whose duty it is to revive the faltering action of 
the motor and to take care of the other internal troubles 
in the machine. 

C, Special effort has been made to emphasize the treatment 
of the Electrical Equipment of Gasoline Cars, not only be- 
cause it is in this direction that most of the improvements 
have lately taken place but also because this department of 
automobile construction is least familiar to the repair men 
and others interested in the details of the automobile. A 
multitude of diagrams have been supplied showing the con- 
structive features and wiring circuits of the majority of 
the systems. In addition to this instructive section, par- 
ticular attention is called to the articles on Welding, Shop 
Information, Electrical Eepairs, and Ford Construction 
and Repair. 

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Table of Contents 


Gasoline Automobiles (continued) 

By Morris A. Hall. Revised by J. R. Bayston t Page *11 

Clutches: Classification, Cone Type, Disc Type, Plate Type— Clutch 
Operation: Methods, Gradual Release, Lubrication, Bearings, Adjust- 
ment, Accessibility, Clutch Troubles and Remedies (Slipping: Clutch, 
Clutch Leathers, Clutch Springs, Fierce Clutch, Ford Clutch, Spinning, 
Cork Inserts, Adjusting Clutch Pedals, Summary of Troubles) — Trans- 
missions: Classification, Sliding Gear (Selective, Progressive, Modern 
Selective, Transmission Location, Interlocking Devices, Electrically Op- 
erated Gears, Pneumatic Shifting System). Planetary Gears (Method of 
Action, Ford Planetary Type), Miscellaneous (Freak Drives, Cable and 
Rope, Hydraulic, Electric, Electric Transmissions). Transmission Trou- 
bles and Repairs (Heating, Gear Pullers, Pressing Gears on Shafts, Diag- 
nosis, Poor Gear Shifting, Cleaning Gears, Transmission Stands, Modern 
Transmission Repair) — Gears: Types of Gear-Cutting Machines, Types 
of Gears in Automobiles (Spur, Bevel, Helical, and Herringbone, Spiral, 
Spiral -Bevel, Worm) — Questions and Answers — Steering: Group: Steer- 
ing Gears: Front Axle Steering, Characteristics of Steering Gears, Spur 
and Bevel Type, "Worm Gear Type, Ford Steering Gear, Semi-Reversible 
Gear, Steering-Gear Assembly Troubles and Repairs — Steering Wheels — 
Steerin&r Rods — Special Types of Drive: Front-Wheel Drive, Four-Wheel 
Drive, Four-Wheel Steering Arrangement, Electric Drive — Front Axles: 
Classification, Elliott Type, Reversed Elliott Type, Lemoine Type, Ma- 
terials, Axle Bearings, Front Axle Troubles and Repairs — Chassis Group: 
Frames: Pressed-Steel Frame, Sub-Frames, Frame Troubles and Re- 
pairs — Springs: Semi-Elliptic, Three-Quarter Elliptic, Platform, Canti- 
lever, Hotchkiss, Unconventional Types, Spring Troubles and Remedies — 
Shock Absorbers — Questions and Answers — Final-Drive Group: Rear 
Axle: Units and Final Drive, Universal Joints, Fabric Joints, Final 
Drives, Torque Bar and Its Function, Driving Reaction, Types of Rear 
Axles, Rear- Axle Troubles and Repairs — Brakes: Classification, Ex- 
ternal-Contracting Brakes, Internal-Expanding Brakes, Double Brake 
Drum for Safety, Brake Operation, Adjustments, Lubrication, Electric 
Brakes, Hydraulic Brakes, Vacuum Brakes, Brake Troubles and. Repairs 
— Wheels: Pleasure-Car Wheels, Commercial-Car Wheels, Wheel 
Troubles and Repairs — Tires: Classification, Changing Tires, Recent 
Improvements — Rims: Plain Rims, Clincher Rims, Quick-Detachable 
Rims, Standard Sizes of Tires and Rims, Tire Construction, Tire Repairs, 
Vulcanization of Tires, Types of Vulcanizing Outfits, Vulcanizing Kettles, 
Inside Casing Forms, Side Wall Vulcanizer, Layouts of Equipment, Small 
Tool Equipment, Inner Tube Repairs, Outer Casing Repairs 

Electrical Equipment for Gasoline Cars . . . . . 

. . By Charles B. Hayward. Revised by J. R. Bayston Page 351 

Electrical Principles: Electric Circuit: Current, Electrical Pressure, 
Resistance, Ohm's Law, Power Unit, Conductors, Voltage Drop, Circuits, 
Short-Circuits and Grounds, Size of Conductors, Heating Effect of Cur- 
rent, Chemical Effect of Current — Magnetism: Natural and Artificial 
Magnets, Poles, Electromagnets, Magnetic Field, Lines of Force, Sole- 
noids — Induction Principles in Generators and Motors: Induction, Self- 
induction, Condensers, Pressure and Voltage, Power Comparison, Gener- 
ator Principles (Elementary Dynamo, Commutators, Armature Windings, 
Field Magnets, Brushes), Electric Motor Principles (Theory of Opera- 
tion, Counter E. M. F., Types, Dynamotors, Batteries) — Summary of 
Electrical Principles (General, Ohm's Law, Magnetism, Induction, Con- 
ductors, High -Tension Currents, Circuits, Hydraulic Analogue, Gener- 
ator Principles, Motor Principles, Batteries) 

Index Page 430 

♦For page numbers, see foot of pages. 

fFor professional standing of authors, see list of Authors and Collabo- 
rators at front of volume. 

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Classification. Principal among the indispensable parts inter- 
vening between engine and road wheels, and one which may be a 
source of great joy or correspondingly great wrath, according to 
whether it be well or poorly designed and fitted, is the clutch. There 
are three forms into which clutches may be divided, all of which are 
in general use in the automobile. These different forms are: 

(1) Cone clutches 

(2) Disc clutches 

(3) Plate clutches 

The necessity for a clutch lies in the fact that the best results 
are obtained in an automobile engine when run at constant speed. 
In as much as the speed of the car cannot, from the nature of its use, 
be constant, it requires some form of speed variator. This is the 
usual gear box, or transmission, but, in addition, there is the necessity 
of disconnecting it from the motor upon starting, since the engine 
cannot start under a load. There is also the necessity for disconnect- 
ing the two when it is desired to change from one speed to another 
either by way of an increase or a decrease. So, also, when one wishes 
to stop the car, there must be some form of disconnection. There 
are, then, three real and weighty reasons for having a clutch. 

Requirements Applying to All Clutches. In a serviceable clutch 
there are two general requirements which are applicable to all forms. 
These are gradual engagement and large contact surfaces, although 
the latter requirement may be made to lose much of its force by 
making the surfaces very efficient. In the cone clutch, gradual 
engaging qualities are secured by placing a series of flat springs under 
the leather or clutch lining. By means of these springs, acting against 
the main clutch spring, the clutch does not grab, since the large 


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spring must have time in which to overcome the numerous small 
springs. In this way, the engagement is gradual and the progress of 
the car is easy as well as continuous. 

The specific necessity in a cone clutch is a two-fold one — 
sufficient friction surface and proper angularity. The latter, in a 
way, affects the former, as will be discussed more in detail later. 

The angularity varies in 
practice from 8 to 18 

Cone Clutch. The 
cone clutch consists of 
two members, one fixed 
on the flywheel or other 
rotating part of the en- 
gine and the other fixed 
to the transmission shaft. 
The latter usually slides 
upon the shaft so as to 
allow engagement and 
disengagement, .a spring 
holding the two together. 
When the smaller-diam- 
eter member is spoken 
of, it is usually called the 
male member, while the 
part of larger size is 

Fig. 246. Section through Studebaker S P° ken ° f aS the f emaIe 

Direct Cone Clutch member 

Courtesy of Studebaker Corporation, Detroit, Michigan 

An excellent exam- 
ple of the direct cone clutch is seen in Fig. 246, which shows the 
Studebaker clutch in section. The noticeable point about this 
clutch is its simplicity. It will be noted that the spring is entirely 
enclosed, so that when it needs adjusting the repair man must 
open the universal joint and operate the bolt A which regulates the 
tension of the spring. 

Another good example of the simplicity of the cone clutch is seen 
in Fig. 247, which is an aluminum member with bosses cast for cork 
inserts. Between the inserts may be seen the flat heads of the copper 


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rivets which hold the clutch facing in place. Obviously, this has the 
same disadvantage of internal, and thus inaccessible, spring. 

In the cone type of clutch, shown in Fig. 248, the inaccessible 
spring is avoided. In addition, a number of small springs are used in 
place of one very large and very stiff one. The ease of adjustment 
and the greater ease in handling the springs make this clutch a 
much better design for average use from the repair man's point 
of view. 

Disc Clutch. With its advent in 1904, the multiple-disc clutch 
has steadily grown in popularity, until today it is looked upon as the 

Fig. 247. Direct Cone Clutch with Cork Inserts 

most satisfactory solution of the difficult clutch problem. Designers 
who have once adopted it, seldom, if ever, go back to another form, 
while of the new cars coming out from time to time nearly three- 
fourths are equipped with some form of disc clutch. 

Popularity Compared with Other Forms. Statistics for 1914 
showed that the disc form of clutch was easily the most popular type. 
Of 230 different chassis for 1914, there were 119 chassis which were 
equipped with disc clutches, 97 with the cone, 9 with a contracting- 
band type, while there were but 5 with an expanding-band form. 
The relative figures for 1916 were about 94 disc, 81 cone, no contract- 





ing band, no expanding band, and 1 electric. This would give the 
first-named approximately 54 per cent of the total. 

The 1920 chassis show about 85 per cent disc and about 14 per 
cent cone. 

Two Forms of Same Make. Reference to the types of clutch 
brings to mind the relative advantages of the two leaders, the cone 


Fig. 248. Direct Cone Clutch with Small Springs and 
External Adjustment 
Courtesy of Willys-Overland Company, Toledo, Ohio 

and the disc. These are presented in a very striking manner in 
Figs. 251 and 252, which show the cone and disc clutches used inter-^ 
changeably by the Warner Gear Company, Toledo. These clutches 
are designed to be interchangeable, consequently the general layout 
is the same. It will be noted that the cone is somewhat simpler than 
the disc, as it has fewer parts which take up room. The design is such 
that the internal spring of the cone can be adjusted from the outside. 


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as can the outside spring of the disc. An interesting point in this 
connection is that the transmissions also are interchangeable, although 
the type, Fig. 252, with roller bearings is intended for a moderately 
heavy passenger car, while that in Fig. 251 is for lighter work. 

Simple Types. The simple types differ in number and shape of 
discs, method of clutching, material, and lubrication; but in principle 
all are alike. This clutch is one in which the flat surfaces properly 
pressed together will transmit more power with less trouble than any 

Fig. 251. Typical Three-Speed Gearset with Cone Clutch for Unit Power Plant 
Courtesy of Warner Gear Company, Toledo, Ohio 

other form. By multiplying the number of surfaces and making 
them infinitely thin, the power transmitted may be increased indefi- 
nitely. That this is not idle fancy is shown by a number of very 
successful installations of 1000 horsepower and over in marine service. 
The minimum number of plates in use is said to be three, but 
very often the construction of a three-plate clutch is such that one or 
two surfaces of other parts are utilized, making it a two- or even one- 
plate clutch in reality. In the Warner clutch, shown in Fig. 252, 
there are really but two clutching surfaces, the face of the inner plate 


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against the flywheel and the outer face against the engaging disc. 
Both plates are faced with suitable friction surface but it really is a 
one-disc clutch. 

Multiple-Disc Clutches. The modern tendency in disc clutches, 
however, is away from those of few plates requiring a very high 
spring pressure — since the friction area is necessarily limited — 
toward the multiple-disc variety, in which a very large area is 
obtained. The large area needs a very light spring pressure, and 

Fig. 252. Typical Three-Speed Warner Gear Box Shown in Fig. 251, but with Disc Clutch 

consequently it is easier to engage and disengage the clutch. For this 
reason, the multiple disc is becoming more popular with owners and 
drivers than the variety requiring the extra-heavy effort. The con- 
struction of the three-plate disc clutch does not differ radically from 
one maker to another. Three fingers are used to clutch and declutch 
generally, the amount of movement being adjustable. A single spring 
of large diameter and large-size wire is generally used, and sheet steel 
is used for one-half the clutch plates. Between the three-plate and 
multiple-disc are many gradations. 


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In the true multiple-plate clutch, there are three general varieties 
met with in practice: the metal-to-metal with straight faces; the 
metal-to-metal with angular or other shaped faces designed to 
increase the holding power; and the straight-face kind in which metal 
does not contact with metal, one member either being lined with a 
removable lining or fitted with cork inserts. 

Metal-to-Metal Dry-Disc Type. The metal-to-metal method has 
the additional advantage of having the central part within which the 
clutch is housed very small in diameter, so that the portion of the fly- 
wheel between the rim and the clutch housing may be made in the 

Fig. 253. Multiple-Disc Clutch and Transmission of Winton Cars 
Courtesy of Winton Motor Car Company, Cleveland, Ohio 

form of fan spokes that convert it into a fan which serves to cool the 
motor better. 

As the various examples of disc clutch shown would indicate, 
the designer has had his choice between a few large discs and a large 
number of small ones. If he chose the former, the clutch could be 
housed within the flywheel, but that would make it inaccessible. If he 
chose the latter, the clutch could not be kept within the flywheel 
length. A separate clutch housing would be a necessity, but the 
clutch could be made accessible and flywheel fan blades could be used. 

Another example of the plain metal-to-metal disc clutch is shown 
in Fig. 253. In this case also the clutch is not housed in the flywheel, 


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as in most of the preceding examples of this form of clutch, but in the 
forward end of the transmission case, that is, instead of motor and 
clutch forming a unit, the clutch is a unit with the transmission. It is 
claimed that this position makes it more accessible, since it brings the 
clutch directly under the floor boards of the driver's compartment 
where it can be lubricated better. The lubrication is effected through 
communication with the gear part of the case, which is always filled 
with lubricant. 

In the figure it will be noted that there are 13 driven discs, with 
keyways, which hold them to the driven drum. Note that the drum 
is held to its shaft by means of a pair of large set screws. The clutch- 
ing springs are of small diameter and size, spaced equally around the 
periphery of the discs; each disc is enclosed in a small and thin metal 
casing. Attention is called also to the universal joint shown. This 
joint forms the rear end of the driving connection with the flywheel, 
which will be referred to later. These discs are flat-stamped out of 
sheet steel with the proper keyways for internal or external holdings. 

Use of Facings. The more modern disc clutch has two sets 
of sheet metal discs, one of which is faced on one or both sides with 
a special material. Without a single exception, all the disc clutches 
shown have had plain discs against plain discs. This makes a simple 
and fairly inexpensive construction, but one that is not very efficient. 
The most recent tests have shown that metal against metal gives a 
coefficient of friction of but .15, which is reduced to .07 when the 
surfaces become oily or greasy. With one of these contacting faces 
lined with leather, the coefficient rises to .23 when dry and to .15 when 
oiled. Again if fiber is used for the facing, the coefficient becomes, 
respectively, .27 and .10, while with cork or with cork and leather, it 
becomes, respectively, .35 and .32. Here is a very apparent reason 
for (1) facing the clutch discs, and (2) running them dry. 

By going over these figures, it will be noted that discs with 
almost any form of facing will show an increase in efficiency over the 
same discs without facing, varying from 60 up to almost 300 per 
cent. Again, any form of disc clutch, faced or otherwise, will show 
a much higher coefficient when dry than when oiled and thus a 
greater efficiency. These two facts point out the obvious reasons 
for the modern tendency toward the multiple-disc clutch, faced and 
running dry. 


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To present an example of the faced type, Fig. 254 shows the 
multiple-disc clutch of the eight-cylinder V-type Cadillac. In this 
illustration the eight driving discs can be seen with the facing on 
each side of each one; This facing is of wire-mesh asbestos, and 
between each pair of discs comes a plain driven disc, so that it has a 
facing of the asbestos against each side of the metal which it grips. 
The keys holding the inner discs to the shaft can be seen on the 

Fig. 254. 1917 Cadillac Clutch and Transmission, Showing New Clutch Drive 
Courtesy of Cadillac Motor Car Company, Detroit, Michigan 

end of the housing, while the slots into which the keys project can 
be seen on the discs. By examining the group closely, the driven 
plain discs can be seen between each pair of the drivers. The 
method of driving these discs through a multiplicity of keys and 
grooves is unusual, but it is a good example of Cadillac thoroughness. 
Fig. 254 also shows the pedals and the exterior of the clutch case 
where it bolts up to the engine. This indicates how a unit power 
plant simplifies the control group and eliminates parts. 


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Floating Discs a Novelty. The clutch on Locomobile cars, 
shown in section in Fig. 255, is very much like the Cadillac just 
shown, except for the novel feature that the fabric facings are not 
attached either to the driving or to the driven discs but float between 
them. This fabric, usually a woven asbestos material with a central 
core of interwoven metal wires, instead of being attached to both 
sides of every other disc or to one side of every disc, is not attached 
at all. The rings for the fabric discs are made up in the form of 
annular rings. They have the same inner diameter as the inside of the 

Fig. 255. Floating Dry-Disc Clutch Used on Locomobile Cars 

driving discs and the same outside size as the driven discs; conse- 
quently, assembling one of these clutches is simply a question of 
piling first a driven disc, then a fabric, then a driving disc, and so on. 

The fact that the fabric rings are not united to either of the 
metal discs allows them to free themselves with remarkable rapidity 
so that either on engagement or on declutching the action is very quick . 

Greater Power Transmitted by Surfaces Not Plane. To increase 
the power transmitted by a clutch of given size, either the number of 
plates must be increased or the form of the surface changed. The 
latter method was followed on the clutch of the French car "Ours." 


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The discs of this unusual clutch had a perfectly flat outer portion 
and a conical inner portion, only the latter taking part in the trans- 
mission of power. In this disc form, then, we have the advantage 
of the disc economy of space, together with the advantages of the 
cone clutch and the additive gain of running in a bath of oil. 

Another form utilizing this principle, and one that is more widely 
used, is that known as the "Hele-Shaw" so named from its inventor, 
the famous English scientist, Dr. H. S. Hele-Shaw. This is essen- 
tially a flat disc, as shown at A, Fig. 256, with a ridge B at about 
the middle of the friction surface; this ridge consists of a portion 

Fig. 256. Hele-Shaw Disc Clutch, Showing Cone Surfaces 

of the surface, which has been obtruded during the stamping process 
in such a way as to leave the surface of the ridge in the form of an 
angle of small height. The angle used is 35 degrees, and this value has 
been determined upon experimentally as the best. Fig. 256 shows a 
cross-section through an assembled clutch, which reveals the clutch 
angle very plainly. In use, the ridges nest one on top of the other; 
and in the extreme act of clutching, not only the flat surfaces but 
both sides of the ridge are in contact with the next plate. Thus, not 
only is the surface for a given diameter increased, but the wedge 
shape is also taken advantage of. 


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In taking the clutch apart, first throw it out and lock out the 
spring by placing a space-block If inches high and 4 inches long 
between the cover and the throw-out yoke at E. 

The two asbestos rings should be loose in their seats. When 
assembling, these rings should be coated on all sides with a thin 
layer of non-acid grease or cylinder oil. About every thousand 
miles, remove the adjusting screw and squirt a little oil into the clutch 
to moisten the asbestos mats. Too much oil will cause the clutch 
to slip until the oil is burned out. 

The incline thrust ring should slide freely on the three drive 
pins in the flywheel. 

It is good practice to block out the clutch to prevent it from 
becoming set, if the car is stored for any long period. 

If the clutch needs cleaning, remove the adjusting screw and 
pour ^ pint of kerosene into the clutch; let the motor run for fifteen 
minutes and then drain the clutch by letting the car stand over night 
with the front wheels at a higher position than the rear wheels. 

Magnetic Clutches. A great deal of experimental work has 
been done with clutches operating on the magnetic principle. A 
magnet of large size and strength has a great pulling power that can 
be applied to an iron or steel member. In the electric clutch the 
main purpose was to devise some means of controlling the strength 
of these magnets so that they could be strengthened or weakened 
and cause the clutch to hold, slip, or disengage entirely. The strength 
of an electromagnet depends upon the amount of current flowing 
through the coils; and this principle was used to vary the magnetic 
strength. None of these clutches, however, were placed on the market 
as they were both expensive and complicated. Magnetic clutches, 
however, are used a great deal in machine shops to hold small parts 
on lathes, grinding machines, etc., where there is no method of 
holding the work with a mechanical clutch. One form of magnetic 
clutch, as used on the Owen magnetic car, is described on page 47. 
Both the gear box and clutch function by electricity or magnetism. 


Methods of Operation. Practically all modern clutches are 
operated by means of a special pedal moved by the left foot. The 
pedal is connected to the internal member by means of rods and levers, 


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which compresses the clutch spring or springs arid allows the clutch 
members to separate. This throws the clutch out. To throw it 
back in, remove the foot pressure from the pedal, and the springs 
again exert pressure and force the parts together. This action 
causes them to take hold. There was a time when a considerable 
number of cars had the clutch so constructed that the pedal held it 
in and the springs threw it out, just the reverse of the present plan. 
This method is no longer used, as it necessitated a constant pressure 
on the pedal while driving — a very fatiguing process. 

Gradual Clutch Release. The Dorris clutch, made by the Dorris 
Motor Car Company, St. Louis, Missouri, Fig. 259, is a new arrange- 
ment of the clutch pedal, 

and its operation is such /?- 

that the clutch is released 
or thrown out with very 
light pressure on the 
pedal. Pressure on the 
pedal A is transmitted 
by the shorter lever arm 
B, thus greatly increas- 
ing the leverage. This 
pressure is transmitted to 
lever C and through it to 
lever 2), these two being 
hung on the frame cross 
member E. As C is much 
longer than D, there is 
another multiplying ac- 
tion here. This does not 
act directly upon the 
clutdh but upon the upper 
end of the clutch shifter 
F, which is attached to the clutch at G and pivoted at its lower 
end H — here again in a multiplying action. The net result of these 
three multiplications is a combination which will release the strongest 
and stiffest clutch with a very slight pressure of the foot. 

Clutch Pedals. It has been the general practice in the past to 
have the clutch pedals separate and distinct, with the service-brake 

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Fig. 259. Multiplying Lever of Dorris Clutch to 

Make Pedal Pressure Light 

Courtesy of Dorris Motor Car Company, St. Louis, Missouri 


pedal on a concentric shaft occasionally. Now, however, the rapidly 
growing practice of simplification and elimination, combined with the 
wide use of the unit power plant, is eliminating the so-called clutch 
shaft with its bearings and fastenings to the frame, to the clutch 
operating yoke, and to many other parts. As the Cadillac illustra- 
tion, Fig. 254, shows and as the Templar unit, Fig. 260, shows even 
better, all these shafts, rods, and fastenings can be eliminated and the 
pedals and levers mounted directly on or in the power unit. In the 
Templar illustration, the foot brake has a simple rod connection from 
the ear on the pedal to the brake-operating system, while the hand 

Fig. 260. Unit Power Plant of the Templar Four 

brake has a similar connection from the extended lower end of the 
rod to the brake-operating system. In this simple way, perhaps 
40 or more pieces are eliminated and their weight saved. 

Clutch Lubrication. As has been previously pointed out, some 
clutches run in oil, while others run dry. The former type must be 
kept filled with lubricant at all times. The general plan in such a case 
is to provide a lead from the engine oiler when the clutch case is 
separated from the engine case or a connecting means when the two 
are in one case. In addition to the actual clutching members, there 
is practically always a sliding member, which must have lubricant of 
some form, while the thrust bearings to take the thrust of the clutch 


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springs must be cared for. Generally these two cases are cared for 
by a pair of grease cups, which are clearly shown in Fig. 247. 
The operating rods are lubricated usually by means of small oil holes, 
either drilled directly into the part or covered with a small oil cup. 
In those cases in which the clutch runs in oil, it will be noted that a 
filling plug is provided, by means of which additional lubricant can 
be poured into the casing, Fig. 256. 

Clutch-bearing lubrication is highly important, particularly with 
clutches like the cone which must be kept free from lubricant and the 
dry disc in which lubricant is not used. Where the clutch itself 
rims in oil, it is a simple matter to lubricate the bearings, but in 
the other cases, oil or grease must be provided from one of three 
places; from a prolongation of the engine oiling system, as shown in 
Figs. 246 and 251; from the outside — generally by means of grease 
cups — as just discussed; or from the transmission end. The last 
form is used only in unit power plants; combinations of clutch and 
transmission, as shown in Fig. 253; and in cases, Fig. 256, where 
the construction allows a grease or an oil cup attachment at the 
transmission end, the transmission itself being some distance away. 

Clutch Bearings. The need for bearings in a clutch depends 
somewhat upon its nature and location, but regardless of these a 
thrust bearing is needed for the clutch spring. To explain this 
briefly, it is known that action and reaction are equal, and opposite 
in direction. For this reason, when a clutch spring presses the discs 
or parts together with a force of, say, 100 pounds, there is exerted 
in the opposite direction this same force of 100 pounds. In order to 
have something for this to work against, a bearing is used, and since 
it takes up this spring thrust, it is called a thrust bearing. Not all 
bearings are fitted to take thrust, as the majority are designed for 
radial loads only. For this reason a special design is needed. 

When the clutch is incorporated in the flywheel, two additional 
bearings — one for the end of the crankshaft and another for the 
transmission or driven shaft — are generally needed. The bearings 
will be noted in Figs. 246 and 248, although the transmission-shaft 
bearing does not have the clutch combined with the; engine but 
rather with the transmission. In the majority of cases, it will be 
found that a means of fastening the end of one shaft has been worked 
out so as to eliminate one bearing. This accounts for the large 




number which show but two — the thrust and one other. In looking 
back over the clutches, it will be noticed also that nearly all the bear- 
ings are of the plain ball form. This is due in large part to the fact 
that the plain ball bearings take up the least room for the load carried, 
both in diameter and width — a contributing reason being the fact 
that in many cases one of the shafts or parts can be formed to take 
the place of either the inner or outer ball race. 

Clutch Adjustment. Adjusting a clutch, as a rule, is not a 
difficult task as there are but two possible sources of adjustment — the 
throw or movement of the operating pedal or lever and the tension 
of the spring. An adjustment is generally provided for each. When 
the fullest possible throw of the pedal does not disengage the clutch, 
an adjustment is required to give a greater throw. If the throw is 
correct, but the clutch takes hold too quickly and vigorously, the 
spring pressure can be lessened somewhat to soften down this action. 
Chi the other hand, when dropped in quickly, if it takes hold slowly, 
more spring pressure is needed, and it should be tightened. 

Clutch Accessibility. Clutches are made accessible in two ways: 
by their location on the car and by the relative ease with which they 
can be removed. Accessibility as to location is less in the various 
combinations, such as in the unit power plant, housed within the 
flywheel, or combined with the transmission. Ease of removal is 
determined by the number and location of the joints (usually uni- 
versal) used with the clutch. 


The very fact that the clutch is a more or less flexible, or rather, 
variable, connection between engine and road wheels makes it 
necessary that it be kept in the best of shape. It is rather surprising 
to the novice with his first clutch trouble to have his motor racing 
at the highest possible speed and to find his car barely moving, but 
to the experienced driver it is humiliating. 

Slipping Clutch. Slipping is the most common of clutch trou- 
bles. This is brought about in a cone clutch by oil, grease, or other 
slippery matter on the surface of the clutch and can often be cured 
temporarily by throwing sand, dirt, or other matter on the clutch 
surface, although this is not recommended. Many times, the 
clutch leather, or facing, becomes so glazed that it slips without any 




oil or grease on it. In that case it is desirable to roughen the surface. 
This may be done by taking the clutch out, cleaning the surface with 
kerosene and gasoline, and then roughing-up the surface with a file 
or other similar tool. 

In case it is not desired to take the clutch out, or when it is very 
inaccessible, the clutch surface may be roughened by fastening the 
clutch pedal in its extreme out position with some kind of a stick, 
cord, or wire, and then roughing the surface, as far in a£ it can be 
reached, with the end of a small saw, preferably of the keyhole type, 
as shown in Fig. 261. Before starting this repair, it is well to soak 
the leather with neat's-foot oil. This spftens the leather and makes 
the roughening task lighter. 

Many drivers make the mis- 
take of driving with the foot 
constantly on the clutch pedal. 
This wears the leather surface 
and helps it to glaze quickly. 
The constant rubbing from fre- 
quent slipping makes the leather 
hard and dry. 

When a metal-to-metal oiled 
clutch slips, the trouble usually is 
in the clutch spring, which is too 

weak to hold the plates together. To remedy slipping with this 
type, it is necessary to tighten up the clutch-spring adjustment. 

Clutch troubles are not always so obvious. In one instance, 
the clutch slipped on a new car. In the shop, the clutch spider 
seemed perfect and properly adjusted, also the spring, but to make 
sure, a new clutch was put in. Still the clutch slipped. To test it 
out still farther, the linkage was disconnected right at the clutch 
and then it held perfectly, showing that the trouble was in the link- 
age. On examination one bushing was found to be such a tight fit 
that it would not allow the pedal to move freely enough to release the 
clutch fully. When this was relieved a little, the clutch acted all right. 

Replacing Clutch Leathers. Clutches offer many chances for 
trouble. The most frequent causes are the wear of leather facings 
with the attendant loss of power, and weak springs. Weak springs 
may be cured by screwing lip on the adjusting nut or bolt provided. 




Slippery leather may also be corrected by washing first with gaso- 
line ajid then with water, finally roughing the surface with a coarse 
rasp and replacing only after the leather is thoroughly clean. Dry 
leather is fixed by soaking in water or neat's-foot oil. It should be 
replaced while still moist, and copious lubrication will keep it soft. 
The greatest problem in replacing a worn, charred, or otherwise 
defective leather lies in getting the right layout for the form of the 
new leather the first time. It must be remembered that the surface 
is a portion of a cone and, therefore, its development is not easy. 

It is attacked in this man- 
ner: Prepare the cone by 
removing the old leather 
and all rivets, cleaning out 
the rivet holes, and provid- 
ing new rivets. Measure the 
cone, taking the diameters 
at both the large and small 
ends and also the width. 
Take a large sheet of paper 
and lay off upon it a figure 
similar to ABCD, Fig. 262, 
drawn to exact scale and 
having for its dimensions 
the three measurements 
just obtained, viz, the large 
and small diameters and the 
width of the cone. This 
figure represents the projec- 
tion of the cone in a flat 
plane. Bisect the line AD 
and draw the center line EF at right angles to AD. Prolong the 
two tapered lines AB and DC until they meet the center line as at G. 
The point G represents the apex of the cone if it were complete, 
and hence any circular arc with the correct radius, drawn from this 
point as a center, will be a correct projection of the development 
of that portion of the conical surface. With GA and GB as 
radii, draw the two circular arcs HAD J and IBCK, also draw the 
radial lines HI and JK to pass through G. The enclosed figure 


Fig. 262. Diagram Showing How to Gut Clutch 


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HIBCKJDAH may then be cut out and used as a pattern from 
which to cut out clutch leathers. If the distances AH and DJ be 
made approximately equal to or slightly more than AD, the pattern 
will a little more than encircle the cone clutch. 

After the leather has been cut out, it should be prepared by 
soaking in water or oil, according as its surface is fairly soft or rather 
harsh. In either case, it must be well soaked, so as tb stretch easily. 
In. putting it on the cone, one end is cut to a diagonal, laid down on 
the cone, and riveted in place. Next, the leather is drawn down 
tightly past the next pair of rivet holes, which are then driven into 
place. This is continued until the strip is secured. The leather is 
now wetted again, for, if allowed to dry off immediately, the shrinking 
action will break it out at most of the rivet holes and render it use- 
less. By drying it out gradually, a taut condi- 
tion may be arrived at without this danger. 

Handling Clutch Springs. Clutch springs, 
like the valve springs mentioned previously, 
are mean to handle and compress. The' best 
way is to compress and hold them compressed 
until needed. For this purpose, a rig similar 
to that described for valve springs should be 
made but of stiffer stronger stock. A very 
good one can be made from two round plates, 
one small, and the other of larger diameter with ^ %&• ^$* T wSSh * 1 
a pair of L-shaped bolts through it. The „ ^* ^ Friction 

. . , , , , Courtesy of "Motor World" 

spring is placed between the two, with the 
ends of the L's looped over the smaller plate, and then, by tight- 
ening the nuts on the bolts, the spring is gradually compressed. 
An excellent device for holding clutch springs consists of a 
simple pair of metal clamps which are joined together by three or 
more short metal bars, as Fig. 263 shows. If one particular clutch 
spring is handled continuously, the length can be made to fit this 
best, otherwise it will have to be made of any convenient length. 
The inside diameter of the clamps when fully open is greater than 
the outside diameter of the spring. The clamp is set in a vise or on 
a drill press and the spring set inside of it. Then the spring is com- 
pressed by working the vise handle or by lowering the drill-press 
spindle. When compressed down to the length used in the car, the 




ends of the clamp are tightened and the spring is held by friction. 
Then the spring can be handled readily, using one of the metal bars 
as a handle. It is put into place, and then the retaining screws can 
be loosened and the clamp removed. 

Fierce Clutch. A fierce clutch is one that does not take 
hold gradually but grabs the moment the clutch pedal is released. 
In a metal-disc clutch, this is caused by roughened plate surfaces 
and insufficient lubricant, so that, instead of the plates twisting 
gradually across each other as the lubricant is squeezed out from 
between them, they catch at once and the 'car starts with a jerk. 
Chi a cone clutch, this fierceness is produced by too strong a spring, 

too large a clutching sur- 
face in combination with a 
very strong spring, or a hard 
or burned clutch surface or 

Ford Clutch Troubles. 
There are now so many 
Fords in use that the aver- 
age repair man feels justified 
in making special apparatus 
or tools to save time or 
work in Ford repairs. For 
one thing, the clutch-disc 
drum frequently needs 
removal and this is a diffi- 
cult job. By means of a simple rigging, however, consisting of a plate 
and a few bolts, it can be taken off in a few moments and with little 
trouble. It will be noted from Fig. 264 that the rigging is but a modi- 
fied form of wheel puller. It consists of a i-inch plate of steel with 
three holes drilled in it for three bolts. The two outside ones have 
T-head ends and have to be specially made, and made carefully, 
as this T-head must slip through either one of the oval holes in 
the web of the drum. When this is done, it is straightened up so 
as to stand at right angles to the drum and is thus in a position 
to press firmly against the drum from the inside. There are nuts 
on the center bolt on both sides of the plate, but the drawing shows 
only that on the outer end. When the T-bolts are in place, the 

Fig. 264. Simple Rigging for Removing Ford 
Clutch Disc 


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center bolt, which is slightly pointed and preferably hardened on 
the end, is screwed down so as to come into contact with the end 
of the clutch shaft. After tightening the center bolt, the T-head 
bolts are tightened until they pull the drum off the shaft. 

Clutch Spinning. A trouble which is bothersome but not 
dangerous is clutch spinning. This is the name applied to the 
action of the male clutch member when it continues to rotate, or 
spin, after the clutch spring pressure has been released. With the 
male member connected up to the principal transmission shaft and 
gear, as is often the case, these members continue to rotate with it. 
This gives trouble mainly in gear shifting, for the member which is 
out of engagement is considered to be at rest or rapidly approaching 
that condition. When at rest, it is an easy matter to mesh another 
gear with this one; but when this one is rotating or spinning, it is 
not so easy, particularly for the novice. 


Fig. 265. Simple Device for Inserting Corks in Clutches 

Clutch spinning may be caused (1) by a defect in the design, 
in which case little can be done with it; (2) by a defect in construc- 
tion, as in balancing, for instance, which can be corrected; or (3) 
it may be due to external causes, as, for instance, in a bearing which 
has seized, owing to a lack of lubricant, etc. 

In any case, the best and quickest remedy is a form of clutch 
spinning brake. This may consist simply of a small pad of leather 
or of metal covered with leather so located on the frame members 
that the male drum touches against it when fully released. Or it 
may be something more elaborate as to size or construction or both. 
Chi many modern cars, in fact on practically all good cars, some form 
of clutch spinning brake is fitted. Thus, the Hele-Shaw design pro- 
vides at the left end, Fig. 256, a metal cone of small diameter, while 
Fig. 255 shows flat concentric discs 19 of the Locomobile clutch. 

Cork Inserts. When cork inserts are used in a clutch, the 
insertion of nfew corks is not an easy job. A cork is a difficult and 
unhandy thing to work with, and above all to hold straight and true 


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while applying longitudinal force to it. By making up a special 
tool with a tubular member having an inner taper, into which the 
corks are forced by means of a special plunger which forms the other 
part of the tool, this is simplified considerably. This tool is shown 
in Fig. 265, with such dimensions as would be needed for a f-inch 
cork. It is advisable to make the small end of the tube f inch smaller 
than the cork, as this amount provides the proper compression. 
After being soaked in water for 10 or 15 minutes, the cork is dropped 
into the large end of the tube, and, with the small end in place 

against the cork opening in the 
clutch, a single stroke of the plunger 
will force the cork through the tool, 
incidentally compressing it into the 
hole in the clutch. With a few 
handlings any clever mechanic can 
soon become expert in the use of 
this tool. 

A more elaborate device, but 
one which works more quickly where 
there is a great deal of this work, is 
shown in Fig. 266. This is not an 
expensive machine — the original of 
this sketch was home made. The 
framework is made of standard pipe 
fittings, the spring is a valve spring, 
and the rods are cold rolled steel. 
Only a few pieces such as the working 
member C were specially made. The 
working member is made with a slot 
at A into which the corks are inserted. 
When the pedal attached to the rod D is pressed, it brings the rod 
down and forces out the cork at B. At point B, the clutch resting 
on the anvil E is held ready. The stop limits the downward move- 
ment, so a strong stroke of the foot will just push the cork into the 
hole flush and no more. The lower end of the working member is 
made with a taper so as to compress the corks about § inch, as men- 
tioned before. They should be soaked in water just the same as 
when using the hand tool. 

Kg. 266. 

Machine for Handling Cork 
Inserts Quickly 
Courtesy of "Motor World" 


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In Fig. 267, several other common clutch troubles and their 
remedies are suggested; the parts shown in the illustration, however, 
are in excellent condition, in fact, new. 

When the right kind of clutch discs for a multiple-disc form are 
not on hand, new discs can be cut from leather to answer the purpose 
by means of the gasket cutter, shown in Fig. 268. This cutter con- 
sists of a pair of steel L-shaped arms, preferably forged, with points 
sharpened enough to cut the leather or the gasket materials The 
clamp has a point for the center of the circle on its under side, while 




Fig. 267. Clutch Troubles Illustrated 

the actual clamping is done by the bolt or screw with wing head. 
To use for clutch discs, set the inner, or shorter, member to the radius 
of the inside of the outer discs and the outer, or longer, arm to the 
radius of the outside of the inner discs. By pressing down hard on 
the arms and rotating them at the same time, an annular ring will 
be cut out which will fit exactly. One hand should be held on or 
near the center, while the other hand supplies the pressure and 
rotating motion on the cutting ends. It should not be expected that 
the points will cut through in one revolution; on the contrary, the 
first time around will just mark out the section and it will need from 


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6 to 10 revolutions, with heavy pressure, to cut a leather disc. In 
time, the workman will become skilled in the use of this cutter and 

Fig. 268. Method of Cutting Facing for Disc Clutches in an Emergency 
Courtesy of "Motor World'* 

have a knowledge of its limits, as well as of the method of keeping it 
in good cutting order. 

Adjusting Clutch Pedals. Some cars are made with adjustable 
clutch pedals so the long- or short-legged driver can set the length of 
these to suit, but when no adjustment is provided and it is desired 
to change the length, some figuring must be done. To shorten a 
non-adjustable pedal, the best way is to take it out of the car and 

bend it somewhat on the order 

of the dotted lines in Fig. 269. 

The idea is to make the same 

amount of metal take a 

roundabout and longer path. 

In doing this, the workman 

must be governed largely by 

what the floor boards and the 

other parts of the mechanism 

in the immediate vicinity will 

allow. The bend must be 

made so as to allow the pedal 

to work in the same slot. If 

necessary, cut the slot a 

little longer, but first consider the result before bending the pedal. 

On the other hand, when the pedal is too short, the pad can be 

removed from where it is bolted on at A and a pair of steel strips 

cut so as to fit into the two sides of the pedal shank and brought 

Fig. 269. Schemes for Shortening or Lengthening 
Clutch Pedals to Fit Driver 


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together at the other end. These are bolted in at A, where the pad 
was formerly, and the pad moved out to the new end at B. In some 
such cases, where the sides of the pedal shank offer no groove to help 
hold the steel strips, it is necessary to put another bolt through them, 
as at C, to prevent the whole addition swinging about A as a center. 

Clutch Troubles Outside of Clutch. Frequently, there is trouble 
in the clutch when the basic reason for it is outside of the clutch 
entirely. Thus, failure of a clutch to engage or disengage properly 
is often the fault of the connecting rods and levers; wear in the clutch 
collar or in other parts; or the emergency-brake interlock may have 
been fitted so close that as soon as the rods are shortened once or 
twice to compensate for wear, it stands in such a position as to throw 
the clutch out slightly although the latter appears to be fully engaged. 

Another clutch trouble outside of the clutch is apparent slipping 
at corners, especially at turns on grades. On a turn — the road being 
cambered — the frame is distorted, especially with the combination of 
curve and grade. This may be sufficient to throw the clutch and 
driving shaft out of alignment just enough so the clutch face will not 
make full contact. This is most noticeable on cars with a single 
universal joint, in which case the distortion of the frame has more 
effect on the driving shaft. Similarly, a car with an unusually light 
or flexible frame will show this trouble very often, as the combination 
of curve and grade is too much for the light frame. 

Summary of Clutch Troubles 

Throwing in Clutch. Do not throw clutch in suddenly and cause 
rear wheels to spin. Such action is destructive to tires and throws 
great stress on the entire mechanism of the car. 

Lubricating Multiple-Disc Clutches. These are best lubricated 
by injecting oil into the opening for that purpose by means of an oil 
gun. A very light lubricating oil should be used. 

Multiple-Disc Clutches Failing to Hold. Inject three or four 
gunfuls of kerosene into the clutch housing and rim the engine a 
little, thereby washing out the plates of the clutch. This will cut 
the gum caused by the oil. If, after this treatment, the clutch 
squeaks or takes hold too suddenly, lubricating oil may be added. 

Loss of Power. This is noticeable in changing from intermediate 
to high gear, in climbing hills, or in running through muddy or sandy 


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roads. The trouble is of ten the result of the clutch slipping. The 
remedy is to clean the clutch with gasoline and, if the clutch is leather- 
faced, to apply castor oil after cleaning. Castor oil should never be 
used on the multiple-disc clutch. 

Failure of Clutch to Take Hold. This may be owing to a broken 
or weakened clutch spring, the clutch leather may be damaged, 
clutch shaft may be out of line or bent, leather may be gummed, 
or bearing may be seizing. 


Primarily, the clutch is used to allow the use of change-speed 
gearing; or, stated in the reverse way, the form of the transmission 
determines whether a clutch must be used or not, there being cases in 
which it is not used. Thus, where the frictional form of transmission 
is used, no clutch is necessary; the frictional discs act as a clutch 
and render another one superfluous. With the form of transmission 
known as the planetary gear, used in the Ford car exclusively, a 
clutch is used for high speed only. 

On the other hand, the reverse of this does not always hold. Any 
form of clutch may be used with the various other forms of transmis- 
sion, as the sliding gear; in fact, in actual practice every known kind 
of a clutch will be found coupled with the sliding-gear transmission. 

Classification. Broadly considered, there are five classes of 
transmissions used. In cases where the use of any one of these 
forms eliminates the final drive, this from its very nature does not 
alter the facts but simply calls for a different and more detailed 
treatment. The four classes are: 

.^ ™,. [Operated in various ways 

\but usually selective 

(2) Individual clutch 

(3) Planetary, or epicyclic 

(4) Electric 

The features of the 1920 transmissions which stand out from 
previous years are: reduced sizes; simpler, lighter construction; 
greater compactness and greater accessibility. Perhaps the most 
noticeable trend has been toward the unit power plant which has 
helped materially to make transmissions smaller, lighter in weight, 
and more simple, with unusual compactness. This very compact- 


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ness has brought with it a stiffness which has rendered less repairs 
and adjustments necessary, despite lighter weight. The smaller sizes 
have brought about the simplification and lighter weight, and in 
turn have been produced in answer to the popular demand for lighter 
weight cars. In, part, simplification has been produced by unit 
power plants, now so popular. 


General Method of Operation. Qf the different types of sliding 
gears, the first two subdivisions are not very closely marked, but 
blend somewhat into one another. The only real difference between 
them is the method of operation, the names serving to indicate the 
distinctive characteristics. Thus, in a selective gearset, it is possible 
to "select" any one speed and change directly into it without going 
through any other. So, top, in the progressive form of transmission, 
the act of changing gears is a "progressive" one, from the lowest up 
to the highest, and vice ver&a. 

Selective Type. With the selective method of changing gears, 
it is possible to make the change at once from any particular gear 
to the desired gear without passing through any other. Of course, 
the car will not start On the high gear any more than in the other 
case, but shifting into low for starting purposes is but a single action, 
accomplished quicker than it can be told. So, too; When the car has 
been started, it can be allowed to attain quite a fair speed and the 
change to high made at once without going through the intermediate 

Progressive Type. Progressive gears, which are now little used, 
operate progressively: from first* or low, to second and from second 
to third, or high; in slowing down, from third to second to first 
and in this way only. This leads to a number of troublesome 
occurrences; thus, in stopping, it is necessary to gear down through 
all the higher speeds into low. If this is not done, when it is next 
desired to start the car, it will be necessary to start the engine, throw 
in the clutch, drop from the gear in mesh to the next lower, from that 
to the next, and ^o on down to low, throwing the clutch out and in 
for each change of speed. When first is reached, the car may be 
started. After starting, it is then necessary, in order to obtain any 
measurable speed with the car, to change back up the list, from low 


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to second, from second to third, and so forth. In this way the pro- 
gressive gear is disadvantageous, since its use means much gear 
shifting; but, on the other hand, the shifting is very easy for the 
novice to learn, as it is a continuous process, all in one direction. 
Modern Selective Types. To present some modern selective 
types of gear boxes and point out their various differences, advan- 
tages, and disadvantages, refer to Fig. 270. This type shows the 
three-speed selective gear used on the Cadillac cars, which is but 
slightly modified from the type which has been used by this concern 
for three years. This change should be noted, however; the lay- 

Fig. 270. Cadillac Transmission and Housing 

shaft, which formerly was on the same horizontal level as the main 
shaft, is now placed directly below it. This makes a higher but 
narrower gear box, that is, instead of being wide and fairly flat, it 
is now high and narrow. The placing of the shifting levers on the 
cover, directly over the center, has aided in making the gearset more 
compact than formerly. In it there are two shifting gears, one gear 
carrying a set of dogs cut into its face, which mesh with a similar set 
on the main driving gear to give the direct drive. The gear portion 
of this member meshes with another gear for second. The second 
shifting member meshes with one gear on the layshaft for low speed 


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and with another on the third shaft for reverse. The reverse gear 
is at all times in mesh with the fourth layshaft gear, so that on 
reverse the drive is through five gears instead of four. On high gear 
the drive is through the dogs, the layshaft being driven, of course, 
but silently, as k transmits no power. 

Four-Speed Type with Direct Drive on High. One of the tend- 
encies of recent years has been the gradual change toward more 
speeds, as shown by the increasing use of four-speed gear boxes. 

Fig. 271. Sectional Plan Drawing of the Locomobile Four-Speed Transmission 
Courtesy of Locomobile Company of America, Bridgeport, Connecticut 

Other indications of this change have been the two-speed axle, which 
gave double the number of gear-box speeds, with the ordinary three- 
speed and reverse transmission; and the electric transmission, which 
affords seven forward and two reverse speeds. 

Following this increase of speeds, the multi-cylinder motors and 
downward price revisions of the early part of 1916 brought about a 
combination which almost eliminated the four-speed gear box or at 
least removed it from aJl but the most expensive of cars and from 




many of those. It is claimed that the eight- and twelve-cylinder 
motors have so much power and flexibility that a fourth speed is 
rendered unnecessary. The four-speed gear box is more expensive 
than the three-speed box, and the lowered prices of cars have been 
instrumental in preventing its continued use. At the same time, 
there was considerable lightening of weight all over the chassis, and 
the four-speed gear box had to go out of all but the biggest cars on 
account of its greater weight. 

Fig. 271 is a sectional plan of one of the few four-speed gear 
boxes left. In this drawing it will be noted that the two-gear shafts, 
as well as the operating shafts, lie in the same horizontal plane. The 
halftone reproduction of the photograph of this drawing, Fig. 272, 

fig. 2/2. jrnoiograpnic xveproaucuou 01 uocomoDue uearoox suowu 
in Section in Fig. 271 

shows the location of the shafts even more plainly and will, perhaps, 
be of more use to the average reader. Both forms show the arms 
which project up to attach this unit to the frame. The cover, which 
is a light easily removed aluminum member, is taken off from above 
after the floor boards are lifted out. This arrangement makes for acces- 
sibility and eliminates any need for lying on the ground while working 
on the transmission gears or shafts, should such work be necessary. 
The form of final drive alters the construction of the trans- 
mission very materially. Formerly, when all final drives were of the 
double-chain form, it was customary to include the differential, 
bevel gears, and driving shafts in the gear box. Now that the chain 
has gone out, this construction is found only when the gear box is a 
unit with the rear axle. 


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Four-Speed Type with Direct Drive on Third. In all the trans- 
missions shown and described thus far, the direct drive has been 
the highest speed. By referring back to Fig. 253, which shows the 
Winton four-speed gear box, as well as the clutch, a point of difference 
will be seen. This has the direct drive on third speed, fourth being a 
geared-up speed for use only in emergencies, when the very highest 
rate of travel is required, and when a little noise more or less would 
make no difference. This arrangement of the direct drive and silent 
speed has long been a debated point, some designers favoring the 
direct-drive type with an over-geared speed for occasional use, while 
the opponents of this method say that this construction practically 
reduces the transmission to a three-speed basis, the fourth being so 
seldom used that it is practically negligible. They say, also, that the 
modern motor can attain a high enough speed, on the one hand, and is 
flexible enough, on the other, to permit its being used with the high- 
gear direct drive upon almost all occasions. 

Transmission Location. There are but four recognized positions 
for the transmission in the modern car. These are: (1) unit with the 
engine (unit power plant), (2) amidships in unit with clutch or alone 
in a forward position, (3) amidships in unit with forward end driving 
shaft or in a rear position, and (4) at the rear in unit with rear axle. 
Unit with Engine. The unit with the engine type is illustrated in 
an excellent manner in Fig. 273, which shows the eight-cylinder 
Northway motor, cone clutch, and three-speed transmission. Some 
idea of the compactness of this outfit, which is shown exactly as used on 
the Oakland car, can be gained from comparison with cylinder bore 
and crankshaft size, the motor being 3J by 4£ inches. The notice- 
able features of the transmission, aside from its compactness, are the 
use of double row ball bearings on the splined main shaft, with a 
Hyatt roller form for the spigot bearing (free end of main shaft) and 
very long plain bronze bushing for the countershaft unit, the latter 
being made as a single piece rotating on a single bearing around a 
straight fixed shaft. The countershaft, or layshaft, as it is some- 
times called, is placed below the main shaft. 

Another example of the unit with engine type is seen in the 
Grant-Lee three-speed gear box, Fig. 274, as utilized in the Hackett 
car. This is unusually small and compact, as will be noted by com- 
paring the size of the unit with the operating levers and pedal. While 


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the clutch is not shown, its housing is, also the flange which attaches 
it to the flywheel housing to complete the power unit. A third 
example of the engine-unit power group is shown in Fig. 275, which 
shows the flywheel, clutch, and transmission of the Peerless eight. 
This unit transmits many times the power of the Hackett unit and 
is therefore much larger. In this unit the bearing arrangement is 
rather unusual, as roller 
bearings of the taper form 
are used on the main shaft, 
a straight roller for the 
spigot bearing, and plain 
ball bearings for the lay- 
shaft. The shortness and 
large diameter of the 
shafts should be noted. 

Additional transmis- 
sions in a unit with clutch 
and motor will be seen 
under Clutches, in Figs. 
251, 252, and 254. 

Amidships Alone or 
with Clutch. The amid- 
ships unit joined with the 
clutch, shown in Fig. 253, 
represents the Winton 
transmission and clutch. 
This is not a common con- 
struction on pleasure cars, 
although it is used on 
quite a number of trucks. 
On the amidships-clutch 
unit type, however, the 
combination is not quite so 
intimate as the one in which the two units are enclosed in a common case. 

Amidships Joined with Driving Shaft The amidships unit 
joined with the forward end of the driving shaft is well shown by the 
Locomobile, Figs. 271 and 272. The universal joint with the driving- 
shaft pivots is seen at the left side of both these views. In this 

Fig. 274. Gear Box Used in Hackett Care Is Very 

Small and Compact 

Courtesy of Hackett Motor Car Company, 

Jackson, Michigan 


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construction, which is more widely used than the other amidships 
arrangement, there is usually a frame cross-member at the point on 
which the rear end of the transmission is supported. This same 
arrangement is used on the Stearns-Knight four-cylinder chassis, the 
transmission of which is shown in Fig. 276. In this transmission 
the stiffness of the cross-member at the rear end of the transmission 
is also utilized to support the brake drum of the foot-brake system. 

Fig. 275. Gear Box and Clutch of Peerless Eight 
Courtesy of Peerless Motor Car Company, Cleveland 

The short stiff shafts on the transmission will be noted, also the many 
splines on the main shaft and the use of double row ball bearings on 
the main shaft, with a flexible roller on the spigot, and the same type 
of bearings on either end of the layshaft, which is alongside of the main 
shaft. Note also the means provided for adjusting the countershaft 
longitudinally by the two steel screws projecting through the bear- 
ing caps so that this adjustment can be made from the outside. 

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Unit with Rear Axle. The position at the rear axle is not so 
widely used as a few years ago. The Stutz car has a typical rear-unit 
construction, it being about the only car using this equipment. 
The Studebaker makers used this construction for a number of years, 
but they are now mounting the transmission amidships. Fig. 277 
is a shadow drawing of the Stutz rear axle and transmission showing 
all the parts of the transmission, the ring-gear connection and the 
brake shoes. There are two brake shoes: one for the service brake; 

Fig. 276. Three-Speed Transmission and Brake of Stearns Four-Cylinder Car 
Courtesy of F. B. Stearns Company, Cleveland, Ohio 

the other for the emergency brake. As will be noted, this position 
of the transmission calls for two operating rods, each the full length 
from the operating levers to the rear axle. 

The connections of the levers and the shifting of the gears are 
plainly shown in the Studebaker transmission, Fig. 278. 

In this illustration, the gear-shifting lever is placed in the center 
and is shown solid in the neutral position and lighter in the other 
four positions. 



Just below these levers, the transmission is shown with the position 
of the gears for neutral. The high and intermediate sliding gear is 
between the countershaft gear and the intermediate gear, and the 
low and reverse sliding gear is between the low-speed countershaft 
gear and the reverse countershaft gear. The four corners show 
the positions of the gears when the lever is in each one of the positions 
as shown. 

These positions plainly indicate that there is a driving gear 
and two slide members on the main shaft and four gears on the 
countershaft. At the left in the picture, the gear toward the rear 

Fig. 277. Stuts, 1920 Transmission Mounted in a Unit with the Rear Axle 

is for reverse. An idling gear (not shown) is needed to complete 
the reversal of the motion. When the lever is swung to the left 
and forward, this group is completed and then the speed is 

At the time when the shifting lever is swung to the left 
and backward, the rear sliding member is moved forward to mesh 
with the second gear on the countershaft as is shown in the 
diagram (see Fig. 278) at the lower left-hand corner, and first, 
or low, speed results. With this gear in neutral position — as it is 
left when the shifting lever is swung through the neutral position 


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and over to the right — a further movement to the front picks up the 
forward sliding gear and moves it back into mesh with the third gear 
on the lay shaft; this combination, as shown in the upper right-hand 
corner, gives second speed. When the lever is moved back, it moves 

Fig. 278. Diagrams Showing Working of Studebaker Transmission 

the gear forward, giving high speed and direct drive, as shown at the 
lower right-hand corner. 

Interlocking Devices. Nearly all transmissions have a form of 
stop lock on the shifting rods in the transmission, which holds the 
gears in mesh as soon as they have been moved by the operator 
until he moves them again. In reality this arrangement simply 
prevents the gears from jumping out of mesh. Generally, the most 
simple arrangement which will hold the gears is used. In the ordinary 


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form this arrangement consists of hardened steel wedges with light 
springs back of them and deep grooves in the shifting rods into which 
these wedges fit. 

In Figs. 271 and 272, the notches in the shifting rods can be 
seen plainly. In Fig. 275, the bolt head A indicates the location 
of one of the shifting locks. In Fig. 277 notches are placed on the low 

Fig. 279. Various Forms of Transmission Interlocks 

and reverse rod and those on the second and high-speed shifting 
rod to be used as the shifting locks. 

Not all transmissions have the wedge and notch, as Fig. 279 
indicates. This figure shows: at A, a method of interlocking by 
means of a pin at the shifting forks (not rods) which project into 
shallow holes in the two shifters; at B, a rocking, or tilting, bar 
beneath the shifting forks, which is pressed into a notch in either 
fork when moved from neutral; and at C, the use of a steel ball — all 
three arrangements being used by the American Die and Tool 
Company. The form at D shows the pin used by Grant-Lee Gear 


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Company, the grooves in the rods being deep enough to accommodate 
this form in a neutral position so that the rod can be started. But the 
guide hole in the central housing in which the pin is moved across by 
the motion of one rod, owing to the shape of the bottom of the groove, 
prevents the other rod from moving. 

Electrically Operated Gears. In substance, the electrically 
operated transmission has all the hand levers, rods, and other levers 
replaced by a series of push buttons. When it is desired to change 
speeds, even before the actual change is necessary, the driver presses 
the button marked for the speed he thinks he will require. Then, 
when the actual need becomes apparent, he throws out the clutch 
and immediately drops it back again, all this forming but a single 
forward and back movement of the 
foot. During the slight interval while 
the clutch is out, the electrical connec- 
tions shift the gears automatically, so 
that when the clutch is let back, the 
gears are meshed ready to drive. 

Principle of Action. To explain 
this action briefly, the gears are moved 
by means of solenoid magnets, which 
are nothing more than coils of wire, 
through which an electric current from 
a convenient battery is allowed to pass. 
Through the center of each one of these 
coils passes an iron bar. When a cur- 
rent passes through the coil, it is con- 
verted into an electromagnet and draws the iron bar inward. As the 
other end of the bar is connected to the gear to be shifted, this move- 
ment of the bar shifts the gear. Consequently, when the button is 
pressed so that current flows through one of the coils, that action 
shifts the gear for which the button is marked. 

By referring to Fig. 280, this action will be made more clear. 
The diagram shows but one pair of gears to be meshed, and the 
battery, push button S, coil D, iron bar P, and clutch connection 
M are all shown as simply as possible. When button S is pressed, 
current through the coil D will draw the bar P and mesh the 
gears as soon as the clutch has been thrown out, thereby closing 

Fig. 280. Sketch Showing How a 

Solenoid Moves a Gear When 

Current Flows 


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the circuit at M. The application of this to an actual transmission 
is shown more in detail in Fig. 281, which shows the clutch pedal 

Fig. 281. Arrangement of the Solenoids and Pedal in the OH Electric Gear Shift 

and its connection to the six solenoids necessary to produce four 
forward speeds, one reverse speed, and a neutral point. 

On the steering wheel, Fig. 282, the control group of six buttons 
will be noted on the small round plate at the center, with the addition 
of the horn button in the center. In Fig. 283 is another arrangement. 

In the 1916 forms of electric-control systems, the buttons are 
grouped in one instance on the top of a small box four or five inches 

Fig. 282. Arrangement of Buttons 
for Gear Shifting 

Fig. 283. Another Arrangement of Buttons 
for Gear Shifting 

square, which is placed on the steering post below the wheel; in 
another, on the dash; and in a third, on a rod connecting post and dash. 


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Pneumatic Shifting System. The pneumatic system of gear 
shifting is along lines somewhat similar to the electric system, air 
under pressure being used to move the gears instead of a hand lever 
and rod combination. For this purpose it is necessary to add an 
air compressor, a tank to carry the compressed air, and what is 
called the "shift" — really a complicated valve and a series of plungers 
— to the car. The valve and plungers respond to a finger lever on the 
steering wheel, the same as the electric system responds to the but- 
tons. Air is admitted behind the plungers, which moves the gears 
as soon as the clutch is depressed. It is seen, therefore, that this 
system, like the electric shifter, permits the anticipation of the needs 
of the car. 

Railway Car Needs. All transmissions previously presented 
have had but one reverse. For gasoline railway cars, the inability 
to turn the car requires as many reverse speeds as forward which 
means special gearing. Usually, this gearing is accomplished by 
means of a pair of bevels, each with a clutch, meshing with a single 
driving bevel. Obviously the two driven bevels will turn in different 
directions, and each will drive when its clutch is engaged. 

Transmission Operation. As has been pointed out previously, 
practically all transmissions operate all gears by means of a long hand 
lever, placed either at the side of the car or in the center, according 
to the location of the control. Even on planetary forms, still to be 
described, at least one of the various speeds is controlled by a hand 
lever. The electric- and air-shifting methods have made a start, and 
a good one, but until their number increases materially, these types 
can be considered as only having started their development. 

Transmission Lubrication. A fairly heavy lubricant is gener- 
ally recommended for gear-box use — either a special form of about the 
right consistency, or else a home-made mixture of about half-and- 
half of light oil and hard grease. Some firms recommend a graphite 
grease. The lower part of the case should be filled to a point, or 
level, where the largest gears dip continuously. This will insure a 
constant agitation of the lubricant, which will thus get to all moving 
parts and surfaces. Having the lubricant too stiff is bad, because then 
the gears simply cut a path through it without moving the rest. 
This results in all other parts running practically dry. Too thin a 
lubricant or too much of it will make a fairly heavy drag on the motor, 


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which loss of power should be avoided. Gear-box lubricant generally 
is introduced in bulk by the removal of the cover, usually of a large size 
to allow of this. The outside parts carry their own grease and on cups. 

Transmission Bearings. By looking back at the various trans- 
missions shown, it will be noted that ball bearings are used most 
freely. Roller bearings in various forms are coming into use, as the 
shorter series produced in the last couple of years has shown 
designers that this type would produce a compact gear box, their size 
having previously limited their use. Plain bearings are not used at 
all on good cars. 

Transmission Adjustments. Few adjustments are needed in 
"the modern gear box. However, provision for wear is made in the 
operating rods and levers, both within the case and without. In 
some cases the shafts may be slightly shifted endwise to secure 
better meshing of the gears after wear. Bearings, too, are arranged 
to shift slightly in an endwise direction to take care of wear in other 
parts and not so much in the bearings themselves. 


Method of Action. The planetary, or epicyclic, form of gear- 
ing offers many advantages, but, strange to say, the American 
people, although inclined toward simplicity and cheapness in com- 
bination, will not have it in this form, and, as a consequence, this 
excellent gear-reducing means is fast losing favor. The principle 
upon which all planetaries work is as follows: Connected to the 
engine is the first gear of the train. The second is one of a series of 
several gears; these are pivoted in a drum, which may be held station- 
ary by a brake band. The middle, or third, gear in the train, as well 
as the last, or fourth, is connected to another gear, a driven gear, not a 
driver. Considering but a single rotating train — there usually are 
three or more — the last-named gears form the fifth and sixth in the 
whole train. Gears two, three, and four have different numbers of 
teeth, as well as gears one, five, and six. Holding the band which 
holds the drum to which the gears are pivoted, allows each of them 
to rotate around its own axis, but not around the main shaft. This 
form of rotation gives one gear reduction. 

Another band holds another gear stationary and allows the 
three-gear unit to rotate around the main shaft as an axis; at the 


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same time it leaves them free to also rotate around their own axis. 
This produces another gear reduction. Another form which is 
popular in so far as planetary gears are popular is that in which 
internal gears are substituted for one set of the planets, from which 
the device obtained its name. This does not complicate the device 
any; in fact, the only way in which it makes any change is in the 

Fig. 287. Drawing Showing Ford Planetary Transmission 

manufacturing cost of the gear, internals costing more than spur 

Ford Planetary Type. Ford has been a consistent user of the 
planetary gear; in fact, the simplicity and ease of operation of his 
well-known and widely used car is largely due to this use. The Ford 
transmission, which is of the all-spur-gear type, is shown in Fig. 287. 
This is operated by means of two pedals and a lever, one pedal 
working high and low speeds, while the other pedal controls the 
reverse. The first-named pedal, however, must be used in conjunc- 
tion with the forward movement of the hand lever which locks the 
high-speed clutch, seen in this figure at the right. 


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Freak Drives. What are termed the freak drives attract much 
attention from inventors, but little from hard-headed constructors. 
Thus, the belt drive was once advanced as the simple drive, yet it 
made no progress. Today there are few belt drives used in final 
driving in America, although a few are still made in Europe. There 
is a low-price French car, Fouillaron, with this drive; and a single- 
cylinder Italian car, the Otav, selling for the equivalent of $150, 
which is also equipped with a belt drive. 

Cable and Rope Drives. When cycle cars were first brought 
out and by many considered as destined to replace both the low- 
priced cars, on account of their still lower price and simplicity; and 
motorcycles, because of their greater comfort, superior appearance, 
and greater carrying capacity, many of the simple drives were 
revived and applied to the cycle cars. The types used include the 
cable drive, which attracted much attention at one time in the motor- 
buggy field, the rope drive, the flat belt, the V-belt, the cloth-covered 
chain, and many others. With the collapse of the cycle-car boom, 
these went out of use. 

- Hydraulic Gear. Janney-Williams. The hydraulic transmis- 
sion has been advanced as a cure for all automobile troubles, rep- 
resenting as it does the elimination of clutch, differential, and the 
driving mechanism. It consists of a pump to circulate the fluid, and 
one or two motors usually attached to the rear wheels and propelled 
by the fluid. 


To speak of an electric transmission perhaps sounds peculiar, 
yet that is what should be used for a final drive through the medium 
of electric motors. This form, spoken of abroad as the petrol-electric 
car, is attaining much headway there. It gains slowly, it is true, 
but, nevertheless, surely — each year seeing one or more makes 
added to the already long list of successful cars in this category. 

In the petrol-electric cars, the generator is coupled to the engine 
in the place ordinarily occupied by the flywheel and clutch, and the 
armature acts as a flywheel. Then the two motors are set on each 
side, directly in front of the rear wheels, which they drive through 
the medium of spur gears; the whole is enclosed to keep out dirt, 
keep in oil, and reduce noise to a minimum. 


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In fact, it might be said that the electric drive possesses so many 
advantages which are worth having, even at a sacrifice, and so few 
disadvantages that one is safe in figuring that a few more years 
will see the number of these drives doubled and possibly trebled. 

Electric Transmissions. While the drives just discussed might 
be called electric drives and still be precise, the Owen magnetic car, 
which is constructed by the Baker, Rauch and Lang Company, 
makes use of an actual electric transmission, the Entz, at one time 
used in a Columbia chassis. This is so arranged that all speed 
changing is done by a small finger lever on the steering wheel, similar 
to the ordinary spark and throttle levers. The wiring formerly gave 

Fig. 289. Drawing Showing Section through Owen Magnetic Transmission 

seven speeds forward and two reverse, but a later construction will 
probably give about twice this number. 

As is shown in Fig. 289, this consists of an electric generator, the 
field magnet of which is connected to the engine crankshaft and takes 
the place of the flywheel, the armature being connected with the 
driving shaft. This transmits the turning effort of the engine by 
means of the current established in its circuit, due to the speed 
difference of its members on what constitutes the high speed. Any 
effort exerted by the engine on one member is transmitted, prac- 
tically without loss, to the other member, or armature. The clutch- 
generator member makes a very elastic clutching and transmitting 
means, but cannot transmit more than the full torque of the engine. 





For higher torque, use is made of an electric motor, whose 
armature is mounted on the driving shaft and receives current from 
the first, or clutch, generator. 

In the figure, the clutch generator is shown at the left, its field 
part marked FR, the field winding FW, and the pole pieces PP. 
This portion rotates whenever the crankshaft revolves. Within it is 
the armature A secured to the continuous shaft S, which is con- 
nected through the joint X with the driving shaft to the rear axle. 

The second part of the complete system is shown at the right 
and is practically a duplicate of the clutch generator. Its armature 
A\ is carried on the same shaft S as armature A. Outside this is 
the usual field part with rings FR, windings FW, pole pieces, and 
brushes B. 

Field FR can revolve without any motion of A; in fact, it is by 
varying the relative speed of FR and A that the different speeds are 

Fig. 290. Sketch to Explain Working of Magnetic Transmission 
Courtesy of Baker-R & L Company, Cleveland, Ohio 

obtained. For instance, on direct drive the generator is short- 
circuited on itself and carries armature A with it. Then, except for 
a slippage of 4 per cent or less, between the field FR and the arma- 
ture A, the wheels would be driven as fast as the latter rotated. 
Lower speeds are produced by making the slippage greater. Speed 
changing, as well as starting and braking, are accomplished by means 
of the finger lever on the steering wheel. The storage battery is 
charged at a 10-ampere rate. 

Perhaps the explanation which follows will give a better idea 
to the repair man than the foregoing, which is slightly technical. 
The rotating field of the generator, marked FW, is comparable to 
a horseshoe-shaped magnet B, Fig. 290, also rotated by the engine. 
The armature A at the left-hand, or engine, end of the shaft is com- 


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parable to the piece of steel C, which is free to rotate and which will 
do so when the field rotates and attracts it. If this were connected 
directly to the driving shaft, as Fig. 290 shows the combination 

Fig. 291. Second Step in the Magnetic Transmission Explanation 

would become a simple electromagnetic clutch and the car would have 
but one speed. On the level, one speed would be satisfactory, but 
in deep sand, on a heavy grade, or for any other severe pull, the air 
space between the rotating field and the armature would bring about 
the stalling of the engine. 

If we add a conventional 
electric motor just back of 
C, with its field fixed, or 
stationary, as at D, and its 
armature free to rotate with 
the armature shaft to which 
it is attached, about as shown 
in Fig. 291, C will not rotate 
as fast as B when meeting a 
stiff pull, although it will try 
to do so. A wire connects 
the commutator of C with 
the field coils D, and the 
electricity generated by the 
rotation of B relative to C, that is, the amount of slippage due to the 
air gap, is led through this wire to D where it acts as power, rotating 
E faster and thus acting as a booster on the propeller shaft. 

Fig. 292. Steering Wheel Quadrant of 
Owen Magnetic Car 


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By introducing variable resistance in the connecting wire, or 
rather series of wires, the speed may be varied from zero to the 
maximum, which, as it happens through this booster action, is 
considerably in excess of what it would be if the motor were driving 
directly through on high speed without any electrical or mechanical 
apparatus. The variety of speeds can be anything desired, and this 
forms the basis for naming it "The car of a thousand speeds ,, . As 
a matter of fact only seven speeds are provided for on the steering 
wheel, which is shown in Fig. 292, but it is perfectly feasible to 
wire up the car and arrange the quadrant to have twice this number 
or any other number, as required. On the steering post quadrant, 
the additional positions of charging, starting, and neutral are to 
be noted. The neutral position is that in which the engine is idling 
and the car standing still; or when the car is coming down a grade, 
the wheels are driving the motor which generates current in the reverse 
direction, so that the device becomes an electric brake, slowly but 
surely reducing the speed of the car. The starting position connects 
the storage battery to the generator armature in order to revolve 
the engine shaft and thus start it. The charging position can be 
used at any time to generate electricity for the storage battery. 

While this description sounds very different, the chassis is not 
unlike the average gasoline chassis with a mechanical gear shift, 
as Fig. 293, showing a view of it from above, brings out. The small 
unit just back of the motor is a mechanical reverse gear which it 
has been found advisable to use for one reason, because it gives 
all the quadrant speeds on the reverse, instead of the usual one. 
By this arrangement the car has seven fixed speeds forward and 
seven speeds reverse, together with the possible variations of both, 
which can be produced by the use of spark throttle and accelerator. 


Noise in Gear Operation. One of the most common of trans- 
mission troubles is a grinding noise in the operation of the gears. 
This is heard more in bevels than in spurs, but in old transmissions 
and on the lower speeds it is heard frequently. A good way to 
quiet old gears, after making sure that they are adjusted rightly 
and meshing correctly, is to use a thicker lubricant. If thick oil 
is being used, change to half-oil and half-grease or preferably all grease. 


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In this respect the repair man or amateur worker may take a 
leaf out of the book of second-hand car men, who are said to "load" 
an old and very noisy transmission gear with a very thick almost 
hard grease in which is mixed some shavings, sawdust, cork, or 
similar deadening material. When this is done, a graphite grease is 
generally used, so that the shavings, cork, etc., would not show in 
case it was necessary to take off the gear-box cover. This material 
will fill up all the inequalities of the gears and shafts so that tem- 
porarily everything fits more tightly, and all the sounding board, 
or echo, effect is taken out of the transmission case. This sounding- 
board effect is fully as important as the grinding noise, for many 
really insignificant noises are magnified by poorly shaped gear cases 


Fig. 294. Types of Gear Pullers 

so as to appear very loud, indicating serious trouble which need 
immediate attention, when such is really not the case. 

Another source of gear-set noise is a shaft out of alignment, 
caused either by faulty setting, by worn or loose bearings, or by 
yielding or cracking of the case. If it is properly set at one end and 
is out at the other, the trouble will be more difficult to find and remedy. 

Heating. Heating is a common trouble, too, but usually this 
can be traced to lack of lubricant in an old car or to too large shafts 
or too small bearings in a new one. Sometimes the grease used will 
cause heating, particularly when long runs are made with the trans- 
mission working hard. This is most noticeable when the grease or 
lubricant is of such a consistency that the gears simply cut holes in 
it but do not carry any around with them or do not otherwise circu- 
late the lubricant. This can be remedied by making it thicker so 
the gears will cut it better, by making it thinner so they will splash 
it more, or by changing the nature of it entirely. 


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Gear Pullers. One of the principal necessities for transmission 
work is a form of gear puller. These are like wheel pullers, except 
that they are smaller and more compact. In Fig. 294, a pair of 
gear pullers are shown. The one at the left is very simple, consisting 
of a heavy square bar of iron which has been bent to form a modified 
U. Then, a heavy bolt is threaded into the back of this or bottom of 
the U. This will be useful only on gears which are small enough to 
go in between the two sides of the puller, that is, between the sides 
of the U, which when in use is slipped over the gear, the screw turned 
until it ^touches some- 
thing solid, as the end of 
the gear shaft, and then 
the turning continued 
until the gear is 
forced off. 

While not as simple 
as this, the form shown 
at the right has the 
advantages of handling 
much larger gears, and 
also of being adjustable. 
As the sketch shows, this 
consists of a central 
member having slotted 
ends in which a pair of 
L-shaped ends, or hooks, 
are held by a pair of 

through boltS. Then Fig ^ Method of p re8 sing Transmission Gear 

there is a central work- onto its shaft 

ing screw. To use, the hooks are set far enough apart to go over the 
gear, then slipped around it and hooked on the back. The central 
screw is turned up to the end of the shaft, and then the turning 
continued until the gear comes off. There are many modifications 
of these two; in fact, practically every repair shop in the land has 
its own way of making gear or wheel pullers. At any rate, every 
shop should have one. 

Pressing Gears on Shafts. The opposite of pulling off gears 
is putting them on; very often they are designed to be a press fit, : 





which means exerting tremendous pressure. Every repair shop 
should have some form of press for this and similar work, something 
similar to the form shown in Fig. 295. In this figure, the man is just 
beginning to apply pressure to the shaft to force it into the lower 
gear. The table must be arranged for work of this kind with a solid 
spot when the shaft does not come through, and with a hole when it 
does. The work of pressing is usually done in a few seconds, while the 
preparation, alignment, and starting of the work takes perhaps half 
an hour or more. It is work which should be done very carefully. 
One way in which arrangement can be made for pressing a 
shaft a considerable distance into a gear and, conversely, for pressing 

the shaft out of the gear is that 
shown in Fig. 296. This figure 
has the additional advantages of 
being simple, easily constructed, 
and cheap. A solid base is 
constructed with a pair of 
hinged uprights. These can be 
dropped together with the work 
between them, forming a mod- 
ified triangle, the strongest 
known shape, resting upon its 
broadest side and thus having 
the greatest stability. With this 
arrangement, the press can 
used for pressing off parts. 
Diagnosis. The repair man should use a great 

Fig. 296. 

Home-Made Table for Use in Gear 

Pressing or Pulling 
Courtesy of "Motor World?' 

readily be 

Care in 

deal of care in doping out or diagnosing the trouble in a transmission, 
for, frequently, what appears at first to be at fault turns out to be all 
right, and something else is back of the first trouble, which must be 
corrected before a remedy can be applied. Recently, a repair 
man figured that a new gear was needed to repair a transmission. 
This was received from the factory three days later, but when he 
started' to put it in, he found that a bearing was defective; in fact, 
the defective bearing caused the wear in the gear. This necessitated 
a further delay of three days in order to get a new bearing. 

Poor Gear Shifting. A common transmission trouble is poor 
-gear shifting. This may be due to a number of different things. 


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For one thing, the edges of the gears may be burred so that the edges 
prevent easy meshing. When this is the case, any attempt to force 
the gears into mesh only burrs up more metal and makes the situa- 
tion worse. Whether this is the trouble or not can be determined 
very quickly and easily by removing the transmission cover and 
feeling of the gears with the bare hand; the burred edges can readily 
be distinguished. If this is the only fault, the transmission should 
be taken down, the gears taken out and placed in a vise, and the 
burrs removed with a cold 
chisel and file. 

Poor or worn bear- 
ings or a bent shaft or one 
not accurately machined 
may cause difficult shift- 
ing. If the bearings are 
worn, the difficulty of 
shifting will be accom- 
panied by much noise, 
both in shifting and after. 
The bent shaft is more 
difficult to find and equally 
difficult to fix. A new 
shaft is usually the quick- 
est and easiest way to 
remedy the trouble. 

Sometimes the con- 
trol rods or levers bind or 
stick so that the shifting 
is very difficult. In case 
the gears are difficult to 
"find" or will not stay in mesh, the fault may be in the shifter rod in 
the transmission case. This usually has notches to correspond to the 
various gear positions, with a steel wedge held down into these notches 
by means of a spring. The spring may have weakened, may have lost 
its temper, may have broken, or for some other reason failed to work. 
Or with the spring in good working condition, the edges of the 
grooves or notches may have worn to such an extent as to let the 
wedge slip out of, or over, them readily. - 

Fig. 297. Tank and Basket for Cleaning Gears and 

Other Parts 

Courtesy of "Motor World 1 * 


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Cleaning Transmission Gears. When the transmission is taken 
out of the case and has to be taken apart, and particularly if it has 
not been cleaned for a long time previously, it is advisable to clean 
all the parts thoroughly before attempting to work with them. 
The best way to clean the parts is to have a special cleaning tank. 
In Fig. 297 one of these is shown, which is not unlike the baskets 
used in some hardening processes. It consists of a deep metal *or 
metal-lined tank and a basket or tray, which is an easy fit in it, 
suspended from above by wire cables. The cables are brought 

Fig. 298. Handy Framework for Lifting Transmissions out of Chassis 

together on the wall, where a ring joining the ends and a series of 
nails or hooks make it easy to hold it at any desired elevation, either 
in or out. of the tank. The tank is filled preferably with kerosene. 
As soon as a part has been removed from the transmission, it is 
thrown into the basket, and when this is filled or all the parts are in 
it, it is lowered into the kerosene and allowed to stand, for a couple of 
hours if possible, but, if not, for as long as can be. When thoroughly 
soaked, the basket should be raised above the level of the liquid and 
-allowed to drain thoroughly. If it can be left for an hour or so to 


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drain, all trace of kerosene will disappear, while the gears, shafts, 
and other parts will be like new. 

Lifting Out Transmissions. When the trouble has been found 
to be in the transmission case or in some part that necessitates com- 
plete removal, it is often a tremendous job to get the unit out. Some 
units are attached from below and are not so difficult to detach. 
They are lowered by means of a platform of boards set on two or 
more jacks. But when it must be removed from above and no 
overhead beam is available, the hoist shown in Fig. 298 will be found 
very handy. As will be seen from the sketch, this hoist is simply a 
triangular framework constructed from angle iron to have the 
minimum height which will allow removal of the unit. The chain 

Fig. 299. Two Forms of Useful Transmission Stands 
Courtesy of "Motor World** 

fall is attached to a hook in the center, and the chains put around 
the case. When lifted up close into the V of the framework, the 
whole transmission can be put onto horses and moved along the 
chassis, or boards can be put under it and over the chassis frame to 
allow it to be worked there. Or, if desired, it can be lowered onto a 
creeper or other low platform with wheels aftd moved out of the way. 
This rigging can be used for many other similar purposes, although it 
is not suitable for the removal of an engine, radiator, or other part 
or unit which extends far above the chassis frame. 

Transmission Stands. When the transmission has been 
removed, if the work to be done upon it is all extended, a stand to 
support it is desirable; in fact, a necessity, if the work is to be done 
right. A pair of stands are shown in Fig. 299, the one at the left : 


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is made from pipe fittings and angle irons in such a way that the 
width between the rails can be varied to suit the transmission or 
engine. The stand at the right is more of a specialized type. It is 
constructed for a certain transmission and has clips to support it 
in the same way that it is held in the chassis. The latter frame may be 
smaller and more compact than the former, but the wide range of 
uses to which the former can be put make it more desirable in the 
average shop. 

Working in Bearings. When a great many bearing^ of any 
one transmission are fitted, it is well to make a jig for working in 
the cases to an exact size for the bearings, whether these be over 

Fig. 300. Method of Fitting Transmission Case Bearings with Dummy 

sizes or not. Such an outfit, Fig. 300, shows an aluminum trans- 
mission case with a pair of jigs for scraping its bearings into the case. 
These jigs are made of steel and are constructed to a very accurate 
size, the surfaces being hardened so they will show no wear. The 
jigs are painted with Prussian blue, put in place and turned, the 
markings scraped by hand, the jigs again put in place and turned, 
and this process repeated until a perfect bearing surface is obtained. 
Starting with an unknown size on the case and a known size of bearing 
which must go in it, a few of these jigs will soon save their cost in 
labor and time, by quickly producing the necessary size of case to 
. utke the bearings. 


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Fig. 301. Easy Way of Sorting and Keeping Old 

Bearing Balls 

Courtesy of "Motor World" 

Saving the Balls. If a great many ball bearings, particularly 
from transmissions, are used, and many bearings scrapped, it is 
advisable to save the balls. These balls will come in handy later for 
replacement or other uses. 
Moreover, balls are expen- 
sive, and good ones are hard 
to obtain. A handy way to 
take care of balls, without 
much work beyond cleaning 
thoroughly in the kerosene 
tank, is to construct a cab- 
inet like that seen in Fig. 301 . 
There are four drawers — or 
more if desired. The bottom 
of each drawer is a steel plate 
drilled as full of holes as pos- 
sible of the next smaller size, 
that is, a clearance size for 
the next round figure size. 
Then the cabinet does the sorting, all balls being put into the top 
drawer. The next smaller size is retained in the second drawer, the 
third size in the next, and so on. When using balls out of these 
drawers, the micrometer should be used to determine their exact size. 

Handy Spring Tool. In the Ford transmission-band assembly 
there are three springs which it is difficult to assemble because of 
the trouble in holding so many things at once. To eliminate this 
trouble, the tool, shown 
in Fig. 302, made from 
flat bar stock, can be 
constructed. The han- 
dles, if they could be 
called that, are pivoted 
together and carry a kind 
of flat jaw with three 
notches at one end. 
When the two of these are squeezed together by means of the screw 
and handle at the other end, the flat plates will hold the three springs 
tightly enough so that all can be inserted in their proper positions 

Fig. 302. Handy Spring Tool for Ford Assembly 


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at once by using but one hand. Tools of this kind, which save 
a great deal of the workman's time and thus save both time and 
money for the owner of the car, should, and in fact do, distinguish 
the well-equipped repair shop and garage from the old-fashioned 
kind which is in the business only for the money and not too par- 
ticular how it is gotten. 

In transmissions of the planetary type, there is little or no 
trouble except with the bands. If these are loose, the gears will 
not engage and the desired speed will not result. If they become 
soaked with grease, oil, or water, they will not work as well as if kept 
clean and, in the case of excessive grease, will slip continually. If 
the band lining becomes worn, it should be treated just as a brake 
lining is. When inspected for wear and found not badly worn but 
slippery, it may be cleaned in gasoline and then in kerosene, after 
which a saw, hacksaw, or coarse file may be used to roughen it. 
Sometimes greasy bands can be fixed temporarily — say, enough to 
get the car to a place where tools, materials, and facilities for doing 
the work are available — by sprinkling them with powdered rosin or 
fuller's earth. The former should be used sparingly because it will 
cause the band to bite or grab hold when forcibly applied, and at times 
has been known to cut into and score a cast-iron drum. As a rule, 
planetary transmission bands should be handled in the same way as 
ordinary brake bands, as to lining and relining, roughness of surface, 
lubrication, etc. 

Modern Transmission Construction and Repair. The transmis- 
sion and clutch unit of the LaFayette car is shown in Fig. 303. The 
clutch is a multiple-disc dry-plate type having a fabric lining riveted 
on the driven or smaller discs. The multiple-disc clutch is the most 
popular form now in use and the majority of the 1920 cars are being 
equipped with this type. The clutch spring is made of coiled flat 
wire and the thrust of this spring is taken up by a ball-thrust bearing. 
Pressure on this thrust bearing is had only when the clutch is thrown 
out or disengaged by the driver. This bearing should be lubricated 
occasionally so that it will not become noisy. If the clutch pedal is 
adjusted so that there is continual pressure on this bearing, it will 
wear out very rapidly. The dry disc plates will last for an indefinite 
time; sometimes, however, they become glazed and it is then necessary 
tr> soften up the fabric surface either with emery cloth or a little oil. 


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The transmission furnishes three speeds forward and one reverse. 
The majority of cars now have this speed arrangement. There are 
two gears on the sliding gear shaft — the low and reverse sliding 
gear and the intermediate and high sliding gear — that are placed 










in mesh with the proper countershaft gears when a speed change is 
desired. The sliding gear shaft is mounted at the front end in a 
pilot bearing of the roller type.* Bronze bushings were generally 
used at this place, but they were unsatisfactory as they wore 


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out in a short time. This pilot bearing is placed within the clutch 
shaft and this shaft is supported in the crank case by ball bearings. 
The countershaft is stationary in the case and is hollow so that oil 
can pass through this shaft and lubricate the roller bearings which 
.are placed between the countershaft gear assembly and the counter- 
shaft. A great number of transmissions have bearings on each end 
of the countershaft and the shaft revolves. There is a disadvantage, 
however, in this form of construction, as there is likely to be oil 
leaks at the ends of this shaft. The transmission drive gear is con- 
stantly in mesh with the main countershaft gear, causing the counter- 
shaft gear assembly to revolve whenever the motor is running. This 
continuous operation wears the roller bearings but very little as there 
is no power being transmitted through these gears unless one of the 
sliding gears is in mesh with one of the countershaft gears, or unless 
the high speed gears are engaged. The speedometer is driven by the 
gear that is mounted on the rear end of the sliding gear shaft. The 
universal joint of this transmission is mounted in the transmission 
case and is constantly lubricated by the transmission grease, thereby 
eliminating a great deal of wear and preventing oil leaks at this point. 
The universal joint is well supplied with felt grease washers that 
further prevent oil leaks in the transmission. 

Lubricating Transmission Gears. The transmission case should 
be filled with lubricant to a depth of several inches. Care should be 
exercised at frequent intervals to see that a proper amount of lubri- 
cant remains in the transmission case. Different makers recommend 
different kinds of lubricants for transmissions. In light cars a mixture 
often used consists of equal proportions of light grease and machine 
oil. In heavier cars a heavy graphite grease is often used. The 
proper lubricant depends upon the types of bearings used; thus for 
ball-bearing transmissions, no oil need be added. 

Change=Speed Lever Indicates Some Impediment in Transmis- 
sion, It is desirable to look for broken or mutilated gears, broken 
bearings in transmission shafts, sticking or misalignment of gear shafts 
or of their operating mechanisms. 

Adjusting Annular Bearings. Makers recommend that the 
inner race be pinched so tight that movement is impossible; the 


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puter race is sometimes allowed a little freedom — .002 to .003 


Since the whole subject of transmission concerns itself with 
gears, it will not be out of place to discuss the gears themselves 
and describe the many different kinds in use. Speaking broadly, 
the gears used may be classified according to the position of their 
axes, relative to one another. Thus we have axes parallel and in the 
same plane; parallel but not in the same plane; at right angles and in 
the same plane; at right angles and not in the same plane; at some 
other angle than a straight or a right angle and in the same plane; 
and the same, but not in one plane. These classes give us the forms 
of gear in common use, viz, spur gears, bevel gears, helical gears, 
herringbone gears, spiral gears, and worm gears. 

The spiral gear is being extensively used in automobile and air- 
craft motors. This form of gear is quiet in operation provided the 
teeth are cut at the correct angle, although a great deal of experiment- 
ing was necessary before the right angle could be determined. Worm 
gears are now giving such satisfactory service that nearly all the 
truck manufacturers are using them. 

Spur Gears. A spur gear is not only by far the most common 
kind of gear, but is also the easiest to describe, consisting, as it does, 
of a round flat disc with teeth cut in its circumference, i.e., around 
the periphery of the disc, as shown in Fig. 311. 

Bevel Gears. Bevel gears, in which the shafts are at right 
angles and in the same plane or in the same plane but not at 
right angles, are more difficult to cut and are therefore less used. 
They are now cut, like the spurs, in an automatic or nearly automatic 
machine, which requires little attention, but which does require 
more care than the spur-gear machine. Both spurs and bevels 
sometimes require a chamfered tooth jedge; spur gears as used in the 
Panhard, or clash-gear, transmission are always in need of it. This 
work was formerly done by hand, but now a special machine has been 
manufactured for this purpose. 

There are no real restrictions against the use of the spur and 
bevel, either or both being used interchangeably. Very often they 
are used in combinations which appear peculiar, as the one shown 



in Fig. 311. This is the final drive and reduction gear of the Autocar 
commercial cars, made by the Autocar Company, Ardmore, Penn- 
sylvania. In this gear, it will be noticed that the drive from the engine 
is through bevels to an intermediate shaft and that the final drive 
is by spur gears. 

Helical and Herringbone Gears. In situations where quiet 
running is deemed necessary, the use of a helical gear frequently finds 
favor, since it accomplishes the desired result, although the cost of 

Fig. 311. Combination of Gears in the Autocar Final Drive 

cutting is high. Of late, these gears have come into general use for 
camshaft drives and similar places. A pair of helical gears set so that 
the helices run in opposite directions forms a herringbone gear. 
This is even more quiet in its action than the single helix and pos- 
sesses other virtues as well. One well-known firm has adopted it for 
camshaft driving gears and makes it as described to save cutting- 
cost, as the cost of cutting a true herringbone would be prohibitive. 
So a pair of helical gears of opposite direction are set back to back and 
riveted or otherwise fastened together, forming a herringbone gear at 
a low cost. Both of these may be used when the two shafts are par- 


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allel and in the same plane, but for all cases where the shafts are 
neither in the same plane nor parallel, some form of spiral gear must 
be made use of. 

Spiral Gears. Spiral gears, as such, are not generally under- 
stood, but that variety of the spiral known as the worm gear is 
very simple and easily understood and it has attained much popu- 
larity within the past few years. This popularity has been due, in 
part, to superior facilities for cutting correct worms and gears, but, in 
the main, to a superior knowledge of the principles upon which the 
worm works and of the things which spelled failure or success. Thus, 
one of the earliest experimenters in this line laid down the law that the 
rubbing velocity should not exceed 300 feet per minute if success was 
desired or in rotary speed about 80 to 100 revolutions. For auto- 
mobile use, this was out of the question; but later experimenters 
found that these results only attached to the forms of gear used by 
the early workers and did not apply to a strictly modern gear laid 
down on scientific principles. 

The mistake made was in the pitch angle of the worm, which 
was formerly made small, nothing over 15 degrees being attempted. 
This was the item that was at fault and that caused this very useful 
and efficient mode of driving to fall into disuse. As soon as this 
fact was ascertained and larger pitch angles utilized, better results 
were obtained, until, with 20-degree angles, 700 feet per minute pitch- 
line velocity was attained, followed shortly by the use of even higher 
angles, resulting even more successfully. As the efficiency depends 
directly upon the pitch angle, these changes brought the efficiency 
of this form of gearing from the former despised 30, 40, and some- 
times 50 per cent up to 87, 88, and even 90 per cent, thus putting it 
on a par with all but the very best of spur gears and above bevel 
gearing. In fact, in the light of modern knowledge of worm gears, 
it could easily be said, without departing from the truth, that it 
is possible to obtain from this form an efficiency of 93 per cent. In 
automobile work, the worm gear has been used mostly for steering 
gears and final drives. In the former, its irreversible quality is 
brought out, while in the latter, this quality must be made subordi- 
nate to a great reduction, which may be attained in a very small 
compact space. The majority of modern machines make use of worm 


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Spiral Bevels. The spiral bevel is a new development, having 
been brought out in 1914 as a compromise between the worm and the 

Fig. 312. Rear View of Timken Worm-Diven Rear Axle 
Courtesy of Timken-Detroit Axle Company, Detroit, Michigan 

Fig. 313. LaFayette Driving Gear and Differential Construction 

straight bevel. As such, it is supposed to have practically all the 
advantages of both, except that it does not afford the great speed 


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reduction that can be accomplished with a worm in the same space, 
being more like the bevel in this respect. 

Among those using the spiral bevel are the Packard, Cadillac, 
Reo, Stearns-Knight, Velie, Kline, Apperson, Buick, Chalmers, 
Chandler, Cole, Haynes, Hupmobile, Jackson, King, Locomobile, and 
many others. Fig. 312 shows a worm-drive rear axle: Fig. 313 shows 

the construction of the 
LaFayette spiral bevel 
and the differential gears. 
Fig. 315 shows the spiral 
gearing of the Cadillac 
passenger car. 

Worm Gears. Prog- 
ress in the application 
of worm gears for rear- 
axle use has been con- 
siderable in the last few 
years. In one respect, 
at least, designers have 
found it an advan- 
tage. The top position 
for the worm was not 
much used at first, as it 
was thought impossible 
for it to receive sufficient 
lubricant there. Conse- 
quently, it was always 
placed in the bottom posi- 
tion, which cut down the 
clearance considerably; in 
this position the clearance 
was less than with the 

Fig. 315. Cadillac Helical-Bevel Driving Gear 

and Pinion ordinary bevel. With the 

proof that the worm could be lubricated in a satisfactory 
manner in the top position, the majority of gears are so placed, 
thus converting what was formerly a disadvantage into an 
advantage, for in the upper position the clearance is greater 
than with bevel gears. This is shown quite clearly in Fig. 312, 




where it will be noted that the worm-gear housing in the center 
is actually higher than are the brake drums at either end of the axle. 
This, too, despite the fact that a truss rod passes beneath the 
center of the axle. For heavy trucks, especially, and for electric pleas- 
ure cars, the worm has proved an ideal drive. In these situations, 
there is the condition of high-engine or electric-motor speed, coupled 
with low-vehicle speed requirements, which necessitate a considerable 
reduction. As pointed out, the worm gives this in a small space. 

For 1916, the very apparent tendency in final drives is toward 
spiral bevels for pleasure cars and worms for electrics and trucks. 
The tendency toward spirals is very great, amounting practically 
to a landslide, 57 per cent using it against 10 for 1915. The devel- 
opment of special machinery for cutting these gears and the under- 
standing of their use has brought this about. In the truck field 
there has been a similar movement toward the worm, due to similar 

Gear Pitch and Faces. The manufacturers of transmissions and 
of gears for them do not agree as to the best gears. Neither do they 
agree as to which gears are most quiet or most efficient. In general, 
coarse-pitch stub-tooth gears are gaining faster than any other form. 
The 6-8 pitch is fairly general for gears of f-inch and f-inch face, 
and 4-5 pitch for wider gears. One manufacturer, Warner, con- 
siders the finer pitch gears and narrower faces as less likely to make 
noise, since they will not distort as much in hardening as wider gears. 
In this, other manufacturers agree, but there are some who claim to 
have had both quiet and noisy operation with both fine and coarse 
pitch. The tendency toward compactness has not increased 
transmission-gear faces any appreciable amount, nor has the 
increased use of better steels and better hardening processes lessened 
the size of the four noticeably. 

Gear Troubles. Most of the common gear troubles have been 
previously covered at the end of transmissions. There is not as 
much trouble with gears today as there was several years ago. This 
is due to better design, better materials, better processes, and better 
assembling on the part of manufacturers and to more skill in handling, 
caring for, and adjusting on the part of owners. Of course, the 
repair man still finds plenty to do, but the percentage of gear repairs 
is relatiyely less than ever before. 





Q. Why is a clutch needed? 

A. The clutch is needed to disconnect the rest of the drive 
from the engine. The gasoline engine cannot start under a load but 
must first get up speed. By means of the clutch, which can be 
thrown out, the engine is allowed to run alone and get up the neces- 
sary speed, then the load or drive can be thrown on. This is just as 
true of the stationary gas engine as of the automobile, motor boat, 
or aeroplane power plant. 

Q. How does the clutch act? 

A. It is designed and constructed so that the amount of friction 
surface, with the spring pressure provided, is sufficient to transmit 
the whole power of the engine (and slightly more as a factor of 
safety) when the clutch is in. In addition, it is so designed ancj con- 
structed that when the clutch is out the spring pressure is taken up 
in such a way as to be self-contained, that is, its thrust is carried to 
a member outside of the clutch itself which is able to withstand this 
thrust. In this way, when the clutch is out, the engine is entirely 
free, and when the clutch is in, the connection is such that it will 
carry more than the maximum power of the engine. 

Q, To what type of clutch does this apply? 

A. This applies to all clutches, regardless of type or design, 
with the single exception of clutches on traction engines or on agri- 
cultural tractors. These are designed in the same way but work just 
the opposite, being engaged only when the clutch pedal is pressed and 
disengaged when it is released. On this account, the clutch is 
arranged so that it can be set to be in all the time or out all the time. 
With this exception, the arrangement described applies to all internal- 
combustion engines, although clutches vary widely in type, size 
and arrangement. 

Q. What are some of the most popular forms of automobile 

A. The cone, multiple-disc, and single-plate clutches are used on 
the 1920 cars exclusively; the single-plate type is used on about 
50 per cent of these cars. Users of the disc and the cone clutch 
are about equal in number. 


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Q. What were the two divisions of the cone form? 

A. The cone form was made in two ways, the direct form and 
the indirect form. The direct form has the cone introduced directly 
into the flywheel, which is tapered inwards for this purpose. This 
makes it a very simple device to construct, the machining of the fly- 
wheel forming the female portion of the clutching surface. The indi- 
rect form, or inverted cone, differs in that the female portion is made 
as a separate flange bolted to the flywheel and tapering outward. 
The cone is placed inside of this, so that it works out against the 
clutching surface instead of in against this surface, as in the direct type. 

Q. What are the relative advantages of the two forms? 

A. The indirect is not used now, although it was popular years 
ago. The extra bolted-on inverted cone adds to the flywheel weight, 
for it is large and heavy and gives considerable flywheel effect. How- 
ever, the flywheel is simplified. The spring is enclosed between the 
flywheel and the cone, this being considered an advantage in the early 
days but now considered a disadvantage because it is inaccessible for 
inspection or adjustment. The cone is pushed in — away from the 
clutching surface — to disconnect it, while on the more simple direct 
type, the cone is pushed out — away from the clutching surface — to 

Q. What are the divisions of the disc clutch? 

A. Disc clutchej are generally grouped according to lubrication, 
those which run in oil being called wet, and those which run without 
lubricant of any kind being called dry. In addition, a distinction is 
generally made between the disc clutch with a very few plates (one, 
two, or three), usually called a plate clutch, and the form with many 
plates (10 or more) which is called a multiple-disc clutch. Either 
plate or multiple form may run wet or dry. 

Q. Explain the difference between the wet and dry multiple 

A. In the wet form, the plates, or discs, are plain steel and are 
submerged in oil, the entire clutch housing being filled with oil. The 
clutch discs work steel face against steel face, the action of the spring 
when the clutch is let in gradually squeezing out the oil from between 
the faces. This gradual squeezing out of the oil gives this form its 
gradual-application quality, for with six or seven pairs of dises the 
squeezing-out process takes an appreciable length of time. In the 


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dry form, the plates are ordinarily faced with a special clutching 
surface of woven asbestos fabric similar to brake lining, this being 
placed upon every alternate disc, that is, the actual clutching surfaces 
consist of steel and fabric alternating. The general method of con- 
struction is to take one set, say the inner discs, and face both sides of 
each one. Then none of the outer discs are faced, so that when the 
clutch is assembled there is a steel face against each fabric face. This 
form is run absolutely dry; in fact, considerable pains is taken in 
design and assembly to keep out any form of lubricant. 

Q. Explain the difference between the plate and the multiple- 
disc forms. 

A. In the multiple-disc form, a considerable number, say 11, 13, 
15, or some such number of discs, is used; the smaller number, as 5, 
6, 7, etc., being the driving, and the larger half, as 8, 9, 10, etc., being 
the driven. In the plate form, a very small number of plates of the 
largest size which the flywheel will allow is used. As a rule, the fly- 
wheel inner surface is machined out to form one of the surfaces, the 
engaging or disengaging member another, and a single disc between; 
or, perhaps, another large disc is fixed to the flywheel and two discs 
used between this and the other two surfaces. The plate form has the 
advantages of a small number of parts and of compactness; but, on 
the other hand, the discs are so large and heavy that assembling is 
not so easy and a considerable flywheel effect is produced. More- 
over, it is not so easy to produce an absolutely flat surface in the 
larger sizes, for which reason the clutching is not so even and smooth. 
In the smaller sizes, no attempt is made at perfectly flat surfaces, as 
the inequalities balance one another. 

Q. What is the general tendency in cone-clutch surfaces? 

A. As to size, the tendency is toward larger diameters and 
smaller or narrowed clutch faces. As to materials, asbestos woven 
fabric is gradually replacing leather. Light springs under the fabric 
form the means of gradual engagement, corks going out with the 
leather with which they were used. 

Q. What is the general form of the clutch spring? 

A. Formerly, all clutch springs were of spring wire of the maxi- 
mum possible diameter and, therefore, very stiff. The modern 
tendency is toward a distribution of spring pressure by means of a 
number of smaller weaker springs. The former method almost invari-i 

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ably called for complete enclosure, making adjustments and replace- 
ments difficult. The smaller springs are usually placed outside, 
so that they can be adjusted or replaced easily and quickly. It has 
been found, too, that by using a large number, say 6, 7, or more, 
distributed around the clutching surface, a much lighter spring pres- 
sure can be used with equally good effect. In fact, many modern cars 
have so light a clutch spring that it can be disengaged with one finger. 

Q. How does the contracting-band clutch work? 

A. It has two half-bands which the clutching mechanism draws 
tight against a drum. In effect, a contracting-band clutch is like a 
band brake, except that the braking band is in two halves and operates 
from the center instead of from the exterior surface. 

Q. Is this a popular form? 

A. No. It has gone out of use; only one or two American cars 
have used this type in the last five years. 

Q. How does the expanding=band clutch work? 

A. In a somewhat similar manner to the expanding, or internal, 
brake; that is, it has two segments of fairly stiff metal section, which 
the movement of a cam, or expander, presses outward against the 
inside of the clutch drum (or inside face of the flywheel). This cam, 
or expander, is worked by the movement of the clutch pedal, or spring 
— outward so as to expand the band and take hold of the drum for 
engagement; inward so as to allow the band to contract. 

Q. Is this type gaining in popularity? 

A. No. On the contrary, it has lost so rapidly that there are 
no cars built in this country with it, although a few old cars with this 
form are still running. 

Q. What is the usual position of the clutch? 

A. Within the flywheel. This saves a great deal of space, a 
number of parts, and considerable weight. 

Q. Why is this position used so freely? 

A.. Partly because of the savings just mentioned, and partly 
because of the rapidly growing use of unit-power plants which forces 
this location. With the engine and transmission as a unit and the 
necessity for the clutch being between them, the flywheel interior is 
about the only place for the clutch. 

Q. How can the surface, and thus the transmitting power, of 
clutch discs be increased? 

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A. By the use of other than plane surfaces. Thus, in the Hele- 
Shaw form each disc is made with a small cone projecting from it. 
The outside of this engages with the interior of the cone on the next. 
Other forms have half-cone or other inclined surfaces and half-plane 
surfaces. As a straight line is the shortest distance between two 
points, so a plane flat surface gives the smallest area between any two 
points in parallel surfaces. From this it is apparent that any surface 
not plane offers a greater area than does the plane one. However, 
the plane surface is so much easier and cheaper to make, use, replace, 
etc., that it has gradually driven out all these forms with greater sur- 
face despite their advantages in the way of transmitting power. 

Q. What causes a slipping cone clutch? 

A. A slipping cone clutch is generally caused by oil, grease, or 
other lubricant on the clutching surface or by a weak spring. 

Q. How can this be remedied? 

A. The surface can be cleaned with kerosene, then with gaso- 
line, and dried. Or, if the surface is glazed, it can be roughened by 
using a file. Or, if the slipping occurs out on the road and no tools 
are available, any powder or fine material which will give roughness 
can be used. It is possible to get home with a slipping cone clutch 
by de-clutching and forcing in some sand. Of course, this is not 
advisable, but it works in an emergency. 

Q. What causes a disc clutch to slip? 

A. In a metal-to-metal type, a burred plate or a weak spring 
or a very thin oil which can not all be squeezed out will prevent 
engagement. The two latter causes are easily remedied; the former 
means removing the clutch and taking it apart to find the plate which 
is burred or roughened. In a faced, or dry disc, clutch slipping may 
be caused by oil, grease, or other lubricant getting in on the surfaces 
or by a weak spring. 

Q. What other things may cause a clutch to slip? 

A. The pedal may be held out, when it appears to be in, by the 
emergency brake interlock, by a bent or twisted rod, by a rod which 
presses against something, by a tight-fitting pin in one of the con- 
nections, by a worn pin, or by a bent-clutch spider which cannot 
contact all over because of this bend. 
Questions for Home Study 

1. Describe in detail the construction of the Studebaker clutch; 



2. Tell how you would adjust the Steams-Knight clutch springs. 

3. Give the method of removing and replacing a clutch spring 
in the Warner clutch. 

4. If springs under the clutch facing of a cone clutch do not 
produce gradual engagement, what is the matter, and how would you 
remedy it? 

5. How does the Cadillac clutch work? 

6. How does it differ from other clutches of the same type? 

7. How would you lubricate a clutch bearing, with what, and 
how often? 

8. Describe a quick, easy method of replacing corks in a clutch. 

9. How would you construct a device to hold clutch springs 
while replacing them? 


Q. What is the purpose of the transmission in a motor car? 

A. To allow variations in the speed of the car forward from the 
lowest to the highest, and for reverse, without varying the motor 
speed greatly. 

Q. Why cannot the engine speed be varied directly, doing 
away with the transmission? 

A. The lowest speed used in cars ordinarily would not be pos- 
sible with the present engine, since it could not be throttled down 
slow enough. Again, if the gearing were such as to give the present 
lowest car speeds with the engine low speed, then for maximum engine 
speeds the highest possible car speed would be very low. In short, 
gearing is necessary to give a greater variation than is possible with 
the engine alone. Further, reverse could not be obtained without 
additional gears and this would necessitate also a method of shifting 
the reverse gear into, and out of, mesh. Thus, all the requirements of 
the modern gear transmission would be necessary for reverse alone. 

Q. Show by the use of figures the impossibility of doing with- 
out the transmission. 

A. The circumference of 34-inch wheels is 136.8 inches, or 11.4 

feet. With the engine geared direct to the wheels, the speed of the 

latter would be directly proportional to the former, considering the 

gear reduction. If an average present-day gear reduction of 3.8 to 1 

disconsidered at 240 r.p.m., which is very low, the car would make 


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10.3 m.p.h. as its lowest possible speed. And at 2400 r.p.m. — a high 
maximum for an engine with as low a speed as 240 — the highest car 
speed would be 103 m.p.h. As the average roads would not allow this 
high a speed, and as the average car has a low speed approximating 
3 m.p.h., it is apparent that the gear ratio is too high. By lowering 
this to 12 to 1 at a low speed of 264 r.p.m. of the engine, a low car 
speed of 2.85 m.p.h. would be obtained. And with 2640 r.p.m. as the 
highest engine speed, the highest car speed would be only 28.5 m.p.h. 
From these two extremes, it is apparent that direct gearing without 
a transmission is not feasible. 

Q. What are the general classes of transmissions? 

A. There are five general classes: sliding gear, individual clutch, 
planetary, friction, and miscellaneous types. The first named is most 
popular and constitutes perhaps 90 or more per cent of all the cars 
now built. The individual clutch is really a modification of the slid- 
ing gear, but is not widely used — not to exceed 3 or 4 per cent. The 
planetary is the most simple form to operate but, unlike the others, 
is limited as to the number of possible speeds. Practically the only 
American maker using this today is Ford. The friction form was 
intended to give a maximum number of speeds with maximum sim- 
plicity. It does this, but other faults offset these advantages. Mis- 
cellaneous transmissions include what might be called the unproved 
inventions — forms which have not been tried out sufficiently to be 
proved successes. It includes hydraulic, electric, and various other 
forms of transmissions. The Owen Magnetic cars have been using 
the magnetic transmission for several years. 

Q. What is the average number of speeds? 

A. Three is the most popular number, four is found on a number 
of high-class cars, the planetary can give but two, the friction form 
may give five or more, the only magnetic form on the market gives 
seven. In general, three is considered sufficient; even the highest- 
priced makers are gradually giving up the use of four-speed gear 
boxes, and the number of these is less each year. 

Q. What are the three methods of gear shifting now in use? 

A. The selective form accounts for about 99 per cent. The 
progressive form has been discontinued except in a few trucks, and 
electric shifting is used by but one maker. 

Q. How does the selective form work? 


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A. The operator is at liberty to select any gear he desires and 
to go directly to that speed from the speed which he is using. This 
means with common sense reservations; for instance,* it would be 
foolish to go from high to reverse, although this is possible in this 

Q. How is this accomplished? 

A. Within the gear box, the gears are shifted by forms, and the 
quadrant arrangement is such that the driver can shift his lever so as 
to pick up the fork which will give the desired speed. Usually there 
are but two shifting members (in the three-speed form), one giving 
low speed and reverse, the other intermediate and high. Having 
picked up the low and reverse fork, he can shift his lever forward for 
low and backward for reverse; similarly, with the other fork for 
second and third speeds. 

Q. How does the progressive form work? 

A. In this type of gear box, the speeds must be used in succes- 
sion — first the low, then second, then high, and when slowing down 
from high, to second, then low, then reverse. For instance, if driving 
in high and a turn is passed in a narrow road, it would be necessary 
to shift down to second, then to low, then to reverse. The driver 
could now back his car past the street into a position which would 
enable him to make the turn. Then he could speed up the car again 
by using first low speed, then second, and finally high. This maneu- 
ver could not be accomplished in any other way. In the same cir- 
cumstances with a selective gear, the car could be brought to a dead 
stop with the brakes, an immediate shift to reverse effected, the car 
backed up, and the gears shifted to low and then high speed forward, 
thus doing the same thing as before with half as many changes. 

Q. How is the high speed generally effected? 

A. High speed in all modern transmissions is a direct drive so 
that none of the various gear reductions are in use. This method 
reduces the amount of noise by eliminating at once the meshing of 
two sets of gears, the average high-speed direct drive being effected 
by clutching one gear up to another. 

Q. Is this arrangement always used? 

A. No. In some four-speed gears the highest speed is a geared- 
up form, and the direct drive is used on third speed. This is done with 
the idea of secur ; u^ the silence of the direct drive for all average 


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rapid driving, while the geared-up form gives an extraordinary speed 
for emergencies where noise is immaterial. 

Q. In the electric gear shifter, how is the movement of gears 

A. The shifter is made with a series of electromagnets, or sole- 
noids, one for each speed and one for reverse. Current flows to these 
when the proper button is pressed. It is well known that when an 
electric current is passed through an electromagnet of the solenoid 
type, »the rod, or bar, inside of it is drawn forward. This arrangement 
produces the speed corresponding to the button pressed. In actual 
practice, the current does not flow until the clutch pedal is depressed 
after the button has been pressed. 

Q. Where is the transmission located? 

A. Excluding freak forms, there are four general positions: in 
unit with the motor; amidships in unit with the clutch; amidships 
but separated from the clutch and in unit with the forward end of the 
driving shaft; and in unit with the rear axle. 

Q. Are these same locations used on motor trucks? 

A. Yes. Except that the third class is sometimes modified with 
chain drive, so that the transmission is amidships but in unit with 
the jackshaft. 

Q. Which of these is most popular? 

A. The form in which the transmission is grouped with the 
motor and clutch, that is, the unit power plant, is now the most 
popular, and the tendency among the makers is to make it more so. 
It is gaining at the expense of all other locations. 

Q. What difference is noted in gasoline railway-car trans- 

A. As all speeds must be used in the reverse direction, the design 
is so modified as to allow the driver first to choose the direction and 
then to utilize all his transmission speeds in that direction. 

Q. What is the difference between individual clutch and other 
transmissions, particularly the sliding=gear type? 

A. In the individual-clutch type, no one of the gears is fixed to 
its shaft, but an individual clutch is provided for each. The purpose 
of this is to clutch the gear to its shaft so that it can drive or be 
driven. When shifting gears, the driver moves the usual lever in the 
usual way, but within the transmission this lever, instead of moving 




a gear on a shaft to which it is keyed, moves a clutch which keys the 
desired gear to the shaft. 

Q. What is the advantage of this over sliding gears? 

A. In the sliding gear, the moving members must take the drive 
and transmit the power in addition to withstanding the shocks and 
destructive action of shifting or meshing. In the individual clutch 
form, the gears have only to transmit the power, while the individual 
clutches have only the shocks and destructive action of shifting. 

Q. How are gears pressed onto their shafts? 

A. Usually by means of a hydraulic or a power press — one 
capable of exerting a pressure of many tons. Generally, it is easier 
to lay the gear out on the press table and press the shaft down into 
it, than the reverse. 

Q. How are pressed-on gears removed? 

A. The process of pressing on is reversed, and the gear is sup- 
ported in such a way that the shaft can be pressed, or forced, out of it. 

Q. How is the transmission removed from the chassis? 

A. The usual method in well-equipped shops is to put a rope 
or chain sling or special cradle around the transmission, then to lift 
it vertically upwards by means of a block and tackle, electric or pneu- 
matic overhead hoist, chain block attached to overhead tracks, or 
portable crane. 

Q. How are bearings worked in? 

A. After slow careful fitting by hand for both diameter and 
length, using a dummy shaft with dummy bearings, the real bearings 
should be put in place and run-in for several hours, using power from 
a line shaft. Transmission bearings should be run-in the same as 
engine bearings, set up somewhat tight and with an excess of oil. 
Questions for Home Study 

1. Describe the construction of the Cadillac and Winton trans- 
missions, a railway transmission, the Mack truck, the Ford planetary, 
a friction form, and a magnetic type. 

2. How would you adjust the shafts longitudinally in the 
Stearns transmission? 

3. Tell how to construct a stand for gear pressing. 

4. Give a thorough method of cleaning a transmission. 

5. What are the usual gear pitches? 

6. What is meant by the pitch of a gear? 


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The mechanisms by which steering is effected are among the 
most important features of a car, if not actually the most important. 
The truth of this statement will be realized when attention is called 
to the fact that safe steering is the final requisite that has made the 
modern high speeds possible, for without safe and dependable steering 
gears, no racing driver would dare to run a machine at a high rate of 
speed, knowing that at any minute the unsafe steering apparatus 
might shift the control, thus allowing the front wheels to waver and 
the car to run into some obstruction by the roadside. 

The same argument applies in an even greater degree to the 
case of the non-professional driver, who wants to be on the safe side 
even more, perhaps, than do the dare-devils who drive racing cars. 
Nearly all of our roads are curved and, to make all of these turns 
with safety, the steering gear must be reliable. Again, in mountain- 
ous country where there may be a sheer drop at the roadside of 
hundreds of feet, it becomes necessary that the steering mechanism 
be very accurate and that it obey, at once, the slightest move 
on the driver's part. To secure this accuracy, there must be no lost 
motion or wear of the interrelated parts. 

These things mean that the whole steering mechanism must be 
safe and reliable; strong and accurate; well made and carefully fitted; 
well cared for; and finally, the design and construction must be 
based on a theoretically correct principle, for otherwise the mechanical 
refinements will have been wasted. Perhaps it will be more logical 
to treat the mechanical requirements first by showing how the 
present type has been evolved from the failures of earlier forms. 

General Requirements. In turning a corner a car follows a 
curve, the outer wheels obviously following curves of longer radius 
than do the inner wheels and, therefore, traveling farther. In 


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straight-ahead running, the wheels run parallel at all times and 
travel the same distance. These two facts are the basic ones which 
make the steering action so complicated: First, that on straight- 
ahead running the wheels must travel the same distance; and second, 
that on turning curves the outer wheels, whichever they may be, 
must travel a greater distance. 

This double requirement leads to the usual form of steering 
arrangement, called after its inventor, the "Ackerman". It was 
Ackerman who brought out the first vehicle in which the front 
wheels were mounted upon pivoted-axle ends, these ends being pivoted 
on the extremities of the central part of a fixed axle, while the pivoted 
ends carried one lever each. These levers were connected together 
by means of a cross-rod, while at one end another rod was attached, 
which was used to move the wheels. By moving this latter rod, 
both wheels were compelled to turn about their pivot points, since 
the cross-rod joined them together, and if one moved the other had 
to move also. This was Ackerman's substitute for the fifth wheel 
which had been used up to that time and is even today on all horse- 
drawn vehicles. 

Inclining Axle Pivots. The situation is further complicated 
by the fact that the ideal arrangement, that is, the fixing of the steer- 
ing pivot at the center of the turning wheel in order to allow the maxi- 
mum turning movement for the minimum motion of the hand, is not 
suitable for general use. In practice, however, it is placed as close 
to the ideal position as possible, which, in the ordinary case, is within 
three to six inches. 

This approximation to the ideal has been made by inclining the 
stud-axle pivot inward, so that its center line prolonged would strike 
the ground at a point coincident with the center line of the tire. This 
same result is also brought about by inclining the stud axle itself 
downward. The construction gives added safety, in that the force 
of head-on collisions is supposed to be delivered at or near the line 
of incidence. 

The axle-spindle center may be brought close to the wheel hub 
by means of a double yoke, but this was tried and abandoned as 
too cumbersome for the results effected. A method of placing the 
steering pivot in the center of the wheel was also developed. In this 
case the pivot was enclosed in a hollow hub; but as this made the 


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pivot, which is liable to wear, inaccessible, it also was abandoned. 
However, later tendencies point toward a revival of this construction. 
The result is that today we are using a form which, though far 
from being ideal, fulfills every practical requirement. This form is 
usually constructed as in Fig. 316, which shows a skeleton plan view 
of an automobile. In this, the line AB represents in length, posi- 
tion, and direction, the front axle of a car, while ML represents 
in a similar manner the rear axle. A and B also are the pivot points 
for the axle-stud ends or, as they are more commonly called, the 

Fig. 316. Diagram of Steering Connections 

steering knuckles or steering pivots, which are represented by the 
lines AD and BC. 

The rear (or front, as the case may be) ends of the steering 
knuckles are joined by the connecting rod DC. The Ackerman con- 
struction is such that the center lines of the steering arms, or levers, 
AD and BC, prolonged, must pass through the center point of the 
rear axle at K; the reason for this is that the front wheels arp sup- 
posed to turn about the center of the rear axle as a center. 

Action of Wheels in Turning. If the wheels are supposed to 
turn through an angle, the action of the above arrangement will be 
seen. Suppose the steering gear (not shown in Fig. 316) is turned so 
as to move the steering lever AD to the new position, shown dotted 
at AD i. This movement will also move the other lever BC to a new 
position, shown dotted at BC\. It will be noted in this position that 
the angle through which the right-hand lever BC has swung is not as 




great as that through which the left-hand lever AD has moved, 
although the two levers are attached together by means of the cross- 
connection DC. 

The wheels are mounted upon the extremities of the steering 
knuckles at F and I; EG represents the left wheel, and HJ the 
right wheel. These turn about the pivot points A and B, with 
the movement of the steering knuckles to the new positions, shown 
dotted at EiFiGiand H1I1J1. In this position, prolongations 
of the lines through the pivot point and the center of the two 
wheels will meet the rear-axle center line prolonged at separate 
points as OP, the two lines converging slightly. This same con- 
vergence may be noted by prolonging the center line of the two 
wheels Ei Gi to Q and Hi Ji to R. This divergence means that 
the two wheels are turning on curves of different radii, and since the 
outer wheel Hi J x shows a longer distance from its center line pro- 
longed to the rear-axle line OPM KL than does the inner wheel, 
that is, has the longer false radius, PIi being longer than OFi, it 
follows that the turning action will be correct. 

This is somewhat complicated and rather hard to follow, but 
the figure seems simple and should be examined closely, even draw- 
ing it out step by step, as outlined above, for the purpose of making 
the steering action clear. Laying this out for one's self will bring 
out the reason why the steering knuckles do not move through the 
same distance and thus bring about a different movement of the 

Steering Levers in Front of Axle. That the final movement 
of the wheels will not be changed if the levers, Fig. 316, are laid out 
in the same way but in front of the axle will be evident by prolong- 
ing the levers to S and T, respectively, making the lengths AS 
and BT the same as the former lengths AD and BC. Connecting 
the two by the rod ST completes the front arrangement, which i« 
seen to give the same results as the other. The choice of a front oir 
rear location depends upon certain things, such as the safety of the 
cross-rod, etc., which will be brought out later on. Some machine 
manufacturers even go so far as to fit both front and rear levers to 
the same machine. 

While shifting the lever from rear to front in Fig. 316 does not- 
change the result at all, in Fig. 317 it does. In this construction, 

94 jOG 



known as the Davis, the steering levers are set in front, but taper 
inward instead of outward, so that their center lines prolonged 
meet the center line of the car prolonged at a distance from the front 
axle equal to the distance between the front and rear axles, or equal 
to the wheel base. 

In addition, the connecting rod is carried in guides placed on 
the front of the axle, so that its path of travel is always parallel to 
the front axle. Consequently, the levers must be made slotted or 
telescopic. The result of this combination of movements is an 

Fig. 317. Patented English Steering Device, Said to be Theoretically Perfect 


absolutely correct angle to both wheels for any angle of lock, 
can be explained by a reference to the diagram. 

In Fig. 316 the prolongations of the wheel center lines, or radii of 
turning, do not strike the center line of the rear axle— about which 
they are supposed to turn — at a common point, the difference being 
the amount they are out of true, viz, the distance between the points 
and P. If Fig. 317 be lettered to correspond with Fig. 316, the 
prolongations of the knuckle center lines AF x O and IiBP in 
Fig. 316 become the two converging lines AFiO and IiBO meeting 


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point on the center line LMO of the rear axle prolonged, 
is as it should be and shows the case of correct steering and 

In this case, all four wheels are turning about the point 0, the 
two rear wheels with the radii OM and OL, and the two front wheels 
with the radii 0F X and 0I\, respectively. This gives a theoretically 
correct case in which all wheels will round any curve as they should 
and not slip or slide around, damaging the tires in the process. - The 
Davis type of steering gear, it may be remarked, is not in general 
use, its construction adding a number of parts to the more usual form, 
shown in Fig. 316, which gives close enough results for average use. 

Like the sliding-gear transmission, a steering gear is a form of 
mechanism which, although used on nearly all automobiles, is, from 
a theoretical and mechanical standpoint, far from what it should be. 

General Characteristics of Steering Gears. Standard Types. 
The movement or deflection of the front road wheels is obtained by 

Fig. 318. Typical Steering Gear and Connections to Front Axle 

.a crosswise movement of the tie rod which links the steering-knuckle 
levers attached to the wheels. This tie rod, sometimes referred to as 
the cross-connecting rod, is actuated by the drag link GF, Fig. 318, 
which is pivotally mounted on the steering-knuckle lever L. The 
drag link has a linear movement along the frame and is parallel with it. 
The drag link is also pivotally mounted at the ball arm of the 
steering gear C, and when the drag link is moved forward or back- 
ward by movement of the ball arm, the tie rod is moved at right 
angles, deflecting the wheels. The drag link has a semi-rotary 
motion; that is, its upper end is turned through a part of a revolu- 
tion while ita^ lower end, to which the drag link is attached, swings 


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through a fairly large arc, according to the capacity and design of 
the steering gear. 

As the ball arm swings through its arc, the drag link attached to 
it rises and falls slightly, the movement being indicated by the dotted 
lines in Fig. 318. The partial circular motion in a vertical plane is 
converted from the rotation of the steering gear in a horizontal plane 
by several methods. The gear shown in Fig. 319 is known as the 
worm and sector type, which is illustrated in Fig. 318. 

In Fig. 319 the steering column or post CD carries a worm F 
which is in mesh with the gear E. 
Rotating the column CD in the 
direction indicated by the arrows, 
or counter-clockwise, will result 
in the worm turning in the same 
direction. The gear E will rotate 
on its horizontal shaft in a down- 
ward movement, as shown by the 
arrow, and as the ball arm, or 
lever, is attached to the shaft, the 
member L will move backward, 
or to the left, as shown by the 
arrow intersecting the ball. With 
the worm type the two gears are 
usually in two different planes 
at right angles to each other, one 
vertical and the other horizontal. 
This is an advantage in that it 
lends itself readily to the con- 
struction of a simple steering- 
gear system. Thus the post is in a vertical or modified vertical line, 
as is also the motion of the steering arm, and the consequent 
movement of the steering rod is more or less confined to a vertical 
plane. With the worm and gear this is obtained in a simple manner. 
The gearshaft is in a horizontal plane passing through the center line 
of the worm. If the worm rotates in a direction which approxi- 
mates a horizontal circle around a vertical axis, the worm gear will 
turn in a vertical plane about a horizontal axis. A lever attached 
to the end of this shaft will, consequently, move in the desired 

Fig. 319. 

Worm and Partial Gear of Typical 
Steering Gear 


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plane-f the vertical one mentioned before— and the desired require- 
ments kre met. 

The conversion of rotary motion in a horizontal plane to partial 
rotation in a vertical plane is shown in Fig. 320, the action here being 
slightly amplified. The steering, or hand, wheel A with spokes B is 
turned to the left, turning the steering column C (a hollow tube) in 
the direction indicated by the small arrow. D is the steering gear 
with its ball arm E. The turning of the hand wheel moves the 
ball end F and drag link backward. The front end of the drag link 
is attached to the steering knuckle M at H and turns about the 
center line K L of the steering knuckle J, the end turning through 

Kg. 320. Steering Mechanism and Front Axle of Pierce-Arrow Car 
Courtesy of Pierce-Arrow Motor Car Company, Buffalo, New York 

the arc HI. The lever M is attached to the knuckle J and turns with 
it. Its end turns through the arc OP, moving the tie rod OQ to the 
right and turning the other knuckle in the same way and direction. 
Y Y are the spring pads and ZZ the tapered roller bearings support- 
ing the road wheels. 

Classification. There are three general forms of steering gears: 
the worm, the bevel, and the spur. These may be subdivided, 
which might lead one to assume that there are a dozen or more 
different forms. The mechanical lever has been discarded because of 
its tendency to impart all road shocks to the driver; it is .fully revers- 
ible at all times. Irreversibility is employed because it transmits to 


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the road wheels any turning movement imparted by the driver 
without reversing or carrying back to the operator the original 1 inoye- 
ment of the road wheels. -~ '■' 

Many attempts have been made to substitute another form of 
mechanism for steering gears; this consists of various rod, lever, 
chain, and spring combinations. All of these have failed, however, 
because they lacked the 
fundamental requisite of 

Aside from the many 
schemes mentioned which 
seek to avoid the use of 
the regular gear in the 
standard manner, there 
have been a number of 
unsuccessful attempts to 
avoid its use in other 
ways. Fig. 321 shows 
some of the gears which 
have been tried. At 1 is 
seen a device in which the 
rotation of a large bevel 
gear turned a small bevel 
pinion, the rotation of the 
latter serving to screw a 
long straight lever with a 
threaded inner end into or 
out of the interior of the 
threaded bevel pinion. 

In the figure, N is the 
actuating bevel turned by 
the movement of the operator's hands, while is the smaller actu- 
ated bevel pinion. Within this is seen the worm end S of the 
lever J, the ball at the outer end being connected to the steering 
knuckle. Since the bevel alone lost a great deal of power in friction, 
while the worm arrangement and the sliding action of the lever in 
its bearings did likewise, the total effort. to turn this must have been 
enormous. At 2 is shown another form, which is the double-bevel 

Fig. 321. Obsolete Forms of Worm Steering Gears 


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arrangement; a small bevel N attached to the steering post K turns 
the larger bevel 0, which is pivoted at the axis M about which the 
lever J attached to the segmental bevel turns. 

A most peculiar arrangement is shown at 8, this being a com- 
bination of a worm and nut, two levers and a steering arm, as well 
as a connecting link for the two levers. Turning the hand wheel 
turns the worm, which moves the nut up or down. Since the nut 
is connected by means of the link to the lever, the motion of the 
nut up and down is transmitted to the short lever; this, in turn, 
moves the long-arm, or steering, lever. In the figure, K is the steering 
post, N the worm, the nut, P the connecting link pivoted at the 
two ends T and S, Q the short-arm lever, and J the steering lever, 
the two latter being integral and pivoted at the point R. At 4 
is shown a combination of a double internal worm with a rack tod 
gear. In this, the turning movement of the inner worm causes the 
outer worm to travel up and down. Upon the exterior of this outer 
worm is cut a rack which is meshed with the gear, its up and down 
movements turning the gear around and thus effecting the steering, 
the steering lever being attached to the gear. N is the internal 
worm, the external wo An with the exterior rack, P the gear which 
meshes with it and carries the lever J as a part of it. At 5 is shown 
a combination of a double worm with a double ball and socket 
arrangement. The turning of the outer worm JVi causes the inner 
worm N to rise and fall, the lower end of this carrying a ball-and- 
socket joint 0, the end of the ball being formed integral with the 
steering lever J, which also has a ball and socket attachment at the 
other end. At 6 is shown a steering gear which was tried and dis- 
carded, but which is now coming to the fore and bids fair to oust 
many other forms of gear. It is variously called a globular worm, 
helicoidal worm, or Hindley worm, the worm forming a curve closely 
approximating the curve of the gear with which it is to mesh. This 
gives a greater number of teeth in mesh at any one time, spreading 
the wear over a larger surface and thus lengthening the life as well as 
accuracy of the steering gear. 

Spur and Bevel Types. The spur- and bevel-toothed construc- 
tion of gears may be reversible, and these types are to be found on 
low-priced cars, as the cost of cutting the gears is small. The spur 
gears have straight teeth, the edges, or sides, of the teeth being straight 


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and parallel with the axis of the shaft on which the gear turns. In 
bevel gears the teeth taper toward a point and are inclined to the 
axis of the shaft. Another construction is the spiral gear. Both 
types may be made reversible and irreversible as desired. 

Worm-Gear Types. With a very few exceptions, automobile 
engineers favor the worm type of steering gear, and it will be found 
on the highest priced cars. It has the advantage of being irreversible 
and is utilized in several forms. In the worm class of gears, some types 
are closely related, while others vary widely. For example, the com- 
plete sector and gear type 
differ only in that the wheel 
operated by the worm makes 
a complete circle or part of 
a circle. The full gear can 
be turned through 90 degrees 
and replaced on the shaft 
without presenting a new 
surface to the worm. Some 
hold that the worm must be 
subject to some wear, espe- 
cially where it is most used. 
They contend that turning 
over the pinion brings new 
teeth to engage with the 
worm and that these teeth 
will not mesh properly when 
turned at an angle of from 
20 to 30 degrees. Fig * 322 ' Wor s ?eering P G r ^r al Gear Type of 

Worm and Partial Gear. 
Fig. 322 illustrates a gear of the worm and partial gear type. 
Advantages claimed for the design are durability, ease of action, 
and adjustability to wear. The parts are accurately cut and hard- 
ened, and the worm is provided with a ball thrust on either side. 
With this type, the teeth, which are in the middle of the sector 
and in mesh, perform the greatest work when the car is driven in 
a straight line and are most susceptible to wear. To compensate 
for this wear, the center teeth are cut on a slightly less pitch radius 
so that lost^ motion may be eliminated without affecting the upper 


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and lower teeth of the sector and to prevent binding when turning 
at right angles. In the illustration, A is the steering column to 
which the worm C is secured, D is the sector in mesh with the 
worm, E is the ball arm, or lever, B the gear housing, F the spark 
and throttle bevel gears and levers, and G the lubricant plug. 

Adjustment. Two principal adjustments are provided. End 
play of the worm is eliminated by loosening the jamb nuts and lock 
screws on the column housing. Displacing the oil plug G will dis- 
close an adjusting collar which is set with a screwdriver. Adjust 
collar until all play is eliminated, but the worm must turn easily. 
The lock screws, above referred to, are so located in the gear housing 
that when one is directly over a slot in the adjusting collar the other 
is between two slots. Consequently, after adjusting the collar it is 
essential that the proper screw be selected for locking the adjustment. 
Both locking members must be prevented from turning, by using the 
nuts. Wear of the teeth of the worm and sector may be eliminated 
by means of an eccentric bushing, which, when turned, moves the 
sector into a closer relation with the worm. This is accomplished by 
removing a locking screw at the left of the ball arm and moving 
the arm, which turns the eccentric bushing. In case of extreme wear, 
it may be necessary to displace the ball arm and set the locking-screw 
section in a different position on the end of the hexagonal end of the 
eccentric bushing so as to bring the arm in such a position that it can 
be locked by the screw. End play of the sector shaft is eliminated 
by removing a locking arm and turning an adjusting screw in, after 
which the arm and lock screw are replaced and both set up tight. 

Worm and Full Gear. A full gear and worm type of steering 
gear is shown in Fig. 323, with the gear cover removed. This type 
is irreversible, and the advantage claimed for it is that it can be easily 
removed and so readjusted that an unworn section of the gear may 
be brought into contact with the worm. This is a simple form, and 
it is possible to replace a worn gear with a new one, as the gears are 
not expensive. 

Fig. 324 shows a much more complicated form of worm and full 
gear in which the inventor has attempted to gain something by 
the use of a double steering gear, that is, two complete sets of worms 
and gears set opposing one another, the gears being made to mesh 
with each other just like a pair of spur gears. Since the lever can 


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be attached to but one of the turning gears, the other gear with 
its actuating worm is useless. The inventor doubtless intended 
the two worms to oppose each other and thus be self-sustaining as 
to thrust, but such would not be the case, the actual thrust being in 
opposite directions in the two cases of the upper and lower worms, 
the total thus being double the usual amount. 

Adjustment. The part most subject to wear is that section of 
the gear which meshes with the worm when the front wheels are 
traveling in approximately a straight line. Because of this wear, the 
teeth of the wheel are subject to deterioration. Usually the adjust- 

Fig. 323. Typical Worm and Full Gear Steering Device 

ment for the wear is made by bringing the worm into a closer relation- 
ship with the gear by using the eccentric bushings which support the 
worm shaft. This adjustment is practical when the lost motion is 
due to poor adjustment rather than to wear of the teeth. With the 
majority of types, it is possible to displace the steering arms, move 
the steering wheel about half a turn, then replace the worm wheel so 
that an unworn section opposite the worn teeth will be brought into 
engagement with a comparatively unworn portion of the worm 
proper. The eccentric bushings in this case can be utilized to obtain 
a correct meshing of the worm and gear teeth. End play of the worm 

103 Digitized by GOOC 



can be removed by adjusting the ball thrust bearings on either side 
of the worm. Sometimes these bearings become dry, or the lubri- 
cant becomes gummy, causing the shaft to turn hard. Wear of plain 
bushings in the steering-gear case is responsible for lost motion; the 
remedy is to replace the bushings with new members. 

Worm and Nut Next to the worm and gear, either full or 
partial, the form of steering gear most used is the worm and nut, 
which is made in several different combinations. Thus, the nut may 
operate the steering lever directly through the medium of a secondary 
lever, or it may actuate a block, which, in turn, moves either the 
lever direct or the secondary lever. In Fig. 325 another form of 

Fig. 324. Double Worm and Gear 
Steering Device 

Fig. 325. 

Worm and Nut Steering 

the worm and nut variety is shown. This has a nut which the turning 
of the worm moves up and down but which is split, the two halves 
being bolted together. A spherical seat is formed in the two 
halves of the split nut into which a ball-end lever is set, the bolt 
serving to clamp the two pieces together and hold the lever there. 
This is the end of the secondary lever, which is connected by 
means of another lever to the steering lever itself. In the figure, A 
is the worm, B and Bx the two parts of the nut, C the clamping 
bolt, and D the hinge at the other end. E and E x represent the 
spherical seats for the ball end of the other lever. 


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Having the nut in two widely separated parts reduces the wear 
on each, since the bearing surface is spread out more than would be 

JteAR V/ew J I S/0E View 

Fig. 326. Steering Gear Used on Heavy Manhattan Trucks 

the case with an uncut nut. In addition, the split nut allows the 
changing of the ball-end lever at any and all times. 


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Fig. 327. Section 
Gear of \ 

tl Details of Steering 
ftnton Cars 

Winton Motor Car Company, 
Cleveland, Ohio 

In Fig. 326 is shown a form of 
worm and nut steering gear which is 
used on very heavy trucks and com- 
merical cars. In this gear, the double 
worm is used; the inner worm carries, 
at its lower end, a block which is piv- 
oted in a combination lever and shaft, 
to which the steering arm is attached. 
In the figure, A is the hand wheel 
turning the rod B within the steering- 
post tube C. This rod is driven into 
and keyed at its lower end to a mem- 
ber D which has internal worm 
threads. Another member E has a 
circular upper end on which are worm 
threads, while its lower end is slotted. 
The worm at the upper end meshes 
with the internal worm threads in 
piece D, while the lower slotted end 
carries, between the two arms of the 
slot, a rectangular block F. This 
block is hardened and ground all over 
and is fastened to the forked end of 
piece E by means of the hardened and 
ground pin G. This pin also passes 
through the arm H of the shaft to 
which the steering arm is attached. 
The steering arm is free to rotate 
about the center. This rotation moves 
the steering lever L in the arm of "\ 

The steering action is as follows: 
Turning the hand wheel turns the 
outer worm. This worm cannot move, 
so the inner worm is forced to move 
up or down, as the case may be, and 
moves the block with the pin through 
it, which, being fixed in the arm 


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extension of the shaft, must turn the shaft. To this arm is attached 
the steering lever, so the latter must move. Although a rather com- 
plicated gear to explain and also to make, this gear, when finished, is 
an excellent one, and has been used for five or six years on heavy 
trucks with excellent results. 

The Winton steering gear, Fig. 327, is not decidedly different 
from the one just shown, as will be noted by a close inspection of the 
parts. A is the internal worm, which is turned by the hand wheel, 
while engaging this worm are the block B and pin C, the block being 
partly cut away to show the engaging gear teeth. This block moves 
the jaw arm of the steering lever D. This jaw is not complete in 
this gear, but is cut away to save weight. The jaw arm, too, is con- 
nected directly with the steering lever, the jaw, arm, and shaft making 
one piece. The light work to which this was put made possible the 
economy in the number of pieces and in the weight of each. As 
before, turning the hand wheel turns the worm, which, in turn, moves 
the block and pin up and down and thus moves the jaw arm, which 
moves the steering lever. 

Adjustment. The adjustment for lost motion in the worm and 
split-nut type of gear is generally made by loosening a cap screw on 
the column and screwing down an adjusting nut which has a right- 
hand thread. This adjusting nut acts directly on the thrust bearing, 
forcing the screw and half nuts, which slide, against the yoke rollers. 
In making the adjustment to a gear of this type, it is advisable to 
turn the road wheels to the extreme angle position, because the gear 
is the least worn at this point, and if it is adjusted only enough to 
take up the play when in this position, there will be danger of binding. 
Sometimes, when the adjustment is made with the road wheels straight, 
the gear will bind at the extreme positions. 

Worm and Worm. In the worm and worm form of steering gear 
there is a worm within a worm, not wholly unlike the ones just 
described. Fig. 328 shows an example of this, which has a worm C 
attached to the steering rod H, which is turned by the steering wheel 
A. Within and without this are worm threads, an external worm 
B meshing with the internal worm on the inside of C, while an internal 
worm D meshes with the external worm on C. The action of turn- 
ing the hand wheel, then, moves one of these upward and the other 


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The lower end B\ of the inner worm member presses against 
a hardened end of the steering-lever arm E, while the lower end Di 
of the outer worm member presses against the other hardened end 
Ei of the same piece. There is no lost motion, or play, in the gear; 
when the hand wheel is turned, one worm rises and the other falls, 
as just described; the piece E will let one end rise and the other fall, 
as it is acted upon by the lower extremities of the two moving worms. 
This piece is pivoted at F and carries at its outer end the steering 
lever G, which thus moves in the customary manner. Within the 
steering post are the spark and throttle tube and rod / and J, which 

Fig. 328. Section of Gemmer Steering Gear 
Courtesy of Gemmer Gear Company, Detroit, Michigan 

carry right through the whole gear and out at the bottom, where 
the spark and throttle-actuating levers are attached. 

Adjustment. The adjustment of the worm and worm type, an 
example of which is illustrated in Fig. 328, is generally effected by a 
nut located at the upper end of the gear housing. This nut is pro- 
vided with flats to accommodate a wrench hold. The end of the 
worm-wheel shaft is squared, and to this square the steering-lever 
arms are attached by means of a pinch clamp and bolt. 

Bevel Pinion and Sector. Among the other types of steering 
gears is that of the bevel pinion arid sector, shown in Fig. 329. The 


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bevel pinion moves the bevel-gear sector back and forth as it is turned, 
this motion being transferred to the steering arm attached on the 
same shaft to which the bevel sector is secured. This type of gear is 
said to be effective, but it is not irreversible, and shocks to the road 
wheels may be imparted to the steering wheel and move it. 

Fig. 329. Bevel Pinion and Sector Type of Steering Gear 
Courtesy of Reo Motor Car Company, Lansing, Michigan 

Adjustment. The bevel and sector gear has two adjustments. 
The pinion may be moved up or down, as required, by unlocking the 
clamp bolts (one of which is shown at D) which permits the moving of 
the entire steering column up or down so as to obtain the proper 


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relative position to the pinion and its sector. The position of the 
sector endwise may be adjusted by the block member A, which bears 
against a roller guide, forcing the sector into mesh more or less closely 
with the pinion. The spring E is provided to prevent rattling, and 
the screw If is a guide for the plunger and should not be disturbed 
in making the adjustment. 

Hindley Worm Gear. There are a number of things about the 
Hindley type of worm which make it an excellent one to use for 
steering gears. A realization of this advantage is bringing about a 
greatly increased use of this form; so it will be appropriate and timely 

to look into its form, con- 
struction, and advantages. 

The question of what 
makes the Hindley different 
from other worms naturally 
arises. The ordinary worm 
has the same diameter from 
one end to the other, the 
blank before the cutting of 
the teeth resembling a sec- 
tion of a cylinder. The Hind- 
ley, on the other hand, is not 
of uniform diameter, but has 
a smaller center diameter and 
enlarged ends. This gives it 

Fig. 330. Details of the Hindley Worm ft ^j^ or hour . glass> shape . 

An illustration will make this clear. Fig. 330 shows at A how 
the Hindley shape is generated and at B a finished gear, revealing 
plainly the reduced center diameter. In the upper figure, EE is the 
center line, or axis, of the worm, and the center of the gear which 
is to mesh with it. CD is a circular arc struck from as a center. 
If, on this curve CD, equal spaces be struck off, using a distance equal 
to the pitch of a single-threaded worm or the lead of a multiple- 
threaded one, as at F, and radial lines be drawn from the center 
to these points, these lines will be normal to the surface of the worm at 
those points; in short, the worm must pass through them, as roughly 
sketched in the figure. In the lower part B, of the figure, is illustrated 
a worm made on this principle, ready to be put into position. 


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This form of worm is used for the double reason of presenting 
more wearing surface — since it has at least three teeth in contact 
at any one time, as compared with one or at most two in the 
ordinary worm — and greater resistance to reversibility. The worm 
is used for steering gears because it is partly or wholly irreversible, 
its motion being a sliding one; nevertheless, all worms may be 
so cut as to be either wholly or not at all reversible. The sliding 
motion of the two parts in contact, as opposed to the rolling motion 
in the case of other mechanical movements of a similar nature, is 
greatly increased if there are three teeth in contact instead of the 
more usual one. If the friction of sliding be increased, the amount 
of reversibility will be decreased in the same proportion, for the added 
sliding friction will increase the natural reluctance of the worm to 
transmit power backwards. So much is this the case that it pays 
to use the Hindley form, despite its greatly increased cost of cutting. 

Ford Steering Gear. The steering mechanism of the Ford car — 
a patented construction — differs radically from the conventional 
types in that its hand wheel does not directly rotate, or turn, the steer- 
ing column or rod, but it imparts the necessary turning movement 
through the gearing and the use of a small shaft to which the hand 
wheel is attached. A phantom view of the gearing is shown in Fig. 331 . 

The steering column with its short shaft and drive pinion is 
enclosed in a tube or housing which is set at an angle and bolted to 
the dash. The housing does not extend the entire length of the 
column, as the lower end of it is mounted in a bracket that is rigidly 
bolted to the frame. The steering-gear post, or column, has a tri- 
angular flange at right angles to the rod, and each point of the flange 
has an integral stub, or pin, carrying a small spur pinion. The center 
of the rod is drilled and bushed to take a small shaft to which a fourth 
pinion, or drive pinion, is keyed. The upper part of the housing is 
shaped so as to provide a gear case, and the inner periphery of this 
case is cut to obtain spur teeth or, in other words, an internal ring 
gear. This gear is stationary. 

The hand wheel is attached to the short shaft, and its drive 
pinion is held in place by a brass cover of the internal gear case. As 
the drive pinion of the shaft is in mesh with the three pinions mounted 
on the stubs of the steering column proper,, and these three pinions 
are in mesh with the internal ring gear, any movement of the -hand 


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wheel will rotate the drive pinion on its shaft. This movement will 
cause the three spur pinions to rotate in an opposite direction against 
the internal gear, thus reducing the movement of the steering column 
as compared to that of the hand wheel. The three spur pinions 
compensate for any pressure of the drag link and the tie rod. 

The operation of the Ford steering-gear mechanism explains the 
basic principle of the operation of the hand wheel; that is why the 
wheel is turned in the same direction that the driver desires the car to 

-JHrer//rp Post 
Fig. 331. Ford Planetary Steering Gear — An Unconventional Type 

go. If the hand wheel is revolved from left to right, for example, the 
movement causes the three pinions mounted on the pins of the steering 
column to rotate from right to left; the pinions rotating against the 
stationary internal gear turn the steering rod in the same direction 
taken by the three pinions. The column swings an arm attached to 
it from right to left, and, as the rod is secured to this arm, it moves 
in the same direction, swinging the front road wheels so that they 
move from left to right, and to a degree that will correspond with the 
turning, or movement, of the hand wheel. It should be understood 
that the movement from left to right refers to the front half of the 
road wheels. If the driver desires to direct the vehicle to the left, 
the wheel is turned to the left. 


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The drag link of the Ford steering gear differs from conventional 
designs in that it is at right angles to the frame and is practically 
two-thirds the length of the tie rod.„ The end of the steering column 
is provided with an arm carrying a ball, and the drag link, or steering- 
gear connecting rod, as it is listed by Ford, has a ball-socket 
cap which fits over the ball of the steering rod. The drag link also 
has a ball socket at its other end, which fits over a ball arm on the tie 
rod. The tie rod, called the spindle connecting rod because it con- 
nects the spindles, is provided with yokes at either end, and these 
yokes are pivotally connected to the spindles by a bolt passing 
through them and 
through an eye in the 
spindle. The Ford drag 
link differs from others 
in usual practice in that 
it moves to the right and 
left, while those used on 
other cars move forward 
and backward. No pro- 
vision is made with the 
Ford drag link for absorb- 
ing shocks or for auto- 
matically compensating 
for wear as usually is the 
case with the conven- 
tional type of drag link. 

Semi-Reversible Gear. The steering gear used on commercial 
cars, particularly trucks ranging from 3- to 7-ton capacity, must not 
only be capable of operation with a minimum effort, but it must 
absorb a great many of the minor shocks and a per cent of the larger 
shocks. The semi-irreversible type is most favored because of the 
above-named reasons. The design shown in Fig. 332 is of the screw 
and nut type. The nut is a solid piece, completely enveloping the 
screw, and the threads of the screw are in constant and complete 
engagement with the threads in the nut. The screw has a rotary 
motion and the nut has a longitudinal motion. The means of trans- 
mitting this longitudinal motion of the nut to the rotary motion of 
the steering arm is by circular discs at the lower end of the nut. 

Fig. 332. Screw and Nut Gear Used on Trucks 


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These discs present constant bearing surfaces to the recesses in the 
nut, and are provided with slots into which the projecting levers from 
the rocker shaft fit. The screw pulls the nut up or down in the 
housing, and there is no tendency for this nut to be moved sideways. 

Fig. 333. Worm and Gear Steering Arrangement — Semi-Reversible 

The levers projecting from the rocker shaft into the swivels which 
rotate in the lower part of the nut are in direct line with the screw, 
so that the push and pull of the nut is in a straight line. 

Removing Steering Gear. To disassemble the majority of 
steering gears it is necessary to remove the unit. With the type shown 


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in Fig. 333, which, is a semi-irreversible worm and gear, the removal 
may be accomplished by displacing the control levers at the top of 
the column and dropping the unit down through the frame. The 
adjustment of this type for end play is made by loosening the locking 
nut A and turning down the nut B until the play is eliminated. 


Lost Motion and Backlash. Lost motion of the steering wheel 
does not always indicate that the steering gear is at fault, for wear in 
the steering-gear assembly usually takes place first in the clevis pins, 
yokes, and connections of the drag link. The spindles, spindle bolts, 
and wheel bearings are factors. Despite the fact that the front road 
wheels are deflected but a few degrees the spindles, bolts, or bushings 
may be worn, as these parts are subject to radial and thrust loads. 
The spindle bolt, which does not move, tends to wear oval; adding to 
this tendency the wear of the spindle bushings, one has considerable 
lost motion to contend with. Wear of the wheel bearings contributes 
to the apparent lost motion of the steering gear as do the connections 
of the drag link. Taking all of these factors into consideration, and 
allowing but a small fraction of an inch for play of each worn part, 
the sum total may result in considerable movement of the hand wheel 
before the road wheels are deflected. 

Lost Motion in Wheel. While there should be a certain amount 
of movement to the hand wheel before it actuates the road wheels, 
the lost motion, as a mle, does not exceed \ or f inch when the gear 
is new. This amount is essential as without some free movement the 
steering of the vehicle would be tiresome. Wheels may be keyed or 
pinned to the column. When play exists as the result of a worn key, 
pin, or slots, the remedy is to re-cut the seats and make and fit a new 
key or pin. With some types of wheels the use of a wheel puller will 
be necessary to displace them. Another cause of lost motion, when 
the wheel is tight and linkage free from play, is a loose key retaining the 
worm or gears of the steering gear proper. A simple test of the hand 
wheel is to hold the tube, or post, securely and move the hand wheel. 
The amount of play in the drag link can be ascertained by grasping 
it about midway and trying to move it backward or forward or in the 
normal direction of travel. Hold the ball arm of the steering gear 
when making this test. 


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The amount of backlash present in the irreversible and semi- 
irreversible types of steering gears may be determined by disconnect- 
ing the drag link, grasping the ball arm, and moving it up and down 
and back and forth. Worn bushings in the steering-gear case are 
frequently the cause of movement of the column as a whole. Another 
component that should not be overlooked in the search for the cause 
of lost motion is the ball arm. Movement of this member on its 
shaft can usually be eliminated by tightening the nut. 


Different Forms of Hand Wheels. Wood Rim. A variety of 
material is utilized in the construction of the wheel, which has super- 

Fig. 334. Section through Typical Steering Wheel 

seded the lever or tiller. The section or sections of the wheel or rim 
are circular, oval, or elliptical; the oval, or ellipse, is turned upward. 
The strength of the wheel varies according to the material used and 
the process of assembly. The all wood wheel has not the strength of 
a built-up wheel with a metal core, but it is simpler and cheaper to 
manufacture. With the exception of the molded rubber type of 
rim, the majority of the wheels, particularly those fitted to high- 
grade cars, are built-up. Mahogany, Circassian walnut, and black 
walnut are the materials favored. The wood is cut to short sectors 
of an annular ring of about 2 inches in width and so glued together 
as to eliminate joints. 

The method of attaching the rim to the spokes of the wheel 
spider is by screws, and this method is illustrated in Fig. 334. A 


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indicates the wood member, B the arms, or spokes, which have a 
boss through which the screw C passes into the wood. The hub of 
the spider D is attached to the steering post by two keys E. 

Metal Core with Wood Covering. When the wheel design is made 
up of a metal core the ring is cast on the spider or integral with it. 
Coverings of wood concealing the ring are used, although with some 
types, a section of the ring may be noted. This type of wheel pos- 
sesses great strength and the wood veneers can be secured at more 
frequent intervals than in the design previously described. 

Different Wheels for Commercial Use. Truck Types. For the 
light delivery wagon, taxicab, and similar cars, no difference in the 
steering wheel is made, but when it comes to the heavier service, there 
is a need for a heavier wheel. This does not mean a heavier rim 
only, but a heavier, more rugged gear all the way through. The 
weight on the front wheels of a heavy truck is very great, and 
the tires, which are of solid rubber, may have frictional contact with 
the pavement of several inches in width. All this combines to make 
turning the vehicle from the driver's seat more difficult. 

For this reason the driver must have a greater leverage, which 
means a larger diameter of the wheel. Then, too, the rim should be 
bigger in section in order to withstand the harder use of commercial 
service, and to provide for the large hands of the operators. Greater 
strain upon the rim of the wheel, on attempting to turn heavier 
weights with it, means that the rim must be fastened to the spider more 
securely. This means more arms, the four generally used for pleasure 
cars being increased to five for trucks. While this helps a great 
deal; since it provides five screws instead of four, it is not sufficient, 
and most of the big trucks today are equipped with steering wheels 
in which the rim is built over a central metal rim of the spider. 

Pleasure-Car Types. Usual pleasure-car practice varies from 
14-inch up to 16-inch wheels, while commercial car sizes begin at 16- 
inch and run up to 18-inch wheels on light trucks, and as high as 20- 
and 22-inch wheels on heavy trucks. Rim sizes vary considerably, a 
favorite for touring cars being an oval with from f - to f -inch vertical 
height and a length of about l^fr to 1^- inches. These figures have no 
connection with commercial work, the smallest being l.inch and on 
up to 1 1 inches in height, with the long diameters varying from 1$ up 
to If inches. For speed work, racing, and the like, it is usual practice 


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for the operator to wind the surface of the wheel with string, this 
giving a rough surface upon which the 'hands will not slip. This is 
practiced, too, by many truck drivers, who claim that the strains of 
steering the big vehicle are not felt as much when the wheel is thus 

To preserve the nice appearance of the steering wheel and still 

Fig. 335. Knotted Wood Rim as Used on the Oldsmobile 

give the roughened surface to which the hands will cling easily, even 
in wet weather, many manufacturers are making a wheel of knotted 
wood, the use of this material allowing the formation of the wheel 
in any desired section, as is seen in Fig. 335. As a concession to 
appearances, these wheels are usually made with a plain upper surface ; 
the lower or under surface, however, being made in a series of depres- 


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sions and humps, between which the fingers find a good resting place. 
This gives a good grip, as the under side of the wheel seldom gets wet. 
Folding Steering Wheels. Although tilting steering wheels were 
introduced several years ago, they did not meet with favor until the 
Cadillac adopted them as standard equipment. The wheel, which is 
18 inches in diameter and has an aluminum spider, is hinged to drop 
downward, a design facilitating entrance and exit at either side of the 
car and making it possible to attain the driver's seat without squeez- 

Fig. 336. Hinge Type of Steering Wheel Used on Cadillac 

ing. The Cadillac wheel is shown in Fig. 336, while that used on the 
King car, illustrated in Fig. 337, is of the tilting type. To operate 
the design, the wheel is turned until the wheel spider arm carrying 
the release button is convenient to the thumb of the right hand. 
The button is pushed to the right, and, by using both hands, the 
wheel is pushed forward and upward. The Herff type, shown in 
Fig. 338, is of the true hinged form; the rim is thrown up and out of 
the way, that is, the rim only, as the quadrant carrying the spark and* 





Fig. 337. 

Tilting Steering Wheel on the 

I Car 

throttle levers remains. There are several other types marketed, but 
their working principles are similar. 

Throttle and Spark Levers. In the usual case, the arms of 

the steering wheel have the 
quadrant for the spark and throt- 
tle levers fastened to them. The 
levers are operated within the 
space inside of the rim of wood 
and above the spider of metal; 
the latter is usually at a lower 
level by several inches, as shown 
in the figure. In Fig. 334, how- 
ever, the quadrant is not carried 
by the spider arms, but on a sep- 
arate framework G, or spider of 
its own, up above the hub of the 
wheel. Over this frame- 
work the spark and throt- 
tle levers H and I work, 
serrations of teeth in the 
quadrant preventing 
the levers from moving, 
except when they are 
sprung off by the pressure 
of the fingers operating 
them. In some cases, 
these teeth are done away 
with and friction surfaces 
are substituted; springs 

Fig. 338. Herff-Brooks Folding Steering Wheel holding the Contact SUT- 

faces together are so light as not to interfere with the moving of 
the levers by hand. 


Operation. By the steering rod, or drag link, is meant the 
member connecting the ball arm, or lever, of the steering gear to 
the lever attached to the steering knuckle. This is clearly illustrated 
in Fig. 339. The steering gear is marked D, the steering arm pro- 


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jecting down from it C, while the steering rod which connects the 
lower end of the arm with the lever on the knuckle is marked AB. 
F is the knuckle pivoted in the axle, which carries the two-end lever 
E, one arm of which has the steering rod attached to it at B, while 
the other carries the cross-connecting rod joining the two knuckles 
together. Since the pivot point is fixed, any movement imparted to 
the knuckle must result in its swinging about the pivot point and 
carrying the wheels with it. 

This movement is imparted by the steering rod to the end B 
of the arm E. The stearin? rod itself simnlv 

Fig. 339. Typical Steering Arrangement on Pleasure Car 

a constant level, although moving in a circle, the rod must have a 
universal joint at one end. This is really a necessity from two points 
of view: to allow the rear end to move up and down vertically while 
the front end swings around in a circle; and also to allow the front 
end to swing in a circle set in one horizontal plane, while the rear end 
remains stationary or practically so in that plane. In short, the two 
ends move continuously, each in its own plane, but the two 
planes never coincide — the one is always vertical, while the other 
always stays horizontal. This necessitates at least one universal 
joint. Many makers play on the safe side, and lower the cost of 

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production by making the two ends alike — a universal joint on 
each one. 

Types of Construction. A glance at the construction shown in 
Fig. 340, and also in Fig. 341, shows a steering lever made with 
a ball end, or partial ball end, upon which the steering rod is 
hung. In this, the, partial ball is formed in the center of a bar, the 
inner end of which is threaded and screwed into the steering arm, 
with a nut on the outside to prevent its backing out. The ball 
itself is made separately and slid on over the rounded end of the 
shaft, or axis. After this a sleeve is put on, followed by a nut which 
holds the sleeve up tight against the ball. The function of the sleeve 
is to give the spherical end of the rod plenty of play in a sidewise 

direction. This is a cheap form of con- 
struction, but could have been made in 
one piece had it been desirable or neces- 
sary to do so. Such a form has a metal- 
to-metal contact, which is hard upon both 
ball and socket, necessitating frequent and 
costly replacements. These replacements 
are obviated by backing the ball socket 
up with a spring or springs, as is shown 
in Fig. 341. This form of construction 
is now quite generally used; the socket of 
the ball in the inner end of the rod is set 
inside of a sleeve with a spring on each 
side of it. These springs not only take up the road shocks but the 
wear as well, the shoulder against which they rest being adjustable. 
In this figure, J is the lower end of the steering lever with the ball 
end. This lever is mounted in the ball socket G. A is the body of 
the steering rod, which is expanded at the end to a larger diameter, 
this being designated in the figure as B. Within this expanded 
portion, the sleeve E at one end acts as a shoulder for the spring F. 
At the other end, the outside of the sleeve is threaded to receive 
the collar C with the hexagon end K. Within this, a second spring 
L holds the socket up to its position. The location of the collar C 
determines the tension of the spring L, and this is locked in its 
position by the screw V. Should there be wear, which necessitates 
the moving of the ball toward the open, or left, end, the whole thing 

Fig. 340. Steering Lever with 
Ball End 


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is disassembled and a longer sleeve inserted in place of the one shown 
at E. On the other hand, ordinary wear is compensated for by 
taking up on the collar C, first loosening the lock screw V. 

In Fig. 342, a rod is shown assembled at the top and disassembled 
into its components at the bottom. The two ends differ, one being 

Fig. 341. Adjustable Form of Ball-End Steering Rod 

but a simple yoke with a plain bolt through it, marked D. 


other, however, is a ball end with an adjustment and with springs 
to take up shocks. 

All these parts are marked in the figure and may be located by 
letter. The body of the rod is marked A, the expanded end B, which 
has a groove H cut in it. Into the inner end of this groove is fitted, 
first, the spring F; second, the two halves of the ball socket G; and 


Fig. 342. Cross-Connecting Rod Assembled and in Parts 

third, another spring. The sleeve E closes the outer end, and over 
the exterior is screwed the adjusting nut C. The nut and sleeve are 
held in place by the locking pin V, which passes through the 
outer nut, the shell end of the rod, and the inner spacing sleeve, the 
ends being riveted over to hold it in place. This form limits the adjust- 


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ment to a full half turn of the nut, while the pin would soon need 
replacement if much adjusting were done, as some of its length would 
be lost each time it was riveted over because of the chipping away 
to allow it to be taken out. 

Cross-Connecting, or Tie, Rods. The object of the cross- 
connecting, or tie, rod is to connect the right- and left-hand steering 
knuckles so that the road wheels will be turned alike. The general 
practice is to place the rod back of the front axle, a location avoiding 
the possibility of damage if an obstruction in the road is encountered, 
but in some instances the tie rod is placed in front, as in Fig. 339. 

Fig. 343. Finished S.G .V. Chrome Nickel-Steel Steering Knuckle and the Same 
before Machining 

Fig. 344. Left Steering Knuckle of S.G.V. Car before and after Machining 

The tie rod is made adjustable to compensate for any change 
that may be necessary to preserve the alignment of the wheels, and, 
generally, the rod is adjustable at either end. The yoke ends of the 
rods are made adjustable, screwing on or into the rod proper and 
secured by lock nuts or other suitable fasteners. The adjustment is 
easily made. Decreasing the length of the rod increases the gather, 
or distance, between the forward section of the front wheels, while 
increasing it causes the wheels to toe in. This applies to the tie rod 
behind the axle. 


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Function and Shape of Steering Knuckles. The steering knuckles 
serve as a pivot for the road wheels, enabling them to move in a hori- 
zontal plane. The design of the knuckle depends upon the axle, and 
the pair used on a car are different as one has a lever for carrying the 
drag link. Both have integral spindles to which the tie rod is attached. 
Figs. 343 and 344 illustrate the difference between the knuckles. 

Fig. 345. Packard Steering Gear Parts 

Fig. 343 shows a right knuckle, forged from a blank of chrome nickel 
steel, while the one at its side is the finished part. A is the place 
for the outer wheel bearing, B the position of the inner bearing, C the 
hole for the pivot, or knuckle, pin, D the upturned steering arm, and 
E the arm to which the tie rod is attached. Fig. 344 is an example 
of a left steering knuckle of the same pair, both before and after 
machining. The letters in Fig. 343 apply to this knuckle. 


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Lubrication of Steering-Gear Assembly. The proper lubrication 
of the steering-gear assembly adds to its life, but this work is not, as 
a rule, thorough. The steering gear proper should be packed with 
grease, the ball and socket joints of the drag link and steering-arm 
lever with a light grease; the clevis pins also should be lubricated. 
The steering-knuckle pins are provided with either grease or oil cups. 
A point generally overlooked in the lubrication of the steering 
gear is the steering-post spark shaft and throttle-sector anchor tube, 
shown in the illustration at Fig. 345, which is of interest in that 
it illustrates the assembly of the Packard car. The post carries 

the control-box unit. The 
spark shaft and throttle tube 
frequently lack lubricant and 
should be cleaned and coated 
with a graphite grease before 
replacing when the gear is 
being reassembled. The lower 
extremity of the spark and 
throttle members carry levers 
or small bevel sectors which 
operate the linkage of the igni- 
tion apparatus and carburetor. 
Clamping screws are generally 
used to secure these parts. 

Front=Wheel Drive. In 

Fig. 346. Front Drive and Steer on Homer the Conventional type of 

Laughhn Car v ^ 

pleasure motor car, the energy 
of the engine is applied to the rear wheels which propel the car, the 
drive being a pushing one. A pleasure car, or rather a racing machine, 
with a front-wheel drive — which is a pull, and held by some to be more 
economical — was brought out several years ago but not marketed. 
During the latter part of 1916, a company was formed to market an 
eight-cylinder pleasure vehicle, utilizing a front-wheel drive and steer 
and a friction drive with an automatic pressure control. 

Difficulties of Transmission. The Homer Laughlin car, a bottom 
view of which is shown in Fig 346, made use of an original type of 


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universal joint to transmit uniform angular velocity. Its design was 
brought about by the fact that the rate of transmission of angular 
velocity through ^t universal joint is not even when the shafts are at 
an angle. This is the fundamental difficulty every designer of a front 
drive has to overcome or suffer the twisting of the axle. 

The front wheels and the flywheel must rotate at practically a 
uniform speed, at least through each revolution. The irregular rate 
of transmission through the universal joint must be taken up some- 

Fig. 347. Homer Laughlin Pedal Mechanism 

where. The normal action of a universal joint at certain angles is 
to make four jerks in a revolution, as it has four fast points and four 
slow points. The Laughlin joint gives uniformity of rotation with 
75 per cent on each side of normal*, the difference being taken up by 
the flexibility of the transmission parts. 

Friction-Disc Transmission. The transmission is of the friction- 
disc type, but the disadvantage of this form of drive — the fact that 
the control is reversed — is eliminated. The usual clutch control is 
provided, but the pressure is automatic. This pressure is obtained 
by an eccentric connection by means of which designers obtain irre- 


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versible application of spring pressure. The transmission locks at the 
correct pressure through the friction of the eccentric. The spring 
controlling the friction for driving provides the proper pressure for 
running, but it is not sufficient for starting or climbing long hills in 
the low gear. The pedal shaft operates a dog that presses down on 
the eccentric sheave extension. To de-clutch, the operator presses 
the pedal down, releasing the clutch. The pedal has two points at 
which it latches, providing extra pressure, and an extra spring is 
brought into service for the high and low speed. This spring operates 
through a toggle linkage. As the pedal rises, the applied power 
increases. When the car attains momentum, the driver depresses 
the pedal until it latches. The running pressure is sufficient to hold 
the engine in all gears except the low and reverse. 

Control. Complete control is obtained through one gearshaft, 
the lever working forward for progressive, and back for reverse. Auto- 
matic latching is obtained in every gear, the latch working in sockets 
sunk in the jackshaft. Chain drive is employed between the trans- 
mission and front axle. The brakes are located on the rear axle. 
Fig. 347 shows the method of obtaining a conventional pedal control 
of the transmission through the irreversible application of spring 
pressure — one spring for ordinary service, the other for low gear work — 
controlled by the eccentric on the jackshaft of the driving mechanism. 

Four-Wheel Driving, Steering, and Braking. The four-wheel 
drive — a construction in which all four wheels of the vehicle drive, 
and frequently steer and brake — is confined to commercial vehicles. 
A brief consideration of the actions which may have to take place at 
the same time in such an axle will give a very good idea of the problem 
which must be worked out. The wheels must be free to turn about 
the axle as an axis, being driven from their hollow centers; the wheels 
must also be free to turn about the pivot point as an axis swinging in 
a horizontal direction and must be driven steadily all the time. 
All the turning, swinging, and driving action must be outside of 
and beyond the spring supports of the chassis, since the body cannot 
turn; but the axles must at the same time support the springs. 
Further, if all four wheels are to carry brakes, they must be appli- 
cable at any and all times and at any and all angles of inclination of 
the wheels, either in a vertical or horizontal direction, and they must 
be so equalized as to apply equally to all wheels, no matter how the 


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force is applied to the system, and no matter in what position the 
wheels may be. 

The advantage of the four-wheel drive and with it the four- 
wheel steer and brake is granted by eminent engineers, as is also its 

Fig. 348. Side View of a Four-Wheel Drive, Steer, and Brake Motor Truck 

necessity for heavy commercial trucks, but its use lias not been 
extensive for the simple reason that it is a complicated arrangement 
at best. In many cases, the design has been so complicated and 
unmechanical as to cause failure, and the reports of these troubles have 
given the four-wheel driving, steering, and braking device a sort of 
visionary air, so that any one talking of it is supposed to be a dreamer. 
Such is not necessarily the case, for many different practical four- 
wheel combination driving, steering, and braking devices have been 
brought out, built, tested, and proved efficient. 

A number of four-wheel designs for commercial cars are being 
marketed, and have proved the contention of their makers that they 
are economical in operation and maintenance. 

Four- Wheel Steering Arrangement. With the design shown at 
Fig. 348, steering knuckles are eliminated, the wheels being con- 

Fig. 349. Details of Axle of the Four-Wheel Drive Truck Shown in Fig. 348. 

nected to the axle ends through the medium of vertical trunnions. 
These trunnions bear on the wheel ball-bearing ring/ which is ample 
in diameter and turns freely because of its size and the use of ball 


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bearings. Within this ring, the axle terminates in what is practically 
a universal joint/driving through to the outside of the wheels. The 
wheels are thus free to run about a point in the axle ends, at the same 
time taking their power through the inside rotating shaft. Fig. 349 
illustrates one of these axles with the parts lettered. Here H is the 
point of attachment of the driving propeller shaft, G the cast-steel 
one-piece case, F the differential gear within the large driven bevel 
gear 0, MM the vertical trunnions upon which the wheels rotate, and 
NN the universal joints which drive the wheels. 

How the steering is obtained is shown in Fig. 350. At the front 
of the chassis is the steering wheel P; turning it partially rotates the 
longitudinal shaft Q, which extends the length of the chassis. This 
shaft carries levers RR near its two ends, which are connected to 

Fig. 350. Diagram Showing Steering Action of a Four-Wheel Drive Truck 

the steering rods SS. These rods connect to the steering levers U U, 
which are fixed to the wheels themselves instead of to the steering 
knuckles as in the ordinary case, for this car has no steering knuckles. 
In addition to the steering rods attached to the longer of the two steer- 
ing levers, there is a cross-connecting rod TT at each end, which con- 
nects the two steering levers. Thus, when the levers RR move the 
rods SS, and through these the levers UU, which in turn move 
the wheels VV, the rods TT also come into play and move the 
levers WW and the wheels XX. Therefore, the movement of the 
steering wheel in any given direction, as to the right, turns all four 
wheels, the front two to the right, and the rear two to the left so 
that they form arcs of the circle in which the front ones are turning. 
The truck thus makes the desired turn to the rig 1 ^ in one-half the 


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distance or time of the ordinary 
truck. Four-wheel steering then 
has the advantage over two- 
wheel, or ordinary, steering, of 
requiring only one-half the space 
and one-half the time to accom- 
plish a given turn. The vehicle 
described would turn completely 
around in a circle of 40 feet, the 
outermost circle shown in Fig. 
350 being 56 feet in diameter. 

Chain Four-Wheel Drive. 
Fig. 351 clearly illustrates a bot- 
tom view of the Hoadley four- 
wheel drive, four-wheel steer, and 
four-wheel brake truck. The 
power of the engine is trans- 
mitted through shafts, gears, and 
universal joints to the differen- 
tials; there is a third differential 
in the gear box at the center of 
the frame. Final drive is by 
chain; both ends of the truck are 
exactly alike in so far as the four- 
wheel drive is concerned, and the 
fifth wheels run in ball bearings. 
Steering is accomplished by means 
of worm gearing, the shaft being 
clearly shown, and both sets of 
wheels are steered simultaneously. 

Jeffery Quad. An example 
of the successful development of 
the four-wheel drive is the Jeffery 
Quad, Fig. 352, which has given 
an excellent account of itself in 
government work. In this type 
it will be noted that the inclined 
driving shafts, shown in Fig. 348, 


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have been carried up to the gear box with a universal joint on either 
side. This construction has resulted in a much more inclined shaft 
in each case, but it has also eliminated the tail shaft D, the use of a 
silent chain E with its housing, the central universal joint, and the 
spherical bearing K, and, in addition, it has simplified both shafts. 
In the four-wheel drive vehicle the engine was placed on the 
center line of the car; on the Jeffery it is set off to one side, while the 
two driving shafts to the front and rear axle, which form a continua- 
tion of each other, are set off to the other side. This result is produced 
by making the transmission very wide with three side-by-side shafts, 
as shown in Fig. 353. The engine drives the splined shaft H, on which 
are gears that transmit the rotation to the intermediate shaft C, which 
through the final gears E and F, drives the final shaft, which is in two 

Fig. 352. Plan View of the Jeffery Quad, Showing Disposition of Units 
Courtesy of Thos. B. Jeffery Company, Kenosha, Wisconsin 

parts, B driving one pair of wheels, G driving the other pair. Note 
that the differential has been incorporated in this type of drive, 
so that it is possible to have a different drive for the front wheels 
from that for the rear wheels. 

The rest of the construction is too simple to require a detailed 
description beyond the simple statement that the gear box gives four 
forward speeds and one reverse. When the two ordinary shifters 
are in the neutral position shown, reverse is produced by shifting 
the double reverse gear on shaft D along until its left-hand member 
meshes with the second-speed gear on shaft A and its right-hand 
member with the low-speed gear on shaft C. 

Universal joints fit on the two tapers B and C with shafts 
inclined to the two axles. On top of the stationary axle of the I-beam 



section is fixed a small box which contains the bevel gears and an 
additional differential with suitable bearings, the whole being 
enclosed. These can be seen in Fig. 352, that on the rear axle being 

Fig. 353. Plan View of the Transmission of the Jeffery Quad, Showing the Shafts for Both Axles 

plainly shown, while the one in front is partly obscured. This 
member is shown in detail in Fig. 354, which gives the longitudinal 
section along the driving shaft at the left, in which the axle H is 
noted, the bevel gear 7, and the bearings for radial and thrust loads 

Fig. 354. Sections Showing Bevel Drives at the Axles on Jeffery Quad 

at J and K, respectively. The driven shaft is seen at L, with the 
sleeve M around it, the sleeve being used to drive to the differential 
case, since the larger, or driven, bevel C is not sufficiently large to 
house the differential P. 

138 Digitized by GOOgk / 



Fig. 355 is a diagram showing the details of the axle end and 
wheel construction. In this, H is the I-beam section of the axle bed 
shown in Fig. 352, and N one of the shafts, which carries at its 
end the universal joint Q, with the end of the shaft extending beyond 
the joint R. The latter carries the spur gear S, which meshes with 

Fig. 355. 

Section through a Wheel and Axle End of the Jeffery Quad, Showing 
Method of Driving and Steering 

the internal gear T fixed to the wheel and drives the vehicle in this 
manner. It will be remembered that this is not necessarily a front 
wheel, but any one of the four. 

The wheel turns on the spindle U, which is part of the steering 
knuckle V; this knuckle turns upon the pivot W. The lever which 


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turns the wheel is attached at X, the pair (either both front or both 
rear wheels) being connected by means of a cross-rod; at one end of 
this rod there is a connection to a rod which runs the entire length 
of the chassis. This rod is operated by means of the steering gear, 
and imparts the same motion to the front wheels as to the rear, 
except that the two are in opposite directions, that is, front wheels 
turn to the left and rear wheels to the right, so that they will follow 
around in a correct circle. 

Advantages of Four-Wheel Drive. It is claimed for the four-wheel 
drive that its four-wheel steering reduces the mileage traveled to the 
minimum in that the car can run closely to corners and travels less in 
crowded traffic, in turning around, and in approaching and leaving 
loading platforms. The push of the rear wheels and pull of the fronj; 
wheels enables it to surmount obstacles instead of bumping over 
them, and its greater traction permits it to travel soft roads not 
easily negotiated by the rear-drive type of trucks and cars. The 
four-wheel drive type will turn in a 48-foot circle, and, with its lock- 
ing differential, obtains traction on slippery roads. 

Electric Drive. When the final drive is electric, or when the 
source of power is an electric motor, the matter of four-wheel driving 
is much simplified, the wheel carrying the electric motor attached 
directly to it and turning with it about the knuckle pin. Both 
wheel and motor are turned by means of a worm and gear above, the 
wheel being attached to the upper end of the steering-knuckle pin 
prolonged. Turning this turns the wheel and motor. . 

This steering wheel is turned by the worm, which is on one end 
of a cross-shaft. This shaft is carried in bearings above the stationary 
bed of the axle and has near the center a bevel gear that meshes 
with another bevel, which is, in turn, attached to the lower end of the 
steering post. Turning the steering wheel turns the post and the 
bevel gear, which turns the bevel pinion and with it the worm shaft. 
The shaft turns the worm and the worm wheel which actuates the 
road wheels. The driver thus has a triple reduction between himself 
and the wheels, giving him this much advantage in steering: there is 
the leverage of the wheel of large diameter, the ratio of the sizes of 
the two bevels, and the ratio of reduction of the worm gearing, which, 
in addition, is irreversible. The steering gear is thus eliminated and 
four simple gears substituted for it. 


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Couple-Gear Type. In the Couple-Gear wheel, which is an 
American product, the motor is placed inside of the wheel — a type 
especially designed and constructed for this purpose. With the 
motor in this position, the wires enter through the hollow hub, 
altering its construction very materially. As compared with the 
electric motor on each wheel, previously described, this form has the 
advantage of greater simplicity, . fewer parts, superior appearance, 
and protection against the elements, while the enclosed position of the 
motor, which is the most delicate part of the machine, protects it 
against road obstructions and accidents. This arrangement also 

simplifies the steering 
problem, since the car is 
steered just the same as 
any other truck, much 
of the complication inci- 
dent to an electric motor 
on each wheel being elim- 

Fig. 356 is a view of 
the wheel with the tire 
removed and the whole 
disconnected from the 
axle ends. Aside from 
this, it is complete and 
ready for use. Note how 
the axis of the motor is 
« « a -r, j ,r. * „ i r, ™ . „ ^_. set at a very slight angle, 

Fig. 356. End View of Couple-Gear Electrically Driven J & & > 

Wheel with Tire Removed j us t sufficient to allow a 

pair of very small driving gears at the two ends of the armature shaft 
to drive on opposite sides of the wheel. The wheel is assembled with a 
pair of driven gears on either side, these being separated a compara- 
tively small distance, about 2\ to 3 inches. As stated, the armature 
shaft has a small bevel pinion on each end, each of these meshing with 
the driven gears, but on opposite sides. It is this arrangement which 
gives the device its name of Couple-Gear. In this figure the brake 
band has been removed, but the brake drum will be seen just inside 
the wheel at A. Beyond this is noted the spindle B, which is made 
hollow for the wires from the battery and turns in a bearing on the axle. 



In the second illustration, Fig. 357, an axle, either front or rear, 
with the wheels removed, is presented. In this cut the left wheel is 
entirely removed, but the one on the right shows the axle spindle B, 
the method of fixing it in the axle support at C; the armature housing 
D is normally within the wheel and not visible. One feature peculiar 
to this arrangement is the steering, which is effected by means of 
a vertical post with a small spur gear at its lower end E. This 
meshes with a curved rack F, which is machined on the outside of 
a pivoted member G, to which a pair of arms are attached. One of 
these arms H has a rod I, which runs to and operates the right-hand 
spindle B, while the other J has a similar rod K, which operates the 
left-hand wheel. When all four wheels are to be driven in this 
manner, the post is vertical, but the connection with the rack F 

Fig. 357. The Couple-Gear Axle and Parts, Showing Method of Operation 
Courtesy of Couple Gear Freight Wheel Company, Grand Rapids, Michigan 

becomes horizontal, with a continuation to the rear axle which 
operates the various arms, levers, and rods there in the same manner. 
This particular system is used for heavy commercial work only, 
and in this it has been particularly successful as a tractor, a front axle 
and a pair of wheels being substituted for those of a heavy trucking 
wagon. Then, with a sling under the body or beneath the driver's seat 
for the batteries, and with proper wiring, control levers, and steering 
wheel, the truck becomes electrically driven. 

Classification. Generally speaking, front axles may be divided 
into about five classes: the Elliott, the so-called reversed Elliott, the 
Lemoine, the front-drive form, and the fifth-wheel form. 


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These typical forms of axles are themselves subject to further 
subdivisions. For example, there are many different forms of Elliott 
axles, each manufacturer having what is practically his own form. 
Again, the Lemoine, when used by other firms, has been built in a 
practically new form, taking the second maker's name. Thus the 
form of front axle made by Lemoine for Panhard is so different as to 
be called the Panhard, and not the Lemoine. The same is true of 
the Lisses axle made by Lemoine. In this country, it is claimed 
that the axles made by Timken are sufficiently different from the 
Elliott and reversed Elliott, from which the principle was taken, as to 
deserve the name of Timken axles. It should be borne in mind that 
in the following description of the various axle types the forms of 
material, and the shape, size, and kinds of bearings used do not alter 

Fig. 358. Elliott Type of Front Axle and Steering Knuckle 

the principle upon which the axle is constructed, although they do 
alter the appearance. 

Elliott Type. In general, a front axle consists of a bed, or axle 
center; a pivot pin or knuckle pin upon which the knuckles may turn; 
and the knuckles themselves with the attachment for turning them. 
The Elliott type, Fig. 358, the form in which the end of the axle 
takes a U-shape, is set horizontal and goes over the knuckles. 
The knuckles have plain vertical ends bored for the pivot pin, which 
passes through and has its bearing in the upper and lower halves of 
the axle jaw. In this form, the thrust comes at the top, where the 
axle representing the load rests upon the top of the knuckles that 
represent the point of support. 

Reversed Elliott Type. In the reversed Elliott front axle, as the 
name would indicate, the action is just reversed in that the axle end 


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forms a straight vertical cylindrical portion bored for the pivot pin, 
while the knuckles are so formed as to have jaw ends which go over 
the axle ends. The thrust comes at the bottom of the knuckle, 
where the axle bed rests upon the upper face of the lower jaw of the 
knuckle, the axle representing the load and the knuckle the support, 
just the reverse of the previous case. 

This will, perhaps, be made clearer by illustrations. In Fig. 
358, as already mentioned, the axle has the jaw ends, and the thrust 
comes at the top. This is indicated in the figure by the letter A, 
which calls attention to the thrust washers at the top. Fig. 359 
shows an axle of the reversed Elliott type, this being the front axle 

Fig. 359. Reversed Elliot Type of Front Axle and Steering Knuckle 

for a heavy truck. In this the thrust washers A are at the bottom, 
and are of hardened steel, ground top and bottom to a true surface; 
the upper surface is doweled to the axle, while the lower is doweled 
to the knuckle. This form has the real advantage of concentrating 
all of the difficult machine work and assembling it into one piece, 
the knuckle. The Elliott type, on the contrary, makes the knuckle 
and axle difficult pieces to handle in the machine and afterward, this 
being shown in the cost. Ease of machining the bed of the axle 
is a great advantage, for the axle will average about 44 inches in 
length for a standard tread of 56 J inches, and longer for wider treads, 
up to a maximum of about 48 inches for the wide-tread standard in 
the South. 


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The ordinary automobile machine shop is not fitted up for work 
of this size, particularly in machine tools other than lathes, and this 
job could not be done on a lathe. The result is that it becomes a task 
to handle it, necessitating special and expensive rigging for that one 
job. This was the case with the axle shown, a boring mill of the hori- 
zontal type and a large size milling machine being used on it. Both 
of these had to have special fixtures, which were useless at other times, 
to hold and machine these parts. At that, this job was much easier 
than an axle of corresponding size in the Elliott type would have been. 
Lemoine Type. The Lemoine type of front axle differs from 
those described in that the axle proper bears upon the top or bottom 
of the knuckle-pin part of the knuckle, the two being made as one; 
that is, an extension or a jaw of the axle does not support the knuckle 

as with the Elliott type. 
When the steering knuckle 
of the Lemoine type is 
mounted below the axle 
stub, the latter is carried 
higher than with the re- 
versed Elliott, so as to 
rest upon the top of the 
knuckle. An advantage of 
the construction from a 
manufacturing viewpoint 
is the cost of machining. 
With this design, the thrust load is practically entirely at the bottom 
upon the knuckle, which also must take all side loads; it is fastened 
in a sidewise direction at but one point — the bearing in the axle. The 
side shocks are taken on the end of a beam fixed only at the other 
end, whereas with the other types, the load is distributed between 
two supports, or divided equally over two sides, the point of support 
being midway between them. With the Lemoine type discussed, 
the bottom bearing must compensate for radial and thrust loads — 
a difficult condition to meet. 

While the design is easy to machine, assemble, and handle, its dis- 
advantage is that the knuckle has a double duty, having, as it does, both 
radial and thrust loads to care for because of its one-piece construc- 
tion. This type of axle is, however, very popular with foreign designers. 

Fig. 360. Inverted Lemoine Type of Axle 
as Used on Overland Cars 


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Inverted Lemoine. A novel type of axle has been created in the 
1916 Overland car, Model 75, called an inverted Lemoine. In 
this type, as Fig. 360 shows, the wheel spindle, or stub axle, is at 
the top of the steering knuckle instead of at the bottom as in the 
case of the regular Lemoine type. The knuckle has a single, fairly 
long support in the end of the I-beam front axle, the forging being 
much simpler on this account. In fact, this makes the axle nearly 
straight, which doubtless accounts in large part for this unusual 
design. One real advantage of this design is that it allows the car 
weight to be low in relation to wheel bearings, thus assisting in steering. 

Courtesy of Nor dyke and Mormon Company, Indianapolis, Indiana 

Marmon Self=Lubricating Axle. The new Marmon front axle, 
Fig. 361, is of the inverted Lemoine type similar to the Overland, 
shown in Fig. 360, but at first glance it looks quite different. For 
one thing, the bearing in the axle end is different, and in this 
lies an exclusive and valuable feature. The stub-axle pivot pin, 
made integral with the stub axle, is placed in a split bushing, which 
is a tight fit at the bottom — where the thrust collars are formed in it — 
and at the top, but not in the middle. When this bushing is in place, 
the knuckle and bushing are forced into the axle end from above, 
and a kind of hub cap screwed on at the bottom. This holds it 
permanently in place. 


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Near the middle of the split bushing there is a narrow slot to 
which a central bolt hole is connected. • On being assembled, the 
inside is filled with lubricant, which cannot escape; but, as it wears 
away, the central bolt can be removed, more lubricant can be poured 
in until it is full, and the bolt replaced to prevent leakage. In this 
way the axle is selfflubricating, and, as the oil is used up very slowly, it 
needs practically no attention. 

Fig. 362. Front Elevation of Car, Showing Camber of the Front Wheels 

Like the Overland, this arrangement of the axle end brings the 
axle down low, relative to the weight, and consequently steering is 
made easier. The lowering of the axle also brings the points of 
spring support down and thus lowers the whole car. 

Camber Somewhat Complicates Axle Ends. All front wheels 
are dished, that is, the spokes do not lie in a flat plane but in the 
form of a cone, with the point of the cone at the outer end of the 
hub and the base'of the cone at the rim of the wheel. Now all roads 


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and most all pavements are made with a camber. The center of the 
road is made higher than the sides so that the road will drain. It 
is necessary, in order to have the lower spokes plumb or perpendicular 
to the road surface, to throw the center line of the wheel out of the 
vertical plane 2 or 3 degrees. This offset is also called camber, and 
it complicates the construction of the axle ends to such an extent 
that they must be machined with this slight angle either in the 
knuckle or in the axle, or distributed over the two places. 

Fig. 362 shows the effect of this camber upon the front appear- 
ance of the car, the slight angle of the front wheels giving the car a 
bow-legged appearance. 

Gather Further Complicates Axles. What the carriage men 
term "gather" further complicates the axle ends. This is the practice 
of setting the axle so that the front wheels are closer together at 
the front than at the rear, that is, they toe in. The idea of this is 
to make steering easier and, more particularly, to make the car 
self-steering on plain, level, straight-ahead roads. It is scarcely 
noticeable from in front, but is from above. Although many cars 
still have it, it is not used as much now as formerly. 


The materials utilized for front axles include castings of steel, 
manganese bronze, iron, and other metals, in the form of forgings, 
drop forgings, drawn or rolled shapes, and pressed shapes. Wood 
has been but little used and only in the past. 

Cast Axles. Castings for front axles have been looked upon 
with grave doubt and fear by designers and owners, because of 
the fact that road shocks are more severe for front than for rear 
axles, and because of the fear that a casting may have a blowhole 
or some other defect. In addition to the natural distrust of castings 
for this work, it was feared that such material would crystallize more 
quickly than would a better and more homogeneous material like 
steel. There is, of course, a certain amount of crystallization in all 
materials, but far less in a close-grained fine-fibered structure like 
forged or rolled steel than in any form of casting. Aside from this, 
castings present many other advantages which are well worth while. 
Thus, the spring pads may be cast integral with the axle with prac- 
tically no extra charge, while the same forged integral with a drop- 

143 ^le r 


forged axle may easily add several hundred dollars to the cost of the 
dies. Again, with casting patterns, the fillets may be changed easily 
to give a greater section here or to reduce a section there, while a 
similar action with any forged axle means a new set of dies, costing 
perhaps $600. There are many other machining helps which may 
be provided in cast axles without any extra cost. 

Notwithstanding these many advantages, the casting for the 
front axle has been and is distrusted, and the makers who have used 
it have flown in the face of popular prejudice, for the public has 
mistrusted jt even more than the makers. For this reason, the cast- 
ing has been little used, and the writer fails to recall a single car 
with a cast axle now on the market. 

Forgings. Forgings, as distinguished from drop forgings, are 
much used for good front axles, but are expensive. The writer knows 
of one excellent truck builder, striving to build the best truck in the 
world, who is using a hand-forged front axle, the end of which is 
shown in Fig. 359. It is forged down from a 6-inch bar of selected 
steel and the ends worked out so as to leave the bed proper a 2§- by 
2|-inch section, which later has been increased to 3 inches square. 
This made a very costly piece of work, but the stand-up qualities 
shown in actual work more than made up for it as long as people could 
be found to pay the price demanded for a truck made along these lines. 

Many smaller makers follow out the same scheme, the lighter 
work allowing the axles to be forged up much more quickly, more 
easily, and more cheaply. The smaller the amount of material to 
be heated, the less difficult will be the work, and the more quickly 
will progress be made. The general trend of axle practice today, 
however, is to turn over the axle job to specialists in that line, most 
of whom employ drop forgings, drawn- or rolled-steel tubing with 
drop-forged ends, or similar rapid-production forms of construction. 

Drop Forgings. Drop forgings are now more used than any other 
form, although the first cost is great, for the dies must be very care- 
fully worked out in a very high grade of steel; the result is a large 
expense of from $750 to $1200 before a single axle is turned out. 

As a matter of fact, with drop forgings, after the die is once 
made, the axles may be turned out rapidly, accurately, and with 
little labor and cost. Given the dies, therefore, there is no doubt 
that this method produces an ax!e at a very low first cost. Moreover, 

144 Digitized by 




the method itself produces better quality, for any process which 
works steel or wrought iron over and over again improves its quality, 
provided the steel is not burned in the process of heating. Not only 
are the majority of axles made of drop forgings, but of those not so 
made some part is almost sure to be a drop forging, as, for example, 
those made of steel tubing which have their ends or other parts 
made by the drop-forging process. In Fig. 363 is shown a drop- 
forged axle used on a truck. 

Tubular Axles. The I-beam section of front axle is universally 
used, and while the tubular type formerly enjoyed some popularity, 
its use today is confined to a very few vehicles. When employed, 
its ends are drop forged or drawn, or rolled steel may be used 
with the ends welded or otherwise secured. The disadvantage of 
the tubular type is the fastening of the ends which is more or less 
offset by the lowered cost of material. 

Fig. 363. Typical Drop-Forged Axle Used on Truck 

Drop-Forged Ends. Nearly all the ends for axles made in this 
way are drop forgings, very few castings being used, while the spring 
pads, or spring seats, as they are sometimes called, are split into 
upper and lower halves and bolted on. 

The loading conditions of all front axles are such that the load 
rests on the axle at two points inside of the supporting points — 
the wheels. Thus, the continual tendency of the load acting down- 
ward and of road shocks acting upward is to bend the center of 
the axle still further downward. Since a tube which has been bent 
once has been weakened, it follows that this tendency to weaken it 
presents a further source of trouble. 

Pressed-Steel Axles. The pressed-steel type of axle, which 
made its initial appearance in 1909, and is not generally employed, 
consisted of a pair of pressed-steel channel shapes — one being 


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slightly larger than the other — set together with the flanges 
inward so as to present a box-like shape. When thus arranged, the 
two sections were riveted together by a series of rivets running ver- 
tically along the center part of the channels. The ends consist of 
drop forgings, machined to size or space between the channels when 
assembled, and then set into place between the ends and riveted. 
The pressed-steel construction obtained a secure attachment to the 
bed. This axle was of the Elliott reversed type. 

Change of Axle Type Simplifies. Often the change from one 
type of axle to the other is not made because the latter is better but 
because of some incidental saving in the manufacture. Thus, in 

Fig. 364. Differences in Construction of Reversed Elliott and Elliott Types of Axle Knuckle 

Fig. 364, we see the reversed Elliott type at the left at A and the 
Elliott type at the right at B. From a manufacturing point of view, 
the former is much cheaper to construct, for the axle and knuckle 
costs would just balance one another, but the forging and machining 
of the one-piece steering arm shown in B would be more than double 
that shown in A. Moreover, the number of dies and their cost 
would be about three times as much, while the customer would have 
to be charged two or three times as much for repair parts. That is, 
in a modern low-priced car, produced in tremendous quantities, the 
advantages and costs connected with the two-piece steering arm of 
A would influence the choice of that design, regardless of other 
advantages or disadvantages. 


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Classification. Thus far nothing specific has been said about 
axle bearings. These are, according to construction, of three kinds: 
plain, roller, and ball. From the standpoint of the duty which 
they are to perform, bearings may be divided into radial-load and 
thrust bearings, all three forms mentioned above being used for 
both purposes, but arranged differently on account of the difference 
in the work. Each one of the three classes may be further subdivided. 
Thus, plain bearings may be of bearing metal or of hardened steel, 
or they may even be so constructed as to be self-lubricating. Again, 
plain bearings may mean no bearings at all as in the old carriage 
days when the axle passed through a hole in the hubs, and whatever 
wear occurred was distributed over the inside of the hubs, resulting 

Pig. 365. Front Axle End, Showing Roller Bearings for Wheel 
and Steering Knuckle 

after a time in the necessity for either a new set of hubs or a new axle, 
or for the resetting of the axle, so that the hubs set further up on a 
taper. Roller bearings may be of several classes, some makers using 
both straight and tapered rollers. In addition to these there are 
combinations of the straight and tapered types, and bearings with 
two sets of tapered rollers acting back to back, the action being that 
of straight rollers, with the end-adjustment feature of the tapered 
type. There are also many types of ball bearings, as, for example, 
plain ball bearings — those working in flat races, those working in 
curved races, those working in V-grooved races, and single balls 
working alone. There are also combinations of balls in double rows. 


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Roller Bearings. Fig. 359 shows the use of tapered roller bear- 
ings for the hubs and of hardened-steel thrust washers for the thrust 
load, the figure showing, in addition, a plain brass bushing in the 
axle for the knuckle pin to turn in. In Fig. 365 is shown a more 
elaborate use of roller bearings of very excellent design. In addition 
to the axle bearing, it will be noted that the top bearing of the steer- 
ing knuckle is of the roller type. 

Ball Bearings. Although there is a growing tendency to utilize a 
short adjustable type of roller bearing, many designers favor the ball 
bearing. The two most common forms are the cup and cone type, 
which cares for radial and thrust loads, and the annular form which 

Fig. 366. Front Axle and Steering Knuckle of Superior Construction 

is suited for supporting annular loads. The annular form is not 
adjustable, and when it wears it must be replaced with a new bearing. 
The cup and cone type is adopted by makers of low-priced and 
medium-priced cars, has an angular contact, and is adjustable. 

In some instances, particularly with high-grade cars, ball bearings 
are used for the knuckle bearings as welL as for the hub. Fig. 366 is 
an example of an axle end, which for real bearing worth, has probably 
never been surpassed; this is the axle end and steering knuckle of a 
very high-priced car, not now made, but one on which no expense 
was spared to make it perfect. The illustration shows the wheel 
hubs running on two very large diameter ball bearings, while the 
knuckle also turns on two very large ball bearings arranged for 


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radial loads. At the top is another ball bearing arranged for 
thrust; this bearing taking up all thrust loads from the weight above 
or from road inequalities. Fig. 367 illustrates the cup and cone type, 
This design utilizes ball bearings for the hubs and plain steel thrust 
washers on the knuckle. 


Alignment of Front Wheels Troublesome. The lack of align- 
ment of front wheels gives as much trouble as anything else in the 


«... fiQ^Qib. -■- 


Fig. 367. Front Axle Details of Waverley Electric Car 
Courtesy of the Waverley Company, Indianapolis, Indiana 

front unit. This lack not only makes steering difficult, inaccurate 
and uncertain, but it also influences tire wear to a tremendous extent. 
As Fig. 368 indicates, even if the rear axle should be true with the 
frame, at right angles to the driving shaft, and correctly placed 
crosswise — correct in every particular with the shafts both straight 
so that the wheels must run true — the fronts may be out with 
respect to the frame, out of track with the rears, or out with 
respect to each other. 

In order to know about the front wheels, they should be meas- 
ured; while this sounds simple, it is anything but that. In the first 


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place there is little to measure from or with. A good starting place 
is the tires, and a simple measuring instrument is the one shown in 
Fig. 369. This instrument consists of a rod about J inch in diameter 
and about 3 feet long, fitted into a piece of pipe about 2 feet long, 
with a square outer end on each, and a set screw to hold the meas- 
urements as obtained. By placing this rod between the opposite 
sides of the front tires, it can be ascertained whether these are par- 


Fig. 368. Diagram Showing Front Axle and Wheels Out of True 

allel, and whether they converge or diverge toward the front. But 
knowing this, the driver or repair man is little better off than before, 
because this may or may not be the practice of the makers of the car, 
and it may or may not cause the trouble. 

In short, a more accurate and more thorough measuring instru- 
ment is needed, Fig. 370. Such an instrument can be bought, but a 
similar outfit can be made from f-inch bar stock, using thumb nuts 




■Set Screw 


Fig. 369. Simple Measuring Rod for Truing-Up Wheels 

where the two uprights join the base part, and also at the two points, 
or scribers, on these uprights. Having the floor to work from, the 
heights can be measured, and thus the distance between tires may be 
taken on equal levels. Thus, a bent steering knuckle can be detected 
with this apparatus. Similarly, the center line and frame lines of 
the car can be projected to the floor, and by means of the instrument, 
it can be determined whether the axle is at a perfect right angle 


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with the frame lines, and whether the wheels are perfectly parallel. 
Given the frame line, too, it can be determined whether the wheels 
track with one another. 

Straightening an Axle. When an axle is bent, as in a collision, 
a template is useful in straightening it. This can be cut from a 
thin sheet of metal, light board, or heavy cardboard. It is an approx- 

Fig. 370. Accurate Measuring Rod for Truing- Up Wheels. Better Design than Fig. 369 

imation at best and should be used with great care. Fig. 371 shows 
such a template applied to an axle which needs straightening. 

When the axle is bent back to its original position, a pair of 
straightedges laid on top of the spring pads will be of great assistance 
in getting the springs parallel, as the worker can look across the 
straightedges with considerable accuracy. This is indicated in the 

Fig. 371. Template for Showing if Axle Is Bent 

first part of Fig. 372, which shows the general scheme. It shows also 
how the axle ends are aligned, using a large square on top of a 
parallel bar, but of course this cannot be done until the last thing, 
at least not until the spring pads are made parallel. 

Front axles of light cars may be straightened without removal, 
provided the bend is not in the nature of a twist and not too short. 
Take two hardwood planks 7 feet long, 10 inches wide, and 2 inches 


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thick. Next, cut four f-inch blocks 10 inches long and 3 inches wide. 
Lay the blocks flat between the planks, space-them about 2 feet apart, 
and bolt the whole securely. This obtains a girder 7 feet long, 10 
inches wide, and 4f inches thick, Next, take two pieces of 4X4 timber 
3 feet long and cut a tenon on one end of each. Make three f-inch 
eye bolts, 12 inches long, with nuts and plate washers for each. Place 
one of the eye bolts between each pair of blocks and screw up the nuts 
and washers sufficiently so as to rivet them. This permits of moving 
the eye bolts to any position between the blocks. Two small steamboat 
ratchets and several short but strong chains complete the equipment. 

Fig. 372. Diagram Illustrating Method of Truing-Up an Axle 

With an axle bent back in the center, lay the girder on blocks in 
front of the car so it will be level with the axle, place the tenons of 
the 4X4 timbers in the space between the planks of the girder, one on 
either side of the bend, and connect the axle to the girder by means of a 
chain, the ratchet, and the eye bolt. When the ratchet is tightened up, 
it draws the ends of the4X4's against the axle on either side of the bend. 
Tightening the ratchet still further removes the bend. This work 
may be accomplished in 20 minutes or less or in about one-tenth the 
time it will require to displace the axle, heat it, and straighten on an 
anvil, etc. The apparatus can be used for straightening many differ- 
ent bends; all that is necessary is a different arrangement of its parts." 


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For example, a downward bend can be straightened by placing the car 
above the girder, connecting the axle to the girder, and using a short 
screw jack to remove the bend. This device can be used with success 
in shops dealing with light- or medium-weight cars. 

Spindle Troubles and Repairs. Wear of the spindle, or knuckle 
bolt, and its bushings, as well as play in the steering-gear linkage, brings 
about wobbling of the front wheels when the car is in motion. Some 
experienced persons mistake wear of the knuckle and the bushings for 
play in the wheel bearings, and attempt to remedy the trouble by 
adjusting the bearings. It is a simple matter to determine the com- 
ponent at fault. To test for bearing play, drive a block of wood 
between the knuckle and the axle, then grasp the wheel at the top and 

Pig. 373. Use of Wedge to Cure a Wobbling Wheel 

bottom, or at points diametrically opposite, and test for looseness. 
If none exists, the play is in the knuckle pin and its bushings. The 
remedy is to fit new bushings and new knuckle pins. 

Wobbling Wheels. Wobbling of the front road wheels is gener- 
ally due to play in the joints of the steering mechanism, and it is not 
only troublesome, but also sets up undesirable stresses on the steering- 
gear linkage. This flapping of the wheels may be present with the 
steering gear and linkage in perfect operating condition, and similarly 
when the springs, hangers, etc., are in good condition and the proper 
toe in, or gather, of the wheels exist. 

When the wheels wobble it may be assumed that the front springs 
have so settled that the steering pivots are not quite vertical fore and 


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aft, particularly with reference to that type of pivots which do not 
incline outwards and where the wheels are canted or dished to bring 
their points of ground contact in line with the pivots. A cure for this 
trouble is to place wedges between the front springs and spring seats 
so as to alter the angle of the steering pivots, as shown in Fig. 373. 
Metal wedges are used, about f inch thick at the large end, and 
tapered to a knife-like edge. The wedge is placed at the forward end of 
the axle, and a little experimentation will give the results desired. 
In wedging, as few wedges should be used as is necessary to obtain the 
desired result. 


In arranging a logical presentation of the numerous components 
of the motor vehicle, the chassis is separated from the body. It 
includes the power plant and mechanism utilized in transmitting the 
energy of the engine to the road wheels, also the frame and suspen- 
sion, the axles, etc. However, only frames, springs, and shock 
absorbers will be discussed in this section, as the other parts of the 
chassis have been treated. 

Characteristics of Parts. Frames. The chassis frame practi- 
cally is the foundation of a motor vehicle, since all of the power 
transmitting and other units are attached to it. Motor- vehicle 
construction depends, to a certain extent, upon the general design 
of the chassis, the construction of the power plant and transmit- 
ting units, their mounting, the method of final drive, the wheelbase, 
etc. The size of the material used depends upon the weight of the 
units carried and the capacity of the vehicle, and varies from thin 
and small sizes on very light pleasure cars to heavy structural I-beam 
frames on commercial vehicles. 

The use of pressed steel is becoming more popular, as is also the 
tendency to narrow the frame at the front to obtain a shorter turning 
radius. The majority of designers favor what is termed a kick-up at 
the rear, which affords better spring action and permits of a low sus- 
pension of the body. The use of tubing and wood has practically 
been abandoned. There is a slight return to favor of the underslung 
suspension, a form that was popular several years ago but which did 
not then obtain the results claimed for it, as the springing gave some 


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Springs. The primary function of the spring is to absorb the 
road shocks that would otherwise be communicated to the mechanism 
and passengers. Considerable progress has been made in the past 
year toward improving springs, and not only are they better pro- 
portioned, but improved material and methods of mounting have, to a 
great extent, eliminated breakage. The leaf type, developed by the 
horse-drawn carriage industry, is the form universally employed on 
motor vehicles, both pleasure and commercial. [ 

A review of the 1916 springs for cars showed that the three- 
quarter and seven-eighths elliptic spring was favored by 46.5 per cent 
of the makers, while some form of cantilever spring was second with 
28.7 per cent for rear suspension. This year the advocates of the 
cantilever have gained many recruits. In the matter of front springs, 
the semi-ellipic may be said to practically monopolize the field. 
The coil spring is a thing of the past. 

Shock Absorbers. The fitting of shock absorbers as standard 
equipment is not as noticeable as it was in 1916 and the year previous. 
The use of high-speed engines with light reciprocating parts, and the 
employment of high-grade light material in other components of the 
chassis, together with better springs, serves to absorb shocks created 
by traversing rough roads. A few makers supply shock absorbers, 
but, as a rule, the car manufacturer leaves the selection to the pur- 
chaser. Many different types of shock absorbers are marketed, and 
use is made of varying principles. 


General Characteristics. When the automobile was first intro- 
duced, comparatively little attention was paid to the frame, as the 
other components of the chassis, such as the power plant, gearset, 
axles, etc., were held to be of greater importance, consequently the 
frame did not receive the consideration it should. After experiencing 
considerable difficulty, however, due to accidents and other failures 
which were traced directly to poor frame design, the automobile 
engineer found that it was possible to build a frame of great strength 
with less weight than the troublesome types. This statement applies 
to the frame of the commercial car as well. 

The improvement in frame design is the result of the tendency to 
provide perfect alignment of the power plant, clutch, and gearset, 


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making use of what is known as the unit power plant on some models, 
while on others, particularly of the heavier type, flexible mounting 
of the units has been resorted to. The tendency is toward the use of a 
flexible mounting of all individual units, at least to some degree, in 
order to relieve them of the stresses brought about by frame weaving 
when the road wheels mount an obstacle on the road surface. 

Classes of Frames. The most prominent types of frames, divided 
according to their use, are the pressed-steel frame, the structural 
frame, and the structural I-beam frame; the latter is confined to com- 
mercial cars. These classes may be subdivided according to the 
general construction and material, as well as to the distribution of 
the chassis units. 

The material employed is either pressed or rolled steel. The 
wood frame or combinations of wood and metal frames are practically 
a thing of the past, and are to be found, with one or two exceptions, on 
old cars. The steel frame may be constructed in the following shapes : 
^channel, L-beam, angle, T, Z, tubing, flat plates, and combinations 
of any two or more of these. Other forms are possible. For example, 
the channel may be turned with the open side in or out, the two con- 
structions being widely different; or the angle may have the corner 
down and out, down and in, up and out, or up and in. Similarly, the 
T-shape may be a solid T turned up or down, or it may be a hollow 
T-section with space between what might be called the two sides of 
the leg; this shape may be turned either up or down, while the 
Z-shape may be turned horizontally or vertically. Many frames are 
constructed with the open end of the channel section turned in, and 
use is made of a steel underpan of flat section attached to the under 
side of the main frame. In several instances there is a tendency to 
make the frame and underpan as one piece, in which case the frame 
section assumes the shape of a channel with an exceedingly long lower 

Another type of frame is that having a continuous section 
throughout. Others have a varying section. Thus, the ordinary 
steel frame of modified channel section may have a depth of perhaps 
5 inches at the center, a width of upper flange of 1 \ inches, and a width 
of lower flange of 2 inches. A frame similar to this would taper down 
to the ends to perhaps 20 inches in vertical height, and to 1 inch in 
width of both top and bottom flanges. Then, again, frames which are 


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bent upward or downward at the ends or in the middle really differ 
from those frames which preserve one level from end to end. The 
practice of bending the chassis frame is very prevalent of late, 
the upturning of the ends bringing about a lower center of gravity, 
making for stability and ease of entrance and exit to the body. 

Tendency in Design. There is a marked tendency toward mak- 
ing the chassis frame wider at the rear and narrower at the front. 
In one or two cases the designer appears to have gone to the extreme 
in this respect. The advantage of the narrow front construction is 
that it enables the car to be turned in a shorter radius. The use of a 
wide rear frame provides more space to support a wider body. A 
more recent development is to make the longitudinal bars of the frame 
parallel over the front spring and near the rear spring, and to have 
them tapered from behind the front to the rear springs. A certain 
amount of material is said to be gained by this construction, as no 
heavy reinforcement or sudden offset is necessary to the frame. By 

' ** '\s> 'V " a 

Fig, 374. Typical Automobile Frame of Pressed Steel 

widening the frame at the rear it makes possible the placing of 
the springs directly underneath the frame. Some car makers have the 
sides of the frame straight over the entire length, but tapered from 
the front to the rear. 

Fig. 374 illustrates what is termed a single drop or a kick-up. 
This is a type of pressed-steel construction, of channel section, and 
the deepest and strongest section is at the center where the greatest 
stresses occur. Some frames are built with a double drop, having 
a downward bend just forward of the entrance to the rear part of the 
car body, followed by an upward turn just back of the same entrance. 
The upward turn at the back is carried higher than the main part of 
the frame for the purpose of obtaining a low center of gravity. Then 
there is what is termed the bottle-neck construction, a bend inward 
which resembles that in the neck of a bottle. This obtains a short 
turning radius. Originally, frames were narrowed in front, the differ- 
ence in the width between the front and rear being at first an inch 


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or so on each side, gradually increasing until it became 5 and 6 inches. 
This type did not prove efficient, and the trend favored the taper 
previously explained. 

A not uncommon form of frame is shown in Fig. 375, which com- 
pensates for an abnormal rise of the rear axle without the possibility 
of its striking the frame. Some frames have a bend at the ends to take 
the spring fastenings. 

Pressed-Steel Frames. The pressed-steel type of frame is very 
popular with designers and is largely used on commercial cars up to 
and including 1-ton capacity. This is popular because it is the lightest 
in weight for equal strength of the structural iron or rolled channel 
and I-beam section. The cost of pressed steel is somewhat higher, 


S£C TION Fhf? 


Fig. 375. Frame of Sterns-Knight Car in Plan 

because it is heat-treated material used to obtain maximum strength. 
The cost varies with the section, material, and the nature and extent 
of bending. The finished frames are easy to handle, and the assem- 
bling cost is small. The channel shape is easy to brace and repair. 
These and other advantages have brought about its use. 

The cheapest construction is the straight side rail, and, when 
conditions permit, it is usually tapered at front and the rear, and the 
forward end is sometimes shaped to receive the spring hangers. 
When the side members are inswept to permit a short turning radius, 
it is necessary to make the flanges of the side rail of considerable width 
at this point, tapering gradually to the rear, to provide the proper 
strength at the point of offset. 


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Sub-Frames. The modern tendency is to eliminate the sub- 
frame — a step due to the flexible mounting of the power plant and 
unit construction — because it simplifies the frame. It has also been 
made easier by the tapered frame, which is narrowest at the front 
where the units are attached. The oiost common method of support- 
ing the engine is the three-point. Sub-frames are used, however, as 
they serve the purpose both of supporting some unit and of strength- 
ening the frame. 

Sub-frames may be of two kinds, viz, those in which the sub- 
frame is made different for each unit to be supported, and others 
in which one sub-frame supports all units regardless of size, shape, 
or character of work. The type of sub-frame made to support each 
unit usually works out to two pairs of cross-members, one for the front 
of the unit and one for the rear; while the type which supports all 
units regardless of size works out to longitudinal members, supported, 
in turn, by two cross-members, front and rear. The added weight for 
the first-mentioned type is less than for the other, since it comprises 
only four cross-members; while the last-named type consists of two 
cross-members equal to two of the others and of two very long members 
parallel to the main-frame members, each much longer and thus 
much heavier than the corresponding cross-members. In the two 
frames already shown, Fig. 374 shows the unit type of sub-frame with 
only cross-members, while Fig. 375 shows the more modern type in 
which the power plant is of the unit type and rests directly upon the 
main frame, being the three-point suspension type in which the 
forward point is on a frame or special cross-member, while the rear 
two points are the crankcase supporting arms resting directly on the 
main frame. 

Rigid Frame. A pressed-steel or rolled-stock rigid frame has its 
advantages, particularly with reference to the commercial vehicle. 
It permits the body to be rigidly secured to it, and as it does not give 
with the inequalities of the road, the body is not racked. An advan- 
tage of the rolled stock is its cheapness, except, of course, for the 
lighter models of the assembled type for which frames can be secured 
at low figures. Another advantage of the rolled stock is the ease 
with which the wheel base may be altered. 

Effect on Springs. The effect of frame construction upon the 
design and duty of springs should be considered. This feature 

159 f 


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is not generally understood, but it has an important bearing upon the 
life of the car. A rigid frame relies upon the springs to allow for all 
axle displacement. If a front and a rear wheel on opposite sides are 
raised several inches at the same time, the frame is subjected to a 
torsional stress. If the frame is rigid, springs of considerable camber 
must be employed in order to absorb the shock without being bent past 
the limit of safety, and they must be sufficiently flexible to absorb all 
the shock without any tendency to lift the other wheels from the 
ground. To accomplish this shock absorption, a different type of 
spring is used on a rigid chassis from that employed on a flexible 
frame. The use of underslung spring suspension has come into favor 
for this reason, as it permits the frame to be carried fairly low, without 
sacrificing spring camber or necessitating a dropped rear axle. 

The flexible frame, when diagonally opposed wheels are raised, 
does not impose all the stresses on the springs but it absorbs 
a part of them. For this reason, springs on a flexible chassis 
are flat or nearly so, with a limited amount of play. Flexible con- 
struction also permits the frame to be carried equally as low as with 
the underslung spring, and yet the spring is perched above the axle, 
where it is more nearly in line with the center of gravity, thus reduc- 
ing side sway. 


- Pressed Steel. Pressed steel is purchased iri sheet form, cut to 
the proper shape in the flat, and then pressed into channel form under 
great pressure. It is made of steel rolled into sheets and is somewhat 
closer grained than ordinary steel. There is no breaking of the flake 
in the rolling process. The pressed-steel frame, as previously pointed 
out, permits of greater simplicity in assembling, since the parts can be 
easily bolted or riveted. Fig. 376 is of the type of pressed-steel frame 
having a tapering section, a kick-up at the rear end, five cross-members 
— one of them a tube — and is narrowed in at the front to give the 
largest steering lock. Otherwise it presents only standard practice. 
Wood. Wood is universal and easy to obtain. While no longer 
classed as cheap, it is not expensive; moreover, wood is kept in stock 
nearly everywhere. Users of wood for side-frame members claim 
that the wood frame is not only lighter but stronger. In addition, 
the wood frame would undoubtedly possess more natural spring and 




Comparative Strength of Steel Channels and Laminated Wood Frames 



Weight per 

Linear Inch 




Moment per Unit 


Pressed Steel 






resiliency, so that it would make a lighter and easier riding frame. 

A section of a wood frame is shown in Fig. 377. 

This shows a frame made of laminated wood. There are three 

very thin sections of selected ash, marked A, which are glued together, 

then screwed and bolted to pre- 
vent the glue from opening up. 
To further this purpose, a strip B 
is fastened on the top and bottom 
in the same manner. These strips 
are laid with the grain running 
horizontally, while the main 
pieces are laid with the grain 
running vertically. This con- 
struction makes a very strong 
and light-weight frame; the com- 
parative figures for a steel sec- 
tion and the section shown, as 
given from the tests of the engi- 
neers of the Franklin Company, 
is shown in Table IV. These 
tests, which are authentic, seem 
to bear out the contention that 
the wood frame is both lighter 
and stronger than the steel frame. 
The Fergus car, Fig. 380, 
has a steel frame having a com- 
bination of lattice and girder 
work to increase its strength. 
Recent Types of Frames. An innovation in frame design is the 

Marmon, shown in Fig. 381, the side rails and running boards of which 

are made in a single unit. The great width of the running board, 

i'ig. 377. Section through Wood Side-Frame 
of Franklin Car 


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varying from 11| to 16 inches, serves as the bottom flange of the 
frame, and is therefore of Z-section. The vertical section of the frame 
is 10 inches high, and has height enough to replace the running board 
fenders without appearing narrow. At the front and rear ends of the 
frame, the running boards are curved upward, strengthening the frame 

Fig. 381. Marmon Aluminum Frame, Showing Running Board Construction 

as well as supporting the fenders into which they merge. The frame, 
beyond these points, both forward and rearward, is made of channel 
section of the qonventional type. The rear of the frame is 45 inches 
wide and tapers to 30 inches at the front spring hangers. The great 
depth of the frame section makes it very stiff, so that the body sills 

Fig. 382. Brush Pressed-Steel Frame 
Courtesy of Hale and Kilburn Company, Philadelphia, Pennsylvania 

can be entirely eliminated, and yet the doors will not work loose or 
bind when the top is up or down. 

Fig. 382 illustrates a type of frame similar to the Marmon, the 
Brush frame, controlled by the Hale and Kilburn Company, of 


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Steel Underpans. The underpan has assumed a great deal of 
importance in the last two years, for makers have more and more 
realized that it is highly important to protect many of the parts from 
road dirt, flying stones, water, etc. Designers have, therefore, given 


Fig. 383. Two-Piece Pressed-Steel Underpan Used on Winton Cars 
Courtesy of Winton Motor Car Company, Cleveland, Ohio 

considerable attention to its shape, size, and method of attachment. 
In some types, it apparently runs underneath both engine and trans- 
mission and is made more or less a part of the main frame. There- 
fore, its quick removal on the road would be difficult, if not impossible; 
yet road accidents sometimes make it necessary for the driver to take 
this pan off to get at the lower side of engine, clutch, or gear box. 

For this reason, underpans generally resemble more closely that 
shown in Fig. 383. This is a side view, showing the semicircular 
form of the pans, as well as the two-piece construction. The forward 
part under the engine, which would be taken 
down fairly often, is held in place by three 
spring clips on either side. Lifting these 
clips off is only a second's work; in addition, 
there is a filler piece in front, helping to make 
the pan fairly air-tight. The depth of the 
pan increases slightly toward the rear, so as 
to form a slope down which liquids will 
drain; the rear end is fitted with an upturned 
elbow, so that it will not drip until it accu- 
mulates a considerable quantity of liquid. 
Continual dripping indicates a full charge, 
and the pan is drained by turning the elbow 

Fig. 384. Detail of Spring 

and Section of Winton 



In Fig. 384, a detail of the arrangement of the pan shown in 
Fig. 383 is presented. This indicates both the permanent part of the 
underpan, which is attached to the frame, and the removable part, 
which is freed by loosening the spring clips shown. 


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Commercial-Vehicle Construction. Commercial work, being 
rougher, harder, and cheaper work, changes the frame construction 
just as it does everything else about the car. In Fig. 385, a 
commercial-vehicle frame which brings out this point is shown. 
The main sills are 6-inch channels, while all of the other members 
are correspondingly large angles and channels. In one place the section 
consists of a box shape made up by bolting two large channels together, 
with the open sides in. The total overall length is not given, since 
this differs according to the variations in the wheel base; but, by a 
comparison of the figures given, it is seen that the frame shown is in 

Fig. 386. Solid Rear Construction of Locomobile for Tires and Tanks 
Courtesy of Locomobile Company of America, Bridgeport, Connecticut 

excess of 210 inches long by about 37 inches outside width. This is 
about twice the total length of the average small car. 

In the bracing and arrangement of the different members, this 
frame shows other points of difference, the cross-members, for 
instance, being nine in number, not including the two diagonal 
cross-members. The longitudinal members, too, are eight in number, 
not counting the two diagonals. 

Rear-End Changes. The locating of the fuel tank at the rear of 
the chassis — a practice that was brought into favor largely through 
the introduction of the vacuum system of fuel supply — has resulted 
in a number of changes to the rear ends of frames. The placing of 
the fuel tank at the rear is not new, and probably it would not have 


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occasioned any change to the rear end of the frame were it not largely 
for the fact that the spare tires are now carried at the rear of the 
chassis. The tires themselves are not heavy enough to make it 

Fig. 387. Sketch of Rear-End Construction of Reo Car 

essential to strengthen the rear ends, but the very general use of 
carrying the spares inflated on demountable rims has added consid- 
erable weight to the rear of the chassis. This weight, coupled with 

JPrarst Plug 

Fig. 388. Typical Rear-End Construction, Carrying Gasoline Tank 

that of a large fuel tank, has compelled makers to give more attention 
to the rear construction. 

Provision is made for carrying the spare tires on the Locomobile 
chassis by means of an apron conforming in shape to the shoe. The 
three-quarter elliptic springs of the scroll type have ends attached to 
the outside of the main frame, which is carried back and serves as an 


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extension for attaching the fuel tank. A cross-member is also utilized ; 
iff serves as a point of attachment for the two rods supporting the 
lower apron and for two upper rods as well. This design has merits 
in that the tire carrier is firmly anchored and serves to protect the 
fuel tank from injury possible in operating in crowding traffic where 
rear-end collisions are not uncommon. As may be noted, Fig. 386 
shows the method of using an upper cross-member to prevent theft 
of the tires. 

A different type of rear construction is shown in Fig. 387, a Reo. 
Here the rear cross-member is gusseted, and a pair of substantial arms 
are riveted to the cross-member. These arms serve as an anchorage 
for the tire holders which, in turn, have a crof:s-rod for protection. 
Still another design is shown in Fig. 388. Here the side rail of the 
frame projects back of the rear cross-member of the frame for a dis- 
tance of about 12 inches. The fuel tank is suspended from these two 
extended frame members by means of steel straps which pass around 
the tank. 


The more usual troubles which the repair man will encounter 
are sagging in the middle; fracture in the middle at some heavily 
loaded point or at some unusually large hole or series of holes; 
twisting or other distortion due to accidents; bending or fracture 
of a sub-frame or cross-member; bending or fracture at a point 
where the frame is turned sharply inward, outward, upward, or 

Sagging. A frame sags in the middle for one of two reasons, 
either the original frame was not strong enough to sustain the load 
or the frame was strong enough normally, but an abnormal load was 
carried, which broke it down. Sometimes a frame which was large 
enough originally and which has not been overloaded will fail 
through crystallization or, in more common terms, fatigue of the 
steel. This occurs so seldom, and then only on very old frames, 
that it cannot be classed as a "usual" trouble; moreover, it cannot 
be fixed. 

When a frame sags in the middle, the amount of the sag deter- 
mines the method of repair. For a moderate sag, say \ to \ inch, 
a good plan is to add truss rods, one on either side. These should 
be stout bars, well anchored near the ends of the frame and at points 


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where the frame has not been weakened by excessive drilling. They 
should be given a flattened U-shape, with two (or more) uprights 
down from the frame between them. The material for them should 
be stiff enough and strong enough to withstand bending and should 
be firmly fastened to the under side of the frame. The truss rods 
should be made in two parts with a turnbuckle to unite them, the 
ends being threaded right and left to receive the turnbuckle. 
When truss rods are put on a sagged frame, it should be turned 
over and loaded on the under side; then the turnbuckles should be 
pulled up so as to force the middle or sagged part upward a fraction 
of an inch, say f to J inch, and then the frame turned back, the 
other parts added, and the whole returned to use. A job of this 
kind whicR takes out the sag so that it does not recur is a job to be 

proud of. 

Fracture. Many frames 
break because too much metal 
was drilled out at one place. 
Fig. 389 shows a case of this 
kind. The two holes were 
drilled, one above the other, 
for the attachment of some 
part, and were made too large. 
They were so large that at 
this particular point there was 
not enough metal left to carry the load, and the frame broke, as indi- 
cated, between the two holes and also above and below. A break of 
this kind can be repaired in two good ways. The first and simplest, 
as well as the least expensive, is to take a piece of frame 10 to 12 
inches long, of sufficiently small section to fit tightly inside this one. 
Drive it into the inside of the main frame at the break, rivet it in 
place firmly throughout its length, and then drill the desired holes 
through both thicknesses of metal. 

This is not as good as welding. A break of this kind can be 
taken to a good autogenous welder who will widen out and clean the 
crack, fill it full of new metal, fuse that into intimate contact with the 
surrounding metal, and do so neat and clean a piece of work that one 
would never know it had been broken. When a welding job is done 
on a break like this, and no metal added besides that needed to fill the 

Fig. 389. Reboring Cracked Steel Channel 


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crack, subsequent drilling should be at an angle, to avoid a repetition 
of the overloading condition. In the figure, the dotted lines suggest 
the drilling. By staggering the holes in this way, there is a greater 
amount of metal to resist breakage than would be the case with one 
hole above the other — a method which might preferably have been 
used in the first place. 

So much welding is done now, and so many people know of its 
advantages, that every repair shop of any size should have a weld- 
ing outfit. A frame job is essentially an inside bench job, but a 
large number of cases of welding could be done directly on the car 
outside the building, particularly in summer when the outside air 
and cooling breezes are desirable. So, it is well to construct a small 
truck on which to keep the 
oxygen tank, acetylene cylin- 
der, nozzle for working, and a 
fire extinguisher. One form 
of a truck is shown in Fig. 
390. This truck is a simple 
rectangular platform with 
casters, a handle, and a rack 
to hold the tanks. It saves 
many steps and is particu- 
larly convenient in summer 
months. This outfit is essen- 
tially a home-made affair, but _. onn _ . „ . . . 

* # ' Fig. 390. Handy Oxy-Acetylene Outfit 

the gas-welding and electric- 
welding manufacturing companies have designed small outfits espe- 
cially for automobile repair work, which would be preferable to the one 
in Fig. 390, especially where the amount of repair work warrants a 
reasonable expenditure for a welding outfit. A description of both gas 
and electric outfits and instructions for their use are given in the 
section on Oxy-acetylene Welding Practice. 

Riveting Frames. Tightening Rivets. Rivets securing the cor- 
ners of a frame or holding cross-members, gussets, and plates often 
work loose, particularly with the flexible type of frame previously 
alluded to. The location of the rivet and the accessibility of the part 
will determine how best to proceed with the work. The chief trouble 
experienced is that of placing a sufficiently solid article against the rivet 





while the other end is being hammered. As a rule, old axles, sledges, 
and hammers will serve under ordinary conditions, but these cannot 
always be used in a channel frame. One method is to employ an old 
anvil which is turned upside down and so placed in the frame that the 
flat end of the anvil is placed against the head of the rivet, while a rivet 
set is employed to set the rivet up snug. The horn of the anvil is 
allowed to rest on the other side of the frame. This method can be 
used for cutting off rivets as well as for tightening old ones. The anvil 
should be of sufficient length to rest on the frame as above described. 
When an anvil is not available, the following method may be used 
with success. Take a J-inch bolt and cut it off so that it will just go 
in the frame between the rivets. Slightly countersink the head of the 
bolt with a cold chisel. Put on the nut and slip in between the rivets 
and run the nut down until it expands tight in the frame. The 
depression in the head of the bolt, and the nut fitting around the oppo- 
site rivet head will keep 
it firmly in place while 
riveting. It is not always 
practical to attempt to 

tighten a rivet. The bet- 
Fig. 391. Method of Riveting Frame ^ method is to remove 

it, drill a larger hole and use a larger size rivet. Rivets are usually 
made of Norway iron. Heat to a red heat before using. 

Riveting Methods. There are two methods of riveting, the driving 
in and the backing in. The latter method is shown in Fig. 391, and 
the two plates to be riveted are drilled in the usual manner, as shown 
at A; with the rivets a trifle smaller than the hole, placed as shown 
at B. With hot riveting, the hole should be about ^ inch larger than 
the rivet, but with cold rivets, the opening should be such that the 
rivets will slide in. Instead of backing up the head of the rivet, a 
dolly is applied to the small end, as indicated at C, and the driving 
is done on the head of the rivet by a set D and a hammer. The 
energy of the hammer is applied through the set to the rivet, which is 
upset or enlarged, as it is unable to move because of the mass of metal 
in the dolly. The metal of the rivets expands sidewise at A and B, 
completely filling the space. A feature of this method is that a part 
of the hammer blow is expended in forcing the plate N into contact 
with the plate 0. The metal at B is prevented from moving sidewise 


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by a head formed at the dolly end of the rivet, and additional blows of 
the hammer tend to bring the plates closer and to hold them. The 
backing-in method is practical in making the various styles of rivet 
heads, particularly in making the thin, almost flush, head, and an 
advantage is that there 
are no reactionary 
stresses upon the thin 
head as would exist with 
the driven-in rivet. 

As there is more 
demanded of the rivet 
replacing the old mem- 
ber, it is important that 
the work be carefully 
performed. This applies 
to the holes in the plate. 
All sharp corners should 
be removed, as they af- 
ford an opportunity for the rivet to shear off by external stress 
or to fly off under internal strain. A reamer, drill, or countersink 
can be used in removing sharp corners. The face left need not be 
more than A or ts inch wide, in order to greatly strengthen the rivet 
at its weakest point, or where the head joins the body. By slightly 

Fig. 392. Adding a Truss Rod to the Front of a Weak or 

Damaged Frame to Strengthen It and Preserve 

the Radiator 

steering gea*~. 

•^SfarT-f/rtg JTTofe*~ 



Fig. 393. Bracing Fractured Frame with Bar and Turnbuckle 

chamfering the corner of the plate, the rivet is given a corresponding 
fillet, which not only increases its holding power but serves to draw 
the plates together. 

Frame Bracing Methods. There are several methods whereby a 
frame that has been injured through collision or has sagged because 


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of too light construction can be repaired. The front of the frame is 
the chief offender in this respect, and many times a leaking radiator 
is the result. When repairs to the radiator fail to cure the trouble, it 
may be assumed that the frame is at fault. A simple remedy is 
shown in Fig. 392 and consists in bracing the frame by means of a rod 
and turnbuckle. The rod should be about 2 inches longer than the 
width of the frame and threaded for about 3 inches on each end. 
The turnbuckle is not essential, but it simplifies the work. In 
installing the brace, the inside nuts are screwed on first and far enough 
to allow putting the rod in place. These nuts are next screwed out 
until they bear against the frame, and the latter is forced out until 
any pressure that may have existed on the radiator is eliminated. 
The outside nuts are then screwed up snug. The advantage of the 
turnbuckle is that adjustments may be made as required. 

Fig. 393 shows a method of trussing a frame that was fractured 
by the stresses of the motor starter. Even after the fracture had 
been repaired, the driving gear of the starter would not mesh properly 
with the ring gear on the flywheel of the engine. As the movement 
was up and down on the frame, a truss was found necessary; while it 
was a simple matter to attach one end of the truss on the left-hand side 
of the chassis, the right-hand side was more difficult because of the 
proximity of the ball arm of the steering-gear lever. The problem 
was solved by forming a loop at one end of the truss of sufficient width 
and length to permit travel of the ball arm. By utilizing a turn- 
buckle the desired tension was obtained. 


Basis of Classification. The springs are important components 
of the chassis; for while the frame supports the power plant, clutch, and 
gearset, it is, in turn, supported upon the springs. The tendency at 
present is to design the frame and spring suspension so that the rear 
springs are placed very close to the rear wheels. In some cases, the 
frame is wide at the rear and is directly over the springs. Springs 
may be divided into seven general classes as follows: semi-elliptic, 
the full-elliptic, the three-quarter elliptic, the platform type, the 
cantilever, the quarter-elliptic, the coil, and combinations of these. 
The full-elliptic spring is made up of two sets of flat plates, slightly 
bowed away from each other at the center and attached together at 


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the ends. When these are used, the centers of the springs are attached 
top and bottom, respectively, to the frame and axle. With half of 
the top of the spring cut away, and the cut, or thick, end attached to 
the frame, this spring becomes a three-quarter elliptic. When the 
whole top of the spring is cut away, so that the spring is but a series 
of flat plates, bowed to a long radius, this becomes a semi-elliptic 
spring. By turning the semi-elliptic spring over, it becomes a canti- 

Fig. 394. Typical Semi-Elliptic Front Spring 

lever when its center and one end are attached and the load applied 
to the other end. The quarter-elliptic is but a quarter of a spring, 
while the platform consists of three semi-elliptics — two as side mem- 
bers in the regular position, while the third is used as a cross-spring, 
being inverted and attached at the center to the rear end of the frame 
and at its ends to the side members. The coil form requires no expla- 
nation and is not now used on cars. In addition, these forms are 
modified by scroll ends and various attachments. 

Fig. 395. Typical Full-Elliptic Front or Rear Spring 

Semi-Elliptic. Fig. 394 shows a front spring of the semi-elliptic 
type, the form which is used now for almost every front spring. 
This is a working spring of the usual type, fixed at the front end, 
shackled at the rear end, attached to the axle in two places, and with 
two rebound clips in addition. The latter are put on the springs 
to prevent them from rebounding too far, in the case of a very deep 
drop. In some cases, as high as four, six, or eight of these clips may 


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be used. Many other springs are made with ears, these being clipped 
over the next lower spring plate, the final result being the same as the 
use of many clips, but with improved appearance. 

Full-Elliptic. Full-elliptic springs are the oldest form known. 
Fig. 395 shows the construction of this type, the upper and lower parts 
being pivotally connected at the ends. A slight modification of this 
form, known as the scroll-end full-elliptic type, is in more extensive 

Fig. 396. Full-Elliptic Spring with Scroll Ends 

use than the full-elliptic plain type. As Fig. 396 shows, the ends of the 
upper leaves are bent over. Each carries an eye, which is connected to 
the eye in the end of the upper leaves of the lower half of the spring by 
means of a shackle. This construction makes a very soft-riding spring. 
Three-Quarter Elliptic Very much like Fig. 396 is the form 
known as the three-quarter elliptic spring, the one having scroll ends 
being shown in Fig. 397. This form of spring is fastened at three 

Fig. 397. Three-Quarter Elliptic Rear Spring with Scroll Ends 

points. The lower part of the spring is shackled at the front end, 
fixed to the axle at the center, and shackled to the upper part of the 
spring at the rear. The upper part of the spring is fixed to the frame at 
the upper front end and shackled to the lower part at the rear. Fig. 407 
shows another example of the three-quarter elliptic spring, which may 
differ in practice, as some three-quarter springs are not scroll ended. 
This form of spring is growing in favor daily, a greater number 
being used this year than last, while designs for next year show a still 


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greater increase. One reason for this increase is the great increase in 
the number of dropped frames, that is, frames unswept at the rear. To 
this form of frame, the three-quarter elliptic spring is very well adapted 
and makes a very natural, very good, and very easy-riding combination. 
Platform. The platform type of spring is used a great deal on 
large cars, as well as on very- heavy trucks, on account of its ability 
to carry heavy loads well, and also on account of its flexibility. 
As may be seen in Fig. 398, it consists of three semi-elliptic springs 
shackled together at the corners. The rear cross-spring is usually 
made shorter than the two side springs, while the latter are set off 
center, making the front of the spring, that is, the part forward of 
the point of attachment to the axle longer than the part to the rear. 
There are two reasons for this: First, the front end acts somewhat 
as a radius rod, the rear end of the frame rising in an arc of a circle 
whose radius is the front half of the spring; second, this plan dis- 

Fig. 398. Platform Springs, Showing How Side- and Cross-Springs Are Shackled Togeuier 

tributes the spring action equally in front of and back of the axle. 
Since the rear cross-spring is fastened to the frame in the center, 
each half of it is considered as a part of the side spring to which it is 
shackled. Thus, the total length of the side spring in front of the 
axle is the measured length of the side spring, while the total length 
of the side spring back of the axle is considered as the side length 
plus half of the cross-spring length. The center point, or point of 
axle attachment, is not moved so far forward as to make 'these two 
lengths equal, but in a proportion which may be derived thus: Assume 
a side spring 42 inches long and a cross-spring 35 inches long; then the 
spring would be set out of center some 4§ inches, making the front 
length about 25? inches, while the rear length would be 16^ inches 'plus 
half of the rear spring, or 17? inches, making a total of 34 inches. 
This would give a ratio of 25? to 34, or 1 to 1.333. If the side mem- 
bers were 50 inches, the ratio would be about 1 to 1.25, arid for side 
members shorter than 42, the ratio would be about 1 to 1.5. 


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Cantilever. The cantilever is, in appearance, a semi-elliptic 
spring turned over. It gets its name, however, from the method of 
suspension, which is quite different from that of any form of semi- 
elliptic spring. Moreover, as a part of this suspension, at least one 

Fig. 399. Cantilever Rear Spring Used on King Cars 
Courtesy of King Motor Car Company, Detroit, Michigan 

end of the cantilever and sometimes two are finished up flat and 
square to slide back and forth in a groove provided for that purpose, a 
bolt through a central hole preventing the spring from coming out of 
its guide. One form, shown in Fig. 399, has a fixed attachment 
to the rear axle, a pivoted attachment to the frame at its center 

Fig. 400. Front End of Cantilever Spring on Siddeley-Deasy (English) Car 

(or slightly beyond the center), and a sliding attachment to the frame 
at its forward end to take care of the increase in length and of the 
forward movement necessary when the rear wheels rise. 

Another form of cantilever is that shown in Fig. 400. This is 
the rear spring on the Siddeley-Deasy (English) car and, like that of 


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the King, is pivotally mounted on the frame just forward of its center. 
Unlike the King, however, the forward end of the spring has a shackle 
which permits it to swing when the rear axle rises or falls. This 
shackle is a very interesting feature of this installation, having an 
adjustment which is most unusual for a shackle, Fig. 401 . Note how the 
outsides of the shackle 
have a series of grooves, 
into which the head of 
the shackle bolt on one 
side and the washer on 
the other, fit. By setting 
these in the desired 
grooves and tightening 
the nut, the position is 
fixed. If this does not 
give the proper throw, it 
is a simple matter to re- 
move the nut and make 

a new adjustment. 3^ 401 Detail of the Adjustable Shackle on Siddeley 

In France, a form Of Cantilever Spring 

double cantilever has been tried out with success; this form consists of 
a pair of cantilevers, one above the other, separated at the center by a 
carefully sized spacing block, which is pivotally attached to the frame. 
The rear ends are attached above and below the axle, while the front 

Fig. 402. Illustration of Hotchkiss Drive 

ends are attached to two fixed points. Although the ends are made 
much thinner and more flexible than those just shown, it should be 
noted that both of them are fixed. The rise and fall of the wheels 
must be taken up by the springs themselves, the pivot in the center 
simply distributing the distortion over both the front and rear halves. 


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Advantages of Cantilever. The advantages of the cantilever 
spring are the smaller unsprung weight and the reduced manufac- 
turing cost for a given amount of flexibility. Another advantage is 
the absence of sharp rebounds and a greater deflection for a given 
load and length of spring; it also obviates the cut in the body required 
with the three-quarter elliptic spring. When the cantilever takes the 
driving strain, the main leaf is usually stiffened and, being stronger 
sidewise, it eliminates a good deal of the side sway. With torque 
rods, the main lead may be made lighter, as the starting, the braking, 

Fig. 403. Unique Rear Spring of Marmon Cars 

and the torque act through the torque rods. Since there is more 
metal in the line to the thrust, they are especially suitable for taking 
the thrust, and not quite as efficient in taking the torque. 

Ho tchkiss Drive. The adoption in 1915 of the Hotchkiss drive, 
Fig. 402 in which the rear axle is connected with the frame through 
the chassis springs only, making the springs perform the functions of 
torque and thrust, is a radical departure from previous forms. The 
objection that it subjected the springs to unnecessary strains has not 
been sustained in practice, which has shown that a slight yielding of 
the rear axle when starting and braking, by a certain flexure in the 
springs, has reduced the stresses upon the transmission members. 


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In the Hotchkiss drive, the springs are rigidly attached to the rear 
axle, while the front end of the spring is secured to the frame with a 
proportionately large bolt through which the drive is transmitted. 
Users of the drive claim that it is quieter, that the car holds the road 
better, that it is more flexible, and that it avoids the road shocks 
which are transmitted through stiff torque members from the axle 
to the frame. Makers who drive through the springs and employ 
other torque members claim that they are not sacrificing flexibility in 
driving while eliminating a certain side sway and other strains preva- 

Fig. 404. Combination Cantilever and Semi-Elliptic Spring on Tractor 

lent when the springs perform the functions of the torque. In the 
Hotchkiss drive, two universal joints in the drive shaft are used. 

Unconventional Types. Marmon. A departure from conven- 
tional practice is the spring used on the Marmon car and shown in 
Fig. 403. It is a double-transverse construction, consisting of semi- 
elliptic springs bolted together at the center, with a curved block, or 
hard-maple cam, between them. This cam varies their stiffness, 
the spring automatically becoming stiffer as the load increases. 
Under normal load, the stiffness is about 170 pounds per inch, but as 
the springs are compressed the stiffness will reach 400 pounds. They 


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are shackled at one side and fixed at the other, obtaining a perfectly 
parallel motion to the frame. There is said to be no roll as is some- 
times found with transverse springs. 

Knox Tractor. An unusual method of suspension is that 
employed on the Knox tractor, a combination of a cantilever and 
semi-elliptic spring at the rear end of the frame. The design shown in 

Fig. 405. Rear Spring of Six-Ton Truck 

Fig. 404 includes heavy semi-elliptic springs, which are attached to 
the rear axle by long clips and carry the fifth wheel of the trailer. 
There is no connection between the springs and the tractor frame, so 
they carry the weight of the trailer and load only. The tractor frame 
is mounted on a cantilever spring having a pivot near its center and a 
shackle at the front end. The rear end bears on a seat clipped to the 

rear axle. This obtains a 
flexible mounting for the 
tractor and also permits 
the carrying of very 
heavy loads on the 

Semi-Elliptic Truck 
Spring. The semi-elliptic 
spring is a favorite with 
makers of commercial 
vehicles. It is simple, 
and if the length, width, and other dimensions are proportioned 
correctly, it is a most satisfactory method for both front and rear 
suspension. Fig. 405 shows a rear spring for a 6-ton truck, the 
method of shackling, and how it is mounted on the axle by means 
of a spring seat. 

Fig. 408. Overland Four-Spring Assembly 


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Many makers are now using their own special form of springs. 
Fig. 406 shows the spring arrangement used on the Overland Four, a 
type that may be described as a three-point suspension. It was made 
In two parts, the lower part consisting of a regular semi-elliptic flat 
spring, while the upper part was a semi-elliptic flat spring with scroll 
ends. The central part of the spring was treated as one, being 
attached to the axle in the usual manner; the ends, however, had a 
peculiar appearance, because the upper and lower halves of the spring 
were of different shape. The scroll end of the upper part was sup- 
posed in itself to absorb many of the small road shocks. The spring 
was loosely attached to the frame at each end by means of a double 

shackle, made necessary by the double action of the spring; the tend- 
ency to flatten out increased its length, thus calling for a forward * 
motion of the front and a backward motion of the rear ends, while the 
different lengthening action, owing to the difference in the lengths of 
the two parts of the spring itself, resulted in a turning about a different 

In the latest form of spring construction on the Winton car 
Fig. 407, it will be seen that the three-quarter elliptic form has 
been adopted, with a kick-up at the rear end of the frame. If 
the two types are compared somewhat closely, it will be seen that 
the only change in the frame part is the kick-up. The new springs 
show the scroll ends to which Winton has always been partial. 


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Ford. The form of the Ford spring has always been distinctly 
different. Fig. 408 shows the front and Fig. 409 the rear spring used 
on Ford cars, the distinction in the front spring being principally 
in the use of a single ordinary inverted front spring set across the 
frame on top of the axle, where most makers use a pair of side springs 
set parallel to the frame. This form is simple and cheap to make 
and assemble, the cost of the spring itself, and the work of putting 

Fig. 408. Special Vanadium Front Springs for Ford Cars 
Courtesy of Ford Motor Company, Detroit, Michigan 

it on being just about half that of the spring attachment of the 
ordinary two-spring type. On the other hand, excellent riding quali- 
ties are claimed for it. A second distinction is that the spring is 
an inversion of the usual semi-elliptic type, the set of the spring 
being downward instead of upward. A third claim to distinction is 
in the use of vanadium steel, which, it is claimed, has a higher tensile 
and compressive strength than any other steel, and it is practically 
unbreakable in torsion. This steel is also being used in many other 

Fig. 409. Rear Springs of the Ford Car 

parts, such as crankshafts, camshafts, fender irons, frames, drive- 
shafts, etc., resulting in a very light-weight car, since the greater 
strength of the material allows the use of smaller sections for equiva- 
lent strength. 

The Ford rear spring has all the claims to distinction of the 
front spring, and, in addition, a hump at the center. Fig. 409 shows 
this hump clearly, the rear-frame cross-member being only partly 
shown. It will be noted that both ends of both springs are shackled, 


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the construction necessitating it. These springs represent quite a 
radical departure, the success of which has been proved in actual 

Locomobile. Fig. 410 shows the three-quarter scroll elliptic rear 
spring used on the Locomobile, also the method of shackling both ends 

Fig. 410. Three-Quarter Scroll Elliptic Spring Used on Locomobile Cars 

of the spring, and the use of a considerable extension beyond the spring 
clip of the two upper leaves. Fig. 411 illustrates the Locomobile 
front springs, the upper spring being used on the 1916 model, and the 
lower one on the 1917 model. As may be noted, the later type is 
2 inches longer and also flatter, and the distance between the spring 

Fig. 411. Two Sets of Front- Axle Springs on Locomobile Cars 

bolt and eye of the shackle is less in proportion to the 1916 design. It 
was found that the jerky action and fore-and-aft pitching of the axle 
were eliminated by this construction, greatly improving the riding 
qualities of the vehicle. 

Electric Car Springs. The spring suspension of electric pleasure 
cars is similar to that of the gasoline vehicle, semi-elliptic suspension 

185 Digitized by 



in front, and full-elliptic scroll-end suspension at the rear. The 
method of shackling is similar. 

Varying Methods of Attaching Springs. Springs are attached 
in many ways. For example, the one shown in Fig. 398 might be 
shackled at the front end, fixed to the axle, and fixed to the center 
of the frame at the rear, the side and cross-springs being shackled 
together. Again, the front end might be fixed to the frame, Fig. 412, 
all other connections being unchanged. Or, with either method of 
fixing the front end, the spring might be swiveled on the axle, so as 
to be free to give sidewise without changing the other properties of 
the spring. Or, with either method of fixing the front end of the 
spring, and with or without the axle swivel, the cross-spring might 
be pivoted at the central point so as to be free to turn in any direction 

Fig. 412. Special Type of Double Quarter-Elliptic Rear Spring 

about this central point. This latter method prevents binding and 
unequal spring action when one side of the frame is unduly raised 
or depressed, the solid method of fixing the rear end resulting in a 
double action on the part of one spring, owing partly to the tilting of 
the body and partly to spring action itself. With the pivot joint, the 
spring first swings about this point until a position of equilibrium is 
established, when the suppleness of the spring comes into action, the 
result being a deflection of half what it would be in the other case. 

This form of spring also is used with the spiral spring, the 
latter taking the place of the shackle between the side and rear 
members. In this position it serves two purposes: (1) as a 
connector, taking the place of and doing the work of a shackle, 
thus acting as a universal and swinging joint between the two 
springs; (2) as a shock absorber, taking up road shocks within 


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its length, that is, in the coils, without transferring any of them to 
the body proper or, in case of heavier shocks, sharing with the side 
and rear springs. This, of course, is the true function of the 
springs — to allow the road wheels to pass over the inequalities, 
rising and falling as may be necessary, while the body travels along 
in a straight line, level and parallel with the general course of the road. 
Underslinging. Almost any of the spring forms shown and 
described may be underslung, that is, attached to the axle from 
below. This is a quite common practice for semi-elliptic springs when 
used in the rear, but it is very uncommon for front springs. Similarly, 
full elliptics, whether having scroll ends or not, are frequently under- 

Fig. 413. Rear-Spring Arrangement on 1917 Premier 

slung. The three-quarter elliptic form when used in the rear is 
usually underslung; the platform spring is not underslung so often. 
The cantilever and quarter-elliptic springs have been mentioned in 
connection with the underneath attachment. It should be pointed 
out that the position beneath the axle lowers the center of gravity by 
an amount equal to the thickness of the spring plus the diameter of 
the axle plus twice the thickness of the attaching means, and this, too, 
without interfering with the quality or quantity of the spring action. 
In the case of the cantilever, the effect of underslinging is to reduce the 
straightness of the spring, that is, the form when attached above 
the axle is almost straight, while the form when fastened below the 
axle is very much curvea- has considerable "opening". 


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Shackles and Spring Horns. Considerable improvement has 
taken place in the method of shackling springs, and provision is now 
made with some types of springs for the adjustment of the shackles 
and hangers as well as for renewing bushings. Reference has been 
made to the tendency of design in rear-spring suspension and to the 
underslung types. Fig. 413 shows the design employed with the 1917 
Premier, and, as may be noted, the springs are slightly diagonal, the 
front ends coming inside the frame line, while the rearends are attached 
to goose necks of a rear extension of the frame pieces. Shackles are 
used for connecting the ends of the springs to the extensions. 

Departing from the conventional shackle was the safety double 
shackle used on the Rainer 1000-pound capacity delivery car, shown 
in Fig. 414. In addition to the main eye on the main leaf of the rear 

spring, the second leaf is extended 
and formed into an elongated eye, 
allowance being made for deflection 
under load. The eye of the leaf is 
attached to the frame by the usual 
rigid spring bolt. Additional means 
of support are furnished by clamps 
on either side of the spring, one by a 
pin through the elongated eye, and 
Fig. 414. Double shackle Used on Rainer the other by a pin through the lower 

Delivery Car ^ q{ ^ damp which ^^ ^ ^ 

third and fourth leaves. It is pointed out that in case the main leaf 
breaks the eye of the second becomes the driving eye, and should 
this break, the spring will wedge between the under pin and the 
upper part of the clamp, thus obtaining rigidity which is essential 
with the Hotchkiss method of drive. 

Although the general practice is to shackle the semi-elliptic front 
spring at its rear, a departure which places the shackle at the spring 
horn or in front is noted in the Manly truck. 

Adjusting Spring Hangers. The type of front-spring hanger, 
shown in Fig. 415, is adjustable. This adjustability is accomplished 
by relieving the body of the grease cup and screwing in the slotted 
bolt which eliminates side play. The grease cup body acts as a lock 
nut. The rear hanger of the front spring, Fig. 416, is adjusted by 
loosening the inside lock nut and the body of the grease cup. After 


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removing the cap of the grease cup, the hanger bolt is turned out, or 
to the left, with a screwdriver, decreasing the distance between the 
links. The grease-cup body and lock nut are then set up tight. 

Fig. 415. Section of Adjustable Front-Spring Hanger 

Provision is made with some types of rear springs for eliminating 
play when the rear ends are mounted on seats. 

Spring Lubrication. All springs now are fairly well lubricated. 
All shackles are provided with grease cups, and other points of attach- 
ment to the frame are provided with oil holes. Where the springs are 
pivoted either on frame or axle, a big grease cup is usually furnished. 
In addition, it is now realized that the maker can prevent much of 
the noise formerly coming 
from dry and perhaps rusted fTf I r Mon9er Dott 
steel spring plates working 
over, each other. There are 
several ways in which oiling 
is accomplished. The springs 
are made with an internal 
lip, or groove, which is filled 
with lubricant when they are 
assembled; or between each 
pair of spring leaves is placed 
an insert having a series of oil pockets throughout its length, each 
filled with lubricant normally held in by means of a membrane cover; 
,the movement of the spring plates and the heat generated thereby 

Section of Rear-Spring Hanger 


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starts the lubricant flowing to all parts. An even later method is 
the attachment of external cups, provided with a wick which goes 
around the spring leaves and is pressed against their sides. The 
wick is kept wet with lubricant from the cups, and the motion of 
the spring leaves, together with the capillary action in the wick, 
draws the oil in between the leaves. 

Spring Construction and Materials. A study of the illustrations 
used will show that practically all modern springs are clipped together, 
the number of these clips varying with the length of the spring and the 
use to which it will be subjected. Thus, Winton, Fig. 407, shows 
three clips and a band. Some springs show as many as five clips and 
two bands. But none indicate the use of spring ears — very small pro- 
jections on the ends of the leaves — which are bent over the edge of the 
leaf next below it to assist in holding the spring together, but they 
are in quite general use. Altogether, there are about 14 or 15 forms 
of spring-leaf ends, but those in general use may be reduced to seven. 
These are: the oval; the round point; the short French point, a modi- 
fication of the oval; the round end with slot and bead; the ribbed 
form, widely used on motor trucks; the square point tapered; and 
the diamond point. 

In addition, sizes have been standardized in America to the 
extent that only five widths are used for pleasure cars and seven for 
motor trucks. Those for the former are: 1^, If, 2, 2\, and 2\ inches; 
for the latter: 2, 2\, 2\, 3, 3£, 4, and 4^ inches. 

As the automobile business has called for better stand-up 
qualities under more severe conditions of use, the quality of steel 
used has been greatly improved, and other materials are better. The 
French make excellent springs, many of our best automobile manu- 
facturers going abroad for their springs for this reason, but American 
springs are improving in quality so rapidly that this is becoming 
unnecessary. Formerly, all springs were of a plain carbon stock, but 
now a great deal of silicon, manganese, and vanadium steel are being 
used. Some chrome and chrome-nickel steel have also been tried. 


Usual Spring Troubles. Lubrication. The average repair man 
is likely to have more call to lubricate the leaves of a spring than any 
other one thing in connection with springs. True, they lose their 


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temper; they sag and show signs of losing their set; plates break in the 
middle, at the bolt hole, and near the ends of the top plate; and inside 
plates break in odd places. But more frequently the springs make an 
annoying noise, a perceptible squeak, because the plates have become 
dry and need lubricating. When this happens, and the up or down 
movement of the car rubs the plates over each other, dry metal is 
forcibly drawn over other dry metal with which it is held in close 
contact; naturally, a noise occurs. 

To lubricate the spring, it is well to construct a spring-leaf 
spreader. Of course, the job is best done by jacking up the frame, 
dismounting the spring entirely, taking it apart and greasing each 
side of each plate thoroughly with a good graphite grease, then 

Fig. 417. Handy Tools for Spreading Spring Leaves to Insert Lubricant 

reassembling it, and putting it back under the car. This is the best 
way, but it costs the most, and few people will have it done. Some- 
times spring inserts are used; these are thin sheets of metal of the 
width and length of the spring plates, having holes filled with lubri- 
cant over which is a porous membrane. 

For the ordinary spreading job, the plates must be pried apart 
and the grease inserted with a thin blade of steel, for instance, a 
long-bladed knife. To spread the leaves, jack up the frame so as 
to take off the load, then insert a thin point and force it between a 
pair of leaves. In Fig. 417, two forms of tools for making this forcible 
separation are shown. The first is a solid one-piece forging with 
the edges hardened. It is used by sliding the edges over the ends 
of the spring leaf, then giving it a twist to force it in between them, 


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as shown in the figures. The second tool is intended to be forced 
between two plates by drawing back on the handle. 

Tempering or Resetting Springs. When springs lose their 
temper or require resetting, it is better for the average repair man 
to take them to a spring maker. Tempering springs is a difficult job, 
as it requires more than ordinary knowledge of springs, their manufac- 
ture, hardening, annealing, etc. When springs are in this condition, 
they sag down under load and have no resiliency. If a great many 
springs are handled, a rack like that shown in Fig. 418 is well worth 

Broken Springs. When springs break, there is but one shop 
remedy — a new plate or plates. But when they break on the road, 
it is necessary to get home. When the top plate breaks near the 

Fig. 418. Simple and Well-Designed Spring Rack 

shackled end, repair this sufficiently to get home by using a flat wide 
bar with a hole in one end big enough to take the shackle bolt; bolt 
this bar to the spring in place of the end of the leaf which is broken. 

General Hints on Spring Repairs. As a rule, a break in a plate 
takes place where it does not prevent operating the vehicle, but it 
should be borne in mind that the damage to the plate subjects the 
other plates to extra work, and, unless the broken member be properly 
repaired or replaced, the others are likely to break. If one of the 
intermediate plates breaks in the center at the bolt, tighten the spring 
clips as much as possible. Very frequently the rebound clips will be 
found to be loose, and missing clips also contribute to spring breakage. 

The removal of a plate from or addition to a set is very likely to 
upset the grading of the construction. It is not practical to replace a 
broken plate with a new one because it is of the same width and thick- 




ness, but an expert spring maker should be called in to see that the set, 
or fit, is correct. The fitting of a leaf requires the services of an 
expert spring man; while it appears to be a simple matter, the lack 
of knowledge by some claiming to be spring experts is responsible for 
breakage after the spring has been repaired. The spring clips and the 
nut of the center bolt should be kept tight. The importance of 
preventing the accumulation of rust on the leaves and of lubrication 
has been commented upon. 


Function. The ordinary flat-leaf springs of any of the types 
previously described are inadequate for automobile suspensions. 
When the springs are made sufficiently stiff to carry the load properly 
over the small inequalities of ordinary roads, they are too stiff to 
respond readily to the larger bumps. The result is a shock, or jounce, 
to the passengers. When the springs are made lighter and more 
flexible in order to minimize the larger shocks, the smaller ones have 
too large an influence, thus keeping the body and its passengers in 
motion all the time. These two contradictory conditions have created 
the field for the shock absorber. 

The shock absorber is generally a form of auxiliary spring, the 
function of which is to absorb the larger shocks, leaving the main 
springs to carry the ordinary small recoils in the usual manner; in 
short, to lengthen the period of shock. This is done in a variety of 
ways, and, as might be expected, by a great variety of devices. 

General Classes of Absorbers. The simplest forms of absorbers 
are the ordinary bumper, or buffer, of rubber and the simple endless 
belt, or strap, encircling the axle and some part of the frame and 
acting as the rubber pad does — simply as a buffer. There are the 
following classes of the more complicated shock-preventing and shock- 
absorbing devices: (1) frictional-plate or cam, in which the rotation of a 
pair of flat plates pressed together tightly — one attached to the frame, 
the other to the axle — opposes any quick movement of the two or of 
either one relative to the other; (2) a coil spring used alone and in 
combination — alone it is used in the plane of the coil, or at right 
angles to it, and parallel to the center line about which the coil is 
wound, while in combination it is found joined with the simple leather 
strap or with another coil spring of equal or sometimes of less 


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strength, in the latter case the weaker one acting with the main 
springs; (3) the flat-leaf spring, a more simple description of which 
would be a small duplicate of the main semi-elliptic spring set on it so 
as to oppose its action; (4) the air cushion; and (5) the liquid device, 
in simple form and in combination with some one or more of the coil- 
spring forms. 

Frictional=Plate Type. A frictional-plate type of shock absorber 
is shown in Fig. 419. This absorber consists of an upper arm attached 
to the frame, having at its outer end a frictional plate in contact with a 
similar plate at the upper and outer end of the other arm pivoted to 

the axle. The two plates are 
pressed together by means of the 
nut shown in the center; this nut 
is resisted by the spring beneath 
it and the slightly arched surfaces 
of the plates. When a sudden 
bump raises the axle, it must 
turn the two faces of metal across 
each other to the limit before it 
can lift the body. As will be 
seen, this means a considerable 
distance, and it can be made 
relatively greater by clamping the 
nut up tighter, thus increasing the 
friction between the surfaces, and, 
Fig. 419. Hartford^ Governed^^Friction Type therefore, requiring greater force 

Courtesy of Hartford Suspension Company, to turn them. Because of this 

Jersey City, New Jersey . . 

adjustable quantity of friction, 
this type is called the governed friction type. 

When cams are used, practically the same result is obtained, 
except that the device is necessarily more complicated. The cam 
action usually generates some heat, and, for this reason, this form 
of shock absorber is most always enclosed, and the interior, where 
the cam works, is filled with grease or very heavy oil. 

A modification of the plain frictional-plate form is seen in Fig. 
420, which is called a passive range absorber, because, for ordinary 
movements of the springs to which it is attached, it does not come into 
action. When the usual spring action is exceeded, however, as in a 


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Fig. 420. Laporte Passive Range Friction Type of 

Shock Absorber 

Courtesy of Charles Laporte, Detroit, Michigan 

sharp jounce, the device becomes effective. It appears much like the 
Hartford just shown, but the construction is decidedly different. 
The upper, or frame, arm is threaded to receive an Acme-threaded 
screw, which is carried by the lower, or axle, arm. The action of 
screwing this out tends 
to force the plate on the 
lower arm, which must 
move outward with the 
screw against a rubber 
washer held firmly by the 
outside nut and cover 
plate. Thus, the scissors 
action of the two arms 
on a sudden movement is 
resisted by the compres- 
sion of the rubber washer. 
This compression can be 
increased or decreased by tightening or loosening the slotted outside 
nut, so that the screw is given less or more movement. The rubber 
washer is made with a series of holes in it to allow of compression. 
Coil Springs, Alone and in Combinations. Springs Alone. 
The coil-spring absorber is probably the most widely used form, 
primarily because it is 
both good and cheap; 
furthermore, it is simple 
and adds little weight. 
In most instances, the 
coil is so placed as to 
compress along the direc- 
tion of its center line. 
One device, however, the 
Acme, shown in Fig. 421, 
works at right angles to 
this. It consists of a pair 
of coils, the two ends of each being so constructed as to go on the 
ends of the shackle bolts in place of the usual shackle. When the 
shackle is removed, one pair of ends is fastened to the spring in 
place of the shackle, while the other pair of ends is fixed to the frame 


Fig. 421 

Acme Torsion Spring Fitted to Three-Quarter 
Elliptic Gears 
Courtesy of Acme Torsion Spring Company, 
Boston, Massachusetts 


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or the other part of the spring, as the case may be. Note that this 
arrangement brings one of the coils on either side of the main spring 

end, extending away from 
it in a horizontal plane. In 
this position, the torsion 
spring acts as a spring 
shackle, absorbing the 
jounces and bounces so that 
they do not reach either the 
body, the attaching point, 
or the other half of the 
spring, as the case may be. 
Fig. 422 is a simple 
coil spring of barrel shape, 
that is, the end coils are 
smaller than those in the 
Fig ' 422 ' !S^ u g£S3Sy *" Very center and are set between 

Courtesy of J. H. Soger Company, Rochester, New York frame and axle in SUch a 

way that they absorb the jounces directly. 
This is probably the simplest possible 
shock-preventing device, consisting only of 
the spring and its top frame and bottom 
axle connections. These are made in four 
sizes of wire, varying from A inch up 
to ii inch. 

In the K-W road smoother, shown in 
Fig. 423, the action of the spring is opposed 
by an air chamber at the top, creating a 
balance. A shock which causes the spring 
to move is opposed by the spring itself, 
while the rebound, or reaction, is opposed 
by the air compressed in the air chamber. 

Combinations. Probably exceeded in 

simplicity only by the two forms just shown 

is the type in which a coil spring and leather 

Fig. 423. k-w Spring Type of band, or strap, are combined. One of these, 

the Hoover, is shown in Fig. 424. It will be 
seen that the spring end is fastened to the body, while the strap is 


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attached to the lower end of the spring and encircles the axle. Hence, 
this will not interfere with upward movements of the axle, but 
only with the downward ones, that is, the axle is free to rise, but as 
soon as the car body starts to rise, the 
strap-spring combination acts to prevent 
it. This is particularly true if the axle 
has reached the limit of its motion and 
has started downward before the body 
starts upward. In that case, the body 
can move upward only the amount of 
slack in the strap plus the give of the 
spring, but minus the amount the axle 
has already moved downward. This inex- 
pensive arrangement has found great 

faVOr On Small Cars. Fig. 424. Hoover Shock Absorber, 

t\ L7 n •? o m T • a Spring and Strap Combination 

Dovhle-Loil bpring lypeS. In pnn- Courtesy of H. W. Hoover Company, 

• 1,1 ». . • • . 1 • rv New Berlin, Ohio 

ciple, the use of two springs is not differ- 
ent from the use of one. For structural reasons, however, it is easier 
to attach the two-spring form, while dividing the load up into two 
parts allows of the use of 
smaller diameters and smaller 
sizes of wire, thus making the 
device appear more compact. 
One of the two-spring forms, 
the J.H.S., is shown in Fig. 
425. It consists of a pair of 
cylinders with coil springs 
within. The tops of the two 
cylinders are joined by a pin, 
and this joining pin is attached 
to the lover leaf of the spring. 
Inside the cylinders, pistons 
are set above each spring, and 

these are Connected, this COn- Fig. 425. J.H.S. Shock Absorber Has 

. . 1 . j - . 1 Twin Springs Encased 

nection being used for the 

other half of the spring. At the bottom, the external bands on 
each of the two cylinders ase connected, so as to keep them parallel 
at all times. Thus any movement upward of the lower part of the 


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main-leaf spring tends to draw the enclosure for both shock-absorbing 
springs upward. The springs themselves resist this and absorb 
a large part of the movement both in force and distance. 

Flat=Plate Recoil Springs. The third class, or flat-leaf spring, 
is a semi-elliptic unit in miniature. It is placed upon the top of the 
ordinary semi-elliptic spring, but it is reversed and has a spacing 
plate between the two. The object of this plate is to prevent recoil 
and to eliminate the rebound of the car body without restricting the 
flexibility of the main springs. As shown in Fig. 426, the Ames 
equalizing spring is constructed along these lines. As will be noted, 
this allows all downward movement of the spring, having no influence 
thereupon; but when the recoil, the upward equal and opposite 
reaction, comes, the smaller upper spring opposes this reaction and 

Fig. 426. Ames Equalizing Spring Is a Simple Small Inverted Semi-Elliptic 
Courtesy of Clarence N. Peacock and Company, New York City 

minimizes it, so that little or none of it reaches the body or the 

Air Cushion. Perhaps the most complicated form of shock 
absorber — certainly the most expensive and at the same time the 
most efficient — is the air cushion. This form consists of a pair of tele- 
scoping cylinders one being attached to the frame and the other to the 
spring. When road obstructions cause the spring to rise, it pushes its 
cylinder upward, but this movement is resisted by the air inside of the 
cylinders. With the amount of air properly proportioned to the size 
and weight of the car and its load, all this upward movement will be 
absorbed and none will reach the body and its occupants. 

This rough outline describes the Westinghouse air spring, shown 
in cross-section in Fig. 427. In order to handle the air pressure and 
keep the cylinders within the commercial limits, oil also is used in 
the cylinders. This reduces the volume of contained air; but, for 
each inch the device is compressed, the air is reduced by a greater 
percentage of its original volume, consequently the resistance to 
compression is greater than it would be without the oil. 


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In the drawing, A is 
the upper section of the 
cushion chamber, telescop- 
ing into the lower section 
made up of tube B and 
crosshead E. The outer 
tube C is simply a guard. 
A steel casting D is bored 
out to form a guide for the 
outer tube and crosshead, 
and has a rectangular pad 
F machined for bolting the 
whole device to the bracket 
attached to the frame of the 
car. A shackle G is fastened 
to the end of the car spring / 
and is pivoted to the cross- 
head E. Packing ring H is 
used to make the inner cyl- 
inder a tight fit in the outer 
casing. A breather J is 
placed on the side, through 
which air is drawn by the 
upward movement of tube 
B through the medium of 
the tightness of packing ring 
H , just mentioned, and this 
air, on the downward move- 
ment, is forced through the 
passage K to a port partly 
surrounding the tube B. 
There is no packing ring 
between this tube and its 
guide D, so the air blows 
out and keeps the contact- 
ing surfaces clean. A fur- 
ther protection is afforded 
by the felt-wiper ring L, 


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which retains the grease in the groove just above it. is a rod con- 
necting the two front or rear springs. At the top is the screw 
cap My covering the air valve N, which is designed to be used just 
as the air valve in a tire. 

The lower part of the device is filled with oil up to a level which 
approximates the line Z, all above this level being air under pressure. 
Consequently, the device actually compresses the air through the 
medium of the oil, which is incompressible. This oil forms a seal for 
the air chamber and prevents its leakage, although the oil itself is 
allowed to leak through, this leakage being pumped back auto- 
matically by the action of the springs. This works out as follows: 

Fig. 428. Westinghouse Air Springs Applied to the Rear of Pierce limousine 

In what might be called the piston, although it is not, because it does 
not move — the other parts moving relative to it — there is the plain 
leather packing ring P and the cup leather R held out against the 
sides of the cylinder by the conical ring and spring. 

The small amount of oil which does leak past the packing rings 
P and R is caught in the annular chamber S, whence it flows down 
through the vertical (dotted) passage Q into the chamber just below 
the ball valve T. In the center is a hollow plunger U of a single- 
acting pump. This has two collars on its upper end V and W and 
between them a disc X. This almost fills the passage just above it. 
The plunger is held down by the light spiral spring shown pressing 
on the collar V. 


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When a road obstruction is met and the spring rises, crosshead 
E rises and the upward movement of the oil takes the disc X upward 
until it strikes and carries with it collar V, which lifts the plunger and 
draws in a charge of oil. When the air compressed in the upper 
chamber of the device expands, and the car spring / and crosshead 
E go down again, the oil flows in the opposite direction, carries disc 
X down against collar W, and forces the plunger downward. Then 
the oil passes the ball check F, goes through the hollow plunger, and 
is discharged back into the upper, or air, chamber. In the first place, 
the oil is put in by taking off cap M and taking out the air valve N. 
Then a special single-acting oil gun is used to force it in, a long nozzle 
being necessary to reach down into the interior, with a stop to limit 
this downward distance. The maker recommends that an excess be 
put in and then slowly drawn off to the right level. 


f>ome Cross Member- 

Fig. 429. Typical Semi-Elliptic Overload Spring 

As will be seen from the foregoing, this device is essentially an 
air spring, and the air cushion does the work; but it is the oil below 
it, with its permissible leakage and with a pump to return this leaking 
oil, which makes this device practicable. To show the exterior, 
the part which most persons would see and remember, Fig. 428 
is presented. This figure shows the rear end of a Pierce limousine 
equipped with a pair of the Westinghouse air springs. Note the 
breather, tie rod, cap at the top, cast guide at the bottom, and other 
parts previously shown and described. 

Hydraulic Suspensions. The majority of the hydraulic devices 
developed as shock absorbers consist of turning vanes connected to 
the axle or spring, enclosed in a liquid-tight case filled with some heavy 
oil. There is a hole of small diameter in the case which connects the 
two sides of the vane, its motion forcing the fluid through this hole. 


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Thus the spring action simply pumps the oil from one side of the vane 
to the other and back again, the resistance to the flow of the liquid 
past the vanes and through the small hole absorbing all of the shocks. 
Overload Springs. Overload springs are utilized with com- 
mercial vehicles and may be of either the leaf or coil type, and so 
arranged as to act only when the load on the main springs reaches a 
certain weight. The wear plate may be a separate platform, as 
shown in Fig. 429, or it may be formed integral with the pressure 
block. Where coil springs are used, they are made of square section, 
attached either to the frame cross-member or to the axle. Two such 
springs are used, one on each side. The design in Fig. 429 is a semi- 
elliptic. It is attached to a frame cross-member, and the ends are 
free so that they may make connection with a separate spring seat 
or a pad on the pressure block of the side spring when a predetermined 
load has been applied. With some trucks the front springs are 
mounted on a seat forged integral with the axle and are retained by 
box clips ;a coil spring is attached to the pressure block, which acts as a 
bumper. Under excessive deflections these springs strike the bottom 
flange of the frame and arrest the rebound motion of the vehicle 
spring. The Jeffery Quad employs* a spring bumper which is made 
of flat metal and is termed a volute spring; »It is attached to a bracket 
fastened to the pressure block. 



Q. Which wheel travels farther on curves and why? 

A. The outer wheel must travel much farther on any curve, or 
turn, because it is turning through an equal angle on a curve of much 
longer radius. On very short turns, the distance the outer wheel 
must travel can be more than 50 per cent greater, or longer, than that 
of the inner. 

Q. What general condition exists which makes the problem 
of steering so complicated to lay out? 

A. The answer to the previous question gives an idea of the 
demands on the steering gear. The difference in the distances which 
the two wheels must travel on all curves — some differences being as 
high as 50 per cent, and with the difference shifting from one side to 
the other — is the general difficulty. 


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Q. How does the usual steering arrangement care for this? 

A. By having the linkage which connects and steers the front 
wheels arranged so that a prolongation of the center lines of the two 
steering arms will pass through the center of the rear axle. 

Q. How does this solve the difficulty? 

A. When this arrangement is used, any swing or turn given to 
the steering system, say a turn to the right, will swing the left-hand 
knuckle through a larger angle than the right, although the two are 
connected together by linkage. This means that the inner, or left, 
wheel will swing about a shorter radius than the outer, or right, wheel, 
since if the two were turned through equal angles, the two radii would 
be equal. 

Q. What other items complicate this steering problem? 

A. The fact that the wheels themselves must toe in slightly at 
the front in order to steer easily and hold a straight line when set 
straight. Furthermore, the wheels must be set with their tops wider 
apart than their bottoms so that the line through the center of the 
plane of the wheel strikes the cambered, or raised, road surface at a 
right angle; this makes the whole situation even worse. 

Q. Is the ordinary front axle of such a design that it gives per- 
fect steering? 

A. No. But it represents a working approximation which could 
not be improved upon without many needless complications. On a 
sharp turn, probably one wheel is dragged around the curve for a 
small portion of its length, but the distance is so small that it would 
never be noticed by the eye nor discovered in any difference of life 
in the tires. 

Q. How is the turning of the steering knuckles about their 
pivots obtained? 

A. The swinging movement of the steering knuckles is obtained 
through a fore-and-aft movement of the steering rod connected up to 
one of the steering-knuckle arms by a ball joint. 

Q. How is this longitudinal movement of the steering rod 

A. By a fore-and-aft swinging of the steering arm attached to 
the steering gear. 

Q. How is this fore-and-aft movement of the steering arm 

203 - ed ^y 



A. By the partial rotation of the gear within the steering gear 

Q. And how is this partial rotation of the gear developed? 

A. By the turning of the hand wheel, which turns the worm. 
The hand wheel is fastened to the upper end of the steering post 
proper (as distinguished by its stationary brass cover), while the 
worm is fixed to the lower end of it. Consequently, whenever 
the hand wheel is turned, the worm must turn also. 

Q. Why are the worm and the gear used for steering gears? 

A. The worm is used to secure irreversibility, as it is one of the 
few forms of mechanism which will not transmit power back through 
the entire group in .the reverse direction, that is, it will not allow a 
movement of the wheels to be transmitted back to the steering wheel 
against the driver's wishes. In addition, it is compact, noiseless, easy 
to care for, wears little, and is highly efficient. 

Q. What other forms of mechanism are used for steering gears? 

A. Bevel gear, screw-and-nut, double screw, worm gear and 
full gear as distinguished from worm gear and partial gear, spur 
gear, simple bent lever, and other forms. 

Q. What are the disadvantages of these forms? 

A. With the exception of the worm and full gear, all are wholly 
or partially reversible, so if the front wheels strike an obstacle, the 
shock is transmitted back to the driver's hands. 

Q. How are steering wheels made? 

A. In various ways. Some are rings of glued-up wood, to the 
underside of which the arms of the steering-wheel spider are fastened. 
Others have the arms cast integral with the aluminum rim; still others 
are of bronze with a molded rubber surface applied to the bronze ring. 

Q. Is the wood form, with spider fastened to it, popular? 

A. Yes. This form of steering wheel is more popular at present 
than at any other time in the history of the industry. It is used 
on some of the highest grade cars. 

Q. What are the advantages of the hinged, or folding, steering 

A. Folding up the wheel out of the way allows the driver to get 
out on the lever side of the car, which might be practically impossible 
otherwise. It allows stout drivers more comfort in getting in and out. It 
is also an advantage when working in the front compartment of the car. 


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Q. What is the importance of the cross-rod at the front axle? 

A. It is the only member tying the two steering knuckles 
together. If this rod is bent, the wheels cannot be steered accurately; 
if it is broken, they cannot be steered at all. In fact, the car cannot 
be moved forward when the rod is broken. 

Q. Why is the rod usually placed behind the front axle? 

A. As a protection against damage from high spots in the road. 
If it is back of the axle, it is well protected; but if the design places 
the rod in front of the axle, it has no protection, and trouble is likely 
to ensue on rough roads. 

Q. Where is the front end of the steering rod carried? 

A. As a similar means of protection, the ^steering rod is fre- 
quently carried over or above the front axle, so that the axle will 
protect it. Even when the design of axle, steering knuckle, and other 
parts necessitates this rod being below, it is placed as close as possible 
to the axle level, so as to get the maximum protection. 

Q. What is the function of the steering knuckle? 

A. It forms a pivot, or bearing, upon which the front wheel 
rotates; but, in addition, it forms the basis of steering, being capable 
of turning about a vertical (or nearly vertical) axis. 
Questions for Home Study 

1. Describe the complete steering mechanism of the Pierce- 
Arrow car. 

2. Why is it better to steer with the front wheels than with the 
rear wheels? 

3. Tell in detail how a worm and sector mechanism works. 

4. Describe the working of a worm and nut device. Is it better 
than a worm and gear and if so, why? 

5. How is the Gemmer steering gear adjusted (a) for wear of 
the worms; (b) for looseness of the steering wheel? How is it 

6. Describe the Hindley worm. What are its advantages; 

7. Select and describe one form of steering-wheel construction. 

8. How would you adjust a steering rod for (a) length; (b) 

9. Tell the advantages and disadvantages of the various possible 
positions for the cross-rod; for the steering rod. 



Q. What are the usual front-axle classes? 

A. Eliminating freak forms, axles are generally divided into 
five classes: Elliott; inverted or reversed Elliott; Lemoine; front 
drive; and fixed axle, or fifth wheel, form. 

Q. What is the nature of the Elliott front axle? 

A. The Elliott form has the end of the axle in the form of a jaw, 
or Y, with a bearing above and one below the steering knuckle. The 
latter fits in between the two parts of the jaw, or Y, and consequently 
has a single central bearing. 

Q. How does the inverted Elliott differ? 

A. In the inverted, or reversed, Elliott form, the axle end is made 
with a single central bearing, while the knuckle takes the form of a jaw, 
or Y, and has the two bearings, one above and one below the axle end. 

Q. Which of these two forms is the better? 

A. There is little choice, but what there is seems to favor the 
Elliott form because it gives a stiffer and better bearing in the axle end, 
which is generally a good size rigid member. In fact, the axle ends 
can be made large enough in this form to have ball, roller, or other 
anti-friction bearings. This is not true with the reversed form. 

Q. How is the Lemoine axle constructed? 

A. The steering knuckle and its pivot are integral and form a 
letter L. The axle end is plain and forms a single bearing on the upper 
end of the steering pivot. In the regular Lemoine form, the L has 
its vertical leg*extending upwards, and the axle is on top of the knuckle, 
so to speak. As constructed in United States the vertical leg of the L 
is turned downward, so that the axle is below the knuckle 

Q. What are the advantages of this form of construction? 

A. Both axle end and knuckle are simplified and can be con- 
structed more cheaply. Moreover, the complete axle can be assembled 
or disassembled more readily and quickly. Some consider that this type 
has a nicer, cleaner appearance and thus improves the front of the car. 

Q. What is the disadvantage of the Lemoine type? 

A. The principal disadvantage of the Lemoine axle, ascom pared 
with other forms, is the difficulty of suitably handling the bearing 
loads. The ordinary axle has separate radial-load bearings and 
thrust washers or thrust bearings. In the Lemoine the axle-end bear- 
ing must handle both radial and thrust loads, as well as road shocks, 


Digitized by 



Q. What are the usual axle materials? 

A. Modern practice restricts front axles to hand- and drop- 
forged steel, to tubular centers with forged ends, and to pressed steel. 
The latter is little used, however. Cast steel and manganese bronze 
as well as wood, have been used. 

Q. What are the usual axle bearings? 

A. Ball, roller, and plain bearings are widely used. For the 
sake of simplicity and compactness, the steering-pivot bearings are 
often plain, while the wheel bearings on the knuckle end are about 
evenly divided between ball and roller. Thrust bearings are about 
evenly divided between plain steel bearings with bronze washers, on 
the one hand, and with ball bearings, on the other. 
Questions for Home Study 

1. Describe a good method of truing front wheels. 

2. How would you determine that front wheels were out of 

3. Describe in detail the (a) Overland front-axle; (b) the 
Christie; (c) the Marmon. , 

4. How are axles lubricated, with reference to (a) wheel bear- 
ings; (b) steering pivots; (c) thrust washers or thrust bearings? 

5. What are the disadvantages of cast front axles? 

6. Are ball bearings better than roller bearings for front-axle 
pivots and if so, why? 

7. Describe in detail the process of straightening a bent front 
axle. Would you use a template and if so, why? 


Q. What is the need for a frame in an automobile? 

A. Every automobile needs a frame, stiff and strong enough to 
support all the units for power development and use, down to the 

Q. Is there any radical difference between pleasure=car and 
motor-truck frames? 

A. None, except that the truck frame must carry a much heav- 
ier load and, therefore, needs to be stiff er and. stronger and that it 
must cost less relatively, thus necessitating a form or shape which is 
cheaper to construct. 

Q. What materials are used for frames? 




A. Principally steel and wood. Steel is divided into rolled, 
used mainly for trucks; and pressed, used for pleasure cars and for 
the smaller trucks, or delivery wagons. Wood is divided into plain 
straight wood, laminated wood, and wood used as a filler for steel. 

Q. Is wood used at all widely? 

A. The Franklin is the only American car using wood as mate- 
rial for the frame. In this construction pieces of wood of reversed 
grain are glued together, thus forming a strong elastic frame. 

Q. Is steel tubing used for frames? 

A. Frames are no longer constructed entirely of tubing, although 
this has been tried, but some designers use tubular cross-members 
for the support of the engine, the transmission, and other units. 

Q. Is structural steel widely used? 

A. Structural steel was used quite freely a few years ago, but 
today pressed-steel frames are almost universally used, owing to 
the strength and low cost;, this has almost eliminated the use of 
structural steel in frames. 

Q. What is a frame "kick-up"? 

A. When the rear end of a frame otherwise fairly straight and 
level is bent sharply upwards from two or three to as much as ten 
inches, beginning just forward of the rear axle and carried out to the 
rear end of the frame on this higher level, this whole raised rear end is 
called a kick-up. 

Q. What is the purpose of a kick-up? 

A. It lowers the central part of the chassis relatively, thus giving 
a lower s»tep, incidentally lowering the center of gravity and making 
the car safer. It raises the rear end to give adequate rear springing. 

Q. What is the shape of the modern frame, in plan? 

A. It is gradually assuming a considerable taper. Originally, 
the frame formed a rectangle, with straight side members. Then it 
was found advantageous to narrow the front end to give more room 
for the front wheels to turn and thus allow a shorter turning radius. 
As this had the additional effect of shortening the engine-supporting 
arms, the makers were able to eliminate the sub-frame, with a saving 
of expense and weight. Finally, the width needed for modern 
touring car rear seats gradually widened out the rear ends of the 
frame, while the narrowing at the front became so great as to put a 
weak spot in the frame where its greater load had to be carried. It 

208 Digitized by G00gle 


then became a logical step to make the frame taper from front to rear 
continuously, with straight sides. This is the form which all frames 
are assuming now. 

Q. In what other ways do modern frames differ? 

A. The rear cross-member is being eliminated very widely, as 
is also the front cross-member, so the triangular-shaped frame is not 
closed at either end. Formerly, the depth of the frame was pretty 
much the same from front to rear, but now this tapers very materially 
from the front up to the middle and then down again at the rear. A 
good stiff typical frame would be perhaps 2\ inches to 3 inches deep 
at the front, 6 inches deep in the middle, and perhaps 2 J inches to 2f 
inches deep at the rear. In short, except for perhaps 20 to 24 inches of 
length right in the middle, the frame depth would differ continuously. 

Q. What is the advantage of varying the depth so much? 

A. It eliminates every pound of excess weight, putting much 
metal where there is heavy load and severe stresses and little metal 
where the load and the stresses are light. 

Q. Is this form of construction more expensive? 

A. No. The art of pressing the frame out of sheet steel has been 
developed through large quantity production to such an extent that a 
frame of this type, with a constantly varying depth, costs no more than 
a straight frame cost four years ago. 

Q. Does this form give the repair man more to do? 

A. No. On the contrary, frames give less trouble in the way of 
sagging, breaking, or cracking than ever before. The frame troubles 
of today are mainly due to poor or light design, in an effort to lower 
weight too far, or to accidents. 

Q. What has been the effect of cantilever springs on frames? 

A. One effect of cantilever springs for rear use has been to 
eliminate the rear cross-member, as spoken of previously. Another 
effect has been to continue the deepest, section back quite a few inches 
to the point of support of the front end of the cantilever. 

Q. Is the trussed, or latticed, frame widely used? 

A. Frames of this type were formerly made by one or two 
manufacturers, but they have now reverted to the pressed-steel 
frame. A few heavy cars have a truss rod below the main frame. 

Q. What are the noticeable tendencies in frame construction, 
other than those already mentioned? 


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A. The use of heavier frames, that is, heavier sections of metal, 
deeper side members, and general stiffening is being accomplished 
without much gain in weight, owing to the better distribution of the 
metal. The combination of other units, as steps, step supports, and 
fenders with the frame is being worked out, this being one of the tend- 
encies in construction. The general carrying of spare tires at the 
rear is having an influence, but there seems quite a tendency to con- 
struct the body so as to enclose the tires, which, if carried out, would 
change this. 
Questions for Home Study 

1. How would you repair a sagged frame, if sagged at (a) front 
end; (b) center; (c) rear end; (d) cross-member? 

2. Describe the method of welding a cracked frame by the 
oxy-acetylene process. 

3. Describe the following frames in detail: (a) Steams-Knight; 
(b) Marmon. (c) Fergus. 

4. How is the Franklin wood frame built up? 

5. How is what is called an "armored frame" made? 

6. Tell how to remove and replace an underpan. 

7. What material is usually used (a) for a truck frame; (b) for a 
light pleasure car; (c) for a heavy touring car? 

8. Give the advantages and disadvantages of pressed steel for 


Q. What is the need for vehicle springs? 

A. To support the load in a flexible maimer so that the jolts and 
jars of the road will not be transmitted to the passengers or load. In 
addition, a flexible connection between the power plant and the road 
wheels is needed. 

Q. How many recognized different types of spring are in use? 

A. Seven; all of which are made and used in all sizes and qual- 
ities for all kinds of load. 

Q. What are these seven types? 

A. The semi-elliptic, the full elliptic, the three-quarter elliptic, 
the platform, the cantilever, the quarter elliptic (or half semi-elliptic, 
as it is sometimes called). All but the last two also are made with 
scroll ends, which alters the general appearance without altering 
the type of action. 


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Q. What is the shape of the semi-elliptic? 

A. This form has a slight bow upwards, the two ends being 
slightly higher than the middle. The middle is attached to the axle 
and the ends to the frame, and when load is applied, these ends come 
down, flattening the spring so that it approaches a straight line. 

Q. Describe the full-elliptic spring. 

A. This form has the shape of two semi-elliptics, one inverted 
and set on top of the other. This gives it the appearance of an elon- 
gated letter O with points at the ends. The lower half is attached to 
the axle and the upper half to the frame, and loading tends to bring 
the two halves closer together, flattening the O still farther. 

Q. What is the form of the three-quarter elliptic spring? 

A. This consists of a flat lower semi-elliptic member and a 
highly curved quarter-elliptic upper member, the two being joined 
by means of a shackle. With the exception of the difference in 
curvature of the two parts and the use of the shackle to join them, 
this has the appearance of a full elliptic with the upper forward 
quarter cut away. When loaded, both members give slightly, the 
upper quarter more than the lower half. The shackle gives a consid- 
erable difference in this action from that of the full-elliptic. 

Q. What is the platform spring like? 

A. This spring consists of three semi-elliptics joined together at 
the ends so as to form three sides of a rectangle. The two sides are 
fastened, respectively, to the axle at the middle of each, to the frame 
at their front ends, and to the third spring at the rear ends. The rear 
spring is inverted and its center is fastened to the center of the rear 
end of the frame, while its ends are shackled to the rear ends of the two 
side springs. This makes a combination in which the normal semi- 
elliptic spring action is modified somewhat by the inversion of the rear 
cross-member and by the use of shackles at the ends of all three. 
While popular three or four years ago, it is now going out in favor of 
the three-quarter elliptic. 

Q. What is the cantilever spring like? 

A. It consists of an inverted semi-elliptic fixed or shackled to the 
outside of the frame at the front end, hinged or pivoted slightly 
forward of its center to the outside of the frame, and having its rear 
end attached to the upper or lower surface of the rear axle. It is used 
in greater lengths than any other form of spring and is very popular. 


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It is the most simple spring now in use and is said to give the easier 
riding of all. 

Q. What is the quarter-elliptic spring like? 

A. This is simply what its name indicates, one-half of a semi- 
elliptic or one-quarter of a full-elliptic. Its front end is fixed to the 
frame outside, and the rear end is shackled or allowed to slide on the 
rear axle. It is generally inverted. In reality, it is a cheap substi- 
tute for the cantilever or inverted semi-elliptic, this use being allow- 
able because of the light weight of both car and load. 

Q. Is this used in any different way? 

A. Sometimes a pair of these is used, one above the other, with 
the idea of doubling the resistance or rather of giving equal resilience 
with but half the movement. 

Q. What is meant by underslinging? 

A. When this refers to frame, the entire frame is placed below 
the springs. This has gone out of use. When referring to springs, 
this means placing the spring below its support, as below the rear axle. 
This construction lowers the frame and center of gravity by the 
thickness of the spring plus its seat plus the diameter of the rear axle, 
sometimes amounting to a total of five inches. It is growing rapidly 
in popularity. 

Q. What is the purpose of a shock absorber? 

A. To absorb the small vibrations while the spring cares for the 
large ones. It generally takes the form of any auxiliary spring or 
friction device. 

Q. What are the general classes of shock absorber? 

A. Coil spring, flat-plate spring, friction plates, compressed air, 
and a few hydraulic (or liquid) forms. 
Questions for Home Study 

1. How are springs lubricated (a) as to leaves; (b) as to shackles? 

2. How are the spring leaves separated for lubrication? 

3. Describe a method of getting home with a broken rear spring. 

4. Why do racing cars have their springs wound with rope or 

5. Describe the following car springs in detail: King; Winton; 

6. How do electric car springs differ from those of gasoline cars? 

7. What are the standard spring-plate widths? 


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Units in the Final Drive. Generally speaking, the transmission 
is located in the middle or forward end of the chassis. When this is 
the case, the final drive begins right at the rear end of the transmission. 
The units back of the transmission, then, would be a universal joint; 
a driving shaft; possibly another universal joint; the final gear 
reduction; rear-axle shafts and enclosure; the differential; the torque 
rod, or tube, or substitute for it; the wheels; the brakes; the tires; 
and other smaller units. 

Even when the transmission is placed on the rear axle, this 
general layout is changed little, and the transmission, which has been 
covered in detail previously, is not considered again. In the case of a 
chain drive, which is still used on one pleasure car or perhaps two, on 
a number of small trucks, and on a large number of large trucks, this 
layout is changed considerably. In the large trucks, the transmission 
in perhaps 90 per cent of all cases would be in a unit with the jack- 
shaft, which means that for consideration in the final-drive group 
there would be only the driving shaft to the transmission; the joint 
or joints in it, if any; the chains and the method of adjusting them; 
the rear axle and wheels; the brakes; the differential, of necessity 
becoming a part of the transmission; and the jackshafts. 

To make this clear and point out the various units, it will be 
noted in Fig. 430 that it is a unit power plant. Directly back of the 
transmission is the first universal joint, driving through the hollow 
propeller shaft to the rear axle, in front of which is the second universal 
joint. The rear-axle group includes the axle shafts, differential gears, 
final gear reduction, gear housing, and the wheels. The torque 
reaction of the drive, to be explained later, is taken by the torque rod, 
marked in the drawing, which connects the rear axle to the under 


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side of the stout 
frame cross-member 
in front of the axle. 

Universal Joints. 
The purpose of taking 
up the universal joints 
— it can be seen from 
the drawing — is to 
show how the rear 
axle rises and falls or 
moves sidewise in 
either direction with- 
out making any dif- 
ference in the trans- 
mission of power to 
the axle. When joints 
are used at other 
points, the purpose is 
generally to take care 
of any lack of align- 
ment, but here the 
purpose is to transmit 
power at an angle. 

The transmission 
of power at an angle is 
effected by construct- 
ing the joint so that it 
can work at any angle. 
Usually, this is done 
by constructing the 
central member in the 
shape of a cross, with 
four projecting arms 
or pins, all in the same 
plane. The ends of the 
two shafts are made in 
the form of forks, or 
Y's, and are set at 


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right angles to each other, that is, the forks are laid in planes which 
are at right angles. The fork on one shaft is fastened to a pair of 
diametrically opposite pins, while the fork on the other shaft is fas- 
tened to the other pair of diametrically opposite pins. Each shaft is 
able to turn on its pins about a line through the center of both. As 
these two lines are in planes which are at right angles to one another, 
but intersect at a common center, movement is possible in either 
plane, or by combination movements of both, in any direction. 

Thermoid=Hardy Universal Joint. This universal joint, Fig. 430a 
is a coupling having the ends of the shafts permanently bolted to 
discs of flexible fabric in such manner that there are no metal-to- 

Fig. 430a. Thermoid-Hardy Universal Joint 

metal bearing surfaces. Metallic 
friction is thus eliminated, there 
being left only a small amount of 
friction caused by the distortion 
of the fabric discs. This [type of 
universal joint has become very 
popular in the last two years as it 
greatly simplifies the construction 
of the early type of universal joint 
and its manufacture is less costly. 
In Fig. 430b is shown the 
method of cutting a disc. The in- 
dividual layers of fabric are first placed in staggered form and then 
vulcanized together; this piece of fabric is then machine cut to disc 




form. The purpose in staggering these layers is to prevent them 
from being drawn out of shape; it also increases the tensile strength. 
Tests have shown that these discs are capable of withstanding 
without damage to the fabric a driving torque that will twist a 
2-inch 10-gage tubular propeller shaft. This form of joint is appli- 


Fig. 430c. Method of Drilling the Holes in the Disc 

cable to trucks as well as pleasure cars and is used extensively in 
their construction. 

In Fig. 430c is shown the method of drilling the holes and the 
line of strain on the disc. 

Slip Joints* In many situations, a real universal joint is not 
needed, since the parts are not actually free to move in all directions; 
but what is needed is slight freedom up and down or sidewise 
combined with possible fore-and-aft movement. In such cases a slip 
is used, the name giving the idea of a joint which allows one shaft to 
slip, or slide, inside the other. The general construction of slip joints 
varies. Sometimes a round gear is fastened to the end of one shaft ; 
this gear has a fairly large diameter and many teeth, with the teeth 
chamfered to an unusual extent — almost rounded, in fact. An internal 
gear of the same size and number of teeth with similarly rounded 
profiles is meshed with the hollow gear of the other shaft. Both 
gears have unusually wide faces. This combination gives an action 
almost universal, and also allows lateral sliding of perhaps \ inch. 

The second form of slip joint consists of a squared shaft and 
square enclosure. 


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Occasionally a square joint is constructed as simple and small as 
possible, in which case the housing is not split and the shaft end is not 
rounded. This gives a simple square which drives through a simple 
squared-out hole. In this case there is no universal action, but simply 
lateral ot sliding freedom. 

Other Flexible Joints. To get away from the complication of the 
universal joint and yet give practically the same results, many other 
forms have been produced. A very thin disc of tempered steel, with 
the two shafts bolted to the two opposite sides of it, has been used. 
The metal will bend and give enough to allow considerable angle of 

drive. Later forms of the same 
joint use leather in several 
thicknesses, the leather being 
bolted up to the two shafts in 
the same way. A joint of this 
kind, consisting of several lay- 
ers of fabric which have been 
fastened together in lamina- 
tions until a disc of fair thick- 
ness, say | to f inch, has been 
built up, is shown in Fig. 431. 
Then the leather is cut round 
and drilled for the bolts. In 
this form, six bolts is the pre- 
ferred number, three for each 
shaft end; they are in a three- 
armed spider fastened to the 
end of each shaft, as the figure shows. These newer forms are usually 
convenient for the repair man, for they allow breaking into the main 
shaft by the simple removal of the three bolts (or two as the case may 
be). By taking out the bolts at each end of such a shaft, the shaft 
itself can be removed, leaving the other units in the chassis ready for 
immediate removal, according to the needs of the repair job. 

Types. Possible types of final drive, from the gear box to the 
rear axle and the driving wheels or from the motor to the gear box — 
in case this is mounted on the rear axle, as is not uncommon practice — 
are practically limited, in cars of sound design, to shaft and double- 
chain constructions. 

Fig. 431. Laminated Discs Forming Flexible 
Shaft Coupling 
Courtesy of Thermoid Rubber Company, 
Trenton, New Jersey 


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Shaft Drive. In its usual form, shaft driving in an automobile 
involves simply a propeller shaft interposed between the rear axle 
and a revolving shaft in the car above the spring action. There is 
some provision for takihg the torque of the shaft and of the axle so 
that they shall maintain their proper relative positions. 

In Fig. 432, a typical short driving shaft with its two universal 
joints is shown. This is such a shaft as would be used in the car 
shown in Fig. 430, except that the latter is a long wheel-base car with 
its transmission in a unit with the motor and clutch and thus, far 
forward. This combination necessitates a very long propeller shaft. 
The one shown is actually from a car having a short wheel base, with 
the transmission located amidships. This is a combination which 
calls for a fairly short propeller shaft. 

The short shaft; shown in the figure, is a solid shaft. The modern 
tendency toward lighter weights is being worked out in the case of 

Fig. 432. Ordinary Driving Shaft of Solid Form with Two Universal Joints 

propeller shafts, and many are now made hollow. By making the 
diameter slightly larger and having a large central hole, unusually 
light weight is obtained with all the strength of the solid form. In 
addition, the larger diameter hollow shaft has more rigidity than the 
small diameter solid form, and in many of the modern cars without 
torque or radius rods, unusual rigidity of the driving shaft is necessary. 
Other forms have been used for the driving shaft, but they come more 
or less in the freak class. About two years ago, a car was brought out 
with a spring, or flexible, shaft, which consisted of a rectangular 
member of considerable height, but fairly thin. The idea was not only 
to transmit the power of the engine, but to do it in a flexible manner, 
that is, the shaft was supposed to absorb all the sudden changes, 
such as quick acceleration or quick braking. At the same time, one of 
the electric-car makers brought out a chassis with a square driving 
shaft of very small size. This served the same purpose as the flexible 


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shaft only in a different way; its two ends, setting in square holes, 
formed two sliding joints without further machining. 

Fig. 434. Worm and Gear for Rear Axle, Showing Upper Position of Worm 
• Courtesy of Timken-Detroit Axle Company, Detroit, Michigan 

An objection to the shaft type of drive is that the reaction of the 
revolving shaft tends to tilt the whole car on its springs in a diree- 


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tion opposite to that in which the shaft is turning. In some cars, 
this is counteracted by the use cf slightly heavier springs on one 
side. The advantages of the shaft drive are the complete enclosure 
of all working elements, with their consequent protection from dirt 
and the assurance of their proper lubrication. 

The final drive of the Ford automobile, in which the end of the 
propeller shaft is shown at A, together with the bearings in which it 
revolves, the pinion by which it drives the car, the axle, the differen- 
tial, and the bearings of 
the floating inner ele- 
ments of the axle is illus- 
trated in Fig. 433. 

The shaft drive does 
not necessarily include 
the use of bevel gears for 
the final reduction at the 
rear axle; in fact, almost 
any form of gears may 
be used. In one well- 
known shaft-driven com- 
mercial car, the final 
gears consist of a pair 
of plain spur gears, while 
on the shaft of the second 
of these gears is a pair of 

As soon as the bevel 
gear final reduction dis- 
closed its limitations and 
disadvantages, designers started to displace it. One of the earliest 
forms of gear used for this purpose was the worm, an example of which 
can be seen in Fig. 434. This figure shows the worm placed above the 
wheel, but the lower position, which is also used, has the advantage of 
copious lubrication. In the form shown, the wheel must come directly 
beneath the worm so that the differential may be set inside of it. 

The worm is usually more suitable for slower moving vehicles 
which have a large reduction of speed between engine and rear wheels, 
that is to say, it is peculiarly fitted to electrics and motor trucks of all 

Fig. 435. Spiral Bevel Gears — a New Noiseless Type 

for Rear Axles 

Courtesy of Timken-Detroit Axle Company, 

Detroit, Michigan 


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sizes, on which it is finding wider and wider use.; On pleasure cars 
of the average size and type where a speed as high as 50 m.p.h. or 
higher is expected by all concerned, it has not been found suitable and 
consequently is not being used. 

A later form, which is designed to replace the straight bevel, is 
the spiral bevel. This is primarily a bevel gear with spiral teeth, the 

Fig. 436. Typical Roller Chain 

idea being to incorporate in the bevel 'gear the advantages of the 
spirally shaped worm tooth, without its disadvantages. As Fig. 435 
shows, this makes a very compact and neat arrangement, the differ- 
ential fitting within the larger gear in the same manner as with the 

Double-Chain " Drive. ^ The use of double chains, by which the 
driving wheels of an automobile are driven from a countershaft 
across the frame of the machine, is a practice possessing a number 
of advantages/ But because of the noise and quick wear with badly 

Fig. 437. Typical Silent Chain 

designed chain drives and the difficulties of completely enclosing the 
driving mechanism, chains are not now as popular as formerly. 
Nevertheless, the elimination of universal joints working through 
large angles and under heavy loads, the avoidance of heavy weights 
carried on rear axles without spring support, the lowering of the 
clearance by the differential housings, etc., are very real objections 
that the double chain avoids. 

For trucking and other heavy service, chains are still commonly 
in use, and it is the belief of many that a better understanding of their 


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merits and the means of securing these merits in positive and per- 
manent form will result in their more general use. 

'A typical roller chain of the type most used for automobile 
drives is illustrated in Fig. 436. 

• Silent chains, of the types illustrated in Figs. 437 and 438, possess 
certain points of superiority over roller chains and are therefore com- 
ing increasingly into use for camshaft drives, in gear boxes, etc., and 
there is some possibility that they will find more extensive application 
to final drives than at present. 

The action of a silent chain is illustrated in Fig. 438, in which it 
is seen that as the chain links enter the sprocket teeth the chain 
teeth at the same time close together and settle in the sprocket with 

vm pos/r/ort 

2N& P05/T/0M 

isr, pos/r/o// 

Fig. 438. Action of Silent Chain and Sprockets 

a wedging action that causes them to be absolutely tight, but without 
any more binding than there is backlash. 

To keep silent chains from coming off sidewise from the sprockets 
over which they run, it is customary to make the side links of deeper 
section than the center links, as is illustrated in Fig. 437. Another 
successful scheme is grooving the sprocket to receive a row of special 
center links in the chain, which are made deeper than the standard 

At present, only one American pleasure car, the Metz, has 
final drive by means of silent chains. This is a small car with a 
friction transmission, the drive from the ends of the cross-shaft being 
by enclosed silent chain to each rear wheel. 

Torque Bar and Its Function. It is a well-known fact that action 
and reaction are equal and opposite in direction, so that if a gear is 
turned forcibly in one direction, say clockwise, there is a reaction in 
the opposite direction, or counter-clockwise. This is the simple basic 
reason for a torque bar, or torque rod, on an automobile. It is needed 
with any form of final drive, but it takes different forms, according to 

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the type of gear used. The bevel and spiral bevel used on nearly all 
of the 1920 cars are explained in detail as follows: Fig. 439 shows the 
rear end of a typical pleasure-car chassis. The engine is rotating 
clockwise, and so is the driving shaft A, as shown by the arrow. The' 
shaft turns the pinion B in a clockwise direction, which rotates 
the large bevel C so that its top turns toward the front of the car. 
The bevel C turns the rear axle D and the rear wheels (not shown) 
in the same direction; so the car moves forward. 

In addition to the gear C and shaft D turning easily in the axle 
housing E, there is an equal and opposite reaction which tends to keep 
them stationary, while the bevel pinion B and driving shaft A tend 
to rotate around the rear axle as a center in a counter-clockwise direc- 

Fig. 439. Diagram to Show What Torque Is and Why Torque Rods are Necessary 

tion, as shown by the diagram. If the rear axle were held firmly 
so it could not rotate, and there was nothing to restrain the bevel 
pinion and shaft, this could easily happen. However, since we do 
not wish this to happen, a means is provided to oppose this action 
and prevent it from happening. Since the turning force which makes 
the shaft rotate is called the torque, this rod, bar, or tube, whatever 
its form, is called the torque member. 

In the sketch, the torque member is marked F and is attached to 
. the frame cross-member G, between a pair of springs, so as to cushion 
the shocks of sudden car or shaft movements. The force on this is 
the force which tends to rotate the driving shaft and pinion counter- 
clockwise, so that it works upward, as shown by the arrow. The 
frame prevents this and absorbs the force. 


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Fig. 440. Diagram to Explain Driving Reactions 
Using Radius Rods 

Driving Reaction. As has been stated, the power, or torque, of 
the motor is used to rotate the rear wheels. These stick to the pave- 
ment or road surface, so 
the car is really pushed 
forward. Since it is this 
pushing action which 
really moves the car for- 
ward, it is very interest- 
ing to note how this push 
is transmitted from the 
wheels and rear axle to 
which they are attached 
to the frame which car- 
ries the body and pas- 
senger load. 

The transmission of 
the drive to the body is 
accomplished in one of 
three ways. /The first form was the so-called radius, or distance, 
rod, which the shaft-driven car inherited from the chain-driven form. 
In the chain drive, these 
rods were a necessity and 
served a double purpose; 
they kept the driving and 
driven sprockets the 
proper "distance" apart 
for correct chain driving 
(hence their name "dis- 
tance" rods), and they 
also transmitted the drive 
back to the frame. On 
the sKaft-driven car, the 
distance function is not 
needed, so they are called 
radius rods. As shown 
in Fig. 440, they transmit 
the drive forward to the frame, thus propelling the car in the direc- 
tion of the arrow, and they also keep the rear axle in its correct position. 

Fig. 441. Layout of Driving Reaction Using Torque 
Tube around Shaft 


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In lightening and simplifying the shaft-driven car, designers 
figured that three members for the torque and driving reactions were 
too many; so a design was worked out in which all three were combined 
into one, which is a form of tube surrounding the shaft. This made 
the member light but strong, and simplified the whole rear end. As 
shown in Fig. 441, the tube has forked ends at the front, which are 
connected to the frame cross-member in such a way as to absorb the 
torque reaction and also to transmit the drive. The method has 
the further advantage of needing but one universal joint, and that 
at the front end. Furthermore, it gives a correct radius of rise and 
fall for the rear axle, since the center of the combined torque and drive 

member is also the centerof 
the universal joint in the 
driving shaft. In the form 
shown in Fig. 339 (radius 
rods not shown), the two 
different centers will be 
noted, the torque rod giv- 
ing a greater radius than 
the shaft. Similarly, in 
Fig. 440 (where the torque 
rod is omitted for clear- 
ness), the rods give a 
longer radius of rear-axle 
movement than the shaft, 
which has a joint close to 
the axle. 

It will be noted that both these methods allow complete freedom 
of the rear springs, which may be of any form, and shackled at the 
front end if desired by the designer. In its newest and simplest form, 
the so-called Hotchkiss, or spring, drive has both the radius and 
torque rods omitted, the springs being forced to transmit both forces, 
as shown in Fig 442. In this case, the forward end of the rear spring 
must act as a rod, or lever, instead of as a spring, and must be fairly 
straight and stiff without a shackle, but firmly pivoted on the frame. 
In addition, the shaft must have two universal joints, as shown. 
It must be stated, as a simple fact, that this last form is increas- 
ing rapidly and at the expense of the other two. On smaller lighter 

Fig. 442. 

Arrangement of Driving Reaction When 
Hotchkiss Drive is Used 


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cars it is gradually replacing all other forms. It has the advantages 
of minimum weight and fewer parts, and applies the driving force in a 
direct line to the frame, the same as the two radius rods do. On the 
other hand, it makes the springs serve a triple purpose, the demands 
on these for torque and drive transmission and absorption being such 
that the spring flexibility must be negligible, which makes the car ride 
hard. In addition, making the springs handle the three widely 
different actions puts'additional stresses upon them, so that they are 
more likely to break. On the medium size and larger heavier cars, 
this construction is not gaining so rapidly. 


Classification. Rear axles may be divided into the following 
classes, distinguished according to the method of carrying the load and 
taking the drive: the form in which the axle carries both load 
and drive; the semi-floating form, carrying the drive and a small part 
of the load, the axle shafts not being removable without removing 
the wheels; three-quarter floating form, carrying the drive and a small 
part of the load, the latter being divided between the shaft and its 
housing, but with the shafts removable; seven-eighths floating form, 
carrying the drive but not the load, the arrangement of bearings to 
take the load being such that the wheel hubs do not rest wholly and 
solely upon the axle-casing end; the full floating form, in which the 
shaft does nothing but drive, and is removable at will without dis- 
turbing the wheel and wheel weight resting on the axle-casing end, 
which is prolonged for this purpose. 

The seven-eighths floating type has been developed to meet the 
need which arose for a floating construction, in which the axle casing 
did not pass entirely through the wheel hubs. With the full floating 
form, any accident to the wheel, in which it was struck from the side, 
also damaged the casing, or tube, end. The result of this in nine 
cases out of ten was to make the removal of the wheel impossible, 
because the tube end, which projected through, was bent over. 
Moreover, repairing in such a situation called for a new axle casing 
— a very expensive proposition. Consequently, the seven-eighths 
floating form was developed to present all the advantages of the 
full floating form, with this serious drawback eliminated by a rear- 
rangement t)f the parts which did not necessitate prolonging the axle 


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through the wheel hubs. Despite the facts, it did not gain as rapidly 
as the other floating forms, and now is almost out of use. 

The three diagrams in Fig. 443 explain the types as well as words 
can. At the top is shown the full floating axle, the best but most expen- 
sive form. In thfc middle, the semi-floating axle, which makes the axle 
shaft do all the work — carrying load as well as transmitting power — is 

shown. At the bottom is the 
three-quarter floating form, 
which is really a combination 
of the other two forms and 
possesses a maximum of ad- 
vantages with a minimum 
cost. The car weight is car- 
ried on the tubing, while the 
shaft drives and carries a por- 
tion of the side stresses to 
which the wheels are sub- 
jected, the quantity depend- 
ing upon the construction of 
the bearings. 

Of the 1917 cars, prac- 
tically 30 per cent (29.5) have 
the three-quarter floating rear 
axle, 25.5 per cent the semi- 
floating form, and 43.5 per cent 
the full floating form. In 1916, 
however, the three-quarter 
form was used in but 22.8 per 

Fig. 443. Arrangement of Axle Bearings and Hous- cent > an d in 1915 in Only 18.5 
ing in Three Principal Forms of Rear Axle per Cent of the Cars. These 

figures show how the three-quarter floating axle has been gaining 
constantly at the expense mostly of the floating form, the semi-floating 
form practically standing still for three years. 

Axle Carrying Load and Drive. The type in which the axle 
carried both load and drive was a peculiar one and did not last long. 
In this form, the rear-axle shafts were exposed and carried the 
weight of the load at the spring seats, which were bushed to allow 
the shafts to turn within them. This made a place which was hard 


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to lubricate, and yet which was down in the dust and dirt, so that 
lubrication was a great necessity. All these causes, coupled with the 
fact that the axle carried both load and drive, caused its disuse. 

Dropped Rear Axle of Full Floating Type. The dropped type 
of axle is not much used at present for cars of the shaft-driven type, 
the dropped part of the axle bed being used to hold the rearward- 
placed transmission. Fig. 444 shows a former American type, in 

Fig. 444. Rear Construction Embodying Dropped Type of Rear Axle 

which the weight of the car as well as the weight of the load is carried 
on the I-section drop-forged rear axle, while the drive is transmitted 
from the transmission by the usual shafts, which carry no load. The 
cut shows the complete assembly above and the dropped axle below. 
The round ends of the I-beam axle are hollow, carrying the driving 
shaft through the central hole and the wheels on bearings which 
fit over the outside. The wheels will revolve on the bearings, even 
if the inner shafts and transmission be removed from the chassis. 
Despite its manifold advantages, the expense of constructing 
an axle of this type — it is practically the same as that of two ordi- 


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nary axles, making the total cost double that of any other form— has 
worked to prevent its general use. In fact, it is not now in use in 
this country, as the maker has gone out of business. 

A prominent French constructor, De Dion, utilizes a dropped 
rear axle, but, in this, the differential casing and gearing are suspended 
from the frame and drive down to the axle shaft by means of a pair 
of short inclined shafts with two universal joints in each, that is, 
the drive from the differential to the two wheels contains four universal 
joints. The inevitable loss due to the necessarily short inclined shafts 
and to the two joints in each has deterred other manufacturers from 

Fig. 445. Typical Bail-Bearing Differential 

using this form, although a few makers — notably the Peerless Com- 
pany — have inserted a pair of joints in the rear axle in order to give the 
rear wheels the same camber as the front wheels. As this necessitates 
inclined shafts, the joints are needed to connect the horizontal center 
part with the inclined ends. 

Clutch Forms in Semi=, Three-Quarter, and Full Floating Types. 
The main point of difference in the various semi-, three-quarter, and 
full floating axles, aside from the principle of design which makes them 
decidedly different, is the clutch, by means of which the wheel is driven. 
In some cases, this clutch takes the form of a gear, with straight sides 

231 Digitized by 



and external notches, or jaws, to correspond with the teeth, but 
usually it is more of a claw type, the driving ends projecting inward 
from the point of attachment to the axle shaft. Another notable 
point of difference — and one which makes a huge difference in the cost 
— lies in the machining of these jaws, whether they are attached to the 
axle or machined up with it in one piece. The latter is considered 
better and stronger in every way, but, as it is much more expensive, 
it is used only on the best cars. 

The driving clutch takes various forms, one of which is shown 
in the Studebaker axle, Fig. 445. In this type, the axle is a square 
rod acting within a square hole in the hubs. In the small detail at 
the upper left-hand corner the letter A shows the square upon which 
the driving clutch is slipped. The spaces at the inner ends of this 
indicate the clutches, or jaws, which mesh with corresponding slots 
on the wheel hub and thus do the driving. 

Fig. 446. Rear Axle, Showing Wheels Driven by Spur Gears 

The dropped type of axles are neither all shaft-driven nor all 
chain driven. Fig. 446 shows one that is of the spur-gear driven 
type. The dropped axle bed C is of tubular form, and the differ- 
ential case is dropped down on and slightly back of the rear axle, as 
at B. From this case, two shafts A A extend out to the sides, driv- 
ing the wheels through the medium of the spur gear D, which meshes 
with internal gears within the wheel hubs (not shown) . This type of 
rear axle and drive is used on a number of the Fifth Avenue stages 
in New York City. 

Internal=Gear Drive for Trucks. The spur-gear driven type 
just described is gaining rapidly for motor-truck use, because it has a 
number of important advantages. Besides carrying the heavy load 
on a member able to withstand any amount of overload, it materially 
lightens the power-transmitting portion of the axle, which is enclosed 
and therefore quiet. It is simple and inexpensive to construct and 
repair. Fig. 447 shows a section through one of these axles, which is 


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used on a very light truck of f-ton capacity. In this figure, it will be 
noted that the load-carrying axle is behind the power-transmitting 

shafts, consequently the for- 
mer is straight. In Fig. 446, 
the load carrying axle is in 
front and consequently must 
be bent down at the center. 
This bend is a source of weak- 

Full Floating Axle. Fig. 
448 shows a full floating axle, 
with the ends of the driving 
shafts projecting beyond the 
housing and carrying five 
jaws which mesh with 
five similar ones in the wheel 
hubs and thus drive the 
wheels. Unless the jaw end is 
welded on to the shaft, this 
makes a very expensive axle 
despite its many good points. 
Fig. 449 shows the rear con- 
struction of a car with full 
floating axle, with the brace 
below it for the purpose of 
strengthening the whole con- 
struction. The large diam- 
eter brake drums, shown close 
to the wheels, are made of 
pressed steel and are united 
to the axle tubing, which is 
also united to the differential 
housing, so that the whole 
forms one large and continu- 
ous piece, except where the 
differential unit bolts on one 
side and the cover on the 
other. Note that the shaft 

Fig. 447. Sectional Drawing through Internal-Gear 

Drive Axle of Three-Quarter Ton Capacity 

Courtesy of Russell Motor Axle Company, 

Detroit, Michigan 


Z <* 


has the driving clutches machined as an integral part, and that 
removing the two shafts for a few inches makes it possible to unbolt 

Fig. 448. Example of Full Floating Type of Axle 

Fig. 449. Timken Full Floating Rear Axle, Showing Differential Removed 
• Courtesy of Timken-Detroit Axle Company, Detroit, Michigan 

Fig. 450. Timken Full Floating Rear Axle with Spiral Bevel Gears 

and remove the entire differential unit. For the sake of compari- 
son, Fig. 450 shows an axle which differs from Fig. 449 only in having 
spiral bevels substituted for the ordinary straight-tooth bevels. In 


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Fig. 450, the differential unit is removable in iLe same manner as 
in Fig. 449. One of the axle shafts, with its integral driving clutches, 
and the differential cover are shown below. Note the two plugs in 
the cover; the upper one is for filling the case with lubricant, while the 
lower plug acts as a level indicator. When it is opened, heavy oil 
or oil and grease combinations are put in the filling plug above until 
the lubricant begins to flow out of the lower opening. 

Three-Quarter Floating Axle. An interesting study in rear axle 
design is seen in Fig. 451. This axle has a number of points in which 

Fig. 451. Partial Section through Rear Axle of Case Car, Showing Construction 
Courtesy of J. I. Case T. M. Company, Racine, Wisconsin 

it differs from previously described forms. It is of the three-quarter 
floating type. Note the enclosure of the driving shaft and the splines 
at its forward end for the universal joint, also the housing for the joint 
forming the torque member. The small roller bearing for the spigot 
end of the driving shaft beyond the bevel pinion is unusual; so are 
the diagonal distance rods, the spherical seat for the springs, the 
combination of drawn-steel tubes, steel castings, and pressed-steel 
cover for the axle housing. The wire wheel and its method of attach- 
ment will be seen, also the double set of brakes, internal and external 




on the same drum, with operating shafts for both supported from the 
central part and ends of the axle housing. 

Rear-Axle Housings. Rear-axle housings are usually of pressed 
steel, although castings play a very important part and are some- 
times used alone and sometimes in combination with other castings or 
in combination with pressed steel. Aluminum, although not a depend- 
able metal, is used quite a good deal for the purpose of saving weight, 
as excess weight upon the rear axle is anything but desirable. In 
one unusual but effective combination, the axle housing consists 
of two malleable-iron castings joined together by means of bolts at 
the centers, the brake drums being cast as a part of the tubes. While 
not usual, this is safe practice, for malleable iron is tough and will 
not break or splinter. It seldom is the case, however, that the axle 
casing is reduced to as few parts as are shown here. 

Welding Resorted To. Where the differential housing or brake 
drums are of malleable iron, cast steel, or even of pressed steel, and it 
is desired to unite them with the steel tubing forming the main part 
of the shaft housing, welding is now universally used. Formerly, 
it was good practice to make the casing a drive fit on the tube, riveting 
it in place, or else soldering it in place, making doubly sure by using 
rivets. Now, however, welding is resorted to, either the oxy- 
acetylene, electric, or some other process being used. 

In the axles shown in Figs. 449 and 450, it will be noted that 
the axle shell is of pressed steel, to which the spring seats are bolted, 
the remainder of the construction being formed by drawing. In Fig. 
448, however, the construction is such as to necessitate making the 
two halves longitudinally and then bolting o* spot-welding them 
together. Being machined after they are fastened together, it makes 
as accurate a construction as the one-piece jobs, Figs. 449 and 450. 

Effect of Differentials on Rear Axles. A differential gear, 
sometimes called a balance, or compensating, gear, is a mechanism 
which allows one wheel to travel faster than the other and which 
at the same time gives a positive drive from the engine. This device 
is a necessity in order to allow the car to go around a curve properly, 
for in doing so the outer wheel must travel a greater distance than 
the inner one during the same interval of time. 

There are two forms of differential, the bevel type and the all-spur 
type, the latter differing from the former only in the use of spur gears 




instead of bevel gears. The principle used in both is that a set of 
gears are so held together that when a resistance comes upon one 
part of the train of gears the whole train will stop revolving around 
on a stationary axis and revolve around another gear as an axis, the 
first gear, in the meantime, standing stationary, or practically so, 
according to the amount of the resistance encountered. In the 
bevel type, a pair of bevels are set horizontally. Between the bevels 
is a spider with three or four arms, with a small bevel on the end of 
each. These small bevels mesh with the larger bevels at the sides 

and ordinarily stand still, ro- 
tating around on the arm of 
the spider as an axis by virtue 
of the continued rotation of 
the two side gears in opposite 
directions. When one wheel 
meets greater oostructionSon 
the road than the other, thus 
holding it back, the shaft 
which drives that wheel lags 
behind the shaft driving the 
other wheel and thus holds 
back the horizontal gear at- 
tached to the shaft. This 
retarding movement allows 
the other horizontal gear 
more freedom to rotate. The 
result is that the spider carry- 
ing the smaller bevels rotates 
around on its axis, thus imparting to the free gear attached to the free 
wheel an additional motion, and to the free wheel a doubled speed, 
while the retarded wheel has a lessened speed. This takes the car 
around the corner without breaking the rear axle, as would be the 
case without some such contrivance. The description of the bevel 
differential action applies equally well to the spur type, except that 
all gears are spurs. 

The dividing of the rear axle is, of course, done to make a place 
for the differential gear to work, and much time and thought have been 
given to this subject in an endeavor to work out a substitute which 

Fifc. 452. Peculiar Differential Construction 


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would permit the differential action and still allow the strengthening 
of the rear axle. Fig. 452 shows one solution of the problem, which 
has been worked out in such a way that the differential is moved 
forward into the driving shaft. The rear axle shafts are thus greatly 
strengthened, the designer being unhampered by the presence of the 
differential in the rear axle. In this design, one side gear of the bevel- 
gear differential is carried upon a shaft, and the other upon a tube 
around the shaft. Then, at the rear axle, two sets of bevel gears 
B 2 Bi and A \A 2 are used, Ai being driven by the main shaft, and driv- 
ing the right-hand shaft through the gear A 2 ; while the other B 2 is 
driven by the tube, and drives the left-hand shaft through the gear B$. 
In this case the axle shafts are made much larger than in the ordinary 
case, while the differential action is just the same. 

Improved Forms of Differential. Lately, much work has been 
done upon differentials to cause them to act as differentials should. 
The present form of differential acts according to the amount of 
resistance offered, but should act according to the distance traveled. 
When no resistance is offered, all the power is transmitted to that 
wheel, leaving the other stationary. This is just the opposite of the 
desired effect. If a differential were constructed to work for distance 
only, then, in the case of a wheel on ice or other slippery surface which 
offered little or no resistance, both wheels would still be driven 
equally, and the power transmitted to the one not on the ice would 
pull the vehicle over it. 

One way in which the differential action might be corrected is 
by the use of helical gears and pinions instead of the usual bevel or 
spur gears. In the M & S forms, this construction is used, Fig. 453, 
showing the form constructed by Brown-Lipe-Chapin. In this form, 
each axle shaft carries a helical gear, and the differential spider carries 
two helical pinions with radial axes and four additional pinions, each 
of which meshes with one of the radial pinions and one of the gears 
on the axle shafts. On a turn, the outer wheel tends to run ahead 
of the inner and thus causes the nest of helical gears to revolve. All 
gears and pinions have a right-hand 45-degree tooth, so that one wheel 
may revolve the housing if the other is locked or held, but it is impos- 
sible to turn the free road wheel by pulling on the housing. The 
principle is the same as a worm steering gear in which the turning of 
the hand wheel may be transmitted to the front wheels, but the gear 


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cannot be operated from the wheel end, because the worm is irrevers- 
ible. This differential is used to advantage to prevent spinning on 
slippery ground and also to eliminate the skidding which the ordinary 
differential gives. 

Another somewhat similar device has but two pairs of helical 
pinions in addition to the two helical gears on the shafts, the axes of 
each pair being set at an angle to the others. Thus, each helical 
gear and its pinion form an irreversible gear combination, so that 
movement cannot be transmitted through either in the reverse direc- 
tion. This form fulfills the same conditions as the Brown-Lipe- 
Chapin M & S form, as the construction is such that no motion can be 

Fig. 453. The M & S Helical Gear Differential in Sections 
Courtesy of Brovm-Lipe-Chapin Company, Syracuse, New York 

transmitted from the differential spider or housing to one of the wheels 

The above principle is back of the gearless form, shown in Fig. 
454, in which the result is achieved through ratchets instead of heli- 
cal gears, the lack of gears giving it its name. In this form there are 
two ratchets Y and Yl, which are keyed to the two axle shafts and 
free to rotate independent of the housing. The round members ' 
marked B are the interlocking pawls; the upper one is in a tooth of the 
right-hand ratchet at the right and is driven by the contact face of 
the driving sector X at the left. Thus, the right-hand ratchet is 
being driven positively forward. The lower pawl is engaged at 
the other end; so the left-hand ratchet is also being driven positively 


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forward. On a turn, one wheel revolves faster than the other, say 
the right, and causes the right-hand ratchet to move faster than the 
differential housing, which can only go as fast as the other, or slow- 
moving, wheel. Then, the right-hand ratchet pushes the end of 
its pawl out of the tooth and gives it a free movement forward. As 
soon as the wheels revolve at equal speeds, the spring pushes it back. 
In the figure, the right-hand portion shows the original form in 

Possible Elimination of Differential. The whole modern tend- 
ency is toward differential elimination. In the cyclecars and small 
cars brought out in recent years, designers have been forced to get 

Fig. 454. Sketches Showing Construction and Operation of Gearless Differential 

along without it because of the demand for simplicity, light weight, 
and low price. This effect has been obtained by the use of a pair of 
driving belts, letting one slip more than the other; by the use of fric- 
tion transmissions; by simply dividing the rear axle and letting one 
side lag when there was resistance; by not dividing it and letting 
one wheel drag; and in other ways. The evident success of these 
small vehicles without a differential or any real substitute for one 
has set designers to thinking about this subject again, and some 
big cars without a differential, or with a more simple and less 
expensive substitute for it, may appear in the near future. 

Rear-Wheel Bearings. The bearings used on rear axles differ 
very little from those used on front axles. All forms are used — plain 


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bearings, ball bearings, ball thrusts, roller bearings in both cylindrical 
and tapered types, and all combinations of these. Thus, Figs. 445 
and 452 show the exclusive and liberal use of ball bearings, while Fig. 
451 shows all rollers of two kinds and ball bearings for thrust bear- 
ings only. The two kinds of roller bearings are the tapered roller and 
the flexible roller. Similarly, in Fig. 447, it will be noted that balls 
are used with two kinds of rollers, straight solid rollers in the wheels 
and flexible rollers in the differential case. Figs. 449 and 450 show 
the exclusive use of the tapered roller type, a construction which is 
gaining ground very rapidly, the same as in front axles, although, 
formerly, ball bearings were most widely used. The materials 
employed are similar to those used for front axles, which have been 
previously described. Cases are made of all kinds of steel and iron — 
pressed, drawn, cast, etc. — not to speak of crucible steel, malleable 
iron, manganese bronze, phosphor bronze, aluminum, aluminum 
alloys, and many combinations of these materials in twos and threes. 
Rear-Axle Lubrication. Rear-axle lubrication is generally 
automatic in so far as the central bevel or other gears and the differ- 
ential housing are concerned. The housing usually has a form of 
filling plug, or standpipe, which is used to fill the case with a form 
of heavy grease every 5000 miles, or once each season. The case is 
generally arranged so the filling plug works through and lubricates the 
outer bearings on the axle shafts as well, with suitable provision 
against this reaching the brake drums or other brake parts. The 
wheel bearings either are cared for in this way or have a central 
space which is filled with heavy grease once a season, being self- 
lubricating from then on. Such other rear axle parts as need occa- 
sional lubrication, as torque-rod pivots, brake-band supports, brake- 
operating shafts, etc., are generally provided with external grease cups, 
which are given a turn once a week on the average. It is highly 
important that the braking system be as well lubricated as the lubri- 
cating means provided will allow. 


Jacking-Up Troubles. Much rear-axle work — practically all, 
in fact — calls for the use of the jack. True, the full floating type of 
axle can have its shaft removed without jacking, but, aside from 
differential removal, there is little rear-axle trouble in which it is 


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necessary to remove the shaft alone. In almost all cases, the axle 
must be jacked up. Many axles have a truss rod under the center, 
and this is in the way when jacking; however, this can be overcome. 
Make from heavy bar iron a U-shaped piece like that shown on 
top of the jack in Fig. 455, making the width of the slot just enough 
to admit the truss rod. The height, too, should be as little as will 
give contact with the under side of the axle housing. 

Svbstitvte for Jack. A good substitute for a jack is a form of 
hoist, Fig. 456, which will pick up the whole rear end of the car at 
once. This not only saves time and work, but holds the car level, 
while jacking one wheel does not. Moreover, with a rig of this kind, 
the car can be easily lifted so high that work underneath it may be 
easily done. The usual hoisting blocks are very expensive, but the 
above hoist can be easily made by the ingenious repair man. This 
one was made from an old whiffletree with a chain attached at each 
end. For the lower ends of the chains, a pair of hooks are made 
sufficiently large to hook under and around the biggest frame to be 
handled. With the center of the whiffletree fastened to the hook of 
a block and tackle, the hoist is complete. By slinging the hooks 
under the side members of the frame at the rear, it is an easy matter 
to quickly lift that end of the chassis any distance desired. 

Workstand Equipment. Next to raising the rear axle, the most 
important thing is to support it in its elevated position. To leave it 
on jacks is not satisfactory, for they will not raise the frame high 
enough, and, furthermore, they are shaky and may easily let the whole 
rear end fall over, doing considerable damage. With the overhead 
hoist, the chains or ropes are in the way; so a stand is both a necessity 
and a convenience. In Fig. 457, several types of stands are shown. A 
is essentially a workstand, intended to hold the axle and part of the pro- 
peller shaft while repair work is being done thereon. It consists of 
a floor unit, or base, built in the form of an A, with six uprights let 
into it, preferably mortised and tenoned for greater strength and 
stiffness. Then, the four rear uprights are joined together for addi- 
tional stiffness and rigidity. If casters are added on the ends, the 
stand can be more conveniently handled around the shop. 

The forms B are for more temporary work and consequently 
need not be so well or so elaborately made. The little stand C is a 
very handy type for all-around work. Stands of this kind with the 


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top surface grooved for the axle are excellent to place under cars 
which have been put in storage for the winter. 

The stand D is, like A, a workstand pure and simple. In this, 
however, the dropped-end members allow supporting the axle at 

Fig. 455. Simple Arrangement for Avoiding 
Rear- Axle Truss Rod 

Fig. 456. Simple Automobile Frame Hoist 

those points, while the elimination of central supports gives plenty 
of room for truss rods. This type of stand would preferably be made 
from metal, pressed steel or small angle irons being very good. Every 

Fig. 457. Types of Handy Stands for Rear-Axle Repair Work 

repair shop should have a considerable number and variety of stands, 

made as the work demands them, to fit this particular class of work.. 

Universal-Joint Housings. Universal joints usually are covered 

with leather casings which are packed with grease. These keep out 


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the dirt and, consequently, lessen the wear, and also lubricate the 
moving parts of the joints. A secondary function of the casings is to 
render these joints noiseless. If a car is not equipped with them, it is 
advisable for the owner to purchase them. 

The shape of these casings, when opened out flat, would be not 
unlike that of two bottles with their flat bottoms set together, that 
is, narrow at the top and bottom and wider at the middle. All along 
both edges are eyelets for the lacing. The enlarged center fits around 
the joint, while the small ends encircle the respective shafts. To apply 
the casing, one end is placed around the shaft on one side of the joint, 
and the lace started; then the lacing proceeds, gradually drawing 
the ends together and around the joint. When this has been com- 
pleted, and before the last end is closed, the whole is shoved back 
along the first shaft a little way, and the center portion half filled 
with a heavy grade of transmission grease. This done, the glove is 
pulled back into place, and the work of lacing completed around the 
second shaft. Both ends should be laced as tightly as possible, while 
the middle part should be loose. Sometimes these housings will 
become worn and make a very annoying chatter on the road, even 
when they are not sufficiently worn to warrant replacements. Under 
such circumstances, the offending member may be wound with tire 
tape held firmly in place in addition to its adhesive power by means of 
a hose clamp, as shown in Fig. 458. The coupling is held tightly 
enough to prevent the rattle and chatter, but not enough to interfere 
with its action. While not a handsome job, it does the business, 
stopping the noise effectively. 

Rear Axle. Rear axles do such hard work and must stand up 
under such a large portion of the load carried in the machine that 
they offer many chances for wear, adjustment, or replacement. 

Truss Rods. Truss rods hold the wheels in their correct ver- 
tical relation to the road surface and to one another. If, through wear 
or excessive loading, the axle sags so that the wheels tip in at the 
top, presenting a knock-kneed appearance, the truss rods must be 
tightened up. Usually, they are made with a turnbuckle set near one 
end, a lockhut on each side preventing movement. The turnbuckle 
is threaded internally with a right-hand thread on one end and a left- 
hand thread on the other, so that a movement of the turnbuckle draws 
the two ends in toward one another, shortens the length of the rod, 


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and thus pulls the lower parts of the wheels toward one another, 
correcting the tipping at the top. 

To adjust a sagging axle, loosen both locknuts, remembering 
that one is right-handed and the other left. Then, with the wheels 
jacked clear of the ground, tighten the turnbuckle. A long square 
should be procured or made so that the wheel inclinations may be 
measured before and after. Placing the square on the ground or 
floor, which should be selected so as to be perfectly level, the turn- 
buckle should be moved until the tops appear to lean outward about 
§ inch — some makers advise more. 

It should be borne in mind that even if the wheels and axle do 
not show the need of truss rod adjustment, if this rod be loose, it 
will become very noisy and rattle a great deal, as the rear axle sus- 
tains a great amount of 

Hose Clomp 

Fig. 458. Easy Method of Quieting Noisy Universal- 
Joint Housings 
Courtesy of "Motor World" 

jouncing. Moreover, this 
noise and rattle, if not 
taken up, will cause 
wear, which cannot be 
taken up. 

Disassembling Rear 
Construction. In disas- 
sembling the rear con- 
struction for* purposes of 
adjustment or repair, the 
repair man should be 
careful to mark all parts. Those parts which have been running 
together for several thousand miles act better and with less friction 
than would those which have never run together, despite the fact that 
the duplicate parte are supposed to be alike and interchangeable. 
It is therefore suggested that separate boxes be provided for the parts 
taken from the two ends or sides. The method of disassembling is 
about as follows: Jack up the axle, replacing the jack with small 
horses or blocks of wood if possible. Take off the hub caps, then 
free the wheels and take them off. Disconnect the brake-operating 
rods and levers and remove them from the car, marking them care- 
fully. Spread the brake shoes apart, loosen the springs at one side, 
take out the springs, and then loosen and take out the brake 
shoes themselves. Remove the brake operating shaft with the cams; 


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then disconnect the spring bolts and jack up the chassis, using the 
spring for a support. Disconnect all torsion or radius rods and take 
off the grease boot around the universal joint in the driving shaft. 
Open this joint and disconnect the shaft. Take this off and if the 
spring bolts have been removed, the rear axle will be free. Pull it 
out from under the chassis, and, if desired, further disassembling may 
be done more easily with the member clamped in a vice or laid on a 

Assembling, In assembling, almost the reverse of this process 
is followed, the parts going together in the opposite manner from 
that in which they were taken down. 

Noisy Bevel Gears. Bevel gears make a noise because they 
are poorly cut, because they are not set correctly with relation to 
each other, or because the teeth have become cut, or chipped, by 
some foreign material which has been forced between them. If the 
gears are sprung the noise will be irregular. 

In the first case, there is little the amateur can do beyond 
making the best possible adjustment and smoothing off any visible 
roughness. In the second case, it is simply a matter of setting one 
gear closer to or farther from the other by means of the adjustment 
provided. When the axle is disassembled, and all parts are readily 
accessible, it will be found that there is a notched nut on either 
side of each of the bevels; there should be a wrench in the tool kit 
to fit this. 

Repair for Broken Spring Clips. The springs are held down on 
the axles by means of spring clips, which are simply U-shaped bolts 
with the inside width of the U equal to the width of the spring. 
Occasionally, these will break when they cannot be replaced or new 
ones forged. LTnder such circumstances, a repair such as used by 
one man, shown in Fig. 460, will always get the car home or to a 
garage where a better one can be made. This method of repair 
consists of a pair of flat plates, one above the spring, the other below 
the axle, with holes drilled in the corners to take four long carriage 
bolts, which happened to be handy. The plates were put on, bolts 
put in and tightened up, and the car was ready to run. Although 
an I-section axle is shown in the illustration, this method of repair 
would work just as well on a round axle or on an axle of any other 

246 Digitized by 




Lining Up Axles. In such a repair, however, the main thing 
is to get the rear axle lined up correctly, which is not an easy job. 
This may be done in the following manner : Get the car standing level 
on a nice clean smooth floor; hold a large metal square with a plumb 
bob hanging down over its short edge against the side of the frame. 
Move the square forward until the line just touches the rear axle at 
some set distance out from the frame, say 3 inches, as shown in Fig. 
461. Then notice the distance this line is forward from the rear end 
of the frame. In the sketch it is 16 inches. Transfer the square and 
plumb bob to the other side and repeat. Here it will be found that the 
distance from the rear end of the frame is either more or less. In the 
sketch it is shown at 18 inches; so the difference, 2 inches, shows that 
the axle is out of alignment 
that much or half that, 1 
inch at each end. 

This axle is straightened 
by loosening the spring bolts 
and pushing one side back 
the distance apparently 
needed, then fastening 
tightly and checking up. If 
not correct, try again, using 
judgment as to which side 
should be moved. When 
finally satisfied that the rear 
axle is square with the frame, 
it is well to *check this against the center-to-center distance of the 
wheels on each side. This is done by setting the front wheels exactly 
straight and then measuring from the center of the right front to the 
center of the right rear wheel. Then go over to the other side and 
measure the center-to-center distance of the left wheels. The two 
axles should agree exactly. If they do not, the rear axle prusumably 
needs more adjustment for squareness. 

Taking Out Bend in Axle. A simple method of repairing an axle 
which has been bent, but a method which is only temporary in that it 
is not accurate enough to give a job which could be called final, is 
that indicated in Fig. 462. The axle was bent when the hub struck 
an obstruction in the road, and it had to be straightened immediately. 

Fig. 460. How Spring Clips Are Replaced 

in Emergency 

Courtesy of " Motor World" 


z * 



A short length of 2 x 4 timber was cut to be a tight fit between the 
upper side of the hub cap and the roof beam. Then a jack under the 

Fig. 461. Method of Checking up Rear-Axle Alignment with Square and Plumb Bob 

axle at the point of the bend was raised. As the jack raised the axle, 
and the wood beam held the hub down, enough pressure was exerted 

to force the axle to give at the 


Fig. 462. One Way of Straightening Rear 
Axle Quickly 

bend and return as nearly as 
possible to its original straight- 
ness. It was a quick and easy 
repair of the rough and ready 
order, which served when time 
was worth more than anything 
else; but it is a method which 
would not be advised or recom- 
mended when there was suffi- 
cient time to properly 
straighten the axle. 

Locating Trouble. Many 
times, a car may be brought 
in for rear-axle repair on which 
the repair man cannot find any 
trouble. Many axles often 
develop an elusive hum, or 
grinding noise, which not only 
defies location, but is not con- 
tinuous. The writer had such 
a case brought to him at one 


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time, and was sure that the bevel gears were out of alignment and 
were cutting each other. It was a low-pitched whine which was 
no.t apparent at low speeds, but began to be heard around 18 to 20 
miles an hour, and at times was very apparent. The noise was very 
annoying, but tearing down the rear construction showed absolutely 
no trouble; so the noise could not be at that point. Sometime later 
the noise was definitely located in a pair of worn speedometer 
gears on the right end of the front axle. 

A good way to listen to rear axle hums out on the road is to lay 
back over the rear end of the car, Fig. 463, with the head against 
the top of the seat and project- 
ing over slightly, and with the 
hands cupped in front of the 
ears, so as to catch every noise 
that arises. The larger sketch 
shows the general scheme, the 
small inset giving the method 
of holding the hands. When 
the sound arising from the axle 
is a steady hum, the gears are 
in good condition and well 
adjusted. If this sound is inter- 
rupted occasionally by a sharper, 
harsher note, it may be assumed 
that there is a point in one — - 

„ ,, , . Fig. 463. Listening for Rear- Axle Noises 

of the gears or on one of the 

shafts where things are not as they should be. By trying the car 
at starting, slowing down, running at various speeds, and coasting, 
this noise can be tied to something more definite, some fixed method 
of happening. In advance of actual repair work, including tearing 
down the whole axle, the gears can be adjusted. This can generally 
be done from outside the axle casing and without a great deal of work. 
If the adjustment makes matters worse, it can be reversed, or if it 
improves the situation, the adjusting can be continued, a little at a 
time, until the noise gradually disappears. 

Checking Up Ford Axles. Many cases of Ford bent rear axles 
can be fixed without taking down the whole construction. The prin- 
cipal point is to find out how much and which* way the axle is bent. 


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By removing the wheel on the bent side and placing the rig shown in 
Fig. 464 on the axle end, the extent of the trouble can be indicated by 
the axle itself. The iron rod is long and stiff, with its outer end 
pointed, and is fastened permanently to an old Ford hub. The 
rig is placed on the axle and held by the axle nut, but without the 
key, as the axle must be free to turn inside the hub. With the pointed 
end of the rod resting on the floor and with high gear engaged, have 
some one turn the engine over slowly, so as to turn the axle shaft 
around. As it revolves, the hub will be moved, and the pointed end 
on the floor will indicate the extent of the bend. By marking the 
two extreme points and dividing the distance between them, the 
center is found. Then a rod can be used as a bar to bend the axle, 
until the pointed rod end is exactly on the center mark. A little 

practice with this rig will 
enable a workman to 
straighten out a Ford rear 
axle in about the time it 
takes to tell it. 


Mark$ on Floori^ J 

Fig. 464. Diagram Showing Method of Checking 
Up Ford Axles 


Function of Brake. 

Next to power, applied 
through the correct form of 
gearing, and its final suita- 
ble drive to the road wheels, 
nothing is of more importance than the ability to stop the vehicle at 
will. One medium through which this is done, and which ordinarily 
suffices, is the shutting off of the source of power — in this case, the 
closing of the throttle which feeds the gas to the cylinders. This will 
not always suffice, however, for the ordinary car possesses the ability 
to run at a speed of 40 miles per hour or upward, and weighs from 2000 
pounds (one ton) upward to 4000 pounds (two tons). This combi- 
nation makes for a large force of inertia, which will result in the car 
running for many yards, even hundreds of yards, after the power is 
shut off. It is for this reason that we must have a mechanical 
means of absorbing this inertia, or of snubbing the forward move- 
ment of the car. This is the function of the brakes, as fitted to 
the modern car. 


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Engine as a Brake. Although disregarded in any summary of 
brakes, the engine is the best brake possible, granting that the driver 
knows how to get the best results without doing any damage. The 
ordinary engine has a compression of from 60 pounds to 70 pounds per 
square inch, which is practically the pressure available when it is used 
as a brake. As this pressure offers a great deal of resistance the brak- 
ing effect is self-evident. 

Classification. Brakes are usually divided into two classes, 
differing mainly in location — the internal expanding and the external 
contracting. To these a third class should be added, because it par- 
takes of the nature of both, yet differs from each one. This is the 
railway type of brake with removable shoes of metal, differing from 
the band type in that no attempt is made to cover the whole or even 
the greater part of the circular surface, but simply a small portion of it, 
against which a shoe is forced with a very high pressure. Both types 
are subject to division into other classes, the first into three sub- 
divisions according to operating means, viz., cam, toggle, and scissors 
action. The railway type of brake is no longer used. 

Brakes are generally divided according to their location, as shaft 
and rear axle. The shaft brake at one time virtually went out of use, 
but it is now being revived. The marked swing toward the unit 
power plant, together with its simplification, lightening, and elimina- 
tion tendencies, has produced a situation where a brake drum just 
back of the power and gear unit can be operated by the hand lever 
and a very short rod. In this way much weight and many parts are 
saved. An indirect advantage is that the brake is more accessible. 
With the worm drive, there is a marked tendency back to the shaft 
brake, particularly on motor trucks. Again, in the last few years, 
some work has been done with pneumatic, hydraulic, and electric 
forms of brake. With air under pressure for starting, and with water 
or electricity as needed for starting or for other purposes, it is a simple 
matter to utilize the same agency for braking, providing such use does 
not add too much complication and, at the same time, that it 
will give a superior method of snubbing the forward movement of the 
car. In case none of these advantages are realized, there will be no 
particular advantage in adding new forms of brake. 

External-Contracting Brakes. This class of brakes is divided 
into but two types, viz, single- and double-acting. In the first, an 





end of a simple band is anchored at some external point, while the 
other, or free end, is pulled. This results in the anchorage sustaining 
as much pull as is given to the operating end, that is, all pull is trans- 
mitted directly to the anchorage. This disadvantage has resulted 
in this form becoming obsolete. 

Any brake of the true double-acting type will work equally well 
acting forward or backward. The differential brake, Fig. 465, 
shows this clearly. The external band is hung from the main frame 
by means of a stout link which is free to turn. The band itself 
is of very thin sheet steel, lined with some form of non-burnable belt- 
ing. The ends carry drop forgings, to which the operating levers are 
attached. These are so shaped that the pull is evenly divided between 
the two sides of the band. This will be made apparent by considering 

that a pull on the lever H will 
result in two motions, neither 
one complete, since each depends 
upon the other. First, there will 
be a motion of the upper band 
end B about the extremity of the 
lower one as a pivot, followed by 
a movement of the lower end, 
pivot and all, about B as a second 
pivot point. These two motions 
result in a double clamping action 
which is supposed to distribute evenly over the surface. - In order to 
insure even distribution, the lining is grooved, or divided, into 

Usually, chain-driven cars have a different brake location from a 
car with shaft drive. Some of these cars have three sets of brakes: 
one on the main shaft, one pair on the countershaft, and another pair 
on the rear wheels. 

Internal-Expanding Brakes. While the contracting-band brake 
is well thought of, the internal-expanding form is rapidly displacing 
it, for the reason that experienced drivers think more of it. In Fig. 467 
will be seen a modern form of the internal brake, namely, the use of 
both brakes as internal, but placed side by side in the same drum. 
This is a tendency which seems to be gaining in favor. The car is the 
Owen Magnetic, one of the most expensive and luxurious; so the use 

Fig. 465. Brake on Main Shaft of 
Benz (German) Car 


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of side-by-side internal brakes here must be attributed to superiority 
rather than to a desire to save in money or in parts. 

A considerable number of foreign cars, which are used in moun- 
tainous countries, show a method of cooling the brake drums by means 
of external cooling flanges. In some makes, even a water drip is 
provided for extremely hilly country. 

More modern practice shows no tendency to place all of the eggs 
in one basket, both forms of brake being employed together and upon 
the same car, usually also upon the same brake drum, one set working 

Fig. 466. Showing the 1920 Overland Four Brake Construction 
and Method of Adjustment 

upon the exterior, while the other works upon the inside. In Fig. 468, 
which shows the rear-axle brakes of the larger cars made by the 
Peerless Motor Car Company, this mechanism is plainly illustrated, 
both the brakes being shown, although the drum upon which they 
work has been removed. The parts are all named so as to be self- 
explanatory. In this construction, the inner, or expanding, band is 
operated by a cam. In the brake sets put out by the Timken Roller 
Bearing Company, of Detroit, Michigan, in connection with their bear- 
ings and axles, the toggle actioQ is used, Fig. 469. The constructional 
drawings, Figs. 470 and 471, showing the brakes used on the Reo 
car, manufactured by the Reo Motor Car Company, of Lansing, 


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Michigan, indicate that this firm is partial to the cam for brake opera- 
tion, since these are used for both internal and external brakes, the 

Fig. 467. Rear Axle of Owen Magnetic Car with Wheel Removed to Show Brakes 
Courtesy of Baker-R & L Company, Cleveland, Ohio 

Fig. • 468. Peerless Rear-Axle Brake 

internal form having a split link connected to the toggle, while the 
external has a link movement in contracting much like that shown 
in Fig. 465, which is there explained in detail. 


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In general, however, when both brakes are placed on the rear 
wheels, one external and of the contracting-band type, and the other 
internal and of the expanding-shoe 
form, modern practice calls for a 
cam to operate the latter, oper- 
ating directly upon the ends of 
the two halves of the shoe, while 
levers operate the band so as to 
get a double contracting motion. 

Some modern brakes may be 
seen in Figs. 472, 473, and 474. 
The first shows a system such as 
just described; the second shows 
a stiff metal shoe in both types; 
and the last a pair of shoes set 
side by side. In addition, the last- 
named includes a new thought in Fig. 469. Timken Double Rear-Axle Brake 

Fig. 470. Section Showing Construction 
of Reo Brakes 

Fig. 471. Drawing Showing Method of 
Operating Reo Brakes 
Courtesy of Reo Motor Car Company, Lansing, Michigan 

that the brake shoes are floated on their supporting pins, as shown. 
This makes the bearing of the shoes certain when expanded against 
every portion of the drum, as the shoes can "float" until they fit exactly. 


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Double Brake Drum for Safety... A very important feature is 
pointed out in Fig. 472, namely, that of safety. Where both brakes 
work on a common drum, one inside and the other outside, the con- 
tinuous use of the service brake (whether internal or external) heats 
up the drum to such an extent that when an emergency arises calling 
for the application of the other brake it will not grip on the hot 
drum, being thoroughly heated itself. The double drum allows air 
circulation and constant cooling. 

Methods of Brake Operation. While it is generally thought that 
round iron rods are the universal means of brake operation, such is not 
the case. Many brakes on excellent cars are worked, as the illus- 
trations show, by means of cables. This idea is even carried so far 

Fig. 472. Double Brake Drum Used on Locomobile Cars 

that brakes have been fitted to operate through the medium of ropes. 
Chains of small diameter have also been used, as well as combinations 
of rods, chains, cables, and ropes. 

A lever-operated braking system of a well-known medium- 
priced car is shown in the outline sketch, Fig. 475. In this system the 
forward part of each half is worked by rods moved by means of 
pedals, but the rear part of each half is actuated by means of cables. 
Cables have one advantage over rods in a situation like this — the 
diagonal pull with a stiff rod might, in time, act to pull the brakes side- 


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Fig. 473. Brakes and Rear Construction of Pierce Cars 
Courtesy of Pierce- Arrow Motor Car Company, Buffalo, New York 

1V minnninmivmii 

Fig. 474. Side-by-Side Arrangement of Brakes on American Rear Axle 
Courtesy of American Ball Bearing Company, Cleveland, Ohio 


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wise off their respective brake drums, the cable, being more flexible, 
gives less danger of this. 

This method of operation seems to be gaining favor because of 
its simplicity, which eliminates parts that add weight and gives 
immediate results when the parts are properly adjusted. The recent 
New York show revealed a surprising number of small and medium 
size cars with cable-operated brakes. An inspection of these cars 
showed a mechanical cleanliness which was lacking in many others of 
the same class on which an attempt was made to reduce braking rods 

Fig. 475. Layout of Brake-Operating System Using Cables 

and levers to a minimum, with consequent bent levers, bent or crooked 
rods, brakes worked from an angle, and other unmechanical ideas. 
Fully as important as the operating means is the matter of 
equalizing the pull so that the same force is exerted upon both wheels 
at once. This action is influential in causing side-slip or skidding, 
which may result fatally. To equalize the force was one reason for 
the use of cables, although the more up-to-date way is to attach the 
operating lever to the center of a long bar, to the extremities of which 
the brakes themselves are fastened. A pull on the bar is then divided 
into two different pulls on the brakes, the division being made 
auton itically and according to their respective needs. This is an 


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important point, and one that should be looked after in the purchase 
of a new car. 

Brake Adjustments. In recent years much of the brake improve- 
ment has been that of making adjustments easier and of making the 
adjusting parts more accessible. This can be noted in such a case as 
the Locomobile, Fig. 472, where the special adjusting handle on the 
brake is carried to such a height as to make the turning of it an easy 
matter. Similarly, on the Pierce, Fig. 473, it will be noted that 
there is provision for increasing or decreasing the closeness of the 
shoes to the drum, which is easily accessible. 

Brake Lubrication. As for the actual brake surfaces, there is no 
such thing as lubrication. The surfaces should be kept as dry and 
clean as possible. If grease or oil gets out from the axle or other 
lubricated parts onto them, there is sure to be trouble. The operating 
rods and levers, however, should have fairly careful lubrication, for 
which purpose the best makers provide grease or oil cups at all vital 
points. If these be neglected, a connection may stick, so that when 
an emergency arises the brake will not act properly and an accident 
may result. 

Recent Developments. In the last few years, the only new 
ideas advanced in the way of brakes concern front-wheel braking 
and electric brakes. The former were used quite extensively abroad 
in 1913, but in 1914 they seemed to drop back; this, too, despite the 
fact that the Grand Prix race of the latter year showed in a marked 
manner the need for and special application of front-wheel brakes to 
racing and high-speed cars. 

Electric Brakes. A very efficient and compact brake, appli- 
cable with a small amount of work to any chassis having a storage 
battery, is the Hartford, shown in Fig. 476, while Fig. 477 shows the 
operating lever as it is placed beneath the steering wheel, and .Fig. 478 
shows the wiring system. This brake consists, in substance, of a 
small reversible electric motor, to which a 100 to 1 worm reduction is 
attached. Attached to the drum is a cable, which is fastened to the 
usual brake equalizer. Turning the current into the motor from 
the storage battery rotates the drum, winds up the cable, and applies 
the brake. The complete outfit weighs but 35 pounds. The motor has 
a slipping clutch set to operate at 1000 pounds pull, at which it draws 
40 amperes of current from the battery for two-fifths of a second. 


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Fig. 476. Exterior of Motor Which Forms Central 

Unit of Hartford Electric Brake 

Courtesy of Hartford Suspension Company, 

Jersey City, New Jersey 

Fig. 477. Hand Lever on Steering Poet for 
Operating Hartford Electric Brake 


o— • 


Fkg. 478. Wiring Diagram for Hartford 
Electric Brake 

In use, it replaces the emer- 
gency hand-operating lever, 
and is said to be able to pull 
a heavy car going 50 miles an 
hour down to less than 15 in 
a distance of less than 35 
feet. The pull is so great 
that the brake drums are 
oiled to prevent heating and 
possible seizing. 

Hydraulic Brakes. On 
the newer Knox tractors, a 
brake of very large size is 
made even more powerful by 
hydraulic operation. This 
brake is shown in Fig. 479. 
At the left will be seen the 
usual brake lever attached to 
a small piston in a chamber 
full of liquid. This chamber 
communicates through the 
medium of a valve normally 
held closed by a spring, with 
a passage above, and that, in 
turn, communicates with the 
pipes leading to the brake- 
operating cylinder. This cyl- 
inder has a stout rod attached 
to a good size plunger, back 
of which the liquid (oil) is 
introduced. When liquid is 
forced in, the plunger moves 
forward, forcing, the rod out 
and, through connecting rods 
and levers, applying the 
brakes. As will be seen in 
the drawing at the right, 
these brakes, which are of the 


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internal-expanding type, are exceptional in size and work against 
steel .drums attached directly to the wheel spokes. 

When the lever is drawn back in the usual manner, liquid is 
forced upward through the top passage to and through the pipes 
into the other cylinder, forcing the plunger to move, and, through the 
movement of the plunger, the brakes are applied. The return of the 
fluid is not shown, but it is assumed that this is through a simple pipe 
connected from the plunger cylinder to the hand-operated piston with 
a check valve. Should the initial movement of the lever fail to apply 
the brakes sufficiently, the driver can let the lever come forward and 
then pull it back again; in so doing he will take into his lever cylinder 

Fig. 479. Layout of Hydraulic Brakes Used on Knox Tractor 
Courtesy of Knox Motors Company, Springfield, Massachusetts 

more liquid from below without releasing the brakes. Then, when 
this extra quantity is forced through, the plunger is moved even 
farther forward, and the brakes applied more forcibly. The brakes 
are 20 inches in diameter by 6| inches wide. 

Dragging Brakes. Probably the first trouble in the way of 
brakes is that of dragging, that is, braking surface constantly in 
contact with the brake drum. This should not be the case, as springs 
are usually provided to hold the brake bands off the drums. Look for 
these springs and see if they are in good condition. One or both of 
the brake bands may be bent so that the band touches the drum at a 
single point. 





Another kind of dragging is that in which the brakes are adjusted 
too tightly — so tightly, in fact, that they are working all the time. 
In operating the car, there will be a noticeable lack of power and 
speed, while the rear axle will heat constantly. This can be detected 
by raising either rear wheel or both by means of a jack, a quick 
lifting arrangement, or a crane, and then spinning the wheels. If 
the brakes are dragging, they will not turn freely. 

All that is needed to remedy this trouble is a better adjustment. 
For the new man, however, it is a nice little trick to adjust a pair of 
brakes so that they will take hold the instant the foot touches the 
pedal, that they will apply exactly the same pressure on the two 
wheels, and yet will not run so loose as to rattle nor so tight as to drag. 
Dummy Brake Drum Useful. Where a great deal of brake 
work is to be done, particularly in a shop where the greater part of 

the cars are of one make, 
and the brakes all of one 
size, a great deal of time and 
trouble can be saved by 
having a set of test drums. 
An ordinary brake drum 
with a section cut out so 
that the action inside may 
be observed is all that is 
necessary, except that it 
should be mounted suitably. As shown in Fig. 482, it is well to fit 
a pair of handles to the brake drum to assist in turning the drum when 
the adjustment is being made. The real saving consists of the work 
which is saved in putting on and taking off the heavy and bulky wheel 
each time when the adjustment is changed. The test drum is put 
on instead, and it is easily and quickly lifted on and off. 

To Stop Brake Chattering. It is claimed that the chattering 
of brakes is caused by having the brake lining, particularly of internal 
hand brakes, extend over too large a portion of the circumference of 
the drum. The result is that with a well-adjusted system, as soon as 
force is applied, the lining close to the operating cam and that on 
the opposite side close to the pin on which the brake shoes are 
pivoted jumps against the drum and then away from it. This 
jumping of the brake shoe, which is the result of too much lining, is 

Fig. 482. Dummy Brake Drum for Adjustment Work 


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what causes the chattering. If the lining is cut away for about 30 
degrees on either side of a line drawn from cam to pivot pin, as shown 
in Fig. 483, it is said that this chattering will stop immediately. 
If further trouble of the 

r Lining Cut fl**au Hera 

same kind results, bevel off 
the outside ends of the lining 
at the two 30-degree points. 

A number of sugges- 
tions in the way of possible 
brake troubles, particularly 
on the side-by-side form of 
internal-expanding brakes, 
are indicated in Fig. 484. 
This shows a semi-floating 
form of rear axle with the 
two sets of brakes and oper- 
ating shaft and levers. A 
number of suggestions are offered for this form, the most important 
of which is: "Renew worn brake lining and broken or loose rivets." 

When a brake lining is worn, the proceeding is much the same 
as with a clutch leather, with the exception that whereas the latter 

Clear? ft- mfifl rtm* 


Fig. 483. Method of Eliminating Brake Chattering 
on Internal-Expanding Brakes 

Fig. 484. Brake Troubles Illustrated 

must have a curved shape, the former can be perfectly straight and 
flat. This simplifies the cutting; but most brake linings are made of 
special heatproof asbestos composition which is made in standard 
widths to fit all brakes, so the cutting of leather brake bands is not 
often necessary. 


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Eliminating Noises. Many times the brake rods and levers 
wear just enough to rattle and make a noise when running over 
rough roads or cobblestone pavements, but hardly enough to war- 
rant replacing them. -The replacement depends on the accuracy 
with which they work, the age and value of the car, and the attitude 
of the owner. In a case where the owner does not desire to replace 
rattling rods, the noise can be prevented by means of springs, winding 
with tape, string, etc. 

If the rod crosses a frame cross-member or is hear any other 
metal part, and its length or looseness at the ends is such that it can 

be shaken into contact there, a rattle 
will result at that point. This can 
be remedied or rather deadened by 
wrapping one part or the other. For 
this purpose, string or twine can be 
used as on a baseball bat or tennis 
racket handle, winding it together 
closely so as to make a continuous 
covering. Tire or similar tape may 
also be utilized. When this is done, 
it is necessary to lap one layer partly 
over the next in order to keep the 
whole tight and neat. It has the ad- 
ditional advantage of giving a greater 
thickness and thus greater resistance 
to wear. If none of these remedies 
I&tc^ are available or sufficient, burlap in 

courtesy of "Motor world" strips or other cloth may be used, 

putting this on in overlapping layers the same as the tape. 
The springs should be put on in such a way as to take up the 
lost motion and hold the worn parts closer together. The rattle 
occurs when the movement of the car alternately separates and pulls 
together the two parts, a noise occurring at each motion. The 
spring should be put on so as to oppose this motion, acting really 
as a new bushing or pin, the pull coming first upon the spring and then 
upon the bushing or pin. 

Stretching Brake Lining. Brake lining should be put on as 
tightly as possible, and the knowledge of this, combined with the 


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difficulty of doing it by hand, makes the stretching device shown in 
Fig. 485 particularly valuable when much brake relining is to be done. 
This is a simple pulling clamp, which is attached to one end of the 
lining after the first end has been riveted in place. Then it is 
attached to the end of the shoe, and the nut tightened so as to stretch 
it. When it has been stretched sufficiently, the other rivets can be 
put in, or the shoe and band with the stretches in place can be laid 
aside for a while to stretch it fully before fastening. Obviously, this 
is applicable only to the internal- 
expanding form, but the hook 
and clamp can be used on any 
size or type of expanding brake. 
Truing Brake Drums. When 
both inside and outside surfaces 
of the brake drum are used, it is 
highly important that both be 
true. Since they do not stay that 
way long, the repair shop should 
be equipped to true them up 
quickly. A truing device is shown 
in Fig. 486, with the wheel and 
brake drum in place on it. One 
feature of the device is that brake 
drums need not be removed from 
the wheel. The device consists 
of a metal base having a strong 
and stiff wooden pier with a hori- 
zontal arm the exact size of the 
axle end mounted on it. The 
wheels are placed on the arm and 
rest on it the same as on the axle when on the car. The tool is 
double, with two ends, one of which cuts the inside surface of the 
drum, while the other cuts the outer surface. At the center this tool 
is attached to a heavy casting, bored out to slide over the shaft and 
with a key fitted into a keyway in the shaft to prevent the tool from 
rotating. The end of the arm is threaded, and a large nut with two 
long arms is screwed up against the tool at the start, and then it is 
used to feed the latter across the work. 

Metal Base- 

Fig. 486. Apparatus for Truing Inside and 

Outside of Brake Drum in Place on Wheel 

Courtesy of "Motor World " 


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This is subject to a number of modifications to fit it to the various 
sizes and shapes of brake drum. Another method is to use the lathe, 
provided the shop is equipped with a lathe large enough. By making 
a mandrel the same as the axle spindle and having a pair of dummy 
bearings to place on it, the brake drum can be slipped on to the 
mandrel, and the whole put right into the lathe. The surface, either 
internal or external or both, can then be trued up exactly as if the 
drum were on the axle. 


Broadly speaking, there are but two kinds of wheels according 
to the service each is to render, pleasure-car wheels and commercial- 
car wheels. The former may be further subdivided into wood, wire, 
and spring wheels; while the latter may be divided into wood, steel, 
and spring wheels. Some of the commercial vehicle wheels are 
further divisible, as steel wheels into sheet steel and cast steel; 
wood into spoked and solid; and spring wheels into various types. 

Wheel Sizes. Wheels are used on automobiles, in combination 
with the tires, to afford a resilient and yielding contact with the 
surface of the road, so that people may ride with comfort. Therefore 
a wheel whose size is such as to yield the most comfort to the car 
occupants with due regard to its cost relative to the cost of the vehicle 
is the wheel to use. The cost of the wheels themselves, however, 
is so small in comparison with the cost of the pneumatic tires which 
are used on them as to be completely overshadowed by the latter. 

Where comfort is sought as the prime requisite, cost becomes an 
accessory. The larger the wheel used the better the car will ride, 
and the greater will be the comfort of the occupants. This state- 
ment can be proved, although the gradually increasing sizes of wheels 
and tires as used on the best cars, both here and abroad — advancing 
from the early 26 and 28 X 3-inch tires, to as high as 38x5J-inch 
tires, and freaks up to 48 X 12-inch — should be sufficiently convincing. 

Advantages of Large Wheels. A graphical demonstration of the 
difference between the action of the large and small wheel to the 
advantage of the former is shown in two drawings, Figs. 487 and 
488. Fig. 487 presents the case of wheels passing over a common brick 
4 inches wide by 2 inches high, and Fig. 488 shows the action in 
passing across a small rut in. the surface of the road, 8 inches wide 


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by 1 J inches deep. In both cases, A shows the 28-inch wheel and B 
shows the 40-inch wheel. Both instances, too, have been selected at 
random, and not so chosen as to favor either wheel. It would have 
been possible to so select the sizes of both obstruction and depression 
as to make out a stronger case. 

The height of the brick being 2 inches the wheel must rise that 
distance, whatever its diameter, but in the case of the 28-inch wheel, 
this rise of 2 inches is largely relative to the wheel diameter being 
one-fourteenth, or 7 per cent. In the^case of the larger wheel of 
40-inch diameter, the rise is again 2 inches, but it is now one- 
twentieth of the wheel diameter, or 5 per cent. In the case of the 

Fig. 487. Diagram Showing Advantage of Large Wheels in Passing over Obstruction 

smaller wheel, the rise is distributed over a length of about 18.43 
inches from the moment when the forward edge strikes the 
obstacle to the moment when the last part of the tire leaves the 
last edge of the brick. If this rise were evenly distributed over 
this distance, rising as an arc of a circle, its radius would be slightly 
over 22 inches. 

Considering the 40-inch wheel under the same circumstances, it 
performs the act of rising and falling 2 inches in the longer distance 
of about 21.5 inches, the radius of this rise being 38.75 inches. It is 
obvious that the latter is a much easier rise than the former, the 
lift being distributed over a length 16 per cent greater. Similarly, 
with the descent from the high point to the surface of the road again, 


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this more gradual rise and fall convert the surmounting of the 
obstacle from a sharp upward bump and downward jounce into an 
easy and not unpleasant swinging up and down. 

A drop into a hole, as illustrated by Fig. 488, shows the bene- 
ficial effect of the large wheel better, perhaps, than does the rolling 
over a rise. A rut in the road 8 inches across, into which the two 
wheels drop in passing, is shown. At A, the 28-inch wheel is seen to 
drop the considerable amount of -& inch, while at B the 40-inch 
wheel drops but f inch into the same hole. Evidently the larger 
wheel has an advantage in so far as passing over obstacles or holes 
is concerned. 

Again, on account of its larger radius, the arc of the larger 
wheel is flatter and has more length of tread in contact with the 

Fig. 488. Diagram Showing Advantage of Large Wheels in Passing over Depression 

surface of the ground, this being particularly noticeable on rough 
roads. Not alone does this mean added adhesion to the ground and 
thus lessening driving effort to propel the same car, but it also means 
a greater resistance to side slip or skidding, thus conserving the 
power and increasing the safety of the occupants. Other arguments 
could be offered in favor of large tires for easy riding, but those 
given should suffice. 


Wood Wheels. Wood wheels are the most common form for 
pleasure cars in this country, being almost universal. Ordinarily, 
they are constructed of an even number of spokes, which are tapered 
at the hub end and rounded up to a small circular end with a shoulder 
at the rim, or felloe, end. Fig. 489 shows this construction, A being 


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Fig. 489. Construction of Wood Wheels 

the felloe on which is the rim B, and R is the spoke which, at the hub 
end, tapers down to the wedge-shaped portion P. This matches up 
to the wedge-shaped ends of the other spokes, so that when the 
wheel is assembled they form a continuous rim around the central 
or hub hole. 

The spokes are held at 
their inner ends by metal 
plates and by through bolts, 
which are set at the joints 
between the spokes so as to 
pass equally through each 
spoke, as shown at D. Not 
only do these bolts hold the 
spokes firmly to the wheel, 
but they have an expand- 
ing, or wedging, action 
tending to make the center of 
the wheel very rigid. 

The outer end of the spoke has a shoulder E and a round part C, 
which fits into a hole bored through the felloe. To prevent the 
felloe coming off after the spoke is in place, the spoke is expanded 
by means of a small wedge driven into it from the outside, as shown 
at F. In this way, the wheel is 
constructed from a series of com- 
ponents into a strong rigid unit. 

Such wheels wear in two 
places, at the inner and at the 
outer ends of the spokes. The 
remedy in the latter case is to 
withdraw the small wedge and 
insert a larger one in its place. 
At the hub end, when wear occurs, 
this, too, must be taken up by 
means of wedges. Fig. 490 shows 
a method of doing this when 

Kg. 490. 

Method of Tightening Spokes 
of Wood Wheels 

the hub has no bolts at the 

joints. A false steel hub A is driven into the hub hole, after 
which wedges of steel are driven in between the wedge-shaped ends 
of the spokes. For slight cases of wear and squeaks, the wheel may 


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be soaked in water, which will cause it to swell, taking up all of 
the space. 

There are various modifications of this, nearly all of them 
changing the hub end of the spoke. In the Schwartz wheel, a patented 
form, each spoke is made with a tongue on one side of the wedge- 
shaped part and a groove on the other. In assembling the wheel, 
the tongue of each spoke fits into the groove of the spoke next to 
it, thus rendering the whole hub end of the wheel, when assembled, 
a stronger unit, being stronger in two directions, one of them of 
more than ordinary value. In driving the tongue into the groove, 
the wheel is rendered strong in a radial direction, but, when the wheel 

Fig. 491. Details of Wood Wheels with Staggard Spokes 

is entirely assembled, the tongue-and-groove method leaves it very 
strong to resist side shocks, a point in which the wood wheel is weakest. 
Staggered Spokes. As mentioned above, the wood wheel has 
little lateral strength, nor can it ever have, from the very nature of 
its construction, except in unusual cases, like the Schwartz patent 
wheel just described. A method of increasing the lateral strength 
somewhat is that of using staggered spokes, these being alternately 
curved to the outside and to the inside, as shown in Fig. 491. This 
gives one set of half the spokes forming a very flat cone with its 
apex, or point, at the inner side of the hub, while the others form 
another cone with its apex at the outside of the hub. Each one of 


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these conical shapes is stronger to resist stresses from the side on 
which the point is located than would be the same number of spokes 
set flat. Hence, the staggered-spoke wheel has the advantage over 
the ordinary type in that it has greater strength from both sides. 
In the figure, A is the iron hub, B the felloe, Ci the right-hand and 
C 2 the left-hand spoke, and D the steel rim for the tire. This is a 
12-spoke wheel, 6 of the right-hand spokes Ci and 6 of the left-hand 
spokes C2. The section shows how these pass alternately to the one 
side or to the other, forming the strong cone shape. 

Fig. 492. Section of Steel 
and Wood Wheel 

Fig. 493. Complete Steel and Wood 
Truck Wheel 

Another method of handling this problem in a somewhat similar 
manner is the use of double sets of spokes, the spokes, however, being 
in two different planes separated a considerable distance at the hub. 
Of a necessity using the same felloe, the outer ends must be in the 
same plane. Fig. 492 shows a drawing representing a section through 
the center line of the wheel, while Fig. 493 shows a photographic 
reproduction of it. 

In Figs. 492 and 493, A represents the steel rim on the felloe 
F, the latter being of metal in this case, as is also the wheel so it 


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may be disassembled. The spokes R have a tubular end piece of metal 
G, which is set over the rounded end of each spoke and fits into a 
hole in the felloe. I and S are, respectively, the inner and outer 
parts of the hub, which are held together and to the spokes by means 
of the bolts N. Z is the hub cap, while U and V are filler pieces 
aiding in the dismantling process. The strength of the wheel is self- 
evident, but it is difficult to see the advantage of the disassembling 
feature, as a stress or strain which would break one spoke, would, in 
almost every case, break practically all of the spokes, thus neces- 
sitating a new wheel instead of new spokes. 

Wire Wheels. Many of the little details of the automobile 
were inherited from its predecessor, the bicycle. Among these may 
be mentioned the wire wheel." Practically all bicycle wheels were 

and are of the wire-spoked type, 
and this same form of wheel was 
used on all earlier automobiles. 
It had no strength in a sidewise 
direction, nor did it, in fact, have 
much of anything to recommend 
it except its light weight. For 
this reason, it failed in automobile 
service, and received a setback 
from which it has even now not 
wholly recovered. 
Early Bicycle Models. Fig. 494 shows an early type of wire 
wheel for automobiles, its construction indicating clearly its bicycle 
ancestry. The spokes were set into a casting, which formed the hub, 
and into the steel rim by means of a threaded sleeve, the head on 
each end of the spoke resting on the inner end of the sleeve. The 
sleeves were screwed in and out to adjust the tension of the spokes. 
This tension was usually considerable, thus reducing in part the 
ability of the wheel as a whole to resist side stresses, for the piece 
already in tension could not be expected to sustain additional ten- 
sion, or compression, or a combination of either with torsion, accord- 
ing to the way the force was applied. Then, too, the casting for 
the hub was wholly unsuited to resist stresses, and the distance apart 
of the spokes at the hub was not sufficient, making the cone so very 
flat that it had very little more strength than a perfectly flat wheel. 

Fig. 494. Hub Details of Bicycle Wheel 


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Following the failure of wire wheels, there was a rapid change 
to wood wheels, which were almost universal for several years. 
Soon after this change was made, there was an increase in the size 
and power of automobiles, which, in turn, was followed by a demand 
for lessened weights. In the meantime, makers of wire wheels, 
knowing their faults, began to re-design in order to eliminate them. 
Their success is best evidenced abroad, where about one-half of the 
French and more than two- 
thirds of the English cars, 
in addition to over seven- 
eights of the racing cars 
in both countries, are now 
equipped with wire wheels. 

New Successful 
Designs. This result has 
been brought about by a 
realization of the previous 
defects and their elimina- 
tion. Thus, no more cast 
hubs are used, drawn or 
pressed steel of the highest 
quality and greatest 
strength being used instead. 
The spokes have been car- 
ried out farther apart at 
the hub, obtaining a higher 
cone and thus a stronger 
one. Spoke materials are 
better and stronger, besides being used in greater quantities, that 
is, larger spokes and larger numbers of spokes per wheel, in some 
cases a triple row of spokes being used in addition to the ordinary 
two rows. This additional row acts as a strengtherier and stiffener 
much like the diagonal stays on a bridge. Fig. 495 shows a set of 
double-spoke wire, triple-spoke wire, and interchangeable wood 
wheels side by side for comparison, while in Fig. 496 is presented 
a recent triple-spoke front wheel in detail. 

In the former figure, the relative depths of the various cones 
and their corresponding strengths are made evident, beins; side by 


Fig. 495. 

Sections of Double and Triple Steel and 
Wood Spoke Wheels 


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side. In this comparison, it will be noted that the new triple-spoke 
wheel has a much longer outer cone than the double-spoke wheel, 
while, on the other hand, the inner cone has been flattened. The 
triple spoke has a greater depth, considering the set of them as an 
additional cone, than has the inner cone in the double-set wheels. 
In examining closely the older double-spoke form and the newer 
triple type, it will be noted, also, how the 
wheel itself, or rather the tire and rim, 
have been brought closer in to the point of 
attachment, thus rendering the whole con- 
struction stronger and safer. In Fig. 495, 
it will be seen that the center line of 
both tire and rim passes midway between 
the inner and outer ends of the hub on 
double-spoke wheels, while on the triple 
form it is even with the inside end of the 
inner hub, being, in fact, farther in than 
is the case with the wood wheel. One 
thing will be noted in all these spokes, 
regardless of number, position, or inclina- 
tion, and that is that their ends present a 
straight head. On the older bicycle spokes, 
the diagonal-spoke head was a great source 
of weakness, tending to create failure at 
the outset. The modern wire wheel is so 
constructed as to do away with this fault. 
By actual tests, the wire spoke — not the 
stronger triple spoke but the double spoke — 
has been found to have the following 
advantages: lighter weight for the same 
Details of Tripie-Spoke carrying capacity; greater carrying capac- 
Front wheel ^ f QT e q Ua j weight ; superior strength from 

above or below in the plane of the wheel; lower first cost (it is doubtful if 
this will hold good for the newer triple-spoke forms) ; and, in addition, 
tests have proved superior strength in a direction at right angles to 
the plane of the wheel. So marked is the difference in weight of the 
two that five wire wheels are said to be lighter in weight than four 
wood wheels of equal carrying capacity. 

Fig. 496. 


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All these arguments in favor of wire have been built up one by 
one, for much prejudice had to be removed. In spite of this, however, 
the wheel is slowly but surely building up a reputation and a long 
list of friends. Since, even now, England and the Continent continue 
to set the fashion in automobiles, it is not too much to expect to 
see wire-spoke wheels in common use in the United States in a few 
years. In fact, the dozen manufacturers 
offering this wheel in 1914, with ten more, 
giving it as an option, have been increased 
to about forty who are fitting it regularly, 
with perhaps fifty or more offering it as an 
option in 1915. In fact, almost any 'car 
maker in the country will fit wire wheels 
for a slight additional charge. 

For 1917 some 20 odd makes of "cars 
are offered with wire wheels as 'regular 
equipment, and about 25 more offer this 
as an option without extra charge. As 
there are about 190 cars on the market, 
the former represents 10.5 per cent, and 
the latter 13.2 per cent of all makes; the 
two together total 23.7 per cent, or less 
than one-quarter. However, these figures 
do not quite indicate the relative popu- 
larity of wire wheels. 

Wire Wheels Much ' Stronger. , The 
increase in the use of wire wheels has 
been brought about by better designs; 
greater attention to the details of manu- 
facture, assembly, and use; but primarily 
by the greater strength which has been 
built into the wire wheel. One way in 
which this has been done is by rearrange- Spoke Wtre 

ment of the spokes as, for instance, the triple-spoke form just 
described and shown in Fig. 469. Another and later form is the 
quadruple-spoke wheel as seen in Fig. 497. This is made and sold by 
the General Rim Company, Cleveland, Ohio, and is called the G-R-C 
wheel. As the sketch indicates, it has all the features of demount- 

Fig. 497. G-R-C Quadruple- 



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ability, etc., of other wire wheels, the notable differences being the 
spoke arrangement to give strength and the form of rim — a patented 
form to be described in detail later. 

By comparison with Fig. 496, it will be noted that a double 
triangular section is formed in the G-R-C, the inner spokes forming the 
inside of the hub and the outside of the hub forming one triangle, 
while the outer ^spokes from each form the other. In Fig. 496, it 
will be noted that there is but the one triangle and a straight row 
of spokes. 

Sheet-Steel Wheels. The sheet-steel wheel is really a form of 
wire-spoke wheel, with an infinite number of spokes joined together. 
It has many advantages, some of which might be mentioned as 
follows: strength, lightness, low first cost, low cost of maintenance, 
and cleanliness. To take them up in order, the strength of two steel 
plates set a few inches apart in a somewhat triangular form with 
the base toward the hub and well attached at the center and at the rim 
of the wheel, is self-evident. Aside from the natural strength of the 
steel plates — far in excess of the wire spokes — or round wood spokes, 
there is the strength of the triangular form. A strong connection at 
the top and at the bottom makes the whole construction very similar 
to a structural form. This shape closely resembles a box girder, 
having great resisting strength in all directions. 

The light weight of the steel wheel comes from the thinness of 
the steel plates which are used, and similarly from the thin and light 
connecting members, either top or bottom. In Fig. 498 the junction 
at the top is seen to be nothing more than the steel rims for the tire, 
thus doing away with the usual felloe or substitute for it. In this 
figure, the wheel is seen to consist of the hub made with two flanges, 
to which the side sheets are bolted; the brake drum I bolted to the 
sheet on the inside, midway up its height; the steel rim mentioned 
before; and the bolts and rivets necessary to join the parts. At 
the hub, bolts are used to allow of dismounting the sheets in case of 
damage, for replacement or otherwise. At the rim, however, the 
plates are riveted to the rim, and riveted together. 

Low first cost is brought about by the simplicity of the wheel. 
The wheel consists of the usual rim, not counted in the wheel cost, 
and two pressed-steel sheets flanged at the top, with a few holes 
punched in them. These sheets are very cheap to make, while the 


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hub construction is much cheaper than the ordinary hub, for the 
reason that there are usually two parts where this cbnstruction 
requires but one, and this a very simple one needing little machining. 
Low maintenance cost is brought about by the rigidity of the whole 
construction; the few parts, which make few to replace or even to 
wear; the cheapness of these parts, when replacement is necessary; 
and the well-known strength and long life of sheet-steel plates. 

On the score of cleanliness, it may be said that this is one of 
the drawbacks of the wire-spoke wheel, cleaning between and around 


Fig. 498. Side and Sectional Views of Sheet-Steel Wheels 

the spokes being very difficult, if not actually impossible. The 
large number of spokes makes the hub inside of the spokes impossible 
to clean, whereas, with the sheet-steel wheel, the cleaning consists 
in merely turning a hose on the sides of the wheel, the cleaning of 
the hub being entirely unnecessary. 

It will be noted, too, in this illustration that the wheel has 
considerable spring, or should have, in a vertical direction. It is 
claimed for this type of wheel that this springiness is an added 
advantage as it allows the use of solid or cushion tires, and thus 


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eliminates the troublesome~pneumatic tire with «its puncture and 
blowout possibilities. For commercial-car use, all of the advantages 
just mentioned are of double worth, for which reason the steel wheel 
is making great strides forward on commercial cars. Where the 
springiness of the wheels is not so desirable as strength, the sheet- 
steel plates may be replaced with either pressed- or cast-steel side 
members on which strengthening ribs are formed. The sides of the 
wheel have holes HH through them which are provided for ventila- 
tion, to decrease the weight of the side sheets, and to lessen the wind 
resistance to the wheel when moving rapidly. In some steel wheels 
these holes are omitted; in others a larger number than the four 

shown here are used. Fig. 
499 gives a better idea of 
the general appearance of the 
wheel ready to use, being 
lettered the same as Fig. 498. 
The spokes shown in Fig. 499 
are painted on the smooth 
exterior of the plates, but in 
other wheels these spokes are 
formed in the plates as pre- 
viously mentioned. 

Steel Wheels Designed for 
Cushion Tires. Sheet-steel 
wheels, particularly those of 
very thin sheets, have a cer- 
tain amount of springiness, 
this being utilized with solid 
and cushion tires on the 

Fig. 499. Sheet-Steel Wheel Complete assumption that the wheel 

will absorb the vibrations set up by the road inequalities. In Figs. 
500 and 501, a wheel is shown which was designed for this express 
purpose. The wheel is called an elastic wheel and uses solid tires. 

By means of the figures the construction is made clear, the wheel 
consisting of two halves, one a single sheet of metal attached to the 
hub and forming its own rim portion, and the other a section which 
consists of two sheets, one attached to the hub and forming its own 
rim portion, with another additional plate riveted to it near its outer 


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end and attached to a middle flange on the hub. The two outer 
members of themselves would be very springy and consequently 
very weak, being of very thin metal. The diagonal extra sheet stiffens 
the whole construction, besides adding 50 per cent to its side strength. 
This is also of thin metal, so the whole wheel retains some springiness. 
Parker Pressed-Steel Wheels. One fault with all the steel and 
sheet-steel wheels mentioned was that they did not resemble other 
wheels, consequently the people did not want them. Moreover, in 
many cases, their construction did not adapt them to the 
use of regular tires but, on the contrary, called for special 
and expensive forms. However, none of these drawbacks 
are present in a new form of pressed-steel wheel, Fig. 502. 
Upon close inspection it will be seen that this wheel has 
no felloe in the ordinary sense, the rim of the wheel form- 
ing the only felloe. In this respect, the wheel is an 
outgrowth of the former Healy demountable rim, the 

Fig. 500. Steel 

Fig. 501. Disassembled Steel Wheel 

modern form being a combination of a demountable rim with steel 
spokes. This wheel is suitable for any car, the hollow steel spokes hav- 
ing great sustaining power. It is interchangeable with all ordinary 
wood artillery wheels of the same size, and fits between the usual hub 
flanges. The spoke portion is made as a pair of units, each forming 
half of all the spokes, the two being welded together. When finished 
in this manner, they have half the weight and more than twice the 
strength of the wood wheel, the greatest saving being at the rim, 
by the removal of from 60 to 100 pounds of metal and wood. 

This wheel takes the ordinary demountable rim directly upon 
the ends of the spokes, the one shown being the No. 2; which is suit- 


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able for about twelve different rims as made by the largest manu- 
facturers. The No. 1, whose only difference in appearance is a flat 
spot just under the bolt heads at the ends of the spokes, takes all one- 
piece clincher or straight side rims, whether clincher or Q.D. (quick 
detachable). The wheel shown is a 36- by 4|rinch size, made from 
.083-inch sheet steel, with ten spokes If inches' round ; and a center 
portion, all of the same thickness of steel. 

A number of other pressed-steel wheels, made, like the Parker, 
by pressing out two or more simple units, and welding these together, 

are making their appear- 
ance. These show great 
ingenuity and variety in 
the methods used to pro- 
duce this same result and 
yet avoid the Parker 
patents. This form of 
wheel, having the appear- 
ance of wood, yet with 
greater strength and 
dependability and also of 
lighter weight, may per- 
haps be the final answer 
to the wheel problem; 
certainly this is possible 

Fig. 602. General Appearance of Parker Hydraulic if quantity production 

steel wneel a 

can bring them down 
below the price of wood wheels, which now seems apparent. 


Requisites. On commercial cars the service is so different as 
to call for entirely different wheels. Of course, many commercial- 
car wheels are nothing but pleasure-car wheels with heavier parts 
throughout, but it is coming to be recognized that heavy trucks, 
tractors, and similar vehicles should have their wheels designed for 
the service required of them the same as lighter cars. No springiness 
or resiliency is required for heavy truck service, but simply these 
three things: strength to carry load and 'overloads; strength to 
resist side stresses; and such material, design, and construction as 


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will make for low first cost and low cost of maintenance. A fourth 
desirable quality might be added to these, the quality of being 
adaptable or adapted to the tires to be used. 

Wood Wheels. Taking Fig. 503 as an ordinary heavy vehicle 
wheel, let us see in what ways it fulfills or falls short of these require- 
ments. The spokes are large in both directions and widened out at 
the felloe to give greater side 
strength. The felloe, which 
cannot be seen, may be judged 
as to size from the width and 
location of the dual tires, 
which would indicate great 
width and considerable thick- 
ness. This style of tire calls for 
a steel band shrunk over the 
felloe, while the heads of the 
cross-bolts show how the tires 
were put on and held on. 
All these make for great 
strength in both horizontal 
and vertical directions, and 
all parts except the spokes 
are simple to make, and even 
these are simple for the wheel 
manufacturer whose shop is 
rigged to make them. More- 
over, to fill the last require- ** *?• *"""-«« Wood T ™<* *** 
ment, the wheel is adaptable to this tire or to any one of a number of 
motor-truck tires which might be used. 

A slight variation from this is the double-spoke wheel, in which 
the spokes, in addition to being placed in double rows, are set so 
as to miss each other across the wheel, that is, each spoke of one 
row coming between two of the other. This placing allows the spokes 
to be made larger and stronger than in the ordinary case, while the 
double rows have, the same strengthening effect as the tapering of 
spokes. The hub portion is assembled as two separate wheels, so 
that the work of assembling as well as of making the parts is slightly 
more than with the ordinary wheel. This is more than compensated 


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for by the added strength. It is but fair to state that each of the 
last two wheels described is of English make. 

In all wood wheels, the blocks composing the wheel and tire 
are of well-seasoned rock elm, sawed into wedge-shaped blocks, with 
the fiber lengthwise. The blocks are glued and nailed together 
until they form a circle. They are then turned round and to size 
in a large wood lathe, a shoulder | inch wide being formed at the 
same time on each side of the tire 2.5 inches from the tire surface. 
A heavy steel ring with a corresponding shoulder is then shrunk 

Fig. 504. White Cast-Steel Wheel 

over the wood shoulder on each side of v the tire7 drawing it together 
much like the ordinary steel tire'bn a wood wheel of a carriage. 
Bolts are run through these rings and through the wood blocks from 
side to side to prevent the blocks from splitting sidewise. To increase 
the life of this tire, steel wedges £ inch thick are driven crosswise 
into the face of it 2.5 inches deep around the whole tire about 3 
inches apart. These wedges prevent the tire from slipping; in fact, 
they act like an anti-skid chain and do not harm the pavement, 
being set flush with the surface of the wood blocks. 


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It is said that one set of these tires was used for nine months, 
and at the end of that time they were still good for service. The 
tires reach clear to the hub, thus doing away with spokes and enabling 
the tires to be slipped over the hub and held in place by a removable 
flange bolted through the wood to the fixed flange on the opposite 
side of the hub. 

Cast-Steel Wheels. The heavier the service the more unsuit- 
able do wood wheels become, that is, wood-spoke wheels. For many 
five-ton trucks, practically all seven- and ten-ton trucks, and nearly 
all tractors, the cast-steel wheel is used, either spoked or solid, the 
spoked form being given the preference. Fig. 504 illustrates a spoked 
cast-steel wheel, fitted with a solid tire. The wheel is cast with ten 
heavy ribbed spokes, a ribbed felloe, and a grooved-felloe surface, 
into which the tire is set. 

Miscellaneous Wheel Types. Steel. Steel wheels are gaining 
for heavy truck use, and a number of the better steel-casting firms 
are now getting into this work, with the result that better steel 
wheels are becoming available. 

Other constructions, such as steel and wood combination wheels 
with removable and replaceable spokes, and the like, are rapidly 
going out of existence. Truck work is unusually severe, and it takes 
but a few weeks of actual use to show up any of the so-called freak 
wheels. The simplest seems to be the best, the only question at 
present being whether the material shall be wood or cast steel. 
Pressed steel may offer some opportunities in combination with 
welding, since good work has been done on pleasure-car wheels of 
this type. 


Wheel Pullers. In handling wheels a wheel puller of some form 
is generally a necessity; wheels are removed so seldom that they are 
likely to stick, and they get so much water and road dirt that there 
is good reason for expecting them to stick or to be rusted on. This 
means the application of force to remove the wheel. For this purpose, 
a wheel puller is needed, and a number of these have been illustrated 
and described previously, as gear pullers, steering-wheel pullers, 
etc. Any one of these devices which is large enough to grasp the spokes 
of the wheel and pull the latter outward and, at the same time, press 
firmly against the protruding axle shaft will do the work well. 


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Fig. 607. 

Makeshift Wheel Puller for Road 
Repair Work 

Sometimes, however, while owning a puller, a wheel breaks 
down on the road where this is not available, or the repair man is 
called without being told the trouble, so that he does not bring the 

puller with him. In such cases, 
the repair man must improyise 
some kind of a puller out of what 
he has on hand. Everyone carries 
a jack, so it is safe to assume that 
one of these will be available as 
well as some form of chain. If a 
chain of large size is not available, 
tire chains — particularly extra 
cross-links — may be fastened to- 
gether to answer the purpose. If 
chain is lacking, strong wire, wire 
cable, or, in a pinch, stout rope 
can be substituted. Attach the 
rope, wire, or chain to a pair of 
opposite spokes of the wheel, 
Fig. 507, allowing usually about two feet of slack. Draw the chain 
out as tightly as possible, place the jack with its base against the 
end of the axle and work the head out by means of the lever until it 

comes against the chain. 
Then by continued but 
careful working of the 
jack, the wheel is pulled 
off the axle. 

If rope, wire, or wire 
cable is used, it is advis- 
able to place a heavy 
piece of cloth, burlap, or 
something similar over the 
head of the jack to pre- 
vent its edges cutting 
through this material. 
With rope only enough slack must be used to allow the jack in its 
lowest position to be forced under it; this must be done because there 
is so much stretch to the rope itself and so little movement in 

Fig. 508. Tire Platform or "Dolly" for Handling 
Truck Wheels 


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the ordinary jack, that the combination of rope and jack does not 
always work to advantage. 

Similarly, the handling of heavy truck wheels gives much 
trouble even in the garage, for they are so big, heavy, and 
bulky that ordinarily two men are needed. One man can do 
the trick, however, with a platform or "dolly" like that shown 
in Fig. 508. This consists of a platform about 4 feet long by 
25 inches wide, fitted with casters at the four corners. Inside of the 
central part are placed a pair of wedges, one of which can be moved in 
or out by means of a crank handle. To use this, the wheel is jacked up 
a little over 2 inches, and the truck pushed under. Then the movable 
wedge is forced in against the tire so that the two wedges hold the 
wheel firmly and carry all of its weight. Then the casters are turned 
at right angles so that the platform and the wheel may be moved off 
together. The truck wheel is removed in the usual manner, that is, 
with the aid of the wheel puller or such other means as the garage 
equipment affords. The dolly also forms a convenient means of 
handling the wheel when it is put back on its axle. 

Kinds of Tires. Broadly, there are three general classes of tires: 
the solid, the pneumatic, and the combination or cushion. The solid 
tire needs little comment or discussion here — being solely for com- 
mercial cars — except in so far as it is used with some form of spring 
wheel, hub, or rim, as just described. Similarly, the cushion tire is 
mostly used for electric cars, its use following that of the solid tire. 


The pneumatic tire was originally developed for bicycle use and 
in the beginning many single-tube tires were used. All of the tires 
used today have two parts — an inner and an outer tube. 

Classification. Considering only the double-tube types, there- 
fore, the pneumatic tire may be divided into three kinds: the Dunlop; 
the clincher; and various later forms brought out to go with the detach- 
able demountable rims; and similar devices. These latter vary 
widely in themselves, but all are modifications of the clincher form, 
with minor differences of the difference in rims. 

Dunlop. The D^ilop tire, so named after the Irish physician 
who invented and Constructed the first pneumatic tire, is brought 

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down to meet the rim in two straight portions, perfectly plain and of 
even thickness, that is to say, the tire has no bead, as it is now 
called. The tire fabric is brought down to a straight edge at the rim, 
as well as the rubber covering, as shown in Fig. 509. A is the steel 
rim of the wheel, B the inner tube, C the outer shoe, which at the 
rim or inner portion is brought down to the two straight parts DD. 
This tire, like all of the early tires, had to be put on over the 
edge of the rim by sheer strength, coupled with the flexibility of 
the tire when not inflated. This was a hard task, and, moreover, 
as soon as the tire was punctured or otherwise deflated, there was 
a strong possibility of its being thrown off, and possibly lost, at 
east after it had been stretched on and off the rim a few times. 

Fig. 509. Section of Fig. 510. Section of Typical 

Dunlop Tire Clincher Tire 

Clincher. To prevent this latter happening, the clincher rim 
and tire were brought out, each being dependent upon the other. 
In the clincher tire, the fabric is brought down to the rim, and then, 
instead of being left straight out as in the Dunlop, the material is 
formed into a hump, or bead, which is shaped just like the hollow 
formed in the rim. The latter differs from the usual Dunlop rim 
only in having this deep depression to fit the bead of the tire. Fig. 
510 shows this, in which the parts are lettered as before. In both 
cases, the fabric of the tire is sketched in, and it may be noted that 
the layers are fewer in number in the older form. 

The great majority of tires now in use are of this type, although, 
like the original Dunlop, it must be forced on and off the rim by 
the stretch of the deflated tire, and by sheer strength, coupled in this 
case with considerable natural ingenuity and some tools for lifting 


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the hard non-stretchable beading over the edge of the rim at one 
point. This done, the rest is easy. For this purpose many tools 
have been bought; some good, some bad, and some indifferent. After 
a fashion, all do the work, but that tool is best which performs 
the operation most easily, most quickly, and with the least damage to 
the tire or rim. Fig. 511 shows a useful tool for this purpose. 

The wire wheel and demountable rims, both allow quick road 
changes of damaged tires, leaving the work of tire repair to be done 
at home in the garage with proper heat, light, tools, and materials. 
This is rapidly bringing back into use the lower price clincher and 
straight-side tire forms, also many new tools have made their 
removal or attachment a much easier and more simple task. 

Demountable Rim Types. Following the development of the 
clincher tire and rim until this form of tire was practically universal, 
came the first forms of the 
demountable rims, which 
consisted of a detachable 
edge or rim portion, like the 
edge of the clincher rim in 
section. These were locked 
in place in various ways in 
the different forms, but the 
first demountable rims — they 
were called detachable rims ™* 51L *i« R-novtog Tool 

— were made by cutting the clincher rims into two parts, one of them 
detachable. This allowed of slipping the tire on over the rim in a 
sidewise direction, and did away with the stretching and pulling 
necessary with the plain clincher. Since this was a tire which was 
detachable more quickly than the ordinary tire, it was given the name 
"Quick Detachable", and now both parts are known to the trade as 
the Q.D. tire and rim. 

Non-Skid Treads. All of the later developments in the clincher 
tire have been along the line of studded or formed treads to prevent 
skidding. In this many different things have been tried. Fig. 512 
shows sections of many of the representative tires on the market. 
They are well known, and only the last three need any comment. 

Fig. 512 H shows the Kempshall (English) tire tread, which is 
built up of a series of circular button-shaped depressions, or cups, 




which hold the pavement by means of the suction set up when they 
are firmly rolled down upon it. This tire has been very successful 
in England, but as yet has not been used much in this country. 

The Dayton Airless tire, shown in Fig. 512 /, is a bridge- 
constructed cushion tire in which the usual air space is given over 
to a series of stiffening* radial pieces of solid rubber, these with the 
tread forming the bridge or truss. Fig. 512 J shows the Woodworth 
adjustable tread for converting the usual smooth-tread tires of 
whatever shape or form into non-skids. It is a leather and canvas 

Fig. 512. Various Types of Non-Skid Tire Treads 

built-up structure, shaped like the exterior of a tire, and freely 
studded with steel rivets. When in place, the tire has all of the 
appearance of a leather-tread tire with steel studs. 

Proper Tire Inflation Pressures. With the recent great increase 
in the value of rubber and the price of tires, the advice of manu- 
facturers on the subject of tire wear is of great and growing impor- 
tance. Nearly every manufacturer of tires is now recommending 
a table of inflation pressures which agree among themselves more 
or less closely. In each and every case, however, the makers are 


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advising higher pressures than those generally used, stating that 
the people do not pump their tires up hard enough to get the best 
results from the materials in the tires. There should really be no 
conflict of interests here as the owner should be as anxious to get his 
mileage out of the tires as the makers are to make good their 

Many makers have stated, as a result of their years of experience, 
that more tires wholly or partially fail or wear out from under- 
inflation than from any other one cause. It thus behooves the 
owner of a car to look well to the pressure in his tires, not occasionally 
but very frequently. As the majority of gages attached to pumps 
in public garages are seriously in error, each motorist is advised to 
purchase his own gage — one of the pocket type which is simple and 
inexpensive — and carry it with him at all times. 

In some cases, it will be found that pumping the tires up to the 
makers' specified pressure will result in unusually hard riding, and 
the motorist must be his own judge as to whether he wants to ride 
more comfortably and get less wear out of his tires or to put up with 
the discomfort and get every cent of wear out of them. In this 
matter, very few will choose the latter course. 

Use of Standard Pressure and Oversize Tires. There is really a 
different way out. If the tire pressure advised by the maker results 
in too hard riding for comfort while comfortable pressures result in 
too much wear, the motorist is advised to get large size tires. These 
on the same car will have a greater carrying capacity than the weight 
of the car by a large margin. Just in the proportion of the tire 
capacity to the weight of the car will be the pressure recommended 
to the pressure utilized. 

A simple example will make this clear: Suppose, for instance, 
a car weighing 3850 pounds, equipped with 34- by 4-inch tires, for 
which the makers claim a carrying capacity of 1100 pounds per wheel 
and recommend a pressure of 95 pounds. If this pressure be too high 
for comfort, and lower pressures, say 80 or 85 pounds, result in too 
rapid wear, the motorist should use larger tires. For instance, a 
34- by 4|-inch tire is scheduled to carry 1300 pounds per tire, and the 
pressure recommended is 100 pounds. The car weight per tire is 
962 pounds, say 970. Changing to the larger tire gives a capacity 
of 1300 pounds per wheel, while the load is actually but 970. This 



change provides a surplus capacity which can be utilized to increase 

Hence, if the tire be pumped up in the ratio of the carrying 
capacity of the tires to the actual weight carried, the spirit of the 
manufacturers' instructions will have been followed, comfort assured, 
and long life of the tire attained as well. Here the ratio of the 
capacity to the weight is as 1300 : 970. If now the pressure be figured 
from this, using the 100 pounds recommended, a suitable pressure 
will be obtained. Thus 

1300 : 970 : : 100 : x 
x =74.6 pounds 
The pressure, therefore, in round numbers will be 75 pounds, and 
if this or any comfortable pressure above this be used, only the 
proper amount of tire wear will result, and a comfortable riding car 
will be assured. 

However, this proposition, namely, changing from 34- by 4-inch 
to 34- by 4^-inch tires, is one which calls for entirely new rims, and 
possibly entirely new wheels, or at least new felloes, because the bottom 
diameter of the 34- by 4^-inch is different from that of the 34- by 
4-inch. In such a case as this, the motorist would gain by changing 
to a still larger size, say 35- by 4|-inch, which change can be made 
without disturbing the old rims, as the 35- by 4|-inch is an oversize 
for 34- by 4-inch. This size also is recommended to carry 1300 
pounds at 100 pounds pressure per square inch, but maximum pleasure 
and comfort will be obtained from it at between 72 and 80 pounds. 

In general, the rule for oversize tires is this: Oversize tires are 
1 inch larger in exterior diameter and % inch greater in cross-section 
than the regular sizes, and any tire so sized will fit interchangeably 
with the regular size on the same rim. 

Recent Tire Improvements. There have been but three recent 
notable improvements in tires which are briefly discussed. 

Tire Valves. There have been several kinds of troubles with 
the old form of tire valve. It was spring actuated, and the springs 
were so small as to cause much trouble; further, it had to be screwed 
in place, requiring a special tool. There are several new valve 
forms with more than one seat, and others with an improved seat 
designed to screw in with the fingers and to offer little or no 
resistance to inflation. 




Inner Tubes. Improvement has been made in inner tubes 
by the use of better and purer rubber in much thicker sections. 
Some of these have a partial fabric reinforcement; others are made 
and then turned inside out so that the tread portion is under com- 
pression, thus resisting punctures or internal pressure. Other 
designs present a tube larger than the inside of the tire before infla- 
tion; this produces a truss formation of the rubber, which the air 
pressure stiffens. 

Cord Tires. The real improvement of value, however, is the 
cord tire. One form of this is shown in partial section in Fig. 513. 
This shows graphically that the difference between this tire and 

Fig. 513. Section of Goodrich Silvertown Cord Tire, Showing Inner Construction 

other forms is that the 4 to 6 or more layers of fabric have been 
replaced by two layers of diagonally woven cord. This cord is 
continuous, rubber impregnated, rubber covered, and, through its 
size, allows a great and very even tension. Lessening the amount 
and thickness of the fabric has given a greater percentage of rubber 
in the tire; consequently, the cord tire is more resilient. The advan- 
tages claimed for it are: less power used in tire friction, which means 
more power available for speed and hill climbing; greater carrying 
capacity in same size; saving of fuel; greater mileage per gallon of 
fuel; additional speed; quicker starting; easier steering, thus less 
driving fatigue; greater coasting ability; increased strength; and 
practical immunity from stone bruises owing to superior resiliency. 




Kinds of Rims. Nearly all rims are of steel or iron, but vary 
greatly as to types. The writer has therefore chosen only a few 
of the well-known ones, no preference being shown in this. 

Rims will be taken up in the order of their development. Natu- 
rally, the first rims were of the plain type, while the latest are of the 
demountable, remountable, or removable types, all these being very 
much the same. Between the two came the clincher rim, which is 
properly a plain rim; and the quick-detachable rim. 

Plain Rims. The form of rim first used was naturally the solid 
type, shown with the Dunlop tire in Fig. 509. This form is a simple 
endless band with two edges just high enough to prevent the tire 
from coming off sidewise when it has once been stretched in place. 
Nothing like it is used today, the nearest approach being the form 
of rim used with single-tubfe bicycle tires. 

Clincher Rims. Clincher rims were brought out primarily to 
avoid the weaknesses of the Dunlop, viz, a weakness at the base, 
and, hence, it had an unusually heavy bead. Another fault which 
this tire remedied was the tendency under high pressure for the tire 
to draw away from the rim. This was avoided by the edge of the 
clincher being made fairly wide where it was designed to go into 
the pocket, or groove, formed by the contour of the rim. 

It is the depth of this pocket, or groove, and the corresponding 
size of the edge of the bead on the tire, both excellent qualities, which 
make the tire hard to put on and take off. This may be seen from 
the previous illustrations of clincher tires, notably Fig. 510. 

Quick-Detachable Tire Rims. It was this inherent difficulty 
of handling the clincher tire and rim which brought about the quick- 
detachable tire. This did not differ from the clincher tire in the 
tire portion, the difference being in the rim, which has one curved 
portion made in removable form, with a locking ring outside of it or 
made integral with it. In some quick detachables, the rim is expanded 
by a special tool and a spacing piece set into place, which holds the 
edge expanded. When this is done, the ring — as it is a simple ring 
with special ends — is held in place until released by the use of the 
special tool. On the end of the ring there are two little square lugs . 
which project downward and have a hook shape. The one edge of 
the rim, made flat and straight on that side, has a slot with stag- 


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gered, rectangular ends into which these lugs fit. It requires force 
to spring the rings together so the lugs will go into the slots, but once 
in place, the natural springiness of the rings holds them firmly in 
place, and holds the tire as well. 

Figs. 514, 515, and 516 are given to show how this ring is put 
in place on a tire. Fig. 514 shows the beginning of the operation, 
and the instructions for the different steps will make them clear. 

Always start with left end of the ring. Lock this in the rim as shown in 
Fig. 514, so that the end of the ring is flush with the slot provided for the second 
end. A dowel pin is provided to register the ring in the proper place. This must 
always be correctly centered or the ring cannot be applied. This done, the balance 
of the ring can be forced over the flange of the rim, as shown in Fig. 515, with the 
exception of the locking end. By means of the tool, the last locking end can be 

Fig. 514. Putting on a Q.D. Ring. Fig. 515. Putting on a Q.D. Ring. 

The Start Forcing Flange over Kim 

raised and forced over the rim into the recess provided for holding the same in posi- 
tion preparatory to drawing the ends together, Fig. 516, showing the correct 
position of the tool. 

Then by entering the two points of the tool in the holes provided in the 
ring, the ends may be drawn together, as shown in Fig. 516,*and, with a slight 
additional leverage, the ends of the rings can be made flush. 

Before proceeding further, it should be stated that the object of 
the quick-detachable rim is the quick removal of the tire, in order 
to allow a quick repair or substitution of the inner tube. On the 
other hand, the object of the demountable, remountable, removable, 
and other rims is the removal ^th the tire of the rim itself to allow 



the substitution of a new tire and rim, the tire being already inflated 
and ready for use as soon as applied. The object of the removable 

wheel is the removal of the entire 
wheel with rim and tire in order to 
substitute a spare wheel with already 
inflated tire. 

It might be thought that these 
methods called for the carrying of extra 
weight, but the amount added is 
actually very small, as, by their use, 
tire tools and pump are dispensed with 
and their weight saved. 

Fig. 517 shows the former Good- 
year rim. This rim, as will be noted, is of the quick-detachable type, 
the idea being to remove the tire only. The rim itself has a button- 
hook shape with a slight ridge, or projection, answering to the handle. 
This is on the fixed side, the inner flange inside of the tire butting 
against it as a stop. The tire is pushed over against this, being held 

on the outside by a second 
flange of similar shape. The 
latter, in turn, is fixed in 
place by a locking ring, a 
simple split circular ring of 
deep oval section. This fits 
into the button-hook portion, 
its contour being such as to 
fit it exactly. In use, it is 
sprung into place, the outer 
edge of the hook on the rim 
and the natural spring of the 
ring preventing it from com- 
ing out. This makes a very 
simple and serviceable quick- 
detachable rim. To make 
doubly certain that the lock- 
Fig. 517. Former Goodyear Universal Rim j ng r j ng cannot j um ^ ou t, a 

spreader plate is attached to the valve stem; screwing this down 
into place wedges the bead of the tire over against the outer flange, 

294 Digitized by 




which, in turn, pushes the locking ring tight against the outer 

curved part of the hooked rim. When in this locked position, 

the upper part of the flange 

hangs over the locking ring, 

so that it cannot rise vertically, 

the only manner in which it 

could come off. This rim is 

shown with a detachable tire in 

position, but may be used with any standard clincher tire by the use 

of extra clincher flanges. Fig. 518 shows the rim with a set of these 

flanges in position, ready to take a standard clincher tire. 

Fig. 518. Adapting Goodyear Rim to 
Clincher Tires 

Fig. 519. Universal Q.D. Rim No. 2 Arranged for Clincher and Dunlop Tires 

Quick-Detachable Number 2. Figs. 519 and 520 show the 
standard quick-detachable rim, now known as No. 2. This was 
adopted by the Association of Licensed Automobile Manufacturers 

Fig. 520. Universal Q.D. Rim with Tires in Place 

as a standard and given the above name. It has the feature of 
accommodating all regular clincher, or Dunlop tires. In Fig. 519, it 
is shown at A ready for a clincher tire and at B ready for a Dunlop 
tire, the adaptation for the straight sides being shown. 

The two parts of Fig. 520 show sections of tires in place, making 
clear the exact use of this reversible flange. A shows a regular 
clincher tire in place, while B reveals the reversed flange in place with 
a Dunlop tire. Both Figs. 519 and 520 show the construction of 


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the device, the outer dropped portion of the rim having a hole through 
it. The locking ring is split vertically and one end, just at the split, 

carries a projection or dowel pin 
extending downward. To put the 
rim on, this dowel pin must be 
fitted into the hole in the rim to 
give a starting place. When this 
has been done, one may force the 
balance of the ring into place 
around the wheel with any suit- 
able, thin, wedge-shaped tool. 

The shape of this locking 
ring with a right-angled groove in 
its inner edge permits the outer 
flange to overlap it, which insures 
the retention of the ring when 
once it has been put in place. Furthermore, it gives the outer side 
flange a wider seat on the rim, thus making it more stable and longer 

As will be noted, the difference between these two rims — that is, 
the old Goodyear and the Universal No. 2 — lies in the saving of one 
ring and the shape of the locking ring. Both of these are called 
universal rims because they may be used interchangeably for straight- 

Fig. 521. Sections through Three Popular 
Q.D. Universal Rims 

Fig. 522. 

Latch Used for Locking Single Combination Ring which Replaces 
Former Side Ring and Locking Ring 

side and clincher types of tire. Other Q. D. Universals are shown in 
Fig. 521, although, in the opinion of tire men, the Universal form is 
slowly going out of use. 

To explain these briefly, No. 1 is a modification of the Goodyear, 
with different shaped inner rings, while the locking ring and the lip 
formed in the felloe band to receive it are similar to those of Univer- 
sal No. 2. . In 2 the only difference from 1 lies in the locking ring, 


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which has a modified Z-section, with a lip extending over the outer 
edge of the felloe band. The third section differs from the other two 
only in having the outer ring and locking ring combined into one, and 
the felloe band changed to suit this. This combination ring is held in 
place by means of a simple, swinging latch, which is shown open and 
closed in Fig. 522. When opened, this permits raising the end of the 
ring, to which the shape of the felloe band offers no resistance. The 
whole inner ring is taken off, following around the circumference of 
the wheel, after which the tire is easily removed. 

Quifik-Detachable Clincher Forms. To return to the plain 
clincher tire and the Q. D. rim, which allows of its ready removal, 

WMMM/M //M/////A 

Fig. 523. Popular Forms of Q.D. Clincher 
Rims, Shown in Sections 



Fig. 524. Three of the Most Widely Used 
Straight Side Q.D. Rims 

Fig. 523 shows four of the most prominent forms, these being indi- 
cated simply as flat sections of the rim, for the tire is the same in 
all cases. All these have the simple clincher edge on one side, with 
removable ring and locking device on the other. That at 1 has the 
same locking device shown at 2 in Fig. 521, the Z-shaped ring extend- 
ing over the edge of the band. That at 2 is practically the same as 
8 in Fig. 521. The one seen at S is similar to that at 2 except for the 
detailed shape of the ring as well as the lock (not shown). The 
advantage of the form shown at 4 is that the outer ring is self-locking, 
that is, the shape of ring and band are such that when the former 


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is in place the tire itself locks it. Its only disadvantage is that 
it is harder to operate than the other forms, yet despite this fact it 
has been recommended for general adoption as the only Q.D. clincher 
rim worth continuing. 

Q.D. Type for Straight Sides. To close the subject of straight 
side tires, the rims of the quick-detachable form now in use aside 
from those already shown are seen in Fig. 524. Here these are seen 
to be identical with 1, 2, and 4 of Fig. 523, except that the fixed 
side is arranged for a straight side instead of being made with a clinch. 
Here again, the last form of self-locking type has been recommended 
as a standard. 

Demountable Rims. All, or practically all, demountable rims 
come under one of two headings — those in which the tire can be 
detached on the wheel without demounting (if it is so desired) and 


Fig. 525. Sections of Michelin and Empire Demountable Rims 

those which are of the transversely split type and must be demounted 
before the tire can be removed. In addition, there is a second division 
of demountable rims into those which have a local-wedge form of 
attachment and those which have a continuous holding ring, this, in 
turn, being held by means of local wedges. Any of the plain demount- 
ables, which will be called demountables from now on, may be of 
either type of attachment, as is also the case with the first-named or 
demountable detachables. 

Local Wedge Type. In the so-called local wedge type, which 
includes the well-known Continental forms (notably Standard 
Universal Demountable No. 3 and Stanweld No. 22 and No. 30), 
Michelin, Empire, Baker, Detroit, Prudden, Standard Universal 
Demountables No. 1 (formerly the Marsh), and No. 2, and others, 
loosening the six (or eight, as the case may be) bolts frees the rim 
directly without further work. In some of these, such as the Michelin •, 
the various Continentals, including Stanweld No. 22 and No. 30; 


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Detroit; Baker; and others, the wedges carry a projecting lip, which 
makes it necessary to unscrew the nuts far enough to allow the 
removal of the wedge so as to 
pick this lip out from under 
the tire-carrying rim. In 
others, such as Empire, S.U. 
No. 1 and No. 2, the con- 
struction of the wedge and 
rim is such that loosening 
them frees the rim, the upper 
part of the wedge or clip 
swinging down to the bottom 
position as soon as loosened, 
because of its heavier weight 
and the fact that there is no 
projecting edge to prevent it. 
While this latter construction 
makes a faster operating rim, 
it is an open question as to 
whether it is as safe as the 
other form. These two con- 
structions are shown very 
plainly in Fig. 525, in which 
A is the Michelin with lipped 
wedges, and B the Empire 
with plain wedges. 

In Fig. 526 is shown a 
pair of additional demount- 
ables, which are held by 
the local wedge method, the 
difference here being in the 
form of a wedge. Note that 1 
has a solid clincher rim and 
2 a straight side rim. The 
base, however, is the same 
for both and, as will be seen ^ 527 se Ctional Drawing showing con- 

by examining this, has tWO struction of Baker Demountable Rim 

curves in its upper surface, the straight side rim fitting into the lower 

Fig. 526. Two Popular Demountable Rim Forms 
— for Clincher Tires above, for Straight Side below 


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or bottom one, while the clincher form of rim fits into the upper one. 

Note, also, that the wedges are the same for these two. This makes 

the demountable parts 
of the rim practically 
universal in that the 
owner can change from 
clincher to straight side 
or vice versa by simply 
purchasing the extra set 
of tire-carrying rims, 
no change in the wheels 
or means of attachment 
being necessary. For 
this reason, the felloe 
band shown under these 
two rims has been sug- 

Ffg. 528. The lint Operation in Removing Baker 8 eSted ftS a Standard for 

Demountable-Loosening the Bolts demOUntableS. 

Process of Changing Baker Local Wedge Type. In Fig. 527 is 
shown the Baker, which, as mentioned previously, is of the local 

wedge type of demount- 
able, having a trans- 
versely split rim which 
must be removed from 
the wheel before the tire 
can be taken off. Per- 
haps this whole action 
will be shown more 
clearly by the progres- 
sive series of views, Figs. 
528 to 538, which show 
the various steps in re- 
moving and replacing a 
tire and tube mounted on 
, „ , ^ . ^ a Baker rim, the same as 

Fig. 529. Second Baker Demounting Operation — # ... 

Jacking the Wheel and Starting to Pry off Rim jg shown in Section 111 

Fig. 526. First, all the wedge bolts except the two nearest the valve 
stem, one on either side, are loosened by means of the special brace 


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until the wedges swing out and down, as shown in Fig. 528. As 

mentioned previously, this means quite a little loosening, for the 

wedges have a long lip 

which projects under the 

tire-carrying rim. When 

this has been done, and 

as each one swings down 

out of the way, it is 

tightened just enough to 

prevent the wedges from 

swinging back. 

This done, the wheel 
is jacked up off the 
ground, as shown in Fig. 

529, and the point of the 
tire tool is inserted be- 
tween the felloe band _. 

. . Fig. 630. Third Baker Operation— Putting on New Tire 

and the run carrying the a™ 1 Lowering wheel 

tire at the point opposite the valve, where, it will be remembered, the 
wedges were loosened, and the rim will be almost free. By prying 
the tire-carrying rim out- 
ward and working around 
it toward the valve and 
back again, it will finally 
be loosened to a point 
where, with the valve at 
the bottom, the rim and 
tire can be slipped off 
without lifting it. The 
extra tire and rim are 
now put in place. 

This is shown in Fig. 

530, where the reverse of 
the operations shown in 

Fig. 529 and just de- ^ ML Fourth Operation— Tightening Bolts on 

scribed is followed, that *« New Tire and Rim 

is, the valve stem hole is revolved to the top, the valve stem inserted, 

the rim pressed into place all around, then the wheel is revolved until 


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Fig. 532 Fifth Operation — Starting to Take Fig. 533. Sixth Operation — Forcing Down the 

the Rim out of the Tire — Beginning Short End of Rim 

to Pry Short End 

Fig. 534. Seventh Operation — Prying under Fig. 535. Eighth Operation — Raising the Free 

the Loose End of Rim End of Rim, Using Both Hands 

Fig. 536. Ninth Operation — Inserting Fig. 537. Tenth Operation — Prying Tire 

Valve Stem and Beads in Away from Rim to Let Latter 

End of Rim Slip into Place 


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the valve stem comes to the bottom, so that the two wedges 
which have not been loosened are nearest the ground. Then the jack 
is let down and removed, the whole weight of the wheel coming on 
the bottom point where the wedges are already tight, never having 
been loosened. 

This action is necessary as, with the weight on the other points 
where wedges are still loose, it would be necessary to work against 
the car weight. At this point, as Fig. 531 shows, the nuts are loosened, 
using the special brace until the wedges can be inserted under the 
rim. This done, the nuts are tightened to hold them there. This 
tightening is continued until the little studs, or lips, in the rim rest 
on top of the outside edge of the felloe band, using the tire tool to 
force them in, if necessary. The new tire carried is supposed to be 
ready for use, that is, inflated to the proper pressure, so that these 
four actions complete the work of making a roadside change. 

When it is desired to repair the tire which has been removed, 
it is carried home on its rim just as taken off the car wheel, and the 
rim is removed from the casing as follows: Rim and tire are laid 
flat on the garage floor, as shown in Fig: 532, so that the outer end 
of the diagonal cut in the inside of the rim which is farthest from the 
valve stem is uppermost. An inside plate will be found on the rim 
which covers the two rivet heads on either side of the cut, with a 
central hole for the valve stem. This plate is called the anchor plate 
and must be removed. To do this, begin at the short end of the rim, 
which does not have the valve stem — as, in this position, it will be 
held in the long end — and insert the sharp end of the tire tool or a 
screwdriver under the bead or between the bead and the rim. 

These two actions, as shown in Fig. 533, bring the two short 
sides of the rim closer together and thus reduce the diameter. When 
the extreme end has been freed in this way, the operation is repeated 
some 5 or 6 inches farther around, that is, that much farther away 
from the slit. This done, a considerable portion of one end will be 
free. Then turn the rim and tire over so thatvthis free part comes at 
the top instead of at the bottom and, standing on the part whieh is 
still tight, insert the tool between the rim and the entire tire. 

This frees the entire end, but, to make sure, the tool must be 
moved a little farther along so as to free more of it. When enough has 
been freed to allow grasping it with both hands, as shown in Fig. 535, 


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the tool is dispensed with and, taking a firm grip on the rim, at the 
same time standing on the tire at the point where tire and rim still 
contact, pull upward strongly. When followed all the way around 
this pulls the rim entirely out of the tire; 

Having the casing and tube free, they may now be inspected and 
repaired. When this is done, or if it is not done, and a new tire or tube 
or both are used, the worker is ready now to replace the rim. This is 
practically the reverse of the method just followed out. As shown in 
Fig. 536, the rim is laid on the floor; then the end which has the valve- 
stem hole drilled in it is raised, and the valve stem inserted. Next 
the beads are pulled into the rim, it being necessary to press them 
together somewhat tightly in order to do this, but, with a little prac- 
tice, it soon becomes an easy matter. All this is done with the other 
part of the rim underneath the tire. 

The inserted end of the rim is followed around with the thin 
end of the tire tool, as shown in Fig. 537, the position of the tire 

above the rim allowing the work- 
man to stand on it and thus use 
his weight to press the two sides 
of the tire together and, at the 
same time, to force them into the 
rim. This operation is followed 
right around the inside circum- 
ference of the tire, the free, or 

Fig. 538. Eleventh Operation-Inserting short > en <* of the rim being the 

Anchor mat. last part to enter. On account of 

the shape of the joint or cut in it, this should slip readily into its 
proper place, but if it does not, the thin end of the tool can be used to 
pry it into place, or a hammer can be used on the longer side to 
drive it in. 

The rim being fitted snugly into place all around, the anchor 
plate is inserted, Fig. 538, to prevent the short end slipping out again, 
and the tire is ready for inflation. If it is to be carried as a spare 
tire, the dust cap should be screwed into place over the valve stem, 
so as to preserve the threads which might be damaged in handling. 

Rim with Straight Split. This covers the action of practically all 
the demountables in which the transversely split rim is used, necessi- 
tating the removal of the rim and tire from the wheel before the 





Fig. 539. One-Piece Rim, Showing Right-Angled 

Split and Locking Device 

Courtesy of Standard Welding Company t Cleveland, Ohio 

tire can be taken off the rim. However, not all rims are split on a 
diagonal as is this one, and Fig. 539 is presented to show this single 
feature on another rim, which otherwise is somewhat similar. Here 
the rim is split at right 
angles, having a plain thin 
rectangular plate A attached 
to the free end, or that which 
is removed first, while the 
other end has a swinging flat 
tapered plate with a cam- 
shaped end B, the action of 
which is to expand the rim 
to its fullest diameter and 
lock it there. In the top 
figure, it is locked — that is, 
the rim is expanded as it 
would be when in use and just 
after it had been removed for 
replacement. When the rim 
is to be removed from the 
tire, the latch B is swung out 
of the way, as shown in the 
lower figure, when the catch 
C which holds the two ends 
together can be opened by 
lifting the tire with this 
portion at the bottom and 
then dropping it a couple of 
times. ' This done — usually 
this action will be accom- 
panied by the free end spring 
inside the fixed end — con- 
tinuation of the removal is an 
easy matter. The rim shown 

Comparison of Continuous Holding Ring Type with Local Wedge 
Type. To return to demountable-detachable rims, these may and do 
include a number of those quick-detachable forms previously shown 

Kg. 640, 

Sections through Two Popular Forms 
' " i Kims 

of Demountable-Detachable J 


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and described. In Fig. 540, a pair of typical forms is shown, that at 
1 being fitted for a clincher tire, while that at 2 is for a straight side. 
Looking at the detachable part of the rim, 1 will be recognized as 
that previously shown at 3, Fig. 521, where it was described as a 
universal rim, the inversion of the two rings converting it from a 
clincher to a straight side, or vice versa. Similarly, 2 will be recog- 
nized as the form of detachable shown at 3 in Fig. 524. 

Here, however, both are fitted to be used as demountables, 
this being accomplished by the formation on the under side of the 
band of a pair of wedge-shaped projections. The felloe band is so 
made and applied that it forms one surface to contact with one of 
these wedges, while the other is formed variously. At 1, a separate 
ring is used with the flat outside clips to hold this against both 

felloe band and rim, while at 
2 the wedges or clips have 
an extension which presses 
against the outer wedge on 
the rim. This latter distinc- 
tion divides these two into 
the two classes mentioned 
previously — one into the 
continuous holding ring class, 
the other into the local 
wedge type. 

These forms are shown 
to illustrate this point and 
also because, despite this 
difference, they have practically similar felloe bands. This felloe 
band — that is, of the form shown in 2 — has been recommended as a 
standard for all demountable-detachable rims. Another and different 
example of the clamping-ring demountable-detachable type is shown 
in Fig. 541, this being the Firestone rim. Here, it will be noted, is 
the felloe band just mentioned, while the detachable-rim portion is 
that previously shown at 1 in Fig. 523 as having the Z-shaped locking 
ring and being adapted to clincher tires only. The rim band is 
made with the two wedge-shaped projections on its underside. 

Perlman Rim Patents. Late in the summer of 1915, considerable 
consternation was caused among tire and rim manufacturers when 

fi/M BOLT- 






Fig. 541. 

Section of Tire and Rim of Firestone 
Demountable Tire 


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it became known that the Perlman rim patent had been adjudged 
basic by the courts, and that, on the strength of this decision, an 
injunction had been issued against the Standard Welding Company, 
of Cleveland, Ohio, some few of whose rims have been previously 
described. Perlman's original patent was applied for on June 29, 
1906, and, in addition to this record, the fact was established that 
the owner had a Welch car which had traveled over 150,000 miles 
and on which were a set of the original rims. The case dragged 
through the courts and was discontinued some seven or eight years 
ago. Perlman persisted, however, although he had to revise and 
alter his application many times; the basic patents were finally 
allowed, and issued to him in February, 1913. This means, of course, 
that the patent will not expire until 
the year 1930. 

Perlman's locking elements and 
the principle involved are shown in 
Fig. 542, which is a section through 
the rim and felloe. In Perlman's suit, 
it was claimed that the wedge end of 
the bolt which was covered in his 
patent, included all wedge-operating 
rims, whether actuated from the 
center, as in Fig. 542, or from the side. 
This contention was supported by the 
court, and negotiations are now in process between Perlman and many 
manufacturers of the so-called local wedge type of rim. As this would 
appear to cover all the rims shown and described in Figs. 525 to 541, 
inclusive, the influence of this decision upon the industry can be 
-imagined. Moreover, the length of time which this basic patent has 
to run precludes the possibility of delaying action by prolongation 
of suits, as has been done in similar cases. A notable example of 
this is the case of the Selden automobile patents, which were fought 
on one ground or another over a long period of years. 

Standard Sizes of Tires and Rims. As might have been noted 
in going over the above discussion of tires, plain rims, detachable 
rims, and, finally, demountable rims, all these different constructions 
require widely differing wheel sizes. It has been proposed to stand- 
ardize wheels, that is, the outside diameter of the felloe and with 

Fig. 542. Section of Perlman Rim, 
Showing Locking Device 


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it the thickness of felloe bands as well as their shapes or contours, 
one for each tire cross-section. The proposed reduction of tire sizes 
to nine standards is as follows: 30- by 3-inch, 30- by 3^-inch, 32- by 
3^-inch, 32- by 4-inch, 34- by 4^-inch, 36- by 4§-inch, 38- by 5§-inch 
and probably 36- by 5-inch, supplying these sizes and these only to 
manufacturers of cars; additional oversizes are allowed for car users, 
one for each size above, that is, 31- by 3J-inch for 30- by 3-inch, 31- 

Tire Seat Line 

E Sections'! 

felloes for*3+30 

felloes for 

felloes for 

felloes for 

felloes for 

/Til One Piece 





Split Rims 



Fig. 543. 

G Sections 3i "#6 " 
Typical Felloe, Band, and Rim Sections for Popular Demountable Rims 

by 4-inch for 30- by 3§-inch, 33- by 4-inch for 32- by 3J-mch, 33- by 
4§-inch for 32- by 4-inch, 35- by 4^-inch for 34- by 4-inch, 35- by 5- 
inch for 34- by 4§-inch, 37- by 5-inch for 36- by 4§-inch, 39- by 6-inch 
for 38- by 5|-inch and probably 37- by 5|-inch for the 36- by 5-inch. 
Rim standardization will follow the adoption of these sizes. In this 
event, the standardization of demountable rims will come in time. 
At the present, there is a wide range of difference, as will be 
noted in the drawing, Fig. 543, which shows felloes for the most 


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Fig. 544. Operating Device on the Ashley- 
Moyer Double Q.D. Rim for Wire Wheels 

widely used demountable rims, depicting the band and rim in each 

case. The drawing should be read crosswise, each horizontal line 

showing the differences to be 

found in the makes mentioned in 

that particular tire cross-section 

size. Thus, the D sections show 

the differences for 3J-inch tires, 

E those for 4-inch tires, F those 

for 4|- and 5-inch tires, and G 

those for 5?- and 6-inch tires, 

rims for which are not produced 

by all makers. 

Other Removable Forms. 
Outside of the regular range of 
wood wheels and the standard 
tires for them, any different wheel 
calls for a different treatment. 
As has already been mentioned 
under the subject of Wire Wheels, 
few of these have anything but a 
solid one-piece clincher rim; first, 
because the wheel itself is remov- 
able, thus making it as easy to 
change wheels as to change rims 
in the ordinary case; and second, 
to save weight and complication. 

Demountablefor Wire Wheels. 
However, demountable forms 
have been produced for wire 
wheels, one being shown in Figs. 
544 and 545. This is the G-R-C 
double Q.D. rim as the makers 
prefer to call it, in action a de- 
mountable-detachable form, the 
clincher rim being of the straight 
split type, in fact, a Stanweld 
No. 20. This is made with a 
double wedging surface on. the 

Fig. 545. Section through Rim and Band of 

G-R-C Rim, Showing Wedging 

Band and Its Operation 


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outside and a single one on the inside. The latter contacts with 
another on the false rim to which the wire spokes are attached, as does 
also the inner wedging surface on the outer wedge. The outer wedg- 
ing surface is made so as to come just above a fairly deep slot in the 
false rim. In this is placed a ring with a double wedge-shaped upper 
edge and a square lower edge. This ring is split at one point and 
locked in the highest position at the point diametrically opposite. 

At the split point, a pair of bent-arm levers, Fig. 544, are 
connected to the two ends. Attached to a middle point of each of 

these is one end of an inverted U- 
shaped member, the center and 
upper part of which form a bear- 
ing for a locking stud, which is 
attached to one end of the ring. 
Above this is placed a nut. As 
will be noted, this forms a toggle 
motion, the action of which is 
to expand the whole ring when 
the nut is screwed down and to 
contract it when the nut is 
screwed up. 

This is the precise action 
used, the single ring forming the 
whole locking means, and being 

Fig. 546. Construction of Parker Hydraulic actuated by the toggle mech- 

^^MlS^^^ 01 anism through the medium of 

screwing the nut up or down. 
While at its best on wire wheels because of its simplicity, this rim 
is, of course, applicable to wood wheels. At present, its makers 
are specializing on the wire-wheel forms. 

Parker Rim-Locking Device. Another rim-locking device which 
does not come under any of the standard divisions, being devised 
for use on the Parker hydraulic wheel, previously shown in Fig. 
502, is the Parker modification of the former Healy rim. As shown 
in Fig. 546, which shows the end of a steel spoke in section, this is 
made with a cup at the upper and inner end, while at the outer is 
a loose clip, through which passes a bolt with a head on the outside. 
Tightening the bolt by means of the external head draws the clip 



up the incline at the bottom of the cup, against the wedge on the 
underside of the rim, the amount of pressure exerted depending 
solely upon that applied to the bolt head. As the two wedge shapes 
oppose each other, this holds the rim as firmly as is possible. It 
will be noted that this construction does away altogether with the 
use of felloe bands or false rims used on other forms of rims or wheels, 
thus saving much weight. Moreover, a great part of the weight 
is saved at the outside, where the flywheel effect of rapid rotation 
is thus lessened. Moreover, the absence of additional metal here 
would give the tire more chance to radiate its heat, and thus would 
preserve it better. This construction, considering its many advan- 
tages, should have a wide use. 

Similarly, with all demountable rims, the tendency is toward 
wider use, with which comes lower cost, as well as a better under- 
standing of their use, abuse, attachment, and detachment. With 
the standardization of tires to a few standard sizes, say 9 instead 
of 54, it will be only a few years before all kinds of rims, including 
demountables, will be standardized, at which time the latter will 
come into universal use. 


Composition and Manufacture. Tires consist of two parts, the 
tube and the shoe, or casing. The former is a plain ring of circular 
cross-section, made of pure rubber, containing an air valve, and is 
intended only to hold the air. The shoe, or casing, on the other 
hand, provides the wearing surface, protects the air container within 
from all road and other injuries, and constitutes or incorporates the 
method of fastening itself to the wheel. In its construction are 
included fabric — preferably cotton — some pure rubber, and much 
rubber composition, the whole being baked into a complete unit by heat 
in the presence of sulphur, which acts somewhat as a flux for rubber. 

Considering a typical tire, there enters into its make-up, starting 
from the inside, six or seven strips of frictional fabric, that is, thin 
sheets of pure gum rubber rolled into intimate contact with each 
side of the cotton, making it really a rubber-coated material. Next, 
there is the so-called padding, which is more or less pure rubber, has 
a maximum thickness at the center of the tread, and tapers off to 
nothing at the sides, but usually carrying down to the beading. 


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Above this tnere is placed a breaker strip, consisting of two or three 
layers of frictioned fabric impregnated in a rubber composition. 
This, too, is thickest at the center and tapers off to the sides, but 
ends at the edge of the tread. Finally, there is the surface covering, 
called by rubber men the tread; this contains very little pure rubber, 
being thickest at the center and extending with gradually decreased 

thickness almost down to the 

The last two of this series of 
layers constitute the real wearing 
surface of the tire, and when the 
surface is so worn that the breaker 
strip may be seen, it is time to 
have the tire retreaded. When 
the wear has gone through this, 
if the padding be fairly complete, 
retreading will still save the tire, 
but if wear has gone clear down 
through that so as to expose the 
fabric, the show must be run to a 
finish and then discarded. 

All this construction can be 
noted in Fig. 547, which shows a 
section through a tire, with the 
inner tube in place, the section 
being taken so as to pass through 
the center of the tire valve. This 
should be borne in mind when 
examining this figure, for the 
location of the inner tube inside 
the tire, as previously described, 
is likely to be misleading. 

Bead. In the reference to 
tire construction, no mention has been made of the bead. This is a 
highly important part of the tire, for it is the part which holds 
it in place on the wheel. It is made of a fairly hard rubber 
composition, the fabric being carried down on the sides so as to cover 
it. In a cross-section, it has a shape very close to an equilateral 


Volve Inside 


Fig. 647. Section through Assembled Tire and 

Tube, Showing Construction and Parts 

of the Tire and Tire Valve 


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triangle resting on its base; around the wheel it is curved to fit the rim. 
The method of attaching the tire has a considerable influence on bead 
construction, since, in the clincher type of tire, in which the shoe must 
be stretched on over the rim, the bead must be extensible in order to 
insure easy mounting. In the quick-detachable and straight-side 
forms of tire there is no need for this stretching, so the bead can be 
made of stiff and rigid material as well as cut down somewhat in size. 

The straight-side or Dunlop type of tire is seldom made with 
much of any bead, the layers of fabric being carried straight down. 
A more modern form of tire has a 
pair of woven-wire cables incor- 
porated in the bead to make it 
stiffer and stronger, and this is 
said to have been very successful. 
As has been pointed out pre- 
viously, this could be done only 
with the quick-detachable form, 
not with the clincher type. 

In both the clincher and the 
quick-detachable forms, the bead 
holds the tire to the wheel by 
means of parts of the rim, which 
bear on it from above, as well as 
sidewise, the internal pressure 
when the tire is inflated pressing _. KAO __. t „,, T7 , ou . 

* ° Fi . 548. Views of Tire Valve, Showing 

it against these parts Very firmly. Closed and Open Positions 

In both the clincher and the quick-detachable forms, the bead 
holds the tire to the wheel by means of parts of the rim, which bear 
on it from above, as well as sidewise, the internal pressure when 
the tire is inflated pressing it against these parts very firmly. 

Tire Valves. In Fig. 547 there is shown a section through the 
tire valve but on a small scale. As this is a very important part 
and little understood, a larger view is shown in Fig. 548. This is in 
two parts, A at the left showing the valve closed, and B at the right 
indicating the position of the various parts when the valve is open. 
Note that the lower part of the valve is hollow, so that air inside of 
the tire has access to the valve seat. Note that the valve is held 
down on this by the threaded portion above it. This valve seat 


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forms a slight taper which rests against an equally slight taper 
inside of the valve stem. 

One condition of the tire valve holding air pressure is that the 
two valve seats be clean and smooth and free from scratches or cuts 
and foreign matter. Now it will be observed that the valve-seat 
portion of the valve has a hole through the center, in which the 
stem is a loose fit. This large hole passes all the way up through the 
threaded portion. The stem has a projection below the valve seat, 
which normally is held up against the bottom of the seat by the 
spring, this being strong enough to hold it up so tightly that no air 
can pass between the two. There are other conditions for valve 
tightness. The spring must be strong enough to hold these parts 
together; and the surfaces must be clean and true so that when 
held together, no air can get through. 

Action of Valve. The action of the valve is this: When air 
is pumped in, it passes down around the central stem until it 
meets the projection, which it forces down against the pressure of 
the spring and, when there is air inside, against the pressure of the 
internal air. As soon as this is pressed down, the air passes in, and 
if the external pressure is stopped, as at the end of a stroke of the 
pump, the spring and the internal pressure push the projection 
back into place, and no air can escape. On the next pressure stroke 
of the pump, this is repeated, the whole process continuing until the 
tire is filled. 

Leaky Valves. It will be noted that with a good clean spring, 
projection, and valve seat, the pressure of the air itself holds the 
valve tight. Thus, when a valve leaks, it is a sure sign that some 
part or parts of it are not in good condition. If the valve is not 
screwed down far enough, air can leak out around the valve seat, 
so that leakage may be remedied by screwing the whole valve farther 
down into the stem. If the valve stem is too tight a fit in the central 
hole, it may stick in a position which allows air to pass. This can 
be remedied by a drop of oil placed on the stem and allowed to 
run down it. But not more than one drop should be used as oil is 
the greatest enemy of rubber, and the tube with which the valve 
communicates is nearly pure rubber. 

If the spring is too weak to hold the projection against the 
bottom of the valve seat, the valve will leak. This can be remedied 


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by taking out and cleaning, the spring, also stretching it as much as 
possible. In general, however, the best plan of action with a 
troublesome tire valve is to screw it out and put in a new one. These 
can be bought for fifty cents a dozen, and every motorist should 
carry a dozen in a sealed envelope, also a combination valve tool. 
When trouble arises with the valve, or a tire leaks down flat with 
no apparent cause, screw out the valve with the tool, screw 
in a new one, make sure it is down tight, and pump up again. The 
few cents it will cost to throw away a valve, even if it should hap- 
pen to be good, will be more then compensated for by the time 
saved. Another point is that the whole valve assembly is so very 
small that it is difficult to handle. 

Washing tires often is a good practice, since water does them no 
harm, while all road and car oils and greases will be cleaned off, 
nearly all of these being injurious. Frequent washing will also serve 
to call the attention of the owner to minor defects while they are still 
small enough to be easily repaired, and thus they are prevented from 
spreading. When not in use, tires should be wrapped, so as to be 
covered from the light, and put away in a dry room in which the 
temperature is fairly constant the year round. They will not stand 
much sunlight, nor many changes in temperature. Cold hardens 
the tires and causes the rubber to crack. Heat has a somewhat 
similar effect and also draws out its life and spring. 

In general, of gll things to be cared for and repaired promptly, 
no one thing is of more importance than the tires. If this rule is 
kept in mind, better satisfaction in the use of the car will result. 
So, too, with other repair work; if tools and appliances are made 
available and repairs made as soon as needed, the car will be better 
understood and give more satisfaction than if the opposite course 
be pursued. A few months of use of a car will do more to emphasize 
this than any amount of talk. Keep your car in good condition 
and you will reap the benefits of the little work you do upon it. 

Repair Equipment 

Vulcanization of Tires for Repair Man. In practically all of the 
following material the point of view is that of the professional repair 
man, or of the garage man about to take up tire repairs, as dis- 


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tinguished from that of the average owner or amateur repairer. The 
lesser tire injuries and their repairs are handled from an amateur 
standpoint in another part of this work. 

Vulcanization, to the unitiated, sounds very mysterious, but 
it really is nothing more or less than cooking, or curing, raw gum 

Fig. 549. Small Vulcanising Outfit for Single Casing of Six Inner Tubes 
Courtesy of C. A. Shaler Company, Waupun, Wisconsin 

rubber. In the processes of manufacture a tire is cooked, or cured, 
all the component parts supposedly being united into one complete 
whole. A tire is repaired preferably with raw gum or fabric prepared 
with raw gum, and, in order to unite this to the tire, vulcanization 
or curing is necessary. The curing, in addition to uniting the parts 


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properly, gives the proper strength, or wear-resisting qualities, which 
raw rubber lacks. 

Types of Vulcanizing Outfits. Shaler Vtdcanizer. This curing, 
or cooking, is done by the application of heat, in a variety of ways. 
Generally, very small individual vulcanizers have a gasoline or 
alcohol cavity, holding just enough of the liquid so that when lighted 
and burned the correct temperature will be reached and held for the 
correct length of time. The larger units are operated by steam or 
electricity; the latter is preferred for its convenience,but the former is 
used by the majority of repair men. . The source of heat is immaterial 
so long as the correct temperature is reached and maintained for 
the right lengh of (ime. Too hot a vulcanizer will burn the rubber, 
while too low a temperature will not give a complete cure. 

For the average small repair man, the outfit shown in Fig. 549 
will do very nicely, at least to start with. This will handle a single 
casing or six tubes, or in a press of work, both simultaneously. This 
outfit is operated by gasoline, contained in the tank shown above 
at the right, but the same outfit can be had with pipe arrangements 
for connecting-to a steam main, or for electric heating. In the case 
of either gasoline or steam, there is an automatic temperature con- 
trolling device which is a feature of the Shaler apparatus. As shown, 
casings are repaired by what is known as the "wrapped tread method", 
the repair being heated from both inside and outside at once, the 
outside being wrapped. Tubes are handled on the flat plate, shown 
in the middle of the framework, the size of which is 4? by 30 inches, 
this being sufficient, so the makers say, to handle six tubes at once. 

Haywood Vulcanizer. For larger work, a machine something 
like the Haywood Master, shown in Fig. 550, is excellent. This is 
a self-contained unit, carrying its own gasoline tank, steam generator, 
and other parts. It handles four casings at once, while the tube 
plate G, 5 by 18 inches, is large enough for from three to four tubes, 
according to the allowance per tube made in the Shaler outfit. The 
separate vulcanizers are not designed for the same part of a casing, 
a side wall and bead vulcanizer being shown at D, a sectional vul- 
canizer for large sizes at E, a sectional vulcanizer for small and 
medium sizes at F, and a side wall and bead vulcanizer for both 
clincher and straight-side tires at H . The gasoline tank is marked 
C, with vertical pipe in which is the gasoline cut-off valve K. This 


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leads down to the gasoline burner M , where the gasoline in burning 
vaporizes the water into steam. The water gage L, which indicates 
the amount of water available, is placed on the side of the steam 
generator A. Above this steam generator is the steam dome at B 9 

Fig. 550. Master Vulcanizer with Self-Contained Steam Generator 
Courtesy of Haywood Tire and Equipment Company, Indianapolis, Indiana 

from which the steam pipes lead to the various molds. The returns, 
or rather drips, will be noted, also the steam gage (not marked) and 
the cut-off valve in the supply pipe to the sectional molds. In addi- 
tion to the molds shown and a full supply of parts and tools, sec- 
tional vulcanizers for 2§- and 3-inch tires, relining mold for 2§-, 3-, 


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and 3|-inch tires, and relining mold for 4-, 4|-, 5-, and 5J-inch casings 
come with the device. 

This outfit with the extra molds, described but not shown, gives 
a very complete equipment for the small shop doing average 

Fig. 551. Battery of Vulcanizing Mold for Various Sizes of Tires 

repairing. In fact, when a shop outgrows this type of equipment, 
it must specialize in tire work and purchase special equipment. 

Separate Casing Molds for Patch Work. In the way of sepa- 
rate molds for casings, an excellent example of the localized heat 
type is shown in Fig. 551. By this is meant the form designed to 
vulcanize a small short section of a tire. The illustration shows 
five sections capable of handling, respectively, 2£-, to 3-inch (motor- 
cycle), 2\- to 3-inch (small car), 3|- to 4-inch, 4|- to 5-inch, and 5§- to 
6-inch tires, thus covering the entire range. These molds have a 
special arrangement in that the heating portion is divided into three 
sections, into each of which steam can be admitted separately. This 
allows the use of one, two, or all the sections, according to the nature 
of the repair. 

In Fig. 552 is shown how it is 
possible, with this apparatus, to vul- 
canize the tread portion only by 
admitting steam solely to the larger 
bottom steam chamber around the 
tread, similarly, with the right-hand 
bead or side wall or the left-hand bead 
or side wall. When a complete sec- 
tion is to be vulcanized, all sections 
are opened. The importance of this 
will be realized in a simple consideration of the fact that the tire itself 
has already been vulcanized and further heat is not only not good for 
it, but is distinctly bad, as it deteriorates the rubber. Where the heat 

% 3 team Cavity -X ft 

Fig. 552. Section of Vulcanizer, 
Showing Steam Cavities 


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is needed, however, is not the raw rubber which has just been added at 

the repair point, this being practically useless until it has been cured. 
Vulcanizing Kettles. Horizontal Type. When it comes to 

vulcanizing an entire tire, as, for instance, when a new tread has been 

put on, or other very large repair, 
what is known in the trade as 
a "kettle" is needed. This is 
simply a heavy steel tank, large 
enough to take one or more entire 
tires, steam being admitted to its 
interior to vulcanize them. The 
kettle shown in Fig. 553 has a 
capacity of two casings 36 inches 
in diameter or smaller. It is of 
the type in which no bolts or nuts 
are used for fastening the cover, 
this being held fast by the pro- 
jecting lugs which lock under 
other projections on the top of 
the kettle when the cover is 
turned. A special rubber pack- 
ing ring also is used, Fig. 554, 
effectually sealing the kettle 

against steam leakage. This kettle resembles a doughnut in shape, 

the tires lying within the circular cavity. 

Fig. 553. Vulcanizing Kettle, Horizontal 

Teat Coch 

•5afdy Voire, 

-Teat Coch 

__ ^&lQ*> Off 
4^—ToJtetar-n on Thop 

Fig. 554. Section of Horizontal Vulcanizing Kettle 

5 team Supply- 

Large Vertical Type. When the work goes beyond the capacity 
of size and type of tank or kettle shown in Fig. 553, which will handle 


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two casings at a time, and at least two, perhaps four, kettles full 
an hour, that is, from 40 to 75 casings a day, it becomes necessary 
to use a larger type of kettle, made in vertical types only. These 
consist simply of large round steel shells with hinged heads, into 

fig. ooo. snaier Electrically Heated inside Uasing Form 

which the tires can be rolled and piled, after which steam is admitted to 
the whole interior. They vary in size from 36 inches inside diameter 
by 24 inches in length to 48 inches diameter by 40 inches in length. 

Inside Casing Forms. Another 
requisite of the tire specialist is an 
inside casing form, such as is shown 
in Fig. 555, or something similar. 
Many tire repairs are inside work, 
and even on those which are 
external, it is important to have an 
inside form against which the tire 
can be pressed and firmly held while 
vulcanizing. This particular form 
is heated by electricity, the wires 
being shown at the left; it is 14 
inches long and has an external 
shape to fit the inside of all casings. 

Side-Wall Viricanizer. A shop doing a great deal of work can 
use to good advantage the side-wall vulcanizer shown in Fig. 556. 

Fig. 556. Side-Wall Vulcanuer 


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It has a single central member through which the steam passes, and 
also has bolted-on side plates, the insides of which are formed to suit 
either clincher or straight-side tires. In the figure, the side plates are 
not both in place, one being shown on the work table below. The 
brace shown is used to remove the clamping nuts quickly and easily. 
This form is very useful on all side-wall or bead operations. It applies 
greater pressure along these parts of tjie tire than an air b&g; it exactly 

fits the tire, and the size and shape make it possible to vulcanize a 
36-inch tire in four settings. 

Retreading Vulcanizers. Retreading vulcanizers differ from 
the sectional molds of Figs. 549, 550, and 551 in that the heat is 
applied at one particular point or, rather, strip along the middle of 
the top surface of the casing and extending down only as far as 
the side walls. Such a device, shown in elevation in Fig. 557, and 
in enlarged sectional detail in Fig. 558, is used solely for retreading 
or vulcanizing a new tread strip around the tire. The complete 
unit extends around pbout one-third of the whole tire surface so that 



when putting on a complete new tread the mold must be used three 
times. The section, Fig. 558, is numbered as follows: casing, 2; 
inner mold, 1; new tread to be vulcanized, 3; vulcanizer proper, 4; 
clamp, 5; and steam space within which the heating is done, 6. 

Layouts of Equipment. There are two ways of installing an 
outfit somewhat like that just described, namely, by the non-return 
system and by the gravity- 
return system. 

Non-Return Layout. A 
typical installation according 
to the non-return system is 
shown in Fig. 559. A steam 
trap must be placed in the 
system to remove the water 
and discharge it either into 
the sewer or into a tank so 
that it can be used again. 
In the figure there is shown a 
tube plate, a three-cavity 
sectional vulcanizer, two in- 
side molds, and a medium 
size kettle of the vertical type 
placed in order from right 
to left. A pressure-reducing 
valve is shown which permits 
the use of a higher pressure 
in the boiler, thus maintain- 
ing an even steady pressure 

- , . ji Fig. 558. Section of Retarding Vulcanizer 

On the VUlcaniZerS regardless Courtesy of Haywood Tire and Equipment 

of fluctuations at the boiler. Company > India ^^ Indi «™ 

Gravity-Return Layout. When the coil steam-generator or flash 
type of boiler is used, the gravity-return system is utilized, this being 
a method of piping by means of which the condensed steam is returned 
to the coil heater to be used over again. This makes it necessary to 
set the apparatus so that the water of condensation will run back to 
the coil heater, which means that the pieces must be in a series, each 
successive one being set a little lower down to the boiler. Figs. 
560 and 561 show a side view and plan view, respectively, of a small 


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plant arranged on this plan. The outfit consists of the coil heater, 
which may be fitted to burn gas or gasoline, two inside molds, a large 
tube plate, and a three-cavity sectional vulcanizer. The outfit 

Kg. 500. Elevation of Gravity-Return Vulcanising Plant 

differs from Fig. 559 only in the absence of the kettle; on the other 
hand, the tube plate in Fig. 560 is larger. 

Small Tool Equipment. In addition to these larger units, the 
well equipped tire repair shop should have a considerable quantity 
of small tools, among the necessities being those shown in Fig. 562. 
At A is shown a flat hand roller and at B a concave roller. C shows 
an awl, or probe, which is used for opening air bubbles and sand blis- 
ters. D is a smooth stitcher; F a rubber knife, of which two sizes are 
advisable, a large and a small; and G a 10-inch pair of shears for 

Fig. 561. Plan View of Gravity-Return Vulcanising Plant 

trimming inner tube holes, cutting sheet rubber, etc. IT is a steel 
wire brush for roughing casings by hand; a preferable form is a 
rotary steel wire type driven by power at high speed. J is a similar 




wire brush for roughing tubes; and J another brush with longer 
wires, also for roughing casings; K is a tread gage for marking 
casings to be retreaded; and L a fabric knife necessary in stepping 
down plies of fabric, if is a pair of plug pliers for placing patches 
inside of small tube repairs; N is a cement brush for heavy casing 
cement, another very much smaller and lighter one — preferably of 
the camel's hair type — being used for tube cement. is a hand 

Fig. 562. Collection of Tools Necessary for Vulcanizing Work 

scraper and P a tread chisel; Q performs a somewhat similar function, 
being a casing scraper for cleaning the inside of a casing preparatory 
to mending a blowout. 

In addition to the small tools shown in Fig. 562, it is necessary 
to have several tube-splicing mandrels; a large number of various 
sizes and shapes of clamps for all purposes; rules, try-squares and 
other measuring tools; tweezers for handling small patches, tools 
for recutting threads on tire valves; tire spreaders, for holding casings 


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open when working inside; a casing mandrel or tire last of cast iron 
for holding a casing when making repairs; a tread roller for rolling 
down layers of raw stock evenly and quickly; a considerable amount 
of binding tape; thermometers; and such motor-driven brushes, 
scrapers, etc., as the quantity and quality of the work warrant. 

Materials. Each repair shop must carry such a supply of tire- 
repairing material as the nature and quantity of its business demands. 
Among other things may be mentioned: Tread stock, rebuilding 
fabric, single-friction fabric, cushion stock, breaker strips, single- 
cure tube stock, combination stock, cement, quick-cure cement, 
soapstone, valve bases, valve insides, valve caps, complete valves, 
vulcanizing acid, various tube sections, tire tape, cementless patches, 
as well as many other tire accessories to sell. Many good tire-repair 
shops find a legitimate use for special tire-repairing preparations on 
the order of Tire-Doh. 

Inner Tube Repairs 

In general, all tire repairs come under one or more of the following 
headings; puncture; blowouts; partial rim cut or rim cut all around; 
and retreading or recovering, and relining. 

Simple Patches. Under the heading of punctures are handled 
all small holes, cuts, pinched tubes, or minor injuries. Generally, 
these can be repaired by putting on a patch by means of cement, 
or with cement and acid curing. When well done, this method is 
effective. This kind of a job seldom comes to the repair man, and, 
when it does, it is principally because the owner is too lazy to do the 
work. About the only two cautions necessary are relative to clean- 
liness and thoroughness. The tube and patch should be thoroughly 
cleaned. Again the patch should be large, well cemented, and the 
cement allowed to dry until just sticky enough to adhere properly. 
Many a simple patch of this kind has been known to last as long as the 
balance of the tube. 

Large Patches. Cleaning the Hole. Whenever the hole or 
cut is large, it is recommended that the repair be given more serious 
attention and vulcanized. The ragged edges of the rubber should 
be trimmed smooth with the tube shears or knife, the minimum 
amount of rubber being cut away. The hole, however, should be 
made large enough to allow the insertion of an inside patch. Then 

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the tube around the hole should be cleaned thoroughly. This is best 
done with a cloth wet with gasoline, cleaning not only the outside 
but the inside around the hole and at the edges. In order to make a 
good job of this, it should be gone over several times; the larger the 
hole the more care should be used in cleaning around it. 

Preparing the Patch. Having the hole well cleaned and ready, 
these cleaned parts should be painted with two coats of vulcanizing 
cement, which is allowed to dry. This must be thoroughly, not partly, 
dry. Then the proper patch is selected, the smaller size being 
sufficient for small patches, while in the case of large repairs, the 
patch should be from £ to 1 inch larger all around than the hole. 
If this is not a prepared patch, one side should be cemented just as 
the tube was previously. If a prepared patch is used, the semi- 
cured side should be placed in, that is, with the sticky or uncured 
side toward the tube from the inside. 

When the cement on the patch is just sticky enough, it should be 
inserted and the tube pressed down against it all around, slowly 
and carefully so as to get. good adhesion. Next the cavity about 
the inside patch is filled with gum or pure rubber, preferably in sheet 
form as it comes for this purpose. This is filled in until the surface 
is flush. It is preferable to use a little vulcanizing cement to hold 
this rubber in place, particularly if a piece of sheet gum is cut to 
fill the hole. 

Vulcanizing tlie Patch. The repair is now about half completed 
and is next vulcanized. The length of time, if steam is used, varies 
with the amount of steam pressure; if the portable gasoline or alco- 
hol type of vulcanizer is applied the time varies with the temperature. 
As this time variation is so wide, it is impossible to give an invariable 
rule. Thick tubes require a little longer than thin ones, large patches 
longer than small ones, wide patches more than narrow, etc. The 
vulcanizing must be carefully and thoroughly done, and, as the 
success of the whole job depends upon this one process, the arrange- 
ment of the tube on the plate, of the soapstone on the new rubber 
and on the vulcanizer to prevent adhesion, of the wood or rubber 
pad above the patch, of the clamp and its pressure, should all have 
careful attention. With 60 pounds steam pressure available, from 
10 to 12 minutes is about right, with 75 pounds from 8 to 10 minutes. 
Jn any case, the rubber should be cured just firm enough not to show 


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a slight indentation from the point of a lead pencil. This is a good 
test to use at first, although after a short experience, the workman 
will be able to judge of the condition from the feeling, color, and 
general appearance of the patch. 

When the size of the plate is small, the tubes should be held up 
above it out of the way, partly to allow the full use of the plate 
surface, but also to keep the tubes from being damaged. 

Inserting New Section. Preparing the Tithes. In case the 
damage to the tube is too great to permit the use of a patch, for 
instance, in case a blowout makes a wide hole perhaps 7 inches 
or more long, in an otherwise good tube, it is advisable to cut out 
the damaged section and insert a new section in its place. Some- 
times old tubes of the same size can be used for this, but, if not, 
sections can be purchased from the larger tire and rubber companies. 

Fig. 563. Sketch Showing Method of Inserting New Section in Inside Tube . 

In the repair, proceed as follows: After cutting out the damaged 
section, bevel down the ends very carefully, using a mandrel to 
work on and a very sharp knife. As the appearance and, to a large 
extent, the value of the repair will depend upon these beveled ends, 
this should be done in a painstaking manner. T* Next select the tube 
section and cut it to size, that is, from 5 to 6 inches longer than the 
section which was cut out and which this patch is replacing. - This 
allows 2\ to 3 inches for the splice at each end/ * Bevel the ends of 
the tube as well, and, after beveling all four ends, roughen them 
with a wire brush or sandpaper. 

Making the Splice. Having the tube and repair section beveled 
and buffed, the ends to be joined should be coated with one heavy 
or two light coats of acid-cure splicing cement. With the tube and 
patch properly placed on the mandrels — tube on the male and patch 
on the female — turn back the end to be repaired and the end to be 


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Worn Tread 


applied as shown in Fig. 563. At A is shown the female mandrel 
on which is the patch B, turned back from the end of the mandrel 
about the right distance, say 3 to 3J inches. On the male mandrel C 
the tube D has been turned back about 7 to 7J inches, then turned 
back again on itself about 3 to 3$ inches. 

Just as soon as the cement has dried thoroughly on the tube, apply 

a coat of acid to the patch and 
immediately place the two 
mandrel ends together and 
snap, blow, or push the end of 
the patch over on to the end 
of the tube. This frees the 
female mandrel, which can 
be laid aside. Immediately 
wind the patched portion 
(ptill on the male mandrel) 
with strips of muslin or inner 
tubing. In 15 to 20 minutes 
the cement will have formed 
a permanent union, the wrap- 
pings can be removed, and 
the tube withdrawn through 
the slot in the mandrel. 

This done successfully, 
the whole operation is re- 
peated for the other splice. 
If the splice does not cure 
together well, it indicates 
either that the acid supply is 
poor or else the splicing was 
not done quickly enough 
after applying the acid. 

Rim Cut 

Leaky Valve- 

Fig. 564. 

Section of Tire, Showing Forms 
of Troubles 

Outer Shoe, or Casing, Repairs 

Classifying Troubles. Some of the common tire troubles — 
those of the inner-tube variety just discussed, and casing troubles 
as well — can be clearly shown by suitable illustrations. For example, 
a section through the tire showing how the troubles occur is some- 


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times very useful, as shown in Fig. 564. Here th^ pinched tube 
and blowout are indicated, the results of these on the inner tube 
and also their method of repair having just been described. These 
troubles together with punctures, leaky valves, and porous rubber 
in the tubes about cover the extent of inner tube troubles. Because 
of their more complex construction, casings have more numerous 
and more varied troubles, which, consequently, are more difficult 
to repair. The more common casing troubles are blisters, blowouts, 
rim cuts, and worn tread, the latter indicating the necessity for 
retreading. These will be described 
in order. 

Sand Blisters. The sand blister 
shown on the side of the tire, Fig. 564, 
is brought about by a small hole, such 
as an unfilled puncture hole, in com- 
bination with a portion of the tread 
coming loose on the casing near this 
hole. Particles of sand, road dust, 
dirt, etc., enter, or are forced into, 
this hole and move along the opening 
provided by the loose tread. Soon 
this becomes continuous and the 
amount of dirt within the break forces 
the surface rubber out in the form of a 
round knob known as a sand blister. 
This is cured by cutting open the 
blister with a sharp knife on the side 
toward the rim and picking out all 
dirt within. When the recess is 
thoroughly cleaned, the hole and the 
radial hole in the tire tread nearby Fi £ f^f^ 
should be filled with some form of inside Method 

self-curing rubber filler, a number of kinds of which are sold. The 
double benefit of this is to close the hole so that the trouble is not 
repeated and to keep out moisture which would ultimately loosen the 
entire tread. 

Blowouts. The blowout, which is perhaps the most important 
casing repair, may be made in two ways: the inside method, in which 


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the whole repair is effected on the inside; the combination inside 
and outside method. 

Inside Repair Methods. Refer back to Fig. 564 for the general 
tire construction and to Fig. 565 for this particular case, the inside 
of the tire is held open by means of tire hooks and the inside fabric 
layers or plies removed for a liberal distance on each side of the 
opening. As shown in Fig. 565, a lesser amount of the second layer 
should be taken than of the first, and still less of the third and each 
subsequent one. On 3§- and 4-inch tires it is not advisable to remove 
more than two plies; on 4^-inch tires three, as shown; and on the larger 
sizes four plies. The edge of each layer of fabric should be beveled 
down thin, as well as the material directly around the blowout. 

Fig. 566. Method of Preparing Fabric for Blow-Out Patch — Inside and 
Outside Method 

Apply a coat of vulcanizing cement and when it has dried, say 
for an hour, apply another. When this has dried enough to be 
sticky or tacky, fill as much of the hole as possible with gum. When 
this is filled in level, apply the fabric patch. This is made up to 
match the fabric cutout, that is, if three layers are removed, it should 
consist of three plies stepped-up to match, and an extra last ply of 
bareback fabric unfrictioned on one side. This last layer should 
extend 3J to 4 inches beyond the ends of the patch. 

When this is properly applied and carefully smoothed down, the 
tire is placed in a sectional mold, clamped in place, perhaps wrapped 
with muslin strips to hold it tightly against the mold, and heat applied 
from the inside. This makes an excellent repair and a fairly quick 
and easy one, but it is not applicable for large blowouts; at least, it is 
not as effective as the inside and outside method. 


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Inside and Outside Method. In the inside and outside method, 
the material is removed from the outside, stepped down, and beveled 
in the same manner as for the method just described. Fig. 566 shows 
a tire with a medium size blowout, which has been stepped down 
for a sectional repair, four plies having been removed. The rule for 
the number of plies to remove is about the same as before, except that 
in the larger sizes this should depend more on the nature of the injury. 
It should be noted, however, that in this case the plies have all been 
removed right down to and including the bead. This is done to give 
the new fabric a better hold and to make a neater job and one that 
will fit the rim better. Give the whole surface two good coats of 
vulcanizing cement, allowing it to dry thoroughly. 

Apply the same number of plies of building fabric as were 
removed, with the addition of chafing strips of light-weight fabric 
at the bead. Over this building fabric apply a thin sheet of cushion 
gum, slightly wider than the fabric breaker strip; then a thickness 
of fabric breaker strip over this; and then over this fabric another 
sheet of gum, slightly narrower than the previous sheet. All this, 
however, should be built up separately and applied as a unit and 
not one at a time, as described. These several plies should be well 
rolled together on the table. All edges should be carefully beveled off, 
especially the edges of the new gum where it meets the old, as it is 
likely to flow a little and leave a thin overlap which will soon pick 

No fabric is removed from the inside, but the hole is cleaned, its 
edges beveled, then filled with tread gum, and the inside reinforced 
with a small patch of building fabric; over this lay two plies of 
building fabric of considerable size. Now the whole casing is placed 
in a sectional mold, a surface plate applied to the outside, and heat 
applied both inside and outside. This will heat the tire clear through 
and make a good thorough job of curing. 

Rim-Cut Repair. Partial Cut To repair a partial rim cut, 
one or two plies of the old fabric are removed, unless it is severe, 
when three plies may be taken off. This is removed right down 
clean as explained under Blowout Repairs, and the cement and new 
materials applied in the same way, with the omission of the fabric 
breaker strip. However, care should be used to carry all building 
fabric layers not only down around the bead to the toe but up on 

333 Digitized by G00gle ,- 


the inside far enough to secure a good hold and ample reinforce- 
ment. If this should make the rim portion somewhat more bulky, 
remember it was a case of doing this or getting a new tire. 

Complete Rim Cut Where the rim cutting is continuous, the 
old side-wall rubber is removed up to the edges of the tread, and 
the old chafing strips and one ply of old fabric to about an inch above 

the beads removed also. 
Cut through the side- 
wall rubber all around, 
but be very careful not to 
cut into the fabric body, 
or carcass. The whole 
of the side wall and 
chafing strips can be 
removed in one opera- 
tion. Apply two coats 
of cement and, after this 
is thoroughly dry, put on 
a patch consisting of one 
ply of building fabric, 
one ply of chafing strip, 
and a surface, or outside, 

Fig. 567. Method of Handling Rim Cuts , - . 

ply of new tread gum. 
This is made on the table and the parts thoroughly rolled together. 
When completed, vulcanize in a sectional mold with sectional air 
bag and bead molds or endless air bag; apply to a split curing-rim 
wrap, and vulcanize in heater or kettle. The tire is repaired, but 
not vulcanized, and, with the ends of the three applied plies of mate- 
rial loosened to show, may be seen in Fig. 567. 

Retreading. Retreading is a job which must be done very 
carefully, not only because of the job itself, but also because this 
is probably the most expensive single job which can be done to a 
tire, and the worker should make sure before starting that the wire 
warrants this expense. It should have good side walls and bead, 
and the fabric should be solid and not broken apart. 

Repairing the Carcass. In the usual case, it is advisable to 
remove not only the surface rubber and fabric breaker strip, but 
also the cushion rubber beneath the breaker strip, that is, the tire 




should be cleaned off right down to the carcass, and the latter cleaned 
thoroughly. As the rubber sticks, a rotary wire brush will be found 
useful and quick. However, this should be used carefully so as not to 
gouge the carcass. After buffing, the loose particles of rubber should 
be removed with a whisk broom or dry piece of muslin. In this 
cleaning work the carcass should be kept clean and dry. Apply two 
coats of vulcanizing cement and allow both to dry; the first should be 
a light coat to soak into the surface fabric; the second should be a 
heavy coat. 

Building Up the Tread. In building up the tread, it should 
not be made as heavy as the former tread, as the old worn and 
weakened carcass cannot carry as heavy a tread as when new. 
Furthermore, it takes longer to vulcanize a heavy tread and presents 
more opportunity for failure. In the building-up process, the pro- 
portioning of weights is important, and should be taken from the tab- 
ulation below, which represents years of experience in tire repairing: 

Size of 







Last Ply 
Over All 






























♦See Note 
♦See Note 
♦See Note 
♦See Note 
♦See Note 
♦See Note 
♦See Note 

3 plies 

4 plies 
4 plies 

4 plies 

5 plies 

6 plies 
6 plies 

* Note — Determined by condition of case after buffing and cementing. 

Size of Case 








Width of Breaker Strip 








This tread strip is built up on the table with exceeding care, 
all edges being rolled down carefully. When the strip has been 
prepared and the carcass is ready for it, one end should be centered 
on the carcass, and then the balance of the strip applied around the 
circumference, being careful to center it all around, as the workman 
in Fig. 568 is doing. After it has been applied all around, it should 


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be rolled down carefully, all air pockets opened with a sharp pointed 
awl, and the gum at the edges of the plies rolled down with the 
corrugated stitcher. When ready, vulcanize in a kettle, using an 
endless air bag with tire applied to a split curing-rim, and wrapped — 
preferably double ^Tapped — all around. 

Use of Reliner. Many a casing which appears good on the out- 
side but which really is unsafe because of fabric breaks on the inside 

)orarily prolonged, 

t. By this is not 

and fabric reliner 

a regular built-up 

lized in place so as 

to be an integral 

part of the tire. 

For ordinary 

breaks, use a 

single ply of 

building fabric 

on a casing 

which has been 

entirely cleaned 

out and which 

has had two 

coats of vulcan- 

izing cement 

thoroughly dried 

eak, use two plies 

fit; the under ply 

ides and coated on 

Jig. 568. New method of 0ne > and the U PP er Ptf Sn ° uld be ^ictioned 
Jutting on New Tread on Qne ^ on j y> the s ; de towar( J t h e tube being 

bareback. Use an endless air bag for internal pressure, apply to a 
split rim, wrap, and vulcanize in a kettle from 35 to 45 minutes at 
a steam pressure of 40 pounds. 

Summary. By the application of parts of the foregoing instruc- 
tions and the use of much common sense, coupled with a knowledge 
of the construction, use, and abuses of tires, the repair man will be 
able to handle any form of tire repair brought to him. In starting 

336 Digitized by 



out, perhaps he could not do a better thing than to take an old tire 
apart to see just how it is constructed. This will give a much more 
clear idea than any number of diagrams, sketches, or photographs. 

The tire repair man should remember, too, that this is no longer 
a game, but that, by means of scientific apparatus and the appli- 
cation of correct principles, it has been brought up to a high state 
of perfection; an expert can predict with reasonable accuracy what 
will happen in such and such a case, if this and that are not done. 
In short, the tire-repairing business within the last few years has 
been brought up to a stage where it, or any part of it, is a dependable 
operation. The tire repair man should handle all his work from 
this advanced point of view; it will pay the largest dividends in 
the long run. 


Q. What are the units comprising the final-drive group? 

A. Universal joints; driving shaft; final gear reduction; axle- 
shaft differential; axle enclosure; torque rod, or tube, or substitute 
tor this: radius rod, or tube, or substitute for this; brakes; wheels; and 

Q. Why are these called the final-drive group? 

A. Because they constitute the final drive of the car, beyond the 
power-producing unit, the engine; the connecting and disconnecting 
unit, the clutch; and the speed-changing unit, the transmission. 

Q. What is the function of the universal joint? 

A. In the final-drive group, it is used to transmit power at an 
angle, as, from a horizontal-transmission shaft to an inclined-driving 

Q. How does it do this? 

A. The construction is such that the driving shaft is attached 
to one set of pins, while the driven shaft is attached to another, the 
axes of these intersecting in a common point. As the driven shaft can 
turn about its pins in one plane and, with the complete joint, about the 
driving shaft pins in another, as well as combinations of the two, 
complete freedom, or universal movement, is assured. 

Q. What are the power losses in a universal? 

A. In a well-designed and fitted universal joint, working prac- 
tically at zero angle, there is no loss, but as the angle increases, the loss 
increases until at about 20 degrees, it may reach 2 or 3 Der cent. 




Q. Why is such a joint needed? 

A. The final drive must be at the center of the rear axle, which 
is comparatively low, say 17 inches with 34-inch wheels or 18 inches 
with 36-inch wheels, while the power must originate at the engine 
which cannot be set as low as this, that is, the power must be gen- 
erated at a higher level than that at which it is used. An inclined 
shaft and universal joints must be used somewhere in the system. 

Q. What other considerations necessitate universal joints? 

A. The engine level varies little, while the rear end of the chassis 
varies up and down through a considerable range. In addition, the 
rear end carries perhaps 85 per cent of the load and sustains greater 
road shocks because of this fact. The design is such as to keep the 
front, or engine, end as quiet and as nearly stationary as is possible. 
These considerations necessitate a flexible connection between the two 
ends, so that one can move frequently and through considerable 
distances, while the other moves seldom and through very small 
distances. In addition, the rear end must sustain considerable side 
sway, so that freedom in a sidewise direction is necessary. The only 
way in which these necessities can be obtained is through the use of 
universal joints. 

Q. What is a slip joint? 

A. One which will allow sliding, or slipping, of one part or shaft 
within the other. Thus, under certain restraining conditions the rise 
and fall of the rear end may mean approaching or receding of that end 
to and from the front portion. With a slip joint, this is made easy. 

Q. What is the usual form of a slip joint? 

A. Generally, this takes the form of a squared shaft within a 
squared-out housing, although sometimes the square is rounded off 
to give a slight universal action. 

Q. What is the modern form of universal joint? 

A. A thin flexible disc of steel, leather, fiber, or laminated fabric, 
with the driving shafts bolted to two opposite points and the drive 
shaft bolted to two others between them has been found to be much 
simpler, lighter, cheaper, and better than the average universal, 
although it allows only limited angular motion. The engine is being 
gradually lowered, while the rear wheels are constantly being 
increased in size; so the difference of level is not as great as it was, and 
there is less need for the full universal. 

goo Digitized by 



Q. What is the biggest advantage of these to the repair man? 

A. They allow the removal of a driving shaft, or a unit on either 
side of such a joint much more quickly and easily, with less work, 
than any other form, similarly, in replacement after the repair is 
completed. In addition, they have no loose parts to be lost or mis- 
laid with consequent trouble and delay of the work. 


Q. What is the usual type of driving shaft? 

A. The usual driving shaft is of small diameter and solid. 
Cold rolled steel is used on the lower priced cars, but forged steel 
machined at the ends (at least) is used on the better cars. On many 
of the most expensive machines, the shaft is fairly intricate in shape 
and is machined all over after forging, sometimes ground after har- 

Q. What would be the advantage of a spring shaft? 

A. Being flexible, it would cushion the shocks so that none of 
these reached the engine. Such shocks as are induced by jerking 
the throttle wide open, or stepping on the accelerator pedal suddenly 
or, on the other hand, a sudden application of the brakes. 

Q. What is its real disadvantage? 

A. Being small, the owner of the car and the driver would 
always mistrust it, and would not feel free to drive as they would with 
a larger and more dependable shaft. 

Torque and Radius Rods 
Q. What is torque? 

A. Torque is turning effort, or force, applied to rotation, in the 
case of an automobile, to rotation of the driving shaft, and from it to 
the rear axle and wheels by means of the final reduction gears. 

Q. What is a torque rod? 

A. A rod, bar, or tube, provided to take, not the torque, but the 
equal opposite reaction from the torque application to the final drive. 

Q. What is the manifestation of this torque reaction? 

A. A tendency of the driving shaft and driving bevel gear to 
rotate up and around the bevel-driven gear in a counter-clockwise 

Q. How does the torque rod absorb this? 

A. By extending this forward and attaching it to a frame cross- 




member at the front end and to the rear axle housing at the rear end, 
this counter-clockwise motion of the driving shaft is prevented. 

Q. What is driving effort? 

A. The force applied to the rear wheels tending to move the 
car forward. It is transmitted to the car, or frame of the car, as 
a push. 

Q. How is this push transmitted to the frame? 

A. In one of three ways; through special radius rods which 
transmit it directly to the frame; through a central tube which handles 
both torque and driving effort, transmitting this first to a frame cross- 
member, then to the main side members and through the springs, 
which are modified in attachment so as to take care of these extra 

Q. Which is the best form? 

A. The use of radius rods, one on each side, transmitting the 
stresses directly to the frame, is undoubtedly the best form, but also 
the most expensive, the heaviest, and includes the greatest number of 

Q. Which is the most simple form? 

A. The use of the springs, the so-called Hotchkiss drive, but this 
also reduces the easy-riding qualities of the car because the springs, 
which should be flexible for easy riding, must be made somewhat 
rigid in order to transmit torque and driving reactions. 

Q. Which is the cheapest? 

A. Undoubtedly the use of the springs is the cheapest form, as 
it eliminates all additional parts, and simply necessitates a pivoted 
form of springing end in place of the usual shackle there. 


Q. What are the usual methods of final drive? 

A. Final drive is usually by one of these methods: roller chain, 
silent chain, spur gear, bevel gear, spiral bevel gear, worm and gear, 

Q. Are all of these in use today? 

A. All but the roller, although the two forms of chain drive 
have almost gone out of use for pleasure cars and are becoming less 
popular even for truck use. 

Q. Which is most popular? 




A. For pleasure-car use, the spiral bevel form, and for motor 
trucks, the worm. 

Q. Why is the spiral bevel popular on pleasure cars? 

A. Because of its many advantages. It is just as simple as the 
straight bevel, needs no additional parts, is more quiet, perhaps more 
efficient, is less likely to cut or wear, can be removed as readily, and 
has other minor advantages. 

Q. Why is the worm popular for trucks? 

A. It has all the needed qualities; it is efficient, silent, easy to 
handle, and allows bigger gear reductions than any other form. 
Furthermore, various gear reductions are interchangeable by changing 
other parts, and the worm has other advantages. 

Q. Why is the worm not used more on pleasure cars? 

A. Because it is not so well adapted to high speeds of 50 to 60 
miles an hour and higher, which may be demanded, and because the 
large reduction between engine and rear axle, which is its biggest 
advantage, is not needed on pleasure cars. 

Q. What are the three mostly used forms of rear axle? 

A. The full floating, semi-floating, and three-quarter floating. 

Q. Which is the best form? 

A. From an engineering standpoint, the full floating is undoubt- 
edly the best, but it is also the most complicated, with the largest 
number of parts, and the most expensive to construct. 

Q. Which is the most simple form? 

A. The semi-floating form is the most simple, but it lacks 
advantages which the majority of car owners want. It is the cheapest 
to make, but is made so through the lack of these advantages. 

Q. Which is the compromise form? 

A. The three-quarter floating form seems to offer a maximum 
number of advantages with the minimum of disadvantages. It has 
practically all the advantages of the full floating with less cost. It 
has all the advantages which the semi-floating lacks and costs but 
little more. 

Q. Which is the most popular form? 

A. The floating still has the greatest number of makers, but the 
three-quarter form is rapidly gaining in popularity and, in another 
year, will displace the full floating as the most popular, both as to 
the number of makers and as to the actual number of cars. 


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Q. Describe the internal=gear axle? 

A. In this form a spur gear is used to drive an internal gear of 
larger diameter. This construction enables the separation of load 
carrying and power transmitting, so that one part of the axle can 
handle each. 

Q. For what is this used mostly? 

A. The internal-gear axle is used mainly on motor trucks, 
although a few heavy pleasure cars have been built with it. 

Q. What is a differential? 

A. A mechanical device for allowing the rear wheels to travel 
different distances when turning a curve or corner. 

Q. How is this done? 

A. By combinations, or nests, of gears and a divided rear axle, 
one-half being fixed to each half of the differential, with only the nests 
of gears connecting the two. As these are free to revolve as a unit, 
or stand still and have their gears revolve, the drive can either be 
transmitted all to one wheel, half to each wheel, or divided unequally. 

Q. Wliat is the usual differential form? 

A. The usual differential gear is constructed with bevel or 
spur gears, the bevel form being more popular, the spur cheaper. 

Q. What is undesirable in present differentials? 

A. Present differentials have the disadvantage that they work 
for resistance not distance. This permits the wheel, which we do not 
want to slip, to slip on icy places so that the car cannot pull itself free, 
the differential making a bad matter worse. 

Q. If the differential worked correctly, how could this be? 

A. In such a case, since the differential worked only for differ- 
ence in distance, and there was no difference in distance on an icy 
place, the power would be transmitted equally to the rear wheels. 
One would slip, but the other on firm ground would use its share of 
the power to pull the car off the icy place. 

Q. How is it expected that this result will be attained? 

A. By the use of helical gears, which, like the w # orm of a steering 
gear, are not reversible but will transmit power only in one direction. 

Q. In addition to correct differentiation, what is it expected 
these differentials will do? 

A. Eliminate skidding, always dangerous and always a possi- 
bility with present forms. The connection between skidding and 




present differentials has never been explained, but can be readily 
proved by the simple process of building a car without a differential. 

Q. What forms of bearings are used in rear axles? 

A. All the different kinds of bearings are used in rear axles: 
plain ball, plain straight solid roller, straight flexible roller, tapered 
roller, a few plain bronze beiarings, ball-thrust forms, and others. 

Q. Which form is most popular? 

A. There is little choice between the two forms of roller and the 
ball bearing. In fact, the majority of axles use several different forms 
of bearings; so it is difficult to compare the work of the various bearing 

Q. How can a broken spring clip be repaired? 

A. A good substitute for a spring clip can be made from two 
flat plates and four bolts to reach from one plate to the other. The 
purpose of the spring clip is to hold the spring to the axle; this combi- 
nation will do the same thing. 

Q. How would you line up a rear axle? 

A. With a try-square and plumb bob, working downward from 
the main frame, determine the distance from the rear end of the frame 
to the back side of the rear axle, on each side of the car. If the two 
do not agree exactly, the axle is out of square by the difference, or by 
half this difference on each side. Loosen the spring bolts, set the axle 
correctly, tighteh the bolts, and check up the measurements again. 


Q. What are the two general types of brakes? 

A. The contracting-band, which is an external brake, and the 
internal-expanding shoe. 

Q. How are these used? 

A. There is no set rule; some designers use only the internal- 
expanding form, claiming this is more powerful and dependable; 
others use only the band, claiming this is cheaper to make and repair 
and just as good; still others take no side but use both forms. 

Q. Has there ever been any agreement in relation to brakes? 

A. Up to about a year ago, it was general practice to use the 
internal-expanding shoe brake for the emergency, or hand, brake,. 
This was the case whether the band form was used for the foot, or 
running brake, or another expanding shoe. 

843 ' ^Digitized by G00gle 


Q. Does this rule hold now? 

A. No. Many hand-operated brakes are of the contracting- 
band form, while many foot-operated forms, which would be consid- 
ered the service, or running, brakes, are internal expanding. The 
tendency toward unit power plants is bringing back a shaft brake of 
the band type, operated by the hand lever. 

Q. Where are the brakes generally located? 

A. Except for the tendency just mentioned, the brakes have 
been located as much as possible in the rear wheels, on the assumption 
that this gave the most direct and thus the best application of the 
braking force. 

Q. How are brakes arranged on the rear wheels? 

A. When both brakes are placed on the rear wheels, practice is 
sharply divided into two camps. The one places the running brakes 
as a band form on the outside of the drum, claiming this makes 
a smaller .lighter drum, a more compact group on the wheel, and less 
expensive because the drum is cheaper. The other places the two 
brakes side by side, making both of the internal-expanding shoe form 
inside a wide drum, claiming this is more effective, more powerful, 
and that the brakes are better protected against dirt, dust, and water 
because entirely enclosed, and thus are more effective and need less 

Q. What is the electric brake?* 

A. A new device which substitutes the rotation of an electric 
motor for hand or foot application of the brakes. This is put into 
action by a finger lever on the steering post, which makes contact, 
through suitable resistance, between the battery and the motor. When 
the motor rotates a cable is wound up and this pulls the brakes. 

Q. Is this a powerful form? 

A. Not only very powerful but also very quick to act, so that 
care must be used in applying it. 

Q. What is the hydraulic brake? 

A. A new form for heavy trucks and tractors, in which the use 
of an oil, which transmits power equally and without loss, is substi- 
tuted for the usual rods and levers in the application of the brake. 
The construction is such that the driver can apply the brakes by a 
stroke of the hand lever, and if this does not give sufficient power to 
stop the truck, he can let the lever go forward and then pull it back- 


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ward again; this action soes not release the brakes but does apply 
more force, that is, it can be worked continuously until sufficient 
power is applied to stop the vehicle, a peculiarity of this particular 

Q. What is the vacuum brake? 

A. . A new form which utilizes the suction of the engine to create 
a vacuum in a special braking cylinder, the movement of a piston in 
which applies the brake. The amount of action depends on the 
amount of suction, that is, regulated by the amount the valve is 
opened, and this is dependent upon the pressure applied to the finger 
lever or toe button, whichever is used. 


Q. What are the usual forms of pleasure-car wheels? 

A. The plain wood form and the wire wheel comprise 99 per 
cent of all pleasure-car wheels; the wood forms about three-quarters 
and the wire about one-quarter of the total. 

Q. What are the tendencies in wheel sizes? 

A. On small cars the tendency is toward larger and larger sizes, 
but on the larger heavier cars the tendency is away from the very large 
sizes of a few years ago. The latter tendency has been brought about 
by the standardization of tire sizes, and the elimination of 38s, 40s, 
and larger sizes formerly made. 

Q. What are the different forms of wire wheels? 

A. The double-spoke form, which is lacking in lateral strength; 
the triple-spoke; and the quadruple-spoke. The two latter make up 
in strength what the former double-spoke form lacked. Except for 
number of spokes, these do not look any different to the casual 

Q. What is the sheet-steel wheel? 

A. A form in which the whole wheel construction consists of a 
pair of sheet-steel members. These are given a slight taper, some- 
times have holes through them for ventilation and to make them 
lighter, and frequently are painted to resemble wood-spoke wheels. 
The steel sheets are made thin enough to be flexible. 

Q. What is the pressed-steel wheel? 

A. A newer form in which a simulation of one-half the entire 
wheel spokes, hub and all, is pressed out of thin sheet steel, and a pair 


Digitized by 



of these welded together so that the finished product has all the 
appearance of a wood wheel with the usual number of spokes, but 
without the rim which this construction eliminates. 

Q. What are the usual truck wheel forms? 

A. Most truck wheels are of heavy wood or cast steel. The 
latter do not weigh a great deal more than the former; because oi the 
greater strength of the material, less of it can be used. 

Q. Which is the most popular? 

A. The wood form is still the most popular, despite its disad- 
vantages for heavy truck use, but the steel form is gaining rapidly? 

Q. What are the advantages of steel? 

A. Greater strength, particularly to resist side stresses; better 
ventilation and removal of heat from the tires; more firm foundation 
for the tire so that it holds its shape better; and longer life at less cost. 


Q. What are the general divisions of all tires? 

A. Pneumatic, cushion, and solid. 

Q. What is the principle of each? 

A. The pneumatic tire has an interior air bag which is pumped 
full of air, the tire gaining its resiliency from this. The cushion tire 
is so constructed as to have a central air passage or other yielding 
space so that it gives a cushion effect under loads. The solid tire is a 
solid mass of rubber, its only give being the natural yield of the rubber. 

Q. Is there a distinct field for each? 

A. Yes. Pneumatics are used only on pleasure cars and the 
lighter trucks or delivery wagons; cushion tires are used mostly on 
slow-speed electric pleasure cars and a few light trucks; solid tires are 
used only on the heavy trucks. 

Q. What is the big disadvantage of the pneumatic form? 

A. Its liability to puncture or blow out, or loose its air other- 
wise, after which the tire is useless until the fault is mended; in fact, 
the tires are actually in the way, and running a deflated tire only cuts 
it to pieces. 

Q. What are the divisions of pneumatic tires according to shape 
and method of holding? 

A. While there are other forms, practically all tires today are in 
one of two classes, the clincher or the straight side. 

346 v 

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Q. Describe the clincher type? 

A. This is made with a bead or hard portion at the base, which 
forms a projection around which the clincher rim fits. The rim has 
the shape of a flattened U with the ends curled in, and the beads on 
the tire fit into these curled ends or clinches. 

Q. What is the advantage of this? 

A. The clincher form is held firmly on the rim, while the stiffness 
of the bead contributes more rigidity of form and permanence of 
shape to the whole tire. 

Q. Describe the straight-side form. 

A. This type of tire has no bead, the fabric forming the side 
walls being carried straight down to form the base without additional 
thickness of material. 

Q. What are the advantages of this? 

A. Its simplicity and lighter weight, with greater air space are 
the advantages of the straight-side form. In addition, in the newly 
standardized rim forms, the form of rim adapted to the straight-side 
tire is more simple, lighter in weight, and lower in cost than any other. 
It has been found by experience that the holding power of the beads 
was unnecessary as the inflated tire could not come off the wheel 
whether it had a bead or not, since its diameter at the base could not 
be increased in any possible way sufficiently to pass over the larger 
size rim. 

Q. What is an oversize tire? 

A. In the standardization of tires and rims, for each even tire 
size, which is called a standard, there is an oversize made which will fit 
on the same rim without any other changes. 

Q. What is the difference between standard and oversize tires? 

A. All standard tires are made in even inches of outside diam- 
eter, and all oversize tires are made in odd inches of outside diameter, 
so that the rule for oversizes is this: An oversize is one inch larger in 
diameter and ? inch larger in cross-section, that is, the Ford size 
is 30 by 3 J, the oversize for this, according to the rule, is 31 by 4; an 
average large car size is 36 by 4J, the oversize for this is 37 by 5. 


Q. What are the general different rim forms? 

A. Rims are generally divided into these forms: plain, which is 


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no longer used; clincher, which is gradually going out; quick-detach- 
able in its various forms; and demountable rims, now almost universal. 

Q. What are the differences in these? 

A. The clincher rim is a solid form, and the tire has to be 
stretched to get it on or off the rim. For this reason, it has to be made 
with a more or less yielding base, but even at that, tire removal is 
very difficult. The quick-detachable form is made with a locking 
ring on one side to replace the solid side of the clincher, so that tires 
can be applied easily. The demountable rim is a form which is used 
in combination with the others, this being a modification of the felloe 
of the wheel by which the entire tire and rim are removed in case of 
trouble, and then are replaced by another tire and rim which have 
been carried for this form. 

Q. What are the advantages of this? 

A. All roadside work is eliminated. When a puncture or 
blowout occurs, the driver simply jacks up his wheel, takes off tire 
and rim, and puts on the square tire and rim — the tire being inflated — 
lets down his car by means of the jack and drives off. The worn, or 
damaged tire, is carried at the rear in place of the spare, and is mended 
in the convenience and comfort of the garage or left at a tire repair 
station for that purpose. It saves work, time, and trouble at a time 
when these are of the greatest value to the owner. Given demount- 
able rims, supplied on the car by the manufacturer, the car can be 
operated with all these conveniences without extra tire expense. 

Q. How are demountable rims held in place on the wheels? 

A. Nearly all demountables are held by means of wedges, with 
separate bolts to press these into place, or else a construction in which 
the bolt and wedge are combined. 


Q. What is vulcanization? 

A. Vulcanization is the curing, or cooking, of raw rubber. B.y 
this curing it is more suitable for hard usage and its soft pliable 
character is changed without injuring its resiliency. If these were 
unchanged the tire would cut and would not wear. 

Q. How is this accomplished? 

A. By the application of heat in moderate quantities and in dry 
form. The heat is not applied directly but through metal. In the 


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usual tire-curing mold the central space for the tire is surrounded by 
metal, with a hollow annular space outside of this into which the 
steam, which is generally used, is introduced. The heat from this 
steam penetrates the metal inside and vulcanizes the tire. 

Q. Are all vulcanizers operated by steam? 

A. Practically all the larger ones are, but many of the smaller 
forms of the portable type burn gasoline in the heating space, others 
use electric resistance coils. 
. Q. What is the advantage to the private owner of a vulcanizer? 

A. When a tire is cut badly, he can apply raw rubber as a patch 
or repair, and then vulcanize this for the double purpose of curing 
and of uniting it with the older part of the tire. In this way, tire life 
is much prolonged at little expense. 

Q. Is vulcanization profitable as a business for a repair shop? 

A. It is said to be highly profitable, after suitable equipment 
has been purchased and a trade built up. It is said to be a more 
steady and stable business than any other, for, as soon as an owner has 
been convinced of the value of vulcanization of tubes and casings, he 
will bring in all his tire repairs. 

Q. What is a sand blister? 

A. A small opening in a casing, into which sand has entered and 
continues to enter until the outer surface is swelled up just like a 
blister. If neglected, this will ruin the casing. 

Q. How should a sand blister be cared for? 

A. By the immediate removal of the sand and the cleaning of 
the cavity, after which it should be filled with a tire-repairing cement 
or tire-filling compound. The sand can be removed by cutting a small 
hole in the underside of the blister with a sharp penknife. 


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p* ''■■'■' 


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Importance of Electricity on Automobiles. Starting with 
nothing more than a few dry cells and a wiring system that would 
have shamed an itinerant bellhanger, the electrical equipment of 
the automobile has constantly increased in importance, until within 
the last few years it has become the most essential auxiliary there 
is on the machine. Electricity now starts the motor, ignites the 
charge in the cylinders, lights the car and the road ahead, sounds 
the horn, and in some instances shifts the gears and applies the 
brakes. In addition to performing the numerous functions already 
mentioned, it has even gone as far as to displace the flywheel, clutch, 
and gearset altogether, in which case the car is provided with as 
many gradations of speed as a steam car. It seems quite likely that 
along this line is to be one of the most important developments of 
the next few years. 

Inherent Weakness of Electrical Devices. Even in the present 
highly perfected state, the electrical equipment still constitutes the 
weakest element among the motor auxiliaries. In fact, it is subject 
to more frequent defection than any other single element of the 
entire construction of the automobile. This must not be taken as 
implying that it is defective in any sense, as it is quite the contrary, 
ignition, lighting, and self-starting systems having been developed 
to a degree of reliability that was undreamed of in the earlier days. 
But owing to its nature, the electrical equipment is more susceptible 
to derangement. Consequently, a rather substantial proportion 
of the minor troubles of automobile operation that still survive to 
harass the motorist arise from some failure of the electrical system. 
Of course, many of these are due to the inexperience or ignorance 
of the motorist himself, and for this reason it behooves the student 




to give more than the usual amount of attention and study to this 
branch of the subject. 


Knowledge of Principles Necessary. To acquire a good 
practical working knowledge of electricity as applied to the auto- 
mobile today, it is essential not merely to find out how things are 
done, either by watching the other fellow do them, or by studying 
"pictures in a book", but also to learn why certain things are done 
and why they are carried out in just such a way. In other words, 
the man whose knowledge is based upon theory and principles 
applies knowingly the cause to produce the effect and is certain 
that the desired effect will be produced. On the other hand, the 
man who works only with his hands aimlessly goes from one thing 
to another trusting chiefly to luck to accomplish two things. One 
of these is to strike upon the remedy for the trouble the cause of 
which is sought, and the other is to deceive the spectator — usually 
the owner of the car — into believing that the fumbler really knows 
what he is about. 

There are accordingly two distinct classes of knowledge as 
regards the electrical equipment of an automobile — one which is 
picked up by rote, an isolated point at a time, and applied in the 
same manner, and the other which is based upon a clear insight 
into the underlying reasons for the various actions and reactions 
that make up the different, electrical phenomena involved. If 
we want to know what is wrong with an electric motor, it is essential 
that we should know what makes an electric motor operate when 
everything is right. In the same way, it would be groping in the 
dark to attempt to investigate the reasons for the failure of a dynamo 
to generate current, or a storage battery to give up its charge, 
if we had no knowledge of why a dynamo, when run by an outside 
source of energy, normally produces a current, or why an accumu- 
lator literally "gives back" what has been put into it when its 
circuit is closed after charging. 

It will accordingly be the function of this introductory chapter 
to give a brief r6sum6 of the principles underlying the operation 
of what has come to be the most important auxiliary of the gasoline 
motor as applied to the automobile — its electrical equipment. 


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A thorough understanding of these principles will go a long way 
toward enabling one to remedy the various minor ills that afflict 
the apparatus, and to recognize at once those of a nature serious 
enough to be beyond the first aid which eyen the best equipped 
garage is capable of giving. It is worse than a waste of time to 
hunt for a short circuit or a ground as the cause of failure of the 
dynamo to generate, when an inspection of its parts reveals the 
fact that its armature winding has been burned out. Again, one 
can hardly expect the motor fo continue starting the gasoline engine 
when the owner's neglect of the storage battery has permitted the 
plates to sulphate so badly that they are practically worthless. 
Contempt of "book knowledge'' is not wholly a thing of the past, 
and many men consider themselves "practical" in insisting upon 
learning how to do things with their hands alone. The best-paid 
man, however, and he who can instruct others how things should 
be done, is the man who uses his head to acquire a knowledge of 
the theory upon which practice is based, and then employs his 
hands to much better effect by letting his brain guide them. 


Current. Just what electricity is we do not know — maybe 
we never shall know — but it is a matter of common knowledge that 
it is one of nature's prime forces and as such is universal. The 
air, the earth, the water, the clouds, our bodies and those of animals, 
and other inanimate objects such as trees, houses, and the like 
are all electrified to a greater or less degree all the time. The 
amount of electricity that any given object possesses at a given 
moment depends upon its capacity (the electrical meaning of which 
ist given later) and the conditions of surrounding objects. For 
example, a room will hold a certain amount of air; if it is unin- 
fluenced by other conditions, we know that the room is full of air 
at an approximate atmospheric pressure of 15 pounds to the square 
inch (the usual pressure at sea level). The room may be considered 
in a normal "state of charge". 

There is nothing that differentiates the air in this room from 
that of the room adjoining. It is perfectly quiet and nothing is 
disturbing it; there is no tendency for it to move. If, however, 
all the openings of the room are tightly closed with the exception 


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of a duct for the admission of more air under the impulse of a power- 
ful compressor, in a very short time there will be a marked difference 
between the air in this room and the air in the other rooms. Instead 
of the normal atmospheric pressure of 15 pounds per square inch, 
there will be a pressure against all parts of the room — floor, walls, 
and ceiling — of 50, 60, or 100 pounds, according to the length of 
time the compressor has been working and the degree of tightness 
with which the various openings have been closed. Thus there 
will be a great deal more air in the one room than in its neighbors. 
If it were electricity instead of air, the room would be said to be 
highly charged. 

The air in this room, on account of the pressure which it is 
under, is constantly seeking an outlet, and it will gradually leak 
out through various small openings, probably without its escape 
being noticed. The same conditions obtain when a body becomes 
electrified beyond its capacity to hold a charge — the charge of 
electricity will leak away without giving any indication of its passing. 
Turning again to the room containing the compressed air, if a door 
or window of that room is opened suddenly, the pressure is immedi- 
ately released through that opening and anyone standing in front 
of it would say that a strong current of air blew out. In the case 
of electricity, if any easy path of escape is provided, the entire 
charge will rush away from the body, and there is then said to be 
a current of electricity "flowing" from this point of escape to what- 
ever other object equalizes the pressure by becoming charged. 
An electric current is accordingly electricity in motion; it is simply 
said to flow. But to cause it to do so there must be pressure. The 
electrical term for this pressure is potential or voltage. 

Electrical Pressure, Every day in the year the earth transmits 
a greater or less proportion of its electrical charge to the atmos- 
phere, or receives a charge from the latter, but unless the conditions 
are favoiable there is no visible indication of this difference of 
potential as it is termed. It must be borne in mind that this differ- 
ence of potential, or difference in electrical pressure, between two 
points is what causes a current to flow. Given a hot day in summer, 
however, when the air is heavily charged with moisture and low 
cumuli, or rain-charged clouds form in great masses, then the 
electrical charges from the earth and the air accumulate in these 


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great banks of dense water vapor instead of passing up to the higher 
regions of the atmosphere. When the charge exceeds the capacity 
of the clouds, and the electrical pressure, or difference of potential, 
between two neighboring clouds or between a cloud and the earth 
becomes very great, we have the familiar phenomenon of lightning, 
the electricity escaping in a several-mile-long flash instead of by 
means of the little spark with its snap as it passes from one object 
to another under similar conditions. 

Resistance. It is thus apparent that electricity is an element 
that can be expressed as a quantity, and likewise one that can be 
subjected to pressure. The unit of quantity is the coulomb; the 
unit of electrical pressure is the volt; the unit of current is the 
ampere, equal to one coulomb per second. Resuming the simile 
previously given, 500 cubic feet of air per minute forced into a 
room under 100 pounds pressure may be likened to a current of 
500 amperes at 100 volts. And, just as the opening allowed deter- 
mines the rate at which air will escape, so the electrical outlet 
influences in the same manner the current that will flow. From 
this it is evident that there is another factor to be considered. 
This is resistance. 

If a half-inch hole is bored in the door of the room, the air 
will escape at a pressure of 100 pounds to the square inch, but 
only a few cubic feet per minute can pass through the orifice. If 
a very fine wire is used to tap the given charge of 500 amperes 
at 100 volts, the current will have a potential of 100 volts, but very 
few amperes will pass through the fine wire. If the pressure back 
of the air is increased, however, more air will be forced through 
the small opening in the same time; and if there is a greater potential 
back of the electrical current, more current will be passed through 
the fine wire. Thus the factors of electrical quantity, pressure, 
and flow are all related and are all dependent on the factor of 
resistance. The unit of resistance is the ohm. 

Ohm's Law. From this interrelation has been deduced what 

is known as Ohm's law, usually expressed as 1=^, or current equals 


voltage divided by resistance, E denoting the electromotive force, 
which is only another term for voltage or potential — the electrical 
moving force back of the current I. 



As a practical application of the preceding formula, take the 
case of a small conductor connecting the battery and starting 
motor of the electrical starting system on an automobile. The 
diameter of the wire is such that the length required to connect 
the two points has a resistance of 10 ohms. One ampere is that 
amount of current which will pass through a conductor having 
a resistance of one ohm under a pressure of one volt. The starting 
system in question operates at 6 volts. Hence, J=iV = .6, that 
is, the battery would be able to force only .6 ampere through that 
small wire, and the starting motor would not operate. 

It is apparent from the foregoing that the formula for Ohm's 
law may be transposed to find any one of the three factors that 
may be unknown. For example, given the conditions just men- 
tioned, we may determine how much resistance the wire in question 
has. The resistance equals the voltage divided by the current: 

that is, R = —,ot resistance equals — = 10 ohms. Or again, if it is 
i .6 

desired to learn what voltage is necessary to send a current of .6 

ampere through a resistance of 10 ohms, the solution calls for an 

equally simple transposition of the formula. Given any two factors, 

then the third may be readily determined. 

Ohm's law is absolutely fundamental in all things pertaining 
to electrical operation, and the man who wants to make his knowledge 
of the greatest practical use will do well to familiarize himself with 
it. Naturally it does not enter into repair work to more than a 
small fraction of the extent that it enters into the design of motors, 
generators, and other electrical devices, but a knowledge of it is 
of distinct value. 

Power Unit. To go back to the simile of air under pressure, 
it is apparent that the energy released by the lowering of this 
pressure may be made to perform useful work, such as driving a 
compressed-air drill, running a small air motor, or the like. So 
with the electric circuit, the drop from a higher to a lower potential, 
which causes a current to flow, is a source of power. Electrical 
power is the product of the amperage or current multiplied by the 
voltage at which it is applied. The power unit is the watt and it 
is equivalent to one ampere of current flowing under a pressure, 
or potential, of one volt. There are 746 watts in a horsepower. 


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Electrical computations, however, are based on the metric system 
to a large extent, so that instead of being figured in horsepower, 
electrical energy is figured by the kilowatt, or a unit containing 
one thousand watts, and the charge therefor is based upon the length 
of time for which this amount of energy is employed. From this 
comes the now familiar expression "kilowatt-hour". 

The power equivalent is expressed as P = IXE, current multi- 
plied by electromotive force (potential), and, as in the case of Ohm's 
law, with any two of the factors given, the third may be readily 
determined. For example: How much power is developed by 
a 3-volt starting motor if 125 amperes of current are necessary 
to turn the automobile engine over fast enough to start it? The 
amount of current given is an arbitrary average taken simply fo* 
the purpose of illustration, for in overcoming the inertia of an 
automobile engine a great deal of current is required at first, the 
drain on the battery often exceeding 250 amperes for a few seconds, 
then dropping as the engine turns over to about 50 or 60 amperes. 
Taking 125 as the average, we have 125X6 = 750 watts = .75 kilo- 
watt, or slightly over one horsepower. 

Granting that one horsepower is necessary to turn over a 

3| by 4-inch six-cylinder motor at 75 r.p.m. — a speed that has been 

predetermined as necessary to .cause it to take up its own cycle 

under the most adverse starting conditions — and given a 6-cell 

storage battery capable of developing a potential of 12 volts, then 

P 746 

we have : J = — , or current = — = 62.1 + amperes, which represent 

the average demand upon the storage battery to start that engine 
under normal conditions. This illustration and the previous one 
show the working of Ohm's law; doubling the voltage halves the 
amount of current necessary. As the life of a storage battery is 
largely determined by the rapidity as well as by the number of 
its discharges, and as the storage battery is the weakest element 
in any electric lighting-and-starting system, it may well be asked 
why the 12-volt standard is not universally adopted, or why, as 
is done in some cases, a 24-volt battery is not employed and the 
current consumption again reduced by half. Just why this is not 
done is explained in detail in the section on the voltages employed 
in electric starters generally. 


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Conductors. To lead steam or air under pressure from a 
boiler or compressed-air reservoir to the point at which it is to be 
utilized as energy, it is desirable to use a conductor that will not 
waste too much of this energy in useless friction. That is, the 
conductor must be of ample size in proportion to the volume to 
be conveyed, smooth in bore, and free from sharp turns or bends. 
The transmission of electrical energy involves some of the same 
factors. While neither the smoothness of the bore nor the presence 
of bends and turns has any effect, they have their counterpart 
in the conductivity of the material of which the wire is made, the 
size of the wire in proportion to the amount of current to be carried 
being also a matter of prime importance. 

Resistance of Materials. Materials differ greatly in their 
ability to conduct an electric current, or, to put it the other way 
around, they differ in the amount of resistance that they offer to 
the passage of the current. Silver in its pure state heads the list 
in the table of relative conductivities, and it is accordingly said 
to possess a relative resistance of one, or unity; the resistance of 
every other material may be expressed by a number which repre- 
sents the resistance of that particular substance as compared with 
pure silver. Naturally silver does not represent a great possibility 
for commercial use, and so copper, which is second on the list, is 
almost universally employed. Pure copper is very soft and is 
lacking in tensile strength; it is therefore alloyed, and it is also 
hardened in the drawing process; both of these processes increase 
its resistance slightly over the factor usually accorded it in the 
standard table of specific conductivities of materials. In this 
table, German silver (which is an alloy containing no silver whatever 
and having but a few of its properties), cast iron, steel, carbon, 
and similar substances will be found well down toward the end. 
They are known as "high-resistance" conductors and are usually 
used where a certain amount of resistance to the current is desirable. 

It must be borne in mind that ability to conduct a given amount 
of current without undue loss through resistance depends upon 
the size and the length of the conductor quite as much as upon 
the material. In other words, if a steel rail is only one-thirtieth 
as good a conductor as a copper cable, it will require a cross-section 
of steel thirty times as great as that of a copper cable in order to 

358 ■ 

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conduct the current with the same ease — that is, to make a con- 
ductor of equal resistance. An illustration of this may be seen 
in the overhead copper wire of the usual trolley system. This 
wire of about one-half inch diameter forms one of the conductors, 
while the two steel rails form the "return". A similar example 
may be found in what is known as the single-wire system of installa- 
tion for an electric starter in automobiles. A single copper cable 
conducts the current from the battery to the starting motor, while 
the steel frame of the automobile is the return side of the circuit, 
or vice versa. 

Voltage Drop. It is evident that the resistance of a circuit 
varies inversely as the size of the conductor — the larger the cross- 
section of a conductor, the less its resistance — and increases directly 
as its length, besides depending upon the specific resistance of the 
material. The specific resistance of the metals constituting elec- 
trical circuits on the automobile are (silver being 1.0); copper 
1.13, varying more or less with its hardness; aluminum 2.0; soft 
iron 7.40; and hard steel 21.0. Thus, 9.35 feet of No. 30 copper 
wire are required for a resistance of one ohm, while only 5.9 inches 
of hard steel wire of the same gage are required to present the same 
amount of resistance to the current. If the length of the conductor 
is doubled, its resistance is doubled, which accounts for the placing 
of the storage battery as close as possible to the starting motor. 
Furthermore, the heavy starting currents which are required by 
the motor demand the use of heavy copper cable for this circuit. 
If two wires are of the same length but one has a cross-section 
three times that of the other, the resistance of the former is but 
one-third that of the latter. If a circuit is made up of several 
different materials of different sizes joined in series with one 
another, the total resistance will be the sum of the resistance of 
the various parts. 

In addition to being affected by the cross-section and the length, 
the resistance is also influenced by the temperature. All metals 
increase in resistance with an increase in temperature, that of copper 
increasing approximately .22 per cent per degree Fahrenheit. The 
change of resistance of one ohm per degree change in temperature 
for a substance is termed its temperature coefficient. Metals have 
a positive temperature coefficient; some materials, like carbon, 



have a negative temperature coefficient, that is, they decrease 
in resistance with an increase in temperature. 

It is consequently necessary to employ wires of proper size 
to carry the amount of current required by the apparatus in circuit 
— such as lamps — without undue heating, which would cut down 
the amount of current flowing. For the same reason it is also 
desirable to make the circuits as short as practicable, since in addition 
to cutting down the current, the resistance also cuts down the 
effective voltage. That is, there is a fall of potential, or drop in 
voltage, between the source of current supply and the apparatus 
utilizing it, due to the resistance of the conductors between them. 
This voltage drop is further increased by joints in the wiring and 
by switches. It is apparent that the lower the voltage of the source 
of supply, the more important it becomes to minimize the loss, 
or voltage drop, in the various circuits. For this reason lighting 
or other circuits on the automobile should never be lengthened 
where avoidable. When necessary to extend a circuit for any 
reason, wire of the same diameter and character of insulation as 
that forming the original circuit must be employed, and the joints 
should be as few as possible, all mechanically tight, and well soldered. 
The voltages employed in the electrical systems of automobiles 
are so low — varying from 6 to 24 volts, with a strong tendency 
to standardize the 6-volt system — that any increased resistance 
is likely to cause unsatisfactory operation. 

Non-Conductors. In going down through a table of specific 
conductivities of various materials, the vanishing point is reached 
with those that cease to be conductors at all. Such materials 
are known as nonconductors or insulators, and some substances 
vary in the degree of insulation they afford quite as much as other 
materials do in their ability to conduct a current. Glass, rubber, 
shellac, oil, paraffin wax, wood, and fabrics are all good insulators 
when perfectly dry. Distilled water has such a high resistance 
as to be almost an insulator, but in its natural state water contains 
alkaline salts or other impurities that make it a conductor. Con- 
sequently, when any otherwise good insulating substance is wet, 
the current is likely to leak across the wet surface of the insulator. 
This is particularly the case with a current of high potential, or 
high tension, and explains why it is of the greatest importance 


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to keep all parts of the secondary side of the ignition system perfectly 
dry. The potential which causes the current to arc across the gap 
of the spark plug is so high that it will leak across even slightly 
damp surfaces, such as the porcelains of the plugs. This leakage 
is often visible, especially in the dark, and it may also be detected 
by placing the bare hand on the porcelain. 

Just as the amount of current to be carried determines the 
size of the conductor to be employed, so the potential or pressure 
under which this curfent is transmitted determines the amount of 
insulation that will be necessary. The latter is also affected, how- 
ever, by mechanical reasons, for example, by the liability of the 
conductor to chafing or abrasion. The best grades of copper 
cable employed for both ignition and starting-lighting systems on 
automobiles today are stranded, that is, composed of a number 
of fine wires, to make them flexible. The stranded cable is then 
tinned to prevent corrosion due to the sulphur in the insulation, 
after which it is covered with a soft-rubber compound of a thickness 
dependent upon the purpose for which the wire is intended. For high- 
tension ignition wire this rubber covering is about three-sixteenth inch 
thick. This covering is vulcanized and is then further protected by 
braided linen, or silk-cotton thread which is made waterproof by 
being impregnated with shellac or some other insulating compound. 

Circuits. When air under high pressure escapes from its 
container, it simply mingles with the atmosphere, and as soon as 
the difference in pressure is^equalized there is no distinction between 
it and air in general. But to equalize a difference in potential 
of an electric current there must be a conducting path between 
the points of high and low potential. This is termed a circuit. 
Current to operate trolley cars is fed to the motors of the car from 
the overhead wire and returns through the tracks to the generators 
at the power house. This is known as a ground-return circuit. 
In the single-wire electric starting system of an automobile, current 
from the storage battery reaches the starting motor through the 
starting switch and a single heavy cable, and returns through the 
frame and other metal parts of the car itself, or vice versa. This 
is another instance of a ground-return circuit. 

Both the primary and secondary sides of the ignition system 
of an automobile are also grounded circuits. In contrast with 





this, the circuit may be composed of copper cables directly con- 
necting both poles of the battery and switch with the starting 
motor. The highly insulated cable employed for both ignition 
and starting systems is expensive and the use of a single wire greatly 
simplifies the connections, considerations which account for the 
general use of this type of circuit. A circuit is said to be open when 
there is a break in it which prevents the current from flowing, as 

Starting Motor 

2 p p 

d d 







(5**"** 1 



Toil light 


O \P P 

<®+ (b) 



Fig. 1. Typical Starting-Lighting Wiring Diagrams, (a) Series Circuit of 
Starting Motor; (b) Multiple Circuit of Lamps 

when the switch is opened, or when a connection or the wire itself 
is broken. 

Series Circuit. The connections between a storage battery, 
switch, and starting motor, comprise the simplest form of circuit, 
in which the motor is said to be in series with the battery, and x 
the cells of the battery are in series with one another. This is 
termed a series circuit and a break in it at any point opens the 
entire circuit. The starting motor, Fig. 1 (a), requires the entire 
output of the storage battery for its operation. 


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To make clear the distinction between this and other forms 
of circuit, it must be borne in mind that, in equalizing a potential 
difference, electric current flows from the positive or plus side 
of the source of supply, whether a battery or generator, to the negative 
or minus side (plus and minus being arbitrary signs employed to 
distinguish the positive and negative sides of a circuit or of an 
instrument). The current is said to flow out on the positive side 
of the circuit and to return on the negative side. In the case of a 
series circuit as described, the current flows through each piece 
of apparatus in turn; each receives all the current in the circuit 
at a potential proportioned to the resistance of the apparatus in 
question. For example, in the simple starter circuit referred to 
above the starting motor receives the entire output of the 3-cell 
storage battery at its full voltage of 6 volts, less the drop in voltage 
due to the resistance of the circuit. If there were two starting 
motors instead of one in the circuit, both in series, both would 
receive all the current but at only half the voltage. 

Multiple or Shunt Circuit As opposed to this, in a multiple 
circuit, Fig. 1 (b), in which every piece of apparatus is connected to 
both sides of the circuit "in parallel", each piece of apparatus in 
the circuit receives current at the same voltage but draws from 
the circuit the current determined by its resistance. The failure or 
withdrawal of any one or more instruments in a multiple or parallel 
circuit has no effect on those remaining. The lighting circuits 
of an automobile equipped with a 6-volt starting system are an 
example of this. Each lamp is designed to burn to its maximum 
illumination at 6 volts, but the 25-candle-power headlights take 
more current than the 6-candle-power side lights or the 2-candle- 
power taillight, owing to the difference in the size and resistance of 
their filaments. Removing any one of the bulbs has no effect on 
any of the others, because all are in parallel. 

Series-Multiple Circuit. A combination of the two forms of 
circuits is sometimes necessary to accommodate different devices 
designed for varying voltages. For example, it is usually found 
expedient to burn 6-volt lamps on the 12-volt starting systems. 
In such a case, the starting motor is in series with the battery and 
receives the full voltage as well as the full current. The lamps are 
divided into two groups, each group comprising a parallel or mul- 


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tiple circuit of its own, and these two groups are connected in series 
so that the lamps in each circuit receive 6 volts, but the circuit 
as a whole takes the battery current at 12 volts. Such a combination 

Fig. 2. Dry Cells in Series-Multiple for Ignition Circuit 

is known as a series-parallel or series-multiple circuit and is more 
or less commonly used for connecting dry cells for ignition use, 
Fig. 2. 

Circuits may also be in parallel, that is, practically a 
circuit on a circuit. The method of connecting up the voltmeter 
that is mounted on the dash of the car is an instance of this, a wire 
being led from each side of the main circuit to the instrument. 
The instrument is then said to be in shunt, Fig. 3, and the amount 
of current that is diverted to it is entirely dependent on the 
resistance. As a voltmeter is wound to a high resistance, Fig. 4, 
it is designed to take very little current for its operation. The 


y . 






Fig. 3. Diagram Showing How Voltmeter Is 
Shunted in the Circuit 

ammeter, Fig. 5, on the other hand, is intended to indicate the entire 
current output of the generator on charge or discharge, and is 
accordingly connected in series so that all the current passes through 



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Diagram of Voltmeter Principle 

it. (Owing to the heavy rush of current taken by a starting motor 
in overcoming the inertia of the gasoline engine, the t ammeter is 
not included in this circuit.) 
Short-Circuits and 
Grounds. The previous par- 
agraphs have made clear the 
necessity for having a com- 
plete path or circuit for the 
current in order that its power 
may be utilized. There must 
be a connecting cable on one 
side and there must be a re- 
turn on the other (grounded 
circuit). If instead of pass- 
ing through the apparatus, 
such as the starting motor, 
the current finds an easier 
path through an abrasion in 
the insulation of the cable 
and some metal part against 
which that touches, it is 
said to be short-circuited. A 
case such as that cited, 
where a stripped cable 
touches a metal part, so 
that the current completes 
the circuit without passing 
through the motor, is 
usually termed a ground. 
This should not be confused 
with the ground return pre- 
viously mentioned as a 
characteristic of the wiring 
of many of the starting and 
lighting systems in use on 
automobiles today. It is indeed a ground return but not an 
intentional one. It is also true that a ground of this type is 
a short circuit, but it does not necessarily follow from this that 

Fig. 5. 


Diagram of Ammeter Principle 


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all short circuits are grounds, as short circuits may occur from 
many other causes — for instance, where two wires touch at unin- 
sulated points or where stray metal makes contact with connec- 
tions, etc. 

Size of Conductors. The influence of the factor of resistance 
makes plain the reason for using wires of different sizes for the various 
circuits of the ignition starting and lighting systems of the auto- 
mobile. If an ample flow of compressed air is desired for power 
purposes, a liberal outlet must be provided, while if only a small 
spray is required, as for cleaning purposes, a small-bore tube will 
suffice. If we try to employ the small-tube line for power pur- 
poses, we shall not gain the desired result because its resistance is 
so great that it will not permit a sufficient flow of air. For the 
same reason a conductor of much larger diameter and, therefore, of 
correspondingly low resistance must be employed to handle the 
heavy current necessary to operate the electric starting motor, than 
is needed for the comparatively small current which is demanded by 
the ignition system. 

Whether it is mechanical or electrical in its nature, the power 
necessary to overcome resistance is liberated in the form of heat. 
Mechanical resistance is friction and its presence between moving 
bodies always generates heat. Electrical resistance may, for the 
purpose of illustration, be termed internal or molecular friction, 
and it also results in heat. The extent of the rise in temperature 
of a conductor or wire, depends entirely upon the proportion that 
its size and, consequently, its current-carrying ability bear to the 
amount of current that is sent, through it. Roughly speaking, if 
a wire is three-fourths the size it should be to carry the starting 
current, it will become uncomfortably warm to the hand after the 
motor has been operated several times in succession. If it is only 
one-half the size it should be, continuous operation of the starting 
motor for a few minutes will doubtless burn off most of the insulation. 
Further reducing its size would cause the wire to become so hot 
as to set fire to the insulation the moment the current was turned 
on, and any great decrease in diameter would result in the immediate 
fusing of the wire itself. The wire would literally "burn up" and 
in a flash. 

It would not be practical to attempt to conduct live steam 


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American Wire Qage (B. & S.) 


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at high pressure through a cardboard tube. Nor is it any more 
so to attempt to send a heavy current through "any old piece of 
wire". Electric lighting and starting systems as they exist on cars 
today are of all degrees of merit. The cars themselves have reached 
a stage of reliability where their useful life is now on the average 
from five to ten years or more. Consequently, there are a great 
many cars in service equipped with electric systems that were 
brought out several years ago. These are the cars on which the 
repair man will get a great deal of his early experience, and he 
need not take it for granted that just because the electric systems 
have worked for a certain length of time they were properly designed 
at the outset. Overheated conductors not only indicate excessive 
resistance caused by small wires or poor joints, but they also indicate 
a waste of power that is being drawn from the battery and dissi- 
pated in the air. The utilization of this energy or rather the 
prevention of its transformation into heat would mean all the 
difference between poor and good operation between an efficient 
and a wasteful system. 


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Heating Effect of Current. The amount of heat that a given 
current will produce in passing through a conductor of a certain 
size is expressed by Joule's law: The number of heat units developed 
in a conductor is proportionate to its resistance, to the square of the 
current, and to the time that the current lasts. 

The heat generated, therefore, increases in direct proportion to 
the resistance. For example, if the cable between the starting 
motor and the battery be replaced by one-half its size, the resistance 
will be doubled and the heat generated will increase in the same pro- 
portion, the current remaining the same in both instances. Increasing 
the current, however, adds to the amount of heat generated, as the 
square of the increase. Thus, if with the original starting cable above 
mentioned, the amount of current necessary to start the motor has 
to be doubled, owing to gummed lubricating oil or stiff bearings, the 
volume of heat generated will increase fourfold. The amount of 
heat generated also increases in direct proportion to the time that 
the current lasts. It will be easy to realize from this why abnormal 
conditions may quickly bring the heating effect of the current to a 
point where the insulation of the wires, or even the wires themselves, 
may be endangered. For instance, in the case of a motor that is 
very hard to start, the discharge from the battery is greatly increased 
in turning it over, and the starting motor must be operated for a very 
much longer period to get the engine under way, causing a direct 
increase in the heating effect, due to the longer time that the current 
is passing through the cable, and a fourfold increase for the addi- 
tional current necessary. 

Heat Generated in Starting Motor. Take the case of a motor 
that requires 150 amperes for the first few seconds and 50 amperes 
once the engine is turning over freely. If stiff bearings or gummed 
oil cause the initial current to rise to 200 amperes and the running 
current to 80 amperes for a period three times as long as would ordi- 
narily be required to start, there will be a very considerable increase 
in the number of heat units generated. This is one of the reasons why 
it is good practice to use the starting motor intermittently when the 
engine does not at once fire and take up its own cycle, instead of 
running the starting motor continuously until the engine begins to 
fire and generate its own power. A much more important reason, 
however, is the fact that the intermittent use of the starting motor 


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is not nearly so hard on the battery, as the storage battery recu- 
perates very quickly when given short periods of rest between the 
demands for its power. Running the starting motor for ten periods 
of 30 seconds each, with a like interval between the attempts to start, 
will not discharge the battery anything like as much as will operating 
the starting motor continuously for five minutes. A longer rest 
between trials will be of greater benefit to the battery. 

Heating Effect on Lamps and Fuses. It must not be concluded 
from the above that the heating effect of the current is always detri- 
mental, as it is taken advantage of in many ways. Two of the com- 
monest of these are the incandescent lamp and the fuse. In the case 
of the former, the increase in heat with an increase in resistance is 
mainly depended upon, the filament being made of such a size that 
a given amount of current at a certain voltage will just bring it to 
incandescence. For this reason an increase in tlie current, or voltage, 
will burn the filament and destroy the lamp. The fact that the 
heating effect increases as the square of the current is taken advantage 
of in the design of fuses which are made of soft alloys that will melt 
at comparatively low temperatures. Resistance is also a factor in the 
fuse, as in cutting down the cross-section of the fusible wire the resist- 
ance is increased, while the current-carrying capacity of the wire is 
decreased. The cross-section, or diameter, of the fuse is gaged to 
carry the amount of current that is a safe load for the circuit and 
the apparatus in it plus a reasonable factor of safety to prevent 
the fuse from burning out, with a small percentage of increase that 
would do no damage. For example, a 10-ampere fuse, such as is 
used in connection with many automobile-lighting generators, would 
seldom burn out with an increase in the current to 12 amperes or 
even to 15 amperes for short periods, as the time element is also 
important. Some other applications of the heating effect are electric 
welding, blasting fuses, soldering coppers, cooking utensils, and the like. 

Chemical Effect of Current. The passage of an electric current 
likewise has a chemical effect depending upon the nature of the con- 
ductor. This may take various forms, such as the conversion of one 
chemical compound into another, as in the case of the storage battery; 
the decomposition of water into hydrogen and oxygen; the deposition 
of metals, as in electroplating; or the decomposition of metals, as 
in electrolysis. 


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Carrying Capacity of Wires 





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Natural and Artificial Magnets. It has been known for many 
centuries that some specimens of the ore known as magnetite (Fe 3 4 ) 

have the property of attracting small bits 
of iron and steel, Fig. 6. This ore proba- 
bly received its name from the fact that it 
is abundant in the province of Magnesia 
in Thessaly, although the Latin writer 
Pliny says that the word magnet is de- 
rived from the name of the Greek shep- 
herd Magnes, who, on the top of Mount 
Ida, observed the attraction of a large 
stone for his iron crook. Pieces of ore 
which exhibit this attractive property 
for iron or steel are known as natural 

It was also known to the ancients. 

that artificial magnets could be made by 

stroking pieces of steel with natural mag- 

LodeJtone agne or nets, but it was not until the twelfth 

fig. 6. 


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Fig. 7. Bar Magnet 

century that the discovery was made that a suspended magnet 
would assume a north-and-south position. Because of this prop- 
erty, natural magnets came to be known as lodestones (leading 
atones) ; and magnets, either arti- 
ficial or natural, began to be 
used for determining directions. 
The first mention of the use of 
a compass in Europe was in 1190. It is thought to have been 
Introduced from China. 

Artificial magnets are now 
made either by repeatedly strok- 
ing a bar of steel, first from the 
middle to one extremity with 

One Of the ends, Or poles, Of a Fig 8> Horseshoe Magnet 

magnet, and then from the mid- 
dle to the other extremity with the other pole; or else by passing 
electric currents about the bar in a manner to be described later. 
The form shown in Fig. 7 is called a 
bar magnet, that shown in Fig. 8 is a 
horseshoe magnet. 

Poles of a Magnet. If a magnet 
is dipped into iron filings, the filings 
are observed to cling in tufts near the 
ends, but scarcely at all near the mid- 
dle, Fig. 9. These places near the 
ends of the magnet, in which its 
strength seems to be concentrated, 
are called the poles of the magnet. 
It has been decided to call the end 
of a freely suspended magnet which 
points to the north, the north-seek- 
ing, or north pole, and it is commonly 
designated by the letter N. The other 
end is called the south-seeking, or 
south pole, and is designated by the letter S. 
which the compass needle points is called the magnetic meridian. 

Laws of Magnetic Attraction and Repulsion. In the experiment 
with the iron filings no particular difference was observed between 

Fig. 9. 

Location" of Poles of a 

The direction in 


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the action of the two poles. That there is a difference, however, 
may be shown by experimenting with two magnets, either of which 
may be suspended, Fig. 10. If two N poles are brought near each 
other, each is found to repel the other. The S poles likewise are 
found to act in the same way. But the N pole of one magnet is 
found to be attracted by the S pole of the other. The results of 
these experiments may be summarized in the general law: Magnet 
poles of like kind repel each other, while poles of unlike kind attract. 
This force of attraction or repulsion between poles is found, 
like gravitation, to vary inversely as the square of the distance 
between the poles; that is, separating two poles to twice their original 
distance reduces the force acting between them to one-fourth its 

original value, and separating them three 
times their original distance reduces the 
force to one-ninth its original value, etc. 
Magnetic Substances. Iron and 
steel are the only common substances 
which exhibit magnetic properties to a 
marked degree. Nickel and cobalt, how- 
ever, are also attracted appreciably by 
strong magnets. Bismuth, antimony, 
and a number of other substances are 
actually repelled instead of attracted, 
but the repulsion is very small. Until 
quite recently, iron and steel were the 
only substances whose magnetic prop- 
erties were sufficiently strong to make 
them of any value as magnets. Recently, however, it has been 
discovered that it is possible to make rather strongly magnetic 
alloys out of non-magnetic materials. For example, a mixture of 
65 per cent copper, 27 per cent manganese, and 8 per cent aluminum 
is rather strongly magnetic. These are known as the Heussler alloys. 
Electromagnets. The identity* of magnetism with electricity 
is readily established by some very simple experiments that have 
been repeated so often as to become classics. By taking a bar of 
iron and winding some insulated wire around it in the form of a 
coil and then connecting th£ terminals of this coil with a battery 
or other source of current, the bar becomes magnetic. One end 

Fig. 10. Experiment Proving the 

Law of Magnetic Attraction 

and Repulsion 


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of it is the positive, plus, or north pole of the magnet, and the other 
the negative, minus, or south pole. Break the connections or 
otherwise "open the circuit" and the magnetism instantly dis- 
appears. Reverse the connections to the battery by attaching 
the wire previously at the positive pole to the negative, and vice 
versa, complete the circuit again, and the bar is once more magnetic, 
but now the pole that was previously north or positive is south. 
The bar is once more a magnet, but its polarity has been reversed 
by reversing the direction of flow of the magnetizing current. This 
bar of iron with a coil of wire wound around it is known as an electro- 
magnet because it becomes magnetic only when a current is passing 
through the coil. If a rod of hard steel is substituted for the bar 
of soft iron and the current passed through it, the bar will be found 
to be strongly magnetic after the current has been shut off. That 
is, the bar of steel has, through the action of the current, become 
a permanent magnet like that shown in Fig. 7. This method is 
often used for making permanent magnets from hardened steel. 

To determine the polarity of a magnet it is only necessarj 
to hold a small pocket compass near it; let the compass needle 
come to rest normally and then bring the compass near to one 
end of the magnet. If the needle continues to point in the same 
direction and gives evidences of being strongly attracted to the 
magnet, the end to which it is being held is the south pole. Bring 
the compass near to the other end of the magnet, and the needle 
will turn away sharply, showing that like poles repel each other. 

Magnetic Field. If a bar magnet is placed on a sheet of glass 
and a handful of fine iron filings thrown around it, they will auto- 
matically assume the position shown by Fig. 11. As originally 
dropped on the glass some of the filings may not be within reach 
of the influence of the magnet, but if the glass be gently tapped 
and tilted slightly, first one way and then another, they will arrange 
themselves in the symmetrical pattern shown. This gives a graphic 
illustration of the field of influence of the magnet, usually termed 
the magnetic field. This field is most powerful at the poles,* as 
will be noted by the attraction of the filings at the N and S points, 
representing the north and south poles of the magnet. At inter- 
mediate points along the length of the magnet the filings will be 
seen to have placed themselves as if to indicate a circular movement 





of the lines of force. This is the magnetic circuit and these concentric 
circles represent the magnetic flux, or flow. If the magnet is then 
removed from the glass and the north pole extension of it placed 

Fig. 11. 

Field of Force about a Bar 

Fig. 12. Field of Force about a Single 

centrally under the glass, a striking illustration is given of the 
magnetic field around the pole, Fig. 12. A bar magnet has been 
shown here for purposes of simplicity, but a common horseshoe 
magnet such as can be had for a few cents will serve equally well 
for the experiments. 

By carrying the experiments a little further, the identity of 
magnetism and electricity is strikingly shown. Take a piece of 

Fig. 13. 

Field about a Conductor Carrying a Current 

cardboard or heavy paper, punch a hole through its center and 
pass through this hole a wire connected to two or three dry cells. 
Scatter on the paper the filings used in the previous experiments, 


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then complete the circuit by touching the end of the wire to the 
other terminal of the battery. The filings will immediately arrange 
themselves as shown in Fig. 13, illustrating the magnetic field 
which is always present around any current-carrying conductor. 

Lines of Magnetic Force. Punch another hole through the 
cardboard and rearrange the circuit of the dry cells so that the wire 
passes from the positive battery terminal up through one hole 
of the cardboard and down through the other hole to the zinc or 
negative. Scatter the filings as before and touch the loose end 
of the wire to the negative terminal. The arrangement of the 
filings will then be that shown in Fig. 14, the positive field being 
at the left and the negative at the right. The fact that the mag- 
netic fields overlap in the curious 
alignment indicated is simply 
due to the proximity of the con- 
ductors carrying the current. 

Another simple method of 
demonstrating the identity of 
electricity and magnetism is to 
place an ordinary pocket com- 
pass above or below a wire which 
is running north and south and is 

carrying a current. If this is a Fig. u. Field about a CoU 

direct current the needle of the 

compass will tend to set its axis at right angles to the wire, that 
is parallel to the lines of force; the direction of the deflection will 
depend upon the direction of the current. This test, therefore, 
not only indicates the magnetic field about the wire bearing a current, 
but shows its direction. 

All of the Arrangements whidi the filings assume under the 
influence of either a magnet or a current, as shown by the various 
llustrations, indicate that the stresses in the medium surrounding 
a magnet or current-carrying conductor follow certain definite 
lines, the lines showing the direction of stress at any point. These 
are termed lines of force. 

Solenoids. It has been determined that the direction of the 
current and that of the resulting magnetic force are related to one 
another as the rotation and travel of an ordinary, or right-hand, 





Fig. 15. Direction of Magnetic Lines about a 

screw thread. Consequently, if the conductor be looped instead 
of straight, the lines of magnetic force will surround it as shown 
in Fig. 15. The field of such a loop, if outlined with the aid of 
filings or explored with a compass needle, will be seen to retain 

the general character of 
the field surrounding a 
straight conductor, so 
that all the lines will 
leave by one face and 
return by the other, the 
entire number passing 
through the loop. Hence one face of the loop will be equivalent 
to the north pole of a magnet and the other face to the south 
pole. In fact, the loop will act exactly as if it were a thin disk 
magnetized perpendicularly to the plane. By winding a number 
of these loops to make a hollow coil, there is formed a solenoid, 
Fig. 16. Exploring its field shows that the lines of force pass 
directly through the center or opening of the hollow coil, leaving 
by one end and returning by the opposite end, as indicated. 

If such a solenoid is held vertically and a bar of soft iron placed 
so that it extends for an inch or so into the lower end of the solenoicj, 
a current passed through the latter will cause the iron to be violently 
drawn up into the coil and held there. As long as the current 
flows, this rod is strongly magnetic and has all the properties already 

_ — _.^_ ^ described. Butthemo- 

^-*~"' w _ ~^-^ ment the current is shut 

off, the magnetism prac- 
tically disappears and 
the rod immediately 
drops out of the coil by 
its own weight. Re- 
versing the direction of 
the current reverses the 
polarity of the solenoid 
but makes the effect the same; increasing or decreasing the amount 
of current sent through it increases or decreases correspondingly the 
strength of its magnetic field. The principle of the solenoid is used 
m starting systems to operate electromagnetic starting switches- 

Fig. 16. Magnetic Field about a Solenoid 


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Effect of Iron Core on Strength of Solenoid. The magnetic 
flux or flow of lines of force through a solenoid is much greater 
when an iron core is present than when the coil is empty or a core 
of wood is inserted. The magnetism flows through the iron as a 
current would. Soft iron is said to have a high magnetic permea- 
bility. The magnetic permeability of air (or a vacuum) is taken 
as unity and other substances rated accordingly: for very soft iron 
it may be as high as 2500, while for substances such as silk, cotton, 
wood, glass, brass, copper, and lead, it is unity, the same as for air. 
Such metals are said to be non-magnetic. All insulators are 
likewise non-magnetic. 


Induction. When a current suddenly flows in a wire place J 
close to another wire, a delicate measuring instrument such as a 
galvanometer will indicate a momentary current in the second wire. 
When the current in the first wire ceases, that in the second will 
likewise cease immediately. This phenomenon is known as induc- 
tion, and a current is said to have been induced in the second wire. 

Winding the first wire in the form of a coil and bringing this 
coil close to the second wire, will give the induced current con- 
siderably greater strength. The induced effect is still further 
increased in three other ways: first, by inserting an iron core in the 
coil; second, by winding the second wire in the form of a coil; and, 
third, by bringing these coils as close together as possible by winding 
one directly over the other. 

Transformer Principle. The arrangement just discussed is 
termed an induction coil or transformer (step-up) and is universally 
employed in connection with ignition systems. The character 
of the induced current depends upon the relation that the first 
coil, termed the primary, bears to the second coil, known as the 
secondary. In the usual ignition coil the primary consists of a 
few turns of comparatively heavy wire, and a current of about 
2 amperes (4 to 5 on starting) is sent through it at a low voltage, one 
seldom exceeding 6 volts. The secondary coil, however, consists 
of a great number of turns of exceedingly fine wire, and the current 
induced in this is proportional to the relative number of turns 
between the two and the value of the current in the primary. The 


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secondary current is accordingly of extremely high potential but 
of low current value. 

In the commercial step-down transformer, the relations described 
above are reversed, the primary being a coil of many turns of fine 
wire, while the secondary is a comparatively small coil of few turns. 
In this case, the current is received at the transformer at high 
voltage and correspondingly reduced amperage, and it steps the 
voltage down to the standard generally employed, 110 or 220 volts, 
and increases the amount of current proportionately. 

Self-induction. It has already been pointed out that electricity 
may be put under pressure or potential, and that the greater this 
pressure, the greater the amount of work a certain amperage of 
current will perform, thus affording a direct analogy with steam, 
water, or air under pressure. An electric current also possesses 
other characteristics corresponding to mechanical equivalents. 
Chief among these is inertia and it is the latter that is responsible 
for what is known as self-induction. 

When a current is passed through a coil of wire, a strong magnetic 
field is set up in the coil owing to the concentration of a great many 
turns of wire in a small compass. By inserting a core of soft iron 
wires into this coil, the magnetic field is greatly strengthened, since 
the permeability of the iron affords a path of slight resistance for 
the magnetic circuit. There is, of course, a magnetic field sur- 
rounding every conductor in a circuit when the current is passing, 
but the iron core of the solenoid converts a certain part of this 
current into magnetism. An appreciable time is necessary after 
the circuit is closed for such a coil "to build up". This "building 
up" consists of saturating the core with magnetism. 

When the circuit is suddenly opened, the current that has been 
stored in this core in the form of magnetism is as quickly retrans- 
formed and its value is impressed upon the circuit, causing a flash 
at the break. The flash is also aggravated by a certain amount 
of inertia which the current possesses. We may illustrate this 
by a stream of water flowing in a pipe. If the water is suddenly 
shut off by the closing of a valve, it tends to keep on flowing and 
momentarily causes a great increase in the pressure against the 
face of the valve, resulting in the familiar "water hammer". The 
same thing happens when a circuit is suddenly broken, and the 


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higher the potential the more marked this effect will be. The 
current tends to keep on flowing, and the extra potential which 
this self-induction gives it will cause it to arc, or bridge, the gap at 
the break, unless a condenser is provided to take care of this. Every 
circuit possesses self-induction, but it is only marked in circuits 
having considerable inductance, that is, in coils, and especially those 
with iron cores, such as induction coils, circuit breakers, etc. 

Capacity of Condensers. Every conductor of electricity has 
capacity to hold a charge just as a vessel holds water. But the 
capacity of a conductor is dependent upon its surface area rather than 
its cross-section, or cubic volume, and is also influenced by surround- 
ing conditions. Where it is desired to accumulate a considerable 
charge, as for an ignition spark, a special form of capacity is utilized. 
This is known as a condenser (a detailed description of which is 
given later in connection with ignition coils). The ability of a 
condenser to absorb the rise in potential that occurs through selt- 
induction whenever a circuit containing inductance is opened is 
also utilized to prevent sparking at contact points. Comparatively 
small condensers are necessary for this purpose, and they are shunted 
around the contact points, that is, connected in parallel with the 
latter. When the circuit is opened the excess energy of the circuit 
passes into the condenser instead of forming a hot spark at the 
contacts. The occurrence of any undue amount of sparking at 
contacts should accordingly be made the subject of an investigation 
of the condenser connections, or of the condenser itself. 

Comparison of Generator Current to Water Flow. The com- 
parison of air in a room has been made to illustrate the presence 
of electricity and its characteristics, since it may be made to partake 
of all the latter by being put under pressure, allowed to escape 
through various sized outlets, and made to perform work of differing 
nature by being utilized at varying pressures and volumes, exactly 
as electricity is. Where an electric current is produced by a gener- 
ator, however, the older simile of water flowing under pressure due 
to the impulse of a pump may serve to make it much clearer. 
This comparison of a water pump and its piping with an electric 
generator and its circuits is known as a hydraulic analogue, and, it 
may be added, there is scarcely any characteristic or function of 
the electrical current that cannot be similarly compared. 


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Take, for example, a waterworks system of the type in which 
a large pump at the power house draws water from artesian wells 
or a reservoir and forces it into a closed system of piping. Located 
on this piping system are all the house outlets, street hydrants, and 
the like. The speed of the pump is regulated so as to keep a certain 
amount of pressure on the water in the pipes, based upon the average 
demand at different periods of the day. The pressure is reduced at 
night and is increased at any time, day or night, in case of fire. 

Pressure and Voltage. This constant pressure in pounds per 
sqliare inch that the pumps maintain on the supply of water in the 
entire piping system is the exact counterpart of the voltage, or electro- 
motive force, produced by a dynamo, or generator, when running. 
Just as the pressure exerted on the water by the pumps depends 
upon the speed of the latter, so the voltage produced by the dynamo 
is proportional to its speed. In the case oi the pump, the pressure 
depends upon the number of times that the pistons of the pump 
reciprocate; in the dynamo, upon the number of times that the 
coils, or windings, of the armature cut the lines of force of the mag- 
netic field in which it revolves. This is explained in detail later 
in connection with generator principles. 

When the pump moves very slowly, there is very little pressure 
produced in the pipes, and this is the case with the dynamo to an 
even greater extent, since dynamos are usually designed to run at 
very much higher speeds, and consequently their voltage, or pressure, 
drops off very sharply at low speeds. This will explain why the 
majority of lighting generators on automobiles do not begin to charge 
the battery until the motor of the car is running at a speed equiva- 
lent to ten to fifteen miles per hour, as explained later. At low 
speeds they do not generate sufficient voltage to overcome that of 
the battery. 

Fall in Pressure. When either a pump or a dynamo is running 
at a constant speed, the pressure, or voltage, produced at the machine 
is practically constant. But in the case of the water system, the 
pressure is not the same at the outlet of a branch line a mile away 
from the power house as it is at the delivery end of the pump, nor 
is the voltage on a branch circuit at a great distance from the dynamo 
the same as it is at the terminals of the latter, consequently, 
the fall in pressure in the water piping is the exact counterpart of 


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the drop in voltage on the electric circuit due to the resistance of 
the wires. In the case of the water supply, the friction encountered 
by the water in passing through the pipes is analogous to the resist- 
ance which the electric current must overcome, except that bends 
in a wire do not impose any greater resistance to the current than 
the same length of wire when straight, whereas bends in piping greatly 
add to the friction with a correspondingly greater drop in pressure. 

Friction and Resistance. There is, in consequence, almost an 
exact parallel between the mechanical friction of water passing 
through a pipe and that of the electric current passing through a 
wire, as it is commonly said to do. Friction in water piping is 
inversely proportional to the size of the pipe in proportion to the 
pressure to which the water is subjected, and is directly proportional 
to the length of the pipe in exactly the same way that a wire opposes 
more resistance to the electric current the smaller the wire is, and 
the amount of resistance also increases with the length of the wire 
itself. In both cases, the product of this friction, or resistance, is 
heat; and it results in a drop in pressure, whether mechanical or 

Current and Volume. So far the comparison has been limited 
entirely to the pressure exerted by the pump on the supply line as 
compared with the voltage of the generator imposed on the circuit. 
In a similar way the flow of water from the pipe line may be compared 
with that of the current in an electrical circuit. Assume, for example, 
that, in the case of the water-supply system, the pumps generate a 
pressure of 100 pounds to the square inch. Eliminating from con- 
sideration any drop in pressure between the pump and outlet as 
only tending to confuse the comparison, suppose a half-inch faucet 
to be opened at a distant part of the system. Then there will flow 
from the pipe an amount of water proportioned to the size of the 
outlet times the pressure, or head, back of it. Let us assume that 
this will be one cubic foot per minute, or, roughly, eight gallons. 

In the same way, assume that the generator imposes a pressure 
of 100 volts on the line and, for purposes of comparison, there is 
no drop between the generator and the end of the line. So long as 
there is no outlet open there is pressure on the water in the supply 
system, but no flow. This is likewise the case with the electric 
circuit. The voltage is present as long; as the armature of the dynamo 



is revolving, but there is no flow of current in the circuit. A small 
fan motor, corresponding to the half-inch faucet, is switched on at 
a distant part of the circuit. There is then a flow of current of, 
say one ampere. In this case, the hydraulic analogue reflects exactly 
the action of the current as compared with the water supply in a 
pipe. If, instead of opening a small house faucet, we open the valve 
of a branch main a foot in diameter, there is a correspondingly greater 
volume of water flowing, but the pressure remains the same. On the 
other hand, if, instead of a small fan motor, a five-horsepower motor 
is switched into the circuit, the outflow of current will be equivalent 
to five horsepower, though the voltage of the circuit will remain 
the same. (There is, of course, always a voltage drop with every 
piece of apparatus that the current passes through before com- 
pleting the circuit by returning to the generator, just as there is a 
drop in water pressure for every additional length of pipe or open 
outlet in the system; but, to keep the comparison clear and simple, 
this is not taken into consideration here.) Thus, in one case, we 
have one cubic foot of water per minute flowing under a head, or 
pressure, of 100 pounds per square inch; in the other, a current of 
one ampere at a voltage of 100; also the fact that the volume of 
either water or electricity that will flow depends upon the resist- 
ance of the outlet. The fan motor is wound to a high resistance, 
and, consequently, only one ampere of current is required to 
operate it at its maximum speed. In the same way, the i-inch out- 
let will permit only one cubic foot of water to escape per minute. 
Increasing the size of the outlet in either case increases the How 
correspondingly. The simile holds good with the water system 
up to the point where the outlet becomes too large to permit the 
pumps to maintain the pressure; but, in the case of the electric 
generator, the resistance cannot be decreased to zero, since this 
would result in a short-circuit permitting the entire current output 
of the dynamo to flow. Unless the dynamo were protected by cir- 
cuit breakers and fuses, the functions of both of which are explained 
later, the windings of the machine would be burned out. 

Power Comparison. To go back to the simile between water 
and current flow, it will be noted that in one case there is a flow 
of one cubic foot per minute at 100 pounds to the square inch, and, 
in the other, a flow of one ampere of current at 100 volts. This 

382 Digitized by G00gle 


flow of water represents power just as the flow of electric current 
does, and it may be utilized in a similar manner. The product of 
the volume times the pressure would give foot-pounds in the case 
of the water and watts in the case of the electrical energy, in 
other words, one ampere times 100 volts, or 100 watts — almost 
one-seventh of a horsepower. 

Circuits. The simile of the water-supply system does not 
correspond exactly to any type of electric circuit, in that the water 
does not return to the pump in any case, as the current always must 
to the generator, to complete the circuit. But it does afford a com- 
parison of the characteristics of both series and multiple circuits, 
showing to what an extent the illustration of electrical principles 
may be carried by means of a simple mechanical analogue. For 
instance, the opening of one outlet after another in a water system 
reduces the pressure in the entire system, just as the insertion of 
one piece of apparatus after another in a series electric circuit 
causes a corresponding drop in voltage for each addition, except, 
of course, that in case of the series electric circuit it must always 
be complete, regardless of whether one or a dozen different pieces 
of apparatus be included in it. In other words, the current must 
pass through each one of them in turn to complete the circuit. On 
the other hand, the water system has. some of the characteristics 
of a multiple, or parallel, electric circuit, in that the opening of one 
outlet does not prevent the use of others, whereas in the series circuit, 
the breakdown of one piece of apparatus, such as a motor or a lamp, 
puts all the others out of action by opening the circuit. 

The comparison may be carried still further to illustrate other 
attributes of the electric circuit. For example, if there be a bad 
break in one of the large mains of the water system, no water will 
reach smaller outlets beyond the break in the main, the entire volume 
flowing out of this opening. This corresponds very closely to a 
ground or short-circuit on an electric circuit. If one of the wires, 
instead of carrying the current to the motors, permits its supply to 
return to the generator by a shorter path, due to faulty insulation 
or a broken wire touching the ground, no useful work will be per- 
formed by the current. It will escape and be wasted just as the 
water is, with this important difference, however, that in the 
case of the water pumps, the break in the main will be evidenced 



only by a marked decrease in the pressure, and the pumps will run 
to no purpose, whereas the electric generator will still continue to 
generate its full voltage, and, unless the grounded circuit caused by the 

break has sufficient resistance, 

~~ \^*V the circuit breaker, or fuses, 

/ \^ST must operate to protect it. 

V <T^ȣ^"* " " Classification. All dy- 
\^ ^"v ^/CsW namo-electric machines are 

Pig. 17. Elementary Principle of Generator Commercial applications of 

Faraday's discovery of in- 
duced currents in 1831. They are all designed to transform the 
mechanical energy of a steam engine, a waterfall, a gasoline engine, 
etc., into the energy of an electric current. Whenever large currents 
are required — for example, in running street cars; in systems of 
lighting and heating; in the smelting, welding, and refining of metals; 
the charging of storage batteries, etc. — they are always produced 
by dynamo-electric machines. 

There are two kinds of generators (1) d.c, or those producing a 
unidirectional (direct) current, that is, one which always flows in 
the same direction in the external circuit, and (2) a.c, or those 
producing an alternating current, that is, one which reverses in 
direction continuously throughout the entire circuit. 

Elementary Dynamo. Whenever lines of magnetic flux are cut by 
a conductor, for example, by a wire passing through them, an e.m.f . 
(electromotive force) is produced in the conductor, and the strength 
of this e.m.f. is entirely dependent upon the speed at which the 
conductor passes through the magnetic field. If, at the time that 
this is done, the ends of the wire are brought together to form a 
circuit, a current will' be induced in the conductor. The simplest 
form of generator would consist of a single loop of wire ABCD 
arranged to rotate in a magnetic field, as shown by Fig. 17. Having 
its plane parallel to the direction of the magnetic flux, the loop, if 
it be rotated to the left as shown, will have an e.m.f. induced in it 
that will tend to cause a current to flow in the direction shown by 
the arrows. The e.m.f. 's induced in AB and CD for the position 
shown will have their maximum values since the wires are then cut- 






ting the magnetic flux at right angles and are consequently cutting 
more lines of force per second than in any other part of the revo- 
lution. Note that as CD moves up, AB moves down (and vice 
versa) across the magnetic flux so that the induced currents in all 
parts of the loop at any instant are 
flowing in one direction. The value 
of this e.m.f. depends upon the 
speed, and as the loop approaches 
the 90-degree, or vertical, position, 
the e.m.f. decreases because the rate 
of cutting is diminishing, until when 
the loop is vertical both the cutting 
of the magnetic flux and the generated e.m.f. are at zero. If the rota- 
tion is continued, the rate again gradually increases, until at 180 
degrees it is once more a maximum. The cutting, however, in the two 
quadrants following the 90-degree position has been in the opposite 
direction to that occurring in the first quadrant, so that the direction 

Fig. 18. Dynamo E. M. F. Curve 

Fig. 19. Simple Form of Generator Showing Arrangement of Brushes 
in Contact with Commutator 

of the e.m.f. generated is reversed. Plotting this through an entire 
rotation gives the curve shown in Fig. 18. Such an e.m.f. is termed 
alternating because of its reversal from positive to negative values, 
first in one direction and then in the other, through the circuit. 
It cannot be utilized for charging a storage battery, and hence it 
is not employed in connection with starting and lighting dynamos 
and motors. To convert an alternating current into a direct or 
continuous current, a commutator must be added. 

Commutators. Fig. 19 illustrates a commutator in its simplest 
form. It may be imagined as consisting of a small brass tube 
which has been sawed in two longitudinally, the halves being mounted 


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Fig. 20. Commutator with Double Turn 

on a wooden rod. The wood and the two cuts in the tube insulate 
the halves from each other. Each one of these halves is connected 
to one terminal of the loop, as shown in the illustration, Fig. 20. 
Against this commutator, Fig. 
19, two brushes bear at opposite 
points and lead the current due to 
the generated e.m.f. to the ex- 
ternal circuit. If these brushes 
are so set that each half of the 
split tube moves out of contact 
with one brush and into contact 
with another at the instant when 
the loop is passing through the 
positions where the rate of cutting is minimum (as indicated in 
the enlarged end view of the commutator shown at A), a unidi- 
rectional current will be produced, but it will be of the pulsating 
character as indicated by the curve for one cycle shown in Fig. 21. 

This would also be the case, 
if instead of the single loop, a coil 
wound on an iron ring be substi- 
tuted, as in Fig. 22, the only effect 
of this being to increase the e.m.f. 
by increasing the number of times 
the electrical circuit cuts the magnetic flux. Now assume that two 
coils are connected to the commutator bars, instead of the single 
loop, shown in Fig. 22. This arrangement will give the simple 
device shown in Fig. 23, called an armature. The two coils are 

6° " 90° 160* 270° 060° 

Fig. 21. E. M. F. Curve with Com- 

Fig. 22. Armature with Single Coil 

Fig. 23. Two-Coil Armature 

in parallel and while the voltage generated by revolving this winding 
with two coils is no greater than with one coil, the current-carrying 
capacity of the winding is doubled. The current generated by 


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this form of armature would still have the disadvantage, however, 
of being pulsating. As in the case of the automobile motor, the 
number of cylinders must be increased to make the power output 

a continuous unbroken line, so 
armature coils and their corre- 
sponding commutator brushes 
must be added that one set may 
come into action before the other 
"goes dead". By placing an 
extra pair of coils on the arma- 
ture, at right angles to the first, 
as shown in Fig. 24, one set will 
be in the position of maximum activity when the other is at the point 
of least action. While this armature would produce a continuous 
current, it would not be steady, having four pulsations per revolu- 
tion, and it is consequently necessary to increase the number of 
coils and commutator segments still further to generate a steady, 
continuous current. This is what is done in practice. 

A commutator consists of a number of copper bars or segments, 
equal to the number of sections in the armature. These bars are 
separated by sheets of insulating material, usually mica, and are 

Fig. 24. Four-Coil Armature 

Fig. 25. Sectional and End Views of a Commutator 
Courtesy of Horseless Age 

firmly held together by a clamping device consisting of a metal 
sleeve with a head having its inner side undercut at an angle, a 
washer similar in shape to the head of the sleeve, and a nut that 


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screws over the end of the sleeve, as shown in the left-hand or 
sectional view of Fig. 25. The sleeve is surrounded by a bushing 
of insulating material, and washers of the same material are placed 
between the assembly of commutator bars and the two clamping heads. 
Each bar is then completely insulated from every other bar and from 
the clamping sleeve. Commutators are also made by pressing the 
entire assembly of copper segments together, or molding them, 
in insulating material (Bakelite), which thus forms the hub or 
mounting of the commutator as well as the insulating material 
between the segments. After assembling, the commutator is 
turned down in a lathe to a true-running cylinder and then sand- 
papered on its outer cylindrical surface to present a smooth bearing 
surface for the brushes. At the inner end of the commutator 
which is closest to the armature windings, the commutator bars 
are provided with lugs as shown in the sectional view; these lugs 
are slotted and the armature leads are soldered to them. At the 
right, Fig. 25, is shown an end view of the same commutator. 

From the repair man's point of view, the commutator is the 
most important part of the generator or the motor, since it is one 
of the first with whose shortcomings he makes acquaintance. Prae* 
tically all lighting and starting motors now have their armature 
shafts mounted on annular ball bearings, so that the commutator 
and the brushes are the only parts that are subject to wear. If 
the time devoted in the garage to the maintenance of automobile 
electric systems were to be divided according to the units demanding 
attention, the battery would naturally come first, brushes and 
commutators next, then switches, regulating instruments, con- 
nections, and wiring, about in the order named. After all of these 
come, of course, burnt-out armatures or other internal derangements 
which necessitate returning the units to the manufacturer; but 
troubles of this nature are quite rare. While this list gives the 
order of precedence, it has no bearing on the relative importance 
of the troubles; with respect to the total time taken by each, the 
battery is responsible for not far from 90 per cent, the commutator 
for about 5 per cent, all other causes comprising the remaining 5 
per cent. 

Armature Windings. In the simple illustrations given to 
show the method of generating e.m.f. in the armature and leading 


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the current to the external circuit, what is known as the ring type 
of winding is shown. This is inefficient because half the length 
of the conductor — the portion inside the ring — does not cut any 
lines of force and hence does not aid in generating the current. 
The design, moreover, does not lend itself to compactness, so that 
it would not be adapted to automobile work even if there were no 
objection to it on the score of inefficiency. A slotted type of arma- 
ture core is very generally employed for the small generators and 
starting motors used on automobiles and the wire is either wound 
directly in the slots, or is "form wound", that is, the wire is placed 
on ,a wooden form shaped to correspond to the position the coil will 
take when in place on the armature. After winding the necessary 
length of conductor on this foundation, the wire is taped together, and 
varnished or impregnated with an insulating compound, and baked. 

Owing to its high magnetic permeability, iron is universally 
employed for the core of the armature, since the function of the 
core is to carry the magnetic flux across from pole to pole of the 
field magnets, as well as to form a foundation for the coils. How- 
ever, when a mass of iron is rotated in the field of a magnet what 
are known as "eddy currents" are set up in the metal itself, and 
these prevent the inner parts of the mass from becoming magnetized 
as rapidly as the outer and also cause the interior to retain its mag- 
netism longer. As the efficiency of the generator depends upon 
the rapidity with which the sections of the armature become mag- 
netized and demagnetized as they revolve, the lag due to these eddy 
currents is a detriment. To reduce this effect to the minimum, 
the armature cores are always laminated, that is, built up of thin 
disks of very soft iron or mild steel, these disks having the necessary 
slots punched in them to accommodate the windings when assembled 
on the shaft. The disks are insulated from one another either by 
varnishing them or by inserting paper disks between them. They 
are assembled on the shaft and are put together under considerable 
pressure, various means being employed to hold them in place. 
These disks are so thin that hundreds of them are required to make 
an armature core only a few inches long, and when pressed together 
in place they are to all intents and purposes a solid mass. 

Armature winding, however, is something that is entirely 
beyond the province of either the car owner or the repair man, no 


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matter how well equipped a shop he has. It is a job for the expert 
in that particular line, and on ;the rare occasions when an armature 
does go wrong, it should always be returned to the manufacturer, 
if possible, if not, to a shop making a 
speciality of such work. 

Field Magnets. In the foregoing 
explanation of the generation of an 
e.m.f. in a conductor when rotated in a 
magnetic field and the leading out of 
the current through a commutator, the 
presence of the field has been assumed 
and nothing has been said regarding 
the method of providing it. The term 
field is applied interchangeably to the 
magnetic flux between the pole faces of 
the field magnets and to the magnets 
themselves, but it is more generally 
understood to refer to the latter directly 
and to the former by inference. There 
are various methods of maintaining 
the flux, usually described as "field magnet excitation", but only 
two of them are applicable to the electric generators employed on 
the automobile. 

Permanent Field Used in Magneto. The simplest of these, 
and the first to be designed, employed permanent magnets, from 
which such a generator takes its name, 
magneto. Fig. 26 is a diagrammatic rep- 
resentation of an early form of the mag- 
neto-generator. Since magnetism cannot 
be maintained permanently at the high 
flux-density or strength which can be 
produced by an exciting coil fed by a 
current, this method is only employed 
in very small generators, as its bulk for 
large powers would be excessive. Its 
great advantage is its simplicity and constancy. The magneto-gener- 
ator shown in Fig. 26, however, is designed to produce a continuous 
current, and is not the type in general use on the automobile today. 

Fig. 26. Diagram of Magneto 

Fig. 27. Sketch Showing Shape of 

Armature Core 

Courtesy of Horseless Age 


• Digitized by 




The type usually installed is made with a two-pole armature, 
as shown by Fig. 27. This figure illustrates the core known as 
a "shuttle" type because the wire is wound around the center of 
the core in much the same manner as thread is put on a shuttle. 
These cores are laminated as already described, in all well-built 
magnetos. The space on the core is filled with a single coil of 
comparatively coarse wire on the majority of magnetos, which 
generate a low voltage current that is subsequently stepped up 
through an outside transformer. In some instances, in what may be 
termed the true high-tension type of magneto, there is a second wind- 
ing of fine wire on the core so that the magneto generates a current 


A B C 

Fig. 28. Diagrams Showing Distribution of Magnetic Flux for Various Positions 
Courtesy of Horseless Age 

and steps it up without the aid of any outside devices. In either 
case, one end of the winding is "grounded on the core", that is, 
connected to it electrically, so that the core and other metal parts 
of the machine form one side of the circuit, while the other end is 
connected to a stud against which a spring-controlled carbon brush 
bears, to collect the current. Detailed descriptions of various 
types of magnetos are given later so that nothing further concerning 
the construction need be added here. 

Principle of Operation of Magneto. Under "Generator Prin- 
ciples", the principle of the operation of the magneto has already 
been explained, the method by which the rotation of the conductors 
in the magnetic field generates an e.m.f. and a current is induced 


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in them. But as the actual operation of the magneto as designed 
for ignition purposes is radically different from any other form of 
generator, it is given here. If unrestricted, the armature of the 
magneto will always assume the position shown at A, Fig. 28, and 
considerable effort will be required to turn it from this position 
as the magnetic flux through the armature is then a maximum. 
When the armature is rotated a little over 90 degrees from this 
horizontal position so that the armature poles leave the field poles, 
as at B in the same figure, the flux decreases, and when in a vertical 
position no lines of force pass through it. At this point, the direction 

&ie Revolution Qfyfrmatur* 

Fig. 29. Curve of Primary E. M. F. in Magneto on 

Open Circuit 

Courtesy of Horseless Age 

of the magnetic flux through the armature core reverses. Having 
a two-pole armature, the magneto produces an alternating current 
of one complete cycle per revolution, as shown by the curve, Fig. 
29, which illustrates the electromotive force generated at the dif- 
ferent positions in the rotation of the armature. The similarity 
between this curve and the one generated by the elementary dynamo, 
Fig. 17, will be noted. With the armature in the horizontal position 
there is a dead point, the e.m.f. curve only starting as the pole 
pieces of the armature begin to cut the edges of the field magnet 
poles. It then rises very sharply to a peak, and as sharply drops 


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Fig. 30. Diagram Showing Series Generator 

away to zero again, thus forming one-half cycle, which is then repeated 
in the opposite direction. As the present discussion comprises 

on 'y an introduction to elemen- 

V Q (J (j * ar y principles and theories* 

^ further details of construction 

and operation of the magneto 

are given later in the section on 


Self-Excited Fields. In a 
machine of the magneto type, the 
only method of varying the cur- 
rent output is to vary the speed 
of the armature, and it is there- 
fore not well adapted to the 
majority of uses for which a gen- 
erator is employed. Conse- 
quently, other methods of excit- 
ing the fields have been developed, which may be roughly divided 
into two classes: first, those separately excited, in which cur- 
rent from an independent source is supplied to the field windings. 
This is now practically restricted to large alternating-current gen- 
erators and so need not be con- 
sidered further here. Second, 
self-excited fields, which are now 
characteristic of all continuous 
current generators. In this 
method all or a part of the cur- 
rent induced in the armature 
windings is passed through the 
field coils, the amount depend- 
ing on the type of generator. 

Series Generator. Where 
the entire current output is util- 
ized for this purpose, the dynamo 
is of the series type, and a refer- 
ence to the section on "Cir- 
in connection with the illustration, Fig. 30, will make this 
There is but a single circuit on such a dynamo &nd while it 






Fig. 31. Diagram Showing Shunt-Wound 




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has the advantage of simplicity, it does not generate a current until 
a fairly high speed is reached, or unless the resistance in the 
external circuit is below a certain limit. It is also likely to have 
its polarity reversed so that it is not fitted for charging storage 
batteries. As the only series generators put into commercial use 
have been for supplying arc lamps in series for street lighting, 
they need not be considered further. 

Shunt-Wound Generator. By winding the generator with two 
circuits instead of one and giving that of the fields a relatively high 
resistance as compared with the outside circuit on which the generator 
is to work, a machine that is self-regulating within certain limits 
is produced. As shown by Fig. 
31, the main circuit of the gener- 
ator is that through the arma- 
ture with which the field wind- 
ing is in shunt. The current 
accordingly divides inversely as 
the resistance and only a small 
part of it flows through the field 
coils, while the main output of 
the generator flows through the 
external circuit to light the lamps, 
to charge a battery, or the like, 
the resistance of this external 
circuit being much less than that 
of the fields. But in this type, 
as well as in the simple series form, the e.m.f. generated varies more 
or less with the load, and as the latter is constantly changing, it 
is necessary to provide some means of varying the e.m.f. gen- 
erated to suit the load, in other words, to make the generator 
self-regulating. Of the several available methods of doing this, 
the only one applicable to the small direct-current generators used 
in automobile lighting and starting systems, is that of varying the 
magnetic flux through the armature. 

Compound-Wound Generator. There are also several methods 
of effecting this variation of the magnetic flux, but the most advan- 
tageous and consequently the most generally used, is to vary the 
amount of current in the energizing coils on the field magnets. 

Fig. 32. 

Diagram Showing Compound- 
Wound Generator 


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By adding to the shunt winding a few turns of heavy wire in series 
with the armature so that all the current passes through them, the 
magnetic flux may be made to increase with the load as it is directly 
affected by the current demanded by the latter. This combination 
of the shunt and series is termed a compound winding, and the 
usual method of affecting it is shown by Fig. 32. Such a machine 


Fig. 33. Forms of Field Frames 

is called a compound generator, and is sometimes used for lighting 
and for charging the storage batteries of automobiles. 

In view of the great range of speed variation required of the 
automobile motor, the series wiring is sometimes reversed so as 
to act against the shunt instead of with it, in order to prevent an 
excessive amount of flux and a current that would be dangerous 
to the windings themselves due to a very high speed. The compound 


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winding then opposes the shunt-winding and is termed a hiking- 
coil or winding. This is referred to later in connection with the 
discussion of methods of regulating the generator on the automobile. 

Forms of Field Magnets. For greater simplicity, all of the 
illustrations shown in connection with the explanation of the various 
types of generators are of the old bipolar type in a form long since 
obsolete. The field frame, as it is designated may, however, take 
a number of different forms depending entirely upon the designer's 
conception of what best meets the requirements of ample power 
in the minimum of space and with the minimum weight. Fig. 
33 shows some typical forms of field frames in general use on auto- 
mobile generators, and it will be noted that in addition to providing 
a magnetic circuit the field frame also serves to enclose the windings. 
These are known as "ironclad" types from the fact that all parts 
are thoroughly enclosed and protected. The arrows in each case 
indicate the paths of the magnetic circuits, the number of the cir- 
cuits varying with the number of pole pieces. The form at A has 
two opposed poles, each of which is designed to carry an exciting 
coil or winding. This is a bipolar machine. Field frame B is 
also of the bipolar type but only one pole carries an exciting winding, 
the other being known as a consequent pole. In both of these 
field frames, it will be noted that the magnetic circuits are long, 
which adds to the magnetic reluctance and tends to decrease the 
efficiency. To overcome this, multipolar types of field frames 
are very generally employed. One of these, with two wound or 
salient poles and two consequent poles, is shown at D, the extra 
poles making four short instead of two long magnetic circuits. 
C is a multipolar type with four salient poles. 

Brushes. Brushes serve to conduct the current generated 
by the armature to the outer circuit and ta the field coils in order 
that the excitation of the latter may correspond with the demand 
upon the generator. The brushes originally employed were strips 
of copper which bore on the commutator; as generators increased 
in size these brushes were built up of thin laminations of copper. 
Plain copper brushes in any form, however, cause an excessive 
amount of sparking which is ruinous to the smooth surface and 
true running of a commutator. Built-up copper gauze brushes 
were then adopted, and they were fitted to bear against the com- 

396 . 

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mutator. Though an improvement, these did not meet all the 
requirements and were in turn superseded by carbon brushes, 
which are now practically universal. The carbon brushes usually 
bear directly against the face of the commutator, either through 
a blunt, squared end, or one that is slightly beveled. The brush 
holders are generally attached to rocker rings, which allow adjust- 
ments to prevent sparking; in these holders are small helical springs 
under compression, which serve to press the brush against the commu- 
tator. Ordinarily, the brushes are composed of a uniformly smooth 
and homogeneous compound of carbon that soon acquires a glazed 
surface at its bearing end and wears indefinitely without requiring 
any attention, but at times a gritty brush will be found. Such a 
brush scratches the commutator surface, wears unevenly, and is 
generally a source of trouble. 

Badly worn commutators frequently result from the use of 
improper brushes, or too heavy a spring pressure — also from too 
light a spring pressure. The manufacturer has found out by experi- 
ment and study just what character of brush is best adapted to 
his particular generator or starting motor and also the exact amount 
of spring pressure that is necessary to insure the best results. Con- 
sequently, much trouble will be avoided if brushes are replaced 
only with those supplied by the manufacturer of that particular 
machine, in connection with the brush springs that were designed 
for it. There are electrical as well as mechanical reasons for this, 
since both the resistance and current-carrying capacity of carbon 
brushes vary. This has been taken into consideration by the man- 
ufacturer who has provided a brush especially adapted to his 


Theory of Operation. A machine that is designed to convert 
mechanical into electrical energy or the reverse, is known as a 
dynamo-electric machine. When its armature is rotated by an 
external source of power, such as a steam engine, hydraulic turbine, 
or gasoline engine, it is a generator. By sending a current through 
it from another generator or a battery it converts electrical into 
mechanical energy and is a motor. It is evident, then, that a 
generator and a motor are fundamentally one and the same thing, 
and a reversal of the conditions one unit may be made to 




serve both purposes. It will naturally depend upon how closely 
these purposes approach each other so far as their operating con- 
ditions are concerned, whether it will be practical to employ the 
same machine for both. In practice, operating conditions rarely 
approximate and so before the advent of the single-unit starting- 
and-lighting system on automobiles the use of the same machine 
for both generating current and converting it into mechanical 
energy was practically unknown. Space considerations were the 
chief factor which led to the development of the single system, 
as the demands on the machine for charging the battery and starting 
the engine are radically different. 

How Rotation Is Produced. The operation of an electric motor 
will be clear if the essentials of a dynamo-electric machine and their 
relations are kept in mind. There is, first, the magnetic field and 
its poles — two or any multiple thereof, though for space reasons 
more than four poles are seldom used in starting motors; then the 
armature, which must also have an even number of poles corre- 
sponding to the number of segments in the commutator. Each 
separate coil in the armature winding magnetizes that section of 
the armature core on which it is wound, when the current passes 
through it, as its terminals, connected to different segments on the 
commutator, come under the brushes. In an electric motor having 
either two or four field poles, and eight, twelve, or sixteen armature 
poles, it is apparent that every few degrees in the revolution of 
the armature an oppositely disposed set of its poles is either just 
approaching or just leaving the magnetic field of two of the field 
poles. Bearing in mind that like poles repel one another and that 
unlike poles attract, and that the polarity of both the fields and 
the armature coils is constantly being alternated by the commutator, 
we see that each section of the armature is constantly being attracted 
toward and repelled from the field poles. 

The fundamental law just stated can be easily illustrated by 
taking two common horseshoe magnets, such as can be bought 
for a few cents. Placing their north and south poles together 
it will be found that they have no attraction for each other and 
cannot be made to adhere in this relation. If they had sufficient 
force they would actually move apart when placed on a smooth 
surface in this position. But if one of the magnets is turned around 


Digitized by 



so as to bring the north and south poles of the two opposite each 
other, the magnets will be immediately attracted and will hold 
together to the full extent of their force. 

What may be called one cycle of the operation of an electric 
motor may be described as follows: the motor turns clockwise; 
it is of the bipolar type, that is, it ha? two field poles; and therfc are 
eight coils on the armature. At the moment assumed, the left 
field pole is the north, and the right south; consequently, the section 
of the armature just entering the field is of opposite polarity, pre- 
senting a south pole to the north pole of the field and a north pole 
to the south pole of the latter. The armature is therefore strongly 
attracted. This attraction is maintained by the current in the 
windings continuing in the same direction until the magnetic attrac- 
tion reaches a maximum, at which point the stationary and moving 
poles are practically opposite each other. Unless a change occurred 
just at that point the armature would be held stationary and could 
be turned from it only by the expenditure of considerable force, 
that is, assuming that the field did not lose its exciting current. 
(This may be observed on a small scale by attempting to revolve 
the armature of a magneto by turning its shaft by hand.) But 
either at that point, or just before it is reached, the revolution of 
the armature brings a different set of commutator bars under the 
brushes and the direction of the current is reversed in that particular 
winding and with it the polarity of the armature poles. Instead 
of being mutually attracted the armature and field poles become 
mutually repellent. In brief, the armature is first pulled and then 
pushed around in the same direction by reason of the force exerted 
both by the field magnets and by its own magnets. The passing 
of one section of the armature through this change as it enters 
and leaves the zone of influence of a pair of pole pieces may be said 
to constitute a cycle of its operation, by analogy with alternating- 
current generation. The cycles are repeated as many times per 
revolution as there are coils on the armature and the number of 
coils miltiplied by the speed will give the number of changes per 
minute. For example, in a motor assumed to have eight armature 
coils, as in the present instance, there would be, at a speed of 1,000 
r.p.m., 16,000 changes per minute, which makes clear the reason 
for the very smooth pull or torque that an electric motor exerts. 


Digitized by 



Counter E.M.F. Though being rotated by means of current 
obtained from an external source of power, it is apparent that the 
motor armature in revolving its coils in the magnetic field is fulfilling 
the conditions previously mentioned as necessary for the generation 
of an e.m.f. Experiment shows that the voltage and current thus 
generated are in an opposite direction to that which is operating 
the motor. It is accordingly termed a counter e.m.f. as it opposes 
the operating current. This, together with the fact that the resist- 
ance of copper increases with its temperature and that the armature 
becomes warmer as it rung, explains why the resistance of a motor 
is apparently so much greater when running than when standing 
idle. The counter e.m.f. approaches in value that of the line e.m.f., or 
voltage at which current is being supplied to the motor. It can, 
of course, never quite equal the latter for in that case no current 
would flow. The two opposing e.m.f. 's would equalize each other; 
there would be no difference of potential. 

Types of Motors. Being the counterparts of electric generators, 
electric motors differ in type according to their windings in the same 
manner as already explained for generators. The plain series-wound 
motor is nothing more or less than the simple series-wound generator 
to which reference has already been made; the shunt and compound 
motors likewise correspond to the shunt and compound generators. 
But while the series-wound generator was of extremely limited 
application and has long since become obsolete, the series-wound 
motor possesses certain characteristics which make it very generally 
used. It is practically the only type employed for starting service 
on the automobile, and it is also in almost universal use for railway 
service. The reasons for this are its very heavy starting torque 
which increases as the speed of the motor decreases, the quick drop 
in the current required as the motor attains speed, and its liberal 
overload capacity. It is essentially a variable speed motor, and, 
just as the plain series-wound generator delivers a current varying 
with the speed at which it is driven, so the speed of the motor changes 
in proportion to the load. These are characteristics which make 
it valuable for use both as a starting motor for the gasoline engine, 
and for a driving motor on the electric automobile, though in the 
latter case it is seldom a simple series-wound type. As its speed 
is inversely proportional to the load, however, it tends to race when 




the load is light; in other words, it will "run away" if the load is 
suddenly removed, as in declutching from the automobile engine 
after starting the latter, unless the current is instantly shut off or 
very much reduced. This is provided for, as will be explained in 
detail later in connection with the various systems. 

Shunt motors and compound-wound motors are the same as 
their counterparts, the generators of the same types, but as they are 
not used in this connection, no further reference need be made to 
them here. 

Dynamotors. As the term suggests, this is a combination of 
the generator or dynamo and the electric motor, and it is a hybrid 

Fig. 34. Dynamotor (Single Unit) of the Delco System 

for which the automobile starting system has been responsible. 
It is frequently mistermed a "motor-generator" and while its assump- 
tion of the two r61es may justify the name, the use of the term is 
misleading as it becomes confused with th^ motor-generators 
employed for converting alternating into direct current. The latter 
consist of an a-c. motor on one end of a shaft and a d-c. generator 
on the other end of the same shaft. The two units are distinct 
except for their connection, whereas a dynamotor is a single unit 
comprising both generator and motor, and it can perform only 
one of these functions at one time. A motor-generator, such as is 
used in garages for transforming alternating into direct current 
for charging storage batteries, must carry on both functions at 









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the same time in order to operate. That is, the a-c. motor must 
run as a motor in order to drive the d-c. generator and cause it 
to generate a direct current. Hence, the term motor-generator 
as applied to the single-unit type of electric starting system for an 
automobile is not in accordance with the accepted meaning of the 
words and is likely to be confusing. 

A typical example of the dynamotor is to be found in the Delco 
single-unit system, illustrated in Fig. 34. This is really the windings 
of two radically different machines, a shunt-wound generator and 
a series-wound motor, placed on the same armature core and field 
poles. As will be noted, the terminals of the two sets of windings 
on the armature are brought out in different directions and two 

commutators are employed, that at the 
right-hand end being for the generator 
windings, and that at the left for the 
motor. The method of winding the 
armature is illustrated by Fig. 35, which 
shows the generator and motor wind- 
ings projected on a plane. In the pre- 
ceding illustration the detail at the left 
shows the gearing and starting connec- 
tion for coupling the starting motor with 
the flywheel of the engine, the one at 
the right an ignition distributor for the 
Kg. 36. Typical Dry Battery high-tension current. Both of these are 

later referred to at greater length. 
Batteries. The only other method known for generating a con- 
tinuous, direct current is by means of chemical reactions in what are 
known as primary cells. With the exception of the so-called dry cell, 
a description of these and their workings could be of only historic 
interest and is accordingly omitted here. As no chemical reaction 
could take place in perfectly dry substances this part of the name 
is used simply to distinguish such cells from those using a liquid 
solution. The dry cell is a zinc-carbon couple, Fig. 36, the zinc 
acting as the container while the carbon is a heavy rod packed in 
manganese dioxide, together with some moisture-absorbing material. 
On the contents of the zinc container as thus filled is poured a 
solution of sal ammoniac and water which forms the active solution 


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of the battery. The cell is sealed at the top to prevent evaporation, 
since, when the cell does actually become as dry inside as it is out- 
side it is no longer of any use. Some of its other characteristics are 
mentioned under "Ignition", Part II. 

The storage battery or accumulator does not generate a current 
in any sense of the word. By means of a much more complicated 
chemical reaction than that of the primary cell it absorbs a charge 
of electricity. Upon the completion of the circuit of a storage 
cell with a suitable load or resistance, such as driving a motor or 
lighting a lamp, a reversal of this chemical process takes place and 
the battery redelivers a part of the current which it has previously 
absorbed. Full details of the characteristics, construction, and 
working of the storage battery are given in the article on "Electric 
Automobiles". The storage battery and the dry cell are the only 
two forms of battery employed on the automobile so that no mention 
of the other types is necessary, particularly as all but very few of 
them are practically obsolete. 


The importance of a knowledge of the fundamental principles 
of electricity and of its characteristics to the man who wishes to 
familiarize himself with the electrical apparatus on the automobile 
to the point where he can readily diagnose and remedy its ills has 
already been dwelt upon. To bring these out more clearly and make 
them easier to memorize, they are repeated here in the form of a 
brief r6sum6 in questions and answers. 

Q. What is electrical pressure, and to what may it be com- 

A. Electrical pressure is electromotive force, usually termed 
e.m.f., or voltage, also potential, and may be likened to water under 
pressure in a pipe or to compressed air in a container. 

Q. Of what does this electrical pressure consist, and how 
is it measured? 

A. It is represented by the difference of potential between two 
points in a circuit, and it is measured in volts. 

Q. What does the unit volt represent? 


Digitized by 



A. The volt is the amount of e.m.f . required to force a current 
of one ampere through a resistance of one ohm. 

Q. What is the ampere? 

A. It is the unit of current flow. 

Q. What is the ohm? 

A. The unit of resistance represented by a length of wire 
that will pass one ampere under a pressure of one volt. 

Q. In what unit is the volume of current flow measured? 

A. In the coulomb, which is the equivalent of one ampere 
per second. 

Q. Are the factors of electrical quantity, flow, and pressure 
related, and how? 

A. They are all closely related, and their relation is governed 
by the factor of resistance. 

Q. What is resistance, and of what may it consist? 

A. Any element which tends to retard the flow of the current 
is resistance. It may consist of the wire of the circuit itself; the 
windings of different apparatus in the circuit, such as an induction 
coil or a motor; the filament of a lamp; a switch; or the like. 

Q. Are these the only forms that resistance takes? 

A. No. Poor joints in wires, dirty and loose connections, 
dirty switch blades, all produce increased resistance in the circuit. 
These are undesirable increases in the resistance. In addition to 
these, there are special resistances intentionally inserted in the 
circuit to serve a definite purpose. These are known as rheostats, 
resistance coils, windings, or grids, according to the form they 

Q. Why is it desirable to keep the resistance of the circuit, 
outside of that produced by the apparatus itself, at a minimum? 

A. Because any resistance other than that interposed by the 
windings of the motor, the filaments of the lamps, or other useful 
apparatus in the circuit, not only means waste current, but also 
prevents the full amount of current required from reaching the 
desired points. 

Q. How does this waste occur? 

A. In a poor joint, a loose connection, or a dirty switch blade, 
the current is dissipated as heat and accordingly represents that much 
energy passing off into the air. 



Q. Can undesirable resistance be interposed in a circuit in any 
ways other than those already mentioned? 

A. Yes, by the use of wire too small to carry the amount of 
current required by the apparatus. 

Q. What is the effect of using wires too small for the current? 

A. The wires waste a great deal of the current in heat and, if 
much too small for the purpose, are likely to become overheated to 
a point at which they will burn the insulation off or to actually become 
fused by the current. 

Q. What determines the voltage in an electrical circuit? 

A. The potential, or. voltage, of the source of supply, such as 
a storage battery, in which case the voltage will be constant less the 
drop caused by the resistance of the circuit; or, in the case of a light- 
ing generator, it will depend upon the design of the latter (winding, 
etc.) and the speed at which it is running. 

Q. How may the voltage be varied? 

A. In the case of a battery, by varying the number of cells, each 
cell of a storage battery giving approximately 2 volts. In a gen- 
erator, by varying the windings of the field and the armature and by 
increasing or decreasing the speed at which it runs. On a circuit 
having a higher voltage than desired, by the insertion of an amount 
of resistance calculated to give the drop required. 

Q. Can lamps of a certain voltage be burned on a circuit having 
a higher voltage? 

A. Not if inserted directly in such a circuit. For example, the 
standard 6-volt lamp cannot be used directly on a 6- or a 12-cell 
storage-battery circuit as employed for the lighting and starting 
systems of many cars. The filament would immediately burn out, 
as its thickness is calculated to a nicety to become incandescent when 
current of the voltage for which it is designed is passed through it, 
and anything in excess of this voltage will fuse the wire. 

Q. How can lamps of lower voltage be used on such circuits 
without the employment of a wasteful resistance to cut the voltage 

A. By cutting down the number of cells employed for the light- 
ing, as, for example, where 12 cells are used to operate the start- 
ing motor, the battery is divided into four groups of 3 cells each 
for the lighting, these groups delivering current at 6 volts, while 

406 Digitized by GOOC 


the complete battery has a potential of 24 volts. This is termed 
putting the battery into series-multiple connection, which is explained 
further under the head of "Circuits". 

Q. When the voltage is lower than that required by the lamp, 
what happens? 

A. The lamp filament will give only a dull red glow with a volt- 
age drop of but 20 per cent or less of the total, since there is insufficient 
potential to cause the current to bring the filament wire to 

Q. Is the insertion of any apparatus, such as lamps, a motor, 
etc., in a circuit having a voltage higher than that for which they are 
designed likely to damage them? 

A. Yes, it will burn them out if, for instance, 110-volt lamps 
or motors are connected to 220-volt current, or 6-volt lamps put on a 
12-volt circuit. 

Q. Does the opposite also hold true? 

A. No. The apparatus will merely fail to function properly if 
put on a circuit of a voltage lower than that for which it is designed. 


Q. What is Ohm's law? 

A. It is the basis of all computations concerning the flow of 
an electric current. It is stated as current equals voltage divided by 
resistance and may be transposed to find any of the three factors, as, 
resistance equals voltage divided by current, so that, given any two of the 
factors, the third may be readily determined. 

Q. How is the power equivalent of an electric current 

A. Power equals current times voltage, the product being 
watts, as one volt times one ampere equals one watt. 

Q. How many watts are there in a horsepower? 

A. 746. Electrical horsepower, however, is usually figured in 
kilowatts, or units of one thousand watts, generally abbreviated to KW. 

Q. Qiven a 6-volt storage battery fully charged and a circuit 
including a starting motor, the total resistance of which (idle) is .1 
ohm, how much current will pass through the motor? 

A. As current equals voltage divided by resistance, we have 
6 -5- .1 = 60 amperes. 




Q. If, instead of a heavy stranded cable between the battery 
and motor, we substitute a fine wire having a resistance of 10 ohms, 
how much current will pass? 

A. Only .6 ampere. 

Q. What would happen if a very small wire were employed to 
connect the starting motor with the battery? 

A. Not sufficient current would reach the motor to operate it, 
and the wire would probably be fused by the heating effect of the 
heavy current. 

Q. If one horsepower be required to turn the engine over at 
100 r.p.m., and the car is equipped with a 6- volt battery, how many 
amperes will be necessary to start? 

A. As power divided by voltage equals current, 746-s-6 = 124| 

Q. How is the power equivalent usually expressed? 

A. Power equals current times voltage. 

Q. As the voltage is one of the chief determining factors, what 
effect does doubling it have? 

A. Reduces by one-half the amount of current required, exactly 
the same as doubling the pressure of a steam boiler reduces corre- 
spondingly the volume of steam necessary to perform the same 
amount of work. 

Q. If the voltage be cut in half, what will be necessary to per- 
form the same amount of work? 

A. The number of amperes, or amount of current, must be 



Q. What is magnetism? 

A. It actually is electricity in another form and is evidenced 
by the attraction or repulsion that one magnet exerts on another, 
or that any piece of magnetized metal has for objects of steel or iron. 

Q. How is this relation between magnetism and electricity 

A. By the fact that they are interchangeable. By passing a 
current of electricity through a coil surrounding an iron or steel bar, it 
becomes magnetic; upon moving a magnetized piece of metal close 
to a coil of wire, a current of electricity is induced in the wire, 

Q. What is meant by the polarity of a magnet? 



A. Upon being magnetized, a bar of steel will attract other 
pieces of metal (iron or steel) indiscriminately, but upon being 
brought close to another magnet, it will display an attraction at 
one end and a repulsion at the other for the second magnet. In 
other words, the magnetic attraction at both ends is not the same. 
These ends are termed the poles, one north and the other south, 
by analogy with the compass which is merely a magnetized needle 
having a natural tendency to point north and south. 

Q. What other characteristics do the poles of a magnet display? 

A. They show that the force of the magnet is practically 
concentrated at these poles, as the magnetic attraction is very 
much less at any other part of the bar. 

Q. What is the law of magnetic attraction and repulsion? 

A. Like poles repel Dne another and unlike poles attract. In 
other words, if a bar magnet be suspended, and the north pole of 
a second magnet be held close to the north pole of the suspended 
magnet, the latter will swing away; if the south pole of the second 
magnet be approached to the north pole of the suspended magnet, 
the latter will swing toward the former until they touch. 

Q. How does the force of this attraction or repulsion vary? 

A. Inversely as the square of the distance, i.e., separating 
the poles by twice the distance reduces the force acting between 
them to one-fourth its value. For example, if two magnets exhibit 
a strong attraction for each other at a distance of one-half inch, 
the attraction will be four times stronger when they are separated 
by only one-fourth inch. 

Q. What are the chief magnetic substances? 

A. Iron and steel. 

Q. What is meant by the magnetic field? 

A. The space immediately surrounding the poles and at which 
the magnetic force is most plainly apparent, as shown by the experi- 
ments with filings which graphically illustrate the field of influence 
of the magnet, and from which the term in question originates. 

Q. What is a magnetic circuit? 

A. The path followed by the magnetic flux, or flow, from one 
pole to the other. 

Q. What analogy is there between the poles of a magnet 
and the flow of a current in an electric circuit? 


Digitized by VjOOQIC 


A. The current is said to flow from the positive, or north, pole 
of a battery or generator, to the negative, or south, pole to complete 
the circuit, exactly as the lines of force in a magnet flow to complete 
the magnetic circuit. 

Q. How can the polarity of a current flowing in a wire be deter- 
mined by a simple experiment? 

A. Hold a small pocket compass close to the wire. If the needle 
of the compass is attracted at its north pole to the wire, the current 
flowing in the latter is negative (south pole), as unlike poles attract, 
and vice versa. This will be true only when a direct current is flowing 
in the wire, since an alternating current, as the term indicates, alter- 
nates in polarity with every cycle. 

Q. What are lines of force? 

A. The invisible flow of magnetic influence from the north to 
the south pole of a magnet or about any conductor carrying an 
electric current. 

Q. What is a solenoid? 

A. A hollow coil of wire through which a current may be passed 
to produce a magnetic field. 

Q. What is the difference between a permanent magnet and an 

A. When a piece of hard steel has been magnetized, either by 
being rubbed on another magnet or by being placed in a solenoid 
through which a current is passed, the steel retains a large percentage 
of its magnetism when removed from this magnetic field and is said 
to be a permanent magnet. An electro magnet consists of a soft iron 
or steel core on which a coil of wire is wound. When a current passes 
through the wire, the coil becomes strongly magnetic, but when the 
current ceases, the magnetism does likewise. 

Q. When a bar of iron is placed partly in the coil of a solenoid 
through the winding of which a current is passed, what takes place? 

A. The bar is strongly attracted to the center of the coil and 
held there. 

Q. How is this principle taken advantage of in electric starting 
and lighting systems on the automobile? 

A. It is employed for the operation of electromagnetic switches 
for the starting motor, and it is also the principle upon which the 
electromagnetic gear shift depends for its operation. 


Digitized by 



Q. What effect has the insertion of an iron core in a solenoid? 

A. It greatly increases the flow of magnetism through the sole- 
noid, with the same amount of current passing through the winding 
of the latter. 

Q. What effect has reversing the direction in which the current 
is passed through the winding of a solenoid? 

A. It reverses the polarity of the latter so that if the core were a 
bar of hard steel, it would be drawn into the opening of the solenoid 
with the current in one direction, and expelled from it when the cur- 
rent was reversed. 

Q. What bearing have the principles of magnetic attraction and 
repulsion and of magnetic polarity on electric generator and motor 

A. They are the fundamental principles upon which the opera- 
tion of all electric generators and motors are based. 


Q. What is the principle of electric induction? 

A. If a circuit carrying an^electric current be opened and closed 
quickly in the case of direct current, and a coil of wire be held close 
to this circuit, a current will be induced in the coil. If the latter be 
wound on an iron core, the induced current will be very much stronger, 
and if both the active circuit and the coil are on the same magnetic 
core, the maximum inductive effect will be produced. The latter is, 
in effect, a transformer, and if an alternating current be sent through 
the first circuit, or coil, there is no need to make and break the circuit 
as where the current is direct. 

Q. Why will a transformer not operate on direct current without 
making and breaking the circuit constantly? 

A. It is necessary to magnetize and demagnetize the core, or, 
where there is no core, to produce a magnetic field and then destroy 
it, in order to produce an inductive effect. 

Q. Why will it operate on alternating current without making 
and breaking the circuit? 

A. Because the alternating current intermittently rises to its 
maximum in one direction, then drops to zero and rises to its maximum 
in the opposite direction, that is, the direction or the polarity of the 
current changes with every cycle. The transformer core is accord- 


Digitized by 



ingly magnetized to full strength with a certain polarity, is then 
demagnetized and again remagnetized with the opposite polarity, 
and it is this rise and fall in the strength of the magnetic field from 
zero to maximum, first in one direction and then in the other, that 
causes the inductive effect. 

Q. What is a cycle? 

A. It consists of one alternation from zero to maximum in one 
direction, back to zero and then to the maximum in the opposite 
direction, and back again to zero. The ordinary house-lighting 
supply current is 60 cycles, i.e., it alternates 60 times per second, or 
3600 times per minute. It is owing to this extreme rapidity in alterna- 
tion that no flickering is apparent in an incandescent lamp fed by 
alternating current. 

Q. Where alternating current is not available, how can a trans» 
former be operated? 

A. By making and breaking the circuit at a high rate of speed, 
as with a vibrator used on automobile induction coils. 

Q. In general, why is no vibrator necessary on a coil when 
fed with current from the magneto? 

A. Because the magneto supplies an alternating current. 

Q. On the so-called dual system of ignition, the same coil with- 
out any vibrator is used with both the battery and magneto as a source 
of current. How is this effected? 

A. The circuit breaker, or interruptor, of the magneto takes the 
place of the vibrator when the battery is used. The current from 
the magneto alternates twice per revolution and the circuit is broken 
at the breaker points the same number of times. 

Q. What relation does the induced current bear to the current 
from the source of supply? 

A. This depends upon the transformer and the purpose for 
which it is intended. On the automobile where it is desired to raise 
the current to a high voltage to enable it to bridge the gap of the spark 
^plugs, the transformer is known as a step-up type, i.e., it takes current 
at a low voltage and transforms it to one of high voltage, or tension. 
The original, or primary, current passes through a winding of a com- 
paratively small number of turns of coarse wire on a core of soft iron 
wires. Directly over this winding is a second one consisting of a great 
number of turns of very fine wire. This is known as the secondary 


Digitized by 



winding, and the current induced in it is termed a secondary current. 
The voltage of this secondary current depends upon the voltage of the 
source of supply and the proportion that the number of turns in the 
secondary winding bears to that of the primary winding. 

Q. Is the transformer used in any other form or type on the 

A. In the so-called true high-tension type of magneto, the trans- 
former is made integral with the armature, the fine wire, or secondary 
winding, being placed directly over the coarser winding that serves 
to generate the current. The step-up is the only type of transformer 
used on the automobile. 


Q. Do materials differ greatly in their ability to conduct elec- 
tricity, and which are the most efficient in this respect? 

A. They vary all the way from absolute insulators to those 
metals which will pass the electric current with the minimum resist- 
ance, such as silver, copper, and aluminum. 

Q. Do the characteristics of a material affect its current-con- 
ducting ability? 

A. Very greatly. The harder copper is, the poorer its conduc- 
tivity, and this is likewise the case with steel. 

Q. Name the different materials in the order of their current- 
conducting ability* 

A. Silver in pure state, soft copper, brass, aluminum, iron, steel, 
carbon, German silver, etc.; also water, depending upon how alkaline 
or acid it is. 

Q. Is German silver a good conductor? 

A. No. It is known as high-resistance conductor and is accord- 
ingly used chiefly for winding resistances and not for the wires of a 

Q. What are some good insulators? 

A. Wood, glass, resin, paraffin wax, silk, cotton, asbestos, rub- 
ber, and similar mineral or vegetable substances. 

Q. Are they always equally good insulators, regardless of their 

A. They are efficient as insulators only when dry. The pres- 
ence of moisture on any of them affords a path for the current to 
cross them. 




Q. What effect on the ability of the conductor to carry a current 
has the amount of material used? 

A. The resistance is increased with a decrease in size and is also 
increased directly as the length of the conductor. 

Q. - Where, for mechanical or other reasons, it is not practical 
to use copper or aluminum, how can an equally efficient conductor 
of some other material be provided? 

A. By increasing the amount of material employed in the same 
proportion that its conductivity bears to that of copper. For 
example, assuming that steel is only one-thirtieth as good a conductor 
as copper, thirty times as much of it must be employed to give the 
same conductivity. 

Q. Give an example of this? 

A. The single-wire system of connecting the starting and light- 
ing outfit on an automobile. A small copper cable forms one side of 
the circuit, while the entire chassis forms the other. The ordinary 
trolley-road circuit is another, the small overhead wire forming one 
side of the circuit, and the rails on which the car runs, the other. 

Q. Name some of the materials which are employed for their 
high resistance to the current. 

A. German silver, iron wire, cast iron in the form of grids of 
small cross-section, and carbon. Very fine copper wire is also 
employed where the resistance desired is not very great, and space 
considerations permit its employment. 

Q. What is meant by the "specific conductivity" of a material? 

A. Its ability to conduct the current as compared with that of 
pure silver which has a specific conductivity of one. 

Q. Does this ability of a conductor to convey the current vary 
particularly with a great increase in voltage? 

A. Yes. The so-called high-tension current which has been 
stepped-up in a transformer from the 6-volt potential of the 3-cell 
storage battery to many thousand volts for ignition purposes will 
cross surfaces and penetrate materials that are perfect insulators to 
the low-tension current. For example, the high-tension current will 
leak across a moist wooden surface or it will sometimes puncture the 
one-fourth inch of rubber and cotton insulation of the secondary cable. 

Q. What is one of the chief effects of transforming a current at 
a low voltage to one of high potential? 


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A. It enables the current to leap an air gap, the width of which 
is proportioned to the voltage itself. The greater the voltage the 
greater the width of the gap it will jump. This is the principle on 
which the spark plug is based. 


Q. When a current of 2 amperes at 6 volts, such as would be 
consumed by the ordinary ignition coil from a storage battery, is 
transformed to a high potential, is the amount of current still the 
same? In other words, can 2 amperes at 6 volts be transformed or 
stepped=up to 2 amperes at 10,000 volts? 

A. No. The current decreases as the voltage increases. For 
example, to make the comparison more clear, consider a current of 
10 amperes at 100 volts. This is passed through a step-up trans- 
former, of which the ignition coil is a type, and is given a potential of 
1000 volts. The current, however, would then be 1 ampere, that is, 
the current decreases in the same proportion that the voltage is 
increased. The opposite is also true. By passing this current of 1 
ampere at 1000 volts through a step-down transformer, it may be 
converted into a current of 100 amperes at 10 volts. It will be noted 
that the product of volts times amperes in any of the above instances 
cited, or of any possible combinations that can be made, is always the 
same. In other words, a certain amount of energy is sent through the 
transformer, and the same amount, barring losses due to the trans- 
formation process itself, is taken out. 

Q. Is there any mechanical analogue of this process of trans- 
forming a current up or down to impress upon it a greater or lesser 

A. There is nothing in mechanics that corresponds exactly to 
this peculiar property of electricity. The resulting change in the 
form in which the energy is applicable as a result, however, may 
readily be compared with mechanical standards. For example, 
we may have in a very small boiler, a pressure of 1000 pounds to the 
square inch, but a volume of only one cubic foot of steam. This 
small amount at its high pressure represents the equivalent in energy 
of 10 cubic feet of steam at a pressure of 100 pounds. 

Q. What is the object of stepping the current up to such high 


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A. On the automobile, simply to enable it to jump the gap of 
the spark plug and fire the charge. In ordinary commercial service, 
to permit of sending it long distances with a minimum expenditure 
for copper wire and a minimum loss in tha amount of energy 


Q. What is meant by an electric circuit? 

A. The path by which the electrical energy, or current, is said 
to flow from and return to its source. 

Q. Is a circuit absolutely necessary in order to permit of utiliz- 
ing electricity? 

A. Unless there is a circuit or complete path for the, current, 
it does not flow. 

Q. Must a circuit be comprised completely of wires leading 
from, and returning to, the source, such as the battery or 

A. No, it is not necessary that wire be used for both sides of 
the circuit. One side or the other may be composed of a ground, 
such as the tracks of a trolley system, the overhead wire consti- 
tuting the other side of the circuit, or in the case of a single-wire 
lighting and starting system in which one cable is employed to con- 
duct the current from the battery to the starting motor and lights, 
and the chassis itself forms the ground return for both. 

Q. How many forms of circuits are there in general use? 

A. Three: the series, the multiple, and the series -multiple. 
In the first, all apparatus in the circuit is in series. That is, all the 
current from the source must pass through each instrument or light 
in turn to complete the circuit. In the multiple type of circuit, 
every instrument or light on it is independent of all the others. 
Lights may be turned on or off, motors started or stopped, without 
interfering in any way with any of the others. As its name indicates, 
the series-multiple is a combination of the two forms of circuits. For 
example, in using incandescent lamps to cut down the current for 
charging a storage battery from the lighting mains, the lamps them- 
selves are in multiple, but the whole bank of lamps is in series with 
the storage battery. See illustration on charging storage battery 
direct from lighting mains. 


Q. Which of these forms of circuit is in most general use on the 

A. All three will be found on practically every car equipped 
with a starting and a lighting system. For instance, the starting 
motor is operated in series with the battery, while the lamps are wired 
in multiple for the side and head lights, and the speedometer and tail 
light are wired in series as a branch of the multiple-lighting circuit, 
thus giving a series-multiple circuit. The ignition distributor, coil, 
and battery are in series. 

Q. What is meant by a grounded circuit? 

A. This is ordinarily used to indicate that through lack of 
insulation at some part of the wire, or similar injury, the circuit has 
been shortened, owing to this bare wire touching a ground, thus per- 
mitting the current to return to its source without passing through 
whatever instruments there may be on the circuit. A grounded cir- 
cuit, however, is also one in which one side consists of a ground return 
instead of having two wires. This is frequently distinguished by 
being termed a ground-return circuit. 

Q. What is a short-circuit? 

A. As the term indicates, a completion of the circuit short of the 
point or apparatus which the current is intended to reach. The 
example just cited is a short circuit as well as a ground, sometimes 
termed a grounded short-circuit. In other words, the abrasion of the 
insulation of one of the conductors has permitted the current to 
escape by a convenient path of return which, being of less resistance 
than the one it is intended to take, prevents any current from reaching 
the apparatus in the circuit. A ground is practically always a short- 
circuit, but the reverse is not always true, that is, a short-circuit need 
not necessarily be a ground, as in a double-wire circuit, but the two 
conductors may come together at a point where the insulation is 
worn, or winding 'of a coil may break down and cause a short- 

Q. What are some typical examples of grounded circuits on the 

A. Both the primary and secondary sides of the ignition circuit 
and the starting and lighting circuits of the so-called single-wire sys- 
tems in which the chassis is always used as a ground return for all the 
circuits employed. 


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Q. What is a hydraulic analogue, and what bearing has it on an 
electrical system? 

A. It is a comparison of the electrical system with a hydraulic 
or water-pressure system and serves to make clear the resemblance 
or analogy that exists between the principles upon which both operate. 

Q. What type of hydraulic system is similar to an electrical 
system consisting of a generator, external circuits, and lamps, motors, 
or the like, as a load? 

A. A constant-pressure system in which the pumps keep the 
water in the pipes under a certain amount of pressure corresponding 1 
to the demand. When the demand increases, the supply does like- 
wise and vice versa. (In the case of the pumping system, this is not 
automatic, but is controlled by the attendant.) 

Q. To what does the pressure of such a pumping system corre- 
spond in the electrical system? 

A. To the voltage, or electromotive, force. 

Q. Can there be voltage, or potential, in an electrical system 
without a flow of current? 

A. Yes, exactly as in the pumping system in which there is 
always a constant pressure on the water in the pipes whether the 
water is escaping through any of the outlets or not. In other words, 
there may be pressure but no flow. The same thing is true of the 
generator. If it be turning at its normal speed and is wound to 
produce current at 100 volts, there will be a potential of 100 volts 
across its terminals, even though there are no lamps or motors 
switched on in the external circuit. 

Q. How does the resistance of the pipe lines in the water system 
compare with the resistance of the wires in a circuit to the electric 

A. It is nearly the same. It varies inversely as the size of 
the pipe and directly as its length. The smaller the pipe the greater 
the resistance per foot; the longer the pipe the greater the total 
resistance. In the same way, the resistance to the electric current 
increases with the decrease in the size of the wire and increases with 
the length of the wire, the chief difference being that bends or turns 
in the wire do not add to the electrical resistance, whereas bends in 
the pipe impose greatly added resistance to the flow of water. 


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Q. What comparison may be made between the speed at which 
the generator and the pumps run? 

A. The greater the speed, the greater the pressure in the case of 
the pumps, and of the voltage in the case of the generator. Below 
a certain speed, usually termed the normal speed, there is a sharp 
falling off in the pressure in both. Neither can be operated safely 
at an excessive speed. 

Q. What is the cause of the increase in voltage with increasing 
speed in the case of the generator? 

A. Voltage, or electromotive force, is generated by the coils, 
or windings, of the armature cutting the magnetic lines of force of 
the field of the generator. The greater the number of times that 
these coils pass through the lines of force per minute, the greater 
the voltage will be. 

Q. How does fall in pressure correspond to voltage drop? 

A. To reach the end of the piping system, the water must over- 
come the resistance of the latter to its passage, and the friction 
involved robs it of some of its pressure in overcoming this resistance. 
Consequently, there is less pressure at the outlet a mile away from 
the pumps than there is at the pumps themselves. The same thing is 
true of the electric circuit. The current must force its way through 
the wires by reason of its voltage or pressure and, in so doing, some of 
the voltage is lost in overcoming the resistance of the wires, joints, 
switches, and the like. In both cases allowance for this loss is made 
by increasing the pressure at the source by an amount equivalent to 
the loss in transmission. For example, in electric street-railway work 
the motors are wound to operate on current at 500 volts, while the 
generators in the powerhouse produce current at 550 to 600 volts, 
the difference being known as the voltage drop. 

Q. Is this an important matter on the automobile where the 
circuits are so short? 

A. It is of considerable importance, particularly in connection 
with the starting motor circuit. The circuits are very short, but the 
initial voltage is likewise very low, so that the percentage available 
for voltage drop is correspondingly limited. For example, a drop of 
one volt in a 110- to 115-volt lighting circuit is negligible, being less 
than 1 per cent, but a drop of one volt in a 6-volt circuit represents 
almost 17 per cent and would accordingly be prohibitive. As poor 


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connections, dirty switch contacts, dirty commutator, and worn 
brushes are apt to increase the resistance to a point where the voltage 
drop is in excess of this, the importance of properly maintaining these 
parts of the system may be appreciated. 

Q. How does the flow of water correspond to the flow of 

A. In both cases, the amount is proportionate to the resistance 
of the outlet and to the pressure back of the current, whether water 
or electricity. In other words, the volume of water that will flow 
depends upon the size of the outlet (the smaller the outlet the greater 
the resistance to the flow) times the pressure back of it. In the same 
way the number of amperes that will flow when the circuit is closed 
depends upon the voltage of the circuit divided by the resistance 
(Ohm's law). For example, the ordinary 16 c.p. carbon-filament 
lamp for a 110-volt circuit has a resistance of 220 ohms, which, 
divided by 110, gives \ ampere as the current that will flow when the 
lamp is switched into the circuit. 

Q. Can the piping system properly be compared with an electric 

A. In practically every way except that of the return required 
for the latter. For example, the opening of a series of outlets in the 
piping system reduces the pressure in proportion to the number 
opened; so in connecting a number of different pieces of apparatus 
in series in an electric circuit, the voltage through each will decrease 
as another is added. It may also be compared with a parallel or 
multiple circuit in that the opening of one outlet does not prevent 
drawing water from another. A break in a main corresponds to a 
short-circuit or a ground in that no water can then be drawn from any 
outlet beyond the break. The comparisons between the piping 
system and the circuit are not exact, owing to the lack of any neces- 
sity for a return in the case of the water piping, but they serve to 
make clearer some of the fundamentals of the electric circuit. 


Q. What makes it possible to generate a current of electricity . 
by mechanical means? 

A. The fact that electricity and magnetism are different mani- 
festations of the same force and that, given one, the other may be 


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produced. Also the fact that they are readily interchangeable, 
i.e., one may be readily converted into the other. 

Q. On what fundamental principle does the generation of elec- 
tricity in this manner depend? 

A. That of induction. 

Q. How is it utilized? 

A. By revolving a coil of wire in the field of a magnet. 

Q. What occurs when this is done? 

A. An e.m.f . is generated in the coil. 

Q. Describe the simplest form of generator. 

A. Such a generator consists of a horseshoe magnet between 
the poles of which a coil of wire is revolved. 

Q. What governs the strength of the e.m.f. or potential, thus 

A. The speed with which the conductor or wire revolves, or is 
said to "cut the lines of force" of the magnetic field. 

Q. How can this potential be further increased? 

A. By winding the coil of wire on an iron core, as the iron 
becomes strongly magnetic and greatly increases the inductive effect. 

Q. What is this simplest form of generator consisting of horse- 
shoe magnets for the field and of a single winding on an iron core 
termed, and for what is it employed on the automobile? 

A. It is known as a magneto and is generally employed for pro- 
ducing the current needed for ignition purposes. 

Q. Can such a generator be directly employed for charging a 
storage battery or for lighting lamps? 

A. No, it cannot be used for charging purposes, since it gen- 
erates an alternating current. Moreover, owing to the small number 
of poles (two), its single winding, and the high speed at which it is 
driven, it produces very little current but a high e.m.f., as this is 
desirable for ignition. It cannot be used for lighting purposes for 
the same reason, i.e., the simple winding produces an alternating 
current with a very perceptible interval between the alternations, or 
cycles, so that a lamp would flicker very badly. As its e.m.f., or 
voltage, is proportionate to its speed and as there is no method of 
controlling it, the lamp would be burned out as soon as the magneto 
was speeded up. 

Q. What are the essentials of this simple form of generator? 



A. The field consisting of the horseshoe magnets, and the arma- 
ture consisting of a soft iron or steel core, usually in the form of an H, 
in the slots of which, the single winding of comparatively coarse wire 
is wound. 

Q. Why is the field of a magneto usually referred to as a "per- 
manent field?" 

A. Because it consists of so-called permanent magnets. Nat- 
urally, they are not permanent in the real sense of the word, but their 
magnetism is constant while it lasts and it decreases only very grad- 
ually under the influence of heat and vibration. 

Q. Why does heat affect the magnetism of the field of a genera- 
tor of this type? 

A. Because a piece of hard steel that is strongly magnetic when 
cold loses its magnetism altogether when raised to a sufficiently high 
temperature. In other words, if heated to a bright red and then 
cooled, it is no longer a magnet, and the steel must be remagnetized. 
Constant vibration has the same effect, but it is much slower. 

Q. Is there any other way of increasing the voltage of such a 
generator besides running its armature at a higher speed? 

A. Yes, by increasing the number of turns of wire in the wind- 
ing, which has the same effect as revolving a single coil at a higher 

Q. How is the current produced by a simple form of generator, 
such as the magneto, conducted to an outside circuit? 

A. Ordinarily, this would be done by means of slip rings, i.e., 
plain bands of copper mounted on the armature shaft with narrow 
copper brushes bearing on these rings, as is the case with large alter- 
nating-current generators. But as the ignition system of the auto- 
mobile is a grounded circuit, one end of the armature winding of the 
magneto is connected directly to the core of the armature, and the 
other is led to a small V-shaped ring or to an insulated stud on the end 
of the shaft against which either a copper or a carbon brush is held 
by a small spring. 

Q. What is the cause of the alternating cycle of the magneto, 
and at what points in the revolution of the armature does it occur? 

A. In revolving in the field of the magnets, the armature passes 
successively from the field of influence of a north pole to one of 
opposite polarity, so that the direction of the e.m.f. is reversed. 



When the armature is in a horizontal position in the field, the e.m.f. 
curve is at zero; as it turns, the edges of the armature core pass the 
ends of the pole pieces of the field, and the e.m.f. rises sharply to a 
maximum as the central line of the core passes the ends of the poles, 
when it is said to be cutting the maximum number of lines of force. 
It drops off again quickly from this point and again reaches zero, 
when the armature is in a vertical position. As its ends come under 
the influence of opposite poles, the curve again rises, but is now in the 
opposite direction, or of opposite polarity. In other words, it passes 
from zero to maximum and back again in every half revolution, or 
180 degrees. 

Q. How can a generator be made to produce a direct, instead of 
an alternating current? 

A. The current is always alternating as generated in the arma- 
ture, but it may be conducted to the outside circuit as a unidirec- 
tional, or so-called direct, current by the addition of a commutator. 

Q. Can such a current be produced by the addition of a commu- 
tator to the simple single-coil winding already mentioned in connec- 
tion with the magneto? 

A. Yes, but as the commutator would have but two parts, the 
e.m.f., while passing in one direction, would be strongly pulsating. 

Q. What is a commutator and how does it convert the alternat- 
ing current produced in the armature to a direct current in the outside 

A. It consists of a number of segments of copper, one for each 
coil terminal of the armature, i.e., two for each complete coil of the 
winding. These segments are insulated from one another, and 
brushes bear at opposite points ofrthe conducting hub thus formed by 
the segments. As the terminals of the armature coils are connected 
to segments that are opposite one another (in the simplest forms of 
winding), and as the brushes, also opposite one another, are set at 
points so that they pass from one segment to another when the fate 
of cutting is at a minimum in the armature winding, their relation to 
the latter is changed each half revolution. In other words, at the 
point in the revolution where the polarity of the e.m.f. generated 
reverses, the relation of the brushes to the winding is also reversed, 
so that the direction of the e.m.f. is accordingly always the same. See 
Figs. 20 and 21. 


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Q. How is the pulsating nature of the direct current thus gener* 
ated overcome? 

A. By adding coils and commutator bars to the armature so 
that new coils come into action before the e.m.f. produced in those 
just preceding them under the brushes has an opportunity to drop 
much below the peak or maximum. Thus, only the peak of the 
wave is utilized, and the e.m.f. of a direct current consists of a series 
of these wave peaks overlapping one another. 

Q. Are permanent magnets used for the fields of all generators? 

A. No, only for those of magnetos. In other types, an electro- 
magnetic field is used. 

Q. What are the advantages of the permanent field for use in 
connection with the magneto? 

A. It is always at its maximum strength, so that the magneto 
generates a powerful e.m.f., even though turned over very slowly. 
Regardless of the speed of the armature, the strength of the field 
remains the same, so that no controlling devices are necessary to 
prevent the armature from burning out, owing to excessive speed. 

Q. What is an electromagnetic field and how is it produced? 

A. It is based on the fact that when a current of electricity is 
sent through a winding surrounding an iron core, the core becomes 
strongly magnetic. It accordingly consists of windings on the fields 
of the generator, in addition to those on the armature. Depending 
upon the particular type of generator in question, either all or only 
part of the current produced in the armature is sent through the 
windings of the field. The latter is then said to be self -excited in that 
it depends upon no outside source. 

Q. Is the self=excited field characteristic of all generators 
except the magneto? 

A. Yes, of all direct-current generators. Large alternating- 
current generators are said to be separately excited, a smaller direct- 
current generator being employed solely for the purpose of rendering 
the fields of the larger machine magnetic. 

Q. What is a series-wound generator, and why is this type not 
used on the automobile? 

A. It is one in which the entire current generated in the arma- 
ture is passed through the field windings. It does not generate until 
a high speed is reached. Its voltage varies sharply as its speed, and 


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it may have its polarity reversed by the battery if its speed drops 
below a certain point, consequently, it is not fitted for charging 
storage batteries. (In fact, the series-wound generator is practically 
obsolete, except for some special uses.) 

Q. What are shunt= and compound-wound generators? 

A. In the former, the windings of the armature and of the fields 
are in multiple, or shunt, so that only a certain amount of current, 
depending upon the difference in the resistance of the outside circuit 
and that of the fields, passes through the windings of the latter. As 
the load and consequently the resistance of the outside circuit 
increases, more current passes through the shunt, and the fields 
become more strongly magnetic, thus increasing the output so that 
the generator is, to a certain extent, self-regulating. 

In the compound type, there is, in addition to the main shunt 
winding on the fields, an auxiliary winding of heavier wire (lower 
resistance) which is connected in series with the armature. As in a 
series-wound generator, the amount of current exciting the fields is 
directly proportional to the speed, more current in proportion passes 
through the compound winding than through the shunt winding as 
the load is increased, and the generator is self-regulating to a much 
greater degree. The compound-wound type of generator is in prac- 
tically universal use on the automobile as well as for general power 
purposes. See Figs. 31 and 32. 

.Q. What is meant by the term "self-regulating" as used in the 
preceding paragraphs? 

A. The generator automatically produces more current in 
response to the demand occasioned by an increase in the load, without 
any change in its driving speed. 

Q. How is this accomplished? 

A. The amount of current produced by the generator depends 
upon the strength of its magnetic field in which the armature revolves. 
The magnetism of this field represents the so-called lines of force. 
The greater the number of lines, or the more powerful they are per 
unit of pole-piece surface, the greater the volume of current that will 
be generated. In practical usage, this is referred to as the magnetic 
flux, or flow, through the armature. By increasing or decreasing 
the amount of this magnetic flux through the armature, the current 
output can be controlled within close limits. 


Q. What is meant by the "load" on a generator? 

A. The lamps, motors, storage battery, or similar apparatus to 
which it is supplying current. 

Q. As the speed of the generator itself does not increase, how 
does it provide for an increase in the load? 

A. By absorbing more power from its driving unit. For 
example, if a generator be operating with only ten 100-watt lamps in 
the circuit, it is requiring approximately one and one-half horsepower 
to drive it. Now, if another group of ten lamps of the same size be 
switched on, the amount of power demanded by the generator of its 
engine will be doubled. This may be very readily demonstrated in a 
rough way by fitting a handcrank to any small automobile generator 
and turning the machine over with one lamp in the outside circuit. 
It will be found very easy to spin the generator very rapidly by hand, 
as practically no resistance is felt. Now connect in the circuit a 
discharged storage battery, and the additional power required to 
turn the machine will at once be very perceptible. 

Q. What are the brushes and what purpose do they serve? 

A. They are strips of copper or carbon (the latter is now almost 
universally used), which serve to conduct the current generated in 
the armature to the outside circuit and to the field windings by 
bearing on the revolving commutator. Except where an additional 
brush is employed for regulating purposes, there is usually one brush 
for each pole of the field, i.e., a bipolar generator is fitted with two 
brushes, a four-pole with four brushes. The brushes are 1 held against 
the commutator by springs. Soft copper embedded in carbon is also 
employed, especially for low-voltage generators, such as the lighting 
generator on the automobile. 


Q. Is there any difference in principle between the electric 
generator and the electric motor? 

A. Fundamentally, they are the same, as is evidenced by the 
fact that either is reversible, that is, an electric generator, when 
supplied with current from an outside source (of the proper voltage, 
of course), will operate as a motor, and a motor, when driven by an 
outside source of power, will generate an electric current. They are 
naturally not interchangeable in practice, owing to differences in 




design and winding. The generator is wound to produce the maxi- 
mum amount of current at a certain voltage with a given horsepower, 
while the motor is designed to produce the maximum amount of power 
with the minimum current. 

Q. What is the operative principle of the electric motor? 

A. That of magnetic attraction and repulsion. 

Q. How is it applied? 

A. As in the generator, both the fields and the armature of the 
motor consist of electromagnets. The brushes and the commutator 
serve the same purpose of reversing the direction of the current 
through the armature coils every time a different pair of commutator 
segments passes under the former. As has already been explained, 
reversing the direction of current flow through the winding of an 
electromagnet reverses the polarity of the magnet itself. To sim- 
plify the illustration, take a bipolar motor with a two-pole armature 
having but a single winding. When the current is switched on, the 
armature is at a 45-degree angle, so that its poles are just under the 
poles of the field. As the commutator causes the current to flow 
through the armature winding in a reverse direction to that of the fields, 
unlike poles will be created. They will attract each other, and the 
armature will revolve a small part of a revolution, until it is directly 
in the strongest part of the field of the influence of the field magnets. 
Just as this point is reached, however, the brushes pass on to new 
segments of the commutator, and the direction of the current in the 
armature coils is instantly reversed. The polarity of the armature 
core is also reversed, so that there are now like poles opposed to one 
another, and they repel, causing the armature to complete another 
part of its revolution, when the former conditions are again estab- 
lished and the armature is again attracted. In a bipolar motor with 
a simple two-pole armature, there would be two phases of attraction 
and repulsion per revolution. In larger motors this is multiplied by 
the number of poles in the field and the number of coils on the 

Q. As an electric motor in running fulfills all the conditions 
necessary for the generation of an e.m.f., what becomes of this 

A. It constitutes what is termed a counter e.m.f. and serves the 
useful purpose of increasing the resistance of the motor when in 

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operation, thus reducing the amount of current necessary to drive it. 
For example, when the motor is standing idle, the resistance of its 
windings is low. It is for this reason that large direct-current motors 
(one h.p. or over) cannot be started without the aid of an outside 
resistance to cut down the starting current, otherwise the armature 
would be burned out. As the armature speeds up, the counter e.m.f . 
generated opposes that of the driving current and accordingly 
increases the resistance. The heating of the windings in operation 
further serves to increase the resistance, as the resistance of most 
metals increases with a rise in their temperature. 

Q. How many types of motors are there, and what type is most 
generally used for automobile starting? 

A. As they correspond exactly to generators, there are the 
same number of types, i.e., series, shunt, and compound wound". 
The series type is almost universally employed on the automobile and 
is also very largely used on trolley cars. 

Q. If the series-wound generator is of so little practical applica- 
tion, how is it that the series-wound motor is found so advantageous? 

A. The same characteristics that are a disadvantage in the 
generator are correspondingly valuable in a motor, which explains 
why generators and motors are not interchangeable in practice, as 
already mentioned. A series-wound machine is essentially a variable- 
speed machine, and this is not desirable in a generator, while it is in a 
motor. The series type of motor has a very heavy starting torque, 
or pull, which increases as the speed of the motor decreases. This is 
exactly what is wanted to overcome the inertia of the gasoline engine. 
Its current consumption falls off very quickly as its speed increases, 
and it has a very liberal overload capacity, being capable of carrying 
loads up to five times the normal, for short periods. 

Q. As the speed of the series motor decreases in proportion to 
the load, what happens when the load is suddenly relieved as in the 
starting of the gasoline motor? 

A. The electric motor tends to race, or run away. 

Q. How is this prevented on the automobile? 

A. The method employed differs in different systems, but, as a 
rule, the starting of the gasoline engine automatically opens the 
starting motor circuit, or means are provided for greatly reducing the 
amount of current it receives the moment the load is removed. 


Digitized by 



Q. Are either shunt- or compound-wound motors used on 

A. They are employed on electric vehicles, but not often in 
connection with the starting systems used on gasoline cars. 

Q. What is a motor-generator, and what is it employed for? 

A. As its name indicates, it consists of two units, a motor and a 
generator, the former having an alternating current, and the latter a 
direct current. It is employed for converting an alternating current 
into a direct current, so that it may be utilized for charging storage 
batteries. The alternating-current supply is used simply for running 
a motor of that type to which is directly coupled a direct-current 
generator. There is no electrical connection between the two 

Q. Are motor-generators ever used on automobiles? 

A. No, but the combination of a direct-current generator and a 
starting motor in one machine, as in the single-unit systems, is fre- 
quently so-called through error. This single unit is variously termed 
a dynamotor and a genemotor to distinguish it from a motor-generator. 

Q. How are the two radically different purposes for which the 
generator and the motor must be designed combined in one machine? 

A. By putting independent windings on the fields and the arma- 
ture, and, in some instances, by employing two commutators at 
different ends of the armature shaft. 


Q. What other method is there of producing an electric current 
besides that of driving a dynamo? 

A. The use of batteries known as primary and secondary cells. 
Q. What is the difference between these two types? 

A. In the primary cell, the current is generated by means of 
the chemical reaction taking place between electrodes of different 
materials in an acid or alkaline solution, one electrode being dissolved 
in the solution as the chemical action continues. 

The secondary cell is the storage battery. This does not generate 
a current of electricity as in the case of the primary cell, nor does it 
actually store electricity as its name would indicate. The passing of a 
current through its elements brings about a chemical conversion of the 
latter, which is reversed when the current flows out of the cell. 



The page numbers of this volume wUl be found at the bottom of the pages; 
the numbers at the top refer only to the section. 

A.C. generators 384 

Ackerman steering construction 92, 93 
Acme torsion spring 195 

Air cushion 198 

Alignment of front wheels 149 

Aluminum, specific resistance of 359 
American Die and Tool Company 

transmission interlocks 50 
American wire gage 367 

Ames equalizing spring 198 

Ampere 355 

Angularity of cone clutch 12 

Annular bearings 72, 148 

Armature cores 389 

Armature windings 388 

Artificial magnets 370 

Axle bearings 147 

Axle pivots, inclining 92 


B.& S. wire gage 




Ball bearings 

147, 148 




27, 54, 72, 147, 240 

Belt drive 


Bevel differential 236 

Bevel gears for final reduction 222 

Bipolar field magnets 396 

Blowouts 331 

Borg & Beck clutch 22 

Bottleneck frame 157 

Brakes 215, 250 

adjustment 259 

cable-operated brakes 256 

cam-action brakes 251, 254 

chain-driven cars, brakes on 252 

Note. — For page numbers see foot of pages. 

Brakes (continued) 
chattering of brakes 262 
double-acting external-contract- 
ing brakes 252 
double brake drum 256 
dragging brakes 250 
dummy brake drum 262 
electric brakes 251, 259 
eliminating noises 264 
engine as brake 251 
external-contracting brakes 251 
function 250 
Hartford brake 259 
hydraulic brakes 251, 260 
inertia of car 250 
internal-expanding brakes 251, 252 
Knox tractors, brakes on 260 
lever-operated braking system 256 
Locomobile car, brakes en 259 
lubrication 259 
operation, methods of 256 
Peerless rear-axle brake 253 
Pierce car 259 
pneumatic brakes 251 
railway-type brake 251 
rear-axle brakes 251 
scissors-action brake 251 
shaft brakes 251 
side-by-side internal brakes 252 
single-acting external-contract- 
ing brakes 251 
stretching brake lining 264 
summary of instructions 343 
Timken brake 253 
toggle-action brake 251, 253 
troubles and repairs 261 
truing brake drums 265 
types 251 


Digitized by 



Brown-Lipe-Chapin M&S differ- 
ential 238 
Brush frame 164 
Brushes 396 
Bucking coil 396 

Cable drives 56 

Cable-operated brakes 256 

Cadillac clutch 19, 26 

Cadillac transmission and hous- 
ing 40 
Cam-action brake ^51, 254 
Camber of front wheels 142 
Cantilever spring 174, 178, 180 
Capacity 379 
Carbon brushes 397 
Carrying capacity of wires 370 
Casing molds for patches 319 
Casing repairs 330 
Casing of tire 311 
Cast axles 143 
Cast-steel wheels 283 
Chain drive 223 
Chain-driven cars, brakes on 252 
Chain four-wheel drive 131 
Chassis group 154 
axles (see Front axles and Rear 

frames (see Frames) 
shock absorbers (see Shock ab- 
springs (see Springs) 
transmission (see Transmission) 
Chemical effect of current 369 

Circuit, electric (see Electric cir- 
Clincher rims 292 

Clincher tires 286, 297 

accessibility 28 

adjustment 28 

bearings 22 

Borg & Beck clutch 22 

Cadillac clutch 19, 26 

coefficient of friction of clutch 

discs 18 

Note. — For page numbers see foot of pages. 


Clutch (continued) 

cone clutch 

11, 12, 13 

contact surfaces 


cork inserts 


cutting new discs 


direct cone clutch 

12, 13, 14 

disc clutch 

11, 13 

Dorris clutch 


dry-disc clutches 


electric clutch 


facing on clutch discs 

18, 19 

female clutch member 


floating discs 


Ford clutch troubles 


function of 


grabbing clutch 


gradual engagement 


gradual release 




Hele-Shaw clutch 


hydraulic clutch 


internal spring 

13, 14 

LaFayette car, clutch on 70 

leathers, replacing 29 

Locomobile, clutch on 20 

lubrication of clutch 18, 27 

magnetic clutch 24 

male clutch member 33 
multiple-disc clutch 13, 16, 70 

operation 24 

Ours car (French), clutch on 20 

pedals 25, 36 

plate clutch 11 
power transmitted by clutch, 

increasing 20 

relation to transmission 38 

release 25 

Studebaker clutch 12 

slipping clutch 28 

spinning 33 

spring pressure 16 

springs, handling 31 

summary of instructions 79 

three-plate clutch 15, 16 

thrust bearing on clutch 27 

troubles and remedies 28, 37 

types 11 


Digitized by 



Clutch (continued) 

Warner clutch 15 

Winton car, clutch on 17, 45 
Coefficient of friction of clutch 

discs 18 

Coil springs 195 
Commercial car (see Truck) 

Commutators 385 

Compound-wound generator 394 

Compound-wound motor 400 

Condensers 379 

Conductors 358, 366 
Cone clutches 11, 12, 13 

Contact surface of clutch 11 

Continuous holding ring rim 298, 305 

Copper brushes 396 

Copper conductors 358 

Copper, specific resistance 359 

Cord tires 291 

Cork inserts on clutch 12, 33 

Coulomb 355 

Counter e.m.f. 400 

Couple-Gear axle 137 

Couple-Gear wheel 136 

Cross-connecting rods 124 

Cup and cone ball bearings 148 

Current 353, 368, 381 

chemical effect of 369 

heating effect of 368 

Cushion tires 278 


D.C. generators 384 

Dayton Airless tire 288 

De Dion dropped rear axle 231 

Delco single-unit system 403 

Demountable rim 298, 309 

Demountable-rim tires 287 

Differential 215, 236 

Disc clutch 11, 13 

floating discs a novelty 20 
greater power transmitted by 

surfaces not plane 20 

hydraulic clutches 22 

metal-to-metal dry-disc type 17 

multiple-disc type 16 

simple type 15 

Note. — For page numbers see foot of pages. 


Disc clutch (continued) 

use of facings 


Warner clutch 


Difference of potential 


Direct cone clutch 

12, 13, 14 

Distance rods / 


"Dolly" for handling truck 

wheels 285 
Dorris clutch 25 
Double-action external-contract- 
ing brakes 252 
Double brake drum 256 
Double cantilever spring 179 
Double-chain drive 223 
Double-coil springs 197 
Double-drop frame 157 
Double shackle 188 
Double-spoke wheel 281 
Double-tube tires 285 
Drag link 120 
Dragging brakes 250 
Driving reaction 226 
Driving shaft 215, 220 
Drop-forged axle 144 
Dropped rear axle 230 
Dry cell 403 
Dry-disc clutches 17, 70 
Dummy brake drum 262 
Dunlop tire 285 
Dynamo (see Generator princi- 
Dynamo-electric machines 397 
Dynamotor 401 


Eddy currents 389 

Elastic wheel 278 

Electric circuit 353 
aluminum, specific resistance 

of 359 

ampere 355 

chemical effect of current 369 

circuits 361, 383 

condensers 379 

conductors 358, 366 

copper, specific resistance 359 

copper conductors 358 


Digitized by 



Electric circuit (continued) 
coulomb 355 

current 353, 368, 369, 381 

difference of potential 354 

electricity and magnetism 372 

electromotive force 357 

formulas 355, 357 

fuses, heating effect on 369 

ground 365, 383 

ground-return circuit 361 

heating effect of current 368 

high-tension ignition cables 361 

horsepower 356 

insulators 360 

iron, specific resistance 359 

Joule's law 368 

kilowatt-hour 357 

lamps, heating effect on 369 

multiple circuit 363 

nonconductors 360 

ohm 355 

Ohm's law 355 

open circuit 362 

parallel circuit 363 

potential 354 

power 382 

power formula 357 

resistance 355, 358, 359, 366, 

368, 381 
series circuit 362 

series-multiple circuit 363 

short-circuits 365, 383 

shunt 364 

shunt circuit 363 

silver, electrical resistance of 358 
single-wire installation for elec- 
tric starter 359, 361 
sizes of conductors 366 
specific resistance of metals 359 
steel, specific resistance of 359 
stranded cables 361 
summary of instructions 404 
temperature coefficient 359 
volt 355 
voltage 354, 380 
voltage drop 359, 380 
watt 356 

Note. — For page numbers see foot of pages. 


Electric brakes 

251, 259 

Electric car springs 


Electric clutch 


Electric drive 


Electric transmission 

38, 56 

Electrical equipment for gasoline 

cars 351 

Electrical principles 352 

electric circuit (see Electric 

induction principles in genera- 
tors and motors (see 
Induction principles) 
magnetism (see Magnetism) 
summary of instructions 404 

Electrically operated gears 51 

Electromagnets 372 

Electromotive force 357 

Elliott front axle 137, 138, 146 

Elliott reversed front axle 137, 

138, 146 
Entz electric drive 57 

Epicyclic gear 38, 54 

External-contracting brakes 251 

Facings on clutch discs 


Female clutch member 


Fergus car, frame of 




Field magnets 


Fierce clutch 


Fifth-wheel front axle 


Final-drive group 




chain four-wheel drive 


electric drive 


four-wheel driving, steering, 

and braking 128 

friction-disc transmission 127 

front-wheel drive 126 

Jeffery Quad four-wheel drive 131 

rear axles 215 

summary of instructions 337 

tires 285 

types of final drive 126, 219 

units in final drive 215 


Digitized by 




Final gear reduction 215 

Flat-plate recoil springs 198 

Flexible frame 161 

Flexible joints 216, 217, 218, 219 

Flexible mounting 156 

Floating discs 20 

Folding steering wheels 119 

Ford assembly, spring tool for 69 

Ford axles, checking up 249 

Ford clutch troubles 32 

Ford final drive 222 

Ford planetary gear 55 

Ford spring 184 

Ford steering gear 111 

Forged axles 144 

Form-wound armature 389 

Ohm's law 355 

power formula 357 

Four-speed gear boxes 41 
Four-wheel driving, steering, and 

braking 128 
electric drive 135 
Frames 154, 155 
bottleneck frame 157 
bracing frames 173 
brush frame 164 
double-drop frame 157 
Fergus car, frame of 162 
flexible frame 161 
flexible mounting 156 
fracture of frame 170 
I-beam frame 156 
kick-up frame construction 154, 157 
Locomobile rear-end construc- 
tion 168 
Marmon car, frame of 162 
pressed-steel frame 156, 158, 161 
rear-end construction 167 
Reo rear-end construction 169 
rigid frame 159 
riveting methods 172 
sagging frame 169 
single-drop frame construction 157 
springs affected by frame con- 
struction 159 
structural frame 156 

Note. — For page numbers see foot of pages. 


Frames (continued) 



summary of instructions 


three-point suspension 


tightening rivets 


troubles and repairs 


truck frames 


trussing frames 






underslung suspension 


unit power plant 


unit type sub-frame 




wood frames 


Friction-disc transmission 


Friction surface of cone clutch 12 

Frictional-plate shock absorbers 194 
Front axles 137 

Front-wheel drive 126 

Full-elliptic springs 174, 176 

Full floating axle 228, 229, 233 

Fuses, heating effect on 369 


G.R.C. wheel 


Gather of front wheels 


Gear faces 


Gear pitch 


Gear pullers 


Gear set (see Transmission) 

Gear-set noise 


Gear troubles 


Gear types 


bevel gears 


helical gears 


herringbone gears 


spiral bevel gears 


spiral gears 


spur gears 


worm gears 


Gearless differential 


Generator, principles of 


Globular worm gear 


Governed friction shock absorber 194 
Grabbing clutch 32 


Digitized by 




Grant-Lee Gear Company trans- 
mission interlock 50 
Grant-Lee three-speed gear box 43 
Gravity-return layout of tire re- 
pair equipment 323 
Ground 365, 383 
Ground-return circuit 361 


Hackett car, gear box in 
Hand wheels, different forms 
Hartford brake 
Hartford shock absorber 
Haywood vulcanizer 
Heating effect of current 
Hele-Shaw clutch . 
Helical gear differential 
Helicoidal worm gear 
Heussler alloys 
High-tension ignition cables 
Hindley worm gear 
Hoadley four-wheel drive 
Homer-Laughlin car 
Hoover shock absorber 
Hotchkiss drive 
Hydraulic brakes 
Hydraulic clutch 
Hydraulic shock absorbers 
Hydraulic transmission 



180, 227 
251, 260 



I-beam frame 

I-beam section of front axle 

Individual clutch 



generator principles (see Gen- 
erator, principles of) 

motor principles (see Motor, 
principles of) 


summary of instructions 

transformer principles 
Inflation pressures 




Inner tube 

291, 327 

Note. — For page numbers see foot of pages. 

Inside and outside method of re- 
pairing blowout 333 
Inside casing forms 321 
Inside method of repairing blow- 
out 332 
Insulators 360, 377 
Interlocking devices on transmis- 
sions 49 
Internal-expanding brakes 251, 252 
Internal-gear drive 232 
Internal spring on clutch 13, 14 
Inverted Lemoine front axle 141 
Iron, specific resistance 359 
Iron core in solenoid 377 
Ironclad field magnets 396 

J.H.S. shock absorber 197 

Jack 241 

Janney-Williams gear 56 

Jeffery Quad four-wheel drive 131 
Jeffery Quad spring bumper 202 

Jigs for producing right size case 

for bearings 68 

Joule's law 368 

K-W road smoother 196 

Kempshall tire tread 287 

Kettles, vulcanizing \ 320 

Kick-up frame 154, 157 

Kilowatt-hour 357 

King car, cantilever spring on 178 
Knox tractor 182, 260 


LaFayette car, transmission and 

clutch unit 70 

Lamps, heating effect on 369 

Laughlin joint 127 

Leaky tire valves 314 

Lemoine front axle 137, 138, 140 

Lever-operated braking system 256 
Lines of force 375 

Lining up axles 247 

Local wedge demountable rim 298 
Localized heat type of vulcaniz- 
ing molds 319 


" Digitized by 





Locomobile car 20, 45, 168, 

, 185, 259 

Motor (continued) 

Lost motion 


dry cell 















series-wound motor 



189, 190 

shunt-wound motor 


steering-gear assembly 


storage battery 




summary of instructions 







M&S differential 


Multiple circuit 


Magnetic clutch 


Multiple disc clutch 

13, 16, 70 

Magnetic meridian 


Multiple field magnets 


Magnetic permeability 


Magnetic substances 





Natural magnets 


artificial magnets 


Noisy bevel gears 


attraction and repulsion 






Non-magnetic materials 

372, 377 



Non-return layout of tire 


Heussler alloys 






Non-skid tire treads 


iron core in solenoid 


Northway cone clutch 


lines of force 


Northway motor 


magnetic meridian 


Northway three-speed transmis- 

magnetic permeability 




magnetic substances 


natural magnets 



non-magnetic materials 

372, 377 

Oakland car, unit power plant of 43 

permanent magnets, making 373 

polarity of magnet 373 

poles of magnet 371 

relation to electricity 372 

repulsion and attraction 371 

solenoids 375 

summary of instructions 408 

Magneto 390 

Male clutch member 12, 33 

Manly truck, shackle on 188 

Marmon car 141, 162, 181 

Metz final drive 224 

Motor, principles of 397 

batteries 403 

compound-wound motor 400 

counter E.M.F. 400 

Delco single-unit system 403 

Note. — For page numbers see foot of pages. 

Ohm 355 

Ohm's law 355 

Open circuit 362 

Ours car (French), clutch on 20 

Overland car 141, 183, 202 

Oversize tires, use of 289 

Owen Magnetic car 57, 252 

Parallel circuit 363 

Parker pressed-steel wheels 279 

Parker rim-locking device 310 

Passive range absorber 194 

Patches 319, 327 

Pedals, clutch - 25, 36 
Peerless car 45, 231, 253 

Perlman rim patents 306 


Digitized by 





Permanent magnets 

373, 390 

Rear axles (continued) 

Petrol-electric drive 


double chain drive < 


Pierce car 


driving reaction 


Plain bearings 


driving shaft 

215, "220 

Plain rims 


dropping rear axle 


Planetary gears 


final gear reduction 


Plate clutch 


flexible joints 216, 217, 

, 218, 219 

Platform springs 

174, 177 

Ford axles, checking up 


Pleasure-car steering wheels 


Ford final drive 


Pleasure-car wheels 

266, 268 

full floating axle 228, 229, 233 

Pneumatic brakes 




Pneumatic shifting system 


internal-gear drive 


Pneumatic tires 


lining up axles 


Polarity of magnet 




Poles of magnet 


noisy bevel gears 




semi-floating axle 

228, 229 



seven-eighths floating axle 


Power formula 


shaft drive 


Power transmitted by clutch, in- 

slip joints 




spring clips, broken 


Premier car, shackle on 


straightening axle 


Pressed-steel axles 


Thermoid - Hardy universal 

Pressed-steel frame 156 

, 158, 161 



Pressed-steel wheels 


three-quarter floating axle 


Progressive gears 







torque rod 



troubles and repairs 


Q.D. tire and rim 

287, 292 

truck internal gear drive 


Quick-detachable rims 

287, 292 

truss rods 





universal joint 

215, 216 

Radial-load bearings 


universal-joint housings 


Radius rod 


Rear-end construction 


Railway car transmissions 


Release, clutch 


Railway-type brake 


Reliner, use of 


Rainer car, shackle on 


Reo car 

169, 253 

Rear axles 


Repairs (see Troubles and reme- 

assembling rear construction 246 


axle carrying load and 


Resistance 355, 358, 366, 368, 381 

228, 229 

heating effect 




of metals 






chain drive 


Retreading vulcanizers 


clutch forms 


Reversed Elliott front axle 



215, 236 

138, 146 

disassembling rear construction 245 

Rigid frame 


Note. — For page numbers see foot of 






Rim 292 
changing Baker demountable 

rim 300 

clincher rims 292 
continuous holding ring rim 298,305 

demountable rims 298, 309 
local wedge demountable rim 298 

Parker rim-locking device 310 

Perlman rim patents 306 

plain rims 292 

quick-detachable rims 287, 292 

rim-locking device 310 

sizes 307 

straight split rim 304 

summary of instructions 347 

transversely split rim * 300 

universal Q.D. rim 295 

wire wheels, demountable rims 

for 309 

Rim-cut repair 333 

Rim-locking device 310 

Ring armature winding 389 

Roller bearings 147, 148 

Roller-chain drive 224 

Rope drives 56 


Sand blisters 331 

Schwartz wheel 370 

Scissors-action brake 251 

Selective sliding gears 39, 41 

Self-excited fields 393 

Self-induction 378 
Semi-elliptic springs 174, 175, 182 

Semi-floating axle 228, 229 

Semi-reversible steering gear 113 

Series circuit 362 

Series generator 393 

Series-multiple circuit 363 

Series-wound motor 400 

Seven-eighths floating axle 228 

Shackles 188 

Shaft brakes 251 

Shaft drive 220 

Shaler vulcanizer 317 

Sheet-steel wheels 276 

Shoe of tire 311 

Note. — For page numbers see foot of pages. 


Short-circuits 356, 383 

Shunt 364 

Shunt circuit 363 

Shunt-wound generator 394 

Shunt-wound motor 400 

Shock absorbers 155 

air cushion 198 

coil springs 195 

flat-plate recoil springs 198 

frictional-plate shock absorbers 194 

hydraulic shock absorbers 210 

overload springs 202 

summary of instructions 210 

Siddeley-Deasy car, cantilever 

spring on 178 

Side-by-side internal brakes 252 

Side-wall vulcanizer 321 

Silent-chain drive 224 

Silver, electrical resistance of 358 

Single-acting external-contracting 

brakes 251 

Single-drop frame construction 157 
Single-wire installation for elec- 
tric starter 359, 361 
Sliding gear 38, 39, 41 
Slip joints 218 
Slipping clutch 28 
Small tool equipment of tire re- 
pair shop 325 
Solenoids 375 
Solid tires 278 
Spark lever 120 
Specific resistance of metals 359 
Spinning of clutch 33 
Spiral bevel gears for final reduc- 
tion 223 
Spring clips, broken 246 
Spring drive 227 
Spring pressure in clutches 16 
Springs 31, 155 
attachment 186 
broken springs 192 
cantilever spring 174, 178 

clutch 31 

construction 190 

double cantilever spring " 179 

double shackel 188 


Digitized by 




Springs (continued) 

ears 190 

electric car springs 185 

Ford spring 184 
frame construction, effect on 

springs 159 

full-elliptic springs 174 

hangers, adjusting 188 

Hotchkiss drive 180 

King car, cantilever spring on 178 

Knox tractor, springs on 182 

leaf ends, forms of 190 

Locomobile car, springs on 185 

lubrication 189, 190 

Manly truck, spackle on 188 

Marmon car, springs on 181 

materials 190 

Overland Four, springs on 183 

platform springs 174, 177 

Premier car, shackle on 188 

Rainer car, shackle on 188 

resetting springs 192 

semi-eUiptic springs 174, 175, 182 

shackles 188 
Siddeley-Deasy car, cantilever 

spring on 178 

sizes 190 

summary of instructions 210 

tempering springs 192 

three-point suspension 183 
three-quarter elliptic springs 

174, 176 

troubles and remedies 190 

truck spring 182 

types 174 

underslinging 187 

Winton car, springs on 183, 190 

Spur and bevel steering gear 100 

Spur differential 236 

Spur gears for final reduction 222 

Staggered spokes 270 

Starting motor, heat generated in 368 

Stearns-Knight car, transmission 

on 46 

Steel, specific resistance 359 

Steel wheels 283 

Steering group 91 

Nate. — For page numbers see foot of pages. 

Steering group (continued) 
Ackerman steering construc- 
tion 92, 93 
axle pivots, inclining 92 
backlash 115 
cross-connecting rods 124 
drag link 120 
folding steering wheels 119 
Ford steering gear 111 
front axles 137 
globular worm gear 100 
hand wheels, different forms of 116 
helicoidal worm gear 100 
Hindley worm gear 100 
lost motion 115 
lubrication 126 
metal-core steering wheel 117 
operation of drag link 120 
pleasure-car steering wheels 117 
removing steering gear 114 
semi-reversible steering gear 113 
spark lever 120 
spur and level steering gear 100 
steering gears 91, 96 
steering knuckles 125 
steering levers 94 
steering rod 120 
steering wheels 116 
summary of instructions 202 
throttle lever 120 
tie rods 124 
troubles and repairs. 115 
truck steering gear 106, 113 
truck steering wheels 117 
wheels, action in turning 93 
Winton steering gear 107 
wooden-rim steering wheel 116 
worm-gear steering gear 101 
Storage battery 404 
Straight-side tires 298 
Straight split rim 304 
Straightening axles 151, 247 
Stranded cables 361 
Structural frame 156 
Studebaker car 12, 27, 232 
Stutz car, transmission on 47 
Sub-frames 159 


Digitized by 





American wire gage 367 

B.& S. wire gage 367 

carrying capacity of wires 370 

comparative strength of steel 
channels and laminated 
wood frames 162 

proportioning of weights in 

building up tread 335 

Temperature coefficient 359 

Templar power plant 26 

Thermoid-Hardy universal joint 217 
Three-plate clutch 15, 16 

Three-point suspension 159, 183 

Three-quarter elliptic springs 

174, 176 
Three-quarter floating axle 228, 

229, 235 
Three-speed selective gear 40 

Three-speeds forward and one 

reverse 71 

Throttle lever 120 

Thrust bearings 27, 147 

Tie rods 124 

Timken brake 253 

Timken front axle 138 

Tire platform for handling truck 

wheels 285 

Tires 215, 285 

bead 312 

blowouts 331 

care of 315 

casing molds for patches 319 

casing repairs 330 

casing of tire 311 

clincher tires 286, 297 

construction 311 

cord tires 291 

Dayton Airless tires 288 

demountable rim tires 287 

double-tube tires 285 

Dunlop tire 285 

gravity-return layout of tire 

repair equipment 323 

Haywood vulcanizer 317 

inflation pressure • 288 

Note. — For page numbers see foot of pages. 

™. Pa 8 e 
Tires (continued) 

inner tube 291 

inner tube repairs 327 

inside casing forms 32 1 
inside method of repairing 

blowout 332 
inside and outside method of 

repairing blowout 333 
Kempshall tire tread 287 
kettles, vulcanizing 320 
leaky tire valves 314 
localized heat type of vulcaniz- 
ing molds 319 - 
new section of tube, inserting 329 
non-return layout of tire repair 

equipment 323 

non-skid tire treads 287 

oversize tires, use of 289 

patches 319^ 327 

pneumatic tires - 285 

punctures 327 

Q.D. tire and rim 287, 292 

reliner, use of 336 

repair 34 g 

repair equipment 315, 323 

retreading 334 

retreading vulcanizers 322 

rim-cut repair 333 

sand blisters 331 

Shaler vulcanizer 317 

shoe of tire 311 

side- wall vulcanizer 321 

single-tube tires 285 

sizes 307 
small tool equipment of tire 

repair shop 325 

straight-side tires 298 

summary of instructions .346, 348 

trouble and remedies 315, 348 

tube of tire 311 

valves 290,313 

vulcanization of tires 315 

vulcanizing patch 328 

Woodworth adjustable tire 

tread 288 

Toggle-action brake * 251, 253 

Torque rod 215,' 224 


Digitized by 




Torque tube 227 

Transformer principle 377 

Transmission 38, 215 

adjustments 54 

American Die and Tool Com- 
pany transmission inter- 
locks 50 
annular bearings, adjusting 72 
bearings 54, 72 
belt drive 56 
cable drives 56 
Cadillac transmission and hous- 
ing 40 
care in diagnosis 64 
cleaning transmission 66 
electric transmission 38, 56 
electrically operated gears 51 
Entz electric drive 57 
epicyclic gear 38, 54 
final drive 215 
Ford planetary gear 55 
four-speed gear boxes 41 
gear faces 78 
gear pitch 78 
gear pullers 63 
gear-set noise 61 
gear troubles 78 
gear types 73 
Grant-Lee Gear Company 

transmission interlock 50 
Grant-Lee three-speed gear box 43 
group 38 

Hackett car, gear box in 43 

heating 62 

hydraulic transmission 56 

individual clutch 38 

interlocking devices on trans- 
missions 49 
Janney-Williams gear 56 
jigs for producing right size 

case for bearings 68 

LaFayette car, transmission on 70 
latest transmissions 38 

lifting out transmission 67 

location 43 

Locomobile transmission 45 

lubrication 53, 72 

Note. — For page numbers zee foot of pages. 

Transmission (continued) 
Oakland car, unit power plant 

of 43 

Owen magnetic transmission 57 

Northway cone clutch 43 

Northway motor 43 

Northway three-speed trans- 
mission 43 
Peerless car, gear box and 

clutch on 45 

petrol-electric drive 56 

planetary gear 38, 54 

pneumatic shifting system 53 

poor gear shifting 64 

pressing gears on shafts 63 

progressive gears 39 

railway car transmissions 53 

relation to clutch 38 

repairs 61, 72 

rope drives 56 

saving balls from bearings 69 

selective sliding gears 39, 41 

sliding gears 38, 39, 41 

spring tool for Ford assembly 69 
stands 67 

Steams-Knight car, transmis- 
sion on 46 
Studebaker transmission 47 
Stutz car, transmission on 47 
summary of instructions 84 
two-speed axle 41 
three speeds forward and 

reverse 71 

three-speed selective gear 40 

troubles and remedies 61, 72 

types 38 

unit power plant 38, 43 

Winton transmissions 43, 45 

Transversely split rim 300 

Troubles and repairs 
brakes 261 

clutch 28, 37 

frame 169 

front-axle 149 

knuckle bolt 153 

rear-axle 241 

spindle 153 


Z , 




Troubles and repairs (continued) 

springs 190 

steering-gear assembly 115 

. tires 315, 348 

transmission 61, 72 

Truck frames 167 

Truck internal-gear drive 232 

Truck overloaded springs 202 

Truck spring 182 

Truck steering gear 106, 113 

Truck steering wHeels 117 

Truck wheels 280 

Truing axles 151 

Truing brake drums 265 

Truing front wheels 149 

Truss rods 244 

Tubular axles 145 

Two-speed axle 41 


Underpans 165 

Underslinging 187 

Underslung suspension 154 
Unit power plant 38, 43, 156, 251 

Unit type sub-frame 159 

Universal joint 215, 216 

Universal-joint housing 243 

Universal Q.D. rim 295 

Valves, tire 



Voltage drop 

Vulcanization of tires 

types of outfits 


Warner clutches 



290, 313 


359, 380 

317, 320 

13, 15 


170, 236 


Westinghouse air spring 198 

Wheel pullers 283 

Wheels 266 

action of in turning 93 

cast-steel wheels 283 

commercial-car wheels 280 

cushion tires 278 

"dolly" for handling truck 

wheels 285 

double-spoke wheel 281 

elastic wheel 278 

G-R-C wheel 275 

Owen Magnetic car 252 

Parker pressed-steel wheels 279 

pleasure-car wheels 266, 268 

pressed-steel wheels 279 

Schwartz wheel 270 

sheet-steel wheels 276 

sizes 266, 307 

solid tires 278 

staggered spokes 270 

steel wheels 283 

summary of instructions 345 
tire platform for handling 

truck wheels 
wheel pullers 

wire wheels 

wood wheels, 
Winton car 
Wire wheels 
Wobbling wheels 
Wood frames 
Wood wheels 

Wood worth adjustable tire tread 
Workstand equipment 


272, 309 

268, 281 
43, 45, 107, 183, 190 


268, 281 

Worm gear for final reduction 222 

Worm-gear steering gear 101 

Hindley worm gear 110 

worm and full gear - 102 

worm and nut 104 

worm and partial gear 101 

worm and worm 107 

Note. — For page numbers see foot of pages. 


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