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GASOLINE TRACTORS

A PRACTICAL PRESENTATION OF TRACTOR
PROBLEMS AND THEIR SOLUTION

CHARLES B. HAYWARD

PKESIDENT AND GENERAL MANAGER, THE STIRLING PRESS, NEW YOKK CITY
MEMBER, SOCIETY OF AUTOMOBILE ENGINEERS

MEMBER, THE AERONAUTICAL SOCIETY

FORMERLY SECRETARY, SOCIETY OF AUTOMOBILE ENGINEERS
FORMERLY ENGINEERING EDITOR, The Automobile

AMERICAN TECHNICAL SOCIETY

CHICAGO

1920

AMERICAN TECHNICAL SOCIETY

COPYRIGHTED IN GREAT BRITAIN
ALL RIGHTS RESERVED

INTRODUCTION

THE huge slow-moving steam tractor has been known in
farmland for many years. It was used by big ranchers
to plow their broad acres and to harvest their grain.
Individual owners also made their tractors sources of revenue
by going around among smaller farmers to thresh their oats
and wheat, the same tractor doing duty for all of the farmers
of a certain district.

<I Within the last few years, however, the development of the
gasoline motor and the dearth of available farm labor has
called for the design of small gasoline tractors sufficiently
inexpensive to make their acquisition a possibility for the aver-
age farmer, and sufficiently flexible as to power to make them
economical for all sorts of operations about the farm, from plow-
ing to running a corn sheller or a feed grinder. These small
tractors, while not having the flexibility of control of the automo-
bile, are easily manipulated and have been found adaptable
to so many farm processes that they have been received by
the farmer with open arms.

*I Of course, the farmer for years has been so thoroughly
acquainted with the automobile that he recognizes the gaso-
line tractor as a friend but nevertheless he has found the
mechanisms, the action, and the management of his new assist-
ant sufficiently full of mystery to make him wish for a manual
at his elbow to help solve his difficulties. His need is par-
ticularly great when the machine stops on its job or when some
part has to be replaced. This situation, coupled with the fact
that the farmer must usually be his own repairman, has cre-
ated a real need for an authoritative book on the subject —
a book which will tell the owner of a tractor just what he
ought to know, will guide him in his selection of a machine,
and will tell him what to do when the ignition fails to work,
when the carburetor is out of adjustment, etc. The author
of this work has had a great deal of experience in the gas
engine field and has made special study of the subject. It
is the hope of the publishers that this little volume will suc-
cessfully fill the place for which it was designed.

A OPTfT 4 f\

CONTENTS

Page

Introduction 1

Relation of Tractor to Automobile 1

Need of Judgment in Selection of Tractor 1

Classes of Tractors 2

Development of Tractor Industry 2

Lack of Standardization 2

Types of Tractors 3

Selecting Tractor '. 4

Work Done on Demonstration No Criterion 4

Financial Return 4

Size of Farm , 5

Size of Tractor 6

ANALYSIS OF TRACTOR MECHANISMS

Tractor Motors 9

Steam Tractors vs. Internal-Combustion Tractors 9

Superiority of Four-Cycle Motor 9

Motor Parts 10

Four-Cycle Principle 10

Pressure and Temperature 12

Grouping of Motor Parts 14

Interrelation of Groups 15

Value of Skilled Operator 17

Valves and Valve Timing : 18

Placing of Valves 18

Valve Details 18

Camshaft and Timing Gear 19

Timing Valves , 21

Lead and Lag of Valve Movement 22

Need of Closely Checking Valves ' . . 24

Sixteen-Valve Engine 24

Fuel Supply System 25

Operating Principle of Internal-Combustion Motor 25

Fuels Available 20

Vaporizing Fuel 28

Proportion of Air to Gas 30

Details of Spraying Process 31

Effect of Increasing Speed 32

Heating Requirements 34

Air and Fuel Balanced. 37

Gasoline and Kerosene Carburetor. . 39

CONTENTS

Page
Fuel Supply System (Continued)

Need for Cleaning Air 41

Tractor Air Conditions Very Bad 41

Types of Air Cleaners 43

Lubricating System 45

Effect of Temperature and Pressure 45

Types of Lubricating Systems 48

Frequent Attention Necessary 56

Cooling System 56

Heat Efficiency of Motors 56

Types of Cooling Circulation 57

Protection of Radiator from Stresses 59

Automobile Experience Misleading 60

Ignition System 61

Importance of Ignition 61

Electric Current 63

Electrical Units 63

Conductors 63

Circuits. 64

Voltage and Amperage 66

Low- and High-Tension Currents 67

Types of Ignition Systems 68

Low-Tension Ignition 68

High-Tension Ignition 69

Mechanisms to Make and Break Circuit 70

Safety Spark Gap 71

Low-Tension Magneto 72

High-Tension Magnetos 76

Spark Plugs 81

Wiring 84

Magneto Impulse Starter 84

Types of Motors 87

Wide Range of Types. 87

Horizontal Engine 89

Vertical Motors 93

Engine Governors 97

Need of Governors 97

Centrifugal Governors ^ 97

Tractor Clutches 103

Functions of Clutches 103

Types of Clutches 104

Friction Drive. . 109

CONTENTS

Page

Tractor Transmissions Ill

Speed vs. Weight Ill

Function of Transmission 112

Wide Range of Types 112

Speeds 113

Heavy Types 116

Intermediate Types 117

Special Types 119

Final Drive 123

TRACTOR OPERATION

General Instructions 125

Tractors Different in Design but Alike in Care Required 125

' Degree of Care Necessary 126

Parts Giving Most Trouble 126

Supply of Spares Necessary 127

Lubrication 129

Motor Lubrication 129

Control System Lubrication ' 133

Engine Parts 134

Engine Bearings 134

Valves 137

Pistons • 142

Carburetor 145

Cooling System • 149

Horsepower Ratings 152

Engine Troubles 153

Running Troubles 162

Engine Noises 166

Clutch and Transmission 167

Housing Tractor 168

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GASOLINE TRACf QRS

PART I

INTRODUCTION

Relation of Tractor to Automobile. At first sight it appears to
be rather a fortunate coincidence that the man to whom the trac-
tor will prove of the greatest benefit is he who has found most
advantage in the automobile — the progressive American farmer.
The automobile has proved a veritable godsend to the farmer, and
there is no question but that he has thoroughly mastered it. He
appreciates that it is a piece of machinery and as such can only be
kept in satisfactory operating condition by proper attention; and
further, that even despite attention it is subject to breakdown at
times. Having acquired this knowledge of an automobile by experi-
ence, the prospective purchaser of a tractor naturally feels perfectly
competent to judge the merits and demerits of the various types
offered and to give the one he buys whatever attention it may
need to keep it operating satisfactorily. This is a mistake and has
proved a more or less costly one to many farmers who have pro-
ceeded on such an assumption. The tractor is driven by a gasoline
or kerosene engine, it has a gear set, clutch, and final drive — all
counterparts of the automobile — but it is not an automobile
any more than an aeroplane or a motorboat is, and the attention
that will suffice to keep an automobile going wih fall far short of
what a tractor requires. Unlike an automobile, the tractor is
always operating at full, or almost full, load. Moreover it oper-
ates for ten, twelve, or even eighteen hours a day under this load.
Its requirements are those of the mogul freight engine rather than
those of the high-speed passenger locomotive.

Need of Judgment in Selection of Tractor. Not every one can
hope to operate a tractor satisfactorily, but the experience of those
who have acquired the many thousand machines turned out in the
last few years shows that, given proper judgment in the selection
of a tractor for the work it is to perform and the right kind cf

GASOLINE TRACTORS

attention ifq. its neexii'ils tyill do all or more than is claimed for it.
Buying & tj-aejtor;4nay be>. likened in some respects to building a
house.' "Maiiy*' t^oplc'-neVer** succeed in building just the housf
they want until they have made two or three attempts. This is
equally true of tractor purchases; many farmers do not succeed
the first time in buying the tractor they should have, but in the
end the value of the experience gained usually offsets its cost.

CLASSES OF TRACTORS

Development of Tractor Industry. According to a recent issue
of a directory of the industry one hundred and thirty-five different
American manufacturers are building over two hundred models of
tractors. This statement holds good only for the time at which it
is written since both the number cf manufacturers in the field and
the number of models the old and the new entrants are turning
out are constantly on the increase. The use of tractors on large
farms dates back almost half a century, but up to less than ten
years ago they were all of the steam-driven type. Their first cost
as well as the expense of maintenance made them practical only
on very large farms where skilled labor is constantly employed.
This bit of history is mentioned merely to emphasize the infancy
of the industry as it now exists, a factor that makes it exceedingly
difficult to classify the product of all the manufacturers in the
field and even harder for the prospective purchaser to make his
selection of a machine. The business of building gasoline- and oil-
driven- tractors only dates back to about 1910, and for the first
five years of its existence its progress was not very rapid. Conse-
quently it is only during the last four years or so that most of the
many manufacturers mentioned have entered the field in response
to the great demand for tractors on the part of the farmers, caused
by the acute shortage of farm labor and the corresponding increase
in wages.

Lack of Standardization. When an industry comes into
existence almost overnight, as in the present instance, every manu-
facturer proceeds along individual lines in the design of his machine
with the result that the divergence in types is almost as note-
worthy as the number competing. The tractor industry now finds
itself in about the same position as did the automobile industry

fc r

5 ^
« »

§ 8

GASOLINE TRACTORS 3

fifteen years earlier in that the machines differ widely in design
and construction, horsepower ratings bear little relation to the
dimensions or speed of the motor, and weights for the same horse-
power are often far apart. There is accordingly an entire lack of
standardization where any of the essentials are concerned though
efforts to remedy this situation by the Society of Automotive
Engineers are already well under way. It is scarcely to be
expected, however, that the recommendations adopted can come
into general use for two or three years at least. Meanwhile, many
thousands of tractors are being turned out annually, and the pro-
spective purchaser must make his selection of a machine from
those offered, since conditions make it impossible to wait for the
perfected tractor to be produced several years from now.

Types of Tractors. Regarded from the mechanical standpoint,
the large" number of machines now being built may be classified in
groups according to some feature of design, such as the type of
motor employed, the method of transmitting the power, the man-
ner of securing traction, and the number of wheels, where the lat-
ter are used. For example, when classified according to type of
motor, there would be a group consisting of those tractors using a
slow-speed two-cylinder engine adapted from stationary-engine
practice, and a second group of those employing a high-speed four-
or six-cylinder motor designed along lines that have been made
familiar on the automobile. When classified according to trans-
mission of power, the tractors using a drive through a clutch,
which are in the majority, would fall in one group and those
employing a friction type of drive in another. On the basis of the
method of obtaining traction we would have a group consisting of
tractors employing wheels, also in the majority, and a group com-
posed of the so-called caterpillar, or tracklaying, type and its
numerous modifications. A subdivision of the class using wheels
can be made to cover three- and four-wheel types sinct many
machines differ chiefly in this respect. As a matter cf fact, sub-
divisions of practically every one of these classes are possible.
For instance, in some three-wheel machines there are two driving
wheels, while in others but one is employed. These numerous
differences are cited merely to point out the great rarge of varia-
tion that exists.

4 GASOLINE TRACTORS

SELECTING TRACTOR

Work Done on Demonstration No Criterion. Involving, as it
does, an investment larger than that of almost any other single
farm machine, the selection of a tractor should be made the sub-
ject of as much study and investigation as the prospective buyer
can possibly give. One of the commonest fallacies in tractor buy-
ing is to judge the merits of the machine by the class of work it
does, the term "work" in this connection being applied almost
entirely to plowing since the latter represents the heaviest service
to which the tractor is put. It should be borne in mind that the
tractor is nothing more than the motive power, and neither its
reliability nor its value as a farm machine can be judged from the
character of the plowing it does on a demonstration. Good or
poor plowing depends entirely upon the plow itself and the methods
used in its handling, so that a poor tractor properly hitched to the
right type of plow and in the hands of a skilled operator will do
better work than the best tractor that can be built will turn out
when handled improperly. The method of hitching the plows to
the tractor governs not only the quality of work turned out but
likewise the amount of power consumed in doing it, granting that
the right type of plow is being used for the soil under considera-
tion. It would be just as sensible to judge the value of a
team of horses by the character of the furrows they turned in
plowing.

Financial Return. It has become customary to criticize Amer-
ican farming methods as compared with European solely upon the
difference in production per acre, the fact that the application of
intensive cultivation by hand labor to very small areas is account-
able for the disparity being lost sight of entirely. American agri-
cultural methods produce more per acre for each man employed
than is grown anywhere else in the world, and this is due solely to
the application of farm machinery to production on a larger scale
than has ever been attempted abroad. This has a direct bearing
on the purchase of a tractor, since the capital required for the lat-
ter must be invested for one of two reasons: either the tractor
will enable its owner to cultivate the same number of acres more
economically, or it will place him in a position to cultivate a
greater number of acres with the same number of "hands."

g£

GASOLINE TRACTORS 5

The impression has been more or less general that the first of
these two reasons, "It will do the work cheaper,'* is the chief one
for purchasing a tractor. Investigations carried out by the Depart-
ment of Agriculture, however, have shown that this reason is not
valid. Taking into account the capital outlay required, the cost of
operation, and the depreciation, and considering the average life of
a tractor as seven or eight years, it has been found that plowing
cannot be done any more cheaply with a tractor than with horses,
but that the use of the tractor does enable the farmer to cultivate
a substantially increased number of acres writh the same number
of men. Out of the large number of farms investigated, a major-
ity of the owners found it necessary to increase their acreage after
purchasing a tractor in order to use their machines most effi-
ciently. In other words, the same crops could not be raised any
more cheaply with the tractor than without it, but much larger
crops could be raised by increasing the acreage under cultivation.
This naturally applies more particularly to small farms, by which
is meant those of 150 acres or less, taking the country as a whole,
since what is considered a small farm in the Middle West would
be thought quite the contrary in New England.

Size of Farm. It goes without saying that a tractor will not
prove a profitable investment on farms of such a size that all the
land available for cultivation may be as easily worked by horses
in the time allowed, which classification would cover all farms hav-
ing 100 acres or less of cultivable land since only a portion of the
total acreage is open to cultivation on any farm. Many farmers
consider the purchase of a tractor on the assumption that its excess
capacity can be taken care of by doing "custom work," or plowing
for neighbors. In a number of cases of this kind that were inves-
tigated the charge made for this work was not sufficient to leave a
profit after deducting the cost of operation and the interest on the
investment, so that the farmer would have been better off without
undertaking this extra work. As a means of paying for the trac-
tor when the owner's farm is not sufficiently large to absorb its
full capacity, this practice did not show a profit that would war-
rant the investment in a tractor, since, as before stated, the
charges were too low to cover the cost of operation, while
increasing the rates to a point that would leave a profit would

6 GASOLINE TRACTORS

result in a falling off in the demand as the renter could do the
same work for considerably less with horses.

Judging from the results of the investigations in question, it
will not pay the owner of a 150-acre farm of which not more than
100 are cultivable to invest in a tractor unless he can add from 20
to 50 acres to that under cultivation. This, of course, is a general
statement that may be subject to modification in numerous
instances where specially favorable conditions make the use of a
machine advantageous. But this statement as well as the pre-
ceding matter is intended chiefly to emphasize to the prospective
purchaser of a tractor the fact that it is unwise to make the invest-
ment required in anticipation of doing the same amount of work
much more economically than it can be performed with horses.

Size of Tractor. First cost is naturally the chief item con-
sidered in the purchase of a tractor, and in this connection true
economy is to be found in the selection of a machine that is not
only of good quality, properly designed and well built for the
work it is to do, but that likewise has ample capacity to handle it
without overloading. It will prove as expensive in the long run to
pay for a good small machine that must be overloaded to do the
work required as to buy a cheap machine of any size. In either
case the repair bills and the time lost through delays at the height
of the season are apt to make the buyer regret his choice, if, in
fact, he is not led to condemn tractors altogether. In this con-
nection, however, the skill and experience of the operator are fac-
tors which have a very important bearing on the successful use of
the machine and largely govern the amount of time that it is out
of service due to breakdowns. This is dwelt upon at greater
length in later paragraphs.

Tests have demonstrated that at the maximum speed of plow-
ing recommended for all tractors, that is, 2J to 2J miles per hour,
a two-gang plow will not cover much more ground in a day of ten
hours when drawn by a machine than when pulled by horses. In
other words, the advantage of the tractor-drawn two-gang plow
over horse work is so small that it usually does not pay to buy a
machine whose maximum capacity is two plows. Whether it be a
tractor or any other type of machine, it is not good practice to
depend upon running it at its maximum capacity continuously.

BORING THREE-WHEEL TRACTOR WITH FORWARD DRIVE AND
UNDERSLUNG PLOWS

HEAVY THREE-WHEEL TYPE OF TRACTOR

GASOLINE TRACTORS 7

The machine will not do as good work and it will be much more
subject to frequent breakdown than where it has power in reserve
to meet emergencies that will seriously overload a machine that is
already working at its full output.

The number of plows that any given machine is capable of
pulling depends upon so many other factors besides its power rat-
ing that it is often misleading to term a tractor a two-, three-, or
four-plow machine, as the case may be. The depth of the furrow,
the character and condition of the soil, and the method of hitching
all influence this to such an extent that a machine capable of pull-
ing three plows under favorable conditions might make a very
poor job with two where the soil conditions were not so good or
the plows were not properly hitched. ,

Margin of Safety Needed. It should be borne in mind that
any machine will give the most satisfactory service and have the
longest useful life when operated continuously at not more than 75
per cent of its rated capacity. Expense incident to delays as well
as the cost of repairs will accordingly be minimized when a
machine larger than is actually required is selected and is operated
at less than its full capacity. Experienced tractor operators have
proved this in many instances by investing in four-plow machines
and pulling but three plows. It does not pay to load a machine
to its limit since it cannot carry such a load continuously and give
satisfactory service, so that in selecting a tractor the chief points
to bear in mind are not to buy a lightly or cheaply built machine;
and not to select a machine so small that it can only do the work
required by working continuously at full load.

Power for Belt Work. While plowing constitutes more than
one-half the work for which the tractor is required, it would
pay few farmers to invest in a machine for that purpose alone.
All tractors are designed to be used as stationary power plants as
well, and one-third or more of the service demanded of them con-
sists of driving other machines, such as threshers or ensilage cut-
ters, or, as it is usually termed, belt work. Unless a machine has
ample power for this, it will not be found satisfactory since there
is usually a tendency under such conditions to load it to the stall-
ing point and when a cutter has been "choked down," much val-
uable time is lost in getting it under way again.

8 GASOLINE TRACTORS

A tractor that is not powerful enough to do all the work
required of it is not likely to prove a satisfactory investment,
though an error may also be made by going to the other extreme
and selecting a machine of such a size that it is too expensive to
operate on many of the jobs that a tractor of the proper size
would perform economically.

Factors Governing Capacity. Why a machine that will pull
three plows very satisfactorily under some conditions will with
difficulty do good work with only two bottoms in other locations
will be readily apparent from a consideration of the difference in
drawbar pull required for plowing different soils. The average
resistance of soils is given approximately in Table I.

While the figures in Table I have been drawn from experience,
the draft of a tractor plow can only be approximated, since the
condition of the plow itself and the method of hitching are of the
greatest importance. The figures given are based upon the sup-
position that the plow is clean, sharp, and properly hitched so as
to cut easily. When a plow is dull or does not scour well, the
power required to draw it will be substantially increased. This is
equally true when a plow is not leveled or is out of line in any way.

The draft likewise increases in proportion to the grade and
the figures given are based upon plowing on level ground. For
each 1 per cent rise in grade, that is, for each foot of vertical lift
in each 100 feet of horizontal travel, 1 per cent of the combined
weight of the tractor and the plows must be added to the draft.
For example, assume a tractor weighing 5000 pounds and hauling
four plows each weighing 250 pounds, making the total 6000 pounds:
the maximum draft of the four plows in corn stubble, plowing 6
inches deep, would be 3200 pounds, to which it would be necessary
to add 60 pounds for each 1 per cent increase in grade. Even on
rolling prairie land, which is ordinarily thought of as being level,
the dips and hollows often represent 10 per cent grades for short
distances, and in this case they would necessitate adding 600 pounds
to the draft required.

When planning to buy a tractor to do certain work, keep the
figures given in the table in mind; consider the character of the
soil, the grades, the depth of the furrow, and the horsepower rat-
ing of the machine desired — and it is always well to discount that

GASOLINE TRACTORS

TABLE I
Average Resistance of Soils

Soil

Pounds per
Square Inch

6 Inches
Deep

8 Inches
Deep

Sandy loam

4-6

600- 800

750- 950

Corn stubble

700- 800

900-1000

Wheat stubble

800- 900

1000-1100

Light clay

800-1200

1000-1400

Medium clay

900-1400

1200-1500

Heavy clay in good plowing condition

1600-2000

1800-2100

Sod or heavy clay, medium moisture

2500-3000

2700-3100

Gumbo — dry, hard

2600-3200

2800-3300

horsepower rating somewhat. It will also pay to keep these
figures in mind when the over-enthusiastic salesman begins to make
claims.

ANALYSIS OF TRACTOR MECHANISMS

TRACTOR MOTORS

Steam Tractors vs. Internal=Combustion Tractors. Although
tractors have been used in this country for almost half a century,
they were all steam driven until less than ten years ago, so that
the present widespread and rapidly increasing adoption of the
tractor is due to the remarkable development of the internal-
combustion motor, which, in turn, is largely the result of the great
strides the automobile industry has made since 1900. The present
work is accordingly confined to tractors with such motors since,
although steam tractors will continue to be used on some of the
very large farms on which they have been employed so long, they
are not available to the average purchaser of a tractor and, at
best, it will be only a matter of a comparatively few years before
they will have been displaced by the internal-combustion type in
most parts of the country.

Superiority of Four=Cycle Motor. The experience of the auto-
mobile manufacturer as well as that of the stationary oil-engine
builder has demonstrated that of the several types of internal-
combustion motors that may be used that based upon the so-called
four-cycle method of operation combines the fewest drawbacks
with the greatest number of advantages and is accordingly the

10 GASOLINE TRACTORS

most practical for general use. The two-cycle motor has never
proved successful owing to its inefficiency where fuel consump-
tion is concerned, while other types involve the use of excessive
weights for the power generated.

Motor Parts. Assuming the motor to have but one cylinder,
a four-cycle motor consists of a cylinder, inlet valve and exhaust
valve, piston, piston rings, piston pin, connecting rod, crankshaft
and bearings, flywheel, camshaft, valve springs and crankcase.
Its accessories are a carburetor (or fuel-mixing device), magneto or
other method of generating electric current, spark plug for igniting
the fuel, lubricating system, cooling system, and the necessary
piping for supplying lubricating oil and for conducting the cooling
water between the cylinder jackets and the radiator, the fuel mix-
ture from the carburetor to the combustion chamber of the cylin-
der, and the exhaust gases away from the latter after they have
been burned. A circulating pump may or may not form a part of
the cooling system according to the method of circulation employed.
These auxiliaries, plus a fan to assist in the cooling of the water or

011 in the radiator of the cooling system, complete the motor and
the addition of any number of cylinders only involves the duplica-
tion of those parts directly attached to or working in the cylinder,
such as valves, pistons, and connecting rods with, of course, the
provision of an additional crankthrow on the crankshaft for each
additional cylinder.

Four=Cycle Principle. Intake Stroke. The operation of the
motor is based upon a cycle, or recurrence of operations, consisting
of four distinct parts. Starting with the piston at the upper dead
center, the first of these operations is the intake, or suction,
stroke. The inlet valve has been opened through the revolution of
the camshaft bringing the cam in contact .wjth the valve tappet
and raising the valve off its seat, Fig. 1. The piston is a gas-
tight fit in the cylinder, being sealed by the piston rings, which
press out against the cylinder walls, and by the presence of a
film of lubricating oil between the piston and the cylinder. The
downward travel of the piston accordingly creates a partial vacuum
(negative pressure, or less than atmospheric) in the cylinder, and
the atmospheric pressure (14.7 pounds at sea level), acting upon
the liquid fuel in the carburetor, forces the liquid up through the

GASOLINE TRACTORS

spray nozzle of the carburetor and also draws a predetermined
volume of air up through this spray, thus forming a fuel mixture
which is forced into the cylinder. The action of the piston on
this first part of the cycle is exactly the same as that of a pump
in drawing water out of a well. The water is forced up into the
pump, following the plunger owing to the decreased pressure in the
pump barrel caused by the
stroke of the plunger and to
the outside pressure of the air
on the surface of the water.
Compression Stroke.
When the piston reaches the
limit of its travel, or lower
dead center, the inlet valve
closes and the piston in rising
then compresses the fuel mix-
ture against the head of the
cylinder, the valves also being
gas tight. This is the second
part of the cycle, or the com-
pression stroke, and gives to
the fuel mixture what is known
as the initial compression. This
stroke has an important bear-
ing on the power output of the
motor since it renders the com-

bustion of the fuel more rapid
and complete and also in-
creases the pressure developed

when the Charge is fired. The Figs- 1-4- Strokes of Four-Part Cycle: 1. Intake;
^ ^ f & t m 2. Compression; 3. Power; 4. Exhaust

initial compression used in the

average gasoline motor ranges from 50 to 80 pounds per square inch,
and the higher it is, the more power the motor develops, other
factors such as cylinder dimensions and number of cylinders being
the same. In the case of gasoline, however, this initial pressure
is limited to 90 pounds per square inch since the heat generated
by compression above that point would cause the ignition of the
mixture. Tn kerosene, alcohol, or low-grade fuel engines, it may

12 GASOLINE TRACTORS

be much higher, but in this case a compression release must be
fitted to the engine in order that it may be turned over by hand
for starting.

Power Stroke. The third part of the cycle begins with the
firing of the charge by the passage of a spark at the plug, and
the piston then starts downward on the power stroke. Just before the
piston reaches the lower dead center on this stroke, the exhaust
valve is lifted by the camshaft and the remaining pressure in the
cylinder, which cannot be utilized for driving the piston, is allowed
to escape. A very large part of the heat value of the fuel is
wasted in this manner through the exhaust, but the drop from the
very high pressure at the moment of ignition is so rapid that no
advantage is to be gained from lengthening the stroke beyond a
certain point in an attempt to utilize a greater percentage of the
pressure.

Exhaust Stroke. The following upward movement of the pis-
ton is termed the exhaust stroke and serves to clear the cylinder of
the remaining burned gases in preparation for the succeeding suc-
tion stroke, which recommences the cycle. Although it is one of
the three idle strokes of the four-cycle method of operation, the
exhaust stroke is quite as important as those which precede it
since, unless the cylinder is swept clear of the burned gases of the
previous explosion as completely as possible, a volume of dead gas
is left to occupy space which should be filled with fresh fuel and
the amount of power developed on succeeding strokes is reduced
in proportion. This is one of the chief defects of the two-cycle
method of operation, in which compression immediately follows
the power stroke, there being no exhaust stroke or suction stroke.
As a result, a considerable percentage of the cylinder space is
always filled with burned gases and the time available for the
power stroke is so short that part of the fresh gas escapes unburned.
In the four-cycle method, upon the completion of the exhaust
stroke, the exhaust valve closes and the inlet valve opens, begin-
ning a new cycle. The relative positions of the piston and the
valves during the compression, power, and exhaust strokes are
shown in Figs. 2, 3, and 4.

Pressure and Temperature. While even the most skilled
operator of a traction engine need not be conversant with the

GASOLINE TRACTORS 13

intricacies of its design nor with the scientific aspect of its opera-
tion, a knowledge of what goes on inside the cylinder will be
found an aid to a clearer understanding of the engine itself and
the principles on which it works. The internal-combustion motor
is a heat engine pure and simple, and each part of its cycle is
attended by an increase or decrease in pressure and temperature.
One is a function of the other, a given degree of pressure resulting
in an equivalent rise in temperature, and this fact is taken advan-
tage of in determining the pressure and the temperature in the
cylinder by means of an indicator, the use of which need not be
described here since it is only used by designers in the shop.

Range of Pressure and Temperature. Some idea of the great
range of pressure and temperature inside the cylinder during but
two parts of the cycle, the compression and power strokes, may be
gained by assuming that the motor is operating on a summer day
with the surrounding temperature at 70° F. The temperature of
the entering mixture will then be raised to approximately 100° F.
or more through the use of hot air in forming the fuel mixture by
taking the air supply from a "stove" attached to the exhaust
manifold or by using exhaust gases direct from the engine and
also through having a water jacket surrounding the intake mani-
fold. Without these heating devices the mixture would be con-
siderably cooler than the atmosphere since the conversion of the
liquid fuel into a vapor is attended by the abstraction of heat
from the air. Assuming that the engine has been running, the
end of the previous exhaust stroke leaves the interior of the
cylinder at a temperature of approximately 260° F. and the incom-
ing mixture is further heated by contact with the cylinder walls
and the piston head. At the moment of intake the pressure in the
cylinder is slightly less than atmospheric. During the compression
stroke this pressure is raised to 50-85 pounds, depending upon the
amount of initial compression given, and the temperature rises to
a point between 800° and 900° F. Upon the gases being ignited,
their tremendous expansion in the confined space raises the pres-
sure to 225-250 pounds per square inch with an increase in tem-
perature ranging from 2500° to 4000° F., depending upon the
character of the fuel used. This pressure decreases very rapidly
as the piston moves outward on the power stroke, the so-called

14 GASOLINE TRACTORS

terminal pressure, that is, the pressure at the end of the stroke
when the exhaust valve opens, reaching 40 to 50 pounds with a
temperature of approximately 1000° F. The exhaust stroke
lowers the pressure to approximately that of the surrounding
atmosphere with a decrease in temperature that is governed to some
extent by the length of time that the engine has been running.

Effect of High Temperature. The extreme range of tempera-
tures inside the cylinder should impress upon the operator of a
tractor engine the necessity for prompt attention if anything goes
wrong. For example, in the presence of such great heat as is
developed by the explosion it will be evident that failure of the
lubrication or of the cooling system can cause serious damage in a
very brief period. Pistons will score and scratch the cylinder
walls, valves will warp, . bearings will be burned out, and finally
the pistons will bind hard and fast, all in the short space of a few
minutes. In fact, five minutes will suffice to cause damage, the
repairing of which will take a week and will represent a bill of
three figures.

Grouping of Motor Parts. Mechanical Group. The parts nec-
essary to a four-cycle motor, whether of one or several cylinders,
have already been outlined. Upon studying these, it will be
apparent that they may be divided into groups and that each
group has as its object the carrying out of a certain function in
the operation of the motor. The foundation of all the groups is
naturally the chief mechanical group consisting of the cylinders,
valves, pistons, connecting rods, crankshaft, camshaft, crankcase,
and flywheel. The functions of this group are to provide a
container in which the fuel may be compressed and ignited and
moving parts against which the force of the explosion may act —
first, to produce linear motion in the stroke of the piston and, sec-
ond, to convert that motion into rotary motion at the crankshaft.

Auxiliary Groups. All the other groups really consist of
auxiliaries, such as the carburetor, heating devices, and intake and
exhaust manifolds, designed to mix the fuel with the proper pro-
portion of air, warm it, conduct it to the cylinders, and lead it
away from the latter "after it has been burned. These parts con-
stitute the second group, or fuel-supply system. The third group
consists of the apparatus for igniting the fuel in the cylinders and

GASOLINE TRACTORS 15

is represented by the magneto (or other method of generating
electric current), the spark plugs, the connecting cables, and any
distributing or timing devices necessary when a battery instead of
a magneto is employed. The fourth group is represented by the
lubricating system, the function of which is to supply oil to all
the moving parts; while the fifth group is the cooling system, con-
sisting of the water jackets of the cylinders, the pump, the radia-
tor, and the piping connections. On the traction engine there are
further auxiliaries not necessary on an automobile engine, namely:
the governor and the air cleaner. A large part of the work of the
tractor consists in serving as a stationary power plant, and while
doing belt work it is necessary that a steady engine speed be
maintained under a wide range of load. Unless the engine were
automatically governed under such conditions, it would stall when
the load was increased and race when the load was relieved; and
racing would be dangerous to the engine itself owing to the great
stresses set up by the high speed. While not constituting a group
in itself, the governor may be included in a further group consist-
ing of the control system, in which the throttle and the spark
levers represent the hand control, and the governor the automatic
control of the engine.

Interrelation of Groups. It will be apparent upon a little
study of these different groups, or systems, that all are equally
essential to the operation of the motor and that precedence cannot
be accorded to any one as compared with the others since the
failure of any one would prevent the functioning of the rest. An
understanding of the relations that these groups bear to one
another will go a long way toward making clear the principles on
which the engine operates and also the manner in which the differ-
ent systems must work together in order that it may run satisfac-
torily. The interdependent functions of the groups are considered
at some length in the following paragraphs.

Mechanical Group. Unless the pistons are free to move in the
cylinders and the crankshaft and the connecting rods on their
bearings, no movement can result. This free movement of the
pistons and other working parts is entirely dependent upon the
lubricating system maintaining a constant supply of oil on all con-
tacting surfaces. But unless the cooling system continues to

16 GASOLINE TRACTORS

function properly, the fact that the lubricating system is working
will not keep the motor running since the oil will be burned up on
coming in contact with the cylinder walls owing to the high tem-
perature inside the cylinder.

Fuel-Supply System. Air must be drawn through the carbu-
retor and mixed with the spray of liquid fuel issuing from the
carburetor nozzle, but this cannot be done unless the inlet valve
of the cylinder opens just before or when the piston reaches upper
dead center on the exhaust stroke, as otherwise there will be no
difference in pressure between the inside and the outside of the
carburetor and no suction will result. Nor will the admission of a
charge to the cylinder be effective unless the inlet valve closes
when the piston reaches or just after it passes lower dead center
on the upward stroke as otherwise, instead of being compressed ready
for firing, the fuel mixture would again be forced out of the cylinder.

Ignition System. Movement will naturally cease after the
admission of a charge unless the electric spark takes place at the
proper moment to fire that charge in order to produce the power,
or third, stroke of the cycle. The entire failure of the spark will
prevent further operation; its occurrence too early will stop the
engine by driving the piston down in the reverse direction before
it has completed its stroke on compression; and its occurrence too
late will cause a substantial proportion of the power to be wasted
although the motor will continue to operate. After the completion
of the power stroke the mechanical system again enters since,
unless the exhaust valve opens near the end of this stroke, the
burned gases will remain in the cylinder and when the inlet valve
opens, they will be blown back through the carburetor owing to
the terminal pressure of 40 to 50 pounds per square inch remain-
ing in the cylinder at the end of the power stroke just before the
exhaust valve opens. Owing to the high temperature of these
gases they may ignite the liquid fuel in the carburetor if blown
back through it. This is known as a back fire, and while failure
of the exhaust valve to operate is not as common a cause as either
too lean or too rich a mixture, it is evident that back fire must
invariably follow unless the exhaust valve does open.

Summary of Operation. Continued movement of the mechani-
cal parts of the motor is dependent upon the working of the lubri-

GASOLINE TRACTORS 17

eating system. Lubrication fails unless the cooling system does its
part to keep the temperature down to a point where the move-
ment of the parts in contact is possible, as otherwise the oil is
burned. Unless the inlet valve opens at the right time, the car-
buretor cannot supply a fuel mixture to the cylinder, while a
failure of the electric spark to ignite this mixture at the proper
moment renders the admission of the fuel supply useless. Failure
of the exhaust valve to permit the escape of the burned gases
from the cylinder stops further operation by preventing the admis-
sion of a fresh charge.

Value of Skilled Operator. It is necessary to take up each of
these systems in detail and learn the principles upon which its
operation is based in order to understand more clearly the manner
in which they must co-operate to produce satisfactory running of
the engine and also in order to recognize the symptoms at once
when anything goes wrong and to know the remedy to apply to
keep the engine going and avoid laying up the machine at the
time when it is most needed. In the numerous investigations
undertaken by the Department of Agriculture, some of which
have been referred to, it was brought out in a most striking man-
ner that in the majority of cases where repair bills were lowest
and the most satisfactory service was obtained from the tractor,
it was due in very large measure to the fact that a skilled
operator was on the job.

It has not been a very uncommon thing in the past for manu-
facturers to advertise that their machines can be driven by a child.
So can a big mogul freight locomotive be run by any boy with
strength enough to pull the throttle, but no railroad company
would ' entrust valuable machinery to the care of a boy even were
the danger of collision entirely absent. A tractor cannot be run
satisfactorily by a boy or a girl, nor can it be so run by a man
unless he takes the trouble to acquaint himself with its principles
of operation instead of trusting to luck and experience to acquire
the necessary information haphazard. In other words, he must
qualify as a skilled operative by familiarizing himself thoroughly
with the sequence of operations responsible for the working of
the motor and the principles upon which those » operations are
based.

18 GASOLINE TH ACTORS

VALVES AND VALVE TIMING

Placing of Valves. By referring to the description of the four-
cycle method of operation, it will be seen that it is necessary to
draw a fuel charge into the cylinder on one stroke, compress it on
the second stroke, .fire it on the third, and exhaust the burned
gases on the fourth to complete the cycle. There must accordingly
be valves to control the entrance and escape of the gases, and
these valves must open and close at certain intervals with relation
to the rest of the cycle. The placing of these valves depends upon
the type of motor, of which there are three in general use, namely:
the L-head motor, in which the valves are all on one side; the
T-head motor, in which the inlet valves are placed on one side and
the exhaust on the opposite side; and the valve-in-head type, in
which the valves are located directly in the cylinder heads.

Valves in L-Head Motor. The L-head motor forming the
power plant of the Fordson tractor is shown in Fig. 5 in phantom
to bring out the details of the valves and valve-operating gear.
In a motor of this type all the valves are placed on the same .side
of the motor so that in the line of eight valves an inlet and an
exhaust alternate. The operation of the valves may be traced
through their entire range of movement in this illustration by
noting their positions in the different cylinders. Cylinder 2, for
example, is on the first stroke of the cycle, the intake stroke.
The inlet valve is accordingly open and the exhaust valve closed.
Cylinder 1 is shown on the compression stroke, during which both
valves remain closed. This is also true of the explosion stroke, as
indicated by cylinder :>. On the fourth stroke of the cycle the
exhaust valve opens to discharge the burned gases into the air, as
shown by cylinder 4. (The cylinder numbers mentioned hen-
refer to the cylinders counting from the forward end and not to
the numerals shown on the illustration.)

Valve Details. The valves used on automobile and tractor
motors are variously referred to as niHxhrnuni and jx>i>}><'f valves,
the former name referring to their shape and the latter to their
method of operation. The valve proper counts of a head and a
stem, and as the valve is subjected to high temperatures, it is
either made of cast iron welded to a steel stem or i> a piece of
nickel steel or other heat-resisting metal. Inless some expedient

GASOLINE TRACTORS 19

of this nature is employed, the valve heads are apt to warp under
the terrific heat, this being particularly true of the exhaust valves.
The stem passes down through a guide drilled and reamed in the
cylinder casting itself, and below the point where it leaves this
guide the stem is surrounded by a heavy helical spring. This
spring is held against the guide at its upper end and against a
washer at its lower end. A key passing through a slot in the valve
stem itself holds this washer in place. The valve is accordingly
held down on its seat by a strong spring, and it is the pull of this
spring that returns it to its seat with a snap, or pop, after it has
been opened. The inch or so of the valve stem extending below
the spring washer contacts with the valve push rod when the latter
is lifting the valve off its seat, but in order that the valve may
come down squarely on its seat when closing, the valve stem
and push rod should not be in contact normally. This distance,
or clearance, that must exist between the valve stem and the
valve push rod is not indicated in the illustration since, in this
case, the valve push rod also acts to a -certain extent as a lower
guide, the valve stem entering its upper end for a short distance.

Camshaft and Timing Gear. At its lower end the valve push
rod rides on a cam, and the position of this cam with relation to
the camshaft determines the point at which the valve will open
and close. There is, of course, a cam for each valve, and as their
positions must remain absolutely fixed, they are usually drop-
forged in one piece with the camshaft itself. While Fig. 5 shows
all the details of the valves and valve gear of an L-head motor, it
must be borne in mind that every manufacturer has his own
designs and standards. For example, in most motors a cam fol-
lower is introduced between the valve push rod and the cam in
order to minimize the friction. This usually takes the form of a
fork which is in a guide of its own and has at its lower end a
roller which rides on the face of the cam.

The inner end of the camshaft carries a gear known as the
timing gear in that its position with relation to the smaller gear
on the crankshaft, from which it is driven, determines the time at
which all the valves open and close. In. a T-head motor there -are
two camshafts and two timing gears, and there are also usually
additional gears for driving the circulating pump and the magneto,

GASOLINE TRACTORS

GASOLINE TRACTORS 21

which make the timing-gear end of the average motor look very
complicated to the layman. In the motor shown in Fig. 5 there is
but a single timing gear, and it also carries the ignition timing
cam which determines the occurrence of the ignition spark in the
different cylinders. This is marked Comm. Roller on the illustra-
tion. Just below the timing cam will also be noted zero marks on
the time gears; these are check marks to enable the gears to be
reassembled in the proper relation after a motor has been taken
down for repairs. The gear on the crankshaft is but half the size
of the camshaft gear since each cylinder has but one power stroke
for every two revolutions. There are two power strokes per
revolution in a four-cylinder motor, and the camshaft must
accordingly be driven at half the speed of the crankshaft in such a
motor.

Timing Valves. In a motor making 1000 r.p.m. (revolutions
per minute), 2000 strokes or reciprocating mqvements of the
pistons must take place in sixty seconds, so that the entire time
consumed in making each stroke at this speed is three-hundredths
second. A full realization of what an exceedingly short period
this is in which to perform any mechanical operation should make
it unnecessary to emphasize either the need for accurately timed
valves to ensure an efficient running motor or the necessity of
closely watching all parts of the valve gear to take up any lost
motion caused by wear, since very little slack is required to cut
down the effective opening of the valve. For example, assume
the maximum lift of the valve from its seat to be J inch plus the
clearance of ^V inch provided between the valve stem and the
tappet to permit the valve to seat positively. Then if wear or
lack of adjustment be permitted to increase this clearance to y^
inch, the valve can only lift A inch, so that the effective opening
is reduced 12 J per cent for every thirty-second of an inch lost
motion between the valve tappet and the valve stem.

It is nothing unusual to see automobiles brought to the
repair shop with so much clearance between their valve tappets
and stems tha,t the valves barely leave their seats when the cams
come around. A tractor motor would not be of much service in
this condition since it would not develop enough power to carry
its load. If it were not for the fact that usually in driving an

22 GASOLINE TRACTORS

automobile only a very small fraction of its power is used it
would be impossible to keep a motor running after it gets in such
a condition. A knowledge of the principles of automobile opera-
tion will be an aid to the tractor operator but he will do well not
to attempt to apply them literally to tractor handling since they
fall far short of what is needed to keep a tractor running.

In designing a motor, both the contour, or outline, to be
given the cams and their position on the camshaft are fixed, and
the finished camshaft is a single piece of steel the cam faces of
which have been ground to a high degree of precision. In timing
a motor, it is accordingly only necessary to time the valves of
one cylinder as the others must of necessity also be correct. This
process is made very simple on the Ford son motor, since it is
accomplished merely by the correct meshing of the timing gears.
\Yhen the two zero marks on the driving and the driven gear
coincide the camshaft is in the proper position to open the valves
of all the cylinders in the correct order. This, of course, has
nothing to do with the proper adjustment of the tappet clearance,
which must be looked after at each valve.

Check! tiff I'ahe Timing. A closer check is usually considered
necessary than is afforded by the meshing of the timing gears
just mentioned, and to provide this, the necessary data is marked
on the flywheel of the motor while a reference point is also marked
on the crankcase, Fig. 6. In the illustration, the line U.I).(1. 1
and 4 shown on the rim of the flywheel opposite the reference
mrka on the crankcase indicates that that point represents upper
dead center for the pistons of cylinders 1 and 4. The line 1-1.0.
2 and J indicates that when that line on the rim coincides with
the reference mark, the exhaust valves of cylinders 2 and X open.
Similarly, /•,'/'. / and 4 and 1.0. 1 and 4 represent, respectively,
the exhaust closing and inlet opening points of cylinders 1 and 4,
while I.C. 2 and .1 gives the inlet, closing point for cylinders 1' and :>.
The rest of the points for the various cylinders are not shown.

Lead and Lag of Valve Movement. While the strong spring
brings the valve down on its seat with a snap the moment the
valve tappet rides oil' the cam, the valve cannot be opened in
this manner. It must be lifted against the force of the spring,
and as the time available for both its lifting and its closing again

GASOLINE TRACTORS

E.Q2JM3

is so very short, it must begin to open somewhat before the
moment when it is to be fully open. This lead is given to the
inlet valves to a degree dependent upon the speed of the motor in
order that a full charge of fuel mixture may be drawn into the
cylinder on the intake stroke.

It is possible to start the opening of the inlet valve on the
suction stroke before the exhaust valve has closed because of the
fact that a gas, as well as . a solid body, has inertia. Inertia is
that property of all matter
that tends to resist a change
of state, whether that state
be rest or movement. If a
man runs full speed down
a hallway and a door at
the other end is suddenly
closed, he crashes into the
door because he cannot
overcome his own inertia
in time to stop. On the
other hand, if, when stand-
ing quietly at the roadside,
he attempts to board an
automobile passing at
twenty miles an hour simply
by grasping the part nearest
to him, the consequences
are apt to be extremely
unpleasant if his hold is
good. If it is not good,
he stays pretty much in the same place although his arm gets
a severe wrench. In the same manner a gas possesses inertia,
varying with its weight and velocity, or lack of it.

When the gas is flowing out through the exhaust valve at a
high rate of speed, since it has had almost the entire exhaust
stroke in which to accelerate, the opening of the intake valve
has no effect on its movement. Nor is there any risk of the
incoming fresh charge passing through the cylinder and out the
exhaust valve because its inertia -makes it as hard to start as

E.G.

I.O. 1 AND 4

f.C. 2 AND 3

\£. (I. ^Reference Marks for Valve Timing

24 GASOLINE TRACTORS

the high-speed exhaust is to stop and it cannot attain any speed
until the piston is well down on the suction stroke. Then it in turn
is hard to stop, so that it is possible to hold the inlet valve open
after the piston has actually passed the lower dead center and
started upward on the compression stroke. This delay is termed
the lag given the valve closing, and in the case of the inlet valve
it insures filling the cylinder with the fresh charge to the maxi-
mum extent as the fresh gas is rushing in at its highest speed just
at that moment; and every fraction of a second, or of an inch on
the stroke, that the valve can be kept open, the more efficient
the motor will be.

Need of Closely Checking Valves. \Yhile not of the high-
speed type as compared with automobile motors, which run up to
2000 r.p.m. or over, many tractor motors are high-speed types for
the service they are designed to render since the tractor runs at a
very considerable fraction of its load most of the time it is work-
ing while the automobile motor seldom carries over 20 per cent of
its full load and then only for very brief periods. Many tractor
motors are designed to deliver their rated output at 1000 r.p.m.,
and that is high speed for a motor which must carry 80 per cent
of its maximum load for eight to ten hours a day. Wear of small
parts such as valve tappets is apt to be rapid in such service, so
that to keep such a motor up to a good degree of efficiency, the
valve timing must be carefully checked and valve tappet clear-
ances adjusted to ^V inch at fairly frequent intervals. This i^
about the thickness of a visiting card. Some manufacturers sup-
ply a small metal gage for the purpose of testing this clearance,
and it should be used often since under the continued vibration
and jolting of a tractor adjustments are apt to shake loose.

Sixteen=Valve Engine. Particular attention has been called
to the important influence that the rapid filling and emptying of
the cylinders has on the efficiency of the motor, and mention has
been made of the different expedients resorted to in order to
increase this. The limit of efficiency in this respect is reached
when single valves are used for the intake and the exhaust by
placing both these valves directly in the cylinder head, so that
neither the incoming nor the escaping gases have to go round any
bends in entering or leaving the cylinder, while the combustion

GASOLINE TRACTORS 25

chamber of the latter is entirely free of pockets or dead spaces.
To increase the efficiency still further, multiple valves are used,
with the result that a larger effective area of opening is obtainable
with a given cylinder head than could be secured by increasing
the diameter of the single valves to the maximum permitted by
that of the head. In other words, four valves are placed in the
head with their centers located at the corners of a square, so that
the greatest possible amount of space available in the circle repre-
sented by the combustion chamber is utilized for valve openings.
Two of these valves are used for the intake, while the other two
are employed for the exhaust.

Twin City Multiple- Valve Engine. In Fig. 7, which illustrates
the Twin City tractor engine, the application of multiple valves
to a valve-in-head type of motor is clearly shown. These valves
have a clear diameter of 1J inches and are operated by overhead
rocker arms, each arm carrying two valves. The part sectional
view at the left shows the intake side of the motor, while the end
sectional view at the right illustrates the complete valve operating
gear of both the intake and the exhaust valves.

Another unusual feature of this engine is the use of cylinder
liners. The upper half of the crankcase and the cylinders them-
selves are cast in a single block. The liner is made with a flange
which rests on a ground seat in the cylinder, so that when the
liner is inserted, the upper face of the flange is flush with the
upper surface of the cylinder casting and the cylinder head, when
bolted on, holds it in place. This construction is clearly shown
in the right-hand cylinder in the side elevation. These liners
form the entire cylinder wall, so that the pistons do not come in
contact with the cylinder castings at any point. The dimensions
of this motor are 4J by 6 inches, and it is governed to run at
1000 r.p.m., at which speed it is rated at 20 hp.

FUEL SUPPLY SYSTEM

Operating Principle of Internal=Combustion Motor. The prin-
ciple upon which the internal-combustion motor works is that of
utilizing the great expansion of a volume of hydrocarbon vapor
ignited when in intimate contact with a sufficient volume of
oxygen to permit of extremely rapid combustion. In other words,

GASOLINE TRACTORS

an "explosion of gas," so to speak, is the driving force back of
the piston. The various phases through which the gas passes in
being drawn into the motor, compressed, fired, expanded, and
exhausted have been referred to briefly in connection with the
description of the four-cycle method of operation. Mention has
also been made of the fact that the carburetor, while not strictly
speaking a part of the motor proper, is a very important acces-
sory. The purpose of the present section is to make clear how
the fuel mixture of gas and air is obtained from the different
liquid fuels employed.

Fig. 7. Side and Knd Sectional Views of Twin C'ity Sixtorn-Valvo Motor
Courtesy of Minneapolis Sled and Machinery Company, Minneapolis, Minnesota

Fuels Available. While there are a number of liquid hydro-
carbons that may be employed as fuel in the motor, owing to
their cost but very few of them are available for tractor opera-
tion. It is scarcely necessary to discuss what may be done with
benzol, or alcohol, or any one of a number of other fuels since
their present cost is prohibitive. The choice of a fuel is limited
to petroleum and its derivatives, gasoline, kerosene, and distillate.
Owing to the great demand for gasoline for other purposes its
cost has reached a point where the difference between it and
the cost of kerosene is more than sufficient to offset the disad-
vantages of the latter. Some fanners prefer to pay the higher
price for gasoline because of the greater ease of operating the

GASOLINE TRACTORS 27

motor with this fuel, but they are greatly in the minority, and
their plowing operations are generally on a comparatively small scale.

Petroleum as it comes from the ground is a heavy viscous
liquid combining in one fluid practically the entire range of
hydrocarbons (combinations of the gas hydrogen and carbon) all
the way from that compound so light that it is evaporated by
exposure to the atmosphere before the oil ever reaches the refinery
to the heavy residue that is left after all the refining operations
have been completed and that is suitable only for making arc-light
carbons or for similar purposes. So far as their value as fuel for
the internal-combustion motor is concerned, the only difference
between any two of the hydrocarbons contained in petroleum lies
in their evaporation points, that is, the temperatures at which
the different liquids can be converted into vapor. The exceedingly
volatile fraction that passes off into the air as an invisible vapor
practically as soon as the oil is exposed to the atmosphere would
make an ideal fuel ; it would' hardly be necessary to have a carbu-
retor in its present form in order to handle such a fuel. But this
highly volatile fraction forms such a very small percentage of the
oil that running a motor on it would be equivalent to using per-
fumery essence at a dollar an ounce for the same purpose.

Products of Distillation., Up to within a few years ago the
crude oil as it came from the well was subjected to a refining
process which consisted chiefly of subjecting it to a gradually
increasing range of temperatures so that the oil was broken up
into its various constituent hydrocarbons, the latter being led off
into separate vessels where the vapor was again condensed. For
example, the first heat evaporated the naphtha, which was led off to
its own condenser; then followed gasoline, which was in turn recon-
verted into a liquid in another condenser and was itself followed
by kerosene, light lubricating oil, heavy lubricating oil, and so on
down the scale. This process of refining, however, produced but
5 to 6 per cent of gasoline from the Pennsylvania and Ohio crude
oil and so much less from the Texas and California oils that it
was hardly worth while to attempt to make gasoline in this
manner from them.

The great demand for gasoline led to the improvement of the
process by the distillation of the oil under pressure as well as at

2s GASOLINE Th \rT(>i;s

li temperature, so ll:;il in ;i<l< lil ion lo the ell'eet of the heat
in hrr.-il.ini-. llir heaVJ oil into its component, ii \v;is al>> jirtiuilly
"er;irked" I ) v llir pressure and ;i lnil<li i;reater yield ol' llir lighter
Furl oils ohl;iiiir.|. Tin- llurlon ;nul tlir I { il I m;iim ;irr llir two

processes generally employed, :unl their products are sometimes

referred lo a- "cracked oils." These methods produrr a furl lli;il
eoiiimonlv paSSefl iindri1 llir name of gasoline, hill \vliirli, owing
lo (lir mm Ii I'Tcaler proportion of heavier oil that il colll ;i ills, is II
•rade furl roinp;irrd \\illl "line ()f Irii years Jlgo.

Kerosene is the next product, MIX! llirn follow llir various grade-;

of lubricating oil.

Yt'ipori/ing Pucl. In nrdrr lluil M furl nuiy hr used in llir
motor, il must lirsl hr cnnvrrtcd inlo ;i v;ipor. Tlir rr<juirr-
iiM-nls of this pn"< drju-nd rnlii-rly upon llir rli;ir;ir( rr of tlir
liquid lo hr Imiidlcd. In <li<' <"isr of llir vrry \ol;ililr u;i-;olinr (,f
\\l:ir|i ihrrr ;ippr;irrd l<> hr .-in unlimited supply \\lirn the jiuln-
mohile first :ij»pe:ired 1 \\cnl \ -li\c \c;ir> :i:-;o, il is only n:>cess;iry
lo expos*' il lo the ;iir, so tlinl ll:c nn iiincnl jiry c;ii'hui%etors
einploycfl on Ihose first nnloinohilrs consisted in hir^e j)jirt of ;i
receptacle for ;i p»>ol of u;i>ohnr o\cr which tl:c ;iir \\;is di'jiwn lo
nirlmrrf it. This :iir picked uj> the \;ipor ri in- from I he surface-
of ihe ^iisoline pool nnd \\ilh il formed ;iu e\plosi\e mixture.
The mixing jtrocrss n;ilm-;illy could not he curried out \\ith ;my
speed. ;ind il could not he depended upon to he uniform in its
jietioii. (J.-isoliiu' evidently hepm to ,u'<> down the sc;ile very
e;irl\, since 1 he nexl ste|> \\;is to provide ;i he;i\y \\ick or similar
surface to .urcally incrca -e the area e\p,,sed to the air current
\\hich \\;is to he charged with the gasoline vnpnr. l>ut gasoline
(»f any ^radc that could he evaporated in this manner is no\\ a
tiling of the pa 1 .

N/'/v////w/ A'frj'.v.v* //•//. \\'hcn a liquid is not sufficiently volatile

to e\aporalc \\hcn the sutface of a jn.ol of it is exposed to the
;iir, the lir-l Step in caiiMnu; il to evaporate is to hreak il up into
a larue niiinlx-r of ^lohules and thus vastly increase the amount
of surl';n-e exposed to the air. To hrcak a liquid up in this man-
ner, it is spravcd hy heini;- foi'ced throuuh a small orifice known
as a jet, or iio/./le. The dilVerenl types of carhurctor jt'ls, or
no///les, ordinarilv- nnploved are illusiralcd in principle hy F;

GASOLINE TRACTORS 29

The jet A is known as a fixed jet, in that it has no means of
adjustment; B may be adjusted by means of the screw shown
and is commonly referred to as a needle valve. A valve of this
type is generally employed in the so-called mixers, which term is
merely another name for a device that serves the purpose of the
carburetor but is lacking in the refinements of construction of the
automobile carburetor. Jet C is simply a variation of B in which
the needle valve adjustment is made from above instead of below,
while in D a cone takes the place of the needle but serves the
same purpose, that is, so adjusting the orifice that the liquid will
be broken up into a spray so fine as to be practically a mist.
The fixed jet A, while used abroad to a greater extent than here,
is now becoming more generally used in this country on account
of its simplicity.

The principle of all the types is identical, namely, drawing
the liquid through a fine orifice, with or without a baffle surface
in the form of a needle or cone, so that the liquid, being under
pressure, is sprayed out of the opening as a fine mist. The suc-
tion stroke, or descent of the piston in the first part of the cycle,
supplies this pressure by decreasing the pressure in the cylinder
so that the atmospheric pressure on the liquid in the carburetor
forces it through the jet.

Mi. ring Gas and Air. As it comes out of the jet, or spray
nozzle, the fuel is in an intermediate stage between liquid and
vapor. To convert it into the latter, the descending piston also
draws up past the spray nozzle of the carburetor a supply of air.
The latter is given a whirling motion by the shape of the chamber
it enters, with the result that it picks up the tiny globules or
drops of gasoline and breaks them up further. With the volatile
gasoline of earlier days this was all that was required to produce
a true vapor, but with the lower grade fuel now common, and
particularly with kerosene and distillate, the addition of hea4:
is necessary. It is absolutely essential that the fuel mist and the
air be thoroughly mixed for the double purpose of converting the
fuel into a vapor and of bringing every particle of this vapor
into direct contact with an equivalent particle of oxygen in the
air, since it is oxygen that makes the rapid combustion of the
fuel mixture possible.

GASOLINE TRACTORS

Proportion of Air to Gas. Unless there is sufficient air, the
result is a slow-burning, or over rich, mixture that produces a
great deal of black smoke and causes the power of the engine to
fall off. It also causes the familiar back fire that is so startling
to the beginner. This occurs because the fuel is still burning in
the cylinder when the inlet valve opens to admit a new charge
and the latter is ignited and blown back through the carburetor
instead of being taken into the cylinder. If there is too much
air, the mixture is thin, or poor. In such a case the power falls
off and the engine may miss in different cylinders, often jumping
from one to another in an erratic manner. A back fire will also
occur with a lean mixture since it is likewise slow-burning.

Fig. 8. Types of Carburetor Nozzles or Jets

To produce an explosive mixture requires the mixture of
approximately ten to fourteen parts by volume of air to one of
fuel vapor, the proportions naturally varying with the character
of the fuel itself. But to produce an efficient explosive mixture
in a given engine requires a carburetor that has either been spe-
cially designed for that particular motor or one that has been
adjusted especially with a view to meeting the conditions imposed
by that motor.

The amount of air needed for any given fuel or for any motor
also varies largely with atmospheric conditions at the time and
place in question. It is solely the oxygen content of the air that
is of value in helping to burn the fuel mixture rapidly, and at
times the air is denser than at others. The denser it is, the more
oxygen it contains and the less of it is required to form a good
explosive mixture. Just after sundown in spring and fall the air
cools oil' very rapidly, and an automobile engine will run noticeably

GASOLINE TRACTORS 31

better at that time than in any other part of the day and for the
same fuel consumption the amount of air used can be decreased.
The contrary is true of high mountain districts where, owing to
the altitude, the air is thinner and contains considerably less
oxygen per cubic foot than at the sea level. In climbing from sea
level to a height of several thousand feet, it is necessary to allow a
greater proportion of air to maintain the given amount of oxygen
required for the efficient combustion of the fuel. A tractor engine
in Colorado would accordingly require a great deal more air to
operate efficiently than would one working in Illinois, the same
carburetor and the same fuel being used in both cases.

Details of Spraying Process. Since the difference between the
pressure in the interior of the cylinder when the piston is going
down on the suction stroke and that of the atmosphere (14.7
pounds per square inch at sea, level) is not very great at the
beginning of the stroke and as the time interval for charging the
cylinder is very short, the spraying of the fuel into the incoming
air must begin immediately. This is accomplished by carrying a
small supply of the liquid fuel in the float chamber of the carbu-
retor. A typical carburetor float chamber is illustrated at the left
of Fig. 9, which shows a simple form of carburetor in section.
The fuel enters from below through a needle valve, the needle of
which passes through the hollow copper float. As the liquid rises
in this chamber, the float rises with it and in so doing forces the
needle down into its seat by means of the small weighted levers
shown. The levers are attached to a collar on the spindle of the
needle.

It will be noted that this float °hamber communicates with
the spray nozzle located in the mixing chamber just to the right of
it. As a liquid always seeks its own level, the fuel rises to the
same height in the spray nozzle as it does in the float chamber
and the float is set to close the needle valve at a point where
this fuel level is normally but a small fraction of an inch below
the opening of the nozzle. The liquid is accordingly sprayed
out of the nozzle under the influence of a difference in pres-
sure of less than 1 pound to the square inch; that is, as soon
as the pressure above the nozzle due to the suction stroke of the
piston becomes less than that of the atmosphere on the supply

32 GASOLINE TRACTORS

of fuel in the float chamber, the liquid is forced out of the small
opening.

This spray, or mist, is then carried upward through the car-
buretor and through the inlet valve into the cylinder by the cur-
rent of air drawn in at the opening below the spray nozzle and
extending to the right. Owing to the peculiar form given the
chamber surrounding the spray nozzle (known as a Venturi tube),
a whirling motion is imparted to the incoming air and its velocity
is increased. The result is to mix the spray and air more thor-
oughly and to convert the mixture more nearly into a true vapor.

Effect of Increasing Speed. It is apparent that as the speed
of the motor increases, the suction on the spray nozzle will become
greater, and the interval between suction strokes, particularly in a
motor having four or more cylinders, will be so short that the
spraying action will be practically continuous. This tends to upset
the balance of the mixture by causing an excess of the fuel spray
so that the proper proportion of fuel to air is no longer main-
tained and the power output of the motor suffers correspondingly.
To overcome this, means for supplying additional air are provided,
usually in the form of an auxiliary air valve designed to be
operated by the difference in pressure between the inside and the
outside of the carburetor. In Fig. 9 an auxiliary air valve of this
kind is shown in the upper part of the illustration. It consists of
an opening in the carburetor body covered by a diaphragm, or
plate, the latter normally keeping the opening closed by means of
the spring shown. As the pressure inside the carburetor decreases
below a certain point owing to the increasing speed of the motor,
the atmospheric pressure on this diaphragm overcomes the spring
and allows an additional supply of air to enter and combine with
the mixture, which then passes off, through the opening shown at
the right, to the intake manifold.

The carburetor shown in Fig. 9 is a single fixed-jet type with a
simple auxiliary air valve, and it serves to illustrate the principles
upon which practically all carburetors work, namely, spraying the
liquid fuel in the form of a fine mist into an incoming current of
air to which greater movement and increased velocity are imparted
as it passes the spray nozzle. There are a great many different
types of carburetors and an even greater number of different

GASOLINE TRACTORS

makes, but all operate on these basic principles. In some instances
two or more nozzles are used, the smaller being in action only
while the motor is idling and the larger increasing the supply of
fuel when the increased speed of the motor brings a greater pres-

Fig. 9. Section of Typical Fixed- Jet Carburetor

sure to bear and causes them to spray. In this case the principle
K that of altering the amount of fuel in the mixture in accordance
with the speed, the air intake to the carburetor remaining fixed at
all times, while in the single-jet type described above the air sup-
ply is increased with increasing speed. Still other types increase
both the fuel and the air supply, a needle valve on the jet being

34 GASOLINE TRACTORS

connected with the auxiliary air valve, as in the Schebler carbu-
retor shown in Fig. 10. The needle valve, or spray nozzle, is at E,
and the needle is attached to a bell-crank lever, indicated by the
dotted lines, which is attached at its other end to the spindle of
the auxiliary air valve A. As the auxiliary air valve opens down-
ward under the additional suction of increased motor speed, it
lifts the needle E and permits a greater amount of fuel to spray
through the jet at the same time that an increased supply of air
enters through the valve A. While it is automatic in its action,
this carburetor is also provided with a hand control, the connecting
rod of which is attached at B: The movement of this adjustment
is limited by the boss D coming against the stop C. When in this
position, it is set for running and corresponds to the mark AIR,
indicating that the full air supply is being given; at the other end
the adjustment quadrant is marked GAS. This adjustment is
used chiefly for starting. In this particular carburetor the float,
which is not indicated in the illustration, surrounds the spray
nozzle and consists of a shellacked cork ring.

Heating Requirements. The process of converting a liquid
into a vapor is one in which considerable heat is rapidly absorbed
from the surrounding air, so that the temperature of the resulting
vapor is lowered. With the highly volatile gasoline used in early
days no artificial heat was necessary to offset this under summer
conditions, and the simple carburetors then in use were not pro-
vided with any heating devices. But when the car was run in
cold weather, it was nothing unusual for the carburetor to become
choked up with snow and ice caused by this refrigerating action of
evaporation, and this also happened when aeroplanes first reached
high levels. The lower the grade of fuel employed, the heavier it
is and the higher its temperature of evaporation, so that heat is
required even with gasoline fuel nowadays. Kerosene cannot be
vaporized unless the temperature is raised very considerably above
that of the surrounding atmosphere even on a hot summer day,
since this fuel is not at all volatile and will not evaporate at any
ordinary temperature.

Gasoline. For a carburetor handling gasoline only heat is
ordinarily supplied by water-jacketing the mixture chamber, a
small amount of hot water from the cooling system of the motor

GASOLINE TRACTORS

being circulated around this part of the carburetor. The water-
jacket space and connection of the fixed- jet type of carburetor will
be noted in Fig. 9. In addition, the main supply of air to the
carburetor is heated by clamping a sheet-iron box or "stove"
about the exhaust manifold and passing the air over this heated
surface before conducting it to the carburetor through a flexible
metal tube of large diameter.

Kerosene. While the arrangements mentioned work efficiently
on the automobile using gasoline as a fuel, they would not prove

Fig. 10. Interconnected Air and Fuel Feed
Courtesy of Wheeler and Schebler, Indianapolis, Indiana

satisfactory for burning kerosene. A very high temperature is
required to vaporize kerosene and the method of applying it is
illustrated by the section of the Wilcox-Bennett kerosene carbu-
retor, Fig. 11. The float chamber is shown at the lower left hand,
while the mixing chamber, just to the right of it, is equipped with
two needle valves. The lower of these is designed to admit water,
which is required in the majority of engines using kerosene as a
fuel. The kerosene needle valve is just above the water valve,
and it will be noted that the mixing chamber above this valve
is surrounded by a cast-iron radiator provided with fins. The

36 GASOLINE TRACTORS

function of this radiator is to absorb heat from the air pass-
ing over the exterior fins and to radiate it to the fuel mixture
inside.

The passage in which this radiator is located is connected
directly with a damper in the exhaust outlet of the motor, so that
the exhaust gases may be passed directly through it and used to
warm the air instead of merely utilizing some of the heat of the
manifold for this purpose as is done in a gasoline carburetor. In
other words, all or part of the exhaust of the motor is used for
heating by shunting it through the carburetor instead of allowing
it .to escape through the muffler in the usual way. The method of
accomplishing this in the Wilcox-Bennett carburetor is shown in
Fig. 12 which also illustrates the connection of the air cleaner to
the carburetor. The details of the radiator itself and the needle
valves are shown by the part sectional view, Fig. 13, which
illustrates these essentials of the carburetor in the no-load position
at the left and in the full-load position at the right. By compar-
ing the sectional views with the illustration of the complete car-
buretor, Fig. 14, a better idea of the relative positions of its
essential parts can be had.

At the right in Fig. 14 there is a horn-shaped device surround-
ing the exhaust passage and connecting with the mixing chamber
of the carburetor just below the needle valves. By referring to
Fig. 11 or Fig. 13 again it is seen that the object of this device
is to conduct heated air to the mixing chamber. This hot air is
required when the motor is running slowly or under light load, us
this represents a condition under which a kerosene burning motor
will not ordinarily run satisfactorily since it is apt to cool off too
much. The passage connecting this hot-air horn to the mixing
chamber is designed to be opened and closed by a weighted valve,
which is indicated in the drawing by heavy lines. It has already
been explained that the suction of the motor varies with its speed
and increases very markedly as the speed of the motor increases.
At low speeds the force of gravity is more powerful than that of
the motor suction, so that the weighted valve remains at the bot-
tom and the hot-air passage stays open; when the motor speed
increases sufficiently, the suction lifts this valve and holds it in a
position to close the hot-air passage.

GASOLINE TRACTORS

Air and Fuel Balanced. The Wilcox-Bennett kerosene carbu-
retor is designed to be automatically controlled by the speed of the
engine, the amount of fuel, air, and water admitted being depend-
ent upon the suction, which varies almost directly as the speed.

Fig. 11. Section of Wilcox-Bonnott Kerosene Carburetor, Shown at Full Speed Position
Courtesy of VSilcox-Benneit Carburetor Company, Minneapolis, Minnesota

It will be noted that the auxiliary air intake and its valve are at
the upper left hand and also that this diaphragm valve is directly
interconnected with the kerosene needle valve in the spray nozzle.
A stand pipe is employed instead of one of the conventional forms
of nozzle previously illustrated. The stand pipe consists of a tube

GASOLINE TRACTORS

whose entire circumference is drilled with a large number of fine
holes, through which the fuel is drawn instead of through a single
opening at the top. The lines to the right and the left of the
kerosene needle in Fig. 11 indicate that the fuel is issuing from
these openings. In this illustration are shown the essential parts of
the carburetor in the position they assume at full speed : the dia-
pliragm of the auxiliary air valve being depressed, so that there is a
flow of cool air into the carburetor at this point; the kerosene needle
valve is lifted well off its seat to supply the maximum amount

fae/ Conr?e cfion

Wafer Connection

Fig. 12. Method of Kmploying Exhaust Gases in Wilcox-Bcnnctt Carburetor
Courtesy of Wilcox-Bennett Carburetor ('<>r/ii>an//, Minneapolis, Minnesota

of fuel; the hot-air intake below is closed; and the water intake,
also governed by the weighted valve previously mentioned, is open.
It must be borne in mind that under the conditions given the
exhaust of the motor is at its maximum both in volume and tem-
perature, so that the kerosene mist, immediately after issuing
from the standpipe and being whirled into the radiator chamber
by the multi-bladed fan shown in Fig. 13, is at once subjected to a
decree of heat reaching at times as high as 900° F. Since this is
too hot for efficient combustion, before passing into the cylinder,
the temperature of the fuel is lowered somewhat by the addition of
the volume of air entering through the auxiliary air valve. The
admission of water and its admixture with the fuel vapor in the
form of steam serves to provide additional cooling, the necessity
for which will depend upon the action of the motor.

GASOLINE TRACTORS

Gasoline and Kerosene Carburetor. Since kerosene will not
vaporize at ordinary temperatures, it is necessary to use gasoline
for starting, the motor being run on this long enough to warm up
sufficiently to permit the use of kerosene. The combination gaso-
line and kerosene vaporizer used on the Fordson tractor is illus-
trated in Fig. 15. Being designed especially for use on this one
machine, it has been made much more compact than types which
must be adapted to a number of different motors. Compactness

Fig. 13. Detail of Radiator, Wil cox-Bennett Carburetor
Courtesy of Wilcox-Bennett Carburetor Company, Minneapolis, Minnesota

has been obtained by combining* the heating unit directly with the
exhaust manifold, a shunt valve being provided to by-pass the hot
gases as required.

The kerosene carburetor itself is shown at the lower left. It
is of the conventional single-jet type, except that instead of being
designed to produce a working fuel mixture in the carburetor
proper it is only ' intended to make a heavy kerosene mist, with
the result that only a small amount of air is drawn through it
from the primary air tube. As shown by the black arrows inside

GASOLINE TRACTORS

the small white tube, Fig. 15, this rich mixture of kerosene and air
is drawn through a heating coil in a chamber provided for that
purpose in the exhaust manifold. From that point it passes to a
mixing chamber above the inlet manifold, in which it is diluted to
the proper consistency by the addition of air through the auxiliary
air valve shown at the top of the illustration. This air valve is
controlled in the usual way, that is, it varies its position with the
speed cf the motor itself.

Just below the mixing chamber are located the gasoline con-
nection and passage, which are placed at this point since no heat

is necessary for starting on gaso-
line and since the gasoline spray
is converted into a fuel mixture
in the same mixing chamber that
is used for the kerosene. The
gasoline vaporizing device is
only in use for a minute or two
when starting, the gasoline then
being shut off. While gasoline
is being used, the exhaust shunt
lever is moved to the ON posi-
tion, which permits all the
exhaust gases to pass through
the vapor-heating tube and gives
the maxifhum heating effect.
After the motor has been running
on kerosene for a short time,
the shunt lever is adjusted to
suit the load conditions, the
temperature of the mixture being
lowered if the lever is moved toward the OFF position. When it
is desired to run any motor idle on kerosene longer than momen-
tarily, it is necessary to supply the maximum amount of heat and
the ignition should also be retarded, as otherwise the plugs arc
apt to become badly sooted. No provision is made for supplying
water directly with the fuel on the Fordson, but an air washer
is used which serves the same purpose by moistening the main air
supply.

Fig. 14. Assembled View, Wilcox-Bennett

Carburetor

Courtesy of Wilcox-Bennett Carburetor Com-
pany, Minneapolis, Minnesota

GASOLINE TRACTORS 41

Need for Cleaning Air. About fifteen years ago, when the
automobile first began to assume such a degree of reliability
where its ignition and carburetion mechanisms were concerned as
to permit some degree of attention being given to ailments of
other parts of the motor, carbon deposits were discovered on the
pistons and in the combustion chamber. Ever since then there
has been a great deal of discussion as to the conditions which
cause these deposits and the methods of preventing them. A
great deal of the discussion and most of the methods adopted
have been misguided, if not entirely futile, since an analysis of
these deposits made at an early day proved them to consist of
road dirt and grit to the extent of 65 per cent or more, the bal-
ance being simply burned and partly burned lubricating oil, which
serves as a binder and causes the mass to adhere to the cylinder
head or piston. In addition to giving rise to these troublesome
carbon deposits, which frequently accumulate to such an extent
that they cause pounding or even preignition, the fine grit which
composes a large part of the dirt drawn through the carburetor
also causes the pistons and cylinders to wear very much more
rapidly than they would were the air free of this foreign matter.
Notwithstanding these discoveries, none of the numerous remedies
proposed has ever taken the preventive form of cleaning the air
before it is used.

Tractor Air Conditions Very Bad. There are several reasons
why the troubles caused by dirt in the air have not assumed such
proportions on the automobile that it has been considered neces-
sary to use a preventive. Chief among these is the great improve-
ment that has taken place in many thousands of miles of American
roads, which have been made dustless in recent years. The general
recourse to heated air taken from a small box, or stove, placed
around a part of the exhaust manifold is another reason of equal
importance, since this prevents the direct entrance to the carbu-
retor of the air passing through the radiator. Before reaching the
opening of the hot-air box on the exhaust manifold it must pass
around various curves and strike different obstructions, which
cause most of the heavier particles of dust to fall. Since the high
speed of the machine permits it to run away from its own dust
very effectively, it is only on very windy days, when the atmos-

GASOLINE TRACTORS

phere is generally dust laden, that more than a very small amount
finds its way through the radiator.

None of these advantages obtain in the case of tractor opera-
tion. Plowing must frequently be carried out under very dusty
conditions, with the result that the entire machine operates in the
midst of a cloud of dust from which it cannot escape. Under
such conditions a large amount of dust and grit is drawn into the
carburetor as the suction is very heavy owing to the motor operat-
ing under full load most of the time. Unless this intake of dirt is

Main Air Tube
Starting Shutter
Shunt Valve Lever
Primary Air Tube

Air Valve

Air Valve Guide

Gasoline Passage'
(Shown in Shut Position)

Gasoline Pipe Connection
Vapor Tube Pack Nut

Intake Manifold
^ Exhaust Manifold

Exhaust Shunt" Valve1
Vapor Tube
Manifold Outlet

• Kerosene Pipe Connection I H* Exhaust Pipe

• Float Chamber. Drain Plu£ \

Fig. 15. Holley Combination Gasoline and Kerosene Carburetor as Used on the Fordson Tractor
Courtesy of Henry Ford and Son, Inc., Dearborn, Michigan

guarded against, wear of the moving parts of the motor becomes
excessive.

Since, as previously mentioned, approximately fourteen parts
by weight of air to each part of liquid fuel are required to make
an efficient burning mixture, the equivalent in volume of 10, (MM)
gallons of air is needed for every gallon of fuel. In the case of a
tractor burning 20 gallons of fuel in a day's work, a volume of air
equal to 200,000 gallons must pass through the carburetor and
cylinders in ten hours. The amount of dust that such a great
volume of air can hold in suspension under the conditions of

GASOLINE TRACTORS 43

tractor operation makes the importance of thoroughly cleaning the
air too apparent to call for any emphasis.

Types of Air Cleaners. Air-Washer Type. It is apparent
that two or three different principles may be taken advantage of
to remove dust and grit in suspension from a moving mass of air.
The first of these to suggest itself is that of actually washing the
air by passing it through a body of water, and a number of air
cleaners are based on this idea. The action of the air in passing
up through the water is indicated in Fig. 16, and it will be noted
that in addition to dropping its dust and other foreign matter the
air carries with it quite a percentage of moisture, so that the
washing process is a further advantage in those motors that require
considerable water to insure cool running when burning kerosene.
When using gasoline, however, washing the air is apt to be quite
the contrary since the excessive amount of water tends to cool the
mixture too much to permit efficient operation. The air washer
employed on the Fordson tractor is shown in section in Fig. 17.
'It consists of a water tank with a central intake tube and an air
guide mounted on a float and surrounding the intake tube. The
suction of the motor serves to draw air into the washer, and it is
then deflected downward into the water by the air guide. In
order that the air may pass through a considerable depth of water,
the air guide is attached to the float shown so that the air will
always enter the water at the same distance below the water level.
The float keeps this distance constant by maintaining the outlet
of the air guide at the same point at all times regardless of the
amount of water in the bowl. The air guide mentioned also
serves another purpose in that it serves to cut off the air supply
when the water supply is allowed to fall so low that the float
rests on the bottom of the bowl.

Centrifugal Type. Mention has already been made of the fact
that in compelling the current of air drawn 'through the radiator
of an automobile to pass around several obstructions most of the
heavier grit is allowed to drop before the air can reach the carbu-
retor intake. By purposely giving the current of air a whirling
movement this effect can be accentuated by taking advantage of
centrifugal force to throw the particles of dust to the outer edge
of the container, where they drop into a receptacle. This is the

GASOLINE TRACTOKS

principle upon which the air cleaner shown in Fig. 18 is based.
By referring to the phantom view of the same air cleaner, Fig. 19,
it is seen that after entering, the air is conducted through curved
channels, from which it issues to again strike a large central cone,
thus acquiring a whirling motion which tends to deposit on the
sides of the cone all matter in suspension that is heavier than air.

This matter then gravitates
down the sides of the cone and
finally drops off the edge into
the glass receptacle placed
below, which permits the oper-
ator to note the accumulation
of dust and remove it in good
season.

The same principle is
also employed in connection
with a receiving vessel, or
dust collector, containing
water. An air cleaner of this
type is shown in Fig. 20, and
a sectional view in Fig. 21.
In the latter illustration the
action of the air currents in
entering and striking the
central cone is more clearly
indicated by the arrows. The
air is first drawn into the
outer casing and the spiral
- tubes at A. These tubes are
i-.et on the inner circumference
of the casing, so that the
action of the air causes the
water to whirl rapidly and assume the position indicated by the
dotted line, exactly as any liquid will do in a bowl when stirred in
one direction very rapidly. The water, on striking against the
lower projecting edges of the spiral tubes, is broken up into a fine
spray through which the air passes in being cleaned. The washed
air then rises and enters the opening C of the inner cleaner, where

is. 16.

Sectional View of Parrett Wet-Type
Ai

Courli > / c/ 1'iirritt Trnrtnr Company,
Chicago

GASOLINE TRACTORS 45

it is again subjected to a violent whirling. This further tends to
throw down any particles of dust or water which may have been
carried along with the air, the accumulation of dust being deposited
at the bottom of the tube B. In a short time enough dirt col-
lects to form a mud seal for this tube, so that if the operator for-
gets to renew the water supply, the cleaner will continue to
operate as a dry type.

Felt Baffle Type. The third principle available in cleaning air
is that of the dust screen, and the method of employing this is
illustrated in Fig. 22, which shows the device in partial section.
It consists of a cylinder of wire gauze on which felt is stretched.
The air strikes this in entering, and the dust it contains is repelled
by the felt while the air passes through and on to the carburetor
by means of a connection with this inner chamber. The vibration
of the motor as well as the force of the current of air itself tends
to shake particles of dust off the felt and prevent their clogging it,
the dust dropping out through the holes shown. In cold weather
these holes may be closed to conserve the heat, and the dust then
collects in the outer chamber until removed by hand.

Attention Required. Regardless of the type of air cleaner
employed, the chief attention required is the frequent removal of
the accumulation of dust, or mud in case an air washer is used.
Neglect of this precaution simply makes conditions very much
worse than they would be were no air cleaner employed, since the
accumulation of dirt in the cleaner is apt to be drawn directly
into the motor. Where an air washer is employed, the deposit of
mud is converted into dust very quickly by the heat of the motor,
though the partial shutting off of the air supply causes the motor
to miss and lose power, thus providing a warning of the lack of
water.

LUBRICATING SYSTEM

Effect of Temperature and Pressure. Where the lubricating
system is concerned, as well as regards other essentials, the novice
in tractor operation will do well not to rely on his automobile
experience to carry him through without a slip that will result in
serious damage. There can be no comparison whatever between
the 30-hp. automobile motor that runs for ten hours a day and is
seldom called upon to deliver 50 per cent of its rated power and

GASOLINE TRACTORS

the tractor engine of the same rating that is delivering 80 to 85
per cent of its rated output all day long.

The sole object of lubrication is to prevent moving surfaces
from coming into actual rubbing contact of metal to metal, in
other words, to maintain a film of lubricant between the two
surfaces on which they may actually
be said to float, though the film
itself may be only a few thou-
sandths of an inch in thickness.

Fig. 18. Wilcox-Bennett Fry-Type

Air Cleaner

Courtesy of Wilcox-Bennett Carbu-
retor Company, Minneapolis,
Minnesota

Fig. 19. View Showing Method of
Separating Dust from Air by Cen-
trifugal Force

Courtesy of Wilcox-Bennett Carburetor
Company, Minneapolis, Minnesota

The problem is accordingly the same in the automobile and the
tractor engines, but the ease with which a film of lubricant may
be maintained between moving surfaces depends upon the sur-
rounding temperature and the pressure under which the surfaces
move in contact. When the temperature of the circulating water
is seldom allowed to exceed 165° F., as in an automobile motor
running under but a fraction of its maximum load, the vaporizing
point of the lubricating oil is seldom reached. But in a tractor
engine running for hours at close to its full load the circulating
water is seldom much below the boiling point at sea level, 212° F.,
and the conditions of operation are such that every part of the

GASOLINE TRACTORS

engine is very much hotter than this. Under the heavy load the
pressure between the piston and the cylinder wall is much greater,
and the oil tends to squeeze out much more rapidly, so that it
must be renewed with far greater frequency than is necessary in
an automobile engine.

Types of Lubricating Systems. Splash System. The earliest
practical type of lubricating system used on the automobile engine
was the splash system. The crankcase is filled with oil to a cer-
tain level, and the big ends of the connecting rods dip into it and
splash it all over the interior of the motor. To keep up the sup-

CLE.AN AIR
To

CARBURETER

Fig. 20. Wilcox-Bennett Wet Type
Air-Cleaner

Fig. 21. Method of Operation in Wilcox-

Bennett Wet-Type Air Cleaner

Courtesy of \Vilror-Iiennett Carburetor Compani

Minneapolis, Minnesota

ply, 1 quart or more of oil is added at the beginning of a run,
which results in having too much oil at the start and not enough
at the finish. Moreover oil is not always oil so far as its lubricat-
ing properties are concerned, since they are burned out of it by
high temperature. Therefore after a few days' steady use the oil
becomes practically useless, and only the extra quart or two added
to keep up the level serves as lubricant.

When the motor is run very cool, either with gasoline or ker-
osene, a certain proportion of the fuel mixture is condensed in the
cylinders and finds its way past the pistons into the crankcase,
thus thinning the oil out and further reducing its lubricating

GASOLINE TRACTORS

value. This is particularly true of kerosene, which has the further
disadvantage under such conditions of washing the film of oil off
the sides of the cylinder walls as it gravitates to the crankcase.
One instance is cited in which a manufacturer agreed to deliver a
tractor under its own power, but after a few hours running so
much kerosene found its way into the crankcase that the main
bearings were burned out and the tractor had to be towed back to
the shop for repairs before ever reaching its prospective owner.
In another case . that illustrates the fallacy of depending upon
automobile precedents a factory man was called to the assistance
of a farmer who reported that the
bearings of his motor had burned out
before the end of the first week's work.
When asked what he had done to lubri-
cate the motor, the farmer said that he
had added oil as often as he did on his
Ford.

Modified Splash System. The simple
splash system of lubrication is "accord-
ingly not practical on the tractor engine,
though it is successfully employed on
hundreds of thousands of automobile
motors. A small percentage of the
tractors now in use employ this system
but as a rule it is improved by the
addition of some means of constantly
feeding fresh oil to the crankcase or
of circulating it over the bearings
and depending only upon the over-
flow from the latter to furnish splash lubrication. The cross-
section of a Waukesha motor, Fig. 23, gives an excellent idea of
how the dippers on the ends of the connecting rods distribute the
oil to every part of the motor. Large receptacles over the main
bearings are kept constantly filled, while the spray of oil' thrown
up reaches even to the valve stems. The crankcase is divided
into compartments, as shown in Fig. 24, which illustration also
shows the oil pan forming the bottom of the crankcase. The oil
is raised by a small pump, forced through the wire gauze screen

Fig. 22. Orem Felt-Type Dry
Air Cleaner

GASOLINE TRACTORS

Fig. 23. Sectional End View of Waukesha Motor, Showing Operation 'uul Interior Construct i,,n
Courtesy of Waukesha Motor Company, Waukcaha, Wisconsin

GASOLINE TRACTORS

S, and distributed to the different compartments of the bleeder
tube, or pipe having openings A, B, C, and D. The overflow
returns to the pump and is again distributed, so that this is what

Fig. 24. Crank Case Oil Part, Showing Compartments and Bleeder Tube
Courtesy of Waukesha Motor Company, Wmtkesha, Wisconsin

Fig. 25. Diagram of Combination Force-Feed and Splash Lubrication
Courtesy of J* I. Case Plow Works, Racine, Wisconsin

may be termed a circulating-splash system of oiling. A gage on
the crankcase shows the level of the oil. In some systems of this
kind the stroke of the oil pump is regulated to feed the oil slowly
and it remains in the crankcase until consumed.

GASOLINE TRACTORS

Force-Feed Splash System. In the force-feed splash system
reliance is not placed entirely upon the splash of oil in the crank-
case to reach all surfaces in need of lubrication, but a supply of
oil is forced directly to the main bearings, camshaft bearings, and
timing gears, and the overflow from these points is allowed to col-
lect in the crankcase and serve for splash lubrication for the pistons,
piston pins, connecting rods, and cams. Copper tubes are usually
placed on the sides of the connecting rods to lead the oil to the piston
pins, and in some cases this oil is also relied upon to lubricate the

Fig. -<>. Molitit' Circulating Pressure Force-Feed Lubrication

cylinder walls, since it is forced out of the hollow pin on to the cyl-
inder. An indicator in sight of the operator shows whether the
oil is being supplied by the force feed. The partial section of the
( 'ase engine, Fig. 25, illustrates the details of a system of this type.
Necessity for Discarding Used Oil. One of the chief draw-
backs to all forms of splash systems of lubrication for the tractor
is the difficulty of educating the farmer up to a realization of the
saving that ihe constant renewal with fresh oil represents in
repairs. Lubricating oil is the most expensive single item of sup-

GASOLINE TRACTORS

ply for the tractor, regarded solely from the standpoint of its cost
per gallon, and the farmer dislikes to throw it away no matter
how long it has been used. Some tractor manufacturers recom-
mend that the crankcase be drained at the end of every day's
work, washed out, and refilled with fresh oil. When oil has been
used, its structure is broken down by the high temperature. It is
"cracked" — exactly as petroleum is in the pressure distillation
process by which all petroleum fuels are produced nowadays — and
it has lost its lubricating qualities. By taking a sample of oil

Fig. 27. Combination Force-Feed and Splash Lubrication. Detroit Fourteen-Lead

Chain-Driven Oiler
Courtesy of Aultman- Taylor Machinery Compant/, 'Manxfu'lil, Ohio

that has been used in the crankcase for several, days and rubbing
it between the fingers, the great difference between it and a sample
of fresh oil will be noted. The average user does not like to
drain the crankcase every day, and some practice the false econ-
omy of draining it but once a season. It will be found much
cheaper at the end of a season's work to have bought plenty of
good lubricating oil and used it but once, than to attempt to
economize by using it over and over again. Repairs always cost
far more than oil. The used oil may be employed to lubricate other
parts of some machines, such as the track of a caterpillar tractor.

GASOLINE TRACTORS

Pressure-Circulated Lubrication. Following automobile prac-
tice, some motors have the crankshaft drilled throughout its
length and tubes connecting with this bore rising from the con-
necting rod bearings, so that the pressure generated by the pump
causes the oil to flow over these bearings constantly, the cylinder
walls being lubricated by the overflow through the piston pins.

Fig. 28. Force-Feed Oiler of Two-Cylinder < Hl-PuM Kn"ino
Courtesy of Advance- Rumcly Thretker Compmy, Inc., /.<;/>»/•/»•,

In this system no dependence is placed on splash lubrication, jt:-.d
the connecting-rod big ends are not allowed to dip into the over-
flow, as shown by the section of the Moline motor, Fig. 26.

This system is also known as the dry-crankcase type in that
the excess oil drops into a sump, or well, below the crankcase in
which the pump is located, with the result that the entire supply

GASOLINE TRACTORS 55

is constantly kept in circulation. More than one pump is some-
times employed for this purpose, so that oil is drawn from differ-
ent parts of the crankcase at the same time. The advantage of
this method is that the location of the machine, as in climbing a
hill, has no effect on the quantity of lubricating oil that reaches
every part of the motor.

Fresh-Oil System. A very considerable percentage of all the
tractors now in use follow steam-engine practice in lubrication by
feeding only as much oil as is required by each bearing, so that

Fig. 29. Eccentric-Driven Force-Feed Oiler

Courtesy cf II art- Parr Company, Charles City, Iowa

the oil is consumed almost as fast as it is fed. This has the
advantage of constantly renewing the lubricating film with fresh
oil. To provide a factor of safety, however, the supply must
actually be fed faster than it is used by the bearings in order that
oil may accumulate in the crankcase, and unless this is drained off
at frequent intervals, this system is open to the same objection as
the ordinary splash system.

The supply of fresh oil for a system of this type is carried in
an external reservoir which also serves as the lubricator, in that it
is fitted with a number of small plunger pumps, one for each lead,

56 GASOLINE TRACTORS

or tube leading to the bearings. The lubricator is driven by a
belt, chain, or rod (preferably the last named) from the camshaft
of the motor, as shown in Fig. 27, which illustrates the Aultman-
Tavlor engine equipped with a fourteen-lead Detroit lubricator.
Fig. 28 shows a similar lubricator on the Rumely two-cylinder
motor, and Fig. 29 a Madison-Kipp lubricator on the Hart-Parr
engine, -an eccentric or crank an4 rod being employed to drive the
lubricator pumps in both instances.

Frequent Attention Necessary. On an automobile, it is noth-
ing unusual for grease cups to go an entire season without being
refilled, and during that time they have only been turned down
once or twice. How radically different is the attention required
by a tractor may be appreciated from the instructions for oiling
an International tractor. When doing belt work, the grease cup
on the pulley must be turned down every hour. There are eleven
bearings on the fuel and water pumps, camshaft, front wheels,
rear axle, and clutch that require turning down every two hours
that the tractor is running. On another group of ten bearings the
grease cups must be turned down twice a day, while three others
must be turned down once a day.

COOLING SYSTEM

Heat Efficiency of Motors. While the thermal, or heat,
efficiency of the tractor motor is high as compared with that of a
steam engine, in which it is difficult to utilize more than 8 per
cent of the available heat of the coal, it is an unfortunate fact
that a very large part of the heat available in gasoline or kerosene
must also be wasted since no method that will utilize more of it
has yet been discovered. Considering the fuel value of the enter-
ing charge as 100, about 40 per cent of this escapes through the
exhaust valve at the end of the power stroke and during the suc-
ceeding exhaust stroke. An additional 35 per cent that cannot be
utilized to drive the piston by its expansion must be absorbed and
quickly dissipated or it will soon overheat the motor and bind the
pistons hard and fast in the cylinders. Thus only 25 per cent of
the ival value of the fuel is converted into power. These are
simply average percentages which may be made poorer or better
by the type of engine, some simple steam engines working in the

GASOLINE TRACTORS

open in cold weather and poorly protected not showing an effi-
ciency to exceed 3 or 4 per cent, while a condensing Corliss type

unit would reach 17 per cent and a modern type Diesel oil engine
35 per cent or better.

Types of Cooling Circulation. To carry the great amount of
excess heat away from the cylinder heads and exhaust valve ports

58 GASOLINE TRACTORS

with sufficient rapidity to prevent these parts becoming over-
heated, a body of cool water is kept in direct contact with them
and is replaced by fresh water as quickly as it can absorb the heat.
This water is contained in the jackets — spaces cast in the cylinder
walls and cylinder head for this purpose. The cool water is con-
ducted to the lowest part of this water-jacket, passed up over the
hottest parts of the cylinder, and then led to the radiator consisting
of a bank or nest of tubes. These tubes are made of copper,
which is an excellent conductor of heat as well as of electricity,
and their cooling surface is greatly increased by surrounding them
with thin copper fins which give up their heat to the air very
readily. The movement of the water between the jackets and the
radiator is termed the cooling circulation.

Thermo-Syphon Circulation. The circulation of the water may
be effected by the difference in the temperature of the water itself
or may be brought about by forcing the water through the piping
at high speed by a pump. The first method is known as thermo-
syphon circulation and its operation is illustrated by the view of
the cooling system of the Fordson tractor, Fig. 30. The radiator
is shown in section, while the flow of water through the connecting
pipes and the cylinder jackets and head is indicated by the arrows.
After passing downward through the radiator, the water issuing
at the bottom is considerably cooler than that at the top of the
cylinder jackets, which has been absorbing its charge of heat. As
water gets hotter, it expands and becomes lighter, so that it tends
to rise. The water in the cylinder head jacket accordingly flows
toward the radiator and is replaced by fresh water rising through
the cylinder jackets. The hotter the water gets, the faster it
(lows, its movement being controlled entirely by the difference in
temperature between the water entering and the water leaving the
system at the coolest and hottest points. It will be noted in the
illustration how sliort and direct the connections are and how
large their diameter is as compared with the connections on a
motor on which a pump is employed to provide forced circulation
of the cooling water, Fig. 31.

Forced Circulation. On the majority of tractors a forced type
of circulation is employed. In this type the water is moved around
through the cylinder jackets and to the radiator and back by

GASOLINE TRACTORS 59

means of a centrifugal pump driven from the camshaft or one of
the other auxiliary shafts of the motor. The body of water car-
ried, the size of the cylinder jackets, and the diameter of the con-
necting pipes may all be made much smaller than in systems
where the water must move under the force of its own difference
in temperature, as in the therm o-syphon system. But it is also
apparent that the factor of safety is also somewhat lower in the
forced circulation type than in the other. Any failure of the pump,
fan, connections, or radiator must be detected and the engine

Fig. 31. Pump and Connections of Forced-Circulation Cooling System Used

on Heider Tractor Engine
Courtesy of Rock Island Plow Company, Rock Island, Illinois

stopped at once if serious damage is to be avoided. With an
engine that is designed to be run constantly under such a high
percentage of its maximum load for a number of hours as the
tractor engine, the cooling and lubricating systems are of the
greatest importance. This is true particularly of the cooling sys-
tem since any failure in it involves the lubrication system as well,
as the moment the temperature rises beyond control, the lubricating
oil is burned to carbon and the damage is done.

Protection of Radiator from Stresses. The tubular type of
radiator is the most practical for tractor use owing to the neces-

GO GASOLIXK TRACTORS

sity for withstanding constant vibration and also jolting and rack-
ing, and 'it is good practice to support the radiator on a flexible
mounting so that these stresses cannot affect it directly. This
refers particularly to the straining and racking due to the pas-
sage of the tractor over very uneven surfaces. To prevent damage
from this cause, some radiators are mounted on a pin and trun-
nion, others have a three-point support, while still others are
located at points on the frame where they will be subjected to the
least stress from the twisting and bending due to rough going.
In the illustrations in the section on motors the pumps and con-
nections used on some of the machines are noticeable so that it is
unnecessary to illustrate them here.

Automobile Experience Misleading. When first undertaking
the management of a tractor, the average operator is very apt to
be guided by his automobile experience and treat the heavier and
slower-traveling machine in the same manner. This is apt to lead
to serious errors as far as both the cooling and the lubrication are
concerned. The tendency of most automobile engines is to run
too cool to be efficient. In other words, if they could be run
steadily at a higher temperature, less gasoline would be used and
the smaller quantity passing through the cylinders would be
employed more efficiently. But an automobile engine never runs
steadily for any length of time and it is very seldom that more
than a fraction of its normal power output is used at all. Except
in pulling out of a mud hole or in climbing a very steep hill, it is
rare for more than 25 per cent of the output of the motor to be
needed in driving the car. Consequently its cooling system is very
seldom called upon to work to capacity.

There are few cars built that could climb a two- or three-
mile hill mainly on second or even third speed without starting
the water to boiling very violently, and if the hill were five miles
long, few would be able to get up without a stop on the way to
cool off the motor. Compared with the level road service that an
automobile is usually called upon to perform, the tractor, par-
ticularly when plowing, is performing the equivalent of mounting
a steep hill on second or third, with the exception, however, that
there is no summit to the hill and no opportunity to cool until the
motor is shut down For the day. The cooling system accordingly

GASOLINE TRACTORS 61

calls for close attention, any sign of overheating being noted
immediately and the engine shut down at once to remedy the
trouble. Fan belts and pumps must constantly be kept at a high
state of efficiency since slippage at the fan or a leaky pump gland
will reduce the cooling ability of the system all out of proportion
to the apparent importance of the defect. When working under a
heavy load, such as plowing or driving a good-sized thresher, the
engine cannot be shut down too quickly upon the first indication
of any trouble writh the cooling system as under such conditions
only a few minutes are required to destroy the film of lubricating
oil between the pistons and cylinders and then the damage is done.
With an automobile engine it is seldom necessary to add
water to the cooling system even after a long run on a hot sum-
mer's day. A tractor cooling system, on the other hand, may
need water several tunes a day, and this is particularly true of the
thermo-syphon type of circulation since the water wrill not con-
tinue to circulate unless the entire system is filled to a certain
level. The slower speed at which the water circulates in this type
keeps it at a higher average temperature, so that evaporation is
rapid. The manufacturers of the Fordson, for instance, recom-
mend that the radiator always be filled before starting and replen-
ished every time the machine is stopped for fuel or oil. As regards
winter use, the same precautions apply as in the case, c.f the auto-
mobile, that is, the radiator must either be drained upon stopping
the motor or an anti-freezing solution used. Since the latter
reduces the boiling point considerably, evaporation is even more
rapid when running under full load on anything but very cold
days, so that it is better practice to drain the system.

IGNITION SYSTEM.

Importance of Ignition. It has been previously stated that
precedence cannot be given to any of the systems upon which the
operation of the motor depends since the failure of any -one means
the stopping of the motor. It will be found in practical service,
however, that there are various degrees of importance as far as the
order in which the failure of these systems may be responsible for
stopping the motor is concerned. Considered from this point of
view, the ignition system heads the list in that it is apt to be the

62 GASOLINE TRACTORS

cause of failure to operate more frequently than any of the others.
There is no function of the motor, a knowledge of which is more
important to the operator than familiarity with the principles
involved in ignition, since without this knowledge it is always
much more difficult to locate and remedy the trouble. Ignition
breakdowns do not result in the serious damage that attends a
failure of the cooling or the lubricating system, but they involve
vexatious delays and the loss of much valuable time when the
difficulty cannot be located quickly. The following brief review
of electrical principles is confined wholly to those utilized in tractor
operation, and they should be thoroughly mastered.

Electrical Principles

Electric Current. Electricity is one of nature's forces possess-
ing many of the characteristics of light and heat plus a number
that are peculiar to it alone. Like light and heat, it may be pro-
duced by artificial means in a number of different ways. The
energy it represents may be utilized in different forms, such as
current or as magnetism. For ignition purposes the electric cur-
rent is either produced by a direct-current generator and chemically
converted into another form in a storage battery from which it is
taken for producing the spark required, or it is generated by a
magneto, which is a simple form of alternating-current generator.
Electric current may thus be direct or alternating, and in either
case it possesses the property of being able to flow along or in a
conductor. In the former case it flows in one direction around
what is termed a circuit, the point at which it issues from the
generator or battery being known as the positive, or +, pole, and
the one to which it returns being the negative, or — , pole. The
signs + and - - are usually stamped on storage batteries to indi-
cate what is known as the polarity of the battery, and they cor-
respond to the north and the south poles of a magnet. ^Alternatiag
current, on the other hand, pulsates, or alternates, first in one
direction and then in the opposite, so that a pole which is positive
at the beginning of an alternation becomes negative at its comple-
tion since the current then rises and flows i.i the opposite direction.
A direct current is of uniform strength in addition to flowing in
one direction, while an alternating current rises from zero to its

GASOLINE TRACTORS 63

maximum and then drops back to zero to rise again in the opposite
direction. The majority of tractors are equipped with magnetos,
which generate an alternating current, and from the character of
such a current, as just outlined, the importance of properly tim-
ing the magneto to the engine may be appreciated since the cur-
rent for producing the spark is only present when an alternation
is approaching its maximum, or peak. If the magneto is improp-
erly timed to the engine, no spark will occur at the plug.

Electrical Units. Electricity may be measured in units
equivalent to the pressure and the rate of flow of any other form
of energy and, carrying out the comparison, it also encounters
resistance to its flow. The ampere is the electrical unit of quan-
tity; the volt, that of force, or pressure; and the ohm, that of
resistance. The electrical power unit is the wratt, equal to the
product of 1 ampere times 1 volt. The flow of an electric current
may be compared directly to that of water under pressure in a
pipe. The number of gallons delivered per minute is the equiva-
lent of the amperes of current; the pressure under which it is
delivered corresponds to the voltage of the current; and the
resistance to flow represented by the friction of the water against
the walls of the pipe corresponds to the resistance encountered by
the current in a wire or other conductor. By increasing the pres-
sure on the water, a greater volume is delivered in a given time.
By increasing the voltage of an electric current, although no
greater volume of current is delivered, the resulting power is cor-
respondingly greater since electrical energy is represented by the
product of the number of amperes times the voltage. Moreover
when the pressure on the water is increased, a smaller proportion
of the total head, or pressure, is lost in friction, and this is equally
true of an electric current since the higher the voltage, the smaller
the amount of electrical energy dissipated in the wire as resistance.

Conductors. The flow of an electric current is determined by
the nature of the material comprising what is known as the cir-
cuit. Some materials are very good conductors, such as silver,
copper, brass, and aluminum; others are poor conductors, such as
iron, nickel, and alloys containing a high percentage of these metals;
while still other materials, such as glass, porcelain, mica, rubber,
wood, and stone, will not conduct the current at all when dry.

GASOLINE TRACTORS

The latter are insulators and are used to prevent the passage of
the current where this is not desired; for example, part of the
spark plug is made of porcelain. The ability of a material to
conduct electric current is determined by its size as well as by its
nature. Given two pieces of wire of the same size, one of copper
and the other of iron, the copper wire will conduct the current
approximately thirty times easier than the iron. By increasing
the iron wire to thirty times the size of the copper wire, both will
then conduct the same current and voltage with the same amount
of resistance. Iron and nickel are accordingly high resistance
conductors, preventing the free flow of the current and converting
a large part of the energy represented by the latter into heat,

Fig. 32. Simple Series Circuit Representing Ignition System -of Single-Cylinder Motor.
The Parallel Lines are Ground Return through the Motor

which explains why a piece of iron wire will not serve as well for a
magneto or battery connection as the copper wire supplied by the
manufacturer. In addition to the insulators already mentioned, no
fabric such as silk, cotton, and wool will pass current when dry,
while dry air is the best insulator known.

Circuits. It has already been mentioned that a current flows
from the positive to the negative pole of the source of energy, but
in order for it to do so there must be a complete circuit of con-
ducting material between the two, a current of low voltage being
considered in this connection. The presence of any insulators in
the path of the current accordingly prevents its flow, and since air
is one of the best insulators, any break in the current such as a
parted wire or a loose connection admits air and interrupts the

GASOLINE TRACTORS

flow of current. If the material comprising the conducting path,
or circuit, be of high resistance, the flow of current will be either
greatly reduced or prevented altogether in the case of the low-
tension currents employed in ignition. If a conductor of high
resistance, such as a very small piece of wire, occurs in the circuit
of a storage battery, it is likely to melt owing to the heat generated
by its resistance.

Ignition Circuits. Ignition circuits are of but one kind, that
is, series circuits in which all the pieces of apparatus, such as the
magneto, the coil, and the plugs, form successive steps through
which all the current must pass in order to complete the circuit.
Simple forms of series circuits are illustrated in Figs. 32 and 33,
which show a dry battery, coil, and plug used as a starting system

\\\

Fig. 33. Series Circuit Using Low-Tension Magneto for
Single-Cylinder Ignition System

for a tractor and a low-tension magneto, coil, and plug constitut-
ing a complete ignition system. When a battery is employed for
lighting to carry on night work as well as for ignition, two inde-
pendent series circuits may be fed from the same source, the
amount of current taken by each being determined by the resist-
ance that it presents to the flow of the current. A multiple, or
parallel, circuit is one in which lamps, motors, or other apparatus
may be inserted at any point, each unit being connected to oppo-
site sides of the circuit, so that any unit may draw current inde-
pendently of the others. Connections may be taken at any point
on opposite sides of such a circuit to form a branch circuit and
the apparatus in the branch circuit connected in series, resulting
in what is termed a multiple-series circuit.

66 GASOLINE TRACTORS

Voltage and Amperage. The pressure under which the cur-
rent flows is termed its voltage, and this may be determined
either by the source of supply or by the presence of a transformer
in the circuit. In the case of a battery the voltage depends upon
the number of cells connected in series with one another, while the
amperage, or volume of current, is measured by that of any one
cell in the series. For example, dry cells deliver a current at 1J
volts and ordinarily average 15 amperes for short periods. A
battery of four dry cells in series would thus produce a current of
15 amperes at 6 volts. If the cells were connected in multiple, that
is, all the positives together and all the negatives together, the
current would be increased but the voltage would be that of a
single cell, so that there would be a current of 60 amperes at li
volts.

Storage Battery. In the case of a storage battery which
delivers current at 2 volts per cell, the voltage required for igni-
tion, that is, 6 volts, is obtained by connecting three cells in
series, while the volume of current depends upon the capacity of
the individual cells in the series, and this in turn is measured by
their size. For ignition service cells of a battery are always con-
nected in series, so that the positive of one cell must be connected
to the negative of the next, and so on throughout the series, one
terminal of the battery being positive and the other negative.
Any cross connection in the series, such as the connection of the
positive of one cell to the positive of the next, would cause one
part of the battery to act against the remainder, with the result
that no current would be delivered to the outside circuit.

Magneto. The voltage of the magneto or any other mechani-
cal current-generating device is determined by the speed of its
armature. The magneto illustrates the fact that electricity and
magnetism are different forms of the same force in that one may
be readily converted into the other. By moving a magnet close to
a coil of wire, a current of electricity is induced in the wire, while
if a coil of wire is placed about a bar of iron or steel and an
eleetric current is then passed through the wire, the bar becomes
magnetic. Steel retains a considerable percentage of the magne-
tism after the current ceases and is termed a permanent inaunet.
The fields of a magneto are formed of permanent magnets and

GASOLINE TRACTORS 67

supply the magnetism by means of which a current is generated
when the wire on the armature is moved past their pole pieces,
that is, their north and south poles. Therefore a magneto will
generate a current at any speed, but the amount of current and
the voltage under which it flows depend upon the speed with
which the armature is revolved. The strength of a magnet is
represented by imaginary lines passing from one pole to the other,
and these are termed lines of force. The voltage of the magneto
current is determined by the number of times per minute that the
wires of the armature cut through the lines of force between the
magnet poles.

Low= and High=Tension Currents. The foregoing brief expla-
nation has been confined to what are known as low-voltage cur-
rents, the storage battery delivering current at 6 volts for ignition,
while the magneto when running at full speed generates current at
approximately 100 to 125 volts. Any current under 500 volts is
usually referred to as a low- volt age current. In connection with
the explanation of insulators it has been mentioned that the
interposition of any insulating material in the circuit, and partic-
ularly a break or loose connection which creates an air gap,
interrupts the flow of current. This is true of all low-voltage
currents; all parts of the circuit must be not merely connected but
in firm and positive contact, and the contact surfaces must be
clean and bright since dirt is likewise an insulator. This is a
principle frequently overlooked in the care of tractor and farm
engines, which usually work in very dusty places; it is absolutely
necessary to keep all connections • clean and tight to insure the
satisfactory working of the ignition system.

Since even a loose connection will interrupt the flow of current
in a low-voltage circuit, it is not suitable for the production of a
spark unless the terminals representing the positive and negative
sides of the circuit are actually brought into contact and then
separated. What is known as the low-tension system of ignition
is emoloyed on thousands of stationary farm engines and also on
many tractors having low-speed engines. Most stationary engines
are run at low speeds, ranging from 200 or less to 450 r.p.m.,
while few tractor engines run below 600 r.p.m. at normal speed
and most of them operate at much higher speeds.

GASOLINE TRACTORS

Types of Ignition Systems,

Low=Tension Ignition. While dry cells may be employed for
ignition with a stationary engine equipped with a hit-and-miss

governor that cuts off the cur-
rent except on the power strokes,
they do not give satisfactory
service and therefore a magneto
is generally used. The magneto
chosen is the simplest type and
consists of nothing more than
the field pieces, or permanent
magnets, and a simple armature
having a single winding. It
may either be rotated or given
a quick partial revolution by
a rod and spring, but in any
case it must be timed to the
engine, so that the current in
its armature is at the maximum
value when the spark is to occur
in the cylinder. While such a
magneto produces ample cur-
rent at a fair voltage it is not
sufficient to produce a spark of
the desired size for low-tension
ignition, and therefore a spark
coil is placed in the circuit.

Spark Coil. The spark coil
consists of a single winding of
many layers of heavy insulated
wire on a thick short core built
up of fine iron wire that has
been annealed until it is very
soft, as in this condition it is
capable of being magnetized and

very quickly. Such ti coil acts on the principle of self-
induction and produces a much hotter and larger spark than the
magneto could unaided. Its working will be clear from Fig. 34,

GASOLINE TRACTORS 69

which shows a typical low-tension ignition system. Up to the
time it is necessary for the spark to occur in the cylinder, the
ignitor has its points in contact, so that the circuit is closed and
current flows through the ignitor and the winding of the spark
coil. Consequently the core of the coil is magnetized and stores
up the equivalent of the current which magnetized it. When the
circuit is broken by the sudden snapping of the ignitor, this mag-
netism is instantly reconverted into electric current and adds its
force to that of the current in the winding, and a much hotter
spark results at the contacts. In fact, this is really a flash instead
of a spark and is usually termed an arc; and it is so hot that it
burns the contact points away rapidly, which is one of the dis-
advantages of the low-tension system.

High=Tension Ignition. In high-tension ignition the ignitor of
the low-tension system is replaced by a spark plug with fixed
electrodes, or terminals, separated by an air gap. But in order
that the current may bridge this gap, it is necessary to raise it
to a high voltage. This ranges all the way from 10,000 to 30,000
volts, the higher voltage being necessary when the initial com-
pression of the engine is high since a greater electrical tension is
required to create a spark across a gap in compressed air than
out in the open.

Induction Coil. In the brief reference given to elementary elec-
trical principles it has been mentioned that when a coil of wire is
passed before a magnet, a current of electricity is induced in the
wire. This also occurs either wdien one coil of wire in circuit
through which a current is flowing is moved close to another in
which there is no current or, the two coils being stationary,
when the current is suddenly broken in the first. This is the
basic principle of the transformer, or induction coil. As% in the
case of the spark coil, the effect produced is greatly increased by
using a heavy core of soft-iron wire. The character of the current
induced in the second coil depends upon the relation that the
windings of the latter bear to those of the coil in which the
current, termed the primary current, is flowing. If both coils
have the same number of turns in their windings, the induced, or
secondary, current will be approximately the same in amperes and
volts as the primary current. By increasing the number of turns

70 GASOLINE TRACTORS

in the secondary winding of the coil, the voltage of the induced
current will be increased correspondingly. An induction coil
accordingly consists of a comparatively few turns of heavy wire
for the primary winding, which is closer to, though insulated
from, the soft-iron core. The secondary coll consists of a great
number of turns of very fine wire and surrounds the primary
winding, but it must also be well insulated from the latter, as
otherwise the high tension-current would tend to jump from the
windings of one to the other. A coil in which this has occurred
is said to be punctured and, as it is short-circuited, is useless for
ignition until repaired.

Mechanisms to Make and Break Circuit. Where batteries
are employed for ignition or the magneto generates a current
which, though alternating in its nature, is of such high frequency
as to be practically continuous, as on the Fordson tractor, the
induction coil must be equipped with a vibrator to make and
break the circuit since current is only induced in the secondary
winding when the circuit is broken or the current rises and falls
from zero to maximum and the reverse, as in an alternating
current of lower frequency. In what is known as the modern
battery system, employing a storage battery kept charged by a
small direct-current generator, a primary contact breaker in con-
nection with the distributor takes the place of the coil vibrator
and but one coil is used.

Essential Parts of System. A high-tension system accordingly
consists of a source of current, most often a magneto, a coil, a
spark plug for each cylinder, and a distributor. The distributor
always forms a part of the magneto and is driven by the magneto
shaft, and in what is known as the true high-tension type of
magneto the coil is also incorporated with it; that is, the magneto
generates the primary low-tension current and also transforms it
or steps it up to the required high voltage, the armature usually
carrying both the primary and the secondary windings. Conse-
quently with a high-tension magneto the complete ignition system
consists of the magneto itself, the spark plugs, and the necessary con-
necting cables, so that the entire system is practically self-contained.

Condenser. A part of the high-tension system with which the
operator is not likeh to become acquainted unless something goes

GASOLINE TRACTORS 71

wrong with it is the condenser. In the form employed for igni-
tion the condenser consists of alternate leaves of tinfoil and par-
affined paper, the latter serving to insulate the sheets of tinfoil
from one another. The tinfoil sheets are divided into two groups,
which are connected to opposite sides of the contact breaker of
the magneto, so that the condenser is in multiple with the breaker.
(Magneto parts and construction are explained in detail in con-
nection with the description of some of the standard makes
employed for tractor ignition.) When parts in contact carrying
current are suddenly separated, a flash, or arc, occurs owing to
the tendency of the current to continue its flow across the break,
as happens in a low-tension ignitor. This not only represents* a
loss of energy but tends to burn away the parts. To prevent
this, a condenser is shunted about the contact, that is, connected
in multiple with it. The current, instead of continuing across the
gap in the form of an arc as the contacts open, flows into the
condenser, which has the capacity to store a charge of electricity.
Immediately upon the contact being made again so as to reclose
the circuit, this stored charge flows back from the condenser into
the circuit.

Safety Spark Gap. In the explanation of circuits mention
has been made of the fact that a current divides or flows through
different branches of a circuit in proportion to the resistance in
those branches. In other words, it will always seek the path of
least resistance. Consequently, if the air gap of a spark plug be
made so large that it represents a resistance greater than the
insulation of the windings of the coil, whether this coil be sepa-
rate or on the armature of the magneto, the current will break
down the insulation and short circuit the winding. The current
burns away the electrodes of the spark plugs and the gap must be
adjusted from time to time to correct this; at the most the gap
should not exceed the thickness of a visiting card, or -^ inch.
As the gap widens, the spark becomes thinner and loses its heat
value so that the ignition is less and less satisfactory. When at
last the gap becomes so wide as to present a greater resistance
than the coil insulation, the spark will jump across the safety
spark gap provided to protect the coils. This gap is designed
with an opening having a resistance that is considerably less than

GASOLINE TRACTORS

that of the coil insulation so as to allow an ample margin of
safety for the coils. It is usually located under the arch of the
magnets of a high-tension magneto and is mounted on the dis-
tributor of a modern battery ignition system. The occurrence of
a spark across this gap is an indication that one or more of the
spark plugs have been burned open too far, though this will
usually be evident from the poor ignition resulting.

Low=Tension Magneto. Magneto ignition has proved the
most dependable as well as the most enduring for tractor work
since the excessive vibration and jolting make the use of the
storage battery practically out of the question. Dry cells are of
little value in any case for ignition, except where starting is con-
cerned, and the necessity for them has been eliminated by the
development of the impulse starter on the magneto, as described

Fig. 35. Inside and Outside Views of Low-Tension Ignition Plug
Used on Oil-Pull Tractor

later. There are several types of magnetos in general use on
the tractor and a brief reference is made to each of them.

On tractors employing low-speed horizontal engines, low-
tension ignition is .standard equipment. It has the advantage of
being extremely simple and all its parts can be made amply strong
enough to withstand the strenuous treatment of tractor service in
the field. Its chief disadvantage is the more or less frequent
necessity for attention to the ignitors, though the hot flash pro-
duced by the latter is better adapted to ignite low-grade fuels
than the high-tension spark produced by a plug. The magneto
employed with the low-tension system has but one winding and
no contact breaker nor distributor. It is connected in a simple
series circuit with a spark coil and the ignitors. The Bosch low-
tension magneto is the type employed on the Ruinely tractor.

GASOLINE TRACTORS

In Fig. 35 are given two views of an ignitor, the view at
the left showing the tripping mechanism outside the cylinder,
while that at the right shows the details of the fixed and movable

IGN/TJON SPOOL SfOP-J /flDJVSTING SCREW -5
/GMT/ON SPOOL;?

ELECTRODE F/NGER-

-/GM/T/ON PLUG -4

Fig. 36. Tripping Mechanism of Low-Tension Igniter, Electrodes in Contact before Sparking

electrodes between which the spark occurs when they are suddenly
snapped apart. In Figs. 36 and 37 are shown the details of the
tripping device, the former illustrating the mechanism with the
electrodes in contact just before sparking.

Timing of Low-Tension System. Since the magneto is directly
connected in a simple series circuit with each ignitor, it is evident
that both the latter and the magneto itself must be timed to
produce the spark at the proper moment for the explosion. The

/GN/TIOM SPOOL STOP~
/GN/TtON SPOOL -2

ADJUSTING SCREW-5

'GN/T/ON TR/PPEft-6

-/GMT/ON PLUG -4

Fig. 37. Low-Tension Ignitor Tripping Mechanism, Showing Adjustment Spacing

ignitor is tripped by a push rod and cam on. the camshaft in
exactly the same manner as the valves are operated, while the
magneto itself is timed to the motor in much the same manner

GASOLINK TRACTORS

as is necessary in the case of a high-tension magneto. In the
section on elementary electricity it has been explained how an
alternating current rises from zero to maximum in one direction

and then subsides and rises
again in the opposite direc-
tion. This is termed a sine-
wave current and is illus-
trated by Fig. 38. The only
part of this current that is
of value for ignition is repre-

Fig. 08. Sine Wave Alternating Cur-
rent as Generated by Magneto

sented by the few degrees in
the revolution of the arma-
ture that are indicated by
the peaks of the alternations. In a simple magneto with an H
armature, Fig. 39, this peak occurs at the point shown in the
illustration, that is, the point when the core of the armature is
entering the tunnel formed by the pole pieces attached to the field
magnets at their lower ends.

In Fig. 39 the armature is turning to the left and has just
left the right-hand pole piece by YG inch. From this point until

the center of the core of the
armature is on a line with the
upper part of the pole piece, the
value of the current is close to
the peak and is rising. The
further revolution of the armature
causes it to fall, and when the
core reaches the lower part of the
tunnel, it reverses and starts
upward in the opposite direction.
The armature of the magneto
must accordingly be set so that it
is in the position shown in the

Fkg.30 Motion if Armature illustl'at i()ll when tllC igllitor is

about to trip. This is not the maximum, as the armature cuts
the greatest number of magnetic lines of force a few degrees
further around and thus produces the current- of the greatest
value at that point. This setting allows for the necessary advance

ARMATURE-L

GASOLINE TRACTORS 75

of the sparking time, which causes the latter to coincide with the
point of maximum value just mentioned.

Causes of Trouble Few. There being only a current of very
low voltage in any part of the system and only a single short
wire being necessary to conduct this low-tension current to the
ignitors, electrical troubles are rare with the low-tension system
and are confined chiefly to failure of the ignitors, or make-and-
break plugs, to spark owing to an accumulation of carbon, or
soot, on the electrodes. Apart from this, any shortcomings of the
system are apt to be purely mechanical rather than electrical.
The tripping mechanism and springs must necessarily be light,
but at the speeds at which they operate wear is more or less
rapid, so that considerable attention is required to maintain them
in efficient operating condition. This is the chief reason why the
low-tension ignition is not applicable to the high-speed type of motor.

As before stated, most of the electrical difficulties experienced
with the low-tension system involve the ignitors, or make-and-
break plugs. Unless the fuel is being burned very efficiently by
the engine, they short-circuit very quickly through a deposit of
carbon, although this also occurs at regular intervals even where
it is not possible- to improve upon the running of the engine.
Another cause of trouble is the sticking together of the electrodes
by what is practically a form of electric welding. Carbon deposits
must be scraped off carefully, electrode contact surfaces filed or
scraped bright, and the remainder of the plug cleaned with kero-
sene. After a considerable time in service the mica insulation of
these plugs may become so impregnated with carbon dust or a
mixture of oil and carbon dust that it is impossible to prevent it
short-circuiting, in which case it is necessary to replace the mica
insulation. The plugs are the source of the trouble in about 85
per cent of the cases, but when they are in good condition, the
magneto should be tested, first, to note whether it is generating
or not and, second, to see whether it is properly timed to the
engine. To provide sufficient current at a good voltage, the
plug must snap, or break, just at the moment when the current
in the armature of the magneto is close to the peak, Fig. 39.
The maximum current and voltage are generated when the arma-
ture has turned a few degrees further.

76 GASOLINE TRACTORS

Testing Low- Tension Magneto. To test the armature to find
out whether it is generating or not, attach a short piece of copper
wire to its terminal, place the bare end of this wire against the
field magnet, and rotate the armature. Pull the wire away from
time to time, and a good spark will follow if the magneto is in
good order. If this proves to be the case and the spark still
fails to occur at the plug, the position of the armature should be
noted at the moment that the plug breaks, and if this does not
correspond with the position shown in Fig. 39, the magneto
should be retimed. The plug itself may be tested by taking it
out and laying it on the cylinder. With the magneto running,
the electrodes may be snapped apart. Should they fail to spark,
all other parts of the system being in good working order, it is
usually due to the insulation of the plug. A spare plug should
be inserted and the insulation of the old one replaced as soon as
the opportunity arises. By carrying spares, much valuable time
in the field may be saved.

High=Tension Magnetos. Two Types. Two types of high-
tension magnetos are employed for tractor ignition: one in which
both windings are placed directly on the core of the H-type
armature, so that the windings, core, and condenser rotate
together; and the other, the so-called inductor type in which the
winding is stationary while the rotor in two parts revolves on
either side of it. The first type illustrates the elementary elec-
trical principle that rotating a coil of wire through the lines of
force of a magnetic field will induce a current in the wire. The
current thus induced in the primary winding of the coil on the
armature is tnmsfonned to one of high voltage by the secondary
winding which is also on the armature. The gear shown at the
right-hand end of the armature is for the purpose of driving the
distributor disc, the function of which is explained later.

The rotor and winding of an inductor type of magneto, the
K-W, are shown in Fig. 10, while a phantom view of the complete
machine is given in Fig. 41. It will l>e noted in Fig. 40 that the
rotor consists of two blocks of iron placed at right angles to one
another with the winding between them. In Fig. 41 the con-
denser is at the left of the winding, while the contact box and
the distributor of the magneto are at the right. The operation of

GASOLINE TRACTORS

the inductor type of magneto is based on the principle that
rotating a magnet so that its lines of force cut the winding of a
coil will induce a current in the latter. The magnet in this case
is the rotor, the members of which form part of the magnetic
circuit of the machine. They are most strongly magnetic when in
the position at which the current of any magneto is at the maxi-
mum, as previously explained in connection with the low-tension
magneto. The rotor takes its magnetism from the permanent
magnets of the field in the same way that an ordinary horseshoe

Fig. 40. Rotor of K-W Inductor Motor
Courtesy of K-W I;/ nil ion Company, Cleveland, Ohio

magnet will render an iron nail magnetic as long as they are in
contact.

High- Tension Circuit. The wiring of a true high-tension
magneto, that is, one that has both the primary and the secondary
windings embodied in the magneto itself, is almost as simple as that
of the low-tension type already described; in the high-tension
system one wire is necessary for each plug and in the low-tension
system a single cable connected to a busbar in contact with all
the ignitors is needed. But in the high-tension system these wires
carry current at very high voltage and the slightest defect in the
insulation or the presence of dampness is apt to permit this high-
tension current to leak away, usually without giving any sign of
its escape.

The primary circuit of a high-tension system consists of the
primary winding on the armature, whether stationary or rotating,

GASOLINE TRACTORS

the condenser, and the contact breaker. The secondary circuit
consists of the secondary winding (whether located on the arma-
ture of the magneto itself in the form of a coil placed under the
arch of the magnets in the magneto or placed independently of
the magneto), the distributor, the cables leading to each of the
spark plugs, and the safety spark gap. It will be noted that
each case represents but one side of a circuit. The other side-
is grounded, that is, the current returns through the metal of the
magneto in the primary circuit and through that of the motor

Fig. 41. Phantom View of Complete K-W Inductor Magneto

Ciiurtr::i/ nf A"- 1'/ lynition Company, Cleveland, Ohio

and the magneto in the secondary. Thus a spark plug with a
cable attached completes the circuit when it is screwed into the
cylinder.

Contact Hmikrr. Regardless of detailed differences in their
construction or design, all high-tension magnetos operate on the
same principles, and in every case the contact breaker is the part
of the magneto on which its continued operation depends. In
Fig. 42 is shown a complete high-tension ignition system con-
Ming of a K \Y magneto and its connections for a four-cylinder
motor. The contact breaker details are plainly shown just below
the distributor of the magnet^,: C is a cam carried on the end of
the magneto armature shaft; R is a roller carried at the center of a
hinged arm which is pivoted at its right-hand end and is designed

GASOLINE TRACTORS

to minimize wear on the cam. At its left-hand end this same
hinged arm carries a platinum contact point designed to make
contact with a similar point that is held stationary, but is adjusta-
ble for wear. The hinged arm and the stationary contact point
are attached to the contact breaker box A, which may be turned
through a partial revolution in either direction to advance or
retard the time of sparking.

The circuit through the primary winding on the armature is
completed when the contact points P are together, and it will be

-ENGINE CYL/NDERS

SECONDARY W/ftES TO
5/^/f/f PLUGS

MAGNETO

Fig. 42. Ignition Circuit of Four-Cylinder Motor
Courtesy of K-W Ignition Company, Cleveland, Ohio

noted that they are in contact with each other as long as the
cam C is horizontal, so that current is flowing in this circuit.
When the cam C turns so that it becomes vertical, it corresponds
to the position of maximum current in the armature winding and
the circuit is suddenly opened at that moment. This breaking of
the current provides the impulse necessary to induce the maxi-
mum current and voltage in the secondary winding. At the same
moment that the contact breaker opens, provided the motor is
designed to turn to the right, or clockwise, the distributor contact
B is passing close to S, which is the terminal representing the
spark plug of cylinder 1. If it is a left-handed motor, the^dis-

GASOLINE TRACTORS

tributor contact B will be at the sparking point for cylinder 4
at S'. There is accordingly a path open for the high-tension
current to the spark plug. As the distributor is driven directly
from the armature of the magneto by gearing, Fig. 43, the dis-
tributor contact is at a point corresponding to the cylinder that is
to be fired each time the contact breaker opens.

Firing Order. While these points on the distributor are num-
bered consecutively from 1 to 4, the cylinders of a four-cylinder
motor cannot be fired in that order since the cranks of a four-
cylinder four-cycle motor are spaced at 180°. In other words,
there are two in one plane and the other two are in the plane

Fig. 43. Distributor End of K-W Magneto
Courtesy cf K-W Ignition Company, Cleveland, Ohio

opposite, or half a revolution away. Consequently, cylinders in
the same plane cannot follow one another in firing. This is made
plain in the circuit diagram, Fig. 42. From this illustration it is
evident that cylinders 1 and 4 have their cranks in the same
plane, so that the cylinder to fire after cylinder 1 must be either
2 or 3. It will also be noted that contact 3 of the distributor
corresponds to cylinder 4 of the motor, so that the firing order
of this motor is 1, 2, 4, 3. The firing order most commonly
adopted for four-cylinder motors is 1, 3, 4, 2 since this produces
a somewhat better impulse balance by distributing the successive
explosions among cylinders at equidistant points on the crankshaft.
In checking up the ignition or making any repairs it is important

GASOLINE TRACTORS 81

to know what the firing order of the motor is, and this will usually
be found stamped on it in some conspicuous place.

Care of Magneto. Since modern high-tension magnetos have
their shafts mounted on ball-bearings, they require very little oil
and that only at infrequent intervals. A few drops once a week
in the case of some and once in two weeks with others is all
that is necessary so far as lubrication is concerned.

The contact breaker is the most important part of the mag-
neto and is the one that should be looked to first whenever the
magneto fails to deliver a spark at the plugs, all other essentials
of the system being in good condition. Long continued operation
at full load is apt to burn the contact points away to such an
extent that they do not come together when the cam is in the
horizontal position. Or they become so pitted and covered with
oxidizing material, which insulates them, that the current cannot
pass even though they make contact. The contact points should
be kept true and bright with a very fine thin file or with a strip
of fine sandpaper, taking care to remove all traces of dust from
the contact box by cleaning it out with gasoline or kerosene.
Since the points are made of very expensive material, when they
are trued up no more metal should be removed than is necessary
to bring the surfaces squarely together. Much better service will
be obtained from the magneto if this operation is carried out at
frequent intervals, say once a month when the tractor is being
used steadily, instead of waiting until the points get in such a
condition that the magneto will not operate at all. If the contact
points burn away very rapidly, it is an indication that the con-
denser has broken down and should be replaced. This is usually
a job that must be referred to the magneto manufacturer. Apart
from the attention required by the contact breaker, the only care
that it is necessary to give the magneto is to keep it clean and well-
oiled and see that its connections are always tight.

Spark Plugs. Regardless of how well every other part of
the ignition system is working, a spark will not occur in the cylin-
der unless the spark plugs are in good condition. The spark
plug is the business end of the entire system since its failure will
render useless the perfect functioning of every other part. As
will be noted in the sectional view, Fig. 44, a spark plug consists

GASOLINE TRACTORS

of two electrodes with a gap between them across which the
current must jump in order to ignite the fuel in the cylinder.
One of these electrodes is the outer shell of the spark plug itself
and completes the circuit through the ground return when it is
screwed into the cylinder head. The other, or central electrode,
is connected directly with one of the points on the high-tension
distributor of the magneto, so that the path of the current is
down through this central electrode, across the gap to form the
spark and back through the body of the motor to the magneto,
which is also grounded by being bolted to the motor.

Importance of Insulation. No spark plug can be any better
than the insulation which separates the two electrodes since the
entire operation of the plug depends upon its pre-
venting the escape of the current before reaching
the gap. Like any other force under pressure, elec-
tricity will always seek the line of least resistance,
and as compressed air has a higher electrical resist-
ance than any solid insulator, the slightest leak in
the insulation will open a path for the current and
no spark will occur at the gap.

Heat, vibration, hot oil, and soot are all enemies
of the insulation, and under their combined attack-
it is bound to break down sooner or later. Soot,
or carbon, which is an excellent conductor of elec-
tricity, is the commonest cause of spark-plug failure,
but it does not necessarily put the plug out of
commission for good. It is particularly difficult to
prevent the accumulation of carbon on the ends of the plugs in
an engine burning kerosene, but a good cleaning with a fine wire
brush and plenty of gasoline is usually all that is necessary to
restore them to service.

Common Plug Troubles. Apart from the difficulty of short-
circuiting due to carbon collecting on the ends of the plugs, the
commonest causes of trouble are due to a hidden breakdown of
the insulation and to the burning away of the electrode points,
so that the resistance of the gap becomes too great for the current
to bridge. Porcelain is one of the best insulators known for the
purpose, but it is difficult to make a porcelain that will witli-

Fig. 44. Sectional

View of a Spark

Plug

GASOLINE TRACTORS 83

stand the intense heat and the vibration indefinitely, particularly
as the material is already under stress due to the screwing down
of the gasket nut of the plug in order to make it gas tight.
When it becomes intensely hot, the vibration and pounding are
apt to open fine invisible cracks in the body of the porcelain.
The carbon is forced into these and forms a conducting path for
the current. As this carbon cannot be cleaned out, the plug is
useless until a new porcelain has been inserted.

In the same manner, the hot oil carrying a considerable per-
centage of carbon particles is forced into the mica insulation of
a plug until it becomes so impregnated with this conducting
material that it will no longer spark. Only the replacement of
the electrode and its insulator will cure the trouble. Failure to
spark due to the electrode points having been burned too far
apart sometimes makes itself apparent by the current visibly
passing over the outside of the plug. That is, instead of jump-
ing the gap inside the cylinder, the current finds a path of less
resistance across the surface of the insulator. This will sometimes
occur when a plug gets extremely hot, even though the points
are properly spaced, and since water is a good conductor, it will
always take place if the slightest amount of moisture is allowed
to fall on the porcelain of the plugs. Dirty oil will also provide
a conducting path. When the electrode points have burned too
far apart and no indication is visible at the plug itself, the spark
will be noticed jumping the safety spark gap on the magneto.

Under the continued heavy service of a tractor engine that
is being used for plowing ten hours a day and six days a week,
it will be nothing unusual to have to adjust the spark plug
points two or three times a week, particularly where cheap plugs
are used, since the electrodes are of common iron and burn away
very quickly. It is poor economy to buy cheap spark plugs, though
it is not so great a sin as to buy cheap lubricating oil. The latter
besides damaging the motor in other wrays will cause added
trouble with spark plugs of any kind owing to the excessive
amount of carbon that accumulates in the cylinders. Leakage of
compression through the plugs must be prevented by turning
down the nut at the base of the porcelain to seat it on the
gasket, but this must be done carefully or the porcelain will break.

84 GASOLINE TRACTORS

Wiring. Moisture and oil are also enemies of the insulation
of the high-tension cables that connect the distributor terminals
of the magneto with the plugs. These cables must be kept clean
and dry and their terminals at both ends must be kept tight
with the cables in a position where they do not come into con-
tact with one another or with the body of the engine as far as
possible since despite the thickness of the rubber and the cotton
insulation the high-voltage current will find a path through it at
the slightest opportunity. When the cables have become soaked
with oil and dirt, it is better to discard them and replace them
with an entire new set as the value of the insulation has been
destroyed to a large extent.

In order to make the cables flexible, they are made up of a
large number of fine copper wires stranded together. When the
cables become frayed at the ends next to the plug terminals,
particularly, it is nothing unusual for one or more of these very
fine strands of copper to project against the body of the plug or
some other metal and thus cause a short-circuit that is not
noticeable. Both ends of the cables should be well taped at the
terminals to prevent this. Contact with any moving parts must
be avoided as even a slight amount of wear on the insulation
will lower its resistance to a point where the current will find a
path through it. This is particularly true of cuts that penetrate
both the cotton and the rubber, but which may be so small as
to be imperceptible. Despite their size the current will leak
through them if the cables come in contact with any metal
parts since almost any path of this kind will present less resist-
ance than does the gap of the spark plug, especially when the
latter has been burned open 'too far.

Magneto Impulse Starter. Owing to the fact that it is not found
practical in the majority of instances to carry a storage battery on
a tractor, while the average tractor motor cannot be cranked fast
enough by hand to start it with the ordinary magneto, an attach-
ment has been designed for the latter .by means of which it may
be caused to generate sufficient current for a hot spark regardless
of the speed of the engine. This is known as an impulse starter.
It consists of a spring mechanism, which, when the engine is
cranked, is automatically released, causing the magneto armature

GASOLINE TRACTORS 85

to turn through a partial revolution much more rapidly .than the
crankshaft.

Bosch. The details of the Bosch impulse starter are shown in
Fig. 45, while Fig. 46 illustrates the magneto complete as equipped
with the starter. Referring to the detail view Fig. 45, it will be
noted that a dish-shaped flange is attached to the armature shaft
and that this flange carries two cams on its periphery. In the
view at the right is shown the crossbar member which forms an
integral part of the starter driving shaft. The squared ends of
this bar fit the openings of the flange mentioned. This bar floats
on the helical springs shown, which are held in a circular recess
and are secured to the starter shaft, which is also the main driv-

Fig. 45. Details of Bosch Impulse Starter

Courtesy of American Bosch Magneto Corporation,

Springfield, Massachusetts

ing shaft, as is made clear in the assembled view of the magneto.
The operation of this starter is controlled by a latch forming part
of ' the external engagement lever, which is .shown projecting
upward. When it is not desired to operate the impulse starter,
this latch is held away from the cams by a trigger. Releasing the
trigger drops the latch, and the starter, or coupling shaft, is
revolved, causing the spring to be compressed. Since the crossbar
is held stationary, the armature does not revolve. By moving the
small lever to the release position, the springs are freed and they
give a rapid partial turn to the magneto armature. When the
engine speed exceeds 150 r.p.m., the speed at which the cams
strike the lever is sufficient to cause it to fly up out of the posi-
tion where it is held by the trigger, so that the magneto operates

80 GASOLINE TRACTORS

in the usual manner. For starting large engines, it is customary
to prime the cylinders with gasoline; the impulse starter lever is
then moved over to the engaged position and let go. The engine
is cranked to bring the piston in a cylinder that is about to fire a
few degrees beyond the upper dead center on the firing stroke-,
and then the starter lever is pushed to the release position, caus-
ing a spark to occur in the cylinder under compression. To facili-
tate starting in this manner, a check mark may be made on the
My wheel to indicate the starting position.

/•'iwmann. In Fig. 47 is illustrated the mechanism of the
Kisemann magneto impulse starter, in which a spiral spring is
employed as the driving element. For greater clearness, this

Fig. 4(>. Bosch Magneto Equipped with Impulse Starter

Courtesy nf Awn'rati Bosch Magneto Corporation, Xpringfirlil,

Massachusetts

spring is indicated by dotted lines. The spring N is attached to
the members II and (', the former being the housing attached to
the magneto shaft and the latter the driving member; J> is a fixed
bar which is mounted on the base of the magneto; and 7 is a
floating member, or trigger. When the motor is cranked slowly,
the trigger T drops by gravity, engaging the bar II and temporarily
preventing the rotation of the housing //. Since C is driven by
the engine, cranking causes it to compress the spring, or wind
it up, until the cam on (' strikes the wedge IF. This forces the
trigger upward until it slips off the lower bar, thus releasing the
housing // and causing the spring to give the armature a sharp
partial turn. The right-hand illustration shows the relation of the

GASOLINE TRACTORS

members after the spring has been released and the magneto
starter is in its normal running position. Stops are provided on
the housing and the outer part of the driver C to prevent the
armature from being turned past the position it must maintain to
be properly timed to the engine. To hold the starter out of
operation while the engine is running, T is heavily counterbalanced
and as a result the action of centrifugal force on it draws the part
T further in until the detent on it, shown just above the trigger

ig. 47. Impulse Starter on Eiscmann Magneto

< '<»ir!(.--i/ of Eixrnxiini .l/V/'/Mr/n C'nmjtnn )i, Rr»nkh/n, Nnv York

itself, enters the notch N in the driving member C, where it is
held as long as the magneto runs at its normal speed. As this
notch provides a positive drive for the magneto independently of
the spring, the starter acts merely as a coupling when running.

TYPES OF MOTORS

Wide Range of Types. When gasoline-driven tractors were
first placed on the market with a view to providing a machine
that could be more widely used than the steam tractor, they con-
sisted of little more than a single-cylinder stationary gasoline
engine on wheels. While tractor design has advanced considerably
since that time, it is still a long way from having reached any
standard as far as the power plant is concerned. Meanwhile, the
automobile engine has undergone tremendous improvement, while
its manufacture is now carried out on a scale that was not dreamed
of fifteen years ago. As a result, the tractor engine has been
developed under the influence of two widely separated standards,

88 GASOLINE TRACTORS

first, that of the stationary engine builder and second, that of the
automobile engine manufacturer. There is, consequently, a wide

Fig. 48. Two-Cylinder Horizontal Motor Used on 20-40 Oil-Pull Tractor
Courtesy of Advance-Rumely Thrcshfr Company, Inc., Laporte, Indiana

Fig. 49. Interior of Crank Case, Oil-Pull Motor
Courtesy of Adtance-Rumchj Thresher Company, Inc., Laporte, Indiana

range of engine types used for tractor propulsion. At one end of
this range there is the descendant of the original stationary
engine, made more compact and with additional cylinders to provide

GASOLINE TRACTORS

the needed extra power without excessive weight, while at the other
extreme there is the light, high-speed, multi-cylinder motor, which
to all intents and purposes is practically an automobile engine.
Horizontal Engine. Oil-Pull. To a large extent the horizon-
tal engine is an outgrowth of stationary engine practice. A repre-

Fig. 50. Section of Eagle Two-Cylinder Horizontal Motor
Courtesy of Eagle Manufacturing Company, Appleton, Wisconsin

sentative example is illustrated in Fig. 48, which shows the 20-40
Oil-Pull engine. The cylinders are cast with separable heads and
the valves, located in the latter, are operated by rocker arms.
The carburetor, or fuel mixer, the magneto, the force-feed oiler,
and the circulating pump are all placed on top of the motor for

90 CASOLIXK TRACTORS

greater accessibility. Since splash lubrication cannot be used
owing to the position of the cylinders, force-feed oilers with leads
directly to each of the bearings are commonly used on this type
of engine. In Fig. 49, is shown a head-on view of the same motor
with the crankcase removed, showing the crankshaft and bearings,
the camshaft and timing gears. The magneto, the circulating
pump, and the force-feed oiler are also driven by the gears. In
this engine the cylinders are slightly offset to reduce the pressure
on the cylinder walls during the firing stroke.

Eagle. A clearer idea of the internal details of this type of
engine is obtainable from the sectional view, Fig. 50, showing an

Fig. 51. Avery Two-Cylinder Horizontal Opposed Motor
Courtesy of Arery Company, Prnrin, Illinois

Kagle two-cylinder motor. The upper cylinder has been sectioned
through the center line of the piston, showing the piston pin and
the inside of the valve cages, while the lower one illustrates the
complete piston with its rings and the removable valve cages in
the cylinder head. Whether it be horizontal or vertical, one of
the advantages of the valve-in-head type of motor is the ease with
which the valves may be kept in condition, grinding-in being an
operation that must be carried out at frequent intervals on a
tractor engine.

Horizontal-Opposed Awry. The horizontal opposed type was
largely used on automobiles for several years during the early
period of their development in this country. It provides better
impulse and mechanical balance than the two-cylinder type in which

Fig. 52. Engine of Holt Caterpillar Tractor
Courtesy of Holt Manufacturing Comp'inu, Inc., Peoria,

Fig. 53. Parts of Tracklayer Tractor Engine
Courtesy of C. L. Best Gas Tractor Company, San Leandro, California

GASOLINE TRACTORS

the cylinders are placed side by side and is accordingly freer from
vibration. In Fig. 51 is illustrated the A very two-cylinder motor
of this type, which is also built with four cylinders in the larger
sizes. A novel feature of the Avery motor that overcomes the
disadvantage to which this type was subject on the automobile is

Fig. 54. Automobile Type Engine of Parrett Tractor
Courtesy of Parrett Tractor Company, Chicago Height?, Illinois

the use of removable cylinder liners. Owing to the weight of the
piston resting on the lower half of the cylinder wall the latter
wore out of round more rapidly than would the cylinders of a ver-
tical engine in the same service. This destroyed the compression
and involved the reboring of the cylinders and the fitting of over-
size pistons. The A very cylinder liners are cast of harder metal

GASOLINE TRACTORS

than the cylinders themselves and may be given a part turn from
time to time so as to distribute the wear over the entire wall,
while the liner itself may be replaced readily.

Vertical Motors. Holt and Tracklayer. All the horizontal
motors described are specially designed for tractor service by the
manufacturers of the tractors themselves and produced in their
own shops. With comparatively few exceptions, most of the ver-
tical types of tractor motors are the products of the various large

Fig. 55. Section of Moline Four-Cylinder Motor
Courtesy of Moline Plow Company, Moline, Illinois

automobile motor factories and are designed along lines that
closely follow practice in the automobile field. One of these
exceptions is the Holt motor shown in Fig. 52, while another of
very similar design is the power plant of the Tracklayer tractor.
Some of the construction details of this motor are shown in
Fig. 53, which illustrates a cylinder casting, cylinder head with
valves, piston, piston pin, and the cylinder head and manifold
gaskets. Both of these motors are specially designed and built

GASOLINE TRACTORS

for tractor service and are of the slow-speed type best adapted for
carrying a large percentage of their maximum load continuously.
Parrett. The Parrett motor shown in Fig. 54, while also
designed for this service, follows automobile practice more closely.
It is shown with the cylinder head casting and the crankcase oil
pan removed to illustrate the accessibility thus obtained. Its
smaller size and greater compactness is accounted for by the fact
, . that it is a high-speed type, de-

signed to produce its normal rated
output at 1000 r.p.m.

Moliw'. Another motor of this
class is the Moline, which is shown
in longitudinal section in Fig. 55
and in cross-section in Fig. ">(>.
These illustrations are taken from
the Moline instruction book and
the identification figures serve to
make clear the functions of the
various parts of a motor. From
1 to J in Fig. 55 they refer to
the lubricating system, as follows:
1, oil level in crankcase; 2, suction
pipe to oil pump; 3, oil pump; /h
oil conduit drilled through the
crankshaft; and 5, oil lead to crank-
pin bearings. Numbers 6 and 7
are the driving pinion and gear o!
the timing gear; 8, a bevel gear for
the belt pulley of the tractor; 9, a
valve tappet; 10, the valve mech-
anism chamber; and 11, the oil
cap filler and breather. The latter admits air to the crankcase and
is a necessary feature of all motors but is usually located directly
on the crankcase itself. It is one of the points that must be care-
fully guarded against the entrance of dust and grit to the interior
of the motor.

In Fig. 5(> / is the oil screen; J, the suction pipe to the oil
pump; .1, the oil hole to the rrankpin bearing; ./, the crankshaft;

Fin. ~>G. Cross-Section of Moline Motor
Courtesy of Moline Plow Company,

Mnlinr. Illinois

GASOLINE TRACTORS

5, the crankpin; 6, the combustion chamber of one cylinder; 7, a
valve; 8, the valve spring; 9, the rocker arm of the valve linkage;
and 11, the rocker arm stud; 10 is the intake passage. The details
of the crankshaft and piston assembly are shown in Fig. 57, in
which 1 is the oil outlet hole from the drilled crankshaft at the
forward crankshaft bearing; 2, the oil intake hole at the rear

Fig. 57. Crankshaft and Piston Assembly of Moline Motor

crankshaft bearing; 3, a series of threads designed to work the oil
backward into the crankcase and prevent its entrance into the
clutch housing; 5, the helical half-time gear for driving the cam-
shaft and auxiliaries; and 6, the bevel pinion for driving the belt
pulley. The bolts for fastening the flywheel to the crankshaft
flange are identified by 4-

GASOLINE TRACTORS

PART II

CONTROL SYSTEM
ENGINE GOVERNORS

Need of Governors. Plowing. In order that a tractor may
be operated most economically, it must be capable of one-man
control since, in plowing, conditions are continually encountered
where the driver's attention must be centered on the management
of the plows and the steering of the machine to the exclusion of
everything else. Moreover the demands upon the engine are con-
tinually varying even when the soil conditions are apparently uni-
form for long stretches. Stones, roots, and extra heavy patches
of sod all impose considerable extra load on the engine that can
be met satisfactorily only by an automatically controlled throttle
if a uniform plowing speed is to be maintained.

Belt Work. A far greater load variation is encountered in
belt work than in plowing, as in the former the engine may be
running practically idle at one moment and be almost choked
down by overloading the next, whereas in the latter there is
always a load on the engine and therefore the danger of racing is
absent. Irregular speed under changing load, racing of the idle
engine, and tardy opening of the throttle to meet the increased
load, all of which are unavoidable with hand control, represent
conditions of operation which not only reduce production at the
machine being driven but are very bad for the engine itself as
they result in overheating, prevent proper lubrication, and, not
infrequently, result in burned-out bearings. In any case the pro-
vision of a governor on the engine releases a hand for other and
more productive labor. The majority of tractors go into service
in the hands of an unskilled operator, and unless there is a governor
on the engine, his course of instruction is likely to be marked by
the occurrence of more or less damage that automatic control
would prevent.

GASOLINE TRACTORS

Centrifugal Governors. Despite almost innumerable attempts
to displace it, the centrifugal principle first taken advantage of
more than a century ago to control the speed of a steam engine is
still in almost universal use for this purpose. Most tractor
engines are equipped with what is commonly termed a fly-ball
governor, though the details of the mechanism and the character
of the throttle valve it is employed to control differ more or less.
In its simplest form such a governor consists of two weights on
the end of oppositely placed arms which are pivoted on a spindle
connected to the throttle valve, either directly or through suitable
linkage, so that any movement of the weights is communicated
directly to the throttle. On a stationary engine the governor may

Fig. 58. Simplex Engine Governor
< '<nirti'.--i/ <if Duplex Engine Governor Company, Brooklyn, New York

be placed upright and is not subjected to vibration or jolting, so
that gravity alone may be depended upon to keep the weights in
their normal position, but on the tractor springs are usually
employed, and the governor may then be placed in any position.
When running below a certain speed, either gravity or the pull of
the spring is sufficiently strong to keep the weights together against
the shaft or close to it. But as the speed increases, centrifugal
force acts on the weights and tends to make them assume a posi-
tion at right angles to the shaft. The faster the engine runs, the
closer the weights approach to this position, but as their move-
ment brings about a proportionate closing of the throttle, the
engine is not given an opportunity to increase its speed. A well-
balanced u'ovcrnor of this type will operate so sensitively that

GASOLINE TRACTORS 99

there will be practically no perceptible change in speed between
idling and full load. So far as the tractor is concerned, centrif-
ugal governors are of two general types, those that are an inte-
gral part of the design of the engine and are built right into it
and those that are in the nature of auxiliary devices designed to
be attached to the inlet manifold between the carburetor and the
intake valves.

Auxiliary Types. The Simplex governor, shown in Fig. 58,
and the Pierce, illustrated in Fig. 59, are examples of governors
designed to be adapted to any make of motor, the only modifica-
tion necessary depending upon the details of the drive, since the
governor must be driven directly from the motor itself. In the

Adjusting Screw Diaphragm Bali Bearing

Bell
Cran*

Shaf

Spring

Fig. 59. Section of Pierce Engine Governor
Courtesy of Pierce Governor Company, Anderson* Indiana

Simplex the governor weights, which are housed in the casing just
under and to the left of the oil plug shown, operate a grid valve
the openings of which appear in the intake manifold flange at the
left. The driving attachment, designed in this instance for a
flexible shaft drive, appears at the right. Fig. GO shows the
attachment of a Simplex governor to a Continental motor, the
drive in this case consisting of a solid shaft and bevel gears
operating from the camshaft. The governor is set for the maxi-
mum speed to which the motor on which it is mounted is best
adapted and is then sealed, as shown at the left end. As the
governor mechanism runs in a bath of oil, it requires no attention
vxt-ept to replenish the oil from time to time,

Fig. 60. Installation of Simplex Governor on Continental Motor of Bullock Tractor
Courtesy of Bullock Tractor Company, Chicago, Illinois

Fiji. (>1 . Installation of Pierce Governor on Buda Motor
Courtesy of Pierce Governor Company, Anderson, Indiana

101

GASOLINE TRACTORS

The Pierce governor, which is.1 sh</\vn, iij tK-jr
operates a conventional butterfly type of throttle valve such as is
used in the majority of carburetors. This valve is shown at the
left, while the weights and the driving attachment are at the right.
Between the two is the spring against which the centrifugal force
of the revolving weights must act to close the throttle. Just above

Fig. 62. Built-in Governor of Creeping-Grip Tractor
Courtesy of Bullock Tractor Company, Chicago, Illinois

the left-hand end of this spring will be noted a screw adjustment
by means of which the speed for which the governor is set may be
altered. Increasing the tension of the spring by screwing this in
permits an increase in the speed of the motor since the weights
must then revolve at a higher speed in order to overcome the pull
of the spring. This is the principle upon which the adjustment of

102

TRACTORS

all ccntT:('i:u';! gn\ rrno'-s is based. One method of attaching the
Pierre governor is illustrated in Fig. 61, which shows it mounted

on a Buda motor and driven
through bevel gearing from the
camshaft.

Built-in Types. The part
sectional end view of the engine
of the Creeping Grip tractor,
Fig. 62, illustrates an excellent
example of a built-in governor.
This is driven from a transverse
shaft which takes its power
through helical cut gearing from
the timing gear of the motor, the
same shaft also serving as the magneto drive. In expanding,
the revolving weights draw in the sliding shaft shown, which is
linked to a bell-crank lever at its outer end. The lever is attached
to the throttle, which will be noted just to the right of the carbn-

Mir. IK5. Governor and Magnetic Unit of

Creeping-Grip Tractor Motor

Conrtrxy of Bullock Tractor Compn-n;/,

Chicago, Illinois

Fig. C4. Emerson-Brantingham Motor, Showing Governor
Courteay of Emerson-Brantinoham Company, Rockfor/1. Tlltnnix

retor. This bell-crank lever is also attached by linkage to a dash
pot to prevent the governor from "hunting/1 or "surging." as it is

GASOLINE TRACTORS 103

variously termed) that is, fluctuating violently over a wide speed
range. This governor is designed to control the speed of the
motor between a minimum and a maximum of 400 to 700 r.p.m.
and is adjustable by means of the hand lever shown in Fig. 63,
which illustrates the combined governor and magneto unit before
attachment to the motor.

In Fig. 64, which shows the complete power plant of the
Emerson-Brantingham 12-20 tractor, is illustrated another type of
built-in governor, the details of which are clearly shown. This
governor is driven by a belt and is of the usual steam-engine type
in which the weights are carried on leaf springs, the movement
being transmitted to the throttle through the linkage shown.

TRACTOR CLUTCHES

Functions of Clutches. Since the internal combustion motor
cannot be started under load and will stall if the load be applied
too suddenly, even though the engine is developing its full power,
it is necessary to employ a means of picking up the load gradually
as well as of connecting or disconnecting the motor from the load
as desired. This means is the clutch; and clutch problems on the
tractor are the same in kind but greater in degree than those
encountered on the automobile since the load to be started is so
much greater. An automobile need start its own weight only and
in doing so it encounters but slight rolling resistance, whereas the
tractor must not only get a very much greater weight under way
but in starting it must overcome the far greater resistance repre-
sented by the plows or other load and also that of the ground
itself, .

As a general rule the types of clutches employed on tractors
are the same as those used on automobiles, but they are given a
considerably increased area of contact surfaces and these surfaces
are held together under much higher spring pressures in order to
carry the heavier load. Regardless of its type, the principle of
the friction clutch is based upon holding the driving surface
(directly connected to the motor) and the driven surface (directly
connected to the transmission or speed reduction gear) in contact
under a pressure per square inch that is greater than that exerted
by the engine in carrying the load. When the pressure required

104 GASOLINE TRACTORS

to carry the load exceeds that exerted by the clutch spring, the
contact surfaces slide upon one another and the clutch is said to
slip. Unless this slipping took place, some one of the links in the
transmission between the wheels or tracks and the engine would
have to give way or the engine itself would be stalled by the load.
It is accordingly the function of the clutch to slip, first, to insure
gradual engagement in picking up the load and, second, to pre-
vent damage to the transmission or the motor when the load
becomes excessive. The latter function, however, is more impor-
tant in theory than in practice since an excessive load almost

Pig. 65. Transmission Unit of Illinois Tractor Showing Multiple-Disc Clutch
Courtesy of Illinois Tractor Company, Bloomington , Illinois

invariably stalls the motor before the clutch begins to slip, unless
its surfaces have become glazed through wear or its spring has
weakened.

Types of Clutches. In practically every case the flywheel of
the motor itself forms the driving member of the clutch. The
driven member may be a cone faced with asbestos-wire fabric, a
plate faced with similar friction fabric, or a contracting band
similarly faced which is mounted so as to contact with the rim of
the flywheel itself or with that of a smaller drum attached to the
flywheel; or friction-faced shoes may be arranged to expand
against the inner face of the flywheel. The moving force in every
case is the clutch spring. In the order mentioned, these types are
known as the cone, plate, contracting-band, and expanding-band,

GASOLINE TRACTORS

105

or expanding-shoe, clutches. Where a greater contact area is
desired than is afforded by the diameter of the flywheel, a series
of plates or discs is employed. These plates are divided into two
groups, one of which is carried on spindles or bolts attached to

Fig. 66. Section of Dry-Plate Clutch As Used on Moline Tractor
Courtesy of Moline Plow Company, Moline, Illinois

the flywheel and forms the driving member, while the second
group is similarly mounted on members attached to the clutch
shaft and forms the driven member. When in engagement, the
two groups are pressed together by the clutch spring in the same
manner as m other types of clutches. This clutch is known as the

106

GASOLINE TRACTORS

multiple-disc type, and in -....me instances it operates in a bath of
lubricating oil, the latter being squeezed from between the plates
as they come in contact, thus ensuring gradual engagement. In
Fig. 65 is shown the multiple-disc clutch of the Illinois tractor,
the clutch being the small group of plates shown at one end of the
transmission unit.

Plate Type. The sectional diagram, Fig. 66, not only serves
to illustrate the details of the dry-plate clutch but also makes
clear the principles of clutch operation. This is the Borg and
Beck clutch as used on the Moline tractor. One of the asbestos

Fitf. <>7. Main Clutch of Holt Caterpillar Tractor
Cniirtisi/ ,'f Knit MtnnifiK-tiirin'/ f'i>mj>fin>j, Inc., Prorin, Illinoix

rings shown is attached to the flywheel, while the second ring is
carried on the driven clutch member, while between the two is the
clutch disc, which is a, ring or disc of steel also attached to the
clutch shaft. By means of the collar and toggle levers which mul-
tiply the force exerted by the spring, this clutch disc is clamped
between the two asbestos rings when the clutch is engaged. The
backward pressure, or reaction of the spring, is taken on the hall
thrust bearing shown, this being an essential of all types of cone
or plate clutches since otherwise this back pressure of the spring
would cause considerable frictional resistance to the revolution of

(1ASOL1XK TRACTORS

107

the clutch shaft. The screw marked A is an adjustment to main-
tain the distance B indicated, this distance being necessary for
the complete release of the clutch when disengaged.

Expanding-Shoe Type. The Lauson tractor clutch affords an
example of the expanding-shoe type which calls for very little

MOTOR SUDE
SPEED CHANGS

Fig. 68. Friction Transmission of Heider Tractor
Courtesy of Rock Inland Plow Company, Rock Island, Illinois

explanation. Against the inner face of the flywheel are two
pivoted shoes which are counterbalanced. These shoes are faced
with asbestos brake lining and are designed to be held in contact
with the inner face of the flywheel rim by means of the toggle
mechanism shown. The spring has the same location as in other

108 GASOLINE TRACTORS

types of clutches, while its purpose, like that of other clutches, is
to hold the clutch friction surfaces together under a pressure
greater than that exerted by the engine in driving the tractor
under load. The main clutch of the Holt caterpillar tractor is of
a similar type, Fig. 67.

Contracting- Band Clutch. Neither the contracting-band nor
the cone clutch calls for much description. The contracting-band
clutch is practically a duplicate of the usual brake mechanism in
which a friction-lined band is pressed against a revolving drum to
bring the latter to a stop. In the case of such a clutch the object
is to bring the contracting band to a stop on the drum, which is

L ^f

Fig. 69. Bevel Friction Transmission of Square Turn Tra< tor
Courtesy of Square Turn Tractor Company, Nor foil:, Xrl>ru»/.'<i

the flywheel, so that both the band and the flywheel revolve
together, this really being the only diiVerenee between the brake
and the clutch mechanism. The contracting band is ;:tt;>ched to
the clutch shaft, or driven member, and when in operation,
revolves with it, thus carrying the load. This clutch is rsed in
connection with a planetary type of transmission and is accord-
ingly familiar through its employment on many thousand Fords.
Cone Clutch. In the cone clutch the inner face of the fly-
wheel is turned to a bevel of approximately ;>() degrees to form
the driving member into which a cone-shaped member with the
same bevel and lined with asbestos or other friction facing is

GASOLINE TRACTORS 109

pressed by the spring. Owing to the necessarily limited area of
friction contact in this type of clutch, a high spring pressure is
necessary where a heavy load must be transmitted.

On the automobile this spring pressure is very much less than
on the tractor owing to the slight resistance encountered by the
machine in starting, so that the clutch may readily be disengaged
with the foot through the medium of a short lever and pedal, but
on any tractor except a very light one the effort required to do
this would be excessive. The usual method of clutch operation on
the tractor is accordingly by means of a long hand lever provided
with a ratchet or locking detent, so that the clutch may be held
out of engagement. Since it does not benefit the spring to keep it
compressed, the clutch should not be locked out of engagement
any longer than is necessary to shift the transmission gears to
neutral', when the clutch should again be allowed to engage.
Holding the clutch out of engagement overnight or while the
tractor is standing in the field subjects the clutch spring to abuse
and will soon 'result in weakening it to the point where the clutch
slips whenever any extra load comes on it.

Friction Drive. While all the types of clutches mentioned
are, in a sense, a friction drive in that friction is depended upon
to transmit the power, the so-called friction drive is one in which
the load transmitting members revolve independently of one
another except for a single point, or line, of contact. This is
made clear by the illustration of the friction transmission of the
Heider tractor, Fig. 68. The flywheel is the driving member, as
usual, but in this case its entire outer rim is covered with a
special friction facing consisting of hard fiber. The flywheel
rotates between two large steel discs, either one of which may be
pressed against it. In this instance the left-hand disc is used for
forward movement and the right-hand disc for backing, or reverse.
It is also apparent that the point at which the flywheel makes
contact with the disc determines the speed at which the latter and
the tractor itself are driven.

In the position shown the tractor speed will be the lowest
provided, since the flywheel is in contact with the outer edge of
the disc, so that the relation of the two is that of a small gear to
a large one and the speed of the latter is reduced. As the fly-

110

GASOLINE TRACTORS

wheel moves toward the center of the driven disc, the relationship
between the two becomes that of driving and driven gears which
approach closer and closer to the same size, so that the speed of
the driven member is increased. This movement of the flywheel
is accomplished by mounting the motor itself on slides on the
frame and moving it backward or forward by means of a large
hand lever. The direction of movement of the tractor depends
upon which disc is pressed against the flywheel.

Both Wheels Forward Both Wheels Reversed Left Wheel Forward Left Wheel Reversed

Right Wheel Forward

Right Wheel Reversed Right Wheel Forward — Left Wheel Forward —

Left Wheel Reversed Rigel Wheel Reversed

The two views above show positions of Bevels and
Cones in making quick short turn either direction

Fig. 70. Details of Operation of Bevel Friction Transmission
Courtesy of Square Turn Tractor Com pun a, Xorfolk, Xebraxl.u

Bevel Friction Drive. The form of friction drive employed on
the Square Turn tractor is shown in Fig. 69. In this drive the
principle is exactly the same as already outlined, except that
friction-faced (fiber) conical members take the place of the fly-
wheel as the driving member and corresponding cones of iron art
the driven members. The design is also modified to permit of
driving either rear wheel independently or both in different direc-
tions at the same time in order to turn short corners. The small
diagrams showing the different relations in which the driving and
driven members may be placed, Fig. 70, explain the operations
much better than a description, A separate hand lever controls

GASOLINE TRACTORS 111

each of the driven discs, or traction members. Moving both of
them forward drives the machine ahead through both driving
wheels; pulling them back reverses the movement; and each may
be used independently, so that one drives forward while the other
is backing, thus turning the machine as if on a pivot.

TRACTOR TRANSMISSIONS

Speed vs. Weight. The power generated in an engine,
whether by the expansion of steam or that of the ignited gases in
an oil engine, is converted into mechanical energy by applying it
to the movement of weight, and the power itself is represented by
the extent of that weight and the number of times per minute
that it is moved. Hence, for a given power the slower the speed
at which the engine runs, the heavier must be the weight moved
since it is set into movement a smaller number of times per min-
ute. By increasing the speed, or number of impulses per minute,
the weight moved can be correspondingly reduced. This fact
explains why 25 hp. may be generated by a single cylinder sta-
tionary gas engine running at 250 r.p.m. or by a four-cylinder
motor running at 1000 r.p.m. and why one motor is scarcely more
than one-eighth the size of the other, although their power output
is the same. The single cylinder engine will weigh 2 tons or more
and will have flywheels of large diameter weighing more than the
total weight of the smaller engine, but both move the same amount
of weight per minute.

Automobile Practice. On the automobile the object of the
designer is to keep the total weight down as much as possible con-
sistent with reliability, so that light high-speed motors running up
to 2000 r.p.m. or higher are employed. Such motors are practical
for automobile use because the speed ratio between the driving
and driven members — the motor and the rear wheels— is not
excessive despite the high speed of the motor.

Tractor Practice. But on the tractor, where the maximum
speed in plowing cannot exceed three miles per hour and is pref-
erably less than that (2J miles per hour is recommended by the
Society of Automotive Engineers and most tractors are designed
to plow at 2| miles per hour), the higher the speed of the motor,
the greater the number of steps required in the gear reduction, and
each step represents a loss of power in friction as well as acldi-

112 GASOLINE TRACTORS

tional parts to wear out. Since the tractor is not subject to the
same weight limitations as the automobile, there is no advantage
in employing a light high-speed motor. Generally speaking, the
slower the speed of the motor consistent with the avoidance of
excessive weight, the better adapted it is to tractor use. The
slow-speed motor running at 450 to 7.10 r.p.m. also .has the further
advantage of subjecting its moving parts to less rapid wear in
service and, other things being equal, should require less attention
to keep in satisfactory running condition.

Function of Transmission. In the section on tractor motors
it has been pointed out that the types in general use belong to
two distinct classes: those which have developed with the station-
ary engine as a basis; and those that are an outgrowth of auto-
mobile practice. In either case the engine will only develop its
normal rated power when allowed to run steadily at a rate close
to its maximum speed. A gear reduction must accordingly be
interposed between the motor and the driving members of the
tractor; the speed of the motor determines how great this reduc-
tion must be, while the space and the limit of weight available
determine what form it will take. Whether consisting of a com-
pact unit such as is used on the automobile or of large pinions
and gears occupying the entire space between the frame members
of the tractor, this speed reducing mechanism is usually termed
the transmission. This name includes everything between the clutch
and the final application of the power to the wheels or the tracks,
which is termed the final drive.

Wide Range of Types. Since tractor motors differ so widely,
there is naturally a correspondingly wide range of types of trans-
missions, the latter varying all the way from what is practically a
duplicate of the gear train used on heavy steam tractors, or road
rollers, to the light and compact gear box used on high-speed
automobiles. A few illustrations of typical examples of each class
will suffice to give an idea of how widely this feature of the trac-
tor varies on different designs. In comparing these, it should be
borne in mind that while increased width of gear face affords a
larger wearing surface to carry the load and large gear diameter
means fewer steps in the reduction, these advantages may be offset
by the exposure of the gears to dirt and mud.

GASOLINE TRACTORS 113

The great differences in size and weight, in many cases where
the same amount of power is to be transmitted, are accounted for
by a similarly great difference in the character of the materials
used. Small pinions and gears running at high speeds must be
made of alloy steels, hardened and toughened by heat treatment,
and must be run in a bath of oil. Large broad-faced gears, on
the other hand, may be made of steel castings or even cast iron,
and it is the usual practice to run them to a great extent without
protection.

Speeds. Since the speed range of the average farm tractor is
necessarily very low, its requirements are usually covered by the
provision of but two forward speeds and one reverse. A few
machines are provided with three speed transmissions, but this is
the exception and is due to the use of either a high-speed motor
or an automobile-type transmission. On low gear, which is equiva-
lent to a forward speed of about one mile per hour, the speed
reduction between the motor and the driving wheels of the tractor
may range all the way from 40-1 to 80-1, that is, the motor
makes 80 revolutions to a single turn of the driving wheels in the
second case mentioned. Such a great difference between the motor
speed and that of the machine itself necessitates a number of gear
reductions, each one of which involves a power loss in itself and
also presents an extra wearing surface that needs replacement
sooner or later. Generally speaking, the lower the speed of the
motor consistent with the avoidance of excessive weight, the less
loss there will be in the transmission of the power to the rear
wheels or tracks, as the case may be. The point below which it
does not pay to reduce the motor speed appears to line between
400 and 500 r.p.m., as beyond that the weight increases all out of
proportion to the advantage gained, while the upper limit lies
between 700 and 800 r.p.m.; that is, a low-speed motor would
govern between these limits, say 450 to 750 r.p.m., and its trans-
mission would be designed to take care of the difference between
750 r.p.m. and the number of turns per minute made by the
driving wheels, which would depend upon their diameter.

A high-speed motor, on the other hand, would run at 1000 to
1200 r.p.in. and its power would fall off very rapidly the moment
its speed dropped below 800 r.p.m. To avoid an excessive number

114

GASOLINE TRACTORS

of gear reductions, the driving wheels of a tractor equipped with a
high-speed motor would usually be made comparatively small,

Fig. 71. Friction Drive of the Port Huron 12-25 H.P. Farm Tractor
Courtesy of Port Huron Engine and Thresher Company, Port Huron, Michigan

GASOLINE TRACTORS

115

which is a disadvantage since such a tractor is constantly climbing
the grade formed by its small wheels sinking into soft earth, or
depressions, and is- accordingly expending a large fraction of its

Fig. 72. Plan View of Avery Transmission
Courtesy of Avery Company, Peoria, Illinois

power in lifting itself rather than in driving ahead. It does not
necessarily follow that a tractor equipped with a high-speed motor
always has small driving wheels, since the reduction in speed
required may be taken care of in the final drive.

11(5

(JASOLIXK TRACTORS

Heavy Types. Those transmissions which, as already men-
tioned, represent a continuance of the practice followed for years
on heavy steam tractors and road rollers are known as heavy
types. Such a transmission is shown in Fig. 71, which gives a plan
view of the Port Huron 12-25 friction-driven tractor. It also
affords an example of a tractor with a comparatively high-speed
engine equipped with large driving wheels. There are three gear
reductions in all: the first will be noted at the left; the second is
from this transverse shaft to a central gear on a shorter transverse
shaft which also carries two small pinions meshing with the hull

Fig. 73. Transmission ana Differential ot 75 HP. Tracklayer Tractor
Courtesy of C. L. Best Gas Tractor Company, San Leandro, California

gears. Ordinarily the bull gears are attached directly to the driv-
ing wheels, but in that location it is difficult to protect them,
while in the present design they are completely encased.

Since a tractor must make very short turns and both wheels
must be driven when going straight ahead, a differential is indis-
pensable. When rounding a short turn, it will be evident that the
wheel on the. outside of the curve must travel a much greater dis-
tance than that on the inside and that if both were driven at an
equal speed, one would be forced to slip ami impose a heavy
^traiu on the machine. If the ground condition were such that
the wheel would not slip, rounding the turn would be difficult.

GASOLINE

In the Port Huron tractor illustrated the differential is located in
the second transverse shaft which carries the pinions meshing with
the bull gears. As changes in speed are effected through the fric-
tion drive, the gears of this transmission are constantly in mesh.
The A very transmission shown in Fig. 72, is another example
of the heavy type, the illustration showing the relation of the
horizontal motor to the transmission. The two forward speed
redactions are represented by the two pinions of different sizes
carried directly on the crank- v^,^ , , :_,

shaft of the motor, while the
reverse speed is the pinion
just forward of these. The
transverse shaft just under
the rear end of the motor
embodies the differential the
1 lousing of which will be noted
at the right. This shaft also
carries the pinions meshing
with the bull gears. The com-
plete power plant is carried on
a sliding frame, and the differ-
ent speed changes are effected
by moving the motor so as to
bring the different pinions into
mesh with the large gear car-
rying the differential.

Intermediate Types. Be-

Fig. 74. Cotta Automobile Transmissicn of Do£-

Chit.-h Type As Used on Four-Drive Tractor

Cinirtem/ of Cotta Transmission Company,

Roclcfjrd, Illinois

tween the heavy types just
described and what is prac-
tically a motor-truck transmission, there are a number of trans-
missions that conform to some degree with automobile gear-box
practice but are built on much heavier lines, for example, the
transmission of the Best 75 hp. tracklayer type tractor shown in
Fig. 73. Sliding gears are employed for the speed changes, and a
bevel pinion and driving gear on the counter-shaft which incorpo-
rates the differential, the internal bevel gear of which shows plainly
in the illustration. A typical automobile-type transmission is the
Cotta, Fig. 74, as used on the Four Drive tractor.

118

GASOLINE TRACTORS

Fig. 75. Transmission and Spring Drive Differential of 10-30 Oil-Pull Tractor
Courtesy of Advance- Rumcly Thresher Company, Inc., Laporte, Indiana

Fig. 76. Transmission of Turner Tractor

Courtesy of Tunur Manufacturing Company, Port Washington,
Wisconsin

GASOLINE TRACTORS

119

A clearer view of the details of the mechanism of a differential
is shown in Fig. 75, which illustrates the Rumely 16-30 transmis-
sion. One of the features of this differential is the use of a series
of eight springs for taking up the shock of starting which will be
noted just inside the large gear. Upon engaging the clutch, these
springs must first be compressed before the load falls upon the gear
teeth, thus cushioning the latter. Other similar transmissions are
the Turner, Fig. 76, the Hart-Parr, Fig. 77, and the* Nilson, Fig. 78.

Fig. 77. Transmission of Hart-Parr Tractor
Courtesy of Hart-Parr Company, Charles City, Iowa

Special Types. In Fig. 79 is shown a plan view of the trans-
mission of the Twin City 25-^45 tractor, a feature of which is the
use of toothed, or clog, clutches, the details of which are clearly
shown. This view also shows the contracting-band clutch used on
this machine. The dome just to the right of and forward of the
flywheel houses the engine governor. Automobile practice is
closely approached in the Yuba transmission, Fig. 80, and in the
Holt caterpillar transmission, the gear box of the 10-ton Holt

TRANSMISSION
CASE COVER

HIGHSPEED
GEAR

ROLLER
BEARING

T3IVING
SPROCKET

BRAKE BAND BRAKE LfVCR

HIGH-SPEED

PINION

BEVEL GEAR

GEAR-SHIFT
QUADRANT

BEVEL PINION

BUA

Fig. 78. Transmission of Nibon

Courtesy of Nilson Tractor Com pan;/

79. Contrae^Bff-Bcad Clutch and Transmission of Twin Cit> Tractor

i if Minneapolis Stcd anil Ma-)iinrry Company, M inru'tipoli.t, Minnesota

Fig. 80. Dual Automobile Type Transmission of Yuba Tractor
Courtesy of Yuba Manufacturing Company, Mary^vUle, California

Fig. 81. Transmission of 10-Ton Holt Caterpillar
Courtesy of Holt Manufacturing Company, Inc., Peoria, Illinois

122

GASOLINE TRACTORS

tractor being shown in Fig. 81. Both these types are of the selec-
tive sliding-gear type generally used in automobiles, the Yuba

Fig. 82. Worm Drive of Sandusky Tractor
Courtesy of Dauch Manufacturing Company, Sandusky, Okie

Fig. 83. Tr:iMs:iii*.xi.>:i of Huber Li^ht Four Tractor
C'oiirti-xif of llulxr Manufacturing Company, Marion, Ohio

transmission clearly showing the individual clutches which are
used in the tracklaying machine to enable the operator to drive
either track separately when turning. A feature taken directly

GASOLINE TRACTORS

123

from automobile practice is the use of the worm drive, Fig. 82. Tke
Huber, Fig. 83, is a type that is in a class by itself. Its details
and method of operation are clearly indicated in the illustration.
Final Drive. As in the case of the automobile there is a
further speed reduction between the engine and rear wheels in the
final drive, but as the speed reduction between the tractor engine
and its driving members, whether the latter be wheels or tracks,
is so great, this cannot take the form of a small pair of bevel

Fig. 84. Sectional View of Emerson-Brantingham Company Transmission, Showing Oil Level
Courtesy of Emerson-Brantingham Company, Roclcford, Illinois

gears. The usual method is to employ bull gears, or internal gear
rings of large diameter which are bolted to the driving wheels and
with which small pinions on the ends of the transverse shafts of
the change-speed gear mesh. In some instances automobile prac-
tice is followed by using a live axle. This is a combination of a
sliding change-speed gear of the selective type with a planetary
gear. The sectional view of the Emerson-Brantingham transmission,
Fig. 84, clearly shows the relation of the selective sliding gears and
the oil level necessary for lubrication.

Fig. 85. Details of Final Drive, or Track of Holt Caterpillar Tractor
Courtesy of Holt Manufacturing Company, Inc., Peoria, Illinois

Fig. 86. Final Drive of C. L. Best Tracklayer Tractor
Courtesy of C. L. Best Gas Tractor Company, San Leandro, California

Fig. 87. Details of Final Drive of Yuba Ball-Trend Trartor
Courtesy of Yuba Jfanif/oefurfof Company, MarysrUte, California

GASOLINE TRACTORS 125

Final drive in tracklaying machines is usually through large
sprockets on the ends of the transverse shaft, these sprockets
meshing in the track itself. The track runs on rollers or balls
and passes around an idler at the end of the tread, this idler
being made adjustable so as to vary the tension on the con-
tinuous track. The details of the Holt caterpillar, the Best
tracklayer, and the Yuba ball-tread machines of this type are
shown in Figs. 85, 86, and 87, which make the principles of
operation so clear that further explanation is unnecessary.

Only a brief mention has been made of a few of the differ-
ent types of transmissions and final drives employed on tractors,
there being so many that it would be out of the question to
attempt to describe all of them, particularly since not a few
have numerous special features. The foregoing examples, how-
ever, cover the principles employed in practically all tractor
transmissions and suffice to make clear the manner in which
these principles are applied.

TRACTOR OPERATION

GENERAL INSTRUCTIONS

Tractors Different in Design but Alike in Care Required. In

the foregoing pages an attempt has been made to outline briefly
the principles of tractor operation with just sufficient references
to actual types to make the text clear. At the present stage of
development it is hardjy possible to select any one manufacturer's
product as typical of tractor design in general or as embodying
throughout those features of design which are most likely to become
standardized during the next five years of development. There are
so many different makes on the market and frequently so many
models of each make that it would require a volume larger than the
present one merely to give a brief description of all of them. Con-
sequently, no extended descriptions of any tractors are given here.
While designs and details of construction differ so widely
and so frequently, all oil or gas engine tractors are based on
certain underlying principles and all call for the same kind of
care. The remainder of this article is accordingly devoted to
an outline of the methods of handling tractors in service with a

126 GASOLINE TRACTORS

view to pointing out clearly just the kind of care the machine
needs to keep it running efficiently. To facilitate reference, this
information is put in the form of questions and answers grouped
under the particular subjects which they cover.

Degree of Care Necessary. Before taking up the detailed
consideration of tractor operation it is well to revert for a moment
to the comparison between the automobile and the tractor in
order to emphasize the great difference in the conditions of oper-
ation of the two. It is a great mistake for the owner or operator
of a tractor to conclude that because he can keep his car running
for weeks at a time and subject it to the severest kind of service
without being called upon to give it more than passing atten-
tion at infrequent intervals, the same amount of care will suffice
to keep the tractor running equally well. The most severe
service to which an automobile can be subjected is trifling com-
pared to what a tractor must undergo in plowing ten hours a
day. No comparison between the two is possible. The atten-
tion demanded in running a tractor is really only comparable to
that required by a marine engine which is run steadily at full
power.

It is naturally impracticable to employ more than one man
to run the average tractor so that the single operator must
assume the combined tasks of the oiler, engine-room attendant,
and engineer on watch in the engine room of a steamer. He
must see that every part is constantly lubricated, must watch
all moving parts in sight from time to time and keep all his
senses on the alert all the time to detect the first indications of
overheating or faulty operation as evidenced by the sounds
produced.

Parts Giving Most Trouble. Over two thousand tractor
owners sent in reports in answer to a questionnaire forwarded to
them by the Department of Agriculture. In answer to the ques-
tion "What part of your tractor gives you most trouble?" more
than seven hundred mentioned some part of the motor and of
that number considerably over one-half gave the ignition as the
chief source of delay. A leading tractor manufacturer substan-
tiates this by stating in his instruction book that the motor is
responsible for fully 75 per cent of all tractor troubles and that

GASOLINE TRACTORS 127

70 per cent of the motor trouble is due to the ignition. A
resume of the answers sent in to the questionnaire follows:

Magnetos 299 Cylinders and pistons 61

Sparkplugs 110 Clutch 59

Gears 108 Valves and springs 43

Carburetor 104 Lubrication 29

Bearings 80 Starting 28

The figures given in each case represent the number of tractor
owners who gave the part in question as the chief cause of their
troubles in operation. These figures do not, however, give any
idea of the relative importance of the parts as sources of trouble.
Failure of the magneto, or even of a spark plug, brings the
tractor to a halt, but the trouble may usually be remedied in a
very short time and no damage is caused, whereas a breakdown
due to faulty lubrication, or to the failure of the cooling system,
which is not mentioned at all, will usually involve the loss of
anywhere from a day to a week besides a heavy repair bill.

Supply of Spares Necessary. The cost of an ample supply
of spare parts is small compared with the time that is saved
when the part most needed is right at hand and can be installed
without delay, so that a number of spares of the most necessary
parts should be considered part of the investment and be bought
at the same time as the machine. Unless it be an ocean-going
steamer, there is hardly another piece of machinery that per-
forms such strenuous service so far from a repair and supply
base as does the tractor. It would be just as foolish for the
chief engineer of a steamer to leave port without any spare
parts in the storeroom and still expect to arrive at his destina-
tion, regardless of what happened, as it is for a farmer to pur-
chase a tractor and expect to get through his first, second, or
any other season of plowing or threshing without vexatious delays
unless he has on hand spares of the parts most frequently needed.

Manufacturer's Service Poor. While it would not be just to
generalize by saying that the service rendered the purchaser by
every manufacturer of tractors is poor, this is true in many cases
and must always remain so for the farmer who is located miles
from the nearest dealer representing tbe factory. It is nothing
unusual to waste from half a day to a day, telephoning and

128 (JASOLIXK TRACTORS

waiting for a part to be sent out or driving in for it. The
dealer may be off for the day in some other part of the county,
making a demonstration or closing a sale, and there may be no
one in his place of business to render the desired service. Mean-
while, the machine is standing idle. There are few replacements
that the experienced driver of a tractor cannot make without
other assistance than that provided by the usual farm shop, so
that if the parts are on hand little time will be lost in getting
the machine under way again.

Parts Needed. While the make of the tractor in question
will determine the character of many of the spares that should
be carried by its owner, there are some that are needed with all
makes. These are valves, valve springs, and small parts needed
in connection with the valves, igniters, or make-and-break plugs
for low-tension ignition systems, also ignitor trip rods, or rather
the small parts which compose the fittings of the rod rather than
the rod itself, since the latter is not subjected to wear. Spare
connecting cables cut to length and fitted with terminals, whether
for high- or low-tension systems, will often be found valuable.
Extra fan belts and spark plugs should hardly be called spare
parts in this connection since they are absolute necessities at
comparatively short intervals. Hose connections between the
motor and the radiator are also in the same class. Where a
motor is equipped with die-cast main bearings or connecting-rod
bearings, a spare set will often prove to be worth many times
its cost in the saving of plowing or threshing time, since even
well-attended machines do suffer breakdowns from burnt-out bear-
ings at times. Extra piston rings as well as an extra piston
and a connecting rod are likely to be called for sooner or later.
The magneto is a pretty expensive piece of equipment and, more-
over, it is usually so reliable that it will continue to work season
after season without giving any trouble. But when it does break
down, it is sometimes beyond the ability of the tractor operator
to make the repair. WThere two or more tractors are operated on
a farm and the same magneto is standard on all of them, it
would pay to invest in a spaiv, though at any time but the
height of the season the laying up of one tractor would probably
not Oanse anv trouble.

GASOLINE TRACTORS 129

The foregoing discussion has been confined to enumerating
motor parts or accessories that should be carried as spares since
they are common to practically all motors. So far as the rest
of the machine is concerned, the owner must either learn from
experience what parts are likely to wear out rapidly and need
replacement at short intervals, or he must depend upon the
manufacturer's representative to give him this information.
Naturally, the maker and his salesmen do not wish to give the
impression that any of the machine's parts will need replacement
in a short time, and in a good many instances they are as much
in the dark as the purchaser is, since it may be that the model
has just been placed on the market and there has been no oppor-
tunity to learn its weak points in actual service.

Both the time spent in getting information of this kind and
the money invested in the necessary spare parts will return very
substantial dividends when the occasion arises to use the parts.
There are some parts that may never be used, such as a steering
knuckle. Get the manufacturer's representative to give you a
frank opinion. Point out your position, when isolated, and do
not content yourself with his first recommendations. Insist on
finding out what are the weak parts of every important unit.
The factory man has a good line on this by the extent of the
demand for certain replacement parts. It will usually be found a
paying investment to purchase a stock of almost all of them
rather than take chances on getting the particular part most
needed at a time when the tractor is worth a good many dollars
an hour to you.

LUBRICATION
MOTOR LUBRICATION

Q. What grade of lubricating oil should be used for a slow=
speed tractor motor; for a high=speed type?

A. Every responsible tractor manufacturer goes to consider-
able expense to determine just what grade of lubricating oil is
best adapted to his own engines. His investigation covers every-
thing from a chemical analysis and flash test of every grade of
oil recommended for his use to actual tests in service extending
over considerable periods of time. The tractor owner should

CASOLIM: TRACTORS

Accordingly never use anything l>nt llie oil recommended by the
manufacturer.

Q. In a motor having any form of splash lubrication, that
is, one in which part of the supply is carried in the crankcase
pan, how often should the oil be drained from the crankcase?

A. The recommendations of different tractor manufacturers
range all the way from every day to once in two weeks, many
giving one week as the maximum period of time the same oil
should be used.

Q. How often should the oil in a circulating system be
completely replaced with a fresh supply?

A. It should he repla.ee* 1 at the intervals given above for a, splash
system since the service demanded of the lubricant is the same.

Q. Does oil lose its lubricating qualities through use, and
how can this be determined?

A. High temperature and pressure completely change the
character of lubricating oil and destroy its lubricating qualities.
The lubricating quality of an oil depends upon its viscosity, that
is, its body, upon which depends its ability to hold apart surfaces
under pressure by a film of lubricant. Dip the finger ends in
some old oil from the crankcase and rub together under pressure.
The oil will have a thin watery feeling and the finger tips may
be pressed into close contact through it. Try the same experi-
ment with some fresh oil, and it will be noted that a sliding
film is formed between the fingers despite the greatest pressure
that can be put upon them to squec/e it out.

Q. What influence has the effect of high temperature and
pressure on the length of time during which the oil should be
allowed to remain in the crankcase?

A. Both the temperature and the pressure conditions differ
\\idely in different engines so that in some the oil literally nrarx
tmf much faster than in others and should accordingly be replaced
oftener. The tractor manufacturer has learned from experience
the proper period of time for his motors, and his recommenda-
tion is based on a. desire to avoid having his customer pay for
the same experience.

Q. Next to labor and fuel, lubricating oil is the most
expensive item of tractor maintenance. Is it really economy to

GASOLINE TRACTORS 131

replace what appears to be good oil as often as the tractor
manufacturer recommends it?

A. The cost of repairs due to a single breakdown from
failure of the lubrication would usually buy anywhere from one
to five or more 50-gallon barrels of oil, without taking into
account the loss of time due to the tractor being out of service.
It is the highest form of economy to follow the maker's instruc-
tions in this respect; if these are to discard the oil at the end
of every day's service, it will be found far cheaper in the end to
do so. Many tractor owners do not regard it as necessary to
clean out the crankcase more than once or twice a season, but
instead of saving oil they are simply running up repair bills.

Q. What other causes tend to destroy the lubricating quality
of the oil?

A. Another cause is leakage of the fuel past the pistons so
that the supply of oil in the crankcase is thinned out by the
gasoline or kerosene. This is particularly true of kerosene, espe-
cially if the motor be run at a low temperature so that the kero-
sene vapor condenses into a liquid. The admixture of carbon and
dirt with the oil also tends to destroy its lubricating quality.
Compare the color of oil that has been used for some time with
fresh oil; the difference is due entirely to the foreign matter that
has become mixed with it.

Q. What attention does a force=feed lubricator require?

A. The sight feeds should be watched frequently to note
whether oil is constantly passing through them or not. To make
certain of this, dirt should be wiped from the glasses at least
once a day. While this type of lubrication has the great advan-
tage of constantly feeding fresh oil to the bearings almost as fast
as it is consumed, its factor of safety is not so high as that of
the splash or circulating type. In other words, failure of the
part is apt to follow immediately upon a stopping of the feed
since it usually receives no lubrication from any other source.
The lubricator must accordingly be watched closely and the
engine stopped at once if any of the feeds has become clogged.

Q. How often should such a lubricator be supplied with fresh oil?

A. The maker's instructions may be followed but a still
better practice is to get into the habit of keeping the lubricator

(1ASOLINK TRACTORS

constantly filled; that is, of filling it twice or oftener a day, if
necessary, rather than waiting until the supply runs low. A
gage glass on the side of the lubricator shows the amount in it.
The plunder pumps which force the oil to the bearings will
always work better when there is an ample supply.

Q. What other precautions should be taken with a force=
feed lubricator?

A. When it is driven by a belt, close watch should be kept
on the belt to see that it does not become too loose, since any
slackening of the belt slows down the pumps and supplies less
oil to the bearings.

Q. How often should a force=feed lubricator be cleaned out?

A. Two or three times a season should ordinarily be ample,
but this will depend to some extent upon the care that is exer-
cised in handling the supply of oil itself. Unless the oil supply
is kept in a covered oil tank, more or less dust and other foreign
matter is bound to find its way into it. The presence of dirt
in the oil will make itself apparent by clouding the inside of the
sight-feed glasses, making them difficult to read. Oil having
visible foreign matter, such as small specks of grit, short ends of
straw, or chaff, in it should never be put into the lubricator
without straining, as it is liable to clog the pump valves.

Q. How is a force=feed lubricator cleaned out?

A. By disconnecting the leads and flushing it out thoroughly
\vith gasoline or kerosene. The leads should be disconnected at
both ends and also flushed out, blowing through them to see
that they are clear from end to end.

Q. Are some of these leads more apt to clog up than others?

A. Those that supply oil to the pistons are most likely to
clog owing to an accumulation of carbon in the ends opening
into the cylinder. They should be taken off at shorter intervals
and all carbon removed in the tube itself as well as in the open-
ing through which the oil passes through the cylinder wall.

Q. What attention does a circulating system require?

A. A circulating system requires replenishing of the entire
supply after washing out at intervals, as directed in the manu-
facturer's instructions; examination at short intervals of the oil
pump; and l'iv<|iiriit washing oil' of the oil pump screen. Keep

GASOLINE TRACTORS 133

the sight-feed glasses clean and shut down immediately if an oil
stream fails to appear in any of them (some tractors have but
one, others several).

Q. What general precautions should be observed in clean=
ing out a lubricating system of any type and in handling oil?

A. Always avoid the use of waste or rags from which lint
will detach itself in wiping out the crankcase or any part of the
system, since these threads will invariably clog an oil pump or
feeder tubes. All cans or other vessels used in handling oil should
be kept covered to prevent dust falling in them and should be
wiped clean before using. Dust is simply fine grit, and its pres-
ence in the oil converts it into a grinding compound which will
quickly cut away bearing surfaces.

Q. What other lubrication does the motor require?

A. This will depend entirely on the type of motor. Where
it has overhead valves as used on many tractor motors, the rocker
arm spindles and pin should be oiled at least once or twice a
day with a hand oiler. This applies as well to any other external
moving parts not lubricated by the oiling system of the motor.
The grease cups on the fan and on the pump should be turned
down at least once a day. Some tractors are equipped with
gravity oilers for this purpose.

CONTROL SYSTEM LUBRICATION

Q. How is the clutch lubricated?

A. On some tractors it is enclosed in the same housing as
the motor and runs in a bath of oil. Where it is not housed in,
grease cups are usually provided on the clutch, and these should
be turned down at least once a day. Xo oil should be allowed
to fall on the facing, as this would reduce the holding power, of
the clutch and cause it to slip.

Q. What attention is required to keep the transmission
properly lubricated?

A. When the transmission is of the enclosed type, running
in oil, it should be kept filled to the height given in the maker's
instructions and with the grade of lubricant recommended. Don't
attempt to use cup grease, or a home-made compound of grease
and oil or graphite, as the different materials will separate, nor

134 GASOLINE TRACTORS

should heavy steam cylinder oil be used, since it contains animal
fats and will become acid, attacking the steel faces of the gears.
The pressure between the gear teeth in a transmission is very
high so that the oil wears out in time and should be replaced at
intervals of two to three months. Watch the transmission hous-
ing for leaks and renew felt washers or other provision for pre-
venting leaks.

Q. How are open transmission gears lubricated?

A. Where gears are run without a housing, they are not
intended to be lubricated and care should be taken to see that
no oil or grease* gets on them as it will hold dirt and grit and
cause the teeth to wear out much faster. The gears should be
kept free of mud and dirt, but an oily rag or waste should never
be used for this purpose. This also applies to the bull pinion
and gear except where completely housed in.

Q. What attention is required to lubricate other moving
parts of the tractor?

A. Grease cups are usually provided on all other moving
parts, and they should be turned down as instructed by the
maker. In some instances the directions are to screw these cups
down as often as twice a day; in others, once an hour.

ENGINE PARTS
ENGINE BEARINGS

Q. How long will motor bearings run without developing
sufficient play to require adjustment?

A. This will depend largely upon the motor itself and the
service demanded of the tractor. If it is being run constantly
with an overload, they will need attention much sooner than
when the machine is not called upon to carry more than 75 per
cent of its load for the greater part of the time. In any case
the bearings should be examined at least once a week; some
makers recommend that they be tested for looseness as often as
twice a week when in constant service.

Q* How can the bearings be tested for looseness?

A. They should always be examined just after the motor
has been shut down and is still hot; the amount of play will be

GASOLINE TRACTORS 135

greater when all the parts are cold but some of this will be taken
up by the thickened oil film then present and their condition
cannot be determined as satisfactorily. The connecting-rod bear-
ings are the first to show signs of looseness. Take the handhole
covers off the crankcase and turn the motor until two of the
connecting-rod ends are close to the openings. If there is much
play, it will be evident upon grasping the connecting rod and
attempting to lift it, but this amount would usually cause a
knock in operation. Take a small bar and pry the bearing
upward from below, keeping the other hand on the rod to detect
any movement. Do not confuse the side play of the bearing
with looseness of the bearing itself as a small amount of side
movement is allowed on all connecting-rod bearings. Apply this
test to the other two connecting rods also. A bar may also be
used to detect any looseness of the main or crankshaft bearings.

Q. Will it do any harm to allow a certain amount of play
in these bearings?

A. Nothing will be apt to run up a big repair bill quicker
than running the motor with the bearings too loose. Every
reversal of movement pounds the crankshaft and in time will
cause crystallization of the steel with consequent breakage of the
shaft. The resulting vibration is also detrimental to every other
part of the motor.

Q. How are the bearings adjusted when a test reveals
play in them?

A. Most motor bearings are provided with shims, that is,
small strips of metal placed between the halves of the bearing
and through which the bolts pass to hold the bearing together.
Take off one or more shims on each side of the bearing and
screw down the nuts again tightly. To obtain a proper adjust-
ment, you must be able to set up these nuts as far as they will
go without binding the shaft. Open the pet cocks or the com-
pression release, where one is provided on the engine, and try
the adjustment by cranking the motor by hand. It will be very
difficult to turn the motor over if the bearings are too tight.
They should be adjusted so that the motor turns easily, indi-
cating that there is sufficient space between the bearing halves
and the shaft to permit the formation of an oil film between

130 (1ASOUNK TRACTORS

them. The shaft should be tested for play, as already described,
to prevent making the adjustment too loose.

Q. When a bearing is too tight, is it good practice to ease
off the nuts and let the shaft run that way?

A. A bearing is not properly adjusted unless the nuts can
be set up hard on the bearing caps, all adjustments being made
by removing or re-inserting shims, or laminations of metal only a
few thousandths of an inch thick. One or two shims should be
removed from each side at a time and the adjustment tested.
Care must always be taken to see that the bearing cap is replaced
on the bearing from which it was taken and that it is put back-
in ihe same way.

Q. Is it ever necessary to adjust the piston=pin, or wrist=
pin, bearing?

A. This is the bearing which holds the upper end of the
connecting rod in the piston and if the motor is properly lubri-
cated with clean oil, it will seldom require any attention. In
some motors the pin is held fast in the sides of the piston and
the connecting rod moves on it, and shims are provided on the
connecting-rod bearing for adjustment. In others the upper end
of the connecting rod is clamped fast to the pin, and the pin
moves in bronze bushings in the sides of the piston or bears
directly on the piston walls. Allowing the big-end connecting-
rod bearings and the crankshaft bearings to become too loose so
that the motor knocks is the chief cause of lost motion in the
wrist-pin bearing. Where the pin bears in the piston walls this
may wear the holes out of round so that they have to be rebored
and bushed to make a good bearing.

Q. When the connecting rod or crankshaft bearings of a
motor require adjustment at frequent intervals, what is the cause
of the trouble?

A. The cause is faulty lubrication: failure to clean out the
crankcase at the proper intervals, with the result that the oil
loses its lubricating qualities and the dirt that becomes mixed
with it cuts away the bearing surfaces.

Q. Where bearings have become worn to the point where it is
no longer possible to adjust them properly, is it practical for the
average operator of a tractor to replace them with new bearings?

GASOLINE TRACTORS 137

A. It is not practical unless he has had experience in the
work, since it requires accurate lining up and scraping in of the
bearings to a close fit. Unless this is carried out properly, such
heavy stresses will be imposed on the crankshaft that it will
break sooner or later. Therefore it is poor economy to attempt
this repair without actually having had experience in making it;
it is one of those ; things that cannot be learned from an instruc-
tion book. It is necessary to see it clone in the shop more than
once and the first attempt should be made under the supervision
of one who has had experience.

VALVES

Q. What attention is required to keep the valves in good
operating condition?

A. The valve stems must be lubricated one or more times
a day, except on motors provided with special means for doing
this automatically. The clearance between the valve tappet and
push rod, or between the end of the rocker arm and the valve
stem, depending upon the type of motor, must be adjusted at
frequent intervals and the valves themselves must be ground as
often as is necessary to keep them tight.

Q. Why is adjustment of the clearance necessary, and
what should this be?

A. The constant hammering of the tappet or rocker arm
against the valve stem tends to increase this clearance as well as
to wear away the parts, thus increasing the distance. The greater
this distance is the less the valve will lift when operated, so that
less fuel is admitted on the intake stroke and some of the exhaust
gases are left in the cylinder on the exhaust stroke, thus cutting
down the power. This clearance should be just sufficient to
allow the valve to close completely under the pull of its spring
when the tappet or rocker arm is released by the cam. It should
be tested and adjusted with the motor hot, since, if made very
close when cold, the expansion of the parts is apt to prevent
the valve from closing properly. An ordinary visiting card or a
piece of tin plate makes a good gage; it should be possible to
slip this between the tappet and stem easily. In any case the
clearance should not exceed ^V inch.

138 GASOLINE TRACTORS

Q. How often should the valves be ground?

A. When a tractor is being used ten hours a day and six
days a week, they will doubtless require grinding once every four
to six weeks, depending more or less on the motor itself; some
motors run very much hotter than others and in some the pro-
vision for cooling the exhaust valve is inadequate, so that more
frequent attention is necessary.

Q. How may the valves be tested for leakage without
taking the motor down?

A. Turn the motor over by hand about one-third of a revo-
lution, until two of the pistons are within an inch or two of the
upper dead center. At this point the pressure in the cylinder
that is then on the compression stroke should be highest. Hold
the piston up against this pressure, just exerting sufficient pull
to cause the piston to move if the compression leaks away. In
a motor that is in good condition, there should be no perceptible
movement due to leakage in the course of two or three minutes,
and if the pull of the hand is slackened, the piston should tend
to push the starting crank down again under the influence of
the pressure in the cylinder. Apply the test to each cylinder in
turn and any difference in the compression-holding power of the
different cylinders will be noticeable.

Q. When the usual adjustment of the clearance does not
correct a loose and noisy valve action, what is apt to be the
cause of the trouble?

A. The pin of the cam roller has probably worn so that
there is considerable lost motion between the roller and the pin
on which it turns. The only remedy is to replace the roller
and pin or maybe the tappet complete. Any lost motion at
this point permits the roller to move upward the distance repre-
sented by the wear before the tappet itself can lift. While the
play at any one point may be very small, when it is increased
by an equivalent amount at two or three other points, the total
is sufficient to reduce the effective valve opening considerably,
with a corresponding decrease in the power. When new parts
are not readily obtainable, this condition may be remedied by
boring out the holes of the cam roller and the rocker lever and
fitting them with bushings.

GASOLINE TRACTORS 139

Q. When grinding valves, is it necessary to continue the
operation until the entire valve and seat have taken on a polish?

A. No; the operation may be considered complete when
both the valve and the seat are smooth all around and com-
pletely free from any sign of pitting. A polished surface may
give a little closer fit, but the difference is not enough to com-
pensate for the time necessary to produce it. The grinding
operation should always be finished by the use of the fine grind-
ing compound.

Q. In case a motor has been allowed to run until the valve
seats have become very badly pitted, is it necessary to cut these
down by grinding alone?

A. No; a valve-seat reaming tool should be employed for
cutting away the metal until the pitting has almost disappeared,
and the remainder of the operation should then be carried out
by grinding in the usual manner. No more metal than necessary
should be removed with the reamer as cutting too deep will
simply shorten the life of the cylinder casting. Valves are made
in two standard tapers, 45 degrees and 60 degrees, and care
must be taken to see that the angle of the reamer blades corre-
sponds to that of the valve seat before beginning to cut.

Q. Is there any way of testing the tightness of the valves
before putting them back into the motor?

A. When the valves are in cages, they may be tested by
pouring some gasoline into the cage and noting whether it leaks
past the valve or not.

Q. Does a rapid loss of compression under such a test
always definitely indicate that the valves are at fault?

A. No; the piston rings may be worn or the lubrication
may be *poor, so that there is not a good compression seal in
the cylinder. To definitely ascertain the trouble, take out the
spark plugs and pour an ounce or two of heavy cylinder oil into
each cylinder. Turn the motor over fifteen to twenty times
with the plugs out to work this oil down on the pistons, replace
the spark plugs and repeat the test as first described. Failure
to hold compression will then mean poorly seating valves almost
invariably, since, with a fresh oil seal, even loose piston rings
will hold compression when the motor is being turned over by

110 (iASOLiXK TRACTORS

liaiul. The necessity For putting in lliis oil indicates that the
oil in the crankcase or the circulating system needs renewing.
This test for loss of compression should be carried out with the
motor cold.

Q. What is the best method of grinding the valves?

A. With a valve-in-head type of motor, take the valve
cages over to the bench so that there is no risk of getting any of
the grinding compound into the cylinders. Use nothing but the
specially prepared grinding compound designed for this purpose;
ordinary emery and oil should never be employed as it will score
the valve and its seat. When a special valve grinder is not at
hand, a screw driver bit in an ordinary brace makes the best
grinding tool. Smear some of the compound on the valve, drop it
on its seat and turn it first one way and then the other, making
about a quarter turn in each direction without exerting much
pressure. When the compound has been squeezed out, put in
more and continue the operation, repeating this for fifteen to
twenty minutes. Wash the valve and seat off with kerosene and
examine to see if all signs of pitting have been removed and the
valve has a bright uniform band around its entire circumference.
The presence of any breaks in this ring indicates low spots and
calls for further grinding. Never turn the valve completely
around when grinding, making only a quarter turn, since the com-
plete turn will score the seat. Be careful to flush off every trace
of the grinding compound with kerosene when through to pit* vent
any trace of it getting into the cylinder. Otherwise, the engine
will be ruined. Where the valves cannot be taken away from the
motor for grinding, the greatest care must be exercised to prevent
any of the compound from getting into the cylinders or down into
the valve guides.

Q. Why is it necessary to grind the valves at such short
intervals?

A. The exhaust valves in particular are subjected to exceed-
ingly high temperatures that pit the metal Face of the valve.
Once this pitting starts, it proceeds rapidly and if the valves are
allowed to run too long without grinding, these pits in the valve
face will be so deep that new valves will be necessary. They will
also be deep in the valve seat with the result that a correspond-

GASOLINE TRACTORS 141

ingly longer time is required to grind them out. By grinding at
the proper intervals, only fifteen to twenty minutes will be
required for each valve, whereas if they are allowed to run too
long, it may take an hour or more to get each valve and its seat
into proper condition again. The motor will also run very much
better and deliver more power if the valves are kept in good con-
dition.

Q. What is the cause of a valve leaking very badly at
times?

A. Hard particles of carbon from the cylinder may lodge in
the pitted face of the seat or valve and prevent if from closing
tightly. Even though the valve be held off its seat only a few
thousandths of an inch, it cannot hold any compression.

Q. What is the cause of a valve binding so that it will not
operate?

A. Worn valve guides will sometimes permit sufficient side
play to cause the valve stem to become bent. Lack of lubrication
and an accumulation of dirt and carbon in the valve guide- will
cause the valve stem to expand to a point where it binds hard
and fast in the guide.

Q. What causes a valve head to warp so that the valve
must be replaced?

A. It may be caused by overheating of the motor due to
partial failure of the cooling system, such as may be caused by a
slipping fan belt, trouble with the circulating pump, shortage of
water in the system, or the clogging of some of the pipes or the
radiator. An accumulation of sediment or scale in the jackets or
the radiator may have the same effect.

Q. Do valve springs ever need replacement?

A. In the course of a season's use, the temper may be
drawn sufficiently to make the valve action sluggish, particularly
in a motor that runs very hot, but ordinarily the valve springs do
not often need replacement.

Q. Is it ever necessary to check the valve timing of the
engine?

A. It is never necessary except in reassembling the engine
after it has been taken down. Since the camshafts are made with
the earns integral, no relative movement of the cams is possible

142 GASOLINE TRACTORS

and it is only necessary to time one cylinder. Most engines have
reference points by which the valve timing may be checked when
reassembling the engine.

PISTONS

Q. What attention do the pistons require?

A. The piston rings will wear to such a degree that the
pistons no longer hold the compression and there is a substantial
falling off in the power.

Q. How often should it be necessary to replace the piston rings?

A. This will depend entirely upon the care that is taken to
keep dirt out of the lubricating oil and to prevent its entrance to
the motor through the carburetor. If the oil is handled carelessly,
containers being allowed to stand uncovered and a film of dust
settling on them, or if the carburetor is not provided with an air
cleaner, a great deal of grit will find its way into the motor and
will grind the piston rings down rapidly and also the bearings.

Q. How may the pistons be tested for tightness?

A. The valves being in good condition, preferably recently
ground, the test may be made as previously described for testing
the valves; or, with the handhole plates off the crankcase, have an
assistant turn the motor over slowly and note whether there is any
sound of air blowing down past the pistons into the crankcase.
Put a few ounces of fresh oil into each cylinder through the spark
plug openings, replace the plugs, and repeat the test. Loss of
compression may be due entirely to poor lubrication. Drain the
crankcase, wash out with kerosene, and replenish the oil supply;
and test in the same manner.

Q. Is wear of the piston rings the only cause for loss of
compression, aside from pitted valves?

A. An accumulation of carbon under the piston rings may
be holding the piston ring joints apart or the latter may have all
worked into line so that the pressure is escaping through them.
If, with good tight valves, there is still a loss of compression after
putting fresh oil into the cylinders, it is an indication that the
piston rings need attention.

Q. Does the compression fail in all the cylinders equally, or
is one of the cylinders likely to be worse than the rest?

GASOLINE TRACTORS 143

A. The wear is likely to be uneven, so that one or two of
the cylinders will be found very much worse than the rest. Some-
times only one cylinder will fail to hold compression. Test in the
same manner as described for the valves, pulling the crank up
very slowly to note the resistance offered by each piston in turn
as it comes up on the compression stroke. It may be found much
easier to move one of the pistons than the others. When this is
the case, it will be necessary to fit new rings on that piston.

Q. How are new piston rings fitted?

A. Oversize piston rings are supplied for this purpose.
They are slightly larger (a few thousandths of an inch) than those
originally supplied with the motor in order to compensate for the
wear of the cylinder. Take the old rings off by inserting thin
strips of steel (old table-knife blades or discarded hack saws are
excellent for the purpose) at three or four points around the piston
and under the ring. Scrape and wash out all carbon and gummed
oil in the slots. Do not use a file for this purpose. First try the
new rings by fitting them in the cylinder, which operation will
show how much will have to be taken off to allow them to enter
the bore. They must be small enough to insert an inch or two
into the cylinder, since it is turned somewhat larger for a short
distance at the end. If the rings are too large, take a few cuts
with a fine file across the faces of the joint, being careful to keep
the surfaces square and parallel. Very little must be taken off
each time and the ring tried in the cylinder again. The job must
be carried out with painstaking care as unless it is properly done
the new rings will be no better than the old ones. When they
have been properly fitted, use the same strips to place them on
the piston, care being taken not to spring the rings out of round
in putting them on.

Q. When fitting rings in the cylinder as a preliminary to
putting them on the piston, should the break come together for a
good fit?

A. No; allowance must be made for the lengthwise expan-
sion of the ring due to the high temperature, and this allowance
must be greater for the top ring than for the lower ones as it
becomes hotter. Depending upon the diameter of the cylinder,
it is customary to allow yf fa to T%fa inch between the ends of the

144 (iASOLINM TRACTORS

topmost ring and re^ to T^¥¥ inch for the other two. Bearing
shims are often stamped with the thickness in thousandths of an
inch and may be used as a gage. Unless this allowance is made,
the expansion of the ring will cause it to bind against the cylinder
wall and may cause scoring.

Q. Must the piston ring be a tight fit in the piston slot?

A. Allowance for expansion must also be made here. After
scraping the piston slots free of carbon and washing them out
with kerosene so that they are perfectly clean, insert the ring and
see that it turns freely in the slot. A piece of coated catalog
paper lias a thickness of nroo to rcfo^ inch and it should be possi-
ble to insert a piece of this paper between the ring and the slot.
If the rings are too tight they will bind on the piston and cause
damage as mentioned above. Unless they can be moved freely in
the slots, they will have to be made smaller by taking metal off
the bottom edge of the ring. Smear some valve grinding com-
pound on a flat metal plate or a smooth piece of hardwood plank
and rotate the ring in this under pressure with the hand. Be sure
to wash off all traces of the grinding compound before trying on
the piston again.

Q. Do the pistons themselves ever have to be replaced?

A. The same condition that causes rapid wear of the piston
rings, that is, dirt in the lubricating oil, will also cause equally
rapid wear of the pistons. When this wear amounts to jito" to
ylno" inch, the piston will rock on the piston pin in the cylinder
and produce a distinctive noise, known as piston .v/r//>, which can-
not l>e traced to any other cause. At first, it is likely to be attrib-
uted to a loose bearing, and as it increases it will greatly resemble
a bearing knock. When one piston reaches this stage, it is better
to replace all of them with oversize pistons. The cylinders should
be examined carefully for scoring and tested to see if they have
worn out of round as it may be necessary to rebore them or to
replace the cylinder casting to make a good job of it.

Q. Can the pistons be tested for looseness without taking
the motor down when a knock cannot be traced to any other
cause?

A. The amount of wear that will cause considerable piston
slapping is so small that it would b? difficult to detect it without

GASOLINE TRACTORS 145

having the cylinder and piston on a bench where the fit can be
examined closely. The average driver would never attribute the
loud knocking caused by a loose piston to the apparently slight
amount of play that is revealed when the piston is examined.

Q. What causes besides dirt in the lubricating oil will
bring about rapid wear of the pistons or scoring of the cylinders?

A. Other causes are the use of a poor grade of oil, using the
same oil too long, or any other condition that results in inefficient
lubrication, such as overheating due to partial failure of the cooling
system. Unless there is a good oil film between the piston and
the cylinder, the metal comes into actual contact and scoring fol-
lows. Too thin an oil will be burned away by the heat of the
explosion as fast as the film is formed on the cylinder, while too
heavy an oil may not reach the upper end of the cylinder bore
owing to failure to pass the piston rings. Worn piston rings will
permit particles of carbon from the combustion chamber to work
between the piston and the cylinder wall. Partial failure of the
lubrication system, such as the clogging of an oil lead in a force-
feed system, the clogging of the screen or of the pump in a circu-
lating system, or an insufficient supply of oil in a splash system,
will result in scoring.

Cylinder scoring may be due to the piston ring binding
owing to failure to allow for expansion in fitting or to the piston
sticking owing to an accumulation of carbon under it. The wrist
pin may become loose and move endways so that it scrapes against
the cylinder wall; or in assembling the piston and connecting rod,
the wrist pin may be so placed that it presses the piston unevenly
against one side of the cylinder. Carelessness in valve grinding
that results in some of the compound getting into the cylinder will
cause serious scoring sooner than almost anything else.

CARBURETOR

Q. What attention does the carburetor need?

A. It should be drained at frequent intervals to remove the
accumulation of sediment. Care should be taken to prevent dirt
from getting into the fuel, and the latter should be strained as it is
poured into the tank. In making needle-valve adjustments, the
needle must never be screwed down hard on its .seat, since this is

146 GASOLINE TRACTORS

likely to turn a shoulder on it so that proper adjustments cannot
be made with it.

Q. When the carburetor floods, what is the usual cause of
the trouble?

A. The usual cause is dirt lodging under the needle valve in
the float chamber. Where a hollow copper float is used, it may
have sprung a leak, causing it to skik.

Q. How should the carburetor be adjusted to give the maxi=
mum power with the most economical fuel consumption?

A. Definite instructions covering every make of carburetor
cannot be given, but the same principles can be applied to all.
With the motor running, cut down the fuel supply gradually until
the motor begins to run irregularly or to miss. The fuel mixture
is thus made leaner, and in some cases the motor will back fire
through the carburetor when the mixture becomes too lean.
When the point of adjustment has been found at which the motor
is not getting sufficient fuel, turn back slightly until just enough
fuel is being supplied to permit it to idle regularly. This is
termed the low-speed adjustment and some carburetors have no
other, that is, only the fuel supply can be regulated. Others have
a high-speed adjustment as well; this controls the air supply and
takes the form of an adjustable auxiliary air valve. Speed the
motor up and release the tension of the auxiliary air valve spring
until the point is reached where too much air is being admitted
and the mixture again becomes too lean. Then turn back slowly
until as much air is being admitted as is possible without causing
irregular operation.

Q. Does the working of any other part of the motor influ-
ence the carburetor adjustment?

A. Unless all other parts of the motor are in good working
condition, it will be found impossible to make a satisfactory car-
buretor adjustment. Valves in need of grinding, excessive clear-
ance between valve tappets and stems or rocker arms, worn piston
rings or pistons, and worn valve guides will all influence the adjust-
ment of the carburetor. Air drawn in through worn valve guides,
a leaky intake manifold, or a leak at the throttle valve of, the
carburetor will weaken the mixture and make it too lean, so that
the motor loses power and overheats. With the motor running,

GASOLINE TRACTORS 147

take a squirt can and put some gasoline on the intake manifold
gaskets and around the valve stems and note whether it is drawn
in or not. New gaskets will remedy trouble of this nature at the
manifold. Whenever the manifold has to be taken down, it is
always better to replace the gaskets, since it is difficult to make
used gaskets tight.

Q. The float valve and needle adjustment being in good
condition, what is the cause of the trouble when a regular flow
of fuel cannot be obtained at the nozzle in the mixing chamber?

A. The supply line may be partially clogged or tjie vent hole
in the top of the carburetor may Be stopped up. This is a small
opening designed to admit air in order that there may be atmos-
pheric pressure on the fuel in the float chamber. If this clogs up,
a partial vacuum is formed. In a gravity system the air vent on
the tank may have become stopped up and the fuel will not flow
to the carburetor owing to the lack of atmospheric pressure on top
of the supply. In a pressure or a vacuum tank supply system the
trouble may be with the pump, or with loose joints, or with the
tank itself.

Q. When difficulty is experienced in making a satisfactory
low=speed adjustment, what is likely to be the cause?

A. The needle valve may have been forced down on its seat
so that a burr or ring has been formed on the needle. The latter
should be taken out and repointed.

Q. Is an air cleaner indispensable in connection with a
tractor carburetor?

A. It will save its cost and the time required to attend to it
many times over. Without it, pistons, rings, and bearings will
grind out very rapidly, and trouble will be experienced with
accumulations of carbon, more than half of which will be nothing
more nor less than dirt drawn in through the carburetor.

Q. What attention does the air cleaner require?

A. Frequent cleaning is the only attention needed. When
the cleaner is of the dry-air type, the engine should always be
shut down before emptying it. If it is a washer type, see that it
is constantly supplied with plenty of water. Clean out either
type twice a day or oftener, if necessary, rather than wait until it
is full. Analyses of carbon accumulations taken from automobile

148 GASOLINE TRACTORS

cylinders have shown them to consist of 65 per cent, or more, of
road dirt.

Q. How can an over=rich mixture be detected?

A. Note the color of the exhaust from the muffler. The
presence of black smoke indicates that too much fuel is being fed;
blue smoke, too much lubricating oil; and. grayish-white smoke,
poor combustion of kerosene usually due to an excess of water.
An over-rich mixture, particularly when kerosene is being used, will
cut the lubricating oil from the cylinder walls and cause scoring
unless remedied.

Q. What is the object of feeding water with the fuel?

A. To assist in keeping the temperature of the engine down
to the proper point for satisfactory working. The steam generated
rapidly absorbs a great deal of the heat and has the further
advantage of preventing the formation of carbon in the cylinders.
It also causes better combustion, particularly in the case of kerosene.

Q. Should water be fed with the fuel regardless of the
grade of oil employed?

A. Little or no water is necessary when using gasoline, but
the majority of motors will not operate satisfactorily on kerosene
without it.

Q. Is there any danger of feeding too much water, par-
ticularly when the motor is running very hot and appears to
need it?

A. Excess water fed with the fuel is liable to lower the
temperature to the point at which kerosene recoridenses to a
liquid; in such a case considerable of it works its way past the
pistons and down into the crankcase. This destroys the film of
lubricant on the cylinder walls and is liable to cause damage, not
alone to the cylinders themselves but likewise to the bearings;
thinning the oil in the crankcase destroys its lubricating qualities.
If the motor appears to be getting too hot, the trouble should be
remedied by locating the fault in the cooling or the lubricating
system and not by attempting to overcome it by increasing the
amount of water fed.

Q. What indication is there of excessive water in the fuel?

A. A grayish white smoke will appear at the exhaust indi-
cating that the kerosene is not being completely burned in the

GASOLINE TRACTORS 149

cylinders. Cut down the water supply very gradually until the
smoke disappears, the motor being kept running at a good speed,
since if run too slowly on kerosene the combustion of the latter
will not be complete owing to the drop in temperature.

Q. Are all tractor motors provided with hand=controlled
apparatus for feeding water?

A. No; some carburetors are designed to feed water auto-
matically as it is needed, while in others- the use of a wet air
cleaner is depended upon to supply the proper amount of water
required.

Q. Where hand control is provided, should the water be
fed as long as the engine is running?

A. It is better to shut it off five minutes or so before the
motor is to be stopped, and the fuel should be switched from kero-
sene to gasoline at the same time, as this will leave the motor in
better condition and facilitate restarting.

Q. What precautions should be taken with the water sup=
plied for this purpose?

A. Clean rain water should be used, and it is well to strain
it through two or three thicknesses of cloth to prevent the entrance
of any dirt.

COOLING SYSTEM

Q. When the engine overheats despite the fact that the
cooling system is working properly, what is the cause of the
trouble?

A. It may be due either to an over-rich or an over-lean
mixture. In either case combustion is slow instead of taking the
form of the explosion required to produce the maximum power.
The mixture continues to burn throughout the stroke and in the
exhaust passages and muffler. Flame issuing from the exhaust is
an indication of this condition. The ignition may be retarded too
far and bring about the same condition.

Q. What are some of the causes of failure of the cooling
system?

A. Among the causes are the following: insufficient water
supply; fan belt slipping; pump running too slow when driven by a
belt; insufficient lubrication; leaks in radiator or at pump packing
permitting water to escape or air to enter; and clogging of radia-

150 GASOLINE TRACTORS

tor, circulating pipes, or water jackets with an accumulation of
sediment. The cooling system should be drained at frequent
intervals and flushed out with clean water. An accumulation of
carbon in the cylinders will also cause the engine to overheat and
if allowed to become very bad, will cause preignition, which
imposes very heavy stresses on all moving parts of the engine.

Q. When hard water has to be used in the cooling system
and scale forms, how can this be removed?

A. A strong soda solution made by adding several pounds of
common washing soda to enough boiling water to fill the system
should be used for a day or so in place of ordinary water. The
system should then be drained and flushed out. The use of rain
water will prevent the formation of scale. Particles of iron rust
in the water when the system is flushed should not be confused
with scale; these will always be found, even if the system is
drained every day.

Q. Do the flexible=hose connections ever cause any trouble?

A. The inner plies of the hose sometimes become detached
owing to the high temperature of the cooling water and either
partially or wholly clog the passage. The passage is liable to
become wholly clogged with the pump type of circulation owing to
the much smaller diameter of the hose used. To guard against
trouble of this nature, use nothing but the hose connections sup-
plied by the manufacturers as replacements since this hose is
specially made to withstand hot water. Ordinary hose will dis-
integrate rapidly when employed for this purpose and should
never be so used except to tide over an emergency, being replaced
with a new connection as soon as possible.

Q. Is partial or total failure of the cooling system the only
cause of overheating?

A. No; there are numerous other causes of overheating.
The motor may be run with the ignition retarded; the lubrication
may not be efficient; or carbon may have accumulated in the
combustion chambers, as pointed out in a previous answer.

Q. How can carbon be prevented from accumulating in the motor?

A. After the motor has been shut down for the day and is
very hot, take out the spark plugs, turn the motor over by hand
until all the pistons are at approximately the same height, and

GASOLINE TRACTORS 151

pour into each cylinder about an ounce of kerosene, letting it
stand this way over night. Do not use more than this amount of
kerosene (a tablespoon will hold about an ounce) on the theory
that if a little does good, more will do better, since more kerosene
will cut the lubricating film off the cylinder walls and thin the oil
in the crankcase.

Q. How can the fan belt be kept in'good condition?

A. Make adjustments only when the motor is hot and do
not put any more tension on the belt than is necessary to prevent
slipping. A belt that is set up too tightly will wear very quickly
besides imposing undue stresses on the pulley bearings. Keep the
leather soft by applying neatsfoot oil from time to time.

Q. How often should the radiator and cooling system be
drained?

A. Two or three times a season are sufficient in summer if
clean rain water is being used and it is strained before being put
into the radiator. In winter it will be found better practice to
drain the entire system every night rather than to depend upon
an anti-freezing solution, since the latter lowers the boiling point
of the water to such an extent that it is likely to boil away. In
any case, if alcohol is used in the anti-freezing solution, it is
likely to boil out of the water, so that the latter cannot be left in
over night with safety. Some tractors are cooled by oil, and in
cold weather it is necessary to thin this oil with kerosene before it
will circulate freely.

Q. When it is discovered that a considerable quantity of
the water has boiled away and the motor is very hot, is it good
practice to fill up with cold water immediately?

A. This should not be done, particularly in winter, as the
fresh supply is likely to be very cold and the sudden contraction
would impose severe stresses on the radiator joints, starting leaks.

Q. What attention does the pump of a circulating system
require?

A. See that the glands are kept tight. The appearance of a
drop of water at the gland indicates the beginning of a slow leak.
Give the gland nut a partial turn to tighten it; if water still
appears, it will be necessary to repack the stuffing box. Use oil-
soaked cotton wick or graphite packing.

152 GASOLINE TRACTORS

HORSEPOWER RATINGS

Q. Why are tractors rated as 10-20, 16-30, etc., always
giving two horsepower ratings?

A. Tractors are designed to be used for belt as well as for
field work. In doing the latter, the tractor must use a substantial
percentage of its power to move itself. The lower rating accord-
ingly expresses the amount of power available for plowing. When
standing, as in performing belt work, the only losses are caused by
whatever transmission gearing is interposed between the engine
and the belt pulley, so that almost the entire output of the power
plant is available for driving other machinery.

Q. What constitutes an overload, and why do all manu=
facturers warn the tractor user so strongly against subjecting
the machine to overloads?

A. Considerable confusion exists as to the meaning of the
term horsepower. For a few minutes, as in pulling out of a hole,
a heavy draft horse is capable of exerting 600 to 800 pounds draw-
bar pull, which is the equivalent of more than 1 hp., but the
same horse cannot exert much more than an average of 100 pounds
drawbar pull at a speed of three miles an hour in hauling a load
all day. The fact that a tractor having a field rating of 16 hp.
may be pulled out of a bad place by three heavy horses does not
indicate that the team is capable of doing as much work as the
machine. The animals can only exert this much power for a very
short period. The tractor will generate an amount of power at
the drawbar equivalent to fourteen or fifteen horses at the usual
plowing speed and will keep it up all day. A load such as
twelve horses could haul all day would represent the practical
working maximum for such a machine. A heavier load than this,
apart from emergencies which call for all the power the machine
can produce for only a very short period, would represent an over-
load for that tractor. In other words, the tractor should not be
steadily subjected to a load amounting to more than 75 per cent
of its capacity. Manufacturers warn tractor owners against over-
loading their machines because tractors will wear out very quickly
under the excessive strain and will not give satisfactory service
during the machine's greatly reduced useful life. Regardless of
the plow rating of the tractor, as for instance, three-plow or four-

GASOLINE TRACTORS 153

plow, the number of plows used should depend upon the nature
of the soil. When the latter is very heavy, or the plowing has to
be done on an up grade, fewer plows should be used. More and
better work will be done by not subjecting the tractor to any
greater load than it can pull without exerting more than 75 per
cent of its power.

ENGINE TROUBLES
FAILURE TO START

Q. What are some of the commoner causes of failure to
start?

A. Over 95 per cent of all failures to start are due to either
lack of fuel or lack of the spark to ignite it. Part of the remain-
ing 5 per cent are due to the failure of the two to come together
at the right time, while the rest may be put down to faults hav-
ing no connection with either the carburetor or the magneto.

Q. Does lack of fuel in this connection mean an empty
tank and nothing more?

A. While a great deal of energy has been expended to no
good purpose in trying to start an engine that was connected to
an empty gasoline tank, lack of fuel implies a great deal more
than that. It does not do much good to have a full tank unless
the fuel is actually getting into the cylinders every time the
engine turns over. There may be a stoppage between the tank
and the carburetor or between the latter and the cylinders. A
plugged air vent either at the tank or at the carburetor will pre-
vent the liquid fuel from reaching the carburetor nozzle. A
stopped-up carburetor nozzle will not vaporize any fuel, while a
broken throttle connection which leaves the throttle closed will
not permit any spray from an open nozzle to reach the motor, or
at least not enough to render starting easy. Air leaks at the
carburetor, the manifold, or the valve stems will weaken the
mixture considerably.

Q. Is it not as hard to start with too much fuel as with
too little?

A. Flooding the cylinders makes starting very difficult, and
when this has occurred, the only remedy is to shut off the supply
entirely and crank the motor for a few minutes to clean out the

154 GASOLINE TRACTORS

cylinders. Priming too freely is a bad practice, since the liquid
gasoline cuts the lubricating oil from the cylinder walls and
destroys the compression to such an extent that in an old engine
it is next to impossible to start even though the fuel and the
spark come together in the right place at the right time. This is
one of the unspecified causes responsible for part of the 5 per
cent of the failures to start mentioned previously. There will be
a weak explosion every time a cylinder should fire, but not
enough power will be produced to cause the engine to take up its
cycle and run.

Q. When the cylinders have been flooded by over=priming
with gasoline, what should be done?

A. Close the throttle and open the air valve or choker, so
that no gasoline is drawn through the carburetor. Take out the
spark plugs and put 2 or 3 ounces of heavy cylinder oil into each
cylinder. Replace the plugs and turn the motor over for two or
three minutes with the ignition off.

Q. Has the position of the throttle lever any effect on the
fuel supply at starting?

A. Some engines can only be started readily with the throttle
at a certain position, usually not more than one-third open and
sometimes considerably less. On a cold morning opening the
throttle too far is liable to allow too much gasoline in liquid form to
find its way into the cylinders, so that the effect is the same as
that of over-priming or flooding.

Q. How should an engine be primed?

A. Gasoline should be carried in a squirt can for this pur-
pose and not more than a teaspoonful should be squirted into each
cylinder through the pet cocks. If the engine does not start after
priming two or three times, look for some other cause of fuel or
ignition failure. If the engine starts and only turns over a few
times and then stops, the cause is likely to be lack of fuel as
indicated by the fact that it ran on what was injected into the
cylinders. In priming the float in the carburetor is also depressed
by means of a button or lever provided for the purpose. This
floods the carburetor and causes the gasoline to overflow through
the nozzle into the mixing chamber. The moment any gasoline
leaks out of the carburetor, the float should be released, since

GASOLINE TRACTORS 155

otherwise the cylinders will be flooded. Never prime the car-
buretor just as the engine is starting, as this will produce an
over-rich mixture and probably cause a pop back which may ignite
the gasoline in the carburetor.

Q. Is water in the gasoline a frequent cause of failure to start?

A. It may not be a very frequent cause, but the occurrence
of any water in the gasoline will make it difficult to start the
motor. Being heavier than gasoline the water sinks to the bot-
tom of the tank and there may be enough of it to partly fill the
carburetor. The remedy is to drain the carburetor, taking out
a half-pint or so.

Q. What effect does the use of kerosene as fuel have on
the starting of the motor?

A. It has no effect, if the matter is properly handled. At
least five minutes before the engine is to be stopped the kerosene
should always be shut off and the engine allowed to run on gaso-
line so that all traces of kerosene will be cleaned out of the
cylinders and the manifold. If this has not been done, it will
take considerable cranking to start the engine, and it may also be
necessary to inject 2 or 3 ounces of fresh oil into each cylinder to
renew the compression seal since the kerosene condenses in the
cylinders as soon as they get cold and then runs down past the
pistons into the crankcase.

Q. Will an adjustment of the mixture make starting any
easier?

A. The actual adjustment of the carburetor itself should
never be disturbed for starting purposes, as, if this is done,
either the carburetor will seldom be properly adjusted for efficient
running or a great deal of time will be spent unnecessarily in
making adjustments. Moreover the carburetor parts will soon
wear badly and make efficient adjustment impossible. Most car-
buretors are provided with a choker which, when closed, causes all
the air to be drawn past the nozzle, thus increasing the suction
and giving a rich mixture. This should be closed for starting and
opened the moment the motor gets under way. Ordinarily the
running mixture is too lean to make starting easy.

Q. What are the commoner causes of failure to start
through ignition trouble?

156 GASOLINE TRACTORS

A. Among the causes are the following: a ground or short-
circuit in the wiring; points of plugs burned too far apart; moisture
on the distributor of the magneto; failure of the contact points in
the breaker box of the magneto to separate when the cam strikes
the hinged lever; impulse starter of magneto stuck or spring
broken; putting plug cables on wrong plugs when a change has
been made just before attempting to start; badly sooted plugs;
spark lever advanced too far; and loose connections, particularly
where a separate coil is used with the magneto.

Q. What simple test can be made to determine whether
the spark is occurring in each cylinder at the proper time?

A. Take out the plugs, leaving the cables attached to them,
and lay the plugs on the cylinder head. Then turn the motor
over slowly and note whether or not the sparks occur at the
plugs in the proper sequence. Note whether there is a strong
blast of air from one of the spark plug holes each time the motor
is turned over; if not, pour an ounce or two of fresh oil into each
cylinder. The failure to start may be due to lack of compression.

Q. If, when the spark plugs are thus placed, no spark
occurs at them, where should the trouble be sought?

A. Take off the cover of the contact breaker of the magneto;
have an assistant turn the motor over slowly, and note whether
the points of the contact breaker separate twice per revolution
(four-cylinder motor). If they do separate, note whether the
faces of the contact points are clean and square. If they are
blackened or pitted, clean and true them up with a very fine file
or a strip of fine sandpaper, and then so adjust them that they
come together firmly when the cam is horizontal and do not
separate more than -£% inch when the cam is vertical. By giving
the motor a sharp turn beyond a compression point a spark will
be noted between the points; or the impulse starter may be used
and the result noted.

Q. Assuming that a spark takes place between the contact
points of the magneto, but none occurs at any of the spark plugs,
where should the trouble be sought?

A. Open up the distributor of the magneto and wipe it free
of any moisture or dirt that may have accumulated on it. Turn
the motor over and note whether the distributor brush revolves as

GASOLINE TRACTORS 157

it should. Adjust all the spark plug gaps to not more than -gV
inch; see that the plugs are properly cleaned and that they are
lying on their sides on the cylinder heads, so that only their'
bodies come in contact with the metal. If they are so placed
that the central electrodes are touching, the current will pass
through them without causing a spark, since there are then no
gaps for it to jump. In case none of these tests produces a
spark at the plugs, there is more than likely to be some internal
trouble with the magneto, though this is of comparatively rare
occurrence.

Q. When the impulse starter fails to operate, what is likely
to be the cause of the trouble?

A. Either the mechanism has become gummed up with oil
and dirt or the spring has broken. Cleaning out the impulse starter
with gasoline and re-oiling will remove the former cause.

Q. When the engine fails to start after having been primed
once or twice and cranked several times, in what order should
the cause of the trouble be sought?

A. This will depend largely upon weather conditions. In
very cold weather it is quite likely that nothing but the low tem-
perature is the cause of difficulty in starting. Results will usually
follow continued cranking, as this warms the engine up somewhat
and makes it turn over easier, with the result that the first weak
explosions may cause it to take up its cycle. In warm weather,
if a start does not follow several attempts at cranking, test the
ignition first and then the fuel supply, applying the different tests
already outlined and in about the order given.

Q. Are there any other points in the ignition system that
are likely to be responsible for failure to start?

A. If, when turning over, the motor produces a spark at the
contact breaker but none at the plugs, investigate the magneto
switch. It may have become broken or its connections may be
faulty. See that it is in the right position, sin6e many tractor
motors can only be stopped by short-circuiting the magneto by means
of the switch. In case the switch is in the S TOP position, no spark
will occur at the plugs. On some tractors the spark-advance lever
takes the place of the switch; by fully retarding it the magneto is
short-circuited, and the motor cannot be started.

158 GASOLINE TRACTORS

Q. Do the magnets of the magneto lose so much of their
strength that no current is produced?

A. In time, the heat and vibration are liable to weaken the
magneto, but this is far from being a common source of trouble.
If, after making the tests mentioned, no spark is produced, take
off the distributor plate of the magneto and rest a screwdriver
blade on the gear casing so that its end comes within J inch of
the collector ring. Turn the motor over, and note whether a
spark jumps this gap. A J-inch spark at this point will indicate
that there is no falling off in the power of the magneto. If a
spark cannot be produced in this way, there is something wrong
with the magneto itself, and it should be sent to the manufac-
turer for repairs. Ordinarily remagnetization is only necessary if
the magneto has been taken apart and the magnets allowed to
stand without a "keeper," or piece of soft iron across their ends,
or if they have been removed from the magneto and reassembled
in the wrong way.

Q. When the contact points have become so badly pitted
and burned away that they cannot be properly adjusted after
cleaning and trueing up, what should be done?

A. One or both of the contacts should be replaced and
adjusted properly. The magneto manufacturer usually supplies a
special wrench for this purpose, one end of it serving as a gage
for the proper gap between them. The lock nut of the movable
point should always be screwed down firmly after the adjustment
has been made or it will back off owing to the vibration.

Q. Are there any connections on the magneto which are
likely to become short=circuited or grounded?

A. When the wire is brought out through the side of the
magneto, the insulation may become so worn that the metal
touches the side of the opening, causing a short-circuit. In the
inductor types of magneto, such as the Remy and K-W, this is
most likely to occur at the grounding screw where the wire is
fastened to the side of the magneto. In shuttle-wound types,
such as the Eisemann, Kingston, and Bosch, the break may be
at the point where the wire is fastened to the armature or where
it is fastened to the collector ring.

Q. Can the contact breaker become short-circuited?

GASOLINE TRACTORS 159

A. Metallic dust or filings will be liable to cause this; the
remedy is to clean out the inside of the box with gasoline. When-
ever an adjustment is made, the contact points must always be
redressed so as to come together squarely. For this purpose use
only the small file supplied by the manufacturer, and take off just
as little of the platinum as possible, since it is worth consider-
ably more than gold.

Q. How can the contact=breaker box be tested for a short-
circuit?

A. Remove it from the magneto, place a piece of paper
between the points, and then hold the box within J inch of the
shaft while the magneto is turned over with the other hand. No
spark should occur; if it does, it indicates that the insulation of
the adjustable contact point is poor and should be replaced.
The test should then be repeated with the paper removed so that
the points are in contact; a spark should then occur when the
armature is turned over, the breaker box being held within J
inch or less.

Q. Does oil getting on the parts injure the magneto in any
way?

A. If allowed to get between the contact points in the
breaker box, it will insulate them. On the shuttle-wound types of
magneto there is a collector ring and brush, and allowing any oil
to get on them will prevent the operation of the magneto alto-
gether. Oil usually carries more or less dirt with it, and if
allowed to get on the distributor, it is liable to cause leakage of the
high-tension current, so that no spark occurs at the plugs.

Q. How often should the contact points of the magneto
need attention?

A. This will depend more or less on the particular type of
magneto and the engine, but they should be inspected at least
once every thirty days while the tractor is in service steadily and
trued up with the sandpaper or special file whenever the slightest
irregularity of their surfaces is evident. Taking off a little at fre-
quent intervals will keep the points in much better condition and
will save the costly platinum, since once the points start to pit
this process proceeds very rapidly. Emery should never be used
on the points.

160 GASOLINE TRACTORS

Q. Is excess oil in the motor ever a cause of failure to start?

A. When there is so much oil in the motor that considerable
of it finds its way into the combustion chambers, it will collect on
the spark plug points and insulate them, if unburned, or short-
circuit them, if carbonized. The fact that the motor apparently
ran satisfactorily just before being shut down the last time is not
conclusive evidence that the spark plugs are in good condition.
The magneto generates a high voltage when running at full speed,
and the motor will often continue to operate in spite of poor con-
ditions whereas it cannot be started again, once it has become
cold, without first remedying the faults.

Q. What is the commonest cause of failure to start a motor
equipped with low=tension ignition?

A. Dirty plugs, or ignitors, are probably the most frequent
cause. As in the case of the high-tension spark plugs just men-
tioned, the engine may continue to run with the plugs in poor
condition, but once it has been shut down and allowed to become
cold, the magneto will not produce a spark at the dirty plugs at
the low speed at which the engine is cranked. Whenever an
engine with this type of ignition is difficult to start, the first
thing to do is to examine the plugs. Give them a thorough clean-
ing with gasoline and a wire brush, taking out the moving contact
to remove any soot that has been forced into the bearing. These
plugs may be tested by laying on the cylinder head, contacts up,
and snapping the contact with a small piece of wood while an
assistant turns the motor over so that the magneto is generating.

Q. What other attention do these plugs require?

A. The contact points burn away rapidly and need frequent
dressing up to keep their contact faces from becoming pitted.
They should be trued up in the same manner as directed for the
magneto breaker-box contact points, and while the material is not
so expensive, no more than necessary should be taken off. The
operation should be repeated at frequent intervals to keep the
plugs in good condition.

Q. How may the low=tension magneto be tested to find
out whether it is generating or not?

A. Place a screwdriver blade against the single terminal of
the magneto and hold the end against some metal part of the

GASOLINE TRACTORS 161

motor while the motor is cranked. Move the tip of the screw-
driver over the metal while maintaining contact with the terminal
at the other end and sparks will be noted at the tip. A similar
test may be made by disconnecting the cable leading from the
coil. Rub the metal terminal of this cable over different adjacent
parts of the motor so that contact is made and broken while the
engine is being cranked, and much larger sparks will be noted.

Q. If, after making tests successfully, no spark is obtain=
able at the ignitor plug itself, what is the cause of the trouble?

A. The plug is likely to be at fault. Oil that has been used
for any time carries in solution a considerable percentage of
carbon in. a finely divided state. When hot, this oil is thin and
is forced into the insulation of the plug, short-circuiting it,
though apparently there is nothing wrong with it. The only
remedy is to renew the insulation of the plug.

Q. Though a test of the ignitors shows them to be in good
working condition, the motor still fails to start and examination
shows every other part to be working properly, so that the fault
is evidently with the ignition, what is the cause?

A. Either some part of the ignitor tripping mechanism has
failed, so that the contacts do not separate, or the timing has
become deranged, so that the separation takes place at the wrong
moment. In the latter case the spark is occurring in the cylinder,
but it is taking place either too soon or too late to fire the charge.
Check up the timing of the ignitor mechanism in accordance with
the maker's instruction book.

Q. How can the dry cells ordinarily used for starting with
low=tension ignition be tested?

A. A pocket ammeter, or so-called battery tester, should be
used for this purpose. Hold the tips on the cells only long enough
to allow the instrument needle to come to rest, since the ammeter
represents a dead short-circuit on the battery and will run it down
very quickly. If the reading of the ammeter shows less than 10
amperes, the batteries are of no further use for starting purposes
and should be renewed. Any other method of testing will only
show whether the battery is actually dead or not, and dry cells
may make a fairly large spark through the coil but will give a
reading of only 2 to 3 amperes on the instrument and will fail to

162 GASOLINE TRACTORS

ignite the charge in the cylinder. Batteries when this low give
out very quickly. If the switch has been left on the battery side
inadvertently, give the cells ten to fifteen minutes to recuperate
and then test again.

Q. What is likely to go wrong with the wiring of a low-
tension system?

A. About the only thing that can happen to this wiring is a
loose connection at the magneto, at the ground on the motor, at
the ignitor connection, or at the switch. The switch itself may
become short-circuited and thus prevent any current from reach-
ing the plugs.

Q. Does the tripping mechanism of a low=tensiqn system
require frequent attention?

A. The trip-rod mechanism should be inspected from time
to time to see that it is working normally, as the vibration is likely
to knock it out of adjustment. The springs should be replaced
whenever they show any signs of weakening.

RUNNING TROUBLES

Q. What causes the engine to emit smoke?

A. Among the causes are the following: an over-rich mixture
caused by faulty adjustment of the carburetor; and flooding of the
carburetor due to a leaking metal float or a water-logged cork
float. In either of these cases the smoke will be black. Oil get-
ting into the combustion chambers in excess, caused by feeding
too much oil or by broken or stuck piston rings, will produce a
blue smoke. Feeding an excessive amount of water when burning
kerosene or running the engine too cold will produce a white or
gray smoke, indicating that the kerosene is not being entirely
consumed.

Q. What is the cause of back firing through the carburetor?

A. A slow-burning fuel mixture is being fed, that is, one
either too lean or too rich, usually the former, so that there is
still flame in the cylinder when the valve opens. At times this
will occur to such an extent that the flame issues from the exhaust
pipe at the end of the muffler. This is an indication that the
mixture is too rich, since it is still burning after being exhausted
from the cylinder. One of the valves may not be closing properly;

GASOLINE TRACTORS 163

it may be held off its seat slightly by an accumulation of carbon,
or its stem may have become bent, so that the spring cannot
close it. When the ignition has been dismantled, reassembling
the cables on the wrong plugs so as to alter the firing order will
cause a back fire, but in this case the engine cannot be started.
An air trap in the fuel line or partial clogging of the latter will
also cause this at times.

Q. What are the commoner causes of missing?

A. The most frequent cause is a defective spark plug.
Owing to the heat and the vibration the porcelain of a plug will
break, but the cracks will be so small that they are invisible.
The pressure forces carbon-laden oil into these cracks and the
plug becomes short-circuited, though apparently in good order.
Test by short-circuiting the plugs in turn with a wooden-handled
screwdriver. When short-circuiting a plug causes no perceptible
difference in the running of the engine, replace it. Pitted and
badly worn contact points in the magneto breaker box wTill also
cause irregular running. (See the directions given under Failure
to Start.) Missing may also be caused by the fuel mixture being
too rich or too lean, partial stoppage of the fuel line, water in the
gasoline, defective insulation or loose connections, carbon dust on
the distributor plate of the magneto, or a sticking valve.

Q. In what other ways may spark plugs fail besides the
porcelain cracking?

A. Very frequently the electrodes burn too far apart, so that
the current is unable to jump the gap, or if it does, the spark is
weak and irregular. Plugs become foul through an accumulation
of soot in them, and to clean a badly sooted plug out thoroughly,
it may be necessary to take it apart. The insulation of a mica
plug will fail in time through the hot oil and carbon being driven
into it under pressure, and the only remedy is to replace the
insulator. Leakage around the gasket sometimes occurs, and
when it is not sufficient to cause a hissing noise, it will be indi-
cated by the porcelain of the plug becoming very dirty. Squirt a
little oil on the porcelain when the engine is running and bubbles
will form at the gasket if the plug is leaking. Cheap plugs are
made with iron electrodes, and the latter burn away so fast that
it may be necessary to adjust the gap once a day.

164 GASOLINE TRACTORS

Q. What is the cause of preignition?

A. Usually an accumulation of carbon in the combustion
chamber. This carbon deposit often takes the form of small
cones which become incandescent when the engine is running
under full load so that the fresh mixture is ignited the moment
it enters the cylinder. When running on kerosene, the piston
head may become so hot as to produce the same result. In
either case, preignition will be evidenced by a heavy pounding
and the engine should be stopped at once as this imposes a very
heavy stress on all the moving parts. Increasing the amount of
water fed with the fuel will remedy it when it is due to over-
heated pistons and the use of kerosene. Otherwise, the engine
will have to be cleaned out to remove the carbon.

Q. How can the accumulation of carbon be prevented?

A. By using only the grade of oil recommended by the
manufacturer of the tractor; cleaning it out and putting in a
fresh supply as often as directed; keeping the piston rings in good
condition, so that an excessive amount of oil cannot find its way
into the combustion chambers; and keeping the carburetor
properly adjusted, so that too rich a mixture is not used. Feed
the proper amount of water when burning kerosene. In spite of
these precautions, more or less carbon will always accumulate in
the cylinders. This amount can be kept down to a minimum by
pouring a few ounces of kerosene into each cylinder at the end of
a day's run when the engine is still very hot and leaving this in
the cylinders over night. Before starting up in the morning, the
compression seal should be renewed by putting a few ounces of
fresh oil into each cylinder.

Q. When the engine fires regularly but the explosions are
so weak that very little power is produced, what is the cause of the
trouble?

A. Some of the commoner causes are as follows: spark plug
points burned too far apart; excessive clearance at the valve stem
tappets or rocker arms, so that only a fraction of the fuel required
is being admitted; valves in need of grinding; poor compression
caused by oil not being renewed at sufficiently short intervals;
broken or stuck piston rings; leaks around spark plugs; use of a
fuel mixture that is too lean or too rich, so that slow burning

GASOLINE TRACTORS 165

results instead of an explosion; a weakened or broken valve
spring; clogging of the passages of the muffler with carbon; or
any obstruction in the exhaust piping.

Q. What causes the engine to run regularly for a time
and then to misfire badly?

A. This may be caused by switching to kerosene before the
engine has run long enough on gasoline to become thoroughly
warmed up; a valve with a bent stem that operates properly at
times and then sticks during a few revolutions; air leaks around
the valve stems or in the intake manifold; dirt in the carburetor,
so that the nozzle is partly clogged at times and free at others;
defective insulation or a loose connection which interrupts the
circuit from time to time owing to the vibration of the engine,
causing it to change position ; water in the gasoline ; carbon on the
distributor plate of the magneto; or faulty spark plugs which will
permit the engine to run regularly when idling but which will fail
the moment the load is applied. A spark plug with fine cracks in
the porcelain will fail under load owing to the greatly increased
pressure in the cylinder, but will often spark regularly when the
engine is running without load. A loose connection or weak spot
in the insulation is the most puzzling of these causes since it is
often the most difficult to find.

Q. What causes the engine to stop suddenly?

A. This is generally due to a failure of the ignition, owing
to a break in the circuit caused by a connection dropping off, the
switch suddenly opening under the vibration, or some part of the
wiring becoming short-circuited. Clogging of the fuel line or of
the carburetor nozzle or an empty tank will also result in the
engine stopping. Where the stoppage is due to failure of the fuel
supply from any cause, the engine will not usually come to as
sudden a stop as when the ignition fails. The contacts in the
breaker box of the magneto may have stuck together. If the
cooling or the lubricating system fails, it will also take more time
to bring the engine to a stop and there will be noises that give
ample evidence of the cause of the trouble. The engine should be
shut off the moment these noises occur for otherwise it will be
forcibly stopped by the binding of the pistons, thus putting the
engine out of commission.

166 GASOLINE TRACTORS

ENGINE NOISES

Q. How are the different engine noises that' signify trouble
in the operation of the motor characterized?

A. Experienced motor mechanics give a different term to
each one of several distinct classes of noise indicating faulty
operation, such as knock, hammer, pound, and slap, and to the
ear that is familiar with them each can be distinguished.

Q. What do these different noises signify to the experi=
enced ear?

A. A knock is the first indication of looseness in a bearing,
usually a connecting-rod big end, and the sound is generally that
of a sharp metallic blow. When it is allowed to develop or when
looseness in the crankshaft bearings develops, the sound becomes
louder but not so sharp and is more aptly described as hammer-
ing, owing to its similarity to the blow of a sledge. Pounding is
caused by preignition and by overheating and is so violent as to
rack the whole motor very badly. Slap is the result of worn
pistons, the skirts or lower ends of which are banged against
the cylinder walls every time the motor fires. The noise pro-
duced is very similar to that of a knock and is often mistaken
for the latter, though an experienced mechanic will seldom go
wrong on this. In addition to the noises mentioned, there is
another that is readily distinguished by the experienced ear, and
that is the clatter caused by a loose valve motion, indicating
that an excessive amount of clearance has been allowed to develop
between the valve tappets and stems or in the rocker arms. To
the inexperienced ear all strange noises will be knocks and it may
seem to be drawing too fine distincti6ns to differentiate between
knocking, hammering, and pounding, but familiarity with a motor
will enable the operator not only to make these distinctions but
to know as well what causes the different noises.

Q. Which of these noises calls for immediate attention on
the part of the operator to prevent damage to the motor?

A. A very good rule to follow is to shut the motor down
the moment any of these noises is heard and correct the trouble,
but those that call for immediate attention to prevent serious
damage are hammering and pounding. The first indicates a very
loose bearing, which may result in a broken crankshaft if allowed

GASOLINE TRACTORS 167

to run a moment longer than necessary, while pounding not only
imposes exceedingly heavy stresses on every part of the motor
but may also be the first sign of failure of either the cooling or
the lubricating system. The cause may be nothing more serious
than lack of sufficient water when burning kerosene or the fact
that the spark lever may be advanced too far.

GOVERNOR

Q. What causes the engine to race when the load is thrown
off?

A. The governor needs adjustment, or the connection between
it and the throttle has parted.

Q. What attention does the governor ordinarily need?

A. This depends largely upon the type of governor. Some
are housed in and the lubrication provided for by filling the
housing with oil; such a governor needs very little attention,
except to adjust it when it permits the engine to idle too fast.
An adjusting screw is provided for this purpose. With the engine
running, turn the screw gradually until the engine slows down
to a point where it idles satisfactorily. The governor spring
weakens in time, and the adjustment is provided to permit of
increasing the tension. Apart from this, the only regular atten-
tion required by those types which are not automatically lubri-
cated is to oil the bearings at regular intervals and see that the
connecting linkage is in good order.

CLUTCH AND TRANSMISSION

Q. What provision is made for taking up wear in the clutch?

A. The friction surface, which is usually asbestos on a wire
foundation, should be replaced when worn sufficiently to require
it. After considerable service the spring pressure may let up
sufficiently to cause unsatisfactory operation of the clutch. An
adjustment is provided for increasing the tension of the spring,
and this should be tightened just enough to make the clutch hold
under load; but it is not good practice to attempt to make up for
a badly worn friction facing by increasing the tension of the
spring. Replace the facing first. This, of course, does not apply
to the type employing metal to metal contact surfaces. Apart

168 GASOLINE TRACTORS

from this, the chief attention required is lubrication, which should
be carried out in accordance with the manufacturer's instructions,
some clutch mechanisms calling for oil as much as two or three
times a day.

Q. Is it good practice to let the machine stand with the
clutch out of engagement?

A. No; as it only weakens the clutch spring and shortens
its life. Whenever the machine is to stand more than a few
moments, the gears should be shifted to neutral and the clutch
allowed to engage. It is particularly bad practice to let the
machine stand over night with the clutch out of engagement.

Q. Are a worn friction facing and a weak spring the only
causes of a slipping clutch?

A. Allowing oil or grease to fall on the friction faces of the
clutch will cause it to slip badly.

Q. What attention does the transmission require?

A. Maintain the oil level as indicated in the manufacturer's
instructions and use only the oil called for by the latter. Drain
as often as instructed, and wash out with gasoline or kerosene
before refilling. This is usually two to three times a season,
though some types may require it oftener. When the case has
been cleaned out, inspect the gear teeth carefully for breaks,
and see that any chips or foreign matter are removed. By
filtering the old oil through several thicknesses of cloth, it may
be used for other farm machines which do not require the same
high degree of lubrication as the tractor.

Q. Does the differential require any special form of attention?

A. The differential is frequently combined with the trans-
mission, so that it is lubricated by the same supply of oil. Where
it is separate from the transmission, the attention required is the
same as that just mentioned for the transmission.

HOUSING TRACTOR

Q. Does it pay to build a special shelter for a tractor?

A. It will undoubtedly be found a good investment, since
the cost of a building large enough' to shelter the tractor and
provide a working bench beside it will usually be less than the
added depreciation incurred by leaving it exposed to the weather.

GASOLINE TRACTORS 169

*Q. When the tractor is put up for the season, what atten=
tion should be given it?

A. Before putting the machine away for the winter, the' valves
should be ground, the bearings adjusted, the valve mechanism
and the magneto overhauled, the oil drained from the crankcase
and the transmission, and the latter washed out and provided
with a fresh supply of oil. Wash the cylinders and pistons by
putting a pint or more of gasoline in each cylinder and running
the motor for half a minute. Then put a pint of fresh oil in
each cylinder and turn the motor over by hand a few times to
spread it over the surfaces; otherwise, the cylinders and pistons
may rust. Coat all exposed parts with grease and cover the
machine with a tarpaulin or old canvas. Make a list of all
replacement parts necessary and order them at the time the
machine is put away in order that they may be installed during
the winter.

INDEX

PAGE

Air, need for cleaning 41

Air cleaners 43

air-washer type : . . . . 43

attention required 45

centrifugal type 43

felt baffle type 45

Air conditions in tractor 41

Air and gasoline supply 29, 30, 37

Air washer 43

Amperage and voltage 66

Automobile and tractor 1, 60, 111, 126

Avery horizontal-opposed engine 90

Bearings 134

Bevel friction drive 109

Bosch impulse starter 84

Camshaft and timing gear 19

Carburetor 145

Centrifugal air cleaner 43

Centrifugal governors 97

auxiliary types 99

built-in types 102

Circuit 64

Clutch 103

Clutch troubles and remedies 167

Condenser 70

Conductors 63

Cone clutch 108

Contact breaker 78

Contracting-band clutch 108

Control in gasoline tractors 97

clutches 103

engine governors : 97

transmissions Ill

Control system lubrication 133

Cooling circulation, types of 57

Cooling systems in gasoline tractors 56, 149

Current 62

Distillates of petroleum 27

2 INDEX

PAGE

Eagle horizontal engine 90

Eisemann impulse starter 86

Electrical principles 62

circuits 64

conductors 63

electric current 62

electrical units 63

low- and high-tension 67

voltage and amperage 66

Electrical units 63

Engine 9, 153

failure to sta/t 153

Engine parts 10, 14, 134

details of operation 134

engine bearings 134

pistons 142

valves 137

Engine troubles 153

clutch and transmission 167

engine noises 166

failure to start : 153

governor 167

housing tractor 168

running troubles 162

Engine types 87

Expanding-shoe clutch 107

Explosion motors 25

Failure to start engine 153

Felt baffle air washer 45

Final-drive group 123

Firing order 80

Force-feed splash lubrication 52

Forced cooling circulation 58

Four-cycle motor 9

Four-cycle principle 10

compression stroke 11

exhaust stroke 12

intake stroke 10

power stroke 1 '-

Fresh-oil lubrication 55

Friction drive 109

bevel friction drive 109

Fuel

products of distillation

vaporizing 128

INDEX 3

PAGE

Fuel supply system 16, 25

air and fuel balanced ? 37

details of spraying process 31

effect of increasing speed 32

fuels available 26

gasoline and kerosene carburetor 39

heating requirements 34

need for cleaning air 41

operating principle of internal-combustion motor 25

proportion of air to gas 30

tractor air conditions very bad 41

types of air cleaners 43

vaporizing fuel 28

Gas and air in carburetion 29, 30, 37

Gasoline heating requirements in carburetion 34

Gasoline and kerosene carburetor 39

Gasoline tractors 1-169

analysis of tractor mechanisms 9

control system 97

motors 9

introduction 1

operation 125

Governor 97

Governor troubles 167

Heat efficiency of motors 56

Heating requirements in carburetion 34

gasoline 34

kerosene 35

High-tension ignition system 69

High-tension magneto 76

High-tension magneto circuit 77

Horizontal engine 89

Eagle 90

horizontal-opposed Avery 90

Oil-Pull 89

Horsepower ratings 152

Housing tractor 168

Ignition system 16, 61

electrical principles 62

importance of 61

types of ignition systems 68

Impulse starter 84

Bosch 85

Eisemann . , 86

4 INDEX

PAGE

Induction coil 69

Internal-combustion motor, principle of 25

Internal-combustion vs. steam tractors 9

Kerosene and gasoline carburetor •>. 39

Kerosene heating requirements in carburction 35

L-head motor, valves in 18

Low-tension currents 67

Low-tension ignition 68, 73

spark coil 68

timing of 73

Low-tension magneto 72

Lubrication in gasoline tractors 45, 129

Magneto 72, 76

high-tension 76, 81

low-tension 72

Magneto impulse starter 84

Make-and-break-circuit mechanisms 70

Modified splash lubrication 49

Moline vertical tractor motor 94

Motor 9, 153

Motor governor 97, 107

Motor lubrication of gasoline tractors 129

Motor parts 10, 14, 134

Motor troubles 153

Motor types 87

horizontal engine 89

vertical motors 93

wide range 87

O
Oil, necessity for discarding when used 52

Parrett vertical motor 94

Piping and connections for fuel supply in gasoline tractors 142

Plate clutch 106

Pressure-circulated lubrication 54

Pressure and temperature in explosion motor 12, 45

Radiator, protection of from stresses 59

Rating motors 152

Running troubles 162

INDEX 5

PAGE

Sixteen-valve engine 24

Twin City multiple-valve engine 25

Spark coil 68

Spark gap 71

Spark plugs 81

Splash lubrication 48

Spraying process in carburetion 28, 31

Steam vs. internal-combustion tractors 9

Temperature and pressure in explosion motor 12, 45

Thermosiphon circulation 58

Timing gear : 19

Timing valves '. 21

Tracklayer vertical motor 93

Tractor (see Gasoline tractor) 1

Tractor air conditions very bad 41

Tractor and automobile 1, 60, 111, 126

Tractor classes 2

development of tractor industry 2

lack of standardization 2

types of tractors 3

Tractor clutches 103

functions 103

friction drive 109

types 104

Tractor fuel supply system 16, 25

Tractor ignition system 16, 61

Tractor industry 2

Tractor lubrication 129

control system 133

motor 129

Tractor mechanisms 9

control system 97

motors 9

Tractor motor troubles 153

Tractor motors 9

cooling system 56

fuel supply system 25

ignition system 61

lubrication system 45

types of motors 87

valves and valve timing 18

Tractor operation 125

carburetor 145

cooling system 149

engine parts 134

engine troubles 153

6 INDEX

PAGE

Tractor operation (continued)

general instructions 125

horsepower ratings 152

lubrication 129

Tractor parts giving most trouble 126

spares necessary 127

Tractor selection 4

financial return 4

size of farm 5

size of tractor 6

work done on demonstration no criterion 4

Tractor size 6

factors governing capacity 8

margin of safety 7

power for belt work 7

Tractor transmissions Ill

final drive 123

function 112

heavy types 116

intermediate types 117

range of types 112

special types 119

speed vs. weight Ill

speeds 113

Tractor types 3

Transmission Ill, 167

Twin City multiple-valve engine 25

Valve movement, lead and lag of 22

Valve timing 18, 22

Valves 137

Valves and valve timing 18

camshaft and timing gear 19

lead and lag of valve movement 22

need of closely checking valves 24

placing of valves

sixteen- valve engine 24

timing valves 21

valve details 18

Vaporizing fuel

mixing gas and air 29

spraying necessary

Vertical motors 93

Holt and Tracklayer 93

Moline 94

Parrett

Voltage and amperage 66

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