Full text of "Ignition, valve timing and automobile electric systems (self-starting and lighting) a comprehensive manual of self-instruction on the operation, adjustment and repair of magnetos, battery ignition systems, and self-starting mechanisms. Complete tables and data on valve timing for a great number of American automobiles. The Ford ignition system and its adjustment"

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Ignition, Valve Timing

and

Automobile Electric Systems

(SELF-STARTING AND LIGHTING)

A Comprehensive Manual of Self-Instruction on the Opera-
tion, Adjustment and Repair of Magnetos, Battery Ignition
Systems, and Self-Starting Mechanisms. Complete Tables
and Data on Valve Timing for a Great Number of American

Automobiles

The Ford Ignition System
and Its Adjustment

By JOHN B. RATHBUN

Formerly Editor of "Ignition and Accessories." Author of

"Gas Engine Troubles and Installation" "Gas, Gaso-

line and Oil Engines" "Aeroplane Engines"

and "Aeroplane Construction and Operation."

Trouble Chart

FOR

Ignition and Starting System

CHI o>\.a o

SlANTSN««^VAKViiET@.

PUBLISHERS

"««"_*i. VSi?«'

I-

■No-

Pref

rerace

Many of the troubles from which motorists have suffered in
the past — and still suffer, in fact, despite recent improvements
in construction of all the essential parts of, the automobile — ^have
arisen from failure of the ignition system to perform its proper
function. While these troubles may perhaps be minimized in the
^^ latest model cars, there are still in daily use in the United States
and Canada many thousands of machines built and equipped in

^ the days of motor-car development, and to every owner and oper-

ator, no matter whether his car be new or old, the subject of
ignition is of the utmost importance.
^' To know what to do in case of ignition troubles, it is impera-

■s

vi tive to learn something definite about the principles of the igni-
^ tion system used on the car. Intelligent handling of the car in
emergencies can only be assured when the operator possesses
such information. It will not pay to "go it blind" in seeking the
causes of ignition failure. When the engine stops or misbehaves
from such causes knowledge is indeed "power."

The object of this treatise is to equip the reader with such a
Ir-^owledge of the interesting subject of Ignition that he will be
ab.c to handle his own particular apparatus with intelligence and
skill. The mere consciousness that he understands the principles
and construction of his ignition devices will add immensely to his
comfort on the road, giving him greater confidence in himself
as a driver and stripping the ignition bogey of most of its terrors*

"'1

•. . .• i 'C^j:^'

Every modem ignition device, whether for the automobile,
motor-boat or stationary engine is described so fully and at the
same time in so simple a manner that the text is of equal value
to the beginner and the veteran repair man. No previous knowl-
edge of electricity is necessary for a full understanding of the
matter contained in this volume. Examples of well known com-
mercial apparatus follow the descriptions of the various systems,
together with notes on their installation and repair. Particular
attention is paid to the operation of the high tension magneto and
to the various forms of dual ignition circuits.

Probably the most unique and useful features of the book
is the chapter on valve timing, a subject on which very little has
appeared heretofore in book form. Even the little that has been
published has been so elementary or so indefinite that it was prac-
tically useless to the practical man. In contrast we publish the
exact timing figures issued by nearly every prominent automobile
manufacturer for different models of cars so that even a begin-
ner can obtain the correct results without experiment. Firing
orders of four, six, seven, eight and twelve cylinder motors are
given in addition to the material on timing.

As the electric self starting and lighting system bears a definite
relation to the ignition system on most modern cars we have cov-
ered the construction, operation and repair of this feature in a
very simple and careful manner. A complete chapter is devoted
to the care of the ignition and starting storage battery alone.

THE AUTHOR.

CONTENTS

% v

Page
Partjl* Igi|itioa Principles. Combustion, Engine Cycles, Four-
Stroke^ Cycle, Ignition Principles, Ignition Systems, Hot
Tube Ignition, (Electric Ignition, Chemical Batteries, Mag-
netic Effect of Current, Make and Break System, Series
Connections, Induction or Secondary Coil, High Tension
Ignition Circuit, Condensers, Multiple Cylinders, Storage
Batteries, Magnetos, Ignition Dynamos, Battery Timers, "^
Firing Order, Advance aiid Retard, Spark Position, Fixed
Ignition^ Ignition Governors, Vibrator Coils, Multiple Cyl-
inder Circuits 7

Part IJ. Modem Battery Sjrstems. Non-vibrator Coils — Snap
Kreak Timers— ^High Tension Distributers — Modern Bat-
. tery Circuit Diagrams — ^Atwater Kent System — Remy Sys-
"^ tern — Bosch System — Westinghouse System — Connecticut
System — Delco System — Rhoades System — Circuit Breaker
Construction and Adjustment — Fixed Spark — Effect of
Plug Location, etc 43-53

Part III. Magneto Principles — Low Tension Magneto System.

Magnetic Field — The Armature — Windings — Generation of
Current — Low Tension Igniters — Igniter Adjustment —
Magneto Circuits ^ 54-66

Part IV. High Tension Magnetos. Principles of High Tension
Magnetos — Transformer Type — True High Tension Type
— Inductor Type — Double Windings — The Distributer —
Primary Breaker — Safety Gap— Gearing Ratios — Typical
High Tension Magneto Circuits — Splitdorf — Connecticut —
Eisemann — Magneto — Two Point Ignition Theory — Effect
of Advance on Magnetos — ^Automatic Advance 67-90

Part V. Single— Dual— Duplex — Independent— Two Point Mag-
neto Ssrstems. Magneto Wiring and Connections for Va-
rious Combinations of Battery and Magneto — Typical Cir-
cuits 91-95

Part VI. Representative High Tension. Magnetos. Eisemann

. True High Tension Magneto— Bosch Four Cylinder Mag-

neto^Bosch Circuit Diagram — Bosch Oscillating Magneto

"—Inductor Magnetos — Remy Magneto— Remy Circuit —

"K. W." Magneto— Herz-Ruthardt 96-112

0.'

CONTENTS

Part VII. Advancing Field Tsrpe Magnetos. Mea Magneto—

"Dixie" Magneto— Installing Magnets 113-123

Part VIII. Ignition Troubles and Remedies. Poor Insulation
— Broken Wires — Sooted Plugs — Discharged Battery —
Cracked Porcelains — Pitting — Coil Troubles — Punctured
Condenser — Truing Up Contacts — Misfiring — Summary of
Battery Troubles — Magneto Troubles and Adjustment —
(High Tension Type) — Low Tension Troubles — Modern
Battery Systems and Repairs — Preignition — High Tension
Magneto Troubles — Testing Circuits, etc 123-159

Part IX. Electric Starting and Lighting. General Arrange-
ment of Circuit — The Motor — ^The Generator — The Motor-
Generator — Cut-Out — Current Regulation — ^Two Unit and
Single Unit Systems — Circuit Diagrams — Armature Fields

— Field Connections — Series Wound — Compound Wound —
Delco System — Bijur System — Gray-Davis System — Eclipse
Bendix Connector — General Remarks 160-187

Part X. Valve Setting and Timing. The Four Cycle Principle
— Relation of Valves to Piston Position — Valve Setting
Diagrams — Average Motor Timing — Valve Lap— Auxiliary
Ports — Concrete Examples for the Valve Timing of a Num-
ber of Well Known Cars — Stationary Engine Timing — Tim-
ing Offset Cylinders — Firing Order — Firing Order Chart —
Eight Cylinder Firing Order — Twelve Cylinder Firing Or-
der — Timing of Knight Motors — Firing Order of Gnome —
Valve Sizes for Different Gas Velocities — ^Timing Ford Car. 188-212

Part XI. Ford Troubles and Adjustments. The Ford System—
The Ford Magneto — Wiring and Connections — Ford Mag-
neto Troubles — Magnetizing Magneto Magnets — Weak
Current — Removing Magneto— Damage to Insulation —
Armature Clearance — Commutator and Adjustment — Gen-
eral Notes on Care and Repair 209

Part XII. Magneto Chart and Timing Instructions. Charg-
ing Magneto Magnets — ^Timing Magnetos — Setting Pistons
— Setting Breaker Points, etc 219

Part XIII. Storage Battery and Starting Repairs. Discharged
Cells — Gravity — Evaporation — Low Gravity — Standing Idle
— Voltage too High — Open Vents — Full Charge — Charging
— Dynamo and Motor Troubles — Sparking at Brushes —
Poor Contact — Chattering — Grooves — Dirty Commutator —
Weak Magnetic Field — Excessive Load 229

CHAPTER I.
IGNITION PRINCIPLES.

* ••* t

Combustion. The gasoline and gas engine are of a
class of prime movers known as "Heat engines" — that is,
they convert heat energy into useful mechanical energy
through a process of combustion. The mixture of fuel
and air is burned within the cylinder, after it has been
compressed to a comparatively high pressure, and the
sudden increase in pressure due to the expansion causes
the piston to move against the load and deliver energy
to the engine shaft. The fuel must always be vaporized
or in a gaseous state when used in a gas or gasoline
engine, and must be mixed with the proper proportion
of air in order to burn it to its lowest chemical condition.
It will be seen that the ignition or "Kindling of the
mixture is of the greatest importance, and the various
methods of obtaining the igniting spark and the proper
regulation and adjustment of the different parts of the
apparatus are vital elements in the operation of a gas or
gasoline engine.

In any engine, the mixture of fuel and air must be
highly compressed in order to obtain efficient combus-
tion, and a reasonable amount of work out of a given size
cylinder. If the gas is ignited at atmospheric pressure,
the combustion is slow, much heat is radiated and lost,
and the resulting pressure due to the expansion of the
gas is relatively low. Thus an engine compressing to
60 pounds per square inch will only develop about one
horsepower for every 10 cubic inches displaced by the
piston, while compressing to 110 pounds per square inch

8 IGNITION PRINCIPLES

will increase the capacity to a point where 3.8 cubic inches
will produce one horsepower. The thermal efficiency will
be increased from about 18 percent to 28 percent.

Engine Cycles. In order to operate continuously and
deliver power, the engine must go through s^ routine of
operations, each act being performed over and over in the
same order. Each of these operations is known as an
"Event" and the complete series of events, is known as a
"Cycle" or as a "Cycle of Events*" In any ,gas , engine
the following events must take place: (1) The cylinder
is filled with an explosive mixture, (2) The mixture is
compressed, (3) Ignition takes place,. ^4) The pistoa
moves out on the working stroke to produce the power^
(5) The exhaust gases are liberated and then cleaned out
of the cylinder. The engine is classified by the number
of piston strokes taken to accomplish this cycle of events,
for there are a great number of possible combinations
between the events and the number of strokes required
for the cycle. Thus, a two-stroke cycle motor completes
the five events in two strokes, or one revolution. . A fourr
stroke cycle engine goes through the series once in every,
four strokes, or in every two revolutions. As the fo;ur-.
stroke cycle is used almost exclusively in automobile,
practice, we will confine ourselves to a description of.
this type.

A full understanding of the cycles is of the utmost,
importance in ignition and valve setting, and the subject
must be thoroughly studied and committed to: memory.
before proceeding further. The opening and closing of
the valves, and the timing of the ignition apparatus, of
course depends entirely upon the time at which the events
take place in regard to the piston position.

Four-Stroke Cycle. This cycle, which is often called
the "Four-Cycle," is the most commonly used for sta-^
tionary and automobile engines. As before explained, the
five events take place during four strokes, or two revolu-

. I , », .'. .; ^-

IGNITION PRINCIPLES 9

tions of the crankshaft. According to the strokes, the
events take place in the following order :

Stroke 1 (Suction Stroke). The piston moves toward
the crank and sucks in a charge of the combustible
mixture.

Stroke 2 (Compression Stroke). The piston now
moves back in the opposite direction, compressing
the mixture. At the end of the compression stroke,
the spark occurs and fires the gas.

Stroke 3 (Working or Power Stroke). The hot, ex-
panded gas creates a high pressure on the piston, and
produces the power. At the end of the stroke, the
pressure is much reduced, the exhaust valve opens,
and the gas rushes out to atmosphere.

Stroke 4 (Scavenging Stroke) . The piston now returns,
moving away from the crank, and pushes out the
residual gas left in the cylinder.

At the end of the fourth stroke, the cycle starts over
again by sucking in a charge for the next combustion.
It will be noted that two events occur at the end of the
compression stroke (Stroke 2) — that is, both ignition and
compression. In practice, the spark does not occur at the
exact end of the compression stroke, but a few degrees
before, as the gas takes time to burn, and combustion is
assumed to be completed at the center. Since the exhaust
gas takes a definite length of time in which to get out
of the cylinder, and thus reduces the pressure to that of
the atmosphere, it is allowed to start before the piston
actually reaches the end of the stroke.

Fig. 1 is a diagrammatic outline of the four-stroke
engine with the piston (P) starting out on the suction
stroke, the piston moving down along the arrow (m).
Through the connecting rod (R), the piston is moving
the crank (C) in the direction of the arrow (n). The com-
bustible mixture formed in the carbureter is drawn into

10 IGNITION PRINCIPLES

the cylinder through the inlet port (I) and the open inlet
valve (B). This valve is opened and closed by the cam
(IC), which is driven from the crankshaft through the
gear (C). The exhaust valve (A), which allows the
burnt gas to escape to atmosphere, remains closed during
the suction stroke, as shown. Slightly after the piston
reaches the lower end of the suction stroke, and starts up
on the compression stroke, the inlet valve (B) closes.

Fig. 2 shows the piston traveling up on the compression
stroke in the direction of the arrow (m'), and as will be
seen, both the valves (A) and (B) are closed so that
pressure can be built up. At the upper end of the com-
pression stroke, the spark (S) occurs in the spark plug
(Q), and in such a way that the spark is in direct contact
with the mixture and thus starts combustion. Theoretic-
ally, combustion should be complete before the piston
starts moving down on the working stroke, but practically
the spark occurs slightly before this point, so that the
flame will have time to spread through the entire volume
of the mixture. The crank is still revolving in the direc-
tion of the arrow (n), and after the ignition takes place
the piston starts down on the working stroke.

Fig. 3 shows the piston near the end of the working
stroke, and at this point the pressure is reduced and the
exhaust valve (A) is opened for the escape of the burned
gas, as shown. This valve movement is produced by the
exhaust cam (EC), driven from the crankshaft through
the timing gear (G). In the majority of engines, the
exhaust valve opens from 40 to 45 degrees of crank travel
before the crank reaches the lower dead center. Crank
rotation still in the direction of (n).

Fig. 4 shows the exhaust valve still open on the
"Scavenging" return stroke, during which time the piston
is pushing out the remainder of the gas. Near the upper
end of this stroke, the exhaust closes, and the inlet opens
ready for the next suction stroke and the next cycle. The

IGNITION PRINCIPLES

Fig*. 1-2-3-4. Tbe Five Events of the Fonr Stroke Cycle EnEiDc

12 IGNITION PRINCIPLES

burnt gas retained in the cylinder during this stroke is
reduced to atmospheric pressure, but even this must be
expelled in order to prevent the dilution and contamina-
tion of the next charge of mixture. A very small per-
centage of burnt gas will seriously reduce the capacity of
the engine.

The engine makes two revolutions during this cycle,
and as the valves only operate once during this time, it is
evident that the cams (EC) and (IC) must operate at
exactly one-half the crankshaft speed. For this reason,
the ratio of the gears (G) and (G') to the driving gear on
the crankshaft is as one is to two, and are therefore often
referred to as the "Half-time Gears." The exhaust cam
(EC), and the inlet cam (IC), are of different form, as
the inlet and exhaust valves remain open for different
periods of time. The spark is controlled by an automatic
switch known as a "Timer" or "Breaker," and is also
driven at some exact relation to the camshaft speed. The
exact speed ratio of the spark timer depends a great deal
upon the number of cylinders used, hence this is likely to
vary from 1 to 1, up to 4 to 1.

Ignition Systems. Up to the present, we have only
considered the spark as a spark without inquiring into its
origin. There are many ways of producing an igniting
spark or flame, and during the development of the internal
combustion engine the following methods have been em-
ployed: (1) OPEN FLAME ignition, in which the flame
ignited the gas through a "Touch hole" after the manner
of an old-fashioned cannon; (2) HOT TUBE ignition, in
which the gas was ignited by contact with the incan-
descent walls of a tube; (3) HOT WIRE ignition, in
which an electrically heated wire fired the charge; (4)
CATALYTIC ignition, produced by the condensing effect
of platinum black; (5) COMPRESSION, as in the Diesel
engine, by which a spray of fuel is vaporized and ignited
by coming into contact with highly compressed air ; and

SIX

IGNITION PRINCIPLES 18

(6) ELECTRIC ignition, performed by producing an
electric spark in the midst of the mixture. Ignition by
methods (5) and (6) are by far the most common, and it
is very seldom that one encounters any of the remaining
systems. On gas and gasoline engines, electric ignition
is used almost exclusively, but the compression system
-is especially adapted to heavy oil and kerosene engines,
aft<l for thes6 fuels has almost entirely supplanted
electricity.

Hot Tube Ignition. In the older engines the hot tube
was very commonly used, but it had many drawbacks and
was finally superseded by the electric system. Fig. 5
shows the cylinder (C), >vith the hot tube (B) screwed
into one end of the cylinder. The tube is opened into the "
cylinder, but is closed at the outer end, and is heated to
incandescence by the burner flame (A). When the piston
moves up on the compression stroke, tKe mixture is forced
back into the tube until it finally comes into contact with
the upper hot portions of the tube, and ignition occurs.
By arranging the length of the heated portions of the tube
or by moving the flame, the time of ignition can be con-
trolled to some extent. The further up the hot portion
was located, the longer it took for the gas to reach the
heat, and the later the ignition occurred. This was de-
cidedly unsatisfactory, for the tubes would burn out, and
it was difficult to exactly control the timing. With the
engine throttled down on light loads, the compression
would not be sufficient to force the gas back to the hot
spot, and the engine was likely to misfire. For this reason,
it was practically restricted to hit-and-miss engines.

Electric Ignition. The electric system has succeeded
the hot tube and presents many advantages, although it
is still far from being an ideal ignition method. It depends
for its operation upon the fact that a current of electricity
passing through an air gap heats the air to incandescence,
and the heat thus produced will ignite any mixture in the

IGNITION PRINCIPLES

vicinity. The resistance offered by the air, when current
is jumping or flowing between two points, generates a
heat in the same way that heat is produced by resisting
the pull of a rope, or in £act by resisting any force in
motion. The more rapid the flow of current, and the
greater the resistance offered, the higher will be the tem-
perature. Since the resistance of air is many thousands
of times greater than the resistance of the copper wire

c Jump Spark SysH

Fig. S I> the Old Hot

through which it flows, it is evident that a given current
will produce much more heat in the air gap than in the
conducting wire, especially with the air gap concentrated
in a very small space.

Fig, 6 shows an electric spark gap (S) installed in the
cylinder (C). The current is produced by some source
which we will, indicate by (D), and is conducted to the
spark gap by the wires (A) and (B). We will assume
the current to flow from (D) through the wire (A), and
then down the center electrode or conductor (M). At the
lower end of the electrode (M), is a small air gap (S),

IGNITION PRINCIPLES 15

which separates the electrode from the opposite point
(V). After jumping across (S), between (M) and (V)
the current flows back to the source through the cylinder
walls (C) and the return wire (B), which is shown dotted.
The conductor (B) is not always a wire, but in many
cases is formed by the metal frame of the engine. This
serves the same purpose and avoids much complication
and many troublesome connections. The path through
which the current makes its round trip from the source,
and then back to the source (D), is called a "Circuit," and
this must be complete from start to finish before the cur-
rent will flow.

Chemical Batteries. In the early ignition systems, the
current was nearly always produced by batteries, and this
practice still exists to a limited extent. The primary bat-
tery produces current by chemical means, the chemical
reaction consuming the battery elements in exactly the
same way that heat energy is produced by the combustion
of coal. In the majority of primary batteries, zinc is used
as the fuel, and this is converted into zinc chloride with
the further loss of the acid or corrosive fluid. As this
method of producing current is simple, inexpensive, and
has not moving parts, it is very satisfactory for some
branches of ignition service.

A dry cell and its circuit is shown by Fig. 7. This con-
sists of a zinc can (C), in which is a paste of sal ammoniac
solution and some absorbent material such as blotting
paper. In the center of the can, and in contact with the
paste is the carbon rod (A), which is also known as the
"Positive Electrode." The action of the sal ammoniac
(Electrolyte) on the zinc and carbon surfaces establishes
an electrical difference of potential, or difference in
electrical pressure, which causes the current to flow
around the circuit. In the figure, the carbon rod (A) and
the zinc can (B) are connected with the copper wire (W),
thus forming a circuit through which the current flows in

16 IGNITION PRINCIPLES

the direction shown by the arrows. It will be noted that
the current flows from the carbon or from the "positive"
connection to the Zinc or negative connection. In the
industry, the positive pole is designated by (+), and the
negative by (-), as marked in the figure. On the inside
of the battery cell, the current flows through the paste
in the opposite direction, or from negative to positive,
but this latter fact need not interest us much at this point.
The direction of flow is important, for in some appliances
it is necessary to maintain the flow in a certain direction
for the operation of the device. A current which flows
continuously in one direction, as shown, is called a "Con-
tinuous Current" or a "Direct Current."

Magnetic Effect of Current. When an iron bar is sur-
rounded by a coil of wire, as shown by Fig. 8, and current
is flowing through the coil, the bar is magnetized and
becomes capable of attracting and holding pieces of iron
or steel as long as the current flows. If the bar is of very
soft iron or steel, it demagnetizes instantly, and drops
the pieces that it had been holding. In Fig. 8 the mag-
netizing coil, or "Solenoid," is indicated by (C), and the
iron bar by (S-N), the arrows showing the direction of
current flow around the iron "Core." The current is sup-
plied by the dry cell at the left. The effect produced by
the coil is that one end of the bar is magnetized to a
North seeking polarity (N), while the other end (S)
would point to the South pole of the earth if the bar and
coil were pivoted and allowed to swing like the needle
of a compass. This tendency to turn in a fixed relation
to the earth is a distinguishing property of magnets, and
holds true of electromagnets as well as with the perma-
nent magnets more commonly used in compasses. A field
of magnetic force extends around the bar (Magnetic
Field), and any metallic body lying in the field is in-
fluenced by it. The general outline of the magnetic field
is indicated by the dotted lines (M). There are only a

IGNITION PRINCIPLES 17

few substances that are affected by the magnetism or
which can be magnetized. These are iron, steel, nickel,
and one or two very rare metals. Brass or wood are not
magnetized, but they do not prevent the passage ot the
electrical field — in fact, all non-magnetic substances are
practically transparent to the magnetic force.

The external magnetic eifect is always greatest at the
poles (S) and (N), the attractive power growing less and
less as we approach the center of the bar. It should also

Figs. 7-8. Simple Eleciric Circui

be noted that two poles, North and South, are always pro-
duced, and that neither pole can exist alone. The polarity
of the magnetic bar bears a fixed relation to the direction
in which the current flows through the coil (C), If the
fingers are pointed in the direction of current flow and
the thumb is held at right angles to the fingers, then the
thumb will point to the North pole of the bar. When
the current starts to flow and build up in strength, the
magnetism increases with it and the Magnetic Field (M)
spreads out from the bar. When the current is cut off,
the field immediately contracts and returns toward the
bar, and cuts or travels through the turns of the coil.
Since it is the common practice to illustrate magnetic

18 IGNITION PRINCIPLES

force by a series of lines, as shown, the magnetic force is
sometimes called "Lines of Force" or "Magnetic Lines,"
and in some cases it is called the "Magnetic Flux."

The current flow cannot build up instantly in a circuit
containing a coil, and the value of the electric current
builds up very slowly when the number of turns or the
quantity of iron within the coil is increased. The retard-
ing influence is known as "Inductance," and this is caused
by an opposing current produced by the spreading mag-
netic lines of force acting on the turns of the coil. When
magnetic lines of force cut through conductors or wires,
they generate an electric current in the wire, and this
always opposes the flow of the current that energizes the
bar. When the electric circuit is broken, the contracting
lines of force cut through the coil and generate a current
that tends to continue the current. This "Induced" cur-
rent is in evidence when a circuit is broken, the induced
current appearing as a flame that continues for a short
time at the point where the wires are separated. The
more the turns, and the greater the mass of iron in the
core (S-N), the greater will be the induced current volt-
ages. Thus in Fig. 8-a, the separation of the wire ends
(E) and (G) produces a gap which the voltage of the
induced current is able to break down and thus produce
the arc or flame (F). A straight, simple circuit has very
little inductance.

Make-and-Break System. In the make-and-break sys-
tem advantage is taken of the inductance, and the ter-
minals of a highly inductive circuit are broken or sepa-
rated in the combustion chamber of the engine, thus
producing an igniting spark when the circuit is opened.
The coil (Spark coil) consists of a number of turns of
heavy copper wire, while the core (S-N) is built up of
the very fine soft-iron wire which will magnetize and
demagnetize very rapidly when the circuit is closed and
opened. This method is generally applied to large, slow-

IGNITION PRINCIPLES

speed engines, for the weight and inertia of the moving
parts prevents effective operation at very high speeds.
Series Battery Connections. The electrical pressure or
"Voltage" developed by a single dry cell is very low,
about 1.5 volts as an average. As the voltage required
by the ignition system ranges from 6 to 8 volts, we must
find some means of increasing the voltage. This is done
by connecting a number of cells in series, as shown in
Fig. 9, the total voltage of the three cells 1, 2 and 3, being

•*"f@l h - -^

'^f gffffffflh ^

BXTB^lML C/^aC/lT

jHrGf. ^-7>seEZ' GsLLdJfv,Sk7ei^^

equal to the sums of the cell voltages, or 1.5+ 1.5+ 1.5 =
4.5 volts. For 6 volts we would use 6.0/1.5 = 4 cells.

It will be noted that in series connection the positive
connection post of one battery cell is connected to the
negative of the next cell, or in other words, the connection
posts of opposite polarity are connected. The external
circuit is then connected to the unoccupied terminals of
the two end cells, as shown, the external circuit in this
case being the coil or solenoid (S-N).

Induction or Secondary Coil. The voltage required for
forcing the igniting spark across the points of the spark
plug is very high, this requiring many thousand volts.
It would be impractical to obtain this voltage directly by
batteries, for then a 15,00Q-volt ignition circuit would re-
quire 10,000 dry cells connected in series. The use of an

IGNITION PRINCIPLES

inductance or "Booster" coil in the circuit, as already
explained, is not possible in many cases, so that we must
have recourse to some magnetic system by which we can
boost up the low battery voltage to the high potentials
required at the spark gap. This is accomplished by a
double-wound coil, known as an induction or secondary
coil (Transformer Coil), which magnetically increases the
voltage in the battery coil to a high voltage in the sec-
ondary coil. This is shown by Fig. 10.

A soft-iron core (N-S) is wound with a few turns of
heavy wire (C), and is called the primary coil. It is
through this coil that the battery current flows, and hence
is the coil which magnetizes the core (N-S). Over the
primary coil, and thoroughly insulated from it, is the sec-
ondary coil (B), which consists of many thousands of
turns of very fine wire. The primary coil is connected
to the batteries 1, 2 and 3, so that the primary circuit can
be closed and opened by the switch (A). The ends of the
secondary winding are separated by the spark gap (G),
and this corresponds to the spark gap of the plugs.

When the primary switch (A) is closed, the battery cur-
rent flows through the primary coil and magnetizes the
core (N-S). The expanding magnetic flux cuts through
the turns of the secondary coil and thus generates a cur-

IGNITION PRINCIPLES 21

rent in the secondary. Since the voltage induced is pro-
portional to the number of turns, the thousands of turns
in the secondary are capable of being arranged for almost
any voltage desired. The ratio of the secondary and
primary -voltage is roughly proportional to the ratio of
turns of the secondary to the turns in the primary. Thus,
with 36,000 turns in the secondary, and 40 turns in the
primary, the voltage in the secondary will be approx-
imately : 36,000/40 = 900 times. If the battery voltage
in the primary is 6 volts, then the secondary voltage will
be : 6 X 900 = 5,400 volts.

It should be noted that the current in the secondary is
"Alternating" — ^that is, the current flows back and forth
instead of in the same direction as with the continuous
battery current. The secondary flows in one direction
when the primary switch is closed, and in the opposite
direction when the primary is opened. The voltage is
greater when the switch is opened and the primary cir-
cuit is l)roken, for this causes the most abrupt change in
the speed of the magnetic flux, and hence the highest
voltage.

High Tension Ignition Circuit. Several modifications
must be introduced into the circuit of the simple sec-
ondary coil, just shown. The switch in the primary cir-
cuit must be opened automatically at the instant that
the piston arrives at the end of the compression stroke,
so that ignition will take place here. Again, since the
change in the value of the magnetic flux in the core must
be as quick as possible, we must provide some device in
the primary circuit that will absorb the inductive spark
that occurs when the switch is opened. This spark causes
the current to flow for an appreciable time after the switch
is opened, thus prolongs the duration of the primary flow
and causes the voltage to increase very slowly. If a con-
denser is connected across the terminals of the primary
coil, or across the contact points, it will absorb the in-

22 IGNITION PRINCIPLES

ductive energy developed in the primary, and thus will
greatly increase the "Snap" and energy of the secondary
spark in the plugs.

Fig. 11 shows the elementary features of a high-tension
ignition circuit. A revolving switch or "Timer" is driven
at a given speed by the engine, and alternately opens and
closes the primary coil (C). The switch blade is so located
on its shaft that it breaks the primary circuit just before
the piston reaches the end of the compression stroke. The
revolving switch arm is (A), the shaft is (B), and the
stationary contact segment is (D). A condenser (I) is
connected across the ends of the primary coil to suppress
the sparking at the breaker points (D) and (R), and to
increase the energy of the secondary circuit.

One end of the secondary coil (S) is connected with the
spark plug (F) inserted in the cylinder (J). The high-
tension current passes through the plug and into the com-
bustion chamber, causing a spark to take place at the
spark gap (H). The wire is well insulated from the metal
of the cylinder, and after the spark jumps the gap thie
current returns to the secondary winding through the
frame of the engine, as indicated by the dotted line (E)
and (E'). This circuit contains the essential elements
of the high-tension battery ignition system.

The Condenser. Fig. 12 shows a detail of the con-
denser and its construction. The primary coil is shown
by (C) connections to the condenser (D), serving to lead
the induced current to the condenser. The condenser
proper is made up of alternate piles of tinfoil and paper,
the paper serving to insulate the adjacent tinfoil leaves.
One-half the tinfoil sheets are connected to one end of
the coil by (A), while the other half of the sheets are
connected to the co^l terminal (B). In the figure the tin-
foil sheets (t-t-t-t) are connected to (A), while the sheets
(t'-t'-f) are connected with terminal (B), the plates being
piled alternately right and left. In very good coils the

IGNITION PRINCIPLES

condenser insulation is mica instead of paper, and this
gives excellent results but is expensive.

Firing Multiple Cylinders. When more than one cyl-
inder is used, a separate coil may be used for each cylinder,
or a single coil may be provided with a revolving "Dis-
tributer" switch, which connects the cylinders with the
coil alternately and in the proper firing order. The Ford
automobile uses four coils, one for each cylinder, but the
majority of cars use a single coil with a high-tension dis-

JmjTiX^

J3/iTTE!ltY

Mote/
dotted l/ne shows couf^e

OF (^ROUNDED C(/Ri^Er^77/^Et?a^
F^/fMEOrj^A/G/^C.

MvsAaaaah

4wvi/1awwvs

n^NaiJ

Fig. 11. High Tension Circuit.

tributer. In any case the primary circuit is interrupted
periodically by the "Timer," so that each coil receives
its proper primary impulses at the correct time. The
timer revolves at camshaft speed, or at half the entire
revolutions.

Storage Batteries. When a dry cell is exhausted or
''used up," it cannot successfully be restored to its former
usefulness, and it is cheapest to throw it away. The zinc
is badly eaten away, and the solution or "Electrolyte" is
neutralized and practically destroyed. By passing cur-
rent backwards through the cell, some of the zinc is taken
out of the solution and deposited on the zinc, but this

IGNITION PRINCIPLES

method takes considerable time and patience and does not
turn out right. With wet batteries the solution-and zinc
element can be renewed easily and cheaply, and- the wet
cell is generally best for stationary engines. For auto-
mobiles and portable engines wet batteries are not a
decided success because of the slopping of the solution
and the chances of leakage.

Fig. 12. Primary Circuit.

= The storage or "Secondary" battery is entirely different
in construction from the primary battery, and can be
recharged repeatedly by passing a charging current
through the cell in a direction opposite to that furnished
by the battery. This is a very convenient system, for the
battery will absorb electrical energy while the engine is
running, and will give it up either while running or when
the engine is stopped. The voltage of a storage battery
is higher than that of a primary cell, averaging from 2.0
to 2.5 volts per cell, and this of course means that fewer
cells are connected in series for obtaining a g^ven total
voltage. The capacity of a storage battery is greater for
a given size, and the current is steadier when heavy
draughts are being made on the battery.

IGNITION PRINCIPLES 25

The solution i$ a mixture of sulphuric acid and water,
while both the positive and negative electrodes are lead.
Zinc and carbon are not used in a storage cell. The plates
or electrodes are pasted. with a lead salt, and this is dif-
ferent on the positive and negative plates. The plates are
generally in the form of a latticework of metallic lead into
which the lead paste is forced. When the charging cur-
rent is passed through the plates and solution, the paste
is decomposed and the density of the solution is altered.
This difference in chemical composition between the posi-
tive and negative plates sets up a difference of potential
or voltage of from 2.0 to 2.5 volts, depending upon the
state of the charge. When current is drawn from the cell
the paste gradually returns to its original composition,
and the voltage falls off until at full discharge the voltage
is zero. It is best to recharge the battery long before it
reaches the fully discharged stage, as the acid is likely to
destroy the plate.

Magnetos. A magneto is a sort of alternating current
dynamo used for ignition, the magnets being of the
permanent type. A coil of wire, known as the "Arma-
ture," is rotated between the ends of the horseshoe
shaped magnets, and the magnetic flux cuts the wire
turns arid generates an alternating current in them.
The electrical energy in this case is produced by the
mechanical energy of the engine, and when the engine
stops generation also ceases.

The current thus generated may be of low voltage and
passed through an induction coil like the battery current,
or the full spark voltage may be generated directly within
the winding of the magneto. In the former case the mag-
neto is known as a low-tension magneto, while the latter
is a high-tension magneto. The armature winding of a
high-tension magneto is very much like that of a sec-
ondary coil. It has a primary and secondary winding, and
the primary current is interrupted at the instant when

26 IGNITION PRINCIPLES

the spark is required by an automatic switch known as an
interrupter or primary breaker.

In onft-cylinder or two-cylinder engines the high-tension
current is led directly to the spark plugs from the arma-
ture, but when more cylinders are used it generally be-
comes necessary to use a high-tension distributer, which
distributes the current to the various cylinders in the
proper firing order. The armature of the high-tension

Fig. 13. Typical High Tension Magneto.

magneto must be driven at some fixed relation to the
;ngine speed by means of gears, and the armature must
be adjusted so that the interrupter will open just when
the piston approaches the end of the compression stroke.
This type of magneto is probably the most commonly
used types of ignition apparatus, and is not subject to
deterioration as with the primary and secondary batteries.
The low-tension magneto may furnish current directly
to the igniter in the case of the low-tension make-and-
break system, or it may be used with a secondary coil for
the high-tension spark. A low-tension magneto is sup-
plied with the Ford car, and supplies current to four high-

IGNITION PRINCIPLES^ 27

tension coils mounted on the dash of the car. E,v means
of a two-way switch either the magneto current »i the
battery current may be used at the will of the driver. The
battery current is generally used for starting the engine,
while the running is done on the magneto.

Ignition D3'namos. An ignition dynamo is driven f.'om
the engine and delivers direct or continuous current in-
stead of the alternating current delivered by the magneto.
For this reason it can be used for charging storage bat-
teries, since these batteries can only be charged by direct
current. Permanent magnets are not generally used on
dynamos, since it is difficult to regulate the voltage for
charging, hence the field magnets are electromagnets

28 . IGNITION PRINCIPLES

with-co\ls of wire called the field coils, which magnetize
thr ^oles. Since the current in any armature is always
alternating, the dynamo must be provided with a device
known as a commutator for collecting the armature and
rectifying it into direct current for the external circuit.
The commutator is a drum built up of insulated copper
bars, the bars being connected symmetrically to groups of
windings on the armature. Resting on the surface of the

1 from Crankshaft of

commutator are bars called "Brushes," which collect the
current from the commutator bars in such an order that a
positive commutator bar is always connected with a posi-
tive brush.

Part of the current is taken from the brushes and is
passed through the field coils for magnetizing the sta-
tionary field of the dynamo. The current can be used for
lighting and for starting the motor, as well as for the
ignition, and if a storage battery is used the lights can
be used for some time with the engine standing dead.
Current may be taken from the dynamo, from the battery.

IGNITION PRINCIPLES 29

or from both if the dynamo should be charging the battery
at that time.

Battery Timers. Battery timers vary greatly in detail,
but in general they consist either of a series of stationary
contacts^ which are successively touched by a revolving
arm, or by a cam-pperated lever arm, which makes con-
tact with a. stationary point intermittently as the cam
passes under the cam-arm roller. The latter is the more
common on modern battery systems, although the former
"Commutator Type" is used on the Ford automobile.
The commutator type h^s as many stationary contact seg-
ments as there are cylinders, and a single rotating arm,
but the lever breaker is arranged so that there ar^ as many
lobes on the cam as cylinders.

Firing Orden The purpose of the multi-cylinder en-
gine is to divide the total power into a number of very
small, evenly-spaced impulses so that vibration is reduced
and so that there is a uniform flow of power. For this
reason care must be taken to divide up the impulses so
that they occur at equal intervals, and this means that the
primary breaker must measure off equal angles for the-,
contacting arm. "' "^

We know that a idn|f!e-cylinder four-stroke cycle engine
gives one power impulses every two revolutions, from
which it follows that a two-cylinder engine of the same
type will give one power impulse in every revolution, or
twice -a^ many impulses in a given time. To find the
number of impulses given per revolution by any number
of four-stroke cylinders, divide the number of cylinders
by two. Thus a twelve-cylinder engine will give 12/2 =
six impulses per revolution. In the case of a two-stroke
engine there are twice as many impulses per cylinder,
hence there are as many impulses per revolution as there
are cylinders.

Measured on the crankshaft, the angle between the fir-
ing impulses will be equal to 360, divided by the impulses

80 IGNITION PRINCIPLES

per revolution. With a twelve-cylinder engine there will
be six impulses per revolution, hence the angle between
the impulses will be : 360/6 = 60 degrees apart. In some
engines, notably with the "Vee" type used on aeroplanes
and motorcycle motors, the exact theoretical angle may
introduce certain practical difficulties, hence the actual
angle may be somewhat different than that specified.
In most cases it is very necessary to have the engine as

Eight Crtinder "V« Type" Motor (Plan View), Sho-^ing the Two MkV. **
Four Cylinder! Each, and the Dynamo Between the Blocks at the Unit. .

narrow as possible, and with an angle of 60 degrees be-
tween the cylinder blocks, the over-all width may be too
great. The angle of the Liberty motor and the Packard
"12" is thus made 45 degrees instead of 60, but the
difference in the running and balance is hardly noticeable
at high speed.

Vertical and opposed cylinder motors having 2 or 4
cylinders have the crank throws all in one plane with
half of the crankpins on either side of the shaft. Vertical
engines -with 3 and 6 cylindefs have the cranks in different
planes. That is, a six-cylinder will have the cranks a,r-

IGNITION PRINCIPLES 31

iH ranged in pairs, each pair being at an angle of 120 degrees
en , with the next pair. If the cylinders are arranged in "Vee"
ne : form, a simple straight six-throw crankshaft can be made
es ' with the throws all in one plane. A "Vee" type eight-
ly cylinder has the same type of shaft as a four-cylinder

,al vertical, with the cranks all in one plane, but an eight-

4 cylinder vertical requires that the crank throws be ar-

ns ranged so that one-half the throws are at right angles to

the remaining half of the throws. The use of more than
four cylinders in vertical arrangement requires a com-
plicated crankshaft and the offsetting of the crankpins in
the manner mentioned, while the "Vee" arrangement
means a short, simple shaft that is comparatively easy to
make. All this has an influence on the order in which the
different cylinders are fired.

As a general rule, cylinders follow sequence at opposite
ends of the engine — that is, the first front cylinder is fol-
lowed by one as near the rear end as possible, so that the
fore and aft rocking moment is reduced to a minimum.
Calling the front cylinder of a four-cylinder engine "No.
1," the firing order for the average "Four" will be :

1— 3 — 4r-2

First at the front and then to the back, keeping the
moments about the center of gravity opposite and as
nearly equal as possible to prevent fore and aft rocking
and vibration. If No. 1 was followed immediately by No.
2, both explosions would be on the same side of the center
of gravity and there would be an unopposed moment that
would cause rocking. By having a front cylinder and then
a rear, the moments about the center oppose one another.
For perfect opposition No. 4 should follow No. 1, but this
is impossible, as the crankpin of No. 4 would be on the
wrong side of the crankshaft and the piston would be at
the bottom of the stroke instead of the upper end of the
compression stroke, as it should be. Cylinder No. 3 is

IGNITION PRINCIPLES

FIBER.- TUBE

tiSASS TUBE

@= ^ . 1 ) e=?v ' ^^

Fig. 12. — Supports for High Tension Wires Leading to Spark Plugs. Disk
at Left Represents Distributer of Magneto or Battery Distributer and Wires
Shown Leading Out Through Run Are Connections to Spark Plugs. Courtesy
of "The Automobile."

IGNITION PRINCIPLES 33

as near as we can approach the theoretical condition.
Cylinder No. 4 follows No. 3, and then follows No. 2 on
the opposite side of the center. There are a n amber of
combinations possible.

There is some divergence in the firing order of six-
cylinder engines, for the possible combinations are, of
course, much greater than with the four. The following
are examples of six-cylinder vertical orders :

1—5—4—6—2—3
1 — 5 — 3 — 6 — 2 — 4
1—4 — 2 — 6 — 3 — 5
1—2^3 — 6 — 5—4

It is very fortunate that the greater percentage of motor
manufacturers have established the practice of marking
the firing order on the engine. A discussion of several
different makes will be found under the chapter on
"Timing," page 201.

Advance and Retard. For the best results the com-
bustion should be completed at the end of the compres-
sion stroke and before the piston starts out on the down-
ward power stroke. Since the mixture requires some time
in which to burn, it is evident that the igniting spark
must occur some time before the end of the stroke is
reached. When the spark occurs before the center, it is
known as an "Advanced Spark." The exact amount of
advance depends upon the quality of the mixture and the
speed of the engine, for some mixtures burn faster than
others, and at high speed the time for combustion is
greatly reduced, and hence the spark must be started
earlier or must be advanced further than at low speed.
Generally, the ignition apparatus is arranged so that the
spark position may be varied by hand to meet the differ-
ent running conditions.

At low speed the engine will pull best when the spark
occurs later than at high speed, and in this condition the

34 IGNITION PRINCIPLES

spark is said to be "Retarded." The time allowed for
combustion is now greater than at high speed, and hence
the spark is needed only very slightly before the upper
center, or in some cases ev.en slightly after the piston
starts down on the working stroke. ^If the engine should
be throttled down without retarding the spark, the com-
bustion would be completed long before the piston would
reach the top of the compression stroke, and there would
be a very strong tendency toward reversing the engine,
and hence the power would be much reduced at low speed
and the parts of the engine would be severely strained.
This condition of an over-advanced spark makes itself
known by producing a heavy knocking or pounding in
the engine. On the other hand, if the spark is retarded
too far the engine will overheat, due to the fact that the
flame exists longer during the working stroke, and hence
is longer in contact with the cylinder walls. If the spark
is kept much retarded, the radiator is likely to boil over
and the valves will eventually become burnt or pitted
because of the hot gases and flame sweeping over the
seats.

Spark Position in Starting. When the engine is being
started the spark must be well retarded to avoid "Kick-
backs" on the crank. In cranking a motor with an ad-
vanced spark, the explosion will take place before the
crank reaches the upper dead center, and thus the crank-
shaft will be turned suddenly and violently in a direction
opposite to that of the desired rotation. This is very
likely to cause serious injury to the operator, and has
been the cause of many broken wrists, loss of teeth and
other disagreeable consequences. ALWAYS RETARD
THE SPARK BEFORE CRANKING.

Running Position of Spark. When the speed of the
engine is increased, the spark should be advanced accord-
ingly, until it is just short of the "knocking point." After
the throttle is opened the spark is advanced until ham-

IGNITION PRINCIPLES

Magneto Circuit Diagram for 12 Cylinder "Vee" Type Engine; Dinie Mapietoi.

36 IGNITION PRINCIPLES

mering starts, and then is slowly retarded until the knock-
ing just ceases. Whether the spark is first advanced or
the throttle is first opened before the spark lever is
touched is a matter of opinion, but at any rate the engine
should not be run longer than possible before the spark
is adjusted to the correct point, or close to the knocking
point. Any other position causes a loss in power, heat-
ing, or other trouble.

Fixed Ignition. On some automobiles the spark posi-
tion is fixed and out of the control of the operator. This
is to avoid the tendency of the average driver toward
keeping the spark in the wrong position, and in the case
of a careless operator is often advantageous. The fixed
spark is never exactly in the proper position at any speed,
but is arranged so that it is a compromise of all speeds.,
and hence the average results are likely to be better than
with a slip-shod control by a careless or ignorant driver.

Ignition Governors. This is a great step in advance
over the fixed ignition spark, and at the same time can
be arranged so that the control is taken out of the driver's
hands. The spark is automatically advanced and retarded
in proportion to changes in the engine speed, but, of
course, it does not compensate for various qualities of
mixtures. The timer or primary breaker is advanced and
retarded by some form of centrifugal governor, and ad-
vances the spark as the speed rises.

Trembler or Vibrator Coils. In the majority of the
older coils, and in a few modern battery ignition systems,
a vibrator or breaker is used on the coil, which rapidly
opens and closes the primary and thus produces a series
or a shower of secondary sparks at the plug. Instead of
a single spark at the moment when the timer breaks the
circuit, the vibrator causes a series of sparks to continue
as long as the timer remains closed. A vibrator coil makes
starting easy, and produces better general results with a
poor mixture, but is more complicated and difficult to

IGNITION PRINCIPLES 37

keep in order than the single-spark coil just described.
In running some coils are provided with a switch, which
cuts out the vibrator when the engine is up to speed and
is in normal operation, the vibrator only being used for
starting.

The vibrator acts much like the ordinary door buzzer,
and is operated through the magnetization of the core. It
consists of an iron blade, which is provided with contact
points, and is included in the primary circuit in such a way

that it opens the circuit when the magnetized core pulls it
away from the contact. As soon as the contacts are opened
the core becomes demagnetized, and a spring then pulls
the vibrator blade back into its original position with
the contact points closed. The current now again flows
through the primary, the core is again magnetized, and
thus pulls the vibrator blade open and again breaks the
circuit. This occurs over and over again at the rate of
several thousand vibrations per second — in fact, the blade
when in proper condition produces a shrill hum.

The contact points on the vibrator blades eventually
get hammered out of shape, and the continual sparking
finally pits and bums them so that attention must be
paid to this point.

38 IGNITION PRINCIPLES

Multiple Cylinder Battery Circuit. Fig. 16 shows a
complete battery circuit four, a. four^ cylinder motor in
which R', R^ R^, and R* are the spark coils, N is the
battery, and Z is the tinier or commutator. The spark
plugs are shown above the coil and connected to the high
tension terminals of the coils S^ S^ S' and S*. The
knife switch M cuts out the battery when the engine is to
be stopped.

Twelve Cylinder "Opposed" Type Engine, with Cylinders on Opposite Sidea et

The timer shaft E carries the arm F, and at X is pivoted
the roller contact lever H with the roller at I. A spring
G forces the roller into contact with the inner walls of
the timer (W-W-W-W) so that the roller makes suc-
cessive contact with the brass segments (A-B-C-D) while
it revolves. Each segment is connected with a coil, and
the instant that the roller touches a segment, the corre-
sponding coil sends sparks to a cylinder. The timer
housing (Z) can be rocked back or forth by the spark
lever (K), so that the spark will occur earlier or later
in the piston stroke and thus procure advance and retard

IGNITION PRINCIPLES

Typical Four Cylinder Batterv Coil Circuit ShowinB liie Timer Z, t
mp Spark Coils R1-R2-R3 and ft4, the Batteries N. the Switch M and I
ari Plugs V1-V2-V3-V4.

40 IGNITION PRINCIPLES

of the spark. When shifted toward the right, the seg-
ment meet the roller earlier in the revolution and thus
cause the spark to occur sooner (Advanced spark). Turn-
ing the housing to the left causes the spark to occur later
(Retarded spark) . The timer shaft is "Grounded" or con-
nected with the engine frame at (L), and the battery is
grounded to the frame at (O) so that the frame acts as a
conductor or wire between the timer shaft and the battery
and thus saves one wire.

The timer shaft is of course geared to the engine in
such a way that the roller moves in exact relation to the
piston position.

IGNITION, TIMING, ETC. 41

MASTER VIBRATORS

With multiple cylinder engines trouble is often experienced, when
vibrator coils are used, for the reason the spark does not occur in all
of the cylinders at the same time. This trouble is particularly notice-
able when there is a coil for each cylinder and a vibrator is used with
each coil.

Spark variation under these conditions is almost invariably caused
by the difference of the weights and tensions in the different vibrators,
and by the different electrical characteristics of the coils themselves.
When a vibrator or coil does not respond instantly to the contact
made by the timer, the coil is said to "lag" behind the current impulse.
All coils lag to some extent, as it is impossible to instantly o

Pig. IS. — Master Vibrator Circuit Diagram.

the inertia of the vibrators or (o overcome the self-induction of the
primary winding.

With different adjustments, the different coils in a set have different
degrees of lag, which results in varying the timing of the spark in the
cylinders to which they are connected. With cylinder No. 1. for
example, firing regularly on the upper dead center it will often be
fourid that cylinder No. 1 is firing 20 degrees after and that cylinder
No. 3 is firing S degrees before center. This means that with cylinder
No. 1 in the proper position, cylinders 3 and 4 are losing power for
the reason (hat they are not utilizing the compression to the fullest
extent It should not be understood from this that the spark should
always occur exactly on the upper dead center for the best results,
this point being given simply as an example.

It will be evident from the foregoing that if we used a single vibrator

42 IGNITION, TIMING, ETC,

for all of the coils we would have a constant vibrator lag for all, and
that the spark would be alike in all of the cylinders, providing oi
course that the timer was in good condition. This is exactly what
is accomplished with the "Master Vibrator" system in which a single
vibrator is placed in series with all of the coils through the primary
circuit.

The master vibrator generally consists of a small wooden case in
which a vibrator, a magnet coil and a condenser are enclosed. The
magnet acts on the vibrator in the same way that the primary coil
and core acts on the vibrator of a single unit spark coil. The con-
denser connects across the vibrator terminals in the same way and
acts for all four or six coils.

In Fig. 15, 1-2-3-4 are the four coils of a four cylinder motor, and
11-21-31-4^ are the four spark plugs in the respective cylinders. The
timer T is connected to the primary windings of the four coils through
the terminals s-s-s-s. The common return R leads from the coils to
the master vibrator terminal H, the revolving arm of the timer being
grounded at G.

The master vibrator, which is shown greatly enlarged for the sake
of detail, is enclosed in the case F. The connection H leads to the
vibrator leaf V from which the current passes through the contacts
A and the coil B to the battery E. The battery is grounded at G^.
The common condenser C is connected across the vibrator contacts
at H and A. The magnet core D is alternately magnetized and
demagnetized by coil B as the contacts A close and open. The action
of the vibrator, core, condenser, and magnets is the same as in an
ordinary spark coil.

It will be seen that the coil B and the vibrator are in series v/ith
all of the coils.

Effect of Coil Efficiency on Cells. Inefficient spark coils are pro-
verbally "battery hogs" and should not be tolerated even on the
cheapest of automobiles. In the lower grade of spark coils little
attention is paid either to the construction of the vibrator or to the
proportions of the primary and secondary coils. The following table
was compiled from tests made by V. A. Clark, published in the "Gas
Review:"

Resistance, Current, Retail Price,
Coil No. Ohms Amps. Coil

1 0.619 0.5 $3.00

2 2.732 0.2 1.50

3 0.519 0.6 2.10

4 0.617 0.5 2.75

5 0.562 0.5 1.50

6 2.394 0.2 1.50

7 0.924 0.5 1.50

8 0.814 0.4 1.50

IGNITION, TIMING, ETC, 43

PART II
MODERN BATTERY SYSTEMS

While battery ignition was the earliest used on the automobile it
had many objectionable features due to the crude methods adopted
in timing the spark and in constructing the coil. Owing to the exces-
sive current demanded by the inefficient coils, to vibrator adjustment,
and to the prolonged contact made by the timers, dry batteries would
soon become exhausted and would lay down on the job at the most
unexpected and inconvenient times. Storage batteries, while giving a
more uniform flow of current and requiring less attention, had the
disadvantage of being removed from the car during the charging
operation. To avoid the trouble of charging the cells at the proper
intervals, they were usually neglected until they were well sulphated,
which generally meant either a new cell or a thorough overhauling.

With the advent of the electric self-starting and lighting systems
all of these conditions have been changed. The lighting battery is
always kept in the proper condition by the continual charging of the
lighting dynamo so that there is a constant supply of current at a
uniform voltage available for ignition purposes. There is no need
for removing the storage battery for the reason that all of the neces-
sary elements in its operati6n are installed in the car. Dry cells are
not needed except as an auxiliary or for emergency use, and the
troublesome vibrator coil is a thing of the past.

While the magneto proved a great step in advance over the old
type of battery system, it too had many failings. It was usually a
difficult matter to start a car with an ejcclusive magneto equipment,
it seldom gave a satisfactory spark at low engine speeds, the very
time when a hot spark was needed, and when it did get out of order
it was almost impossible for the ordinary mechanic to repair.

Under the new conditions the battery system is as capable of a hot
spark as the magneto, and the efficiency of the engine is in no way
reduced by its use, but as a matter of fact is really increased in the
modern types. The battery system will "accelerate" or build up
speed more rapidly than a magneto for the reason that the magneto
does not give a hot spark at the low starting speed and therefore
does not build up as rapidly as the acceleration requires.

IGNITION, TIMING, ETC, 45

General Description

In general the modern battery system consists of three principal
units: (1) the induction coil; (2) the primary circuit breaker; (3) the
high tension distributer; these items being, of course, exclusive of the
battery.

The principle of the induction or spark coil was explained in a
previous chapter, the function of this coil being to increase the low
battery voltage to the many thousands of volts required to jump
across the spark plug gap.

As before explained, this coil consists of two independent windings,
a coil of coarse wire called the "primary," and a coil of many thou-
sands of turns of fine wire called the "secondary."

The primary circuit breaker corresponds to the timer or com-
mutator of the old system, inasmuch as it breaks the primary circuit
and causes the spark to take place at the outer end of the piston stroke.
The circuit breaker usually runs at cam shaft speed, or what is the
same thing, at half crank shaft speed.

In the majority of cases the circuit breaker contact points are
mounted in a movable housing so that the points may be rocked back
and forth to obtain the retard or advance of the ignition.

With one exception the new battery systems are of the single spark
or non-vibrator types, a single break in the primary circuit causing a
single spark at the end of the compression stroke. The elimination
of the vibrator does away with the mechanical inertia or lag that was
so troublesome with early battery systems.

In all types only a single coil is used, whatever the number of
cylinders, the high-tension current being led to the different cylinders
in the proper order by a revolving switch called the "distributer."
This generally consists of a revolving metal blade that turns beneath
a series of contacts, there being as many contacts as spark plugs. A
lead from the coil carries high-tension current to the revolving blade,
which in turn makes successive contact with the contact points in the
proper firing order. As both the distributer and the circuit breaker
run at the same speed they are generally mounted in one unit for
convenience.

In general these systems can be divided injto two general classes,
those that are of closed circuit type and those of the open circuit type.
The closed circuit type have the circuit breaker points normally in
contact, completing the primary circuit until the time arrives for
the spark. With the open circuit type, the primary circuit is both
made and broken instantly at the time of ignition.

With the closed circuit method, the current is on for so long a
period that the iron core of the coil becomes thoroughly saturated
magnetically, producing a spark of great intensity at the moment the

46 IGNITION, TIMING, ETC,

circuit is broken. It is evident that the closed circuit timer is only
for use with storage batteries, since the long duration of contact
wouli soon exhaust dry cells. When the circuit is closed and broken
almost instantly as in the Atwater-Kent system, the current consump-
tion is very small, which permits the use of the open circuit type with
any source of current supply.

Current for the operation of the coil is taken from either the starting
and lighting current or from dry cells, or both, if an auxiliary is
required to provide for the case in which the storage battery is run
down by too frequent starting.

With the closed circuit system in which the battery system is nor-
mally flowing provision is made for cutting off the current automat-
ically when the engine stops with the main switch left open through
carelessness. This in one case is accomplished by means of a ther-
mostat connected in circuit, the heat produced by a continuous flow
warming the thermostat and therefore opening the circuit. In the
majority of cases the main switch is arranged so that the current is
reversed through the breaker contact points every time the switch is
closed. In this way the life of the points is greatly iiTcreased, as the
metal is not electrolytically transferred from one contact to the other.

THE ATWATER-KENT SYSTEM (Unisparkcr)

In the first models of the Atwater-Kent its use was confined almost
exclusively to dry batteries as its momentary spark was exceedingly
economical in the use of current. It consists of one unit comprising
the distributer and circuit breaker, and a second unit consisting of the
single spark, non-vibrating coil and switch. With this system the
intensity of the spark is independent of the motor speed, the duration
of current also being independent. Since the breaker is positively
driven at cam shaft speed, and as no vibrator is used the spark
obtained is practically independent of the battery condition. Nor-
mally the contact points are held apart, and at the proper time are
forced into contact for an exceedingly brief space of time.

Owing to this short duration of contact, the amount of current
taken is exceedingly small, thus making it possible to use a set of
dry cells for period several times greater than with the ordinary
commutator. As the contacts are normally in such a position that
the circuit is open, it is impossible to exhaust the battery by leaving
the switch closed. It is impossible for the engine to come to rest
with the points of the breaker in contact.

In Fig. 3 is shown the operation of the Atwater-Kent primary
circuit breaker, the diagrams being arranged progressively so that
the cycle can be more easily seen. A cam S is fastened to the rotating
shaft which has a number of teeth cut on its circumference corre-

IGNITION, TIMING, ETC.

spending to the number of cylinders. The trigger T catches inter-
mittently in these notches and is therefore pulled a short distance at
each engagement in the direction shown by the arrow. When the
trigger is released from the tooth it rides up for a short distance

Fosit/cy? A/Q/

f^/y-/'o/7 A/o.2

/^bs/f/o/yA/gJ

/^3/f/b/7AtL^.

Fig. 3. — Atwatttr-Kent Primary Circuit Breaker Shown in Four Suc-
cessive Positions.

on the rounded top of the tooth and then returns to its normal
position through the tension of the spring P.

When the trigger jumps back to its normal position it strikes the
intermediate hammer H which in turn transmits the blow to the con-
tact spring F which closes the circuit. The duration of this contact
is necessarily very short since it is equal only to the time required

48 IGNITION, TIMING. ETC.

for a comparatively stiff spring to snap back into its unstrained
position. Tungsten contact points are used for the reason that
tungsten has a higher fusing point and is very much harder than
platinum, thus giving a minimum of trouble due to pitting or upset-
ting. In addition to the improvement of the contact points, it should
be noted that the current is reversed in direction at every "make" so
that the usual trouble due to electrolytic transfer is avoided. Adjust-
ment of the points is affected by the removal of metal shims placed
under the head of the contact screw. Since the normal position of
T is below and out of contact with the hammer it is impossible for
the device to be held in a contacting position. Contact is caused
only by the inertia of T forcing it above its normal position. The
cam, trigger, and hammer are all of hardened steel so that there is
but little wear.

One model known as K-2 is provided with a governor which auto-
matically advances the spark with increasing speeds. This consists
of four weights spaced equally around the shaft, the rotation of these
weights shifting the cam through an extreme angle of 38 degrees.
This angle at crank shaft speed is equal to 76 degrees, measured on the
crank circle. The weights are controlled by .springs so that their
movement is in direct proportion to the speed of the shaft. In the
type provided for manual advance and retard, the entire case is
rotated by an external lever.

The high tension distributer is a blade mounted on top of the
shaft which receives the high tension current from a central contact
point. This blade rotates directly beneath the terminals of the high
tension cables. The small gap between the blade and the terminals
offers but little opposition to the spark and does eliminate the trouble
due to brush wear.

RHOADES BATTERY SYSTEM

The Rhoades battery system consists of a make and break mechan-
ism and a high tension distributor, contained in a single casing, the
non-vibrating coil and the attached switch being ordinarily fastened
to the dash. The primary circuit breaker operates on the open
circuit principle, this being arranged so that if the switch is left
closed it is impossible to exhaust the battery. The contacts are
always separated when they are at rest. A trigger on the shaft
trips over four or six teeth (depending upon the cylinders) and raises
a collar, also attached to the shaft. When one of the notches on the
collar comes over a projection on the contact springs, the trigger
trips over the tooth. This lets the collar down, momentarily forcing
the contacts together and then permitting them to spring apart
instantly.

IGNITION, TIMING, ETC, 49

In this way, a single spark is produced at each break and as the
duration of contact is exceedingly short, there is but little demand
on the battery. In fact this is so efficient that weak dry cells may
be used with good results. The high tension distributer consists of
a radial arm carrying a brass segment which passes in close proximity
to the terminals of the high tension leads. There is no rubbing con-
tact at this point and no wear or trouble with deposits of metallic
dust that so often cause short circuiting.

THE REMY BATTERY IGNITION SYSTEM

The Remy system is designed for use with storage battery cur-
rent and can be used either on 6 or 12 volts. It is divided into three
units, the circuit breaker, the high tension distributer, and the coil.
Referring to Fig. 7, the cam is shown by C, which operates the arm
lever A through a hardened follower indicated by F. There are as
many faces on the cam C as there are cylinders, each corner of the
cam raising the follower lever. The follower lever A carries one con-
tact point which makes contact intermittently with the stationary
point held in the block B. The coil spring S normally holds these
points in contact. The distributer for the high tension current is
mounted above the circuit breaker, and is arranged in such a way
that it is stationary at all times and is not affected by the advance
and retard of the circuit breaker. This obviates the necessity of
moving the high tension wires every time that the advance is altered.
A radial arm keyed to the rotating shaft constitutes the moving ele-
ment of the distributer, the current being fed to the blade by means
of a carbon brush mounted in the cover. As with the majority of
distributers, the revolving arm does not make actual contact with the
high tension wire terminals, but allows the spark to jump through a
small air gap between the two sides of the circuit.

THE CONNECTICUT BATTERY IGNITION SYSTEM

The primary circuit breaker of the Connecticut system consists of a
pivoted lever actuated by a cam through a roller follower, in a
manner similar to a magneto circuit breaker. One contact is mounted
in the free end of the lever, while the second contact is mounted
in a stationary insulated block. A spring holds these points normally
closed. The cam is provided with as many prongs as there are cyl-
inders, each cam prong breaking the primary circuit and causing a
spark as it passes under the follower roller on the pivoted arm.
Probably the most unique feature of the Connecticut system is the
thermostatic switch which breaks the primary circuit should the
main switch be left closed while the engine is left standing. A small

IGNITION, TIMING, ETC, 51

thermostat is enclosed within the switch proper which heats when
the current passes through it from 30 seconds to four minutes with-
out interruption by the circuit breaker.

The heating of the thermostat causes the deflection of a contact
bar, which in turn closes the circuit through a small magnet. When
the magnet is energized, the armature vibrates the same as the
clapper of an electric bell, and coming into contact with the stops
attached to the main switch, releases the switch and opens the pri-
mary circuit.

BOSCH BATTERY SYSTEM

The Bosch battery system can be used independently or in connec-
tion with a magneto. With this system the circuit breaker and high
tension distributer are combined in one unit, while the coil is inde-
pendent. The distributer, which of course runs at cam-shaft speed,
can be driven at any convenient point on the engine.

A plan view of the circuit breaker is shown by Fig. 5, in which the
driving shaft A carries the cam C, the latter rubbing against the fiber
piece F, thus opening and closing the primary circuit. The contacts
are mounted so that one is on the movable arm M, while the other
is on the stationary block B. The arm M is controlled by the spring
S. Advance and retard is obtained in the usual manner.

For starting, the switch is provided with a vibrator, which in turn
is controlled by a button in the center of the switch plate. Under
normal conditions a quick push on the button will cause a single
spark in the cylinder, which is on the power stroke. With a very
cold motor a succession of sparks as produced by a vibrator. The
vibrator button can be locked in position until the motor is started,
after which it is turned to the single spark position.

Four switch positions are provided: B for battery, M for magneto,
MB for both together, and O for off.

WESTINGHOUSE TIMER AND DISTRIBUTER

In this system the primary timer, high tension distributer, coil, and
condenser are contained in a single unit. It is designed to be oper-
ated in a vertical position geared to the cam, or magneto shaft.

The breaker mechanism, which is shown in plan, is quite similar
to that used in other Westinghouse instruments except that it is not
provided with the automatic advance mechanism. The contacts C
and C^ normally are held together under the action of a small coil
spring S; the cam L is mounted loosely on the shaft and is turned
by the pin P, which comes against the stops A or B, according to the
direction of rotation. The condenser K is mounted adjacent to th«

52 IGNITION, TIMING, ETC.

breaker mechanism, these two units being beneath the coil and
the distributer. The condenser, coil and breaker mechanism are en-
closed in a tube of Bakelized Micarta.

The high tension distributer gives a wiping contact. There are two
round brushes pressed apart by a small coil spring, one of the brushes
making contact with the terminal from the coil and the other rubbing
over the six contacts which connect with the wires to the spark plugs.

See details of unit on page 44.

TIMING WITH DELCO ON CADILLAC

As supplied to the 1915 Cadillac, the Delco has an ignition relay
connected in the dry. battery ignition circuit. This breaks the primary
circuit immediately after it has been completed by the auxiliary in the
timer. This action induces a current in the secondary, giving a spark
at the plug. The magnet of the relay attracts an iron bar or "arma-
ture," which in turn actuates the contacts which open and close the
circuit.

The relay is adjusted by means of a toothed wheel at the top of
the magnet, this wheel serving to regulate the distance between the
armature bar and the top pole piece of the magnet. Clockwise rota-
tion increases the distance, while counter clockwise rotation de-
creases it. When the armature is pressed full down the gap is equal
approximately to ordinary book paper.

Ordinarily, the adjustment is best performed while the engine is
running. Turn the notched wheel in a counter clockwise direction
until the motor stops firing, then turn it four or five revolutions in the
opposite direction. If the action of the armature bar is feeble when
the starting button is pushed, it will be found that there is either dirt
between the armature and pole, or that the dry cells are too weak.

As either the battery or magneto systems may require tuning, we
will now take up the magneto system. In timing the magneto spark
first crank the motor until the piston in No. 1 cylinder is on dead
center. Remove the distributer cover, also the rotor, and loosen the
adjusting screw just enough to allow the cam to be turned by hand
after the rotor is fitted. The adjusting screw should not be loosened
enough to allow the cam to turn on the shaft when the motor is
cranked by hand. Replace the rotor and turn it by hand until the
distributing brush is approximately under the terminal marked No. 1
on the distributer cover.

Switch on the battery ignition, hold in on the vibrator button at the
top of the switch on the cowl board and retard the spark lever fully.
Pull the spark lever towards advance position and note the point on
the sector at which the relay starts to vibrate. If the cam is properly
set the relay will start to vibrate just as the spark lever reaches the

IGNITION, TIMING, ETC. 53

battery center marked "Bat." C. If the relay starts to vibrate before
the spark lever reaches battery center it will be necessary to rotate
the cam slightly in a counter clockwise direction to correct the adjust-
ment. If the relay does not start to vibrate until after the battery
center on the sector is passed it will be necessary to rotate the cam
slightly in a clockwise direction. — "Automobile."

FIXED SPARK

In some motors a compromise between the advance and retard is
made, so that the breaker box is held rigid without connection with
either manual or automatic control. This does not give the best re-
sults, since the spark is overly advanced at low speeds and too far
retarded at high because of the varying rapidity of the rate of burning
of the mixture at the two extremes of speed. This results in a loss
of power, flexibility and fuel where there is much variation in the
speed of a motor, as in the case of automobiles. With marine en-
gines, in which the speed is more nearly constant, the bad effects of a
fixed spark are not so noticeable.

EFFECT OF PLUG LOCATION

A number of tests in regard to the effect of plug location on the
power output have been made recently by C. F. D. Marshall on a six-
cylinder motor —

(1) With single plugs over the inlet valves;

(2) With double plugs connected in series, giving two simulta-

neous sparks over each valve;

(3) With single plugs over the exhaust valves.

The results gave an increase of from Ij^ per cent to 2j^ per cent
over the single plugs with double ignition. With the plugs over the
exhaust valves an increase of approximately V/2 per cent was had
over the results obtained with the plugs over the inlet. The advan-
tages gained by the plug over the exhaust valve were greater at high
speed than at low. This engine was of the "L" type, having the valves
all on one side.

In tests on a "T" head motor with the exhaust and inlet valves on
opposite sides of the cylinder, D. K. Clark found that the increase due
to double ignition was from 10 to 12 per cent.

54 IGNITION, TIMING, ETC.

PART III

MAGNETO PRINCIPLES— MAKE AND BREAK

SYSTEM

APPLICATION OF MAKE AND BREAK SYSTEM TO

AUTOMOBILES

THE MAGNETO SYSTEM

The next of the divisions into which we separate the sys-
tems of electrical ignition is the magneto method, and this
can be subdivided into two sections, comprising the low ten-
sion and high tension systems. In dealing with ignition by
dry batteries and accumulators, it will be remembered that we
showed that the spark inside the cylinder can be obtained
from a low tension current transformed into a high tension
current. It is exactly the same with magneto ignition. We
may use either a low or a high tension current, but, as in the
case of ignition with dry batteries or accumulators, whenever
the high tension ignition is used we must have a low tension
current to induce it in an induction coil.

In both systems of magneto ignition the low tension cur-
rent is generated in the same way, the appliances for this
differing principally in constructional details and in the method
of wiring up, and the high tension system, as far as magneto
methods go, in that provision is made to cause the low ten-
sion current generated in the machine to induce a high tension

IGNITION, TIMING, ETC. 55

current. For this purpose an induction coil, either separately
or incorporated in the machine, becomes necessary.
Low Tension Magneto Ignition.

This being understood, it will be well to deal first with
the low tension magneto. That once being thoroughly com-
prehended, the apparent complication of the high tension sys-
tem will become quite simple. The principle on which the
method is founded lies in the fact that if a coil of insulated
wire be revolved between the ends of a magnet, the magnetic
influence will so act as to cause a current of electricity to flow
through the coil, this being of low tension, and being of a
nature suitable for ignition either on the low tension system
inside the cylinder or to induce a high tension current in some
form of induction coil.

The diagram, Fig, 17, shows the permanent magnets used
in a magneto. They are of highly magnetized hardened steel.

PIO. II.— THE tlACNETS

OF A UAGNETO

MACHINE.

and are generally arranged in pairs, three sets of pairs being
used. These are shown at A, B and C. The efficiency of the
machine depends in a large measure on the extent to which
the horseshoe magnets A, B and C are magnetized. The ar-
rangement of the magnets in horseshoe form is the most con-
venient for the purpose of getting the coil, which we wish to
revolve, well surrounded by the magnet ends, which are for
convenience provided with two soft cast-iron pieces D and E
in close metallic contact with the ends of the magnets and

56 IGNITION, TIMING, ETC.

forming a kind of tunnel inside which the coit or armature
will revolve. These two pieces are termed the field pieces
and are often spoken of jointly as the magnetic field.

If a soft iron core of a cross section of the shape shown in
Fig. i8 is taken and a winding of insulated copper wire is

FIG- It.— THE COKE.

wound around it as shown in Fig. 19, we shall have a coil
which is of a convenient shape to be revolved inside the ends
of the magnets ; that is to say, it will occupy a position within
the magjnetic field. The ohject of having this coil revolving
is to cause the magnetic influence, or the lines of magnetic '
force, as they are termed, of the magnets to pass through the

FIG i» — THE ARMATURE.
A. Arnilure ipindle.

C' Cia "?oMd' core""""""

coil alternately from different directions. This core around
which we wind the insulated copper wire is known as the
armature.

Fig. 20 is a diagram of the ends of the magnets, and a cross
section of the armature in position. AC is the armature core,
and C is the winding of insulated wire around it. F and M
are the field magnets or permanent magnets, and the south
pole of these is at S, the north pole being at N. What effect
the position of the armature with its coil, inside the magnetic
field will have on it, in an electrical sense, we will next en-
deavor to explain as simply as possible.

In describing the soft iron core of an induction coil, we

IGNITION, TIMING, ETC.

showed that, when a current of electricity was passed along 3
winding of insulated wire around the core, the latter became
fpr the time magnetized. A reversal of this idea may be re-
garded, for the sake of argument, as what takes place in the
case of the magneto. Here there is a soft iron core and the
winding of insulated wire around it. If, now, we can make
this soft iron core a magnet, we can, in a certain manner, in-
duce a current of electricity in the winding around it, but this

JIG. 9o.— LINES OF FORCE PASSING

THROUGH THE CORE OF THE

ROTATING ARMATURE.

depends on the fact that, to get any results from the induced
current in the winding, we must keep reversing the direction
of the polarity of the core or armature C. In the case of the
soft iron core of an induction coil the polarity, that is to say,
whether the north pole shall lie at one end or the other, is de-
termined by the direction in which the wire is wound around
the core, and is always the same, there being no practical value
or advantage in altering the polarity of the core; but in the
present case, in order to get an inductive effect, we may re-

58 IGNITION. TIMING, ETC.

verse the polarity of the core, or we may cause it to intermit-
tently become magnetized, and this can be done by revolving
it between the field pieces. The magnet acts on the soft iron
core or armature A C, giving it a magnetic pull which is
apparent to the touch, if the armature is allowed to move
freely towards the field which is trying to attract it. This
it can do when the bearings which hold it centrally are dis-
mantled. This force is represented in our diagram by lines,
these lines indicating the direction in which the force acts.

The direction of these lines shows us that the magnetic
force is similar to electrical force in that it will always try
10 act in a direction in which there is the greatest body of
metal capable of being magnetized interposed between the

two field pieces of the magnets. With the core placed in
the position shown in Fig. 20 it will be seen that the lines
of force are acting as indicated by the dotted lines; that is
to say, the magnetic force is acting straight through the center
of the armature, and thence through the winding of the coil.
Supposing now we rotate the core in the direction of the ar-
row until it assumes the position shown in Fig, 21, it will be
seen that the lines of force have gradually changed their di-
rection. They are still flowing through the greatest body of
metal of the core, but they cannot get across in such a direct
manner, the direction of the lines of force being indicated by
the dotted lines. In fact, there is a kind of leakage, some of
the lines of force flowing across between the fields without

IGNITION, TIMING, ETC.

passing through the armature core, as indicated by the two
separate dotted lines.

If the armature is rotated a little further to the position
shown in Fig. 22, it will be seen that the lines of force flow
across the bulk of metal which forms the sides of the H sec-
tion of the armature, and do not pass through the center of
the armature at all. That is to say, they are not passing
through the center of the coil of insulated wire, so^that, in
fact, stoppage of any magnetic effect on the core has been
accomplished by the mere rotation of the core for one-quarter
of a revolution in the field. If we rotate the armature another

FIG. 22.
LINES OF FORCE PASSING
DIRECTLY THROUGH THE

Ends of the armature
from north to south

POLE.

quarter of a revolution in the same direction, it will assume
exactly the same position as shown in Fig. 20, but with this
important difference, that that part of the armature which
was close to the south pole of the magnets now finds itself
close to the north pole; so that the direction of the lines of
force have been first taken altogether away from the center
of the core and then completel}^ reversed relatively to the core
itself. It is evident, therefore, that the armature is changing
its polarity once every revolution in the field, and it is this
constant change of direction of the lines of force through the
core that induces the current in the winding around the arma-
ture, which current we make use of for ignition purposes.

60 IGNITION, TIMING, ETC.

As the armature A C wound with the copper conductors
or coil rotates between the two poles of the magnet N S it
cuts through the lines of force or magnetism which pass
from one pole to the other, and as a result a current is in-
duced in the coil of the armature. When the armature rotates
through the position as in Fig. 22, it will be seen that the
conductors are cutting the maximum amount of lines of force,
and, therefore, this is the point at which the current is at
its maximum value. As it continues to rotate the current
value gradually decreases, and after a quarter revolution
(when it is in the position as shown in Fig. 20) when its con-
ductors are, as it were, slipping along the lines of force,
and not cutting any, its value is nil. Then it again
gradually grows to a maximum in the reversed direction
(when the armature is again in position as shown at Fig. 22)
and as before, falls to zero, and so on, rising to a maximum
and falling to zero twice in every revolution of the armature.

But something else has also been done by this reversal, for
it will be found that we have changed the direction of the elec-
trical current flowing through the winding; thus we have an
alternating current in the wire. If we were to connect the
two ends of the wiring C round the armature, and to rotate
the latter at a good speed, we should not get a constant flow
of electricity through the wiring, but an intermittent one, that
is to say, the voltage of the current would start from zero
and gradually rise as the armature revolved and then as rap-
idly fall. Two of these, which we may call waves of current,
take place during each revolution of the armature, and if
we break contact in the winding around the armature at the
time when the electrical wave is at the highest voltage, we
shall be able to get a spark.

It is the object of the low tension magneto system to lead
this current generated in the armature winding to the inside
of the cylinder and to break the contact there, and if that
can be done an efficient spark for ignition purposes is pro-
duced.

A Simple Form of Magneto— A very simple low tension

IGNITION, TIMING, ETC. 61

magneto system is shown in diagrammatic form in Fig. 23.
One half of the magneto has been cut away in order to show
the armature A lying adjacent to the field B. The coil of
insulated wire around the armature is shown at C, while D is
the armature spindle upon which it revolves in bearings fixed
to either end of the field pieces, the shaft being driven at one
end by a gear wheel which causes it to revolve at some speed
relative to the engine speed. It generally runs at half the
speed, but, in the case of multi-cylindered engines, it becomes
necessary that it should run at such a speed as will give a
diversion of the lines of force at least once every time a cylin-

VIG. le-DIAGRAH OF A MAGNETO.

der has to be fired. One end of the winding of the coil C is di-
rectly and metallically connected to the armature shaft, which,
of course, grounds it. The other end is brought out and at-
tached to an insulated ring E, which is fixed to some part
of the armature or its shaft and revolves with it, but has no
metallic connection with it. On the outside edge of this
ring, and pressing down upon it, is a carbon brush or wiper

F, contained in a tubular case and pressed down by the spring

G. The casing which holds this carbon brush or wiper is
suitably insulated from any metallic part of the machine, and
carries a screw terminal H. It is from this terminal that the
current is taken off by means of the insulated wire J and con-
veyed to the mechanical contact breaker inside th« engine
cylinder.

62 IGNITION, TIMING, ETC.

The Low Tension Igniter — ^The contact breaker inside the
cylinder for use with this type oi magneto is arranged in a
variety of difEerent ways, according to the ideas of different
designers. Its object is first to keep the circuit open, but just
before the armature reaches the position shown in Fig. 26
to make contact, and then suddenly break it when the arma-
ture is in the position shown. If contact were made all the
time there would be no induction set up in the coil, as may
be easily understood by the fact that if we ground the wind-
ing to the magneto we stop its operation for sparking pur-
poses. Another point is that in the case of multiple cylinder
engines it is necessary that only one contact breaker should
be making contact at the same time.

In Fig. 24 is shown one arrangement, by means of which
contact can be made and broken inside the cylinder. A is

A. Criinder.
CCi. Isniler plui.
H. RoekiBg ipindle.

Hi' Coaica] joio'l.

L. I^er DD H.

M, M, Tappei roil.

P. Sprinl.

R. SprioB.

S, Thimble avct ipri

T, CoUii.

U, Cam shaft.

the cylinder in section, so as to show that part of the contact
breaker which is inside it, as well as that part which is out-
side it. Through the wall of the cylinder A passes an insulated
plug C, having at its outside end a terminal and terminating
inside of a cylindrical piece Ci of steel. This cylindrical piece
is insulated from the cylinder by means of the insulation of the

IGNITION, TIMING, ETC. 63

plug. The low tension wire from the magneto leads the low
tension current to the plug C. H is a rocking spindle, which
also passes through the walls of the cylinder. Inside at Hg it
is provided with a tapered ground joint, so that the pressure
inside the cylinder will always keep it gas-tight, yet at the
same time it can rock in the joint. On its end, inside the cylin-
der, it carries a lever Hi, known as the contact arm. This
lever, as will be seen, is so arranged that it can come up in
contact with the insulated plug Ci. At its end, outside the
cylinder, the rocking spindle H carries a second lever L at
right angles to the lever Hi. A spring P is interposed be-
tween this lever and a pin on the cylinder, and this spring
keeps the lever L pressed down, and therefore tends to force
the lever Hi in contact with the insulated plug Ci. This is
the normal position of this lever, except under conditions
which we shall next describe.

On the engine camshaft U, which is shown in end view, is
mounted an ignition cam Y. The shape of this cam is of
importance to the operation of the appliance. There is a
tappet rod M which passes through the crank case, and at
its end carries a hardened shoe Mi. It also has a collar T,
and is inclosed partially in a thimble S, which is screwed down
on to the crank case. Between the collar T and the top of
the thimble S is interposed a compression spring R. Obvi-
ously this spring will keep the shoe Ml down into contact
with the outside of the cam Y. The top of the tappet rod M
is arranged to come just under the end of the lever L. The
configuration of the cam Y is such as to give this tappet rod
a variable movement up and down. In the position shown the
shoe is on that portion of the cam which is concentric with
the circle Z, which may be described as the lowest part of the
cam. In this position it will be seen that the top of the tappet
rod M is not in contact with the end of the lever L, so that
the spring P can draw the contact arm Hi into close contact
with the plug Ci. It is just at this position that contact is
made, and is about to be broken. The cam Y rotates in the
direction indicated by the arrow, so that, after it has rotated

64 IGNITION, TIMING, ETC.

a little farther than the position shown, the shoe Mi is sud-
denly forced up by the projection W on the cam. As it rises
it will also knock the end of the lever L up, and there-
fore will move Hi out of contact with Ci, thus breaking con-
tact and firing the charge in the cylinder. The cam contin-
ues to rotate, and the shoe gradually drops again as it comes
back upon the lower part of the projection W until it reaches
that part of the cam V, which is concentric with the shaft,
but of large enough diameter to keep the shoe Mi lifted high
enough to keep the lever L lifted up and Hi out of contact
with Ci. During the rotation of the cam the contact breaker
is held in this position until it reaches that part of the cam
again when the tappet rod M drops, and allows contact to
be made, only to be again broken by the projection W on the
cam.

The Fiat Igniter — The illustration (Fig. 24) is purely dia-
grammatic. A drawing of an actual low tension igniter on
practically the same lines is shown at Fig. 25, and the same
index letters have been applied to this as in the case of the
diagrammatic view, so that the reader can refer from one
illustration to the other in order to grasp the details of the
arrangement. In Fig. 25, the cam operating the rod M is not
shown. It is, however, in construction substantially as illus-
trated in Fig. 24.

The low tension current is led by the insulated wire F to
an igniter or plug Gi, made of steel, and passing through the
walls of the cylinder. It is insulated from the latter by the
two cone insulating collars C and C. By means of the nut
E, and the two washers D and D, these two coned insulators
can be drawn towards each other, forming a gas-tight joint.

The plug Gi is thus entirely insulated from the cylinder
wall, but it is in metallic connection with the insulated coil
around the armature of the magneto, through the medium
of the insulated wire F. It is necessary in order to com-
plete the circuit for the low tension current that some means
should be provided for putting the igniter plug Gi into con-
tact with j^round, and at the same time providing a means

IGNITION, TIMING, ETC.

B. Bo» bored ib t
C,C. Composition i
I>,I>,A,be..0iand

E, Nuts for pulling

high tension

F. Wire from magn
G,Gi, Igniter, the

.""^vlrVa
H, Rocking shaft.
H>, Contact arm fo

H. and the e
H>. Conical facing

piece J.
M], Tapered poriio
Hj, Screwed portio
J. Bearing piece, i
K, Light spring, k

J.e ignricr, G, Gi.

sulating blocks, tapered *l(i form air

brasg washers.

up insulailng blocks C, C, and alto
cable F to the igniter G, Gi.

end Gi beinn Urgcr in diameter tha

light joiDii.

[or attaching tbi

the end O. Ihui
ulating block 1 up

ming portion of H. When contact
nd Gi of the igniter, a .park oeenis

s broken betwe«a
eatlnf in beatiar

»hich is formed the seating tor H
eping Hi up to its seating in J.

L. Atluating lever
Li, Small boss or i

cing, against which the lappet ot lif

a Hi and Oi [«

ine rod H acts.

Li, Bois of actuating lever L.

M, Tappet Tod.

N, NbIs. screwed on to the end H* of H, holding the boss ot levei L in

o?'wh^ch'"ihe a^ju's°tment' of"ihe angle between L and H tan be

t>, Spring attached to the actuating lever L. lending to keep Hi aad Ctjs

Q, Boll holes, for atlachiny the ignition device to cyliadcf;

m IGNITION, TIMING, ETC,

for breaking this contact at the moment when firing in the
cylinder is to take place.

This is done by means of the arm Hi. This arm is fixed
at the end of an oscillating spindle H, which passes through
a bearing J in the walls of the cylinder. The outer end of
this oscillating spindle is provided with a second lever L,
this lever bemg on the outside of the cylinder. It will be
seen that if L is lifted or depressed Hi will also be moved
inside the cylinder. The top of the lever Hi is brought
into contact with the end of the plug Gi, by means of the
spring P, at the end of the lever L. This spring holds L
down and causes Hi to keep in contact with Gi. The low
tension current from the magneto can then flow through
Gi, through the lever H, and to earth through the cylinder
walls. M is a vertical tappet rod, its bottom end being in
contact with the edge of a cam on the engine camshaft.

What happens so far as the mechanical break goes is
this: The cam normally keeps M in contact with the boss
Li, on the lever L, and keeps this lever lifted just enough

FIG. 26.

to keep Hi out of contact with Gi. Just before it becomes
necessary to fire the cylinder, however, the cam allows M
to drop out of contact with Li, the spring P draws Li down
and causes Hi to be pressed in firm contact with Gi. This
takes place just at about the time when the armature is in
the position shown in Fig. 21 relatively to the field. As the
piston comes to within a very little distance of the top of the
stroke and just when the relative position of armature is as
shown in Fig. 26 (that is to say, the lines of force have just
been diverted, and the edge J of the armature has just left
the edge K of the field) the cam suddenly forces the tappet
rod M upward; thus M strikes L and lifts it.

IGNITION, TIMING, ETC. 67

PART IV

HIGH-TENSION MAGNETOS

Types of High-Tension Magnetos. To overcome the mechanical
complications of the low-tension make-and-break system, the high-
tension magneto system has been almost universally adopted on motor
cars. Depending on the method by which the low-tension primary
current is stepped up into the high-tension current, these magnetos
may be classified into three general groups.

(1) Dynamo Type. The dynamo type of magneto may be either
of the alternating or direct current type and is generally driven from
the motor by a belt or friction pulley in such a way that there is no
definite relation between the rotation of the armature and the position
of the crank throws.

(2) Transformer Type. The transformer type is geared to the
motor so that the armature position has a definite relation to the
cranks. A primary circuit breaker is incorporated in the magneto that
breaks the primary circuit at the end of the compression stroke. The
low-tension primary current generated by the magneto is led to a non-
vibrating spark coil. Only a single spark is produced at the time
that the circuit breaker opens. This magneto is always of the alter-
nating current type, with two current impulses per revolution.

(3) True High-Ten?iion Type. In this type of magneto the arma-
ture generates high-tension current directly without the use of a spark
coil. The secondary and prin^ary windings are both on the revolving
armature, the high-tension current thus produced being led to the
distributer mounted on the magneto.

Direct Current Magnetos. The direct current dynamo is commonly
used on stationary engines. As the speed of the device is compara-
tively high, it is driven with a belt or friction pulley from the fly-
wheel, a governor being sometimes used to keep the voltage at a
constant value. It can be used for charging storage cells. A separate
circuit breaker or timer must be used since the speed of the armature
does not correspond directly with that of the crankshaft. In sub-
stituting this type of current generator for a battery of dry cells or
storage batteries it is only necessary to disconnect the batteries and
reconnect the same two wires with the dynamo.

A vibrator spark coil is generally necessary for each individual

68 IGNITION, TIMING, ETC,

cylinder unless a distributer is used. The speed of the dynamo must
be very carefully regulated to prevent burning out the coils at a high
speed, since this type increases the voltage with every increase in
speed. A centrifugal governor mounted on the end of the dynamo
shaft which acts by bringing the friction pulley into or out of contact
with the flywheel of the motor, depending upon whether the speed is
too high or too low.

Alternating Current Dynamos. Alternating current dynamos may
be either belt, friction, or gear driven from the motor, and in one or
two cases at least are directly connected with the crankshaft. This
type is not installed with reference to the crankshaft position and
therefore must be provided with a separate timer. No governor is
necessary with the alternating current type, as the generator is to
some extent self-regulating because of the increasing self-induction at
the higher frequencies. This class cannot be used for charging
storage batteries. It is placed in the circuit in the same way as the
direct current dynamo. Vibrator coils and a timer are used.

In the Ford car a series of magnets placed in the flywheel, and
revolving with it, pass a series of stationary coils mounted on a spider.
The magnetism threading through the coils, together with the speed
of the magnets, generates a low-tension primary current. The mag-
neto is very simple as there are no brushes or contacts, the current
being led directly from the stationary coils. Owing to the compara-
tively high peripheral velocity of the magnets, current is produced at
low rotative speeds.

Transformer Type. In this type the primary circuit breaker and
secondary distributer are mounted directly in the magneto and in a
particular relation to the armature shaft. Only a low-tension current
is produced in the magneto, the voltage being stepped up by an inde-
pendent spark coil. Since the timer is mounted on the armature shaft
it is absolutely necessary to time the armature or to gear it to the
motor in such a way that the piston and armature have a certain
definite relation with one another. It cannot be belt or friction driven.

The high-tension spark coil receives the primary current, from the
magneto armature and through the circuit breaker in such a way that
a single spark is produced at each opening of the breaker. This spark
occurs so that the gas in the cylinder is ignited at the end of the
compression stroke.

When more than one cylinder is used the magneto is provided with
a high-tension distributer, which distributes the current to the cylin-
ders in correct firing order. The distributer is mounted in the upper
part of the magneto and is geared to the armature shaft, so that in a
four-cylinder motor the distributer travels at camshaft speed. With
four cylinders the armature travels at crankshaft speed, and with

IGNITION, TIMING, ETC, 69

six cylinders at one and one-half crankshaft speed, the distributer at
all timps and cases turning at camshaft speed. A high-tension lead
from the spark coil connects with the revolving arm in the distributer.

Common examples of the transformer type are the Connecticut,
Remy, Splitdorf, and the old type Eiseman. At the present time,
however, all of these companies with the exception of one also pro-
duce true high-tension type.

True High-Tension Type. This is by far the most common type
of high-tension magneto for the reason that it is compact and self-
contained and is by far the simplest to wire up. It requires no coil
except that used for a battery auxiliary.

In the true high-tension type there are two windings on the arma-
ture, a primary and secondary, the secondary like the secondary of
a spark coil, being composed of thousands of turns of very fine wire.
The primary is of coarse wire and is interrupted by a circuit breaker.
A spark is produced at every break in the primary circuit. The inner
end of the primary is grounded to the frame of the magneto through
the armature, while the remaining end of the primary is connected
to the inner end of the secondary, the connection to the circuit breaker
also being made at this point.

The outer end of the secondary wire is connected to the high-tension
distributer through a slip ring mounted on the armature shaft. The
distributer is driven from the armature shaft by a gear so that it
revolves at camshaft speed. This type is geared to the motor in a
definite relation as in the case of the transformer type, the armature
shaft running at exactly crankshaft speed in the two and four cylinder
types, and one and one-half crankshaft speed in the case of the six-
cylinder motor. The primary circuit breaker is then so placed that it
opens when the piston is very near to the end of the compression
stroke, thus igniting the charge on the upper dead center.

Since two sparks are produced, per revolution of the armature
shaft, no distributer is needed with the two-cylinder motor, the con-
nections in this case being led directly from the high-tension slip ring.
A lead from each spark plug is brought to the distributer so that as
the distributer arm revolves it comes into contact with the terminal
of each plug in the correct firing order. A low-tension lead runs
from the breaker box to the cutout switch on the dash, so that when
the switch is closed the primary winding of the armature is short-
circuited, thus stopping the generation of current.

Advance and retard in this type of magneto is had by shifting the
casing of the circuit breaker back and forth so that the primary cur-
rent is interrupted earlier or later in the revolution. In some types
the advance and retard is performed automatically by means of a
centrifugal governor.

70 IGNITION, TIMING, ETC.

As in the battery coil, a condenser is connected across the terminals
of the circuit breaker so as to increase the rapidity of the break in
the primary circuit.

TYPICAL TRUE HIGH-TENSION TYPE

In Fig. 1 is shown a perspective view of a typical true high-tension
type magneto, the magnets and pole pieces being omitted for the sake
of simplifying the drawing. The armature lies between the pole
pieces and magnets in the same manner as in the elementary magneto
previously described. At the right of the perspective is a section
through the armature showing the actual arrangements of the two
windings on the armature, the winding in the perspective being simply
diagrammatic. The shuttle armature of "H" form is indicated by H
in both views.

This armature is connected to the shafts D and N by two brass
end plates similar to F. The body of the armature in general is built
up of laminated sheet steel to prevent the generation of useless eddy
currents and to increase the strength of the magnetic flux through
the armature winding. The primary winding is grounded to the arma-
ture core at the point Y, and is then given several turns around the
iron core K, the outer end of the winding being connected to the con-
nection bolt 2B at the point M. It should be remembered that the
primary winding consists of a few turns of heavy wire.

From the point M, the secondary winding consisting of thousands
of turns of very fine wire is started. The inner end of the secondary
being connected to M makes the secondary simply a continuation of
the primary winding. This is not shown in the perspective as it would
greatly complicate the drawing, but the true arrangement can be
easily seen from the section at the right in which J is the primary and
L is the secondary, an insulating strip G separating the two parts
of the circuit. The entire series of winding is insulated from the core
by the insulation indicated by the heavy black lines. A band I binds
the wire against the centrifugal force that tends to burst the winding
when the armature is rotating.

Primary current is carried to the circuit breaker jaw 2 A and the
switch 2D, through the insulated connection bolt 2B, which is insulated
from the shaft N by the black insulation shown. The outer end of the
high-tension winding is carried to the high-tension collector ring E
by means of the insulated pin 2E. A brush at 2B carries primary cur-
rent to the grounding switch 2D, which when closed grounds the
primary and stops the generation of high-tension current. This
switch is generally placed on the dash of the automobile.

A primary circuit breaker jaw 2A, which is connected to the primary
winding, and is insulated from the shaft, revolves with the shaft and

IGNITION, TIMING, ETC. 71

makes xntermittenl contact with the jaw X at the point Z. The jaw
X is grounded to the shaft and revolves with it so that the two con-
tact points are always opposite to one another. Every time that
s made between the two jaws at Z, the primary circuit is

completed through the ground. The opening and closing of the jaws
is accomplished by means of a stationary cam which acts on the cam
roller 20, the contact between the cam and roller being made twice
per revolution.

When the contact is broken, the primary circuit is opened, which
gives a heavy current impulse to the secondary winding, this impulse
resulting in a spark at the plugs. The spark therefore occurs at the

72 IGNITION, TIMING, ETC,

instant when the breaker opens the circuit. The cam that opens the
jaws is usually made of fiber board, and is located in che breaker
housing that covers the mechanism. In some types of magnetos the
cam revolves against stationary breaker jaws, but this is merely a
matter of detail and in no way affects the principle of operation. The
contact points Z are either of platinum-iridium or of metallic tungsten.
By shifting the breaker housing to the right or left by means of
lever, the breaker jaws open sooner or later in the revolution of the
armature, causing the advance or retard of the spark. This is similar
to the effect produced by rocking the housing of the battery timer.
Details of several types of breaker mechanism will be shown in the
following chapters.

A distributer board is shown in the perspective which contains the
metal sectors S-S2-S3-S4, each of these sectors being connected to the
wires 1-2-3-4, which lead to the spark plugs in the cylinders. These
sectors receive high-tension current from the brush T contained in
the revolving distributer arm V, each sector being charged in turn as
the arm revolves. The distributer board is of course built of some
high insulating material such as hard rubber or Bakelite, and is shown
as if it were transparent so that the armature parts may be clearly
seen. A spring U forces the brush into contact with the sectors and
also electrically connects the brush with the high-tension current com-
ing through the connector shaft V and the second high-tension brush
holder Q.

High-tension current from the secondary winding passes from the
connection 2E to the collector ring E, this ring being thoroughly
insulated from the frame by the hard rubber bushing D, shown in
solid black. The high-tension current is taken from the collector
ring by the brush C, through the insulating support B, and to the ter-
minal A. From A the current passes through the bridge P to the
distributer arm U through the brush holder Q and the connector V.

The current passes to the plugs through 1-2-3-4, and the plugs
being grounded, the current returns through the grounded frame to
the armature coil through the arms X and 2A at the moment of
contact.

The distributer arm V is driven through a gear (not shown) from
a pinion on the armature shaft N. With four-cylinder motors the
distributer travels at camshaft speed or at one-half of the armature
speed, since the armature of a four-cylinder motor always travels at
crankshaft speed.

With a six-cylinder motor, the armature travels at one and one-
half times the crankshaft speed, and as the distributer still travels at
camshaft speed, the gear ratio between the armature and distributer is
3 to 1. Single-cylinder and two-cylinder magnetos have no distribu-

IGNITION, TIMING, ETC.

ter, the current being taken directly from the collector ring E. In a
type of magneto recently developed for small four-cylinder cycle cars,
there is no distributer in the ordinary sense of the word, the distribu-
tion being accomplished by two split collector rings. (See Bosch
magneto.)

The following table will give the armature speeds for different
numbers of cylinders. It should be remembered that in all cases the
distributer runs at camshaft speed, and that there are as many dis-
tributer sectors as there are cylinders:

(Four-Cycle Type Motors Only)

No. Cylinders

Distributer
Gear Ratio

Armature Speed

Note

One

No Dist.

Crankshaft Speed

Two

No Dist.

Crankshaft Speed

Three

IJ^tol

% Crankshaft
Speed

Four

2tol

Crankshaft Speed

♦Five

No. Dist.

5/4 times Crank-

Rotary Motor

shaft Speed

Dist. on Motor

Six

3tol

lJ/2 times Crank-
shaft Speed

♦Seven

No. Dist.

l^^ times Crank-

Rotary Motor

shaft Speed

Dist. on Motor

Eight

4tol

2 times Crank-

shaft Speed

Single Magneto

Eight

2tol

Crankshaft Speed

Two Magnetos
(each4cyls.)

*Nine

No. Dist.

9/4 times Crank-

Rotary Motor

shaft Speed

Dist. on Motor

tTen

5tol

lYz times Crank-

shaft Speed

Radial Aero Type

Twelve

6tol

3 times Crank-

One Magneto for

shaft Speed

Twelve Cyls.

Twelve

3tol

iy2 times Crank-

Two Magnetos

shaft Speed

(each for 6 cyls.)

* Denotes the arrangement used with rotary engines in which no
magneto distributer is used, the plugs of the rotating cylinders coming
into contact with a stationary brush held by the magneto. The mag-
neto is of the single-cylinder type.

t Denotes a radial arrangement of cylinders, all cylinders being sta-
tionary. Seldom used.

74 IGNITION, TIMING, ETC.

TYPICAL TRANSFORMER TYPE MAGNETO

The transformer type of magneto contains a circuit breaker and
distributer as an integral part. It must be driven positively at a defi-
nite speed, the exact speed in relation to the crank shaft being deter-
mined by the number of cylinders in the motor, or the cycle of the
motor. A single primary winding Z of heavy insulated wire is placed
on the armature, and the inner end is grounded at the point G-3, thus
doing away with the necessity of a return wire. The breaker housing
L in reality comes directly in front of the armature, but in the drawing
it has been placed below so that the armature construction can be
more readily seen. The pole shoes P of the magnet embrace the arma-
ture in the usual way. A lead from the primary winding connects
with a connector bolt G, which passes through the hollow shaft U,
the bolt G being insulated from the shaft by the insulating tube. A
copper brush E pressed on the end of G by a small spring in the rear,
collects the current from the armature and delivers it to the circuit
wire terminal 6, from which it flows to the coil terminal T-3. From
the terminal T-3 the current passes to the switch contact 1^, across
the switch blade N, where the current splits, part going through the
coil and part flowing back to the circuit breaker through 2^, terminal
T-2, and ends at the breaker contact A. A platinum-pointed contact
screw M is adjustable in the insulated holder A. It should be noted
that the brush E is insulated from the frame by the rubber bushing F.

A rocking breaker arm B swings on the pivot I, to which it is
grounded to the frame of the magneto, this arm being swung back
and forth by the cam H, which is mounted on the armature shaft U.
The cam, rotating periodically, strikes the cam roller K fastened in
the arm, opening and closing the contacts mounted in the ends of A
and B at the point B. When these contacts are closed the armature
circuit is grounded through I to 12, the dotted lines representing the
grounded circuit. A pair of auxiliary contacts, C and D, mounted on
the back of the rocker and on the timer housing, respectively, are for
the purpose of breaking the battery current in the coil.

When the points separate, the current is broken in the primary
circuit of the coil, causing a high tension spark. A small helical
spring, not shown, pulls the arm B and the roller K, so that it is at
all times in contact with the cam H. Since there are two maximum
current impulses per revolution of the armature, the cam H is set so
that the current is broken twice per revolution at the time when the
armature is generating its greatest voltage. The timer housing L
may be rocked back and forth by the spark lever 19, by which the
spark may be advanced or retarded. Rocking the housing causes the
cam H to come into contact, earlier or later, with the roller, thus

IGNITION, TIMING, ETC. 75

causing the spark to occur earlier or later in the revolution. The
battery breaker C-D is grounded at G-2.

The spark coil, condenser, safety spark gap, the terminals T-1, T-2,
T-3, T-4, T-5, and the dash switch are mounted in a wooden box that
is usually mounted on the dashboard of the automobile. The battery

Fig. 2,^TypicBl Tiansfonner Type Magneto.

is connected with the box by T-4 and T-S, usually marked "Bat."
oa the instrument. The terminal T-1, marked "3" on the instrument,
is grounded to the frame of the machine, while cables from T-2 and
T-3, marked "2" and "A," respectively on the instrument, are con-
nected with the stationary breaker contact and with the armature
brush E.
Around the soft iron core T-T' are wound the primary and second-

76 IGNITION, TIMING, ETC.

ary windings as shown. In the case of this particular machine, the
secondary winding consists of 3900 ohms of No. 34 wire, while the
resistance of the primary is only 0.08 ohms, the ratio between the
windings being nearly 40,000 to 1. The usual type of tin foil con-
denser is connected across the primary winding of the wires 9-10 and
8-11, this preventing sparking at the contact points A and B, and
acting so as to increase the volume of the secondary spark.

A safety-spark gap is connected across the high tension terminals
at 16 and 17, the distance between the discharge points being regu-
lated so that the spark will jump across these points when the volt-
age becomes excessive at high speeds or in cases when the secondary
leads become disconnected from the plugs. Limiting the voltage in
this way does away with the danger of puncturing the insulation of
the high tension windings. Usually this gap is about ^ inch wide,
and at speeds above 800 revs, per minute, or with more than 4 cells
there is almost a continuous discharge when the plugs are discon-
nected.

A press button P is used for causing a spark at the plug when the
engine is at rest, or for starting on "compression," as it is called.
With a warm engine, having its cylinders full of mixture, it is very
often possible to start the engine in this way without cranking. The
spark occurs when the contacts P and O are separated, the points
P and O permitting battery current to flow for an instant through
the primary of the coil.

The dash switch is mounted on the front of the coil box and has
two switch positions, "Bat." and "Mag." When starting the switch
indicator is thrown to "Bat.," and when the engine is firing regularly
the switch is thrown to "Mag.," thus cutting the magneto in and
the battery out of service. The normal running should always be
done on the magneto.

In the sketch the switch is shown on the magneto position, in which
the blade N shorts the contacts 1^ and 2^, bringing the armature
current from 6 to the breaker contact A. At the same time the in-
terrupted armature current is led from the switch at 7 to the primary
of the coil at 8, and from the other end of the coil at 9 to the ground
at terminal T-1, and thence back to the armature, completing the
circuit.

End 17 of the secondary coil is grounded at G, this connection usu-
ally being to the lead 9 T-1, as this saves one lead from the box to the
frame. The other end of the high tension wire 16 leads through 15
to the axis 18 of the high tension distributer. From the coil box
there are the following cables to connect:

2 wires from box to battery (low tension).
2 wires from box to magneto (low tension).

IGNITION, TIMING, ETC. 77

1 wire from box to ground (low and high tension).
1 wire from box to distributer (high tension).
4 Wires from distributer to plugs.

The distributer board, shown in cross-hatch lines, is made of insu-
lating material such as hard rubber or Bakelite. In this material are
imbedded four metal sectors, S-1, S-2, S-3 and S-4, spaced at equal
distances around the circle. It must be understood that there are as
many sectors as cylinders, the present example being for a four-
cylinder motor.

High tension current from the secondary of the coil is brought into
the shaft of the rotating distributer arc R through the wire 18-15-16.
As the arm rotates it comes into contact with the sectors in order
and thus connects the high tension current to the spark plugs 1-2-3-4
when contact is made with the segments S-1, S-2, S-3 and S-4, respect-
ively. The distributer thus connects with the plugs in the proper
firing order, while the circuit breaker determines the part of the revo-
lution or the time at which the spark is to occur.

The distributer arm R is driven by a gear on the shaft 18 that
meshes with a pinion on the armature shaft U, the gear ratio always
being such that the distributer arm turns at cam-shaft speed. The
gear ratio between the armature and the distributer varies, however,
with the number of cylinders used.

The relation of the magneto speed to the speed of the motor or
crank-shaft speed depends on the number of cylinders, a single, double
and four-cylinder magneto running at exactly crank-shaft speed,
while a three-cylinder runs at ^ crank-shaft speed and a six-cylinder
at 1J4 crank-shaft. An eight-cylinder will run at twice crank-shaft
speed. It must be understood that these speeds apply only to four-
stroke cycle motors and to shuttle type armatures which give two
sparks per revolution.

Two-stroke cycle motors demand twice the number of sparks per
revolution, and for the same number of cylinders as each cylinder in
this case fires twice as often. For the speeds of any other number
of cylinders see the table under "Typical True High Tension Mag-
netos." This will also apply to the transformer type.

A type of transformer magneto that was designed by the author
is shown by Fig. 3. In this magneto the transformer coil was en-
closed in a metal case and placed in the opening between the mag-
nets, thus making the magneto and coil one compact unit and avoid-
ing the use of many wires and cables that are in evidence when the
coil is mounted on the dashboard. In the diagram the coil, armature,
condenser and circuit breaker are shown approximately in their cor-
rect relative positions.

A shuttle armature P is used, one end of the primary winding bein^^
grounded to the armature, while the other end is connected with m-

IGNITION, TIMING, ETC.

sulated bolt D with the lead K. The heavy line indicates the insula-
tion. A brush B held in an insulating brush-holder A presses on the
enlarged head C of the connector bolt D, thus leading the armature
current to the external circuit from 11. One lead 10-11 carries the
armature current to the primary coil 10-7. Instead of depending on
the armature ground connecting with the magneto frame through
the shaft and bearings, a separate grounding brush L, held in the
metal holder M, was used, this brush grounding the winding at G-2.

Fig. 3. — Rathbun Transformer Magneto Circuit

This, as far as the diagram goes, was electrically the same as if the
inner end of the winding was connected to the frame, but, mechan-
ically, was much better, as it did not have to depend on a ground
through the varying conditions caused by grease or loose bearings.
N is the shaft.

At 7 the end of the primary is grounded at G and is connected
through the frame at 18, and to brush at 17, all dotted lines repre-
senting the grounded circuit. A tinfoil condenser 9-8 was connected
across the coil as shown by 9-10 and 7-8. A safety gap 5-6 was con-
nected across the secondary winding, the lead 5-0 going to the high
tension distributer arm O. This arm, in rotating, made successive
contact with the sectors leading to the spark plugs 1-2-3-4.

IGNITION. TIMING, ETC.

The other end of the armature circuit lead from the brush Bat. 11
to the interrupter at R through wire 12. This interrupter eoDsisted
of two metal blades G and H. spring tempered, mounted and insu-
lated from each other on the block 19. Two platinum contact points
I and J made normal contact with one another, grounding the arma-
ture current through IS at G-3, and from here along the frame 15-16
and 16-17 back to the other end of the armature winding.

Toad-
just ' the
points, first
clean them
with a line
flat file. Then
reset adjust-
ing screw
"T" so that
the sap is
not more
than .035
inch.

MTTEKf

Fig. 4. — Splitdorf Transformer Type Magneto and Circuit. Trans-
former Coil at the Left of Circuit Diagram. Courtesy of "The Auto-
mobile."

80 IGNITION. TIMING. ETC.

A cam H made of insulating material intermittently passed between
the contact points at G and H, breaking the primary circuit at I-J
twice every revolution and at a time when the voltage of the arma-.
lure was at a maximum. Every break caused a high teasion spark at
the plugs. A ground switch S mounted on the dashboard stopped the
motor firing by shorting the primary winding across 13-14 and to
ground at 6-3.

Leaving the question of the cables to the plugs, the only connec-
tion to be made with this magneto was the lead 12-13 to the switch

Fig. 5. — Connecticut Transtonner Magneto Dissembled.

on the dash, a low tension wire. Very simple when compared to other
transformer type magnetos. The number of leads to the plugs would
be the same with any magneto.

Another magneto in which the transformer coil is carried between
the magnets is shown by Fig. S. This shows the Connecticut mag-
neto in dissembled form, the transformer coil standing at the extreme
right of the cut. As in the case of the magneto just described, there
are four leads to the plugs and only one lead to the grounding switch
on the dash.

IGNITION, TIMING, ETC. 81

The front elevation and circuit diagram of the Splitdorf
transformer type magneto is shown by Fig, 4, in which A, B,
C, and D are terminals for the spark plug connections. The
coil and switch shown at the left in circuit diagram are con-
nected with an auxiliary dry battery which is generally used
in starting the motor. A total advance angle of 17 degrees
is shown in the elevation with the breaker contacts at the
point S.

Mechanical Details.

The Eisemann System — In this system the low tension
current is taken away from the magneto and used to induce

no. pfr- FftONT VIEW OF THE EISEMANN SIAGNETtt
a high tension current in the secondary winding of an induc-
tion coil. This high tension current is then brought back
from the coil to be distributed by a distributer forming part
of the magneto mechanism. There are several types of this
magneto used ; they vary generally in their mechanical de-
tails, but in principle are all practically alike. In the first
place, as regards the armature, this runs on ball bearings in

82 IGNITION. TIMIXG, ETC.

plates affixed to the end of the field pieces, the plates being of
some non-magnetic metal. A front view of the machine is
shown in diagrammatic form in Fig. 29. The magnets are
shown at A and B, and the armature revolves inside between
ihe ends of these, the end of the armature shaft being seen
at C. If we look now at Fig. 30 we shall understand how
the different units of the magneto are built uq. C is the
end of the armature shaft. The latter revolves in ball bear-
ings in the end plates and carries the wheel D; this wheel

FIG. 3C.-THE GEAR WHEELS WHICH

OPERATE THE HIGH TENSION

DISTRIBUTER.

gears with the second wheel E, which is mounted on a second
shaft carried in bearings inside the space formed by the
horse-shoe magnets A, B. The rotation of the magneto ar-
mature will rotate E at half the speed of the shaft. It is
the function of E to act as a high tension distributer in a
manner which we shall describe later. The contact breaker
is mounted on a plate shown in Fig. 29, and consists of a
pivoted arm J which is pivoted at K, and is L shaped. At
its top end it has a small platinum-pointed head L which

IGNITION, TIMING, ETC. 83

comes into contact with the platinum-pointed contact screw
M, capable of adjustment, and to which the current is led
from the primary winding of the magneto armature* A
spring N keeps the pivoted lever J pressed up so that
contact is made between L and M. On the end of the arma-
ture shaft there is a cam O. * (This cam is seen more clearly
in Fig. 30, where it is not confused with the mechanism of
the contact breaker.) Now, at the time that the armature
is just cutting the lines of force in the magnetic field, this
cam comes up against the lever J and knocks it out of con-
tact with the insulated contact screw M, so that the circuit is
broken at this moment.

The current from the low tension winding is taken through
an insulated contact piece C on the end of the armature shaft,
and passes to a carbon spring brush on the cover of the con-
tact breaker, and from there to the platinum screw M of the
contact breaker. This carbon brush is also connected to the
primary winding of the coil. Thus normally the path of the
low tension current is through the contacts of the commutator
to ground, through the cam O and the armature, which is con-
nected to ground by a spring-pushed contact piece, not shown
in our illustration. This is really to insure a thorough con-
tact to ground. At the moment of breaking the contact the
current passes from the carbon brush to the low tension
winding of the induction coil and then to ground.

The high tension current is now generated in the separate
coil, and is returned by means of the insulated wire to the
high tension distributer, also part of the magneto. This is
shown very clearly in Fig. 30. At the end of the shaft, on
which is mounted the wheel E, is mounted a rotating arm
P (Fig. 29). This arm is insulated from the shaft and to it
is conveyed the high tension current from the coil. It is the
object of this rotating arm to distribute in rotation the high
tension current to the different cylinders, which it does in
the following way. The current is led to it by means of a
terminal Y2 on the cover, which is shown in Fig. 31. This
cover encloses the high tension distributer. The two spring

84 IGNITION. TIMING, ETC.

fasteners 2, Z engage in the holes Zi, Zi (Fig. 29). In the
center of the cover, Fig. 31, is shown a spring-pushed con-
tact piece G pressed forward by the spring Gi. This is insu-
lated from the cover, but is in metallic contact with the ter-
minal inside Y2. When the cover is in position, G presses
up against the contact piece Pi <Fig. 29), in the rotating arm.
P, and thus the high tension current is led to P, which re-
volves in front of an insulated disk Q. In this disk are in-
serted four segments R, R, R, R and a spring-pushed wiper
inside the end of the arm P, and pressing against the vulcan-

ite disk Q, makes contact with each of these four insulated
segments in turn. These segments are internally connected
up to terminals Y, Y, Y, Y on the top of the plate S, and
from these terminals wires run to the different sparking plugs.
It will be seen that this arrangement will distribute the cur-
rent alternately to each of four cylinders. In the case of a
two-cylinder engine or a six-cylinder engine there would have
to be two or six respectively of these insulated segments,
and in the case of a six-cylinder engine the ratio of gearing
between the magneto and the engine would have to be
differently arranged.

IGNITION, TIMING. ETC. 85

TWO POINTS OR TWO-SPARK IGNITION

The greatest power will be developed in a cylinder when ignition
and complete combustion occur with the compression pressure at
its greatest or when the volume of gas is the least. All events should
occur instantly. The time required for the flame to spread through
the mixture has made it necessary to have the spark occur before
the end of the compression stroke, to reduce the loss of heat to the
jacket water and therefore loss of power.

The efficiency and output will increase directly with a reduction in
the time required for the combustion, since the longer the burning gas
is in contact with the cylinder walls the greater will be the heat loss.
Again, delayed combustion is never completed when the compression

Fig. 6.— Two Point Igi

space is the smallest, hence the exposed surface is greater, which
again increases the loss.

If the combustion is started at two places simultaneously in such a
way that the points of ignition are spaced with equal amounts of mix-
ture or distances between them, it is evident that less time will be
required for the flame to sweep throughout the volume. This may be
illustrated by the relative times required to burn a candle: (a) lighted
at one end, and (b) lighted at both ends.

To obtain the best results, the points of ignition should be well
separated, as shown by the accompanying Fig. No. 6. In this case
the two plugs are shown over the valves of a "T" head motor located
on opposite sides of the cylinder, so that the flame travel is only half
instead of the entire distance across the head of the cylinder. This is
the reason that "T" head motors give better results with two-point

86 IGNITION, TIMING, ETC.

than the "L" head or the overhead valve motor, proper plug location
in the two latter types being difficult to obtain.

A better arrangement than that illustrated would be to move both
plugs toward the center, so that the distance between the plugs would
be twice the distance between the plugs and the wall of the com-
bustion chamber. In this way the spread of the flame ring would only
be one-quarter of the distance from wall to wall. This is based on
the assumption that the rate of travel from the plugs is equal in all
directions. As shown, the plugs are too close to the wall.

A test on a four-cylindor Chester motor, Z^ x 4^ was run at the
plant of the Automobile Club of America. The engine was arranged
so that single or double sparks could be had by control switch in the
magneto circuit. The motor was of the "T" head type.

The greatest power output with single-point ignition with an ad-
vance of 4.5 degree was 24 horsepower. With two-point ignition the
advance was only 19 degrees for the same output. The maximum
power developed with two-point ignition was 28 horsepower with an
advance of 32 degrees. This is an increase of 4 horsepower, or 16.6
per cent, over single-point ignition.

Another point noted in the favor of two-point ignition was the
fact that a given power was developed at a much lower speed. Should
one plug fail, it will be found that the other is generally operative,
thus adding to the reliability of the equipment.

EFFECT OF ADVANCE AND RETARD

With all alternating current magnetos there is a definite point in
the revolution where the voltage is at a maximum. This point is where
the rate of change in the value of the magnetic flux is a maximum,
which takes place approximately at the armature position shown by
Fig. 7. In this position the magnetic flux is all passing through the
armature core and has reached its greatest value in turning through
the small angular distance E-F. This angle is very small, as will be
seen from the diagram, and if full advantage is to he taken of these
conditions, the circuit breaker must open the primary circuit at this
point. If the breaker opens at any other point in the revolution, ex-
cept at the point directly opposite, the spark will be weakened at a
given speed.

It should be remembered in this connection that the output, or
sparking capacity, of a magneto increases almost directly with the
speed, so that a more intense spark is obtained at high motor speeds
than at low.

With the magnets stationary, and with the breaker box moved for-
ward or backward from the ideal point in advancing or retarding the
spark, it will be evident that the spark is weakened at the extreme

IGNITION, TIMING, ETC,

points, since the breaker jaws open when the winding is generating
a lower voltage. In practice this is exactly what does happen, when
the spark is fully retarded, making starting difficult. When cranking
the motor a very slow magneto speed is had, which, together with
the effect of the retard (always retarded in starting) causes the crank-
ing proposition to be a very difficult one, especially in cold weather
when in addition to a poor mixture you have a cold engine and
stiff oil.

Even with self-starters, the job with an exclusive magneto equip-
ment is often difficult, for when many starts and stops are made, the

Fig. 7. — Showing Effect of Advance land Retard on Generation

of Current.

battery of the self-starter is often nearly exhausted, causing the
starting motor to run very slowly. Under such conditions it is usually
necessary to fall back on the auxiliary battery system, in which the
spark is of the same intensity at all speeds.

During the last few years magnetos have been greatly improved
in respect to the intensity at full retard, and many perform wonder-
fully well when compared with the old models, but even now crank-
ing is still a difficulty in the exclusive magneto system.

With the Eisemann magneto, a special form of tapered pole tips
is used, which are efficient at the lowest speeds and greatest retard.
In the Mea and "Dixie" magnetos the circuit breakers move with
magnets or coils in such a way that the breaker points open in the

88 IGNITION, TIMING, ETC,

same relation to the magnetic field at all positions of advance and
retard. This, of course, results in an equal spark at all positions of
the breaker housing. The K. W. magneto has a spring device which,
in combination with a trigger, causes the inductor to "flop over" very
suddenly at the sparking point at the slowest possible cranking speeds,
thus producing an intense spark in starting. When the magneto is
running under normal conditions the automatic spring is cut out of
service.

AUTOMATIC ADVANCE AND RETARD

There are magnetos in which the advance and retard is effected
automatically by means of a centrifugal governor, the Eisemann
Company making a magneto of this type (Type E M A). When this
type of magneto is used the advance and retard are out of the hands
of the operator, thus giving the correct spark position at all speeds
without his attention. The efficiency and performance of the motor
is greatly affected in manual control by the ignorance or carelessness
of the driver. Overheating and knocking due to an excessively re-
tarded or advanced spark are the common cause of numberless trips
to the repair shop.

METHODS OF ADVANCING MAGNETOS

In addition to the method of rocking the circuit breaker housing
back and forth to vary the timing of the magneto, there are several
other systems that can be and are applied, such as rocking the field
magnets or turning the armature in relation to the angular position
of the magneto driving shaft.

To understand the working of the two latter types of control it is
necessary to bear in mind that the spark is varied in relation to the
piston and crankshaft positions. In other words, the opening of the
circuit breaker occurs at different parts of the revolution to produce
an advanced or retarded spark. Any alteration in the magneto that
will cause the spark to occur at different parts of the crankshaft revo-
lution will cause a change in the timing.

Consider a magneto geared to an engine with the magneto mounted
in a rocking cradle so arranged that the magnets, frame and circuit
breaker can be rocked back and forth as a unit about the center of the
armature shaft. If the magnets and frame are now rocked in a
direction against the rotation of the armature it is evident that the
armature will break across the pole shoes sooner than would be the
case in its former position, since the pole shoes meet the armature
earlier in the revolution. If the circuit breaker is moved directly with
the magneto frame, the breaker points will open the primary circuit

IGNITION, TIMING, ETC. 89

just that amount earlier, causing an advanced spark. Retard is
obtained by movement in the opposite direction.

Since the magnets and breaker move together in this case, the
breaker points always open when the armature is at the same position
in the magnetic field, that is, the strongest part of the field. By
rocking the field and breaker together it is possible to obtain the same
intensity of spark at all positions of advance and retard. This method
is used by the Mea and Dixie magnetos, as well as by several station-
ary engine-type magnetos built by the Sumter Mfg. Co.

Stating the above conditions in the form of a rule, "Any relative
angular change of the field in regard to a given angular position of
the armature will cause a change in the timing." This is true whether
the fields are moved in regard to a certain armature position or
whether the armature is moved in regard to a certain field position.

With the fields and breaker in a fixed position, turning the arma-
ture back and forth on the shaft will cause a change in their relations.
This method is adopted in several makes of magnetos in which the
armature and driving shaft are free to turn a certain amount in rela-
tion. The control of the relative positions is generally had by means
of a spirally slotted sleeve which in being moved laterally back and
forth on the shaft causes a slight relative angular movement between
the armature half and the driving half of the shaft.

This method has all of the disadvantages of the rocking breaker
housing type, since with a stationary breaker housing there is rela-
tive motion between the breaker and the armature position in the field
due to the advance and retard of the cam mounted on the armature
shaft. The cam, of course, moves with the armature.

AUTOMATIC SPARK CONTROL

With some magnetos, notably with the Eisemann high-tension type,
the advance and retard of the spark is performed automatically. This
device when properly set controls the advance to correspond with the
varying motor speeds, advancing the spark at high speeds and retard-
ing it at low. Usually the control is effected by the action of some
type of centrifugal governor in advancing the breaker housing or in
turning the armature in relation to the angular position of the driving
or cam-shaft.

The centrifugal governor of the Eisemann magneto is located in a
housing at the rear or driving end. Two spring controlled weights
actuate a spiral sleeve mounted on the shaft in such a way that the
relative positions of the driving shaft coupling and the armature are
changed when an increase of speed drives the weights outward by
centrifugal force. This is the advance. When the speed is decreased
the governor weight springs return the armature to the retard position.

90 IGNITION, TIMING, ETC,

Another type of automatic advance is that of a European manufac-
turer who advances and retards the armature by a novel form of
magneto coupling. The two halves of the coupling are provided with
several grooves, a steel ball being placed in each groove in such a
manner that the balls normally tend to lie next to the hub of the
coupling. The grooves in the magneto half of the coupling are of
spiral form, while in the driving half they are straight and radially
placed.

When the driving speed is increased, the balls are driven outwardly
by the centrifugal force, this movement resulting in a relative move-
ment between the two halves of the coupling, that is to say, the
movement of the ball in the straight groove also acts against the
sides of the spiral groove so that one half (spiral half) is turned
slightly in advance of the other. Since this half drives the magneto
armature, it is evident that the armature is advanced with an increase
in speed. The circuit breaker housing is stationary at all points in the
advance and retard.

There are several important advantages to be gained with an auto-
matic advance, especially in the case of commercial vehicles where
carelessness in handling the spark is often a case of efficiency loss
and of excessive motor heating and pounding. With a well adjusted
device of the class named, the spark position is always at the right
point for a certain speed and is entirely out of the driver's control.
With pleasure vehicles, the elimination of the spark control adds to
the simplicity of the drive and therefore adds greatly to the pleasure
of motoring.

In some commercial vehicles an ordinary type of magneto is used
in connection with a special centrifugal governor installed by the
builder of the motor. The control lever of this governor rocks the
timer housing back and forth in a manner similar to that in a manually
controlled magneto.

With an automatic timing there is no chance of accident in cranking
the motor, since the spark is always fully retarded with the motor at
rest. In this way the chances of "kick-back" are greatly reduced.

IGNITION, TIMING, ETC, 91

PART V
SINGLE— DUAL— DUPLEX— TWO-POINT SYSTEMS

. MAGNETO WIRING AND CONNECTIONS

When used as an independent source of ignition, the wiring of a
magneto is a very simple proposition, but when used in connection
with a battery auxiliary, the amateur electrician often becomes con-
fused with the multiplicity of wires and connections. The additional
circuits due to a self-starting and lighting system by no means tend
to simplify matters.

In general, the circuit of an independent magneto depends upon
the type of magneto, i. e., whether it is of the true high tension type
or whether used in connection with an external spark coil, since in
the latter type there are several primary wires leading from the mag-
neto to the coil on the dash. When this system is "double," that is
when two plugs are used per cylinder, the high tension circuit is
different than with the single system. To simplify matters, we will
confine our attention at present to the combinations commonly used
with the true high tension type, or the type in which the magneto
windings generate the high tension current without the use of ex-
ternal coils.

Independent Magneto. When a magneto is used without batteries,
as in diagram No. 1, there is a high tension lead from each plug P in
the cylinders to a corresponding connection post on the distributer D.
A primary or low tension wire leads from the circuit breaker C to the
switch S located on the dash. The remaining terminal of this switch
is "grounded" or connected to the frame of the car or engine. With
some late types of magnetos there is no switch S, this short circuit-
ing switch being embodied in the circuit breaker casing, so that the
magneto is cut out by moving the spark lever on the wheel to "full
retard." When installing the magneto care should be taken to have
the magneto base in full metallic contact with the frame of the motor,
so that the magneto will also be effectively grounded for the return
of the current. The advance and retard of the circuit breaker is
shown by A.

Dual System. In the dual system both a battery and magneto are
used, the former being used in starting and as an auxiliary against

IGNITION; TIMING, ETC, 93

the failure of the magneto. With the dual system a single set of
plugs is used for both the magneto and battery, and the magneto dis-
tributer distributes the high tension current for both. The usual con-
nections are shown by Fig. 3, in which CS is the battery spark coil
and switch mounted on the dashboard, B is the battery^ M is the mag-
neto with the circuit breaker C and the distributer D. And as in the
first case, P are the plugs in the cylinders.

As will be seen from the diagram, one pole of the battery is
grounded to the frame, as is also one terminal of the coil. For details
of this system for different makes of magnetos see the diagrams
throughout this chapter.

Duplex System. In the duplex system both the magneto and bat-
tery are used, and in some cases an independent vibrator is intro-
duced into the starting system. Instead of having a separate coil
for the battery, as in the dual system, the primary and secondary coils
on the magneto armature are used to produce the spark when the bat-
tery is used. In this type, the circuit breaker and distributer of the
magneto are used in common by the battery and magneto. In start-
ing, the switch is thrown so that the battery current passes through
the primary winding of the magneto armature, the interrupting and
timing being performed by the circuit breaker, each interruption caus-
ing a spark at the plugs. The high tension current from the secondary
winding of the armature is led to the distributer as in the case when
the magneto is working alone.

When running normally on the magneto alone, the battery is cut
out of circuit. To increase the spark at starting, the Bosch duplex
magneto has a vibrator in series with the armature (see Fig. 2),
which is cut out in normal running. In Fig. 2, VC is the combined
vibrator and dash switch.

Two-Plug Independent System. To insure complete independence
of the battery and magneto systems, the circuits are made entirely
separate from one another, as shown by Fig. 4, there being two sepa-
rate sets of plugs P and P^, the first for the battery spark and the
second for the magneto. Unlike the previous systems, there is a dis-
tributer BD and circuit breaker for the battery system, and a circuit
breaker C and distributer D for the magneto M. The battery coil
CS carries a switch which opens and closes either independent cir-
cuit. The battery B is grounded on one side.

This arrangement makes the secondary wiring very complicated
and difficult to arrange properly on the motor, since there are twice
as many high tension leads to take care of. Since the plugs are the
most common source of trouble, the complication due to wiring and
the installation of a separate distributer do not make this system
advisable in ordinary cases. The comparatively unused battery plugs

IGNITION, TIMING, ETC,

arc generally foul when called upon in an emergency, and therefore
the system is little more, if any, reliable than the dual system un-
less one wishes to assume the trouble of caring for twice the neces-
sary number of plugs.

Two- Point System. To increase the output of a motor, especially
on racing cars, it has been common practice to have two sparks
occur simultaneously in the same cylinder at rather widely separated
points in the combustion chamber. Whether this amounts to any
material increase is rather doubtful. A recent test run showed that
the increase was only in the nature of 5 per cent, an amount that in

Fig. 6. — Single Cylinder Motor Arranged for Dual Ignition.

an ordinary pleasure car would hardly justify the additional compli-
cation and expense.

By installing two points of ignition it was thought that the distance
through which the flame had to travel would be reduced, since there
were two points from which the flame would spread. An increase in
the rate of combustion obtained in this way would naturally decrease
the loss of heat to the jacket water, and therefore increase the power.
This effect, of course, would be more pronounced in the case of a
T-head motor where the distance across the combustion chamber is
at a maximum. In the case of the T-head in a certain test this in-
crease amounted to 10 per cent under conditions very favorable to
the system, that is, the cylinders were very large, deeply pocketed,
and the piston velocity was extremely high. With the automobile in
ordinary service the advantages are questionable, especially with
L-head or motors having overhead valves.

IGNITION, TIMING, ETC, 95

In general there are two ways of producing the double spark from
a single magneto. (1) By providing the magneto with a double dis-
tributer, one distributer for each set of plugs and arranged so that
each distributer causes simultaneous sparks in each cylinder. (2) By
means of a single distributer and special plugs, one plug in each cyl-
inder being of the double pole variety in which both sparking points
are insulated from one another and from the metal of the cylinder.

The first method is shown by Fig. 5, in which the double dis-
tributers D and D2 control the two sets of spark plugs P and P^, re-
spectively. The plugs used in this system are of the ordinary type.
The primary connections are practically the same as those of the
single magneto, and the system can also be used in dual with the
battery.

With a single distributer, the high tension circuit must be arranged
so that the current passes through the first plug, across the points to
the second plug and thenoe to ground or to the cylinder of the motor.
This necessitates, of course, insulating both of the points of the first
plug from the cylinder, for if either of the points make contact with
the metal, no current -will flow to the second plug. The second plug
is of the ordinary variety.

96 IGNITION, TIMING, ETC.

PART VI
REPRESENTATIVE MAGNETO TYPES

THE NEW EISEMANN MAGNETO

A new type of Eisemann magneto brought out in 1914, known as
model **G," has a number of features not possessed by the model
just described. The mechanism of this new magneto is externally com-
pletely covered with a sheet metal cover so that it is exceptionally
smooth and absolutely oil and waterproof. It is of the straight high-
tension type, no coil being used and with no provision for battery
connections.

Due to a more efficient arrangement of the armature winding it is
possible to use only single magnets instead of the double V*s so
commonly used in other instruments. The distinctive wedge shape
pole piece is still used as shown by Fig. 1, which allows of a hot,
strong spark at very low speeds.

It will be seen from the cut that the wedge shaped poles are thicker
at the center than at the ends, a construction that causes the magnetic
lines of force to be drawn from the ends of the poles to the center.
This permits of the entire magnetic volume being forced through the
windings with a minimum leakage. In addition, the tapered poles
allow of a greater range of advance and retard without a change in
the density of the spark.

The high tension slip ring has been moved to the other end of the
shaft so that it is now at the same end as the circuit breaker. This
change brings all of the delicate parts of the instrument at the same
end where they are readily Accessible by removing the distributer and
circuit breaker covers.

The distributer is entirely new, all of the connections being made
inside of the casing, bemg therefore perfectly waterproof.

By having the distributer disc and high tension collector ring at
the same end of the magneto it is possible to have very short high
tension connections, the brush from the ring leading directly to the
/ revolving distributer arm.

The high tension leads enter tapered holes in the top of the dis-
tributer block, the stripped ends being wrapped around large threaded

IGNITION, TIMING. ETC. ' 97

studs. A keyed washer is placed over the wire for the nut. The
forcmg of the wires through the holes in the distributer prevents
water from leaking past the cables.

The high-tension distributer contacts as well as the ground connec-
tion arc carbon — light springs being used to insure perfect contact
with the distributer arm.

The distributer arm is inserted in the disk with which it rotates
touching in turn the high*tension lead contacts. The location of the
current collecting slip ring in its present position has made possible
the elimination of a large number of parts heretofore necessary. The
t collecting brush is mounted in the distributer block and is
)ved with it, exposing the slip ring when the block is taken off.

Fig. 1. — Eisemann Poles and Tunnel — "The Automobile."

This makes it unnecessary that the current be led from one end of.
the magneto to the other as has been the case in the past.

Another excellent feature of the new instrument is that installation
and timing have been simplified to the greatest possible degree. On
the distributer gear there are two marks, one for left hand engines
and one for right hand engines. In timing the magneto it is merely
necessary to place one piston in firing position and turn the distributer
gear until one of the marks, depending upon the direction of the rota-
tion of the crankshaft, is in line with a screw in the distributer cov-
ering.

The circuit breaker, Fig. 2, is entirely new. Instead of being a
comparatively heavy arm, there is a very light spring A which carries
one of the platinum contacts B and which rotates with the armature
shaft; the other contact C is mounted in the part which supports the
spring.

The auxiliary spring Al is merely for the purpose of slightly

IGNITION, TIMING, ETC.

en the contact points;
e plug P in order to elir

> separated

te the p OS-

increasing the pressure bi
from the main spring by a
sibility of trouble resulting frc

Made integral with the breaker box there is a small cylinder D with
two fibre inserts E and a third felt insert F, the latter serving merely
for lubricating purposes. As the breaker mechanism rotates with the
armature, the spring A wipes alternately against the fibre inserts D
and E, thus making and breaking the primary circuit. The simplicity
of this mechanism is only one of its noteworthy features. As there
are no bearings, it is impossible for wear to cause irregular firing, and
as there is nothing to stick possibility of trouble on this a

Circuit Breaker.

Ijositively ehminated. Another very valuable feature is that owing to
the exceptional lightness of the parts there is no battering of contacts,
which, consequently, may be expected to wear a correspondingly
longer time.

BOSCH HIGH TENSION MAGNETO

The Bosch DU4 type is a typical true high tension magneto, the
armature containing a primary and secondary winding, the primary
being periodically interrupted by means of a circuit breaker. The
circuit diagram is shown clearly by Fig. 3, which \vill serve as a guide
to the actual construction that will be described later on. For clear-
ness, the armature is shown in side elevation, while the distributer
and circuit breaker are front elevations. The primary wiring is shown
by solid heavy lines, the secondary by fine solid lines, and the
grounded circuit by dots and dashes.

IGNITION, TIMING, ETC. 99

Since the secondary winding is simply a continuation of the coarse
wire primary winding it is shown as a single coil wrapped around
the core of the armature. The Wgh tension is collected at the left of
the armature by means of a collector ring and brush, the lead from
the upper terminal of the hrush being connected to the safety spark
gap on its way to the distributer brush.

The distributer brush as it revolves makes successive contact with
distributer segments 1-2-3-4, leads from these segments, running to
ihe respective spark plugs 1-2-3-4 shown in the upper left-hand corner
of the diagram.

A condenser is housed with the armature at the right whose pur-

Fig. 3. — Bosch High Tension Magneto Circuit.

pose is to absorb the spark at the circuit breaker. points and to hasten
the rapidity with which the primary circuit is broken. One end of
both the primary winding and the condenser is grounded, the remain-
ing condenser terminal being connected to the lead that runs from
the armature to the circuit breaker at the right. The outer shells of
the spark plugs, the frame, and the armature are all grounded as will
be seen from the dot and dash lines.

In the longitudinal section shown by Fig. 4, the high tension current
from the secondary winding is led to the high tension collector ring 9.
A brush 10 pressing on this ring collects the current, and through
the spring 11, the bridge 12, and the brush 13, it passes to the rotating
distributer brush or arm 15. In rotating, the brush mak'es jsuccessive

100 IGNITION, TIMING, ETC.

contact with the distributer segments previously mentioned in the
circuit diagram. All brushes 10-13 and 15 are pressed against their
bearing surfaces by small spiral springs.

A serrated edged terminal shown projecting from the bridge 12 into
the safety spark gap housing is placed opposite to another terminal
fastened to the top plate of the armature tunnel. This gap prevents
an excessive voltage that might be caused by a loose or broken high-
tension connection.

Primary current is led from the armature to the circuit breaker
through the insulated connection bolt 2, an intermediate connection
being made to this bolt from the condenser 8. The outer end of the
bolt 2 is connected to the interrupter or circuit breaker jaw 3, an
insulating strip 4 separates the block from the metal of the frame.
At the end of 2 a spring controlled brush carries current to the ter-
minal 24 through the spring 26 and the clip 25. A connection from
24 is led to the grounding switch on the dashboard whose purpose
is to stop the engine by grounding the primary current. The support-
ing block 27 is insulated from the clamp 23 which holds the distributer
cover 22 on the distributer disk 16.

A hard rubber hub 14 carries the brush 15, these parts being readily
accessible through the removal of the distributer cover 22. The pro-
longed shank of the hub 14 rotates in the bearing at the left of the
hub, the bearing being thoroughly insulated from the current con-
ducting rod that runs from the brush 13 to the brush 15. Above the
hub in the open space will be seen a face view of one of the distributer
segments.

Under the base of the magneto and directly under the condenser
will be seen the primary grounding-brush through which the current
returns to the armature from the grounded parts on the frame. This
avoids passing the primary current through the ball bearings, and so
saves them from the pitting action that would be certain with the
passage of current through the ball races.

The end of the primary winding is connected to the plate 1 into
which the connecting bolt 2 is screwed. This plate is of course insu-
lated from the frame by the strip of hard rubber shown between the
end piece and the condenser 8.

Current from 2 enters the breaker block or jaw 3, which on referring
to the front elevation, Fig. 3, will be seen to carry the platinum
breaker point retained by screw 5. These parts are both insulated
from the breaker disk 4 which carries the rotating parts. A contact
breaker lever 7 (grounded to the frame) carries a platinum screw 29
which makes contact intermittently with the first platinum point 5.
These points are normally forced into contact by the flat spring 6.
It should be iremembered that the contact block 3, points 5 and 29, the

IGNITION, TIMING. ETC. > lOl

lever 7 and the spring 6 are mounted on the armature front plate 4 and
revolve with it.

Two tiber cam disks 19-19 mounted in the breaker housing make
contact with the toe end of the lever 7, causing the platinum points to
open every time that the end of the lever passes the cams. As this
is a shuttle armature giving two current impulses per revolution, there
are two cams to open the breaker at the highest voltage peak of each
impulse. The points are therefore opened twice per revolution, giving
a high tension spark at the plugs at each current interruption. A
rocker arm 20 is connected with the breaker housing so that the
housing and the cams can be rocked to and fro for advance and retard.

oil

When the house is turned against the r

toe of the lever 7 meets the cam 19 earlier in the revolution, causing

the interruption to occur earlier and consequently advancing the

Since the lever 7 is grounded it is in connection with the beginning
of the primary winding which is also ground. As the block 3 is
connected to the outer end of the primary, the circuit is closed when
the two platinum points are in contact, allowing the current to flow
and build up the magnetic flux. When the points separate the flux
contracts suddenly through the secondary windings, causing a high
potential in the secondary.

The brush 15 carried in the distributer arm 14 receives the high

102 IGNITION, TIMING, ETC.

tension current as described in an early part of this section. The
distributer segments connect with plug sockets 16 into which are
pushed the plugs or spring jacks 18 that carry the high tension cables
to the spark plugs in the cylinders.

There are as many segments and plugs as there are cylinders.
With single and double cylinder engines there is no distributer, the
high tension current being carried directly to the spark plugs from
the high tension collector rings. In every other respect the construc-
tion is the same.

The distributer brush is driven from the armature shaft by a gear
and pinion, the distributer traveling at half the armature speed with a
four-cylinder engine and at three times armature speed with a six-
cylinder.

With the shuttle type magneto of which the Bosch is an example
there are two sparks per revolution of the armature. For the proper
ratio of the armature to the crank shaft speed of the engine see the
table under the "Elementary True High-Tension Magneto."

As a guide to the proper magneto speed, find the number of impulses
given by all of the cylinders in one revolution, Now find the gear
ratio that will give the magneto a current impulse for every power
impulse of the engine. With a four-cylinder, four-stroke cycle engine
there will be two power strokes per revolution, since each cylinder
has a power stroke in every two revolutions. Since the magneto also
gives two sparks per revolution, it will run at crankshaft speed.

Needless to say, the Bosch magneto must be geared or chain driven
by the engine, since there is a positive relation between the piston
position of the engine and the time at which the circuit breaker opens
the primary circuit.

BOSCH OSCILLATING MAGNETO

When very low rotative speeds are used as with large, heavy duty
stationary engines, it is difficult to obtain good results with the ordi-
nary type of magneto. Under these conditions it is usual to use a
magneto in which the armature is snapped past the fields at the firing
point by means of a spring and tripping device, the armature being
oscillated back and forth instead of being rotated continuously in one
direction.

An oscillating magneto built by the Bosch Magneto Company is
shown in outline by Fig. 5. The armature is actuated by a rotating
cam which moves the armature 30 degrees from its normal position
when at rest. When the face of the cam ''b" strikes the trip lever,
the armature is turned until finally it assumes the position shown; a
very little farther motion will release the lever and allow the springs

IGNITION. TIMING. ETC. 303

to snap the armature back in a left-handed direction. The direction of
cam rotation is shown by the arrow.

It will be seen that the armature speed and hence the intensity of
the spark is absolutely independent of the engine speed.

A double wound shuttle armature is used as with the usual true
high tension type, and the primary current is interrupted by the usual
form of circuit breaker. At the moment of interruption the spark
appears at the plug.

Fig. 5.— Bosch Oscillating High Tension Magneto.

T)vo cams, (a) and (b), are mounted side by side on the cam shaft,
one cam (a) giving a retarded spark for starting the engine, and the
other giving an advanced spark for normal running. The cams are
mounted on a sleeve which may be moved longitudinally on the shaft
(c), guided and being prevented from turning by the key-way or
feather (e). Thus by moving the sleeve on the shaft, the trip lever
may be either brought into contact with cams (a) or (b), A spiral
spring is placed between the cam (b) and a collar mounted on the

104 IGNITION. TIMING. ETC.

shaft which tends normally to keep the cam (b) in contact with the

The circuit breaker is set so that the primary circuit is broken when
the armature is moving at its greatest velocity so that the
spark may be obtained.

INDUCTOR MAGNETOS

An inductor type magneto has no revolving primary winding a
the shuttle type, the winding being mounted on a stationary c

which is attached to the frame of the magneto. The only revolving
parts in the inductor are the shaft and a sector shaped mass of iron
or steel called the "inductor." With a stationary coil it is possible
to dispense with brushes and collector rings and in most cases this
construction permits of more room for the wire and insulation. At
the present time, the Remy, Pittsfield K.W. and Dixie are the only
inductor types on the market and the reader is requested to look for
these types under their respective headings.

In Fig. 6 is shown a perspective of a Remy inductor magneto system
in which N-and S are the two magnet pole shoes and C is the primary
winding. The iron inductors I and I' are mounted on the shaft D-E

IGNITION, TIMING, ETC, 105

and revolve with it, alternately coming opposite the pole shoes N
and S.

In the position shown, the magnetic flux from the pole N passes
across and through the inductor I^, through the iron shaft D-E and
back to the pole shoe S through the inductor I. As the flux passes
through the shaft it also passes through the coil of primary wire C.

As the inductors revolve they interrupt and reverse the flux passing
through the coil, thus producing an alternating current in C. Con-
sider the inductors turned through 180 degrees from the position
shown. The inductor I will now be in contact with N, while inductor
P will be in magnetic contact with pole shoe S, thus reversing the
direction of the flux through C. There are two reversals of flux per
revolution and hence it is possible to have two sparks per revolution.
The coil is supported from the pole shoes by the lugs B and F.

The ordinary type of horseshoe magnets are placed over and bolted
to the pole shoes. The ends L-L^ of the coil C lead directly to the
transformer coil without the use of brushes or slip rings, making
a very simple and reliable job.

True high-tension inductor magnetos are particularly desirable, since
in the shuttle type it is always a matter of difficulty to properly place
the high-tension brush and high-tension collector rings that are con-
nected to the secondary winding. The K.W. and the "Dixie," described
elsewhere in this book, are of the true high-tension type of inductor
magnets, as the primary and secondary of the coil are mounted on
the same core.

Inductor magnetos always deliver alternating current, as it would
be almost impossible to properly mount a commutator.

REMY TRANSFORMER TYPE MAGNETO

In Fig. 7 the application of the Remy inductor principle is seen
applied to the actual machine, the spark coil and the dash switch being
omitted for the sake of simplicity. The front elevation is shown by
the left view, while at the right is a longitudinal section taken along
the center line of the machine. This is known to the trade as Model S.

Mounted on the driving shaft S108 are the two inductors S21 con-
nected with the short sleeve S20. The primary coil is shown by SIO
and is held in place by the clips S19. The breaker cam S157 is held
on the shaft and works against the hardened steel plate S31 (see front
view for circuit breaker). The hardened steel plate is fastened to
the rocker arm S30, which also carries the contact spring S33 on which
the platinum contact points S36 are mounted. A spiral spring S55
holds the rocker arm against the cam at all times. Screws or knurled
nuts S54 and S48 are for the purpose of connecting the lead to the coil

IGNITION, TIMING, ETC. 107

and for adjusting the platinum points respectively. S45 is the timing
lever, which moves the entire housing for the advance and retard.

Consulting the longitudinal section, the pinion SISS mounted on the
inductor shaft meshes with the gear S154 which is mounted on the
distributor shaft SlIO. This shaft is carried by two plain bearings at
the front and rear which are fed with oil by the copper tubes shown
entering the oil cup at the top and rear S228. The distributor disc
is shown at the extreme left of the distributor shaft, which is made of
some highly resisting material such as hard rubber. This is fed willi
high tension current from the brush S122 connected to the terminal
plug, the brush being forced into position with the spring S123. With

Fig. 8.— Circuit Diagram of Eemy Transformer Magneto.
Courtesy "Motor Age."

a four cylinder motor the distributer shaft runs at half the speed of
the inductor shaft.

Looking at the front elevation, the distributer disc is marked S258,
and on the disc is shown the brass distributer segment S117 against
which the brush from the high tension lead presses. As this sector
revolves it comes in successive contact with the contacts of the four
high tension plugs marked S136, a cable frotn each of these plugs
running to the spark plugs in the cylinders. The contacts with which
the sector meshes are in the form of four wires spaced equally around
the circle and may be traced by following the dotted lines that run
from the plugs to the distributer disc circle. The distributer parts
are covered by a removable cap SI20, which may be easily removed
Cor inspection. This sector does not actually rub on the four contacts
but comes within approximately 1/64 inch so that it is an easy matter
for the spark to jump.

The proper points of connections for the coil leads are easily found
from the accompanying circuit diagram which shows the colors of
th? leads and the points at which they c

108 IGNITION, TIMING, ETC.

"K. W." INDUCTOR TYPE MAGNETO

As with the Remy magneto, the primary winding of the K. W.
inductor magneto occupies the space between the two revolving
inductor masses, but unhke the former example this magneto gives
four instead of two current impulses per revolution. The construction
of the K. W. system is shown by Fig. 1 in which A and A' are the
inductors and C is the primary wintiing. As the inductors are double
ended and at right angles each inductor cuts the magnetic field four
times per revolution, two times for each end.

This magneto may be used either as a low tension, low tension

Fig. 9.— Inductors of K. W. Magneto.

transformer type, or as a true high tension magneto. When used as
a true high tension type the usual circuit breaker and high tension
distributer are mounted directly on the instrument. Usually the
primary coil of the low tension K. W. magneto is made up of a strip
of sheet copper rolled on an insulating spool, since this construction
gives a lower resistance and hence a greater volume of current than
with the round copper wire generally used, space for space.

Like all magnetos, the true high tension K. W. is positively driven
from the engines through gears or chain, and as there are four
impulses per revolution instead of two, the speed relative to the
engine is half that given for the shuttle type armature. The greater
number of impulses makes this magneto very desirable on eight and
twelve cylinder motors as the rotative speeds are much reduced.

IGNITION, TIMING, ETC. 109

"K. W." HIGH TENSION MAGNETO

The "K. W." high tension magneto is of the inductor type and
generates high tension current directly without the use of a spark
coil. The arrangement of the coil and inductors is practically the
same as in the case of the low tension K, W. magneto described
under the head of "Inductor Magnetos," except for the tact that the
generating coil carries both a primary and secondary winding. Using
the same form of inductor with the two bars at right angles to one
another, the high tension K. W. also gives four current impulses per
revolution.

Fig. 10.— Longitudinal Section Through K. W. High Tension Magneto.

A longitudinal section is shown by Fig. 2 in which 16-16 arc the
inductors and 17-18 are the primary and secondary coils respectively.
The two coils are wound on a single spool which occupies the space
between the two inductors. A heavy hard rubber insulator is mounted
on the spool, this carrying the high tension lead from the secondary
coil to the point where it connects with the bridge 21. This is shown
cross-hatched with heavy black lines. The current from the primary
winding is led to the circuit breaker through the connectors 22, 25,
and 12, the final connections coming from 12 to the terminal 6, and
then through strip 5 to the breaker jaws.

High tension current from the bridge 21 splits two ways, one way
being to the distributer through 13, and the other being to the safety
sparks gap 20. Current enters the porcelain cap through a point, and
if a sufficiently high voltage exists it jumps across the gap 20 to the

110

IGNITION, TIMING, ETC.

point mounted on the condenser case 19, and thence to the frame and
g:round.

A condenser 19 is connected across the primary winding in the
same way as in the case of the shuttle wound armature. As one end
of the primary winding is grounded, one side of the condenser is also
grounded, thus leaving only one wire to extend from the primary to
the condenser. The free end of the primary winding is closed and
broken by the interrupter contacts, a spark being produced at each
interruption.

High tension current from the lead 13 enters the distributer by the
way of the brush 9, and from there connects with the main distributer
brush 10. As this distributer brush revolves it comes into successive

Fig. 10-A.

contact with the metal distributer segments 7 which are arranged
around the insulating distributer block at evenly spaced intervals.
The number of segments, of course, correspond with the number of
spark plugs or cylinders.

The method of connecting the magneto distributer to the cylinders
is shown by Fig. 10-A in which S and S^ are two of the distributer
segments, and B is the rotating distributer arm. High tension current
is led to the cylinders 1-2-3-4 from the respective distributer terminals
1-2-3-4. The dotted distributer arm B"- shows the position for left
hand rotation while the full line arm is the position for right hand
rotation..

A detail of the circuit breaker is also shown by the front elevation.

IGNITION. TIMING, ETC. ill

The indnctor, or "Rotor" shaft as il is sometimes called, is mounted
on ball bearings which require a minimum of attention and lubrica-
tion. The inductors are laminated, that is, are built up of sheets of
soft iron or steel to increase the magnetic effect in the coil. It will
also be noted that a sleeve is placed over the shaft for the purpose of
increasing the area of the core that passes through the center of the
coil and between the two inductors.

Unlike the case with the majority of magnetos, there are five mag-
nets used, each magnet being of a square cross-section. This gives
a very powerful field and an intense spark at extremely low speeds.

A flexible coupling is shown at the left end of the shaft which
prevents strains from being thrown into the magneto bearings should
the magneto and driving shafts be thrown out of alignment. As
shown, the magneto is driven from the extended end of the pump shaft.

HERZ (RUTHARDT) MAGNETO

Probably one of the unusual features of this interesting magneto
is the construction of the magnets. There are thin circular steel discs
having the opening for the armature bored at the lower edge to the

exact size of the tunnel, no cast pole pieces being used. The com-
plete magnet is built up by stacking teu or twelve of these discs in
a row and then riveting them together with four longitudinal rods.
One of these discs is shown by Fig. 11.

After machining the bore for the armature, the interior of the
bore is polished so as to obtain an exceedingly small air gap between
the armature and the pole. This gap in the Herz Magneto is only
0J)015 inch which allows of a maximum magnetic flux through the
armature. By avoiding the use of pole pieces the magnetism is

112 IGNITION, TIMING, ETC.

again conserved since considerable leakage takes place at this point
in the ordinary type.

The armature is of the usual shuttle type with a primary and sec-
ondary winding, the primary circuit being interrupted in the usual
way by a circuit breaker. In this instrument the secondary is not
a continuation of the primary as in other high tension types, but is
thoroughly insulated from the primary as well as from the metal of
the frame.

A feature of the circuit breaker is that it has no bearings and
therefore requires no oil and wearing parts are avoided in it. An
insulated block D is secured to the rotating disc of the breaker box
by the screw I. A spring A with a platinum contact B is fastened to
K. Screw C holding a platinum point is the adjustment for the
breaker and is threaded into the block D.

The edge L of the block D forms a guide for the fiber roller E
which has considerable play around the small spindle F while retained
by a flat spring not shown. The end of the spring A rests against
the roller pressing it forward, this action being aided by the cen-
trifugal force. The roller which runs on the interior of the rim N
will allo^Y contact between points B and C except when it passes
over the cam-face G. This pushes the roller inwards, forces the
spring A outwards and separates the points. The number of cam-
faces G used, depend on the number of cylinders in the motor.

The rim N which is the outer shell of the breaker box may be
rocked to and fro to obtain the retard and advance. The bolt M
conducts the current from the armature to the contact block D. A
spring in the cover of the breaker box rests on M, terminating in a
binding post which carries the wire from the cut-out switch. This
spring and binding post are, of course, insulated from the frame of
the magneto.

IGNITION, TIMING, ETC. 113

PART VII

MAGNETOS WITH SIMULTANEOUS ADVANCE OF
BREAKER AND MAGNETIC FIELD

MEA MAGNETO

In the usual type of magneto the magnets and pole shoes are sta-
tionary while the circuit breaker housing is capable of being rocked
back and forth to obtain the desired advance and retard of the spark.
Since a maximum voltage is obtained only at one position of the
armature in the magnetic field it is evident that the circuit breaker
opens the primary circuit at many points where the voltage wave is
comparatively low, while the housing is being moved from advance
to retard. In othfer words, it is possible to obtain the maximum spark
at only one position of the breaker housing.

In the majority of cases the breaker is set for the maximunj spark
with the housing in the fully advanced position. This, of course,
causes the weakest spark to occur at full retard, the very point at
which the strongest spark is required, as the retarded spark is always
used in starting. With a low cranking speed, a poor mixture and a
cold motor the already weak retarded spark is still further reduced
in igniting value, often making the starting operation very difficultT

When running the engine at low speeds or in cases where the
motor is overloaded, as in climbing hills, the effects of the retard
are again a cause of annoyance, the failure of the spark to ignite the
charge often causing the engine to stall at a critical time. Attempts,
therefore, have been made to obtain a uniform soark independent of
the timing.

With the Mea magneto the magnets and breaker housing practically
are in one piece, the breaker therefore always opening the primary
circuit at a constant armature position. The advance and retard are
obtained by rocking both the magnets and the circuit breaker as one
unit, the relative positions of the magnets and breaker remaining
constant. This result is obtained by mounting the entire magneto
on a rocking cradle in such a way that the relation between the arma-
ture and pole pieces is changed when advance or retard of the spark
is desired. With this method of mounting there is no limit to the
angle of timing, since with a suitable supporting cradle it would be

114 IGNITION, TIMING, ETC.

possible to rotate the entire frame through an angle of 360 degrees
without changing the quality of the spark. Practically the'Mea has a
timing range of from 45 to 70 degrees, since this is more than ample
for any ordinary condition met with in automohile work.

To obtain the greatest benefit from the rocking cradle and to have
a low compact instrument, the Mea magnets are bell shaped, with the
magnet legs lying parallel with the armature shaft. This can be seen
from Fig. 6 and Fig. 7, the elevation showing the magnets as a hori-
zontal cylindrical frame extending from left to right In the section
the magnets are shown by the figure 100,

Fig. 1.— Elevation of Hea Magneto.

Consulting the cross-section. Fig. 7, it will be seen that the arma-
ture 1 is of the -conventional shuttle wound type, the condenser 12
being contained within the armature. The high-tension lead from
the secondary winding connects with the high-tension collector ring
4, while the primary current is led to the circuit breaker through the
hollow right-hand shaft by the connector bar 24. The armature is
carried by the ball bearings 17 and 18.

The magnets 100, indicated throughout by the double cross-hatch
lines, are fastened to the frame 61 at the left, the latter carrying the
ball bearings. The frame 61 is mounted in the cradle 53, in which
it is free to rock to and fro for the advance and retard. At the right
a similar bearing is formed in the cradle, at 60b, the parts 60b at the
right and 60a at the left being the upper halves of the cradle bearings.
Two spring controlled plungers III at right and left press against the
rocking frame to prevent it from slipping loosely in the bearings.
The magnetic pole shoes are the thin horizontal strips shown directly
opposite the armature 1.

IGNITION. TIMING. ETC. 115

Primary current from the armature led through ihe conductor 24
to the circuit breaker plate 28, which is insulated from the frame.
On this plate is mounted a spring 30, which carries the platinum con-
tact point 34. This is the movable contact point. A fiber cam roller
31, which revolves with the plate 28, rests against the cam plate 40
at the back. The cam plate being provided with two cam projections
causes the cam roller 31 to strike the spring 30 twice per revolution.

Fig. 2. — Section Through Mea Hagneto.

breaking the contact between platinum points 33 and 34 and opening
the primary circuit. The point 33 is grounded to the frame through
the plate 27.

As the inner end of the primary winding is grounded to the arma-
ture core, the return current from the plate 27 flowing through the
frame passes through the grounding brush 78 on its way to the arma-
ture. This completes the primary circuit.

The breaker housing is closed by a cover 74, which supports a
carbon brush 46 through the insulating brush holder 47, this brush
coming in contact with the primary current connector 24. The ter-
minal screw SO connects with the brush, and a lead from this terminal
runs to a short circuiting switch on the dashboard. When the switch
is closed, the primary current from the armature passing through
terminal 50 is grounded, which of course will stop the generation of
current and will therefore stop the engine.

116 IGNITION, TIMING, ETC.

High tension current from the secondary winding is taken from the
high-tension collector ring 4 by the brush 77. This brush is sup-
ported by the insulating holder 76, a spring in the holder being used
to force the brush against the collector ring. The holder 76 and
the low-tension brush 78 are fastened to the plate 91, which in turn
is supported by the magnet frame. Current from the high-tension
brush is led through the bridge 84 to the distributer brush 69. The
connection from the brush holder 76 passes through the insulating
cover 89, which also acts as a safety spark gap.

The distributer consists of an insulating cover (stationary) 70 and
a rotating part 66, the latter being driven from the armature shaft by
the steel and bronze gears 7 and 72. Current reaches the rotating
part of the distributer through the brush 69. From here the current
reaches the two distributing brushes 68, which are placed in slots cut
in the insulating material, the brushes being placed at right angles
to one another. These brushes make alternate contact with four
contact plates which are imbedded in the insulation of the stationary
part of the distributer. These contact plates are connected to the four
high-tension spark-plug terminals 108, which are located on top of
the distributer.

The relative location of these plugs can be seen from the side ele-
vation of the instrument, where it will be noted that the plug con-
nections are arranged in two rows of two plugs per row. In the front
of the distributer are small windows behind which appear numbers
that are engraved on the distributer gear. These numbers correspond
to the number of the cylinder that the magneto is firing at that time.
This makes the reconnection of the magneto a simple matter.

A frame or cradle 53 carries the magnets, distributer, armature, etc.,
in such a way that the magnets, and with them the timer, can be
rocked back and forth by a timing lever that is mounted on one side
of the magnets. The spark is advanced by turning the magnets in a
direction opposite to the direction of armature rotation.

The one-cylinder magnetos are similar to the four-cylinder except
that the distributer is omitted.

DIXIE HIGH TENSION MAGNETO

The "Dixie" magneto is of the- high tension type, but is entirely
different in construction from any magneto on the market. It is of
the "inductor type," that is, there are no revolving windings or wire,
the only revolving part being an iron mass that directs and breaks
the magnetic field in a stationary coil. Figs. 4-5-6-7 show the cycle
of operations of tfie revolving inductor marked N-S, while Fig. 8
shows the arrangement of the circuit.

Unlike the usual magneto, the shaft is at right angles to the plane

IGNITION. TIMING, ETC.

117

of the "U" form magnets, as shown by Fig. 12, in which M i
magnet, C is the core of winding, and W is the winding which c
of a primary and second coil. The two shoes of the inductor, N and S,
are practically at all times in contact with the ends of the horseshoe

Magneto. Inductor Type With Advance and Retard o

magnet, and consequently at all times have the same polarity. Look-
ing at the view shown by Fig. S, which is taken at right angles to
the first figure, we see the sector-shaped shoes of the inductor N-S.

Since the two revolving shoes are always of the same polarity, they
alternately produce opposite polarities in the core poles G and F, caus-

118 IGNITION, TIMING, ETC.

ing a reversal of magnetic flow through the iron core C of the wind-
ing. At each reversal a current impulse is induced in the stationary
winding. In the position shown the current flows to the left from the
upper shoe N.

A turn of a little less than 90 degrees brings the condition shown
in Fig. 6, where the shoe end N comes opposite the core pole F,
causing a flow of flux to the right. In Fig. 7 the shoes are shown in
the mid-position, short-circuiting the core C and thus cutting the
magnetic flux flow to zero.

This advance from zero magnetic flux, and back to zero, causes
the maximum current in the winding, since the magnetic variations are
sharp and sudden. It should be understood that the current depends
on the rate or speed with which the magnetic variations take place,
and not altogether upon the intensity of the magnetic field.

Since no moving wire is used, the difficulties ordinarily experienced
with the shuttle type armature in collecting the current are removed,
having less parts to wear and avoiding unnecessary friction and brush
trouble. There is more space for the windings and their insulation,
and the wire is at no time under the strain caused by centrifugal
force.

Fig. 8 shows the circuit diagram of the "Dixie," in which the
heavy winding P is the primary, A is the iron core and G is the fine
wire secondary. One end df the condenser R is connected at the point
G, where the secondary winding connects to the end of the primary
winding, the other end of the condenser being connected to the outer
end of the primary, thus placing the condenser in "shunt" or "par-
allel" with the primary winding. The interruption of the primary
circuit is performed by the circuit breaker contacts X and Y, which
are in series with the primary coil P. The end of the secondary wire
at the left connects with the revolving arm of the high tension dis-
tributer.

The coil is mounted in connection with the circuit breaker in such
a way that they move back and forth together for advance and retard,
thus causing the same intensity of spark for any position of the
spark lever. In this magneto the circuit breaker points and the mag-
netic field always retain the same relative position.

IGNITION, TIMING, ETC, 119

INSTALLING HIGH TENSION MAGNETOS

The installation of a high tension magneto requires a considerable
knowledge of machine work and of the functioning of the gasoline
engine, especially when installing the instrument on an old car or on
an engine not built especially for magneto ignition. The following
instructions are therefore not intended for the car owner or chauffeur
but for the automobile mechanic or garage manager who are provided
with the necessary experience and shop facilities for making the
extensive alterations.

When the matter of installing is simply one of replacing an old
magneto with new, on an engine already equipped for magneto igni-
tion, the owner or chauffeur can often make the installation by con-
sulting the chapter on magneto timing, starting with Page 213.

Probably the first point to consider is the gear ratio existing between
the armature shaft of the magneto and the crank-shaft of the motor.
This depends entirely upon the number of cylinders as before
explained, the magneto of a four-cylinder engine running exactly
at crank shaft speed while a magneto for a six-cylinder motor runs
at exactly 1^ times crank shaft speed. For any other number of
cylinders consult the table on Page 7Z, It should be remembered
in this connection that the high tension magneto must be positively
driven from the engine by either a chain or gears so that there is
no slip between the two, and also, that the gear ratios must be exactly
as given for the different number of cylinders. A belt or friction
drive cannot be used.

In ordering the magneto give the number of cylinders so that the
distributer will be correctly arranged, and also give the direction, of
rotation of the armature shaft. If the engine is for other than an
automobile give the bore and stroke of the cylinders and the speed of
rotation. If for a car equipped for magneto ignition give the name
and model or year. Some of the more modern magnetos are equipped
so that they can be used with either right hand or left hand rotation
by a simple adjustment of the distributer disc, while others must be
adjusted for rotation direction at the factory. Give location of timing
arm at right or left.

In regard to direction of rotation first determine the method by
which you intend to drive the magneto. Whether from the crank-
shaft or cam-shaft and also note whether it will be necessary to
introduce intermediate gears between these shafts and the magneto.
It should be remembered that an intermediate gear reverses the
direction of rotation. After this matter is settled trace out from the
crank shaft rotation, the direction of rotation of the magneto following
through all the proposed intermediate gears. If the magneto is driven
from the cam-shaft through a single pair of gears, the magneto rota-

120 IGNITION, TIMING, ETC.

tion will be opposite to that of the cam shaft. Direction is taken
when facing driving shaft end of magneto.

The magneto should be mounted directly on the engine frame by
means of a metal plate or bracket and rigidly bolted in place. The
magneto base must be in absolute metallic connection with the engine
frame without an intervening coat of paint or layer of dirt since it is
through this point that the grounded current returns from the spark
plugs to the magneto. Never use paper or wooden shims under the
magneto. Do not place the magneto against a hot exhaust pipe or in
any place where the temperature is likely to rise above 150 degrees.
Take care, also, not to have the magneto breaker box located near
the carburetor or gas pipes since the spark at the breaker is likely to
cause ignition at points of leaks or overflow.

A flexible coupling must be placed between the driving shaft of
the magneto and the driving shaft of the motor, preferably of the type
known as the "Oldham." This prevents strains from being thrown
into the delicate magneto armature through a lack of perfect align-
ment of the magneto and engine driving shafts. These couplings can
be obtained, usually, from the maker of the magneto and permit of
a considerable degree of error in the lining of the two shafts.

Gearing should be made as accurately as possible with little back-
lash between the teeth or play in the bearings. Any great amount of
play or lost motion between the crank and magneto shafts is likely to
cause annoying intermittent changes in the timing of the ignition. If
chain is to be used the flexible coupling can be omitted, but care must
be taken not to have the chain too slack or too tight. The form will
have the same effect as lost motion in the gears, while the latter will
of course cause unnecessary wear in the magneto bearings.

If possible, place the magneto in such a position that the primary
circuit breaker and distributer can be easily inspected for cleaning
and adjustment. Be sure that the oil holes are accessible, and that
the distributer is in such a position that cables leading to the spark
plug are not unnecessarily long or do not trail over the hot exhaust
pipes. Every additional foot of high tension cable gives an additional
chance of leakage and a weak spark at the plugs. Note the position
of your spark control lever and order the magneto so that the timing
lever on the breaker box of the magneto is on the required side of
the box.

On all engines exposed to the weather, especially with tractors
and farm engines, provide a watertight cover for the magneto. While
all magnetos are specified as "Waterproof," it certainly does no harm
to provide additional protection. Oil and grease are especially to be
provided against for oil is most detrimental to the insulation and
high tension cables. Seek to avoid placing magneto near the rubber

IGNITION, TIMING, ETC. 121

connections used on the cooling system for a leak may cause seriops
trouble.

Having disposed of the subject of location and having the gears and
magneto attachments at hand we will now consider the mounting
and wiring.

Both the gears and couplings to the magneto should be keyed
firmly to their respective shafts, and no dependence should be placed
on set screws or wedges since both of these makeshifts are bound to
slip in time and destroy the accuracy of the timing. Temporarily, or
at least during the period when the magneto is being timed, it is often
convenient to fasten the couplings with a set screw, but the key ways
should be marked and cut at the earliest possible moment thereafter.

Bolt the magneto firmly on the bracket, and place the new gears
and couplings in place, and key the gears that are to drive the shafts.
Idle gears that revolve on the shafts should be carefully bushed with
either bronze or cast iron and provided with means of lubrication.
Chains and gears should be thoroughly protected against dirt or grit
by suitable metal housings. Only hardened steel gears, accurately
cut, are suitable for the purpose, and should have a sufficiently wide
face to insure long service and a minimum amount of noise. A face
y2 inch wide should be the least width of face and should preferably
be Y4 inch. See that the magneto and engine driving shafts line up and
then turn engine over slowly by hand to see if there is any tendency
to crank or bind. There should be a slight clearance between the
flanges of the coupling to avoid any possibility of binding due to lack
of truth in the mounting of the couplings.

Now loosen the temporary set screw in the coupling on the magneto
side so that the armature shaft can be turned back and forth in relation
to the driving shaft for the timing operation.

The wiring depends entirely upon the type of magneto used, or
whether it is of the single, dual, duplex or two point type. Diagrams
showing the principles involved in these different types are shown
on Page 92, and are described in detail in Part V starting on Page 91.
The wiring of the true high tension type is also different from the
transformer type of magneto as previously described. Even among
magnetos of the same type there are differences in the actual con-
nections made between the coil, magneto and switch. Specific wiring
diagrams for the Bosch single, Remy transformer, and K. W. mag-
netos are given in this chapter, with diagrams on pages 94, 99, 107, 110
and 117.

Wiring diagams of all true high tension type magnetos without
battery auxiliary are wired in practically the same way as shown by
Fig. 1 on Page 92 or by the Bosch diagram on Page 99; that is, a
separate lead from the distributer to each spark plug, and a low

122 IGNITION, TIMING, ETC,

tension lead from the breaker box to the switch on the dash-board.
From the remaining connection post of the switch a ground wire
runs to "ground" or rather to the frame of the car or engine. When
Battery auxiliaries are used or with transformer type magnetos, there
are additional wires between the magneto and spark coil and between
the coil and battery depending on the magneto type. The number of
these wires in any system can be taken from the diagrams on Page
92 corresponding to the type used.

For the present, however, we are concerned with the number of
wires, their direction of running, and the method of their support
rather than the actual points of connection on the magneto and coil.
When running the wires leave the ends long enough so that they
will reach to any binding post on the instrument. The makers either
have colored wires on the cables that connect with terminals of
corresponding color on the instruments or number the connection
points on the spark coil that are to be connected with corresponding
numbers on the magneto. The ground wire to frame is marked "G"
and the Battery connection is marked "B" when not fully written out.

All wiring, whether high or low tension, should be firmly supported
by insulating supports and should be of the shortest possible length.
They should not come into contact with the frame or metal parts and
most emphatically should not come into contact with sharp edges or
corners that will be likely to chafe through the insulation through the
vibration of the engine. They should be readily accessible for repairs
or renewal and protected from an excess of grease or oil. This applies
particularly to the high tension cables, for oil is most effective in
the destruction of the rubber insulation.

All high tension wires should be of the very best grade of specially
made high tension cable. The best is none too good for withstanding
a voltage of from 10,000 to 25,000 volts. All wiring, whether low or
high tension should be of the cable or stranded type, built of a cable
of fine wires. A cable is easier to handle than a solid wire and is much
less likely to break or strip. No less than a No. 14 B and S gauge
wire should be used, for smaller wires are mechanically weak and
most likely will be a source of trouble. The best possible method
of supporting wires is by means of fiber tubes, through which they
are run to the point of connection.

Different methods of supporting the high tension wires running
from the distributer to the spark plugs is shown by Fig. 12 on Page 35.
"The neatest and most desirable methods are those shown by the two
lower cuts where the wires are run through tubes, the leads to the
plugs leaving at the side of the tube. The magneto distributed is
shown at the left of the diagrams.

In regard to the gear ratios given in the table on Page 7Z it should

IGNITION, TIMING, ETC. 123

be mentioned that the relative speeds are only true for four cycle
motors. For two cycle motors the relative speeds for more than two
cylinders will be double those given in the table. This is due to the
fact that a two cycle motor cylinder gives twice as many impulses
in a given time as a four cycle.

With the magneto, coil and wiring installed we are now ready to
time the magneto in regard to the piston position in the cylinders.
This most important part of the installation will be taken up in detail
in the lattei part of Part XI under the sub-head "Timing Magnetos."

PART VIII

IGNITION TROUBLES— MAGNETO AND BATTERY

SYSTEMS

REPAIR— ADJUSTMENT— CARE

OF
HIGH AND LOW TENSION APPARATUS

This chapter is devoted to the repair and adjustment of the
ignition system by the simple means open to the operator
of automobiles and gas engines, and covers the routine of
attention necessary for the adjustment and care of high ten-
sion magnetos.

If electrical matters are not your forte, the ignition system
is a most likely point of failure; hence the first thing to do
when the engine unexpectedly refuses to give the regular
beat of its explosion, (the skip is quickly noticed)

124 IGNITION, TIMING, ETC. '

is to see whether you obtain a spark between the frame of
the machine and the insulating cap of each sparking plug
when the engine is turned by means of the starting handle
through one or two complete revolutions (of course with mix-
ture cut off and compression released where provision for
this is made in the machine).

When doing this connect one end of the copper of a thickly
insulated wire to the frame of the machine and place the
other end very close to the exposed binding screw or brass
cap of the spark plug; if you get a good spark you may be
almost sure that the ignition is not the cause of the stoppage.
If you cannot get a piece of insulated wire, a key or a spanner
will do as well, provided you are careful to avoid getting a
shock by keeping the metal of the spanner well pounded —
that is, in contact with the frame. If you get either a fat
spark or a strong shock, the ignition is probably all right. K
you greatly dread a shock, undo the high-tension wire, and,
holding it by the rubber insulation, try the high-tension
spark, which should be about J4 inch long in air and very
bright. Special terminals are made for the rapid disconnec-
tion of the high-tension wire for this purpose. There are,
however, five cases in which you will obtain a spark or a
shock, although the ignition is the cause of failure.

The first case is when the battery is practically empty,
but has had time to recover in a temporary manner owing
to the stoppage of the car. You will probably find that the
engine will re-start and only run a little way. The only cure
for this is to have a second battery, which should be switched
oh with a two-way switch.

The second case is when some one of the wires of the
system is making a bad connection or is partially broken.
In this case the running of the car will shake the broken or
loose parts asunder, whereas the stationary car may give
you a satisfactory spark. The quickest cure for this in the
long run is not to hunt for faults, but to tighten one by
one every binding screw and turn the handle again. If this
does not cure it, pull out one by one every wire in the cat

IGNITION, TIMING, ETC. 125

and replace them with your spare wires. The reason for
not hunting out the fault is that the break has probably oc-
curred within the thickness of the insulation itself, and is
not discoverable without instruments or, at any rate, a tedious
search.

The third case is when the two points of the spark gap
within the cylinder are too far apart, or have too much oil,
soot or moisture on them to allow a good fat spark to occur
within the cylinder. Remember that a spark does not occur
with the same ease in the compressed gas of the cylinder as
it does in the open air.

Fourth. — It is possible that the porcelain or mica insulator
of the sparking plug is cracked or allows the current to flow
through it. This is cured at once by inserting a spare plug.

Fifth. — If the high-pressure spark appears to be thin and
weedy, so that yon suspect it of not being hot enough to ignite
the gas within the cylinder when under compression, it is
probable that one of five things is the cause —

1. The battery has run down.

2. The trembler blade and its platinum contacts are out
of adjustment.

3. There is grease or oil upon the make-and-break spring,
if a non-trembler coil is in use.

4. The condenser has somehow become disconnected or
punctured.

5. The high-tension windings on the coil or the high-
tension wire have partly broken down their insulation.

Therefore, switch over to your spare battery; clean the
platinum points of your spring contact by rubbing a visiting
card between them or even by smoothing them out with a
very fine file and removing all filings very carefully. The
condenser trouble is not curable on the road, but you may
be able to run your engine slowly home if you allow the com-
pression cock to leak a little. If touring in remote parts it
is worth while to carry a spare coil or even to have a com-
plete stand-by ignition.

Damp. — ^Water is a conductor of electricity; therefore the

126 IGNITION, TIMING, ETC.

porcelain plug should be wiped after a damp or foggy run.
The rubber-covered wires where they approach the terminals
should also be kept dry. This will be found impossible if
there is any exposed braid or tape to get damp and to col-
lect and retain it. Therefore, remove the braid and tape from
the end of all wires for a length of about an inch close to the
terminals. Do not remove the braid from the entire length
of the wire, because it is a useful protection against breaking
and fretting, but dip the whole of the braided wire before
using it into a bath of melted paraffin wax, wiping off the
surplus.

Supposing that neither a spark nor a shock is obtained at
the spark plug of the cylinder which is misfiring, it is gener-
ally safe to look in turn for one of the following defects:

. (i.) The battery completely exhausted (try it with a volt-
meter which takes the full normal current, say I ampere).

(ii.) There is a disconnection or a break in a wire — exam-
ine first the high-tension wire as being the simpler. See also
that the switch has not accidentally been moved to the "off"
position. See that the lead lug in the battery is not broken.

(iii.) The platinum tip has fallen off from the trembler
blade or from the spring contact, or from the platinum-tipped
screw; or the entire trembler blade has come loose from its
clamp.

(iv.) One of the coils has completely broken down. If so,
the click of a spark is generally audible by putting one's ear
close to the coil-box.

In applying these various suggestions the reader is credit-
ed with a certain amount of acumen. Thus he will at once
surmise that if only one of four coils fails to give a good
spark it clearly cannot be the battery that has failed; indeed,
trouble in this case is not to be expected in any part which
is common to the whole four (;oils, as, for example, the ground
wire, or the switch, or the commutator, save at the one con-
tact corresponding to the one cylinder showing the faulty,
ignition.

IGNITION, TIMING, ETC. 127

Cleaning Sooty Plugs.

With a two, thr^ or four-cylinder motor, it is quite pos-
sible to clean a sooty ignition plug without removing it from
the cylinder. The "modus operandi" is as follows: Detach
the high-tension wire from the misbehaving plug, open the
compression cock of its cylinder, and run the engine on the
other cylinders. Then hold the terminal of the detached
wire, being very careful not to touch the metal part with
the fingers, a very short distance off the end of the plug,
so that the spark jumps to the latter. The wire should be
held by the insulated part at least two inches from the bared
terminal. At first the cylinder will be heard to be missing,
but very quickly the reverse will be the case, and the dirty
plug will be found to have cleaned itself, as to all intents
and purposes a spark gap is established. Then switch off,
shut your compression cock, attach your wire again, and
start up.

How to True Up the Contact Screw.

In devising a jig for trembler screw points, the simplest
possible form, if there is no difficulty in getting either a
"tap" which will fit the trembler screw, or in cutting a tap
to do so, all that is necessary for the trembler screw device
is to drill and tap a hole through a piece of J^-inch steel plate,
ground perfectly true on one face, and then harden the plate.
The hard, flat face acts as a guide for the file, insuring that
it travels truly in the same plane, and the fact that the
trembler screw is held by its own thread is a guarantee that
the face of the point is at right angles to the line of the screw.
This way of doing the point is the simplest, but supposing
the trembler screw cannot have its thread matched without
trouble and expense, the jig illustrated in Fig. i obviates any
difficulty in this direction. It consists simply of a piece
of cast steel bar, bent round as shown^ and having the face
marked D ground quite flat. Through the center of this
portion of the bent steel a hole is drilled, which is exactly
the size of the outside of the trembler screw, so that it will

128

IGNITION, TIMING, ETC.

just push in from the under side easily. In the illustration
a slice has been cut out in front of the trembler screw A so
that it can be seen. Exactly opposite this hole in the other
arm of the bend, a second hole is drilled and tapped with any
convenient thread. Through this hole the round-ended set
screw B is inserted, its rounded end bearing* beneath the
milled end of the trembler screw. The steel bend and the
screw B should both be hardened. To use this jig the

/<k:/.

Jig for filing trembler screw pc^ts oortectty.
fL, trenbler screw. C, platiiraiii point.

B, adjisUiig screw acting as a stop. D, lM(rdened<9at fo^«.

trembler screw is inserted, and the lower set screw B run up
until the contact point C can just be seen, on glancing along
the face D, to be sufficiently above that face to clean up quite
flat. A fine flat file then steadied along the true face D will
complete the operation, and a perfectly level surface will be
obtained for the point C.

Truing Up the Blade Contact.

The jig for the trembler blades illustrated in Fig. 2 consists
of a cruciform base, the central portion of which is bored and
screwed to receive the circular table A. This table, which is
shown separately in the left-hand corner with its shank in
section, is made with a buttress thread as shown, and prefer-
ably its edges should be knurled or milled. Along one diam-
eter of the base, and equidistant from the center of the table

IGNITION, TIMING, ETC.

129

A, are the screwed studs D D, which pass through holes in
the two clips C C. These clips are as shown, and consist
simply of two metal strips about 3/J inch wide and i^ inch
thick, bent over at the one end, and ground flat on the down-
turned face opposed to the top of the table A at the other.
Along the other diameter the studs or stops B B are fixed,
these being screwed into the base and made from hard steel.
The upper faces of these studs B B must be perfectly level,
and exactly the same height from the base plate.

Pmpective plan view of jig for filing the points of trembler blades flat* '

A, adjustable table with buttress threaded D D, studs and nuts for

shank. tightening clips.

I^B, hazd steel studs for grinding the file, E, trembler blade.

C C, dips luddiug blade to table. F, platinum point..

The method of procedure is as follows : The trembler blade
E is laid down on the table A with the platinum point F
upwards. The clips C C are slipped over, so that the trembler
blade is between the lower faces of the clips and the table
top, but the nuts on the studs D D are left quite slack. A
straight-edge is then held across the faces B B, and the table
screwed up until the point F comes into contact with it. The
straight-edge is removed and the table taken up just a shade
more, according to how much has to be removed from the
platinum point F. The nuts on the studs D D are then tight-
ened down gently, when the blade is gripped firmly against

130 IGNITION, TIMING, ETC.

the surface of the table; and, moreover, since the table has a
buttress-threaded shank, the pressure locks the table very
securely in position. A fine file is then run across the studs
B B, with the result that the point F is made quite flat and
true with the blade in both directions.

Two steel plates, identical in shape, which can be clamped
together by a pair of thumbscrews, and having a ^-inch hole
drilled completely through the two, make an excellent jig
for holding the end of the trembler blade when filing the
hole to secure coincident setting of the points, this obviating
straining or bending.

Adjusting Contact Breaker Screws.

In adjusting the contact breaker screws when the contact
breaker is of the positive make-and-break type, care should
always be taken to see that the small locking screw, which
is provided in the split end of the screw-supporting pillar, is
properly locked after the adjustment is complete. Also, it
should be noticed whether locking up this screw affects the
adjustment of the contact screw, as this sometimes happens.
When the contact-making screw is not properly locked up,
the constant tapping on it of the trembler blade invariably
works it farther back, so that the adjustment does not keep
correct for any length of time, and, consequently, the annoy-
ance of misfiring is experienced very frequently.

A Cause of Irregular Firing.

Automobilists who have had experience with the old De
Dion type of contact maker have at some time or other been
troubled with irregular firing of the cylinder charge. This
has been put down to various causes, chief of which, no doubt,
has been a dirty contact between the platinum-pointed ad-
justing screw and the trembler blade. Other causes are loose
contacts, either at the plug wires or in the primary circuit,
dirty sparking plugs, nearly run-down battery, or a bad
mixture.

A not infrequent cause of trouble, however, is due to the
fact of the hole in the insulating quadrant of the contact

IGNITION, TIMING, ETC. 131

maker itself wearing slack or oval. The constant knocking
action of the notched cam on the trembler V-piece in time
causes an oval hole in the quadrant, and consequently the
correct action of the trembler is interfered with, and frequent
adjustments of the screw become absolutely necessary. When
the quadrant wears oval, it can be repaired by bushing it
with gunm'etal, but probably a more satisfactory method
would be to fit a new contact maker.

A more lasting quadrant would be one made entirely of
metal, a good hard gunmetal for preference, in which case
the adjusting screw terminal and connections would have to
be insulated by means of wood fiber or ebonite washers, and
there would be no necessity for a ground wire to be the
trembler terminal, as it would be constantly grounded through
the metal quadrant. This has been employed in certain cases,
and has given every satisfaction.

Trembler Contact Treatment.

When coil tremblers are behaving badly and require filing,
it may happen that a suitable file is not at hand. Then a
fairly good new surface can be obtained on the platinum end
of the screw by tapping it lightly with a small smooth-faced
hammer.

Loose Contacts and Faulty Firing.

A case is reported of a somewhat curious source of trouble
in connection with a two-cylinder engine. The engine sud-
denly refused to fire, and after much trouble and delay in
testing wires, etc., the fault was found to be ascribable to
a loose platinum tip in the trembler adjusting screw. At
first sight the platinum showed about one-sixteenth of an
inch clear of the end of the screw, but when tapped with a
hammer it disappeared entirely within the screw. The trouble
disappeared altogether when a new screw which had its plat-
inum point quite firm was fitted.

Trembler Fatigue.

It is pretty certain that ignition troubles are occasionally
caused by trembler fatigue. A case in point which once oc-

132 IGNITION, TIMING, ETC.

curred to a motoring authority would go to prove this. His
engine would drive for from forty to fifty miles perfectly,
running the car up all ordinary grades on its fourth speed;
but shortly after that distance had been covered, one of the
cylinders would begin to fire irregularly, and nothing would
improve it. Coil trouble was suggested, but he was loth to
believe this was at the root of the evil. The erring cylinder
would not drive the crankshaft alone, when the tremblers of
the other three cylinders were prevented from vibrating, al-
though either of these three would perform fairly well by
itself. No sooner was a new trembler fitted than the afore-
said weak cylinder ran merrily by itself, and the owner was
moved to replace the remaining three old tremblers with new
ones. These replacements greatly improved the firing and
pull of all the cylinders, wso that he was forced to believe that
the old tremblers, which had been in constant use for eight
months, wanted a rest.

Pitting of Trembler Contacts.

An annoying trouble, which in many cases is only a too
frequent occurrence, is the pitting of the platinum contact
on the trembler blade on high-speed trembler coils. The coil
will sometimes work fairly well at slow speeds, but gives
frequent missing when the engine is run at its normal rate,
or accelerated. On examination of the platinum points men-
tioned, it is found that the screw appears to have its end
melted in the form of a rough cone, like the carbon of an arc
lamp, while the platinum on the blade is eaten out cup-shaped
similar to the second carbon. It would therefore appear that
the metal was volatilized at one point and deposited on the
other. The probable reason for this may be the use of an
inferior platinum alloy, which has a comparatively low melt-
ing point, and is, therefore, more readily volatilized than pure
platinum. Pure platinum does not stand the rapid knocking
at the high speeds the trembler works at, and hence an alloy
of platinum and iridium is largely used, and this probably
follows the rule that the melting point of an alloy is lower
than that of either of its constituents.

IGNITION, TIMING, ETC. 133

In many cases frequent adjustments of the trembler screw
and trimming up of the points only cure the trouble for a
time, and lead to the conclusion that there is also some in-
herent fault in the coil itself.

Extra Grounding Wire.

"My 6^ H.P. single-C3'linder engine had always been a
trouble to start, but once going would run well," writes a
European motorist. "Complete rewiring, a new sparking plug,
shifting the non-trembler coil nearer to the engine, and a
general clean up of all the electrical fittings did not improve
matters. Finally, a second ground wire was attached to the
coil, ending at the blade of the contact breaker, and the
engine now starts without hesitation. The question now is,
Why was the first ground wire ineffective? It was a good
wire from the coil to a bolt holding the engine to the frame
of the car. The platinum-tipped screw is insulated, but the
trembler blade is attached to a metal segment moving about
the half-time shaft as usual. The only explanation I can
give is that the thick oil from the crankcase proved an in-
sulator, a film of this lying around the half-time shaft between
it and the metal segment. While the engine was at rest this
oil m.ore or less set hard. Upon trying to start the engine,
it was necessary, by a long period of starting handle exercise,
to wear through this film of oil until the one metal surface
of the half-time shaft rubbed against the other metal surface
of the segment. This has now been saved by giving an
alternative path direct from the blade to the coil."

The Trembler Coil.

Many motorists would be glad to have an explanation of
the reason why a trembler coil is necessary with a wipe con-
tact, and the difference between an ordinary coil without and
the coil with a trembler. To summarize the reason, it is
necessary to break up the primary circuit of the coil rapidly —
that is, the current which flows from the source of electrical
energy through the coil. This interrupts the lines of the
magnetic field, and intensifies the power of the induced curr

134 IGNITION, TIMING, ETC.

rent, for the quicker the make and break at the trembler, the
more effective is the spark, or, rather, the shower of sparks,
at the plug, such a shower being much hotter than those
of lesser density produced by a slow vibrating trembler. That
is why, as a rule, the magnetic trembler is much more effec-
tive than the mechanical trembler, for the latter cannot work
up to the speed of the former.

A Cause of Misfiring.

An engine, after being in use for some time, will often
misfire, and the cause be difficult to ascertain. Frequently
the trouble is one which does not occur with a new engine.
If the contact breaker is of the make-and-break type, the
bearing of the contact maker may have worn and the current
find difficulty in reaching "earth." To obviate this, a stranded
wire, which need not be insulated, may be led from some
part of the motor to the screw which holds the trembler blade
in place. Then the current travels directly from the trembler
to the earth without having to go through any sliding joints,
etc. In a wipe contact maker, it will be often found that
the brass is worn flush, or lower than the insulation, the
result being that the wiping blade jumps the brass at high
speeds. The insulation can easily be removed near the brass,
which will cause it to operate as before. Contact breakers of
this type should always be oiled, as it prevents the wiping
blade carrying the insulation op to the brass, which it fre-
quently does owing to its wiping action, the result being mis-
firing at high speeds. Again, misfiring such as this is often
due to the wiping blade having lost its vStiffness, and not
bearing sufficiently hard upon the contact breaker cam, which
may have worn as well.

Misfiring Through Defective Insulation.

Much annoyance is often caused to the user of a motor car
by occasional misfiring which he finds a difficulty in locating.
We cite a case of this kind, where for a time the engine would
run perfectly, and then most unaccountably commence to mis-
fire. This alternated with periods of regular running and

IGNITION, TIMING, ETC. 135

irregular running. A thorough examination revealed no de-
fects — ^the battery was fully charged, coil worked perfectly,
and the contact maker made good contact — ^but still, as stated
above, trouble was experienced repeatedly. It was noticed,
however, on turning down the front of the coil box, that the
high-tension wire of one of the coils was brought very close
to the low-tension wire of the other, and the owner found
that, instead of this high-tension wire being thoroughly pro-
tected by its insulation, at intervals a spark would leap through
the insulation to the low-tension terminal before mentioned,
and a misfire thus be caused in one of the cylinders. Re-
moving the wire to a distance of about half an inch from
the other terminal immediately corrected the fault, and no
further trouble occurred.

In such cases of misfiring it is always advisable to inspect
all wires which touch a metallic part of the frame, as, owing
to the vibration of the engine, the cause may be at these
points.

Marks on French Induction Coil Terminals.

The marks upon induction coils of French manufacture are
not understood by a great many users, and therefore an ex-
planation of them may be of interest. There are usually three
terminal screws upon the coil for a single-cylinder engine,
and these are marked P, M and B ; P and M usually being at
the side of the coil at the top, and B either directly at the
bottom or lower down on the side. The terminal marked P
is connected to the positive terminal of the storage battery
by an insulated wire into which the contact breaker is inter-
posed. There are, of course, many variations in the wiring
of the connections to the coil, and the one given herewith is
only one of them. The terminal M, which, by the way, on
some French coils is also marked V, is connected to some
metallic part of the frame on the car, or to the engine itself,
and forms an earth or ground return to the negative ter-
minal of the battery, a further piece of wire being connected
from this terminal to the framework to complete the circuit.

136 IGNITION, TIMING, ETC.

The terminal B is the one to which the high-tension wire
connecting up to the phig should be attached.

Numbering the Coil.
On three and four-cylinder engines fitted with trembler
coils, it is alwjiys well to take an early opportunity of verify-
ing the trembler for each cylinder. For instance, assume that
a four-cylinder engine is missing on one or two cylinders.
The bad cylinder is ascertained by holding down the trem-
bler blades and making the engine run on one cylinder at a
time. When we come to the bad one, the engine stops un-
less the other blades are quickly released. Despite this we
find that all four tremblers are buzzing merrily in turn, and
apparently there is nothing wrong with them. It is there-
fore natural to assume that the plug is at fault, and the
question at once arises, which plug? There is nothing for
it but to unscrew them one by one, and to turn the engine
round to see if the one under examination is sparking out of
the cylinder. In the usual course of things it will be the last
plug one takes out which is found to be foul or otherwise at
fault. On the other hand, if we had known which buzzer be-
longed to each plug, we could have gone straight to the foul
plug and have cleaned it up or put in a new one without loss
of time. However, as we have got our four plugs out, we
might just as well count them off from the front. Call the
one nearest the radiator No. i. Turn the engine round slowly,
and when you see the plug on No. i sparking, go round to
the trembler coil and see which of the four tremblers is buzz-
ing. Then pencil on the trembler case opposite to this trembler
No. I. Continue the operation until you have numbered the
coil for all four cylinders. Of course, we know the engine
does not fire i, 2, 3, 4 backward, but that does not matter;
we only suggest numbering the coil so that it can at once
be seen which trembler' and which plug are connected, so
that in future, whenever there is a cylinder not firing, we can
safely assume, when we have played the usual four-finger ex-
ercise on the coil, that the plug on a certain cylinder is wrong.
We no longer need blunder through all four.

IGNITION, TIMING, ETC. 137

General Troubles with Coils.

Looseness of platinum screws in the bridges. — ^Whether
these are bound with a lock-nut or not, they offer resistance to
the primary current.

Armature rubbing against the guide screw. — ^This restricts
the speed of the armature. Allowance is made for this in some
armatures by making the hole in the armature through which
the binding screw passes slightly larger than the screw stem.

Shorting of the secondary current to the coil support angles
or ears, due to the screws which hold the angles to the case
being too long and projecting inside.

In the case of four-cylinder coils (not waxed in entirely)
the ebonite top breaks away, owing to the screws which are
passed through the case into the ebonite top chipping out
pieces of ebonite, and so losing their hold of the top. This
is very often caused by the windings getting loose, and may
be caused by a jar to the coil.

Breaking of the primary wire between the communication
screws on the ebonite top and the terminals, and between the
communication screw and the bobbin itself.
^ Breaking of the flex wire between the bobbin (high tension)
and the terminal.

Internal switch troubles, due to wax entering the switch and
greasing the metal contacts.

Buttons on the armatures (which draw down the platinum
blade) getting loose and causing erratic striking of the platinum
blade. In the case of some distributer coils this may be the
cause of knocking in the engine.

Button of the armature shorting on the platinum screw.

Stiffness of the distributer armatures — ^in those cases where
it is of springy material and has no spring underneath to help
its return movement. This stiffness causes misfiring at high
engine speeds.

Many owners have had cases of coils bubbling the wax out.
This has been in most cases where ordinary coils have been
used for distributer purposes. They have noticed also that
with certain distributer coils with the bobbins waxed sepa-

138 IGNITION, TIMING, ETC.

rately all the insulation off the bobbin melted down to the
bottom of the box. This probably was due to the coil being
placed inside the bonnet near the engine.

In large heavy two, three and four-cylinder coils the wooden
cases have split, especially where angles are screwed to the
wood. As an opposite example to this, the case is cited of a
four-cylinder coil where the wood of the case and front flap
was half an inch thick. It looked a very substantial coil, and
would probably stand rough usage. The top had hinges, and
front flap hinges were also much stronger than usual. Where
flaps in covered-in coils are used the hinges are often loose.
The same applies to the top lids. This is accounted for by
the thin wood used in the case construction, which necessi-
tates small screws being used to screw on the hinges.

Commutator Short Circuiting.

Good as rolling contact commutators undoubtedly are, yet
nevertheless trouble may arise from them and within them
which the automobilist may be long in diagnosing if he has
not been informed that its happening is within the bounds of
possibility. After considerable use, the friction of the roller
over the metal contacts has the effect of wearing off small
particles of the metal and gradually laying these on the fiber
ring in the form of an embedded train, which will ultimately
connect one contact with the other, so that the current will
short all round, and whether two or four cylinders are
served, current will pass to all the sparking plugs at once.
If this has happened, the only thing to do is to detach the
fiber ring and scrape the inlaid metal from its surface. These
remarks apply with even more force to the commutators made
on similar lines, but which have a rubbing in lieu of a rolling
contact.

A Mysterious Squeaking Noise.

Sometimes a motor will develop a mysterious squeak when
running, and this often takes a good deal of locating. Many
motors are fitted with the wipe type of contact maker, and
\t is well to look to the wiper blade and the disk on which

IGNITION, TIMING, ETC.

139

It rubs for the source of the squeak. If the disk is allowed to
get dry, a most distressing noise is caused by the rubbing of
the steel wiper piece on the fiber of the disk or by the bearing
of the roller on the wiper arm when the latter is rotated. A
spot or two of ordinary lubricating oil will effectually cure
the trouble.

Adjusting Commutator Chain Drive.

If a chain-driven commutator upon the dashboard is used,
it should be remembered that a great deal of difficulty will
be experienced in getting the chain correctly replaced if it is
taken off for any purpose. Of course, where a spur gear is
employed to drive the commiitator, it is perfectly easy to
mark one tooth and the bottom of the two opposite teeth into

which it engages, thus insuring correct timing; but with a
chain drive it is impossible simply to mark two teeth alone.
This may be done to a certain extent with satisfaction, how-
ever, by marking the rim of the wheel on the center line; it
then becomes a matter of the eye in replacing the chain, and
also one of memory to insure the marks being in correct posi-
tion, that is, both marks should be at the bottom or top of
the wheel, as originally placed when they were indicated. Ot\,
writer suggests pointers being attached to convenient parts,
the marks on the chain wheel being brought opposite to
these. In any case, it will, of course, be necessary to ascertain
roughly the relative position of the crankshaft to the cam-
shaft. Unless this is done, it is quite possible to get the set-

140 IGNITION, TIMING, ETC.

ting incorrect., as while one wheel may be in position correctly,
the other may be a revolution before or behind it.

Twisting Temporary Connections.

In making a temporary electrical connection, the stranded
wires should be twisted up as solid as possible, and the loop
formed by turning the wire from left to right. When so made,
the loop closes in under the twisting action of the screw when
tightening up the connection. If the loop be made in the
opposite direction, this same action spreads the wire, and a
bad connection results.

Contact Breaker and Commutator.

The terms contact breaker and commutator are at present
being very loosely used in connection with automobilingj
simply on account of their functions not being definitely and
clearly understood. To all intents and purposes, both serve
the same purpose, which is that of an automatic switch com-
pleting the circuit of an electric current at a given time. The
contact breaker, whether it be of the spring blade or of the
wiping contact type, is used in connection with single-cylinder
engines only, while the commutator is used on multi-cylinder
engines, though its type and design may be precisely similar
to that of the wiping contact breaker on the single-cylinder
engine. The very word "commutator" should be sufficiently
expressive to prevent this error, as its meaning clearly shows
that its mission is to "commute," or to exchange, the current
from one path to another — that is, of course, from one cylinder
to another. It could only be a contact breaker when each
cylinder was supplied with a separate source of electrical en-
ergy, and with a separate coil, though when the common
source of supply is from a single storage battery, notwith-
standing that it traverses a separate coil for each cylinder,
it then becomes a commutator.

Multi-Cylinder Ignition Timing.

There are still a few makers of four-cylinder engines who
adhere to make-and-break ignition contacts as their standard.

IGNITION, TIMING, ETC. 1^'

and when perfectly adjusted and tuned up, this ignition is
quite as satisfactory as the trembler coil and wipe contact;
but when the slightest derangement occurs, the trouble is
difficult to locate, and often inexplicable. Presupposing that
all the platinum contacts are in good condition, and that each
cylinder is firing in its turn, it is yet quite possible that any-
thing but the best results are being obtained. The defect
arises solely from faulty ignition timing, due to the fact that
the points of the platinum-tipped screws and blades are riot
all equally adjusted. Thus, if we suppose our four tremblers
to be adjusted with No. i set of points i millimeter apart, No.

2 set 1.5 mm.. No. 3 set 1.4 mm., and No. 4 set 1.2 mm., the
cam having a 3 mm. eccentricity, each and every trembler will
give a spark at its full power ; but if we suppose that trembler
No. I is firing accurately, No. 2 is firing late, No. 3 late also
but earlier than No. 2, No. 4 earlier than either No. 2 or No.

3 but later than the correct No. i, the terms late or early being,
of course, relative to the position of the piston. Thus, in
each cylinder the mixture is being ignited at a different period,
with the result that, if No. i is being fired to its best ad-
vantage, the other three cylinders are not igniting efficiently,
the balance is gone, and considerable power is being lost Be-
yond this, where the firing is late, the combustion is not com-
pleted until after the exhaust valves have opened; the burn-
ing charge passes out in the form of a flash, extremely detri-
mental to the exhaust valve heads, and tending to overheat
the engine. In order that the best power may be obtained,
each cylinder must explode at relatively the same point, and,
therefore, when adjusting the make-and-break mechanism,
great care should be taken to see that exactly the same distance
separates the contact points.

On Preignition.

If preignition occurs, the engine should at once be stopped
and examination be made, as it is the chief cause of bent
connecting rods and broken crankshafts. The chief cause of
preigtiition is failure of water circulation. If this should be
suspected, it can be proved easily whether it is at fault by

142 IGNITION, TIMING, ETC.

placing the hand on the radiators and water-jacket.' If the
former are almost cold, while the cylinder jacket is exceeding-
ly hot, it will at once be understood that the pump is not work-
ing, or that there is an air-lock in the radiator piping. The
best way to deal with the failure in either of these cases is
to disconnect the outlet pipe from the pump and run the en-
gine. If the water is not discharged, it is obvious that the
pump is not working, while, on the other hand, if the water
tank is filled up while the engine is running, the air-lock Avill
probably be removed. Intermittent preignition is rather more
dangerous than persistent preignition, because the latter pulls
the engine up, while the former, coming at rare intervals, is
far more likely to do damage owing to the driver neglecting
to take precautions. A frequent cause of intermittent pre-
igtiition is a short circuit in the contact breaker wire. This
may be due either to the insulation of this wire becoming
chafed and short circuiting to "ground," or to an errant strand
at the contact breaker terminal, which frequently touches
some part of the motor and "shorts."

A third cause puzzled an experienced motorist for a long
time. The symptoms were of persistent preignition. The
pump was suspected and overhauled. The water was emptied
away and the tank refilled with cold, but before the car had
traveled a hundred yards the owner was forced to stop the
engine again, when, of course, he knew it was not the water
circulation, but something inside the cylinder. On removing
the valve caps, he found in the cylinder pieces of porcelain
which had broken off the inside of a porcelain sparking plug.
The central wire was held in place, and the plug was firing
quite normally. These pieces of porcelain naturally got ex^-
cessively hot, and c?used the preigtiition. The owner had
difficulty in getting rid of the pieces, but when removed pre-
ignition ceased.

Experiences: THe Value of Diagnosis.
The foregoing hints are the result of an interesting personal
experience, for faulty ignition resulted in a i6 H.P. car doing
but sixteen miles an hour on the level with its levers in the

IGNITION, TIMING, ETC. 143

45 m.p.h. position, and reduced to a miserable crawl up any-
thing like rising ground. The symptoms at first were pre-
cisely similar to those produced by the butterfly throttle valve
having become loose on its spindle, but this was after a time
proved to be an incorrect diagnosis. Next the governor was
attacked, but, being found in order, the operator looked to
the carbureter, rather expecting to find the gasolene supply
choked to a slight extent, but everything was found clear.
Between these investigations the car was run for a few miles,
so that a chart of times and distances would' have presented
the appearance of the toothed edge of a saw. However, the
operator tackled the ignition, and soon found a somewhat con-
siderable blowing at the ignition plates (this being tested by
pouring a little ofl around the spindles of the tweakers) and
considerable maladjustment. So much for the value of the-
ory and diagnosis. We do not deprecate the system of ob-
serving symptoms and following them out to the end, for
in a high percentage of cases the correct trouble is found,
but, as we have shown, on occasions one is apt to be led far
away from the actual ill. The ignition in the above case, by
the way, was low-tension magneto.

Insecure Terminals.

Cars are sometimes sent out with stranded connecting wires
just twisted round all the terminals, and there held by the
screwing up of the terminal screw. We would strongly ad-
vise any automobilist who finds his new car wired in this
careless and shiftless fashion to get proper terminals soldered
on without delay. It will save both time and tempe-* in the
long run. Moreover, from frequent bending round the ter-
minals, the stranded wire breaks, and one often gets nasty,
painful pricks in the fingers therefrom, which smart and
are sore for some time. There can be no sort of excuse for
sending out cars wired up in the slipshod way we have re-
ferred to. and the purchaser of a car should see that it is put
right*

144

IGNITION, TIMING, ETC.

Varnish for Electric Terminals.

Electric terminals which happen to be in such a position as
to be subjected to water or mud accumulating upon them
can be effectually prevented from possible short circuits by
painting them with a varnish composed of ordinary red sealing-
wax dissolved in a little gasolene. This varnish is made
by putting into a small bottle a quantity of small pieces of
sealing-wax, covering the latter with spirit and occasionally
shaking it. If the varnish should prove too thin, add a little
more wax or leave the cork out of the bottle until some of
the spirit has evaporated. If it is too thick, add sufficient spirit
to bring it down to the required consistency. In order to
prevent the varnish retaining the . brittleness of the sealing-
wax, a little linseed oil should be added. For those who do
not care to go to this trouble, a little melted paraffin-wax can
be used for the same purpose. The ordinary wax candle con-
tains paraffin-wax of sufficient quality to do this. Either of
these methods has been found as satisfactory as binding with
insulating tape.

Making Electric Connections.

A sketch of an excellent method of making electric con-
nections with the wire itself is g^ven herewith. The insula-

••— A

tion must be cut round at a convenient distance from the end,
1*4 inches to i>4 inches usually being the extreme amount re-
quired to make a connection. The stranded wires should be

IGNITION, TIMING, ETC. 145

twisted tightly together ; one or two of the wires, according to
the thickness of the strands of which the cable is composed,
are taken apart, as shown by A, the cable then being retwisted.
The wire should then be formed into a loop round a piece of
metal or the tenninal itself to a nice easy fit. The end of
the wire after forming the loop should lie parallel to the wire
at the beginning of the loop. The stranded wires which have
been taken apart are then used to bind the end of the loop
to the main body of the cable, the whole being soldered to-
gether with soft solder, which will flow easily without having
to use a great deal of heat. Particular care should be taken
to use resin, instead of hydrochloric acid reduced by dissolv-
ing zinc in it, or one of the many acid soldering fluids sold.
The objection to using such fluids is that they set up corrosion
and a chemical action at the joint, offering a high resistance
to the current, and there is no doubt that the same cause is
responsible for the ignition delays which some motorists ex-
perience with their cars.

Broken Plugs.

Sparking plugs with loose and leaky centers are by no means
uncommon ; but, treating the matter generally, very few people
try to discern and remedy the cause of the trouble. More often
than not the source of breakage can be traced to the festoons
of heavily-insulated wire pendant from the plug terminals,
or, where a neater and collective arrangement is employed,
to the tighter wires from the overhead stay to the plugs which
transmit the vibration to a considerable extent, resulting in
a breakage. There are two methods by which this transmitted
vibration can be obviated entirely, and the life of the plug
increased considerably. The one is to solder a fine coil of
flexible wire to the end of the high-tension cable, support the
cable firmly, and connect up the remaining end of the coil to
the plug terminal. In this manner the weight of the cable is
taken completely from the plug, and the fine coil is quite
incapable of transmitting the vibration.

A similar arrangement — one which performs the twofold
functions of spark gap and non-vibrating connection — is now

146 IGNITION, TIMING, ETC.

fitted to a number of engines. From each high-tension ter-
minal to the plug terminal is fitted a light brass or silver chain,
down which the current runs to the plug, having a minute
spark gap, as a rule, between each link; but all uncovered
sparking gaps are dangerous.

Spark Plug Troubles.

If the porcelain body of a sparking plug allows a loss of
compression at the packing gland, it is often only necessary
slightly to tighten up the hexagonal top of the circular por-
tion of the gland. After doing so, the plug wire should be
inspected to make sure that any slight rotation of the por-
celain does not affect the adjustment of the two points, other-
wise some misfiring or entire failure to fire the charge may
result. Another frequent cause of maladjustment of these
points when the plug is new is the screwing of the plug into
the cylinder. When the wire attached to the metal body of
the plug is hammered into position the thread is usually burred
slightly. This is restored to position when the plug is screwed
into the cylinder, and the wire is slightly moved in conse-
quence. When new a plug should be filed at the thread by
means of a triangular or fine half-round file, to remove the
bur. The plug should be screwed home, and then removed
and examined to see that the position of the wires is not
varied, after which the plug can be again screwed into the
cylinder, with the certainty that it will work correctly.

Warped Spark Plug Porcelain.

An Eastern motorist experienced a rather uncommon fail-
ure, accompanied by misfiring and a peculiar blowing noise in
one cylinder. As the valves had recently been ground-in in all
the cylinders, and no compression cocks were used, the trouble
could not be located until kerosene was squirted around
the valve caps and over the sparking plug. Turning the start-
ing handle round, it was found that gas blew past the por-
celain of the plug of the misfiring cylinder, though from what
one could see the plug was in proper condition. On remov-
ing the plug and taking it to pieces, the porcelain was found

IGNITION. TIMING, ETC. U7

to have warped considerably. There is no doubt that the por-
celain was not true in the first place, and from some unknown
cause the packing which secured it had loosened sufficiently
to allow an escape of gas past it, and so caused the trouble.

A Crack in the Porcelain.
When misfiring takes place, one usually in the first instance
examines the sparking plug, which is supposed to be the of-
fender, for deposits of sooty matter or lubricating oil. In a
number of cases it will be found that when the soot or oil
on the porcelain has been washed off with a little gasolene, and
the sparking points cleaned with fine emery or glass-paper, a
very good spark is seen between the points when the metallic
body of the plug is laid on the cylinder and the necessary con-
tacts made. Yet on replacing the plug it is found that the
misfiring in this particular cylinder is just as bad as ever.
This is a most deceptive and annoying trouble, which will
often be caused by a crack in the porcelain, either close to
the wire terminal and almost imperceptible, or it may be
somewhere inside the body of the plug, and therefore cannot
be seen. A good spark is produced in air, but under the
compression at working conditions the spark passes from the
center wire through the crack in the porcelain to the metallic
body of the plug, as this offers a relatively easier path than
that between the points and through the compressed mixture.
If the plug is held with the metal body in one hand and the
porcelain in the other, and a twisting action backward and
forward is applied while the plug is held close to the ear, a
slight gyrating sound will be heard if the break is inside the
body of the plug, which should be at once discarded in favor
of a sound one. A new porcelain may be fitted to the de-
fective plug if desired. Great care should be exercised in
putting in or taking out plugs from the cylinder, as there
is every chance that the porcelain may receive a slight tap
with a spanner and be broken, porcelain being extremely
brittle. This particularly applies in cases where plugs are
placed in deep recesses and a box or tube spanner is required
for insertion or removal.

148 IGNITION, timing; ETC.

MODERN BATTERY SYSTEMS.

By the "Modern Battery System" is meant that type of
ignition which comprises a single non-vibrating spark coil,
a high tension distributer and a circuit breaker as described
in Part II and illustrated diagramatically in Fig. 2 on page
44. Since only a single coil is used for any -number of cyl-
inders, the high tension distributer is necessary for distrib-
uting the spark to the various cylinders in the proper firing
order. To understand the principles of repair mentioned in
this section the reader should first consult the text in Part
II and follow the circuit diagram Fig. 2-3 carefully.

As the circuit breakers of the newer systems are almost
invariably of the platinum contact point variety with a
swinging arm and cam, the methods of repair are different
than in the older system in which a wiping roller contact is
used. The high tension distributer also introduces new prob-
lems not discussed under the older system. As with all high
tension apparatus, the breaker and distributer must be thor-
oughly protected against the entrance of moisture, oil or dust.
Attention must also be paid to the insulation and the support
of the wiring. Grounded contacts or connections must be
frequently examined at the point of connection with the
frame. Any looseness in the shafts, contact arms, control
rods or any tendency for the timer to "wabble" on the shaft
should be immediately corrected.

In cases of misfiring open the primary breaker box and
examine the platinum contact points. If they appear dirty
or oily clean them carefully with a lintless rag, taking care
that no threads remain in the box after cleaning. If they now
appear burnt, pitted, or have irregularities on their contact
faces, carefully file the opposing faces smooth and square
with a fine file. The finished surfaces should have a flat, even
bearing, for should they come together on an edge or corner
there will be heat generated, the resistance will be high, and
pitting will again proceed rapidly. After filing clean out
the metal filings and dust by means of a fine brush.

Now examine the levers, arms and cams for looseness or end
play. A small amount of lost motion will cause error in the
timing and will grow worse rapidly if not immediately re-
paired. Remove the levers from their shafts, clean thoroughly
and apply only a single drop of thin oil on the shaft by means
of a toothpick. Avoid overoiling or spattering oil on the con-

IGNITION, TIMING, ETC. 149

tact surfaces. A single oiling of this nature should be good
for 600 miles. Examine the springs that press the followers
or rollers on the revolving cam. See that they hold the fol-
lower firmly against the cam face, for these springs often
weaken and allow the follower to jump over the "high places"
on the cam and destroy the timing. When the engine misses
at high and runs well at low speeds it would be well to exam-
ine the spring tension.

Looseness in the timing lever connections that run from the
steering column to the timer will cause uneven running for
the reason that the lost motion will cause the spark to be
intermittently advanced and retarded. A defective dash
switch will also intermittently open and close the circuit and
cause misfiring.

After filing down the contact points make sure that they
are brought back to their proper relative position, that is, see
that the contact point in the adjusting screw is away from
the arm contact by the original clearance when the breaker
is fully open. If the full open clearance between the points
is not kept constant, the timing will be changed or misfiring
will result through imperfect contact. Usually the distance
between the points when fully open is about 1-64 inch or
equal to the thickness of a heavy visiting card.

If the engine still runs poorly it is evident that the timing
is wrong (providing the carburetor adjustment is all right).
As an example of proving the timing we will give the instruc-
tions issued for the Atwater-Kent breaker, a proof that will
apply to the majority of this class of breakers.

First, fully retard the spark lever and uncover the fly wheel
so that the timing marks on the wheel and the pointer can
be readily seen. Remove the cable from the spark plug in
cylinder No. 1 and have the end of the cable held about %
inch from the cylinder casting. Now turn fly wheel so that
the pointer is near the mark "No. 1 — T. C." and slowly rock
the wheel back and forth. A spark should appear between the
end of the cable and the cylinder casting at the moment that
the mark on the wheel passes the pointer, for at this point
the piston is at the upper end of the compression stroke. If
the spark occurs any distance on either side of this mark, the
timing is out and must be corrected. If the timing were cor-
rect before the contacts were filed, the chances ar/s that the
contact in the end of the adjusting screw is too far away from
the contact on the swinging arm or contact spring.

150 IGNITION, TIMING, ETC.

Turn the engine over until the contacts are wide open, and
remove one of the washers under the head of the contact
screw. Turn the screw so that the screw contact point tnoves
forward toward the arm contact point and until the two are
separated by approximately 1-64 inch. Try the timing again.
Should the timing still be out, examine the cam, shaft and
fastenings to see if anything has slipped or worn out of place.
Examine the points or teeth on the cam or the cam follower
and note whether the engaging surfaces appear worn.

When finally adjusted, the head of the adjusting screw
should be tight against the washers so that it will not work
loose. In the Atwater-Kent system it should be remembered
that the spark occurs at the instant the rider snaps back and
strikes the contact spring. See page 47, Fig. 3. For similar
adjustments on the Delco as installed in the Cadillac, see page
50, Fig. 8, and the text starting on page 52.

Before leaving the circuit breaker see that all of the wire
connections are tight and that the wires are not broken
through the rocking action of the timing lever.

Considerable trouble with the contact points can be avoided
by occasionally reversing the direction of the current through
the breaker. The current can be reversed by reversing the
wires at the battery so that the wire formerly on the positive
pole will be connected to the negative, or by reversing the
wires at the timer.

The high tension distributer should be cleaned out periodi-
cally as the smallest deposits of dirt or oil are sufficient to
short circuit the high tension current. Deposits of dirt are
most common in distributers that employ a rubbing contact
brush since the material rubbed oflf the brush collects in the
casing.

Should the engine stop suddenly or refuse to start, carefully
inspect the wiring for broken strands, abraded insulation, or
loose connections, or test the batteries if dry cells are used.
With a self-starting and lighting system, the lights are an in-
dex to the condition of the batteries and with proper ignition
apparatus it is possible to fire the engine long after the storage
cells fail to provide sufficient current for the lights, or when
the lamps' burn red. Naturally, a powerful coil with a good
voltage behind it will give a "fat" and hot spark, but this

IGNITION, TIMING, ETC. 151

may easily be offset to a certain extent by high compres-
sion. Th^ best practice is, then, to find by experiment the
most efficient position of the points, and to have a perma-
nent guide in the form of a gauge to set them up to. This
gauge may be a piece of sheet metal, and once obtained should
be religiously preserved.

Screwing in New Plugs.

Before screwing a new sparking plug into its place in
the cylinder head, always file down to the thread level both
in the groove and over the diameter the small hump which
is usually raised ,by the fixing of the sparking wire to the
metallic body of the plug; otherwise, although the points are
correctly spaced before screwing the plug into its place, there
is a tendency to alter their relative positions on screwing in,
and thus to cause failure in working. Always make sure that
the center wire is fixed properly, otherwise if it can be moved
readily the probability is that there is a bad connection, and
trouble with misfiring will follow. Before putting in a plug,
if the screw thread is lubricated with graphite or blacklead,
it is more easily screwed in or out.

Periodical Examination of Spark Plugs.

Because your engine starts up well first time round every
day, runs well to the ear, and seems to pull all right, do not
leave your sparking plugs unexamined from one month's end
to the other. You will insure the extra touches of speed and
power if you take these fittings out from time to time, say
once a fortnight, and scrape all the hard carbon off them,
cleaning them finally and nicely with a stiff toothbrush dipped
in gasolene. Engines with high compression will be improved
by this little attention.

Simple Test for Short Circuits and Broken Circuits.

When troubles occur in connection with ignition, there is
usually no method other than minute examination adopted for
investigating the condition of the wiring in the primary cir-
cuit. Short circuits to the frame owing to chafing or cut-

152 IGNITION, TIMING, ETC.

ting of insulation, and total disconnection owing to hidden
breakages in the wire itself, are not unknown, so a simple
means of testing for these faults may be of value. When
batteries run down rapidly while at rest, the blame is put
upon the cells themselves, but in reality it may be due to
defective insulation of the primary circuit.

The instruments required for the test are usually ready
to hand, these being simply a storage battery and a reliable
voltmeter of fair size. On a peculiarity of the former the
value of the test depends, for it is found that when a battery
is on open circuit it gives a higher reading than when a cur-
rent is flowing. The following actual readings illustrate this :
Current flowing in primary circuit, o, i, 2, 3 amperes; readings
of voltmeter, 4.05, 3.97, 3.92, 3.87 volts respectively. These
readings can be taken advantage of for testing purposes as
indicated below.

Short Circuit to Frame.

To test for a short circuit to the frame proceed as follows:
Connect a voltmeter across the terminals of the battery (ac-

A, accumulator. V, voltmeter.

F, frame wire or eartlu W, wipe contact maker.

S» twitch.

cumulator) ; leave the switch open, and set the wipe or con-
tact maker so that metallic contact is not made (see sketch).
Take a reading of the voltmeter. Now close the switch, watch-
ing the voltmeter carefully while this is done. If the needle
moves, showing a lower reading, it conclusively shows that
a current is flowing through the switch; but since there is
no connection at the wipe or contact maker (contact breaker,
so called), this can only be due to a leakage.

IGNITION, TIMING, ETC. 153

Ignition by Batteries — Causes of Failure.

Below, under the four heads of Sources of Current, Induc-
tion Coil, Wiring, and Commutator will be found nearly
every cause for ignition failure, partial or entire. Although
the list is somewhat awe-inspiring as to length, every source
of trouble enumerated can be avoided by care and cleanliness.

Sources of Current, Storage or Dry Batteries. — Loose or
dirty terminal or terminal screw. Whole or partial discharge
of storage or dry battery. Internal short circuit. External
short circuit. Connection between plates or elements of the
battery broken. Loss of electrolyte fluid. Perforated leaky
casing

Induction Coil. — Loose or dirty terminal or terminal screw.
Wire separated from terminal at inner end. Broken or fused
wire in coil (rare). Faulty adjustment of trembler. Pitted
or unevenly burnt platinum contacts. Insufficient insulation
of terminal from which high-tension plug wire leads.

Wiring. — Bared wire. Wire insulation destroyed by oil.
Wire fractured within insulation. Loose wire attachment.
Terminal unscrewed or dirty. Broken earth wire. Bad or
dirty contact of earth wire. Mistake in remaking connections,
Poor or faulty insulation of sparking plug.

Commutator, with Trembler or Blades. — Faulty adjustment
of platinum contact screws. Too far apart — misses. Too near
— premature ignition. Bad or burnt-out platinum contacts.
Dirty or loose unsoldered platinum contacts. Faulty insula-
tion of platinum-pointed screw. Greasy, split or loose ignition
plate. Horizontal play. Broken trembler or contact blade. •

Rotary Commutator. — Contact roller arm loose on spindle.
Roller worn on circumference or center. Roller spindle worn.
Contact ring worn in ridges, either fiber or metal. Too little
lubrication. Too much lubrication with thick grease. Carbon
deposit on contacts if contact maker runs dry.

Sparking Plug. — Fouling by oil, carbonization. Fracture
of porcelain insulation. Loose porcelain. Shorting through
mica insulation by penetration of grease. Sparking points
too remote or too near. Damp, greasy or dirty porcelain.

154 IGNITION, TIMING, ETC.

HIGH TENSION MAGNETO TROUBLES

In general, the best advice that we can give the operator of an auto-
mobile or engine, is to leave any extended repairs of a high tension
magneto to the service station of the maker, or to a firm making mag-
neto repairs a specialty. In emergencies he may attempt minor repairs
but the results are seldom satisfactory as it is an easy matter to ruin
this delicate instrument through the neglect of the simplest precau-
tions. Fortunately for the operator, the high tension magneto seldom
gets out of order to such an extent that a general dissection is neces-
sary, and hence it is well to go over every other part of the ignition
thoroughly before setting the trouble on the magneto.

When the motor misfires or refuses to start, examine the plugs and
wiring first, as they are the most frequent sources of trouble, not for-
getting the carbureter. If the plugs are clean see that the spark points
are not too far apart from the warping or burning action of the gas.
The gap between the points should not exceed 1/64 inch, as high com-
pressions reduce the jumping ability of the current. Due to the in-
tense heat of the spark, small beads of metal often form on the
spark points. These short circuit the spark gap and should be care-
fully filed away and the gap readjusted. Examine the porcelain of
the plug for cracks and if oily or sooty clean with a tooth brush
dipped in gasoline. Cracked plugs should be replaced with new.

The first point to examine on the magneto proper is the circuit
breaker box and points. If the platinum points are dirty, or if there
are evidences of oil in the breaker box, clean thoroughly with gasoline.
Should the points be burnt so that they have an uneven bearing sur-
face, or have small beads of metal attached at the point of contact,
they should be very carefully filed to a flat, even bearing, so that they
have a full contact over their entire surface. This operation should
be performed with a very fine file, care being taken to have the con-
tacting surfaces absolutely square with one another.

In the course of time the points wear down because of the inces-
sant hammering and leave too great a gap between the stationary and
moving contacts. This can be adjusted by means of the adjusting
screw which carries the stationary point. This should be turned for-
ward until the gap is not greater than 1/64 inch when the points are
fully opened. A gauge for this adjustment is furnished with some
makes of magnetos. After this adjustment is completed all lock
nuts should be tightened up so as to prevent the screw from jarring
back and out of position.

Irregular firing can only be caused by the improper adjustment of
the breaker (when the magneto is at fault), and when the points have
been cleaned and adjusted attention should be paid to the condition
of the rocker lever, roller and other moving parts of the breaker

IGNITION, TIMING, ETC, 155

mechanism. If the rocker lever has become jammed, thoroughly clean
the bearings and axle by rubbing them slightly with fine emery paper,
and then very slightly oil. In this connection it may be said that
great care should be exercised in oiling a magneto as an excess of
oil in the breaker box not only gums the mechanism but also prevents
good electrical contact between the breaker points. If the breaker
arm has been jammed make sure that it is not bent so that the con-
tact points meet in an off center position.

If there are any current collection brushes in the breaker box see
that they are thoroughly clean and that the spring presses the brush
firmly against the corresponding contact point. A weak spring or
dirty brush will interrupt the flow of current in the primary circuit
of the magneto. Clean arid tighten all wiring connection. Irregular
firing is often caused by looseness in the levers and rods leading from
the spark lever on the steering wheel up to the timing lever on the
breaker box. Back lash or play in the driving gears or chain produce
the same result. Thoroughly clean the high tension brush and holder
that rests on the high tension collector ring, generally located at the
rear end of armature. Clean ring and ring insulation with gasoline.

A dirty distributer or distributer brush is the cause of internal
short circuits among the sectors to which the plug leads are attached.
This produces irregular running among the cylinders as the deposits
of dirt cause false connections between the different sectors and there-
fore intermittently connect the cylinders in the wrong order. Re-
move brush and thoroughly clean it and the distributer with a lint-
less rag dipped in gasoline. See that all high tension connections are
free from moisture. Examine all wiring for abraded insulation, broken
wires and loose connections, especially at a point near the circuit
breaker where the rocking of the timing lever is likely to fracture the
primary wires. See that the grounding wires are in good contact
with the frame, and that the dash switch is in order.

Should irregular firing still persist, it is probable that the timing is
at fault, or that the leads to the plugs are connected in the wrong
order. This is very likely to be the trouble if the engine has just been
overhauled or repaired. When replacing the magneto after a gen-
eral overhaul, great care should be taken to mesh the teeth of the
magneto gears at exactly the same place that they formerly occupied,
for the difference of one tooth from the correct position will greatly
distort the timing. The gear teeth should always be marked before
removing the magneto so that there will be no trouble in replacing.
This can be done by marking a tooth on one gear with a center punch,
and then marking the two teeth (of the other gear) that lie on either
side of the first tooth. See that the keyways in the gears and couplings

156 IGNITION, TIMING, ETC.

are intact. Consult one of our wiring diagrams for connecting up the
spark plug leads.

Should there be no marks on the gears, consult the directions for
timing magnetos contained in Part XI, remembering that the circuit
breaker contacts should just barely begin to open when the piston
to be fixed is about ^ inch from the end of the compression stroke.
The order in which the leads are connected depends on the firing order
of the motor, and the direction in which the distributer brush rotates.
This subject is also covered in Part XI.

The magnets of a standard make of magneto do not weaken to any
extent with age, even after several years of service. Should every-
thing eUe be tried as outlined above, test for weak magnets by remov-
ing the magneto from the engine and running it at a speed of about
150 revolutions per minute. At this speed there should be an almost
continuous spark discharge across the safety gap, if the magnets, arma-
ture, and condenser are in proper order. If the discharge is weak
or intermittent it is evident that there is some internal disorder, and
the chances are that the trouble lies in the magnets.

Owing to the many peculiarities of the permanent magnetic circuit
we would not advise the amateur repairman to remove the magnets
unless in the case of an emergency, but with care and attention to
the following instructions it can be accomplished without harm, or at
least permanent hurt to the machine. Go at the job gently, remember-
ing that you are not handling a locomotive, but a machine that is more
delicate than the average clock, and remember above all things that
each part, screw and washer must be replaced in exactly the same
place^it originally occupied. Measurements on a magneto are not in
l/16ths but in ten-thousandths of an inch.

Due to the close running clearance of the armature in the^ tuniiel,
which is in the nature of 0.0015 inch, the alignment of the bearings and
rotating parts must be as perfect as possible. Any error in this re-
spect will cause the armature to strike the pole pieces or permanently
bind in such a way that the entire magneto will be ruined if much
force is applied to the driving shaft before the trouble is corrected.
This small running clearance is necessary to preserve the strength
of the magnetic field. Matters are further complicated by the pull of
the magnets on the armature which tend to take up any slack in the
bearings and bind the armature on the pole pieces.

When removed from the magneto the magnets will rapidly lose their
strength if not carefully handled, owing principally to the great in-
crease of resistance offered to the magnetic force by the removal of
the iron circuit that formerly existed between the legs of the magnets.
If not provided for, the magnetism will generally decrease at least
50 per cent in one hour after the removal. A complete iron circuit

IGNITION, TIMING, ETC. 157

between the poles of the magnet must be provided if the magnets are
to hold their strength. The spark obtained is directly proportional to
the strength of the magnets and to the speed of the armature, a strong
field causing the instrument to generate the current at comparatively
low speeds.

When the magnets are removed from the instrument for remagnet-
izing, or for any other reason, never fail to place a soft iron bar or
"keeper" across the two legs of the magnet on the instant that the
magnet is removed, and keep the bar in this position as long as the
magnets are off of the machine. When lying on the bench take care
not to jar them unnecessarily by dropping them, or by striking with
metallic parts. Do not pile the magnets one on the other, as the crossed
and stray magnetic fields will tend to decrease the strength. Vibra-
tion, heat and external magnetic fields are detrimental ^o the perma-
nance of the magnets. Better not remove them at all unless it is abso-
lutely necessary.

Methods of remagnetizing are given in an article on page 227.

When replacing the magnets, after remagnetizing, be sure that the
magnets are replaced in exactly the same place on the machine that
they formerly occupied, and that the magnet legs of similar polarity
are replaced on the same side of the armature. The best method is
to mark the magnet poles and magneto frame so that there will be no
possibility of mistake. If dissimilar poles are placed on the same side
of the armature, the magnetic field will short circuit and decrease the
effective flux. Carefully clean the poles at the point where they fit
over the armature tunnel and screw them firmly into contact with the
pole pieces. Any space between the poles and the pole pieces will
decrease the spark and the life of the magnets. Do not place liners or
shims at this point.

Diflicult starting is more often due to improper timing than to weak
magnets, and you may almost be sure that this is the trouble when the
engine kicks on cranking with a retarded spark. In this case it will
be found that the circuit breaker opens and causes the spark to occur
long before the piston reaches the end of the compression stroke,
with the result that the piston and crank is driven backwards against
the normal direction of rotation. This of course means that the arma-
ture is too far advanced in regard to the piston. With the armature
retarded too far it is impossible to develop the full speed of the engine
even with a wide open throttle and excessive heat is developed at
moderate speeds even with the spark fully advanced. One test of this
condition is that the engine will not knock or hammer at moderate
speeds with the spark fully advanced.

It must be remembered that both the primary and high tension cur-
rent return from the coil, and from the spark plugs, to the magneto

158 IGNITION, TIMING, ETC,

through the magneto base, and therefore there must be good electrical
contact between the magneto frame and the frame of the engine (elec-
trically called a "Ground")- The current can both return through
the metallic contact of the magneto base and through the hold down
bolts used in fastening the magneto. Be sure that coats of paint and
paper liners do not interfere. If the grounded circuit is not complete
the magneto will not generate.

With the engine running at about 150 revolutions per minute there
will be almost a continuous discharge of sparks across the safety-
gap if there is a break or disconnection anywhere in the high tension
circuit. This may be caused by a disconnected wire running to the spark
plugs, or in transformer types may be caused by a break or discon-
nection in the high tension wire leading from the transformer to the
distributer of tjie magneto. A broken brush in the distributer or broken
connection from the collector ring brush will also cause a discharge
across the safety gap.

High tension magnetos should be thoroughly protected against the
entrance of moisture, or oil, for either are destructive to the insula-
tion. Owing to the small armature clearance, the rust produced by
moisture will soon weld the armature firmly to the pole pieces of the
magnets, with the result that the shaft will be twisted off, or other
serious injury willbe caused. While modern magnetos are supposed
to be waterproof, it is always better to be on the safe side and protect
them with a leather or sheet metal cover. This should be of non-mag-
netic material. If iron is used it will tend to short circuit the magnetic
field and reduce the spark.

When remagnetizing is tried, after the circuits and other parts have
been found clear from trouble, the trouble is undoubtedly due to the
derangement of the armature winding or to the condenser. If the
magneto is of the true high tension type it is almost impossible for
the amateur repair man to remedy the trouble, owing to the great
length of fine wire on the secondary winding and to the careful con-
struction of the condenser. It is far better in this case to return the
magneto to the makers for replacement or repair. In the case of a
transformer type where the armature winding consists of a few turns
of heavy wire or copper strip, repairs can often be made successfully
with the crudest equipment.

When removing the armature of any magneto take great care not
to spring the shaft and do not lay it where dust or moisture will col-
lect on the windings or core, A little rust or dirt will cause the arma-
ture to bind in the armature tunnel when replaced. A kink in the shaft
or a bunged up bearing will cause the armature to strike the pole pieces
or bind in the tunnel. Take care to place the bearings back into exactly
their original positions and use the same bolts in the same holes. If

^ IGNITION, TIMING, ETC, 159

there are dowel pins, drive them in gently before tightening the screws.

In oiling the magneto it is not necessary to use more than two or
three drops of oil per run of 500 miles on the main bearings. In some
types there is no oil required in the breaker box, but in any event never
use more than one drop at a time on the breaker lever and apply this
carefully with a tooth pick so that it will not get on the contact points.
Any light oil such as sewing machine oil may be used, but never cylin-
der oil. Gummy or carbonized oil on the breaker points will surely
cause misfiring.

In cleaning the magneto, start at the breaker box, clean the distribu-
tor, and then clean the high tension collector ring and brushes. A
soft rag, free from lint and moistened with gasoline, will remove
all ordinary dirt and oil. Should the mageto become wet, dry slowly at
a very moderate temperature (less than 150 degrees). Never in a hot
oven.

In the majority of cases the trouble will be found in the plugs or in
the wiring and these points should always be investigated first before
tampering with the magneto. The first places to look at on the mag-
neto are the breaker points and distributer.

SUMMARY OF TROUBLES AND REPAIR

Motor Stops Suddenly. Short circuit in low tension cable — Switch
jarred into closed position — Moisture or dirt in magneto — High ten-
sion lead loose in wire running from coil to magneto distributer — Short
circuit in high tension wire supports. Test for Primary Leak. Dis-
connect primary wire running from switch to circuit breaker and try
to start engine. If engine starts without trouble there is a leak in the
primary wire or trouble in the switch.

Misfiring. Dirty spark plugs — Cracked spark plugs — Spark gap of
plugs too great — Disconnected plug wire — Faulty wire insulation —
Loose wire connection in either primary or secondary — Poor mixture
from carbureter — Dirty or burnt contact points in circuit breaker —
Dirty distributer — Distributer brush makes poor contact — Breaker
brush makes poor contact — Collector rings or collector brush dirty-
Opening between breaker contacts worn or burnt so that the opening
is too great — Breaker arm stuck or loose — Swinging grounds between
wires and engine frame.

Starting Trouble. Spark plug gaps too great — Incorrect timing —
Carbureter trouble — Starting motor runs at too low speed due to ex-
hausted battery — Cylinders not primed — Circuit breaker stuck — Mois-
ture — Closed switch — Short circuit in primary wires or defective switch
— Disconnected plug.

Knocking. Spark advanced too far — Incorrect timing.

Instructions in regard to properly timing the magneto can be found
in Part XI, page 227.

PART IX
ELECTRIC STARTING AND LIGHTING

General. When using electricity as a medium for "cranking" thei
gasoline motor it is possible to use the current also for ignition and
lighting as well as for the electric horn and gear shift. The pos-
sibility of operating so many auxiliaries from the same source of power
naturally makes the electric self-starting system by far the most popu-
lar. In many cases an independent magneto is used and sometimes
in addition a third auxiliary, the dry cell system, is added to the igni-
tion system making the car entirely independent of any one system
for the ignition current.

Disregarding the ignition system for the time being, the self-
starting and lighting system is composed of the following principal
units:

(1) The generator for supplying the current for the cranking of
the car and the lighting system.

(2) The motor for spinning the motor. (Sometimes the genera-
tor and motor functions are supplied by a single unit.)

(3) Storage battery for storing current for the motor and lights
as well as for the horn and ignition.

There are four ways in which a single unit may act as both gen-
erator and motor. (1) A single armature, field and commutator may
give or receive current to or from the storage battery. (2) A unit
with a single field and armature may be provided with two commu-
tators and two independent windings on the armature, one winding
being for the generator while the remaining winding and commutator
is for motor service. (3) Two independent armatures, fields and com-
mutators may be contained in the same frame, the armatures being
mounted on the same shaft in tandem, they being electrically inde-
pendent of one another during the starting and generating periods.
(4) Instead of being in tandem the fields and armatures may be
mounted in the same casing but one above the other. (Double deck.)

When types (1) and (2) are acting as generators they are generally
driven by the engine through the timing gears. When operating as
motors they drive the engine either through a gear toothed fly-wheel
or by a silent chain to the crank-shaft. The driving pinion is so

160

IGNITION, TIMING, ETC, 161

arranged that it can be thrown in and out of mesh with the geared
fly-wheel by the starting pedal, the gear being normally out of mesh
when the engine is running under its own power.

Regulation of Generator Current. The faster the armature of a
generator rotates, the higher will be the voltage, and the greater will
be the current put through the storage battery. With a continually
fluctuating speed due to the variations of the engine it is evident
that some device must be provided that will limit the current sent
through the storage cells and at the same time prevent the storage
battery current from surging back through the generator when the
generator falls below the voltage of the battery.

In general there are four ways of limiting the current. (1) By pro-
viding the generator with a governor so that it cannot Exceed a cer-
tain speed. (2) By placing an automatically controlled resistance in
the generator circuit that will keep the current steady at any ordinary
speed of the generator. (3) Providing an automatic cut-out switch
that will open the circuit when the current exceeds or falls below-
certain points. (4) By inherent regulation of a specially wound gen-
erator in which the windings oppose one another and diminish the
output as the speed increases.

Double Unit System. There are several systems in which the gen-
erator and motor are entirely independent of one another and are
mounted in different parts of the chassis. The motor is series wound
while the generator is compound wound, the difference in winding
being due to the fact that a series winding gives greater "torque" or
pull while the compound winding tends to maintain a constant current.

The Cut Out.. A cut out is an automatic switch which opens the
generator circuit when the voltage of the generator falls below that of
the battery so that the current from the battery will not be discharged
back through the generator. This generally consists of an iron core
on which a double winding is placed. One winding which is connected
across the terminals of the generator consists of many turns of fine
wire, while the other coil consists of a few turns of heavy wire con-
nected in series with the circuit leading to the storage battery.

When the generator comes up to voltage, the fine wire coil mag-
netizes the bar so that the armature is drawn up causing the current
to flow into the battery through the switch. The main current now
flows through the heavy coil reinforcing the -magnetic effect of the
first coil.

Should the generator now fall in speed so that its voltage is less
than that of the battery, the current will be reversed in, direction
through the second coil which will therefore oppose the first coil,
demagnetize the iron core and allow the switch to be opened by the
tension of a spring connected to the armature.

162 IGNITION, TIMING, ETC.

Generating Speeds. All other conditions being constant, the speed
of a dynamo or generator determines the voltage, the voltage increas-
ing in almost direct proportion to the speed until the "saturation''
point of the generator is reached. To obtain the desired voltage it is
therefore necessary to have the generator run at a particular relation
to the normal running speed of the motor. Gearing the generator at
a high ratio allows the current to be developed at low engine speeds
but also causes trouble at high speeds due to the tendency of devel-
oping excessive voltages and currents.

The exact ratio of the gearing between generator and engine
depends of course on generating speed and the low limit speed of the
engine. Again in the systems where the generator also carries the

Conventional Starting and Lighting Circuit, in Which R is the Idling
Resistance, D-T-C-S-G is the Automatic Cut-Out, V is the Voltmeter
and A is the Ammeter.

NOTE I S is the series coil and G is the shunt coil of the cut-out,
the circuit being opened h^ the switch T at the point D.

HF and SP are respectively the shunt and series windings of the
generator. H is the single series winding of the motor.

primary circuit breaker and the high-tension distributer, the speed of
the generator must bear a definite relation to the crank-shaft speed
so that the breaker will cause the spark to occur in the cylinders at
the prpper time. Usually the generator gearing ratio runs from I to
I'/i times the crank-shaft speed. This corresponds to a car speed of
from 10 to 12 miles per hour.

Motor Speeds. To obtain the necessary torque to crank the motor,
the speed,of the motor, or the motor element of the motor-generator,
must be much higher than the generator, and hence the gearing ratio
must be higher in starting than in generating. This higher gear ratio
gives the motor a greater leverage on the engine so that it can be spun
under the most dilTicult conditions. In fact this leverage is so great

IGNITION, TIMING, ETC, 163

that the starting motor is usually capable of moving the whole car at
a low speed.

To obtain this reduction, and to save as many gears as possible it
is the common practice to gear the motor, or the motor end of the
motor-generator, to teeth cut in the periphery of the fly-wheel where
a reduction is to be had of from 8 to 1, to 10-1. The motor pinion
shaft is then provided with a second train of gears (usually encased in
the motor housing) with an additional reduction of from 2 to 1, or
3 to 1. (See (R) in Fig. 1.)

Considering a normal engine speed of 1,000 revolutions per minute
and a starting motor ratio of 30 to 1, it will be seen that the motot •* I JA^ ^
speed would reach a value of 30X1,000=30,000 revolutions per minute ^

if it were left permanently engaged with the fly-wheel teeth,. -This speed ^ . /s
of course would be entirely out of the question because of the mechan- •>'■ i-
ical stresses and the tren^endnu.^ y9 itflr'* ^''^^lorfff so that the motor
drive is always provided with some form of declutching mechanism
that liberates the motor from the engine at a certain speed.

Usually it is in the form of a clutch which engages as long as the
motor exerts a force on the engine, but when the engine exceeds the
speed of the motor and reduces this force to zero or reverses it, the
clutch will free the motor.

CONNECTING MOTOR AND GENERATOR TO ENGINE.

Connection between the generator and the motor to the engine
depends to a great extent upon the arrangement of the engine and the
other accessories, the three principal arrangements being as follows:

(1) Geared connection to fly-wheel (already described).

(2) Chain drive to crank shaft, or,

(3) Through the magneto or pump shafts, and thence through the
timing gears to the crank-shaft.

In addition to the above is the U. S. L. system in which the motor-
generator is mounted directly on the crank-shaft in place of the usual
fly-wheel. This is the simplest type of all since it dispenses with the
usual gears, bearings, clutches and shafts of the other systems, and
reduces the weight of the machine by an amount approximately equal
to the weight of the fly-wheel.

When the drive is through the fly-wheel, with independent motor
(M) and generator (G) as shown in Fig. 1, the motor end is cut in
and out of service by throwing a pinion (A) in or out of mesh with
the teeth ciut in the circumference of the fly-wheel (F) by means of
the starting foot pedal (P).

A switch (S) is opened or closed by the same movement of the
pedal which opens or closes the circuit between the storage battery
(B) and the motor. Depressing the pedal throws the pinion in mesh

IGNITION, TIMING, ETC.

IGNITION, TIMING, ETC. 165

with the fly-wheel and closes the switch allowing the battery current
to flow through the motor, thus turning the crank-shaft over and start-
ing the motor. The second set of reduction gears is shown at (R). A
resistance coil (H) is generally put in series by the switch which allows
the motor to turn over very slowly until the gears are in mesh. When
the pinion is forced clear across the face, the further movement of the
switch short-circuits the resistance, allowing the full current to flow
and the motor to build up its full speed.

The independent generator (G) is shown in driving relation to the
crank-shaft (C), the drive being through the silent chain (D). The
generator in this system is always connected to the crank-shaft no
matter whether the engine is starting or running normally. A cut-out
(E) is shown in series with the generator circuit (the purpose of the
cut-out was described in an early part of this chapter). The distributer
(I) is shown on generator feeding the spark plugs (J), the coil being
at (K).

In Fig. 2 is shown the motor-generator arrangement in which the
functions of motoring and generating are performed by a single unit
(L). When starting, the pedal (P) meshes the pinion (A) with the
fly-wheel gear teeth (K) as before described, the switch (S) perform-
ing the same way as in the two unit system. An extension of the
armature shaft is driven through the gear train (I) when the unit is
running as a generator.

Since two speeds are required for motoring and generating it is
evident that some form of slip clutch must be provided as at (M) so
that the armature (G) will be disconnected from the gears (I) when
the motor is starting the engine and is running at a high speed. This
clutch is usually of the ratchet type which will allow the armature
shaft to run faster than or to run past the gear (N).

It will also be seen that with this type there are two independent
commutators (D) and (E) for the two windings on the armature (G).
A single pair of poles (H)-(H) serve for both the motor and generator
windings.

Voltage and Battery Arrangement. In general there are three volt-
age arrangements at the present time, a straight system where lights,
motor and battery operate at six volts; a straight twelve volt system;
and a mixed system in which a double six volt battery supply current
at twelve volts to the motor and at six volts for the lamps, horn and
ignition system.

With the mixed system, the twelve volt leads are connected from
the end terminals of the battery, while the six volt circuit is obtained
by a third wire connected to the middle cell. A connection made be-
tween this third wire and any of the others gives six volts.

With twelve volts, either twelve volt lamps can be used or two six

IGNITION, TIMING, ETC.

IGNITION, TIMING, ETC. 167

volt lamps connected in series across the twelve volt wires. The latter
method is not the best as one lamp always burns hotter and dims the
other. Unequal burning shortens the life of the lamps.

IGNITION LAYOUT.

It is possible to provide three absolutely independent ignition sys-
tems where the electric selfstarter is used. (1) Current from the stor-
age cells. (2) High tension maghe'to. (3) An auxiliary dry battery.

An independent system in which the starting and lighting storage
cells are ysed exclusively is not desirable for the reason that the volt-
age is often much reduced owing to repeated demands for current in
starting. The dry battery is by far the simplest auxiliary for the rea-
son that a common circuit breaker, distributer, high tension leads, and
spark plugs can be used both for the storage and dry cells without
change. The use of a magneto involves a separate set of plugs and
ignition wires as well as an additional train of driving gears.

The use of more than one set of plugs is ordinarily objectionable,
especially with eight and twelve cylinder motors owing to the difficulty
met with in arranging the wiring on the tops of the cylinders.

ELECTRIC GENERATORS AND MOTORS.

When a current conducting object is moved across a magnetic
field, in a direction perpendicular to the magnetic lines of force, an
electric current is generated in the conductor which flows in a direc-
tion at right angles to the line of motion. It is upon this relation
between a moving conductor and a magnetic field that the operation
of the electric dynamo (generator) is based, the esfsential elements
being a, stationary magnetic field and a moving mass containing the
current generating conductors commonly called the "armature," In
practice the conductors are in the form of copper wire coils which
are rotated between the poles of a powerful electromagnet.

The electrical pressure or voltage depends upon the relative
velocity between the conductors and the field and also upon the
intensity of the field. The current output is limited by the size of
the armature conductors or more directly by their electrical resist-
ance. From this it will be seen that, other things being equal, a gen-
erator will deliver equal voltages at lower speeds with an intense
rather than with a weak magnetic field. The voltage also depends
upon the number of armature conductors, the greater the number of
conductors with an equal speed and magnetic flux, the greater will
be the generated voltage. The current is independent of the num-
ber of active conductors.

Aside from a few minor details of construction, the dynamo and

IGNITION. TIMING, ETC.

motor are identical, both having similar armatures, magnetic fields,'
brushes and commutators. Any direct current dynamo can be
run as a motor, while almost any comparatively large motor can
be run as a dynamo. In the smaller sizes of motors, however, the air
gap, or distance between the field poles and the armature, is much
greater in proportion than in the larger sizes, making it a difficult
matter to generate current when the field current is supplied by the
armalure.

THE DYNAMO OR GENERATOR.

In Fig. 4 is shown a section through an elementary dynamo, the
dissimilar magnetic poles being indicated by the letters N and 5.

Pig. 4. — Elementary Dynamo.

The conductors, shown in cross-section, are shi
circles marlted "A" mounted on the periphery of the a
C, which in turn is mounted on the shaft B, The dire
ture rotation is shown by the arrow.

With a constant direction of armature rotation, I
in the armature conductors reverses its direction
that the conductor passes from one pole to the
produced in the armature being alternating in character. If direct
or continuous current is desired some device must be introduced into
the externa! circuit to reverse these current waves into a constant
direction. In the figure, the direction of flow in the conductors is
indicated by the color of the small circles representing the armature
conductors, the white circles at the left indicating a current that is

by the small

of arma-

induced

every time

IGNITION, TIMING, ETC. 169

flowing toward the observer while the black circles at the right
indicate a current that Js flowing back along the core.

It will be noted from the figure that the flow reverses from one
pole to the next, the black conductors being under the left pole and
white conductors under the right. The general direction of the mag-
netic flux is indicated by the curved dot and dash lines that extend
from one pole to the other. As the three extreme upper and lower
conductors do not extend through the magnetic field it is evident that
they generate no current. The armature core C not only affords a
support for the conductors but also increases the intensity of the flux
through the conductors as the magnetic resistance of the steel core
is less than the same length of air gap.

This core is always "laminated," that is, built up from circular
discs of sheet steel. Before assembling the discs are painted or var-
nished so that adjacent discs do not come into electrical contact.
Laminating prevents the generation of useless and harmful currents
in the iron of the core, thus reducing the heating and power loss to a
minimum. The copper conductors are of course thoroughly insulated
from the iron of the core.

Since the direction of current flow in any one of the armature
conductors is continually being reversed, due to the effect of the
magnetic poles, it is necessary in all direct current machines to employ
a form of rotary switch known as a "commutator" for the purpose
of rectifying the direction of the reverse waves in the external circuit.

The commutator is a cylindrical drum built up of copper bars, the
bars* length being parallel to the shaft of the generator. A connection
from each armature coil leads to a single bar and each bar is thor-
oughly insulated from its neighbor by means of a thin strip of mica.
Thus by going progressively around the commutator it is possible
to make electrical contact with each of the coils independently.

Two conducting strips or "brushes" are arranged in insulating
holders which make sliding contact with the outer surface of the
commutator bars, these bars making contact at diametrically opposite
points. As the armature revolves the bars successively make contact
with the brushes, thus allowing the brushes to collect the current
from each armature coil at the time when they are occupying a definite
position in the magnetic field. Since a conductor gives only one direc-
tion of current flow in a single position in the magnetic field it is
evident that the brushes always collect current of a single polarity.

With the type of electrical generator commonly known as a "mag-
neto" the magnetic field is of the permanent type, that is, composed
of permanently magnetized hardened steel bars. In the generators
used for starting and lighting it is not advisable to use a permanent
field, the common practice being to use a field produced by an electro-

170 IGNITION. TIMING, ETC.

magnet. With a permanent field the voltage fluctuates with the engine
speed to such an extent that it is necessary to introduce an automatic-
ally operated resistance in order to maintain a constant charging cur-
rent, a device that is generally avoided with an electromagnetic
arrangement.

Fig. 5 shows the complete generator assembled in diagrammatic
form, this particular machine being of the "Bipolar" or two pole type,
commonly used with lighting and starting generators. In this figure
the armature conductors A are connected to the commutator bars C
by the spiral lead wires shown. The brushes G, and G' are diamet-

Fig. 5. — ^Assembled Dynamo or Uotor m Diagrammatic Form.

rically opposite to one another on the vertical center line of the gen-
erator and the current from the brushes is led to the external circuit
L-L' by the flexible leads H-H' that connect G-G' with the terminal
blocks 3-4 on the distribution board B.

The magnetic pole pieces N-N' and S-S' are magnetized by the field
coils F and F' which are wound with insulated copper wire in the
same way as the primary coil of a spark coil. Current passing through
the field coils causes a magnetic flux to pass through the armature
windings and core in the same way as shown in Fig. 4. In some gen-
erators, the pole pieces are made of stampings or are laminated, while
in other makes they are simply iron or steel castings. In any case

required lor the energization of the coils is obtained from

e of the generator.

IGNITION. TIMING, ETC. 171

The iron or steel used for the magnetic circuit of the lighting gen-
erators is of a very soft grade so that the magnetization can be
brought to a much higher point than would be possible with the hard
steel used in magnetos. When the current ceases to flow in a field
coil surrounding a soft iron or steel core the magnetism dies out
almost instantly to a very small value.

A surrounding field frame E-E not only serves to support the arma-
ture and other parts but also acts as a return path for the flux on
its way back from the armature core and pole pieces. In all types of
lighting and starting generators the field frame in addition acts as a
covering and protection for the interior wiring and the commutator
against moisture and the oil thrown from the engine. The feet J-J'
which hold the generator frame to the base of the automobile are in
this case cast with the frame. When laminated fields are used, the
laminations are held in a sort of sub-frame made of the cast iron, the
laminations carrying the magnetic circuit while the sub-frame acts
as a support for the various parts of the generator.

Armature current for the field coils enters at the terminal block 1,
passes through the coil F, flows along the cross connection D, and
then passes through the coil F' to the remaining terminal block 2.
, Connectors between the armature terminals 3 and 4 lead current to

the field terminals 1 and 2. The exact interconnections between these
terminals will be described later since they have a direct influence on
the performance of the machine, dividing the generators into three
different classes. Similar variations in the field connections of the
motors also are used, the particular type used depending upon the
use for which the motor is intended. The pole pieces N and S are
always of opposite polarity as indicated by the letters, and the coils
are therefore connected so that the current will flow in the . same
direction around the core.

In general there are four methods of placing the armature con-
ductors on the core. Fig. 6 shows the methods commonly adopted.
In "A" the conductors are laid directly on the surface of the core
with a sheet of insulating material between the wires and the iron.
The different coils are separated from each other by strips of fiber
board which also act as supports while winding. After the winding is
completed the wires are bound firmly to the core by means of trans-
verse hands of brass binding wire. As this type must be wound by
hand, it is difficult to repair, and is not proSf against very high speeds.

At present the "Slotted" or "Toothed" type shown by Fig. B is
most generally used, the slots affording a firm support for the con-
ductors against the stresses set up by centrifugal force and then by
driving effort. The imbedding of the conductors also is effective in
•/ decreasing the resistance to the magnetic field and therefore increases

172

IGNITION, TIMING, ETC.

the efficiency. Circular slots are often used as shown by Fig. C, espe-
cially in the smaller machines, a small outer slot being used for the
purpose of entering the formed coils. Fig. D shows full circular slots,
the coils being entirely embedded in the iron of the core. This gives
the greatest possible mechanical strength and fully protects the wind-
ing against abrasion. A construction of this nature is particularly
desirable with starting motors or motor generators which under certain
conditions may attain terrific speeds.

Fig. 6. — Types of Armature Coils.

As mentioned in a former paragraph, there are several ways in
which the fields can be connected to the armature circuit. In Fig. 7
the three usual methods are shown diagramatically, the series winding,
the shunt winding and the "short" compound. The particular winding
adopted is determined by the voltage regulation of the generator or
by the required torque and speed regulation of the starting motor.

In a series generator or motor the fields are connected in series
with the armature circuit as shown by the upper diagrarfi in Fig. 4.
Current from the positive brush B passes througb the lead C to the
field coll F, hence through C to the field coil F' and out to the external
circuit at L'. After passing through the external circuit the current

IGNITION, TIMING, ETC,

173

returns to the brush B', passes through the armature A and thence
to the brush B, completing the circuit. In this type it will be seen,
the entire current passes through the fields as well as through the

Wound

Shua/t HbuA/a

CoAf/=<?uA/a Wound

Fig. 7. — Field Connections.

armature. The series winding is used only with motors in automobiles.
A shunt jvinding is shown by the central figure in which the two
ends of the field coil are connected directly across the two brushes,
thus placing the armature and fields in parallel instead of in series.
The two leads L-L' from the brushes B-B' lead directly to the external

174 IGNITION, TIMING, ETC,

circuit. The field winding of the shunt type is of comparatively fine
wire having a high resistance so that only a small amount of current
will pass through the field. This winding is seldom used in either
starting motors or lighting generators for automobiles but is often
met with in stationary installations. Current from the positive brush
B' leaves the brush at b, passes through e' and the fields F' and F,
from which it returns through e and a to the negative brush B.

A compound wound motor has both shunt and series fields the con-
nections of which may be easily traced from the lower figure in which
FS and FS' are the shunt fields and F-F' are the series fields. The
shunt fields are connected to the brushes B and B' at a and B', the
two half fields being connected by the bridge e. One end of the series
field F' is connected to the brush B' while the other end of the series
field leads directly to the external circuit from L. The entire current
passes through the series fields as before.

Nearly all starting motors are series wound since this type gives
a better torque or drive than either the shunt or compound. This
great torque is particularly noticeable in starting the motor from a
standstill as the sudden rush of current passes through the fields as
well as the armature, thus increasing the magnetic flux and the torque
on the armature conductors.

The shunt winding tends to hold a fairly constant voltage in the
generator through normal outputs, but with heavy drafts of current
the voltage drops owing to the low resistance of the external circuit.
Shunt wound motors tend to maintain a constant speed with a constant
line voltage and varying load, but have a very low starting torque.

Compound wound machines may be divided into four principal
groups, the long compound, the short compound, the cumulative com-
pound and the differential compound depending upon the relations
existing between the shunt and series fields. The "long" an^ "short"
divisions are really subdivisions of the cumulative and differential
groups since either may be made long or short. In general the dyna-
mos used for automobiles are of the short differential order, a type
that tends to maintain a constant current with a varying driving speed.
In the cumulative type the shunt and series fields act together, an
increase in either field causing an increase in the total magnetic flux.
When the load increases the current naturally increases in the series
field which in turn raises the voltage, hence with the cumulative com-
pound an increase in current output causes a corresponding increase in
voltage at the terminals of the machine.

In the differential compound the shunt and series fields oppose one
another in such a way that an increase of current through the series
winding tends to decrease the total magnetic flux. Since an increase
in the current output thus diminishes the flux it follows that the volt-

IGNITION, TIMING, ETC. 175

age is also diminished, thus tending to maintain a constant flow of cur-
rent. In practice it is possible to build a differential compound that
will maintain a constant flow of current with widely varying speeds.
This is the condition to be met in charging the cells of a starting and
lighting battery. When the shunt fields of either the differential or
cumulative compound are connected directly across the brushes the
machjne^ia Jcn own as^'Sboct." When the shunt winding is connected
to a Brush at one end and to the outer end of the series field at the
other the connection is known as a "Long" compound.

MOTOR-GENERATORS.

In some types of self-starting apparatus, notably the "Delco," a
single unit performs both the functions of a motor and generator.
This machine has a double wound- armature and is provided with two
commutators, one commutator and winding for the generator function
and one for the motor. A machine of this type is known to the auto-
mobile trade as a "motor-generator." This however is not the cor-
rect electrical term, since this sort of machine has been known as a
"Dynamotor" for many years in electrical work.

Motor generators are always compound and are so connected to
the switching and starting apparatus that they are alternately made
cumulative and differential. To have a constant charging current the
motor-generator is differentially wound when running as a generator,
but is changed to a cumulative compound when running as a motor.
This change is effected generally by reversing the current flow through
the series field winding.

DELCO SELF-STARTING AND LIGHTING SYSTEM

With the exception of one model, the lighting, starting and igni-
tion are all performed by one unit in the Delco system. The motor
generator is provided with a double winding on the armature and has
two commutators, one for the motor service and the other for the
generator. A Delco timer and high tension distributer, together with
the spark coil, are mounted on the motor generator. When running as
a generator, the unit is driven through an overrunning clutch. When
operating as a motor the armature drives the engine through a reduc-
tion gear which meshes with teeth cut in the engine fly-wheel rim
through a clutch, so that the motor can be connected or disconnected
from the engine at the will of the operator. It should be understood
that it is the policy of the company to fit the system to the car rather
than to market one single model to meet all conditions.

In Type "A" both commutators are mounted on the front end of
the shaft. One motor brush and one generator brush are mounted on

176 IGNITION, TIMING, ETC.

a common rocking support in such a way that when the generator
brush is in contact, the motor brush is out of contact, and vice versa.
A switch which regulates the flow of current from and to the machine
is mounted on the brush support, so that both are operated by the
starting pedal. When the pedal is depressed, the generator windings
are disconnected from the circuit by the switch, the generator brushes
are lifted, and the motor brushes placed in contact with the motor
commutator.

When running as a motor the fields are cumulative compound
wound, both a shunt winding and a reverse series winding being in
circuit at this time, the series winding improving the torque of the

motor. When running as a generator this winding with series reversed
becomes a dilTerential compound and maintains a constant voltage
without the use of an external current regulator. All of the units .are
of the single wire type, the return current passing through the frame.
The main switch which controls the current between the generator
and battery also controls the ignition system, so that no connection
exists between the generator and battery until the ignition current
is turned on at the switch. With the generator standing, this allows a
little current to pass back through the generator between the time
that the ignition is turned on. This reverse current from the battery
turns the motor over very slowly, making it easier to mesh the gear
with the teeth in the fly-wheel. The amount of current lost in this
way is very small. This is called "motoring the generator."

IGNITION, TIMING, ETC. ' 177

CIRCUIT CONTROL SYSTEM

Two buttons are provided for the control of the ignition, one button
(M) controlling the current from the battery to the circuit breaker
and the other (B) controls the current from the auxiliary dry bat-
tery set. When either button is operated it not only closes the igni-
tion circuit but also connects the generator with the storage battery,
as noted above. An automatic circuit breaker is included in the main
circuit for the protection of the apparatus in case of a short circuit or
ground. This is a coil of wire wound on an iron core which, with an
excessive current passing through the windings, makes and breaks
the circuit intermittently in much the manner of a buzzer, thus giving
warning of a fault in the circuit.

The ignition system is of the ordinary Delco type, except that there
is a coil of resistance wire connected in the primary circuit between
the primary of the spark coil and the timer. Under normal conditions
this coil has little resistance and impedes the current to a negligible
amount. Should the main switch be carelessly left open, however,
with the motor standing still, the uninterrupted current will heat the
coil, increase the resistance, and greatly reduce the flow of current
through the breaker and spark coil. This will prevent damage to the
spark coil and will save the storage battery from a rapid and injurious
discharge.

CIRCUIT DIAGRAM OF DELCO SYSTEM

Referring to Fig. 9, the circuit diagram, the generator and motor
are shown as two different instruments, though they are really com-
bined. The upper contacts K and X on buttons M and B complete
the ignition circuit and the lower contacts J and Z control the motor-
ing of the generator. Upper and lower contacts operate together, on
the same rod. The upper contact X on button B simply supplies cur-
rent for the ignition from the dry battery.

Assume the conditions as shown, that is, all buttons down. Both
dry and storage batteries are on open circuit. Current cannot go to
the motor because the brush L is up. It cannot go to the generator,
because the contacts J, K, X and Z are open. If the engine were being
cranked by hand, with the ignition off as shown, the only passage of
current would be from the generator armature through the brush A,
reverse series field R to F to shunt field S to ground G-1, G-2 and
brush H back to the armature.

Assume we get ready to start: we pull up button M, closing con-
tacts at K and J. We get ignition current from the storage battery
in the following way: From the plus terminal of the battery through
E, switch terminal 1, D, circuit breaker Q, B, K, Y, switch terminal

178 IGNITION, TIMING, ETC.

7, primary of ignition coil P-1, resistance unit R-1 timer, to ground at
G-7 — with an electrostatic ground through the condenser C-1 to G-5.
The circuit is completed through the ground to G-4 and the negative
terminal of the storage battery.

Motoring of the generator occurs when M is pulled out. In this the
circuit is to D, where some of the current goes to C, to the contact J,
to switch terminal 6, through the reverse series field R, to generator

'"nie AutomobiTi

brush A, to brush H and to ground G-1, completittg the circuit
through ground G-4 and the battery. A part of the current divides
at F and goes through the generator shunt field to ground G-2. Cur-
rent through the generator causes it to be driven slowly as a motor.

If button B were pulled up instead of button M, the connections
would be just the same, except that current from the dry battery
would be impressed on the ignition circuit from the positive terminal
of the dry battery, through 2, X to Y and the ignition circuit pre-
viously outhned. At the same time storage battery current would
be sent to the generator from the point C through Z to the generator
connection at A-I.

Now. with the ignition on and the generator running as a motor, we

IGNITION, TIMING, ETC, 179

press the starting pedal. This shifts the pinion on the end of the arma-
ture shaft, which is rotating slowly, into mesh with the gear train to
teeth on the fly-wheel. As the pedal completes its movement, linkages
lift the generator brush H away from its commutator and lower the
motor brush L to its commutator. This disconnects the generator
armature from the circuit and throws the motor in. Storage battery
current is then impressed directly on the motor through E, the series
field S-1 brush L, the circuit being completed through brush L-1 to
ground at G-3. This rotates the motor and through the fly-wheel
starts the engine.

When the engine has taken up its cycle, the starting pedal is re-
leased, brush H goes to the commutator and brush L leaves its com-
mutator, putting the generator back into circuit and cutting the motor
out. Also the pinion is retracted from the fly-wheel, and the gener-
ator starts to furnish current for the battery and ignition. This is
accomplished through the following circuit: A, R, F, 6, J, C, D,
where it divides, part going to the battery through 1 and E to the
positive terminal of the battery, and part through Q, S, K, Y, 7, to the
ignition.

Current for the lights and horn comes from the battery or generator
from S to the bus bar XlYl. Button N supplies the sidelights V from
T through U to 5. Button O supplies the headlights, and P throws in
the dimmer resistance.

The Delco system. Type B, is the one employed on the greater
number of cars equipped with this make of starting, lighting and igni-
tion. There is a difference in the regulation of the generator output.
It will be remembered that in the type already described the voltage
regulation is obtained by the compound winding of the generator
fields, having a shunt field and a reverse series field.

In the Type B, the reverse series field is omitted, leaving only the
shunt field, and the regulation is obtained by an automatic regulating
resistance, which also acts as an automatic spark control and is con-
tained within the distributer housing. It consists of a spool of bare
resistance wire, inserted in the shunt field of the generator. On this
spool is a contact, which can move up or down on the spool. The con-
tact is shorted direct to ground, so that as the contact moves up on
the spool it cuts in more and more coils of resistance wire, and when
it is at the top of the spool, all the resistance is in circuit and the
current through the shunt field is weakened correspondingly.

The contact is attached to an arm operated by a centrifugal gov-
ernor on the timer shaft, so that as the armature speeds up, more
resistance is inserted and the output of the generator thus controlled.
Also the ignition resistance is grounded through the regulating resist-

180 IGNITION, TIMING, ETC.

ance and is cut out of the ignition circuit when the arm is at top
position. This increases the intensity of the spark at high speeds.

In the C type the combination switch is of a different type and has
not the double-contact feature of the others. Instead of this an auto-
matic cutout relay is used to close the circuit between the generator
and storage battery when the generator voltage is high enough to
charge.

Instead of the governor-controlled variable resistance used in the
Type B systems to control the generator output, a solenoid mercury
well voltage controller is employed. Motoring of the generator is ob-
tained by a push button on the combination switch.

There is an added feature in the ignition circuit of the Type C out-
fits. This is the ignition relay which is connected in the dry battery
circuit. It serves to break the primary circuit immediately after it is
completed by. the auxiliary contact mechanism in the timer, thereby
inducing a high tension flow through the secondary circuit, which
results in a hot spark in the spark plug. It is simply an electromagnet,
having two windings, one of coarse wire carrying the main ignition
current. It is connected so that current through this winding ener-
gizes the core, attracts an armature which opens the circuit. The
other winding is of comparatively fine wire connected around the
point of break in the main circuit, so as to hold the armature down
by the current shunted through the fine winding when the main
circuit is opened. If it were not for the fine wire winding the making
and breaking of the main circuit would give a vibrating spark at the
plug, instead of a single spark. This vibrating effect is purposely
produced for starting by opening the circuit through the fine wire
winding, when the button on the combination switch is held in.

BIJUR STARTING SYSTEM

Either a motor-generator or an independent motor and generator
are used in the Bijur system according to the conditions. The
ignition apparatus is not included in the Bijur circuit, this being
installed separately by the automobile builder according to his judg-
ment. The motor generator drives or is driven through a silent
chain to the crank case. The two unit system of a motor and
generator start the car and supply current for the starting and light-
ing, the generator being of the constant voltage type. The voltage
is held constant at any engine speed by means of an automatic regu-
lator that varies the current flowing in the field magnets.

With a constant voltage it is possible to obtain a tapering charge
that is to have the current flow heavier at the beginning of the charge
than at the end, a very desirable feature in the proper maintenance
of a storage battery. Since the voltage of a partially discharged

IGNITION, TIMING, ETC, 181

battery is lower than the voltage at full charge, there is less opposition
to the flow of generator current and a higher charging rate is the
result. As the charge continues the voltage of the battery rises and
cuts down the 'current, this "tapering" down the charge. The system
can be wired either for the one wire (grounded return) or the two
wire circuit.

In general the circuit for light can be considered as a battery
lighting circuit with the generator placed in parallel with the battery,
and all of the apparatus, the lights, horn, ignition, and starting motor
circuit all receive current from the battery terminals. Any of the
wires can be connected with any piece of apparatus without regard
to polarity, not even the generator being affected by the polarity of
the wires leading to it from the battery.

Gear drive to the fly-wheel is used with the independent motors,
the pinion being thrown in and out of mesh with the fly-wheel in a
manner similar to that of the Delco, an intermediate gear train being
used for reducing the motor speed. In another type of independent
motor drive the motor acts directly on the fly-wheel through a pedal
operated pinion. This motor is built to stand high speed and will
not be injured if left in mesh after the engine starts normal firing.

BIJUR CIRCUIT DIAGRAM

While the circuits may differ slightly in detail, Fig. 10 will give the
general principles of the Bijur circuit, in which (B) is the battery,
(G) is the motor-generator, (A) is the ammeter, (C) is the tempera-
ture regulator, (R) is the cut-out relay, (L) is the magnetic latch, (V)
is the voltage regulator, (D) is the main knife switch, and (E) is the
starting button.

It will be noted that the motor-generator (G) is provided with an
armature having a double commutator (1) and (2), a single pair of
field coils (F) and (F^), and a double wound armature (H).

The field magnets of the motor-generator are compound wound,
that is to say, that the winding shown by the thin lines is in parallel
with the brushes while the coil, shown by the heavy lines, is in series
with the main current so that all of the current passes through the
series field. Since the voltage of a generator increases with its speed
it is necessary (in order to maintain a constant voltage) to decrease
the current through the shunt field by means of an adjustable
resistance such as the voltage regulator (V). This regulator is
connected to the shunt field by the wire (4) and to the opposite
side of the circuit by the wire (14).

This adjustment of the field resistance is accomplished magnetically
by the magnet coil (I), which acts on an iron plunger within the case.
The plunger carries a coil of resistance wire in such a way that it may

182

IGNITION, TIMING, ETC.

be drawn in and out of a mercury bath in the bottom of the regulator,
thus varying the length of wire in circuit. Should the voltage rise
slightly above normal, the magnetic pull of the coil (L) will be
increased, thus raising the plunger farther out of the mercury and
increasing the resistance of the field circuit. If the engine spe«d
should fall the plunger will drop, cutting out the field resistance in
proportion to the fluctuation in the voltage, thus increasing the field
current and raising the generator voltage again to normal.
A cut-out relay (R) is provided with a double winding (8) and (9),

"AiiGA/er/cljtTCf^

Nor£f

Fig. 10. — Circuit Diagram of Bijur System.

the first mentioned being a shunt winding while the latter is in series
with the charging current. These windings are on an iron core which
act on the spring controlled armature (11). This armature actuates
the contact points (10) which open and close the charging circuit.
When the voltage of the generator is above that of the battery, both
windings act together in holding the contacts together and closing
the circuit. Should the generator voltage become less than the
battery, the flow passing through the series winding (9) will be
reversed, a condition that will neutralize or kill the magnetic field in
the relay core, allowing the spring to open the contacts and break
the circuit.

A magnetic latch (L) with the magnetic coil (12) is connected in
the starting circuit in such a way that on completing the circuit with

IGNITION, TIMING, ETC, 183

push button (1) the coil will draw the latch back, connecting the
starting pedal and gear train together mechanically. It is impossible
to operate the gears before this is done.

Because of the variations in the resistance of the storage battery
due to temperature changes, an adjustable ballast resistance (C) is in
series with the regulator magnet (I). This is moved manually and
controls the voltage limits.

OPERATION OF BIJUR STARTER

On pushing the starting button (1), the current flows from the
battery terminal (5) across the switch (6), through the ammeter (A)
and into the motor commutator (1). This runs the motor at about
100 revolutions per minute for meshing the starting gears. From the
other brush on the commutator the current flows through the coil
(12), through the contacts (1) and back to the negative battery
terminal (7). No current can flow through the cut-out as the contacts
(10) are open when starting. A part of this current flows through
the voltage regulator windings (I). In passing through the coil (12)
of the magnetic latch the armature is drawn back, connecting the
starting pedal and the gear shift.

The starter pedal, on being pushed out, first meshes with the gears
on the armature shaft and then, with the teeth on the fly-wheel, the
slowly revolving armature making this last a simple matter. When
the pedal is full out a switch is actuated by the pedal that gives the
full current to the motor. The switch (6), on being opened at this
moment, disconnects the original starting button current, the current
now flowing from the battery terminals through the contact (13),
through the series field (3) of the motor, through the armature at (2)
and back to the storage battery negative pole (7). This cranks the
motor at full speed and when the motor begins to fire the pedal
should be released quickly, the release throwing the gears out of
mesh and releases switch (6).

With the engine firing, the generation of current begins. The
current flows from the commutator at the right, through the ammeter
to (16) and thence Jto the positive pole of the storage battery. No
amount of current can flow through the battery since the contacts
(10) are open in the main circuit, but a small amount does flow
through the relay shunt coil (8), causing the armature to be drawn
down and the main circuit closed when the voltage of the generator
reaches a value of about 7 volts. With the main circuit closed the
charging current from the battery now passes through the series coil
(9), which aids in keeping the points in contact.

Should the current become reversed through (9) owing to a drop
of voltage or speed in the genera tor, the polarity of (9) will be

184 IGNITION, TIMING, ETC.

reversed and will act against the field of the magnet (8), thus killing
the magnetism and allowing the spring to pull up the armature and
open the circuit.

GRAY-DAVIS SELF-STARTING SYSTEM

The greater part of the self-starting and lighting equipment made
by the Gray-Davis Company is of the separate unit system, the motor,
generator and ignition apparatus being entirely independent mechani-
cally. In one type only the distributer and generator are in one
piece.

In the older type of generator the voltage was held constant by the
use of a centrifugal governor, but in the later models the voltage is

Fig. 11.— Gray-Davis Motor Equipment in Which P is the Motor
Pinion and B the Fly-Wheel Gear. The Shiftmg and SUrting Lever
is at the Right. (Courtesy of "Motor Age.")

maintained electrically by a device placed on the top of the generator,
A cut-out disconnects the generator when its voltage falls below that
of the battery. The generator designed for four cyclinder cars runs
approximately at 2^ times the crank-shaft speed. The six cylinder
model runs at cam-shaft speed, oc I'A limes crank-shaft speed. This
allows the generator to run at its rated speed of 650 revolutions per
minute, with a car speed of from 10 to 12 miles per hour.

Fly-wheel drive is standard, with the reducing gears, starting switch
and gear shift mounted as an integral part of the starting motor.
The movement of the pedal closes the starting switch and meshes the
gear with the fly-wheel. In a model brought out for use in the Ford
car the motor and generator are arranged in the "double deck"
method; that is, one unit is placed above the other, both, however,
being contained in a single casing.

IGNITION, TIMING, ETC, 185

The Model T generators are rated to give an output of 10 amperes
at 6.5 volts, with a speed of 1,000 revolutions per minute, while Model

5 gives 10 amperes, 6.5 volts, at 650 revolutions per minute. The
Model T generator weighs 20j^ pounds.

Type Y motor develops full torque with 100 amperes at 2,800 revolu-
tions per minute. For very heavy cars Type H-1 motor is used, this
pulling full load at 1,500 R. P. M., with a current of 150 amperes at

6 volts.

THE ECLIPSE-BENDIX STARTER DRIVE

This device is an attachment for the starting motor which does
away with the necessity of an overrunning clutch or a starting pedal,
and can be applied to any starting motor that drives through the
fly-wheel.

Generally speaking, it consists of a threaded shaft on which a
threaded pinion is mounted, the shaft being connected with the arma-
ture shaft of the motor by means of a coiled spring. A weight is
attached to one side of the pinion so that it is out of balance, the
weight normally hanging down. This pinion may now be considered
as out of mesh with the teeth of the fly-wheel.

When the starting motor starts to revolve, the pinion is pulled
along the shaft toward the fly-wheel teeth, since the pinion is pre-
vented from turning by the counterweight. This action is similar
to the travel obtained by holding a nut on a revolving screw, since
the hole in the pinion is threaded like a nut. It is pulled across the
entire face of the gear until it meets a collar on end of the shaft, at
which time, of course, it starts revolving with the shaft and drives the
fly-wheel. The impact of this sudden termination of its travel is taken
up by means of the spring that connects with the armature shaft so
that no shock is transmitted to the motor.

When the motor starts firing and comes up to speed it runs away
from the pinion, turning it in the opposite direction so that it runs
along the shaft and out of mesh with the fly-wheel. In other words
the pinion is "unscrewed" on the shaft, placing it in its former position.

As the weight is now revolving with the pinion at a high speed, the
centrifugal force exerted by the weight causes it to bend on the
threads of the shaft so that continued rotation of the motor will not
cause it to travel back into mesh.

BOSCH-RUSHMORE STARTER SYSTEM

The Bosch Magneto Company market two self starters, the Bosch,
which is a system of their own, and the Bosch-Rushmore, which was
made by the Rushmore Dynamo Company.

186

IGNITION, TIMING. ETC.

The Bosch-RushiDore consists of a separate generator And motor
with an independent magneto, the motor driving the fly-wheel through
an arrangement that automatically engages and disengages the arma-
ture shaft pinion with the teeth on the fly-wheel.

1 JW/*,, -t*..^

— ■

ti.

(

***

SM:

Fig. 12. — Above is Shown the Shifting Armatuie Device of the
BoBch-Rushmore System. At A the Armature is Out of the Field
Giving a Low Voltage. At B the Generator is Giving Full Voltage
With Armature Central in the Field. The Spring is in Shaft at Left
of Armature.

A spiral spring placed on the commutator end of the motor shaft
which forces the armature to one side of the pole pieces, the armature
shaft being constructed so that it can slide longitudinally in its bear-

IGNITION, TIMING, ETC. 187

ings. When current is passed through the motor, the armature is
drawn magnetically under the poles against the compression of the
spring, and at the same time the motor pinion is drawn with the
shaft and into mesh with the fly-wheel gears. As the armature is now
under the poles it can exert its maximum torque.

In the Bosch self-starting system there is a separate motor and
generator, the motor usually being connected with the crank-shaft
through a silent chain, an over-running clutch allowing for the speed
differen'fce due to the two extreme running conditions. One generator
is of the magneto type having a permanent magnetic field and is
designed to run at engine speed. The other Bosch generator is a
shunt wound machine having an automatic field current regulator
located in the dash switch-board.

Starting is effected by a relay circuit operated through a push button,
the closing of the relay circuit closes the main switch magnetically
and starts the motor. When the starting handle is retained, the inser-
tion of the handle connects the battery to the ignition system and
cuts out the magneto. When the engine starts firing, the battery is
automatically cut out and the magneto is replaced in the circuit.

AUTO-LIGHT CRANKING SYSTEM

The two unit auto-light system operates on 6 volts both for the
cranking and lighting systems. A conventional circuit breaker, pedal
switch, and storage battery are placed in the usual circuit, the breaker
cutting out the generator to prevent a reversal of the current. In one
model a primary circuit breaker and distributer for the ignition
system is mounted on the generator. Drive can either be to the crank
shaft by silent chain, to the fly-wheel through a gear train or to
the transmission. Due to the construction, the units can be mounted
either horizontally or vertically. The usual gear reduction from the
motor is 25 to 1.

A differential compound winding maintains a constant current.
Charging begins at an engine speed of about 200 revolutions per
minute, which corresponds to a car speed of about 5 miles per hour.
The output increases with the car speed until it reaches 17 miles per
hour, at which point the current is 12 amperes. At this point the
series winding holds the output constant so that it is no longer
affected by an increase in speed. The generator operates at engine
speed so that it is possible to drive from the magneto shaft.

The model M cranking motor is of the series wound type weighing
365^ pounds. It is claimed that this motor will crank a six cylinder
engine under 60 pounds compression at 100 revolutions per minute,
the current draft being 95 amperes.

=1; v"

ill I
5 Si : 1

fi :§ J

¥ "■

.IS

S.-8 •^••

ill J *i*
1^4= III i

]ilil|if

IGNITION. TIMING, ETC. 189;

PART X
VALVE SETTING AND TIMING

To understand the "timing" of motor valves one must have the
principle of the four cycle motor in mind. The periods of valve
opening and closing vary widely in different types and makes of
motors. With equal areas of pipe and valves, and with a constant
suction, less mixture will enter the cylinder of a high speed motor
than in a low speed type, since the rate of gas flow will be equal in
both cases. In other words, the gas will not have time to completely
fill the cylinder of the high speed motor before the piston reaches
the end of the stroke with identical valve timing.

In general there are two methods of increasing the rate of gas
flow: (1) By increasing the area of the valve opening; (2) by open-
ing the valve earlier and closing it later, thus increasing the time
period of flow.

Both methods have limitations, since for certain practical reasons
it is impossible to increase the valve area beyond certain sizes, and as
we have certain functions to perform in predetermined angles we
cannot increase the time of opening beyond a certain point. Increas-
ing the valve diameter beyond a well defined limit will result in valve
warping, or in excessive wear on the cams, push rods and valve seats
due to the increase in weight. Owing to the increased inertia of a
heavy valve we will require heavier valve springs which still further
increases the wear on the moving parts.

Lifting a valve higher to increase the area of opening still further
increases the stress and wear on the valve actuating mechanism since
the stress varies as the square, of the velocity. A high lift causes
the valve to hammer on the seat with unnecessary violence and is a
prolific cause of noise and vibration. To actuate a heavy valve against
a heavy spring pressure at high speed absorbs no inconsiderable per-
centage of the motor's output of power. The exhaust valves are the
worst offenders in respect to wear and power loss since they open
before the end of the stroke or before the gas has expanded to a low
pressure. The earlier the exhaust valve is opened the higher will be
the gas pressure and the greater the wear. A very early exhaust
opening also decreases the output of the motor since the gas has

190 IGNITION, TIMING, ETC.

not exerted its pressure as far in the stroke as it should. Delaying
the inlet valve closure beyond a certain point materially shortens the
compression stroke and interferes with the combustion chamber and
valve pockets.

Long manifolds or intricate passages with short sharp bends in-
crease the gas friction and therefore limit the rate at which the gas
flows. The time given for the gas under a slight suction pressure
is extremely short even in low speed engines.

Since all motors vary in regard to valve areas, speeds, lifts, length
of passage, etc., it will be seen that the only true authority for any
particular type of motor is the manufacturer. For this reason we
give a list of timings advocated by a number of prominent automobile
manufacturers. The use of this table in connection with the direc-
tions for making the adjustments will enable the reader to set the
valves of almost any modern American automobile. In the case of
cars using a stock motor, determine the make and model of motor
and consult the maker's name in the list.

THE FOUR STROKE CYCLE (First Revolution)

The four stroke cycle motor, or incorrectly called the "four cycle
motor," accomplishes all of its operations in two revolutions or four
strokes. There is one power impulse in every two revolutions. On
the first stroke (suction stroke) the gas is drawn into the cylinder
through the inlet valve by the piston. During this stroke the inlet
valve remains open. The exhaust valve must remain closed so that a
sufficient vacuum can be produced for the movement of the mixture.
At, or a little past the end of the stroke, the valve closes.

COMPRESSION STROKE (First Revolution)

The piston now returns to the outer end of the stroke with both
valves closed, compressing the gas before it.

POWER OF EXPLOSION STROKE (Second Revolution)

Both valves remain closed until a little before the piston reaches
the end of the stroke, at which point the exhaust valve opens and
allows the spent gas to escape to atmosphere.

SCAVENGING STROKE (Second Revolution)

The piston moves outwardly expelling the burnt gas through the
exhaust valve which remains open through the entire stroke. The
inlet valve remains closed.

At the completion of the "scavening stroke" the entire cycle is

IGNITION, TIMING. ETC. 191

repeated. The exhaust valve usually remains open slightly after

[he end of the scavenging stroke. In the following description the
term "moving outwardly" means that the piston is moving away from
(he crank-shaft. As practically all modern automobile motors are
of the vertical type the term "outwardly" would have the same meaning
as "upwardly."

ANGULAR MEASURE OF EVENTS

The time at which any event takes place, such as the opening or
closing of a valve, or its duration, is usually measured in angular

FiK- 1. — Valve Setting Piagram.

degrees taken on the crank circle. For example. — If the inlet valve
is open for 200°, we mean that the crank will swing through an angle
of 200° from the lime that the valve starts to open until it is closed.
In locating the point at which a certain event occurs we refer to either
the upper or lower dead center. For example. — When the inlet valve
of a certain motor opens 11° past the upper dead center, we mean
that the crank will move from the upper dead center through an angle
of 11* before the valve opens. All valve settings are usually shown by
diagram such as Fig. 1. In this particular figure the outer cross

192 IGNITION, TIMING, ETC.

hatched ring represents the length of time that the inlet valve is open.
The inner ring represents the angle through which the exhaust valve
remains open. The intersection of the vertical center with the
outer circle at the top of the diagram represents the upper dead
center. The upper inclined dotted line is the position of the crank
center at the time the inlet valve opens, which is shown as 11.1**.
Following the outer ring around to the bottom of the diagram we find
by the inclined dotted line that the inlet closes 36.8° after the lower
dead center. In figuring the total opening of the inlet valve we find
it to be (180—11.1) + 36.8 = 20S.7\ In this case we see that the inlet
valve opens after the upper dead center and closes after the lower
dead center being open more than the 180* that we have considered
in describing the theoretical cycle of the engine.

From the lower inclined solid line we see that the exhaust valve
opens 46.3* before the crank reaches the lower dead center, and closes
7.7° after the upper dead center. The length of exhaust valve ppening
is therefore 7J + 180 + 46.3 = 234°. In the theoretical cycle this
would have been 180°. This diagram represents the average of a
great number of 1915 four cylinder models, the data being compiled
by the staff of "The Automobile." According to the same authority
the average timing for 1914 four cylinder models was as follows:

Intake opens 11.2° past upper dead center.
Intake closes 35.0** past lower dead center.
Exhaust opens 50.0° before lower dead center.
Exhaust closes 9.3° past upper dead center.

The timing of the average six is slightly different than that given
for the four (1915 models):

Intake opens 10.7* past upper dead center.
Intake closes 37.6° past lower dead center.
Exhaust opens 46.0° before lower dead center.
Exhaust closes 7.0° past upper dead center.

In comparison with the fours and sixes given above we will give the
timing of the 1915 eight cylinder Cadillac motor (high speed type).
Bore and stroke =: 3}i x 5% :

Intake opens 0.0* past upper dead center.
Intake closes 46.6° past lower dead center.
Exhaust opens 46.6° before lower dead center.
Exhaust closes 0.0* after upper dead center.

It will be noted on this high speed motor that the inlet and exhaust
open and close respectively on the upper dead center, and that the
inlet valve remains open way past the lower dead center in order to
give the gas time to enter. The total period of inlet opening is 226.6*.

IGNITION, TIMING, ETC. 193

In reading the diagrams it should be noted that rotation of the crank
is assumed to be toward the right or in the direction of the hands
1^ of a clock. Hence, if an event is said to be after upper dead center, it

will occur after the crank has passed the center when turning in a
right-handed direction.

VALVE LAP

We have seen that the exhaust valve closes and the inlet opens

after dead center, but that these events do not usually take place at

the same time, the exhaust closing first. The exception to this rule

is the Cadillac 8, which in following aeronautic practice opens the

. inlet and closes the exhaust simultaneously — on the upper dead center.

The angle between the closing of the exhaust and the opening of
the inlet is called the "valve lap," and is expressed in degrees. In
^ the average 1915 four cylinder motor this would be from diagram,

11.1 — 7.7 = 3.4 lap. The Cadillac is an example of zero lap since the
opening of the inlet and the closing of the exhaust takes place at the
same time.

There are three conditions of lap, negative, positive and zero. With
the positive lap both valves are open together, in negative lap the
exhaust closes before the inlet opens, and with zero both actions take
place at the same time. With negative lap the piston descends before
the inlet opens creating a slight vacuum, increasing the rush of gas
into the combustion chamber. With zero lap there is no vacuum at
the entrance point. With positive lap the inertia of the exhaust gases
creates a slight vacuum which is an aid in foicmg the mixture into
the cylinder. This is generally used with aeronautic and tee head
type automobile motors, as the incoming and outgoing gases do not
conflict.

AUXILIARY EXHAUST PORTS

To decrease the amount of hot gas passing over the exhaust valve,
auxiliary exhaust ports are sometimes provided. These are similar
to the exhaust ports cast into two-stroke cycle motors. The ports
consist of either a series of holes cored or cast in the cylinder walls
and located so that the piston top uncovers them at the inner end of
the working stroke.

194

IGNITION, TIMING, ETC,

TIMING TABLE— LATEST MODELS

Car Name

Model

Abbott

Auburn

t Beaver

Briscoe

tBuda

Inlet Inlet

Opens Closes

Deg. Peg.

Past Past

Top Bottom

Center Center

F-P 10 28

L 17 29

K 11 44

^6 21 30

6-40 21 39

6-47 17 47

43 5-30 36

K 10 35

ML 10 30

6A 10 25

6B 10 • 25

4A 10 25

4B 10 25

E 10 35'

N 10 30

A 45

M 15 ^^

G 5 45

•i 5 45

Q 5 45

OM-3 5 45

TM^3 5 45

QM-3 5 45

OU 5 45

TU 5 45

QU 5 45

R 5 45

RU 5 45

V 5 45

VU 5 45

SS 5 45

SSU-3 5 45

SSU-4 5 45

LS 5 45

LSU 5 45

Exh.

Opens

Deg.

Before

Bottom

Center

40
42
45
44
43
50
71

55
45
38
38
38
38
42
45

53
55
55

55
55
55
55
55
55
55
55
55
55
55
55
55
55
55
55

Buick C-24, C-25... 16-11' 35-41' 56-19'

C-36, C-37,

C-54, C-55. 14-5' 36-25' 56-51'

Cadillac 8 46-40' 46-40'

Cartercar ........9 15 38 45

Exh.
Closes

De^.

Past

Top
Center

2.5

8
11
10
12
13
15

5
5
8
8
8
8
8
5

12J^
5
5

5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5

13-11'

1 1-29'

10'

IGNITION, TIMING, ETC.

195

TIMING TABLE— LATEST MODELS

Inlet

Exh.

Opens

Closes

Opens

Closes

Car Name

Model

Deg.

Past

Before

Past

Top

Bottom

Top

Center

Case

.... T'U

• 25

Chalmers ....

.... 26B

32^

Cole

. . . . Four

Light Six.. . .

Big Six

t Continental . .

. . . . 6F, 6A, 6-C,

6-N, 6-P...

2-30'

C-R

11-30

44-12'

45-48'

11-30

C^ •J • ^^ • X ,• • • fl

17-53'

29-25'

42-36'

8-20'

t Davis

• • • • oB

Dorris

....l-A-4

Ford

Closes
on top

Franklin

6-30

SVA

Glide

Haynes

t Hazard

Herflf-Brooks

....4-40

On top
cent.

6-50

t Herschell ....

....4404-A

14^
2

445^
45

4402-J

center

4403-N

Before
45

4401-J

Center

4301-E

Center

4001-M

Center

196

IGNITION, TIMING, ETC.

TIMING TABLE— LATEST MODELS

Car Name

Model

Inlet Inlet

Opens Closes

Deg. Deg.

Past Past

Top Bottom

Center Center^

tHerschell 4101-S

4405-C
4201-B
6201 ..
6301 ..

Hupmobile K

Jackson Olym. 46

48-Six

Jeffery 93-2

104

106

King

Kline

Krit

,5-pass.
7-pass.

Lex.-Howard .... 6M

6L
4K

Locomobile L-4

M-S
Lyons- Atlas K-4

McFarlan T

Marmon ... 41

Maxwell 25

Metz 22

Moline

2
2
2
2

15
15
18
IS
18

9-43'-
40"

5
5

8
8

10
10
10

Top
cent.

Top
cent.
5

10
10

19
16

Before
45
40
40
40
40

43
35

38
38
46
50
46

30-38'-
20"

45
45

31^
SVA

28
28
20

48-30'

32
32

40
40

Exh.

Opens

Deg.

Before

Bottom

Center

45
45
45
45

38
40

45
45
47
45
47

32-10'-
20"

55
55

39
39

40
40
44

46-22 50-52'

56-10'

47
47

56
56

Exh.
Closes

Deg.

Past

Top
Center

Center
Center
Center
Center

6
20

10
10
15
10
15

5
5

2
2

2^
2^
10

16-27'
Aft.
bot.

cent.

15-39'

10
10

12
12

IGNITION, TIMING, ETC.

197

TIMING TABLE^LATEST MODELS

Car Name

Model

National .
t Northway

,39 .
40 .
47 .
49 .
30 .

Inlet
Opens

Deg.

Past

Top
Center

15
IS
IS
15
15

Oakland . .
Oldsmobile

Paige-Detroit
Partin

Z7 15

49 15

42 15

55 15

6-46 :.. 10

4-36 11-20'

20 18-14'

Peerless

Premier

48-6 8-40'

54 17-53'

55 17-53'

A 10

Pullman 6-48

R. C. H.

Regal

K 18-12'

D-1915

10
10

Reo

R & S 17-46'

t Rutenber

Saxon

38
28
27
22
B

15
18
18
15
12

Inlet
Closes

Deg.

Past
Bottom
Center

38
38
Z^
38
38

28
40-26'
52-28'

30-21'

29-25'

38^

36-25'

50
46
46
50

Exh.
Opens

Deg.
Before
Bottom
Center

45
45
45
45
45

40
51-18'
56-43'

43-53'

42-36'

46 J4

46)4

53-18'

50
47
• 47
45
55

Simplex 30 H. P.... 10-59'

50 H. P 13-40'

75 H. P.... On dead

center

Speedwell

10 Be-
fore up
dead
center

33-12'

36-4'

41-51'

56-52'

60
66-24'

Exh.
Closes

Deg.

Past

Top
Center

10
10
10
10
10

10
10
10
10

2/2.,

11-40'
12-55'

3-55'
8-20'
8-20'
10

2J4
11-30'

5
14-13

10
15
15
10
12

Scripps 8 18-53' 47-31' 43-25' 15-45'

8-13'
16-26'
16-26'

1.6

198

IGNITION, TIMING, ETC.

TIMING TABLE— LATEST MODELS

Inlet Inlet

Opens Closes

Car Name Model Deg. Deg.

Past Past

Top Bottom

Center Center

Stearns SK-4 4 40

SK-6 4 40

SK-L4 8 40

Studebaker Six 12-30' 32-30'

Four 12-30' 32-30'

EC 12-30' 32-30'

SD 12-30' 32-30'

.Velie 15 10 28

14 10 28

12 7 36

Ahead

Willys-Overland . . 80 8 38

81 8 38

82 1 28
Winton 21 ''.'■''.''.'* 20-45' 35-30'

t Wisconsin A 15 45

^ B 15 45

C 15 55

D 15 45

E 15 55

F 15 30

H 15 35

K 15 30

M \5 45

P 15 30

• Given in incites on the fly-wlieel.

t Stock motors built for assembled automobiles.

Exh.

Opens

Closes

Deg.

Before

Past

Bottom

Top

Center

center

7-30'

2y2

2/2

54-40'

15-30'

IGNITION, TIMING, ETC.

199

TIMING TABLE— EARLIER MODELS

Car Name

Abbott 34-40

Abbott 44-50

Abbott Belle Isle

Allen 40

Cadillac 1914

Pathfinder 4

Pathfinder Big 6

Pathfinder Little 6

Chalmers

Chandler Six

Chevrolet C

Chevrolet H2-H4

Case 40

Franklin M No. 4......

Haynes 26-27

Haynes 28

Hupmobile 32

Oldsmobile 54

JefiFery 6-96

JeflFery 4-93

King B

Krit M/K-M-KR

Lyons-Knight K

McFarlan Six T

Maxwell 4-35 . . .^

Maxwell 4-25

Moon Six 50

Moon Four 42

Marathon, Winner, Run-
ner, Champion

Jackson, Olympic 40, Ma-
jestic, Sultanic

S & M

Pratt 50

Paterson 32 and 33

Palmer Singer Brighton
Six L

Paige Detroit 36

Paige Detroit 25

Republic E

Reo the Twelfth

Simplex 38

Simplex 50

Selden 49

Velie, 9-45, 6-40, 9-5, 9-4,
9-2, 6-5, 6-4

Velie 11-35

Speedwell A B C

Inlet

Exh.

Opens

Closes

Opens

Closes

Past

Before

Past

Top

Bottom

Top

Center

11-30

44-12

45-48

11-30

17-53

29-25

42-36

8-20

10-00

2»-00

40-00

2-30

15-00

40-00

45-00

10-00

14-20

36-26

31_34 7_00 to 17-00

11-30

44-12

45-48

11-30

10-00

2&-00

40-00

2-30

10-00

28-00

40-00

2-30

12-00

33-00

55-00

12-00

14-00

39-00

49-30

12-00

13-00

49-00

47-00

9-00

6-4a-^

54-8-1^

27-13

14-6- J4

13-00

30-00

50-00

13-00

8-00

33-00

51-30

17-00

5-00

35-00

47-00

2-00

5-00

35-00

37-00

2-00

21-00

28-00

46-00

16-00

15-00

38-00

45-00

10-00

18-00

46-00

47-00

15-00

l»-00

46-00

47-00

15-00

9-44

30-38

32-10

5-00

12-00

28-00

39-00

2-00

10-00

40-00

60-00

10-00

36-00

43-30

10-00

5-00

40-00

35-00

6-00

32-00

43-00

6-00

10-00

28-00

40-00

2-30

14-00

24-00

31-00

21-00

12-00

45-00

46-00

7-00

15-00

38-00

45-00

10-00

28-00

40-00

2-30

12-00

45-00

10-00

15-00

38-00

45-00

10-00

6-00

40-00

45-00

5-00

9-40

32-30

41-50

11-40

9-40

32-25

40-30

12-00

15-00

30-00

45-00

10-00

l»-00

36-00

53-30

14-00

10-20

31-40

54-20

7-50

13-10

34-40

57-30

15-40

13-00

26-30

4a-30

7-30

7-00

36-00

43-00

12-00

5-00

31-00

39-00

13-00

10-00

28-00

40-00

2-30

IGNITION, TIMING, ETC. 201

TIMING OF MULTIPLE CYLINDER MOTORS

So far we have only considered the timing of a single cylinder and
have neglected the timing relations that exist between the cylinders
of the modern motor. It should be understood that the timing of each
cylinder is always the same on any multiple cylinder machine, the
only additional point entering into the problem being the relation of
the cranks and cams of one cylinder to the cams and cranks of the
next. The purpose of increasing the number of cylinders beyond
unity is to secure balancing, as well as to decrease the stresses and
also to reduce the weight of the fly-wheel. In regard to the timing
we have only to consider the effects of balance.

Every cylinder of the four-cycle type has an explosion or power
impulse in every two revolutions. With two cylinders there are
twice as many impulses, or an impulse in every revolution. With
four cylinders the impulses are again doubled, giving two impulses
per revolution. For the same power output the power given out in a
two-cylinder motor per impulse is one-half of that of the single-cylin-
der, thus causing one-half of the shock on the machine and the pas-
sengers. It will be seen that increasing the number of cylinders for
a given power decreases the shock, and that with an increasing num-
ber of impulses per revolution the "torque" or pull on the machine
is made steadier and therefore more effective.

With more than four cylinders the impulses "overlap,** that is to
say, there is always two or more cylinders active at one time. With
six or eight cylinders the torque is modified so that the effects of
individual cylinder impulses are scarcely perceptible.

In addition to the reduction of individual impulses, it is possible
to balance the multicylinder type mechanically without massive
counter-balances on the crank shaft.

Very good mechanical balance may be had with the well known
two-cylinder opposed type, since the crank is arranged in such a way
that the pistons move in opposite directions at the same time, and
the connecting rods form equal angles with the cylinder center lines.
This type is not well balanced in regard to the explosive impulses.
In the case of a four-cylinder motor, the crank shaft is arranged
so that two pistons move up and two move down simultaneously.
The connecting rods do not make equal angles with the cylinder
center line as in the case of the two-cylinder opposed. The arrange-
ment of the crank of a four-cylinder motor is shown by Diagram A,
Fig. 6, in which the dot and dash line represents the center line of a
crank shaft. The crank throws, marked 1-2-3-4, show the relative
positions of the four pistons, the pistons of cylinders 1-4 being at the
bottom of the stroke and 2-3 at the top of the stroke. An end view

202 IGNITION, TIMING, ETC.

of the crank circle is shown at the left in which the small circle 2-3
represents the crank pins at the top, and 1-4 the pins at the bottom.

It is possible to fire this arrangement in two ways with evenly dis-
tributed impulses: (1) Cyls. 1-2-4-3, and (2) Cyls. 1-3-4-2, the num-
bers given representing the number of the cylinders, while the arrange-
ment of the numbers gives the order in which they are to be fired. A
table at the top of the chart gives the events taking place in the
variotrs cylinders with the two different firing orders. The crank
pins of a four-cylinder motor are all in the same place, or all lie on
the same vertical line, as shown in the end elevation. It is usual to
take the front cylinder as "No. 1."

With a six-cylinder motor it is possible to fire in four orders —

1-5-4-6-2-3
1-5-3-6-2-4
1-4-2-6-3-5
1-2-3-6-5-4

It should be remembered that the crank throws of a six-cylinder
motor are not all in the same plane, but are arranged at an angle of
120 degrees apart. As two cylinders move together there are always
two throws in the same position, as will be seen from the four end
views at the left of the six-cylinder crank arrangement.

The table at the bottom of the chart gives the events that are taking
place in the different cylinders with the various firing orders. For
this table we are indebted to C. T. Schaefer.

FIRING ORDER OF EIGHT CYLINDERS

in general, there are eight orders in which an eight-cylinder motor
can be fired, but there are only two of these that can be used if full
advantage is to be taken of the eight-cylinder principle. The orders
adopted by well known manufacturers follow:

Cadillac Eight. Two blocks of four cylinders each are used on
the Cadillac, the cylinder blocks being at an angle of 90 degrees with
one another. The blocks fire alternately, first on the left and then
on the right, it being assumed that the observer is facing the front
of the motor. The numerals as arranged below each represent a cyl-
inder, while the two columns represent the right and left blocks. To
follow the firing follow the numbers in order, 1, 2, 3, etc.

Right

Left

Block

Front

Motor

IGNITION. TIMING, ETC. 203

With front cylinder No. 1 on the left firing first, the next cylinder
will be No. 2, the last cylinder on the right. It will be noted that if
the succession on any one side is followed that each block fires in the
usual four-cylinder order — 1-3-4-2. The timing will be found in the
timing table.

With No. 1 starting on working stroke, No. 2 is on compression,
No. 3 is starting compression, No. 4 is completing suction, No. 5 is
starting suction, No. 6 is scavenging, No. 7 is exhausting, and No. 8 is
about one-third through working stroke.

The Dc Dion Eight. The blocks of the French De Dion eight also
fire alternately, but in the reverse way from the Cadillac, the first
cylinder starting on the right instead of the left. There will be found
a considerable difference between the two in the firing order.

8 7

6 5

4 3

2 1

Right Left

Block Block

Front of Motor

The 6rder is to be followed in the same way as in the diagram given
with the firing order of the Cadillac. The two systems given give
two extreme firing orders possible with the eight-cylinder motor
working under proper conditions.

The White Eight-Cylinder (1916). Instead of having the cylinders
arra-nged in the conventional "V" form, the White eight-cylinder
motor has a row of four vertical cylinders with the two trunk pistons
in tandem, that is, a single cylinder unit is provided with two bores,
one above and the other below, with a common piston the diameter
of the lower piston being larger than the upper by an amount neces-
sary for equal areas. A single piston casting serves for both cylin-
ders, and is connected to the crank shaft by a single connecting rod to
a single crank throw.

A set of exhaust and inlet valves is used for the upper and lower
chambers of each cylinder unit, but are located on opposite sides of
the motor. This may be considered as being two superimposed "L"
head cylinders formed in one casting, the valves of which are driven
by two cam shafts. All crank throws are in the same plane as in the
ordinary type of four-cylinder engine. A single carburetor is used.

Starting at the front with both the upper and lower cylinders and
numbering toward the rear, the cylinders in the top row will be suc-
cessively, 1-2-3-4, and from the front to the back on the lower row the
numbers will be 5-6-7-8. The firing order will be 1-8-2-7-5-4-6-3.

204

IGNITION, TIMING, ETC.

TIMING OF KNIGHT MOTOR

The valve functioning of the Knight motor is performed by two
concentric sliding sleeves surrounding the piston, and not by the
poppet valves ordinarily used. Instead of cams, the sleeves are driven
by eccentrics from a shaft that corresponds to the cam shaft of the
poppet valve motor.

Since a description of the mechanical features of the Knight motor
would be out of place in this book, the reader is referred to the ''Gas,
Oil and Steam Engine," published by the C. C. Thompson Publishing
Company, Chicago, 111., the publishers of this volume.

Inlet Opens Inlet Closes Exhaust Exhaust
Make Past Upper Past Lower Opens Closes

Center Center Before After

Stearns-Knight 4° 40** 60" Top Center

Moline-Knight 20V 50** 50** 5°

Lyons-Knight

Porter-Knight Racer 5° 62** 70** 15"

It will be noted that the Porter-Knight motor has the exhaust
port open 10 degrees after the inlet opens, and that the Moline-Knight
has the exhaust closed 15 degrees before the inlet opens.

TIMING THE GNOME AERO MOTOR

The seven-cylinder rotary Gnome motor fires alternate cylinders
in succession. Starting with cylinder No. 1 on the firing point, the
order will be taken against rotation:

1-3-5-7-2-4-6

Pig. 7. — Firing Order of Gnome Motor.

IGNITION, TIMING, ETC.

205

.«»

Q .n' i^T'tj

Effects of Spark Timing Shown by Indicator Cards. Left Vertical Bow (a-a-a): at
Top Shows Correct Timing, Center Shows Retarded Spark; Bottom Shows Adrance.
Center Vertical Bow: (d-d-d) at Top Shows B>etard and Weak Mixture; Center (d) Is
Correct Spark and Weak Mixture; Bottom (d) Advanced Spark and Correct Mixture.
Bight Hand Vertical Column (c-c-c); Normal Spark and Weak Mixture; Advanced
Spark Bich Mixture; Bottom Freignition.

TIMING OFFSET CYLINDERS

It IS common practice to "offset" the crank shaft from the cylinder
center line. There are two advantages to be gained by offsetting,
(1) The pressure of the piston on the cylinder walls is much reduced,

M«fcnywK«clHcrfLO.

Cnakfi

M«rk FlrwM Hert I

Crank

MDcfrect

J UtlOpenH

2 UKdMfaf

MvkfhFwMHert LO.
GmkPtiiliM

Hark FlywM Hert £ C
Gnd^PMiliMi

necluif Rod*

Fljwhccl

3 Eihaust Opcnif

4 EikiMtOosmc

Diagram for Setting the Valves of an Offset Motor.
(Courtesy ''Automobile Journal.")

IGNITION, TIMING, ETC. 207

as the connecting rod makes a smaller angle with the cylinder.
(2) The working stroke is increased and the compression stroke is
shortened.

Practically the only difference in timing the valves of an offset
motor is in locating the dead center. With no offset the two dead
centers lie on the cylinder center line. With the offset motor,^ the
crank pin lies to one side of the cylinder center line when on dead
center, and the three points of crank shaft, crank pin and cylinder
center are on one straight line. In other words, the upper point of
the piston in an offset motor occurs when the crank pin is to one
side of the vertical center line. Bringing such a crank to the vertical
or upper cylinder center line will lower the piston.

This is illustrated by Fig. 8, which shows four crank positions for
four valve events. The following timing has been assumed:

Diag. 1. Inlet opens at 8 degrees past upper dead center.

Diag. Z, Inlet closes at 26 degrees past lower dead center. Inlet
opening = 198 degrees.

Diag. 3. Exhaust opens 46 degrees before lower dead cfenter.

Diag. 4. Exhaust closes 5 degrees past upper dead center. Exhaust
opening = 231 degrees.

It should be noted that this timing is only used for an example in
working out the diagram and that the same methods can be applied
to any other timing. The first thing to do will be to take off the lower
half of the crank case so access may be had to the crank. Now by
inserting a wire through the cylinder head and by resting the end on
the top of the piston, the shaft may be slowly turned back and forth
until the extreme top of the piston travel is found. This is the upper
dead center. A much more accurate method would be to use a
straight edge, so as to get the three centers of the piston pin, crank
pin and crank shaft center in line, but as this is an exceedingly diffi-
cult thing to do on account of the construction of the case, we will
assume that the operation is performed by the first method.

After the top center is found, lay a straight edge across the lower
crank case edge and measure the angle made by the crank with the
straight edge. This will be the angle of offset or the angle made by
the crank with the cylinder center line when the piston is on the
upper dead center.

Add to this the angle of inlet valve advance (8 degrees) and turn
crank to new angle. This will be the crank position at which the
inlet valve should start to open. Find the following lower dead
center and in the same way locate the point at which the inlet valve

closes. The exhaust valve positions may now be found in the same
way.

Care should be taken to mark each of the positions on the fly-wheel

208 IGNITION, TIMING, ETC.

when located. A pointed or indicating finger should be placed on some
convenient part of the engine (near the fly-wheel) so that the marks
on the wheel can be relocated. We are indebted to the ''Automobile
Journal" for the diagrams illustrating this article.

VALVE SETTING ON STATIONARY ENGINES

The exhaust should open when the crank lacks 30 degrees of com-
pleting the outer end of the power stroke, that is, the crank should
make an angle of 30 degrees with the center line of the cylinder when
the exhaust valve begins to open, and should be inclined away from
the cylinder. Some makers have the exhaust open a little later in
the stroke, but little is to be gained with a later opening, as the reten-
tion of the charge beyond 30 degrees heats the cylinder and does very
little towards developing power. The only advantage of the late
opening is that the valve opens against a lower pressure and causes
slightly less wear on the parts.

The exhaust valve should close 5 degrees after the crank has passed
the inner dead center on the exhaust or scavenging stroke, although
some makers close the valve exactly on the dead center. The 5 de-
grees should be given to allow the gas all possible chance of escape.
The piston is said to be on the inner dead center when it is in the
cylinder as far as it will go, and on the outer dead center when it is
on the center nearest the crank shaft.

The intake valve should open about 5 degrees after the exhaust
valve closes, or 10 degrees after the crank passes the inner dead
center. The inlet valve should never open before the exhaust valve
closes on a low speed engine. The above timing is for engines run-
ning 150-600 R. P. M. The automatic type of inlet valve, of course,
cannot be timed, but attention should be paid to the strength and ten-
sion of the spring and the condition of the valve stem guides.

The inlet valve should close 10 degrees after the crank passes the
outer dead center in order that the cylinder be filled to the fullest pos-
sible extent. If the valve closed exactly on the dead center, a partial
vacuum will exist and the charge retained in the cylinder will be com-
paratively small, but if the valve remains open past this point the air
would have time to completely fill the cylinder and develop the capa-
city of the engine. The longer the inlet pipe, the longer the inlet
valve opening.

PART XI

FORD IGNITION TROUBLES

The Ford magneto is of the flywheel type, a series of
horseshoe magnets on the flywheel running past a corre-
sponding series of coils mounted on a stationary support.
As the poles of the magnets are mounted well out toward
the periphery of the flywheel, they pass the coils at a very
high velocity, even when the wheel is revolving at a low
number of revolutions per minute. This allows the gen-
eration of a considerable current at low-motor speeds.
Since the coils are stationary, there are no brushes or
other forms of revolving contacts in the magneto proper.
The current thus generated is alternating current of low
voltage, and is stepped up to the high-tension current by
means of vibrator coils of a type already described. A
timer, or commutator, is used that is similar to a battery
timer in every respect, this device being attached to the
front end of the camshaft.

Fig. 1 shows the arrangement of the magneto in detail,
the flywheel magnets at the left and the stationary coil
plate at the right. The magnets M, sixteen in number,
are attached to the flywheel A by the bolts B. The outer
ends or poles of the magnets are fastened by the magnet
clamps C. As will be seen from the left-hand diagram,
similar poles of adjacent magnets are joined together
under each magnet clamp, two north and two. south poles
alternately. As the different polarities pass a given pole,
the generated current alternates in direction with the
change in the polarity of the magnetic flux. The current
thus produced cannot be used for storage-battery charg-

209

210 FORD IGNITION SYSTEM

ing unless passed through some type of rectifier. If the
current is to be used for lighting it can be obtained only
when the engine is running.

As shown by the right-hand diagram, there are sixteen
magneto coils that correspond in spacing and radius to
the poles of the magnets. As installed in the machine, the
coils face the magnets instead of being in the position
shown, the illustration being reversed for clearness of
explanation. Each coil consists of a number of turns of
copper wire or strap, thoroughly, wrapped with insulating
tape, and is mounted on a central iron core. In the figure
the coils are indicated by R and the cores by S, the sup-
porting plate being marked U. The pole tips of the mag-
nets pass over the faces of the cores S with about 1/32-inch
clearance betwen the faces of the cores and the pole tips.
All of the coils are connected in series, one end grounded
to the plate, and the other end is connected to the con-
nection post P, which is mounted on the transmission
housing. From the connection post wires run to the
spark coils and lamp circuit. Connection between the
terminal of the coils and the connection post is had by
a contact spring.

Ford Magneto Troubles and Adjustments. In the first
place, the reader must be cautioned against connecting a
storage battery in circuit with the magneto unless a
double-throw switch is used, which will disconnect the
magneto when the battery is in service. If battery cur-
rent passes through the magneto coils, it is almost certain
that the magnets will become demagnetized and worth-
less. In case of such an accident the magnets can be re-
magnetized by the owner of the car, but the best and
cheapest method is to replace them with new magnets.
These can be obtained from a Ford branch house or ser-
vice station. For the benefit of those that wish to re-
magnetize the magnets we will give the following instruc-
tions :

FORD IGNITION SYSTEM

212 FORD IGNITION SYSTEM

The process of remagnetization requires a direct cur-
rent of at least 30 amperes. This can be obtained from
direct-current lighting mains, or better, from four to six
storage batteries connected in series. Cells having a ca-
pacity of 40 aniperes at 6 volts will be suitable. The
magnets are turned until they are in correct relation with
the magneto coils, and the current is then passed through
the coils at short intervals until the magnets are restored
to their former strength. Each coil acts as an electromag-
net and passes its magnetic flux through the permanent
horseshoe magnet, a portion of this flux being retained.
If lighting current is used, some form of resistance must
be placed in the circuit or the high voltage will most cer-
tainly burn out the coils, leaving the machine in a worse
fix than ever. In this regard be sure that the lighting cur-
rent is direct and not alternating, for if alternating current
is passed through the coils the magnets will be entirely
demagnetized.

After obtaining a source of current, place an ordinary
hunting compass on the transmission and over the fly-
wheel, so that the compass is % inch to the left of the
connection post. The compass, we will assume, has the
North-pointing end of the needle colored blue, with the
South-pointing end left the natural color of the steel.
In placing the compass to the left of the connection post,
we are supposed to be facing the front of the car. Turn
the motor over slowly until the blue hand of the compass
points to a spot about 34 i^^ch from the side of the fiber
bushing at the bottom of the connection post. Disconnect
the wire from the connection post and attach instead the
positive (t) wire of the battery. Now, take the negative
battery wire and touch it quickly and intermittently to
the frame or some other metal part of the car, leaving the
wire in contact with the frame for about 5 or 6 seconds.
As the wire is removed from contact with the frame a
bright flash will be seen if the circuit is in condition.

FORD IGNITION SYSTEM 213

Abouj/tw fflty c|Hf,h (-.nntarfg should be made at intervals
of one second before the charging is considered as com-
plete. Be sure that the positive battery wire is connected
to the post and that the blue end of the compass needle
points to the connection post. This is rough on the bat-
tery because of the large amount of current drawn, and
the contacts should not be made for a longer period than
absolutely necessary. Better buy new magnets.

A gradually weakening magneto current may be due
either to weakened magnets or to dirt accumiilating under
the contact spring that completes the circuit between the
magneto coils and the connection post on the transmis-
sion cover. It may also be caused by short-circuited or
grounded coils, although this trouble is rather unusual.
Try the simplest remedy first^ — that is, remove the three
screws that hold the binding post in position, remove the
spring, and then clean out any foreign matter that may
have collected at the point of contact. If this does not
remedy matters, carefully examine the wiring for short
circuits or grounds before attempting to undergo the
tortures of removing the magnets from the magneto.
Many times the wear in the crankshaft bearings will cause
the magnet and coils to separate to such a degree that the
current will be weak and the engine will misfire at mod-
erate speeds or be difficult to start. Trouble from this
source will be saved if the gap between the coils and mag-
nets is measured occasionally. It should be little diflferent
than 1/32 inch. If the separation is too great the current
will be weak and the magnets will lose life rapidly. If the
gap is less than 1/32 inch there is likelihood of the mag-
nets rubbing on the cores of the cells. Rubbing often
results in the destruction of the coil insulation, causing
grounds and a sudden loss of brightness in the lamps.

When the magneto stops business suddenly, while at
the same time the motor runs well on the battery, clean
out the contact spring under the connection post, or see

214 FORD IGNITION SYSTEM

that the wire aUd coil insulation is not abraded through
rubbing. Magnets do not weaken suddenly. If very large
lamps are used, or too many are installed, the demand for
current will be greater than the supply, and the trouble
will usually be blamed on the magneto. If there is trouble
with the ignition after the installation of new lamps, this
is probably the cause. The lamps furnished by the Ford
company consume 2 amperes at 8 volts, and the best re-
sults will be obtained by lamps taking this voltage and
current. The many current regulators now built for the
Ford magneto improve the lighting wonderfully and save
current for the ignition system.

Should the magnets be found at fault it will be neces-
sary to remove the entire magneto — that is, it will be
necessary to remove the entire power plant from the car
before beginning the real work. If you are wise you will
try everything connected with the ignition system before
starting this job. After the power plant is removed, take
off the crankcase and transmission cover, and unfasten
the four bolts that hold the flywheel to the crankshaft.
Pull off the flywheel and the entire magneto is exposed.
All of these parts should be marked so that they can be
replaced in their proper positions.

To take off the old magnets, remove the cap screw and
the bronze screw that hold them in place on the wheel,
carefully noting the method of attachment. The new
magnets as received from the Ford service station are
mounted on a board in exactly the same relative position
as they will occupy on the fly-wheel. Be careful that they
are placed on the wheel in the same position as on the
board, as a slight mistake will neutralize the polarity
of one or two pairs of magnets and hence cause unlimited
trouble with the ignition. Should such a mistake occur
remember that poles of like polarity should lie together
under the same magnet clamp. The second important
item is that of clearance between the magnets and coils.

FORD IGNITION SYSTEM 216

Line up the faces of the magnets so that they are just
1/32 inch from the faces of the coils spools or cores.
While the magneto is in this disassembled condition take
a look at the coils — see whether the insulation is worn or
whether the connections are loose, paying particular at-
tention to the ground connection made by the copper
ribbon with the coil frame. If the ground connection is
loose or broken, no current can flow since the return
to the magneto is through the frame or ground. The cir-
cuit must be complete at all points.

The Ford Commutator and Its Adjustment. The mag-
neto current (Low tension) is distributed to the four
spark coils by a roller type commutator or timer. This
instrument determines the time at which the spark occurs
in the cylinder and distributes the current to the coil of
the cylinder next in firing order. In effect it is a rotary
automatic switch that revolves in a fixed relation to the
crank-shaft, its function being to make and break the
current in the primary circuit. Since there are four
cylinders, there are also four insulated contact points
with which the roller makes contact as it revolves. From
each contact point, is a wire lead to the corresponding
spark coil. The commutator is located at the front of the
motor and is driven directly from the front end of the
cam-shaft so that it revolves at one-half crankshaft speed.

Fig. 2 shows a detail view of the Ford commutator
and its connection to the spark coil and magneto. The
roller C rotates in a hinged fork D, and is pivoted to the
cam-shaft A by the pin E, the latter being fastened to a
lug projecting from the cam-shaft. A small coil spring
G connected with the forked lever at F forces the roller
into contact with the contact segments S-S1-S2-S3 as it
revolves. The contact segments are imbedded in insu-
lating material so that they cannot make contact either
with each other or with the frame of the commutator.
The roller of cojurse is grounded to the cam-shaft, so

216 FORD IGNITION SYSTEM

that when the roller makes contact with any segment,
that segment and the connecting wires are also grounded.
This arrangement allows the current from the coil to
flow along the wire, through the corresponding segment
and back to the magneto through the ground. The con-
tact segments S-S1-S2-S3 are provided with the binding
posts or connection posts marked respectively T-T1-T2-
T3 to which the spark coil wires are attached. A short
lever H attached to the commutator housing allows it to
be tilted back and forth for retarding and advancing the
spark.

To facilitate the connections made with the coil, the
wires are colored and numbered to correspond with the
cylinders and coils. Thus the blue wire No. 3 connects
with the terminal T on the commutator and with the pri-
mary binding post (Upper row) on the spark coil. With
colored insulation the wires can be recognized with cer-
tainty at either end of the cable. The colors on the
diagram correspond with the colors of the insulation on
the machine, and they should not be connected in any
other order than that given. In the diagram we are
supposed to be facing the engine from the front of the
car, looking toward the dash.

Looking at the spark coil box we notice that there are
two principal rows of binding posts, an upper and a
lower row, each row having four posts. The upper row
connects with the primary wires coming from the com-
mutator while the lower row contains the high tension
posts that connect with the spark plugs in the cylinders.
In the lower row, post No. 1 connects with cylinder No. 1,
this being the front cylinder in the block. The remaining
cylinders are numbered in order, so that cylinder No. 4
is the last or rear cylinder in the block. Below the high
tension posts are two low tension posts that connect
with the magneto, battery, and lamp circuits. The bat-
tery post is at the left, while the post at the right connects

FORD IGNITION SYSTEM 217

both with the magneto and with the horn. These con-
nections are controlled by a switch in manner that will
be described later. The electric horn is also connected
with the right hand connection post.

If the commutator is to perform its functions properly
the roller and the contact points must be kept clean and
smooth. The inside surface of the circle (Y) around
which the roller runs should be perfectly smooth so that
it will make perfect contact and not skip and bound over
the obstructions that can be caused by foreign matter
or worn places in the insulation. If the roller fails to
make good contact, the cylinder corresponding to that
contact segment will not fire. If dirty clean thoroughly
with a cloth moistened in gasoline. If the parts are
worn replace them with new or reface the insulation and
segments. The spring should be strong enough to force
the roller into good contact. Sometimes the roller spring
weakens and causes a bad case of missing. Worn insula-
tion on the wires leading from the commutator is a com-
mon cause of trouble as in this case they produce short
circuits. The back and forth movement of the commuta-
tor housing in advancing and retarding the spark often
causes broken wires or loose connections. Always see
that the wire connections are tight and clean. A steady
buzzing in one of the coil units will indicate a short cir-
cuited wire. A short-circuited commutator wire is likely
to cause a severe "kick-back" when the car is cranked
for the short is likely to close the circuit before the pistons
reach the end of the compression stroke.
' The commutator should be sparingly oiled, enough to
prevent friction and wear but not enough to gum up the
contacts and pivots. In cold weather the oil often thick-
ens to such an extent as to prevent the roller from making
contact with the contact segments. This is often the
cause of cold weather starting trouble as the roller is
often unable to scrape^the oil away from the segments.

218 FORD IGNITION SYSTEM

Even after getting the motor started, one or more cylin-
ders will continue to misfire until the oil is sufficiently
softened by the heat to permit of good contact with the
rest of the segments. A little kerosene mixed with the
lubricating oil will prevent the oil from solidifying in
extremely cold weather.

For repair or adjustment, the commutator can be re-
moved by removing the spark control rod from the tim-
ing lever H, and then loosening the screw that passes
through the breather tube on top of the cam-shaft gear
cover. This will release the commutator case so that
it can be easily removed for inspection. The brush can
be removed from the cam-shaft by unscrewing the lock
nut removing brush cap and driving out the pin. When
the brush is replaced it must point upward when the
exhaust valve of cylinder No. 1 is closed.

Oil the commutator slightly every day, a few drops
at a time being sufficient. The roller revolves at a high
speed and if not properly lubricated will soon wear out
and cause missing. At the end of a week, the spent
and carbonized oil should be removed or there will be
trouble due to sticking of the parts through the thicken-
ing of the oil. Thin oil should be used or heavier oils
should be thinned with kerosene, the thinning of the oil
being of more importance in the winter than during hot
weather. The parts are small and easily gummed up
with heavy lubricants such as cylinder oil. Any trouble
due to rough or dirty surfaces is more noticeable at high
speed than at low as the roller starts jumping over the
high spots at anything greater than a very moderate
speed.

The switch has three positions. One for connecting
the battery into circuit (Bat.) ; one position for connect-
ing the magneto (Mag.), and a central position (Off) for
cutting out or stopping the engine.

PART XII

BOSCH MAGNETO CHART

A chart developed by the Bosch Magneto Company obviates many
of the troubles experienced in timing a magneto. As the majority
of magneto builders specify the opening of the circuit breaker to take
place at some particular crank angle (in degrees) it is often difficult to
find the angle because of the variation in piston travel and connecting
rod length. With the automobile it is impossible to make measure-
ments directly because all of the ports are enclosed.

As the distortion due to the length of connecting rod is practically
the same in all cars, the calculation for this factor may be neglected,
except in extreme cases, the ratio of the crank to rod being taken
as 1 to 4.5 in all cases.

The row of figures at the bottom of the chart gives the extreme
stroke of the piston or twice the length of the effective crank arm.
The vertical row of figures at the right are an index to the slanting
lines and give the angle made by the crank with the center line of
the cylinders in degrees. The figures at the left index the horizontal
lines and designate the travel made by the piston for a given crank
angle.

Example. We will assume that our engine has a stroke of six
inches, and that it is necessary to find the distance traveled by the
piston from dead center when the crank has moved through an angle
of 30 degrees with the cylinder center. In other words, we wish to

219

aau IGNITION, TIMING, ETC.

obtain the crank position for a magneto whose breaker is to open
the circuit at 30 degrees past upper dead center.

Locate the given stroke in the figures at the bottom of the chart

r--

■

■^

■'

■

— —

—

t
30 I

2o:

J 3*> 4 4!i 5 5i> 6 6)i 7 7li. 8
Stroke in inches
Fig. 1.— Bosch Magneto Timing Chart.

and trace upwardly along the vertical line until it intersects the slant-
ing line indicated by "30" at the' left, as at the point "C." Follow
the nearest horizontal line to the left hand edge of the chart where
it will be found to nearly coincide with the !^-inch numeral. This

IGNITION, TIMING, ETC, 221

means that for an angle of 30 degrees, the piston must travel ^ inch
down from the upper dead center.

Now, to set the engine at 30 degrees, set the engine on dead center,
insert a wire through the petcock in the cylinder head, and then turn
the engine over slowly until the piston has moved down l4 inch, as
shown by the wire. The crank is now at 30 degrees.

This chart is equally applicable to setting valves or in adjusting any
part that requires setting of the crank at any specified angle.

CHARGING MAGNETS

When the permanent magnets become so weakened that the mag-
neto will no longer give a good spark, they must be removed from
the frame and recharged. This is best done by placing them on the
poles of a pair of powerful electric magnets as shown by Fig. 2 in
which A is the permanent magneto magnet, and M-M^ are the electro-
magnets. The current from the line enters the magnet coils as at L
and leaves at L^ highly magnetizing the pole pieces N and S. The
flux from the poles passes through the permanent magnet A, practi-
cally saturating the steel.

It should be remembered that only direct current can be used with
this device, since an alternating current would reverse so rapidly that
the magnet A would be in worse shape than before. There are several
remagnetizers on the market that utilize the direct current from the
ignition or lighting batteries. In the figure, Y is the soft iron yoke
that fastens the magnets M and M^ together and also completes the
magnetic circuit.

When demounting the magnets for remagnetizing their ends should
be marked so that they will reassemble cbrrectly on the magneto. The
marked magnet legs should be placed on the same pole of the electro-
magnets so that the legs on one side of the magneto armature will
all be of the same polarity. It is a good plan to place all of the right
hand legs on north or right hand (as shown in figure) poles of the
electro magnet. Failure to observe this precaution will mean trouble
with the magneto, since placing dissimilar legs together is equivalent
to a magnetic short circuit.

After placing the permanent magnets on the poles S-N, close the
switch and start tapping the magnet A rapidly and lightly with a
wooden mallet or soft faced hammer. Hammering the magneto mag-
nets while under the influence of the electros seems to increase the
magnetic flux and makes the maximum flux more permanent. Under
no conditions hammer the magnets when the current is off or when
they are removed from the charging apparatus, as this seems to lit-
erally knock the magnetism out of them. Leave the current on for
at least two minutes.

IGNITION. TIMING, ETC.

BWure s/iutting off the c

urrent pla

e a soft iron

bar or "kee

per" B

across the poles of the ma

giiets as i

dicated by the dotted lines and

keep this bar on i.

ntil the

magnets

arc well sho

ed down o

er the

pole pieces of the

nagneto

Withou

the keeper, permanent magnets

lose Iheir strength

in a very short tin

ne after the n

magnetizing

urrent

is shut off. Neve

allow

magnets

o lay around

after disse

mbling

without pkcing tw

o or thr

ee keepers

across their

poles.

Fig. 3 shows a

method

of chargr

ng tnagnets

without the

use of

the apparatus just

described. It is

tedious and

crude method, but

often is the only m

eans th

t the layn

an has of pe

forming (he

work.

Pig. 2.— Charging Magnet.

Fig. 3.— Temporary Rig.

Two coils of wire, C and C', are wrapped around the legs of the
magnet A in opposite directions. The wire should be comparatively
heavy, say No. 18 gauge, and there should be at least 75 turns on
each leg. After completing the winding a keeper B should be placed
across the poles X and S. The ends L and L^ should be connected
to the source of direct current.

Tap the magets as before while the current is passing, and at the
end of two minutes rapidly slip off the coils, replace the keeper, and
mount on magneto. If electric light current is used from 110 volt
main it will be necessary to introduce some form of resistance into
the circuit to prevent too sudden a rush of current. About 10 amperes
will usually be required, and even more if you can obtain it. With a

IGNITION, TIMING, ETC. '2.2S

storage battery, the coils must not be left in circuit more than 5
seconds, for the battery is likely to be damaged through the heavy
discharge of current due to the low resistance of the coils.

Do not forget to wind the coils in opposite directions, nor to use only
direct current. The wire should be copper, preferably insulated with
a double cotton cover.

Before starting the charging process with the first method, in cases
where you do not know the character of the current, turn on the cur-
rent and place the keeper across the poles of the magnets. If a
humming noise is heard do not attempt to charge, as the humming
is always due to an alternating current.

TIMING MAGNETOS

•

In any gas or gasoline engine, combustion must be complete at the
end of the compression stroke, or as the crank pin reaches the upper
dead center. As all mixtures require a certain length of time to com-
plete combustion after the application of the spark it is evident that
the spark must occur slightly before the end of the compression
stroke. This "advance" of spark, numerically, depends upon the qual-
ity of the mixture, upon the compression pressure, and upon the speed
of the engine. Poor mixtures require more time for combustion than,
normal mixtures, while high compressions reduce the volume through
which the flame must spread and therefore reduce the advance. High
speeds require more advance than low since there is less time in
which to burn the mixture and consequently the combustion must
be started earlier.

From the three variable quantities it will be seen that the magneto
must be capable of adjustment to meet all running conditions or so
that the sparks can be made to occur over a wide range of piston
positions. A fourth factor of the timing range is that of engine con-
struction for, with all other items equal, the advance and retard are
affected by the size and shape of the combustion chamber and the
position of the spark plugs.

Unlike the case with the common battery system, the magneto of
the true high tension or transformer has no vibrator lag, and little
if any, electrical inertia. For this reason the advance and retard angle
of the magneto is less than with the ordinary battery equipment.
Since all cylinders are fired by the same magneto circuit breaker,
every cylinder receives the spark at the same point in the stroke.
With batteries the latter condition is only approached with the master
vibrator system.

In general the magneto is timed or geared to the engine in such
a position that the spark occurs on, or a trifle before, the end of the
compression stroke with the timing lever in the fully retarded position.

S^^ IGNITION, TIMING, ETC.

It should be noted here that in all cases measurement is taken with
the magneto fully retarded. With some engines, notably those of the
"T" head type, the spark is made to occur at full retard at a point
% inch before the piston reaches the end of the stroke. The exact
point is determined to some extent by the valve setting or construc-
tion of the combustion chamber. Some engines require considerable
advance while others will stand none, or very little. The best point
on engines not already equipped for magnetos is found by trial.

In the case of timing magnetos on engines with marked fly-wheels
thcf timing is a simple matter, for then one only has to place the
pointer opposite to the marks on the fly-wheel and set the breaker
to open at this point with full retard. For simplicity in connecting
up the plugs, start with cylinder No. 1 in the firing position as indicated
on the fly-wheel.

Before continuing further on the subject of timing it should be
understood that the spark occurs at the point where the circuit
breaker contacts are just barely beginning to open. The spark occurs
when the contact is broken by less than 0.005 inch, so that the points
must be observed very carefully or measurements must be taken from
the armature or from points marked by the builder of the magneto.
A small error in this observation will make a very considerable error
in the timing. Some makers provide a key, which, when inserted into
the armature through the frame, hold the breaker at the point where
it just starts to open. This is very convenient as it requires no par-
ticular care on part of the person doing the timing. With some
magnetos, a gauge is provided, while with others it is necessary to
measure the distance between the edge of the armature shuttle and
the edge of one of the pole pieces. Owing to these differences it
will be necessary to specify procedure with several of the principal
makes of magnetos.

The first step in timing will be to set Cylinder No. 1 on the top
center (or in firing position if marked on fly-wheel). In some motors
the firing point "No. 1 ," is found near the top center "No. 1. T. C,"
while in others the two points coincide on the mark "No 1. T. C."
Look carefully for the firing point and if found set this opposite to
the pointer instead of the T. C. mark.

When the wheel is not marked we must set the engine by directly
measuring the piston position through the cylinder head. Access to
the piston in most cases can be had through the relief cocks or plugs
in the cylinder head or in the cases of two part cylinders by removing
the head entirely. A bicycle spoke, knitting needle, or small rod can
be dropped through the plug or relief cock until the end rests on top
of the piston. The engine can then be slowly turned over on the
compression stroke until a point is found where further turning in

IGNITION, TIMING, ETC. 225

either direction causes the rod to move up or down. The highest
point recorded by the rod is the upper dead center. (See Page 215.)

This measurement is crude, impossible for use in correctly setting
valves, but close enough for ignition. Should the engine be of the
"offset" type accurate setting may be performed by the method shown
on Page 205. But even with the offset engine, the rod measurement
is close enough for timing the ignition. Fly-wheel indexing is
described on Page 217 for battery ignition by Fig. 1 and will give an
idea as to the procedure with a magneto setting. When once the
center is found it should be permanently marked on the fly-wheel for
future reference. Find and mark the bottom center in the same way.

Not only must Cylinder No. 1 be set on dead center but it must
also be placed on the compression stroke, for as the complete cycle
is performed in two revolutions it is an easy niatter to cause the
ignition spark to occur at the end of the exhaust stroke which is also
on the upper dead center. Should this error be made the engine of
course would refuse to start.

The compression stroke can be identified by the • order in which
the valves of a given cylinder open and close. Turn the engine over
slowly by hand in the direction in which it rotates when in operation
and carefully watch the movements of the inlet and exhaust valves
of Cylinder No. 1. Finally a point will be found where the exhaust
closes and the inlet opens, together or nearly together. This is the
beginning of the suction stroke. On turning a little more than one-
half revolution, the inlet valve will be observed to close. This is the
beginning of the compression stroke. Now keep on turning in the
same direction until the top center mark already located on the fly-
wheel comes opposite to the pointer. This is the upper end of the
compression stroke of Cylinder No. 1. Mark on wheel (No. 1 T. C).

Of course the approximate end of the compression stroke can first
be obtained in this way, and then the exact dead center can be found
afterwards. This is a matter of individual habit. In any case mark
the results on the wheel before going further. Block the wheel in
the dead center position so that it cannot move and mount the magneto
in place with one of the magneto couplings loose on the shaft.

If you are so fortunate as to possess a magneto with a timing key
ior holding the arjjiature and breaker in the firing position, turn the
armature over unlil the key slips into position before mounting
magneto on the motor bed. This holds the breaker just open in the
firing position, and with the engine on dead center, it simply is a
matter of bolting the magneto on the bed and fastening or keying
the loose magneto coupling tight to the shaft. With this type of
magneto, the timing is now completed, at least for trial. The Eise-
mann Type EMA and the Unterberg-Helmle (U and H) are mag-

226 IGNITION, TIMING, ETC.

netos having this feature. Remove the key from the armature and
turn engine slowly over by hand to see that nothing sticks or binds.
With the Eisemann, the armature shaft should be turned over until
the number "1" appears at the peephole on the distributer plate top
before inserting the timing key or before mounting the instrument.

Before setting any magneto see that the timing lever is set in the
fully retarded position. With the Eisemann Type EMA magneto, the
lead from the distributer connection No. 1 can now be connected with
the spark plug in cylinder No. 1, and the remaining plug wires con-
nected up according to the firing order of the motor. The order in
which different numbers of cylinders fire can be found from the
chapter on Valve Setting, Part X, pages 201 to 208. The numbers
appearing in the peepholes are not the cylinder numbers to which the
next wire is to be connected but only indicate which distributer ter-
minal is active at that time. The terminal numbers give the successive
order in which the brush makes connection with the terminals. See
Fig. 3 on Page 99, and Fig. 10-A on Page 110. (The plugs are not
in proper firing order as shown, but show the order in which they
are connected by brush.)

Example. Say that we have a four cylinder motor in which the
cylinders fire in the order, 1-3-4-2, and that we now have Cylinder
No. 1 connected with the magneto to terminal No. 1. As the dis-
tributer brush connects with the terminals in their numerical 'order,
tlie next live terminal will be No. 2. Since the next active cylinder,
after Cylinder No. 1, will be Cylinder No. 3 according to the given
firing order, it is evident that a wire from terminal No. 2 should
connect with plug in Cylinder No. 3, Cylinder No. 4 will be connected
to terminal No. 3, and Cylinder No. 2 will be connected to terminal
No. 4.

For firing order of six, eight and twelve cylinders see pages 201 to
end of chapter on valve timing. Part X.

In the above description we have assumed that the fully retarded
spark is to occur exactly on dead center and that the magneto is
provided with a timing or setting key. In practice, we often have
different conditions to meet, for we often fire before dead center and
have a different method of setting the magneto circuit breaker. The
notes on the distributer connections, however, hold good for any
magneto with the same number of cylinders.

Assuming for the present, that we are still firing on dead center,
we will consider the method adopted on the Bosch magnetos^. Types
"D," "DU-4," and "DU-6," for finding the point of breaker opening.
For the details of construction see longitudinal section on Page 101
on which will also be found, the part numbers referred to.

The connecting bridge (12) and the dust cap (21) are removed to

IGNITION, TIMING, ETC. 22;

determine the armature position. Fasten the magneto firmly on the
motor bed, and with the driving pinion or coupling loose on the
magneto shaft. The engine is supposed to be on dead center. Now
turn the armature shaft slowly by hand and look through the opening
left by the removal of the dust cap (21). As the armature rotates,
an iron surface, and a black coil appear into view alternately, running
past the pole piece. The circuit breaker will open after the iron edge
of the armature has left the edge of the pole piece by the amounts
given in the following table with right hand rotation (when facing
shaft end of magneto), the gap between the armature and pole will
be at the left. With left hand rotation the gap will be at the right.
The length of the gap should be —

For 3 Cylinder Engine.. 11 to 13 millimeters. .0.4331 in. to 0.5118 in.
For 4 Cylinder Engine.. 14 to 17 millimeters. .0.5512 in. to 0.6693 in.
For 6 Cylinder Engine.. 21 to 27 millimeters .. 0.8268 in. to 1.0630 in.

When the gap is measured as above, for the required number of
cylinders, hold the armature in place and firmly pin or key the loose
coupling or pinion to the shaft. This is now in the correct firing
position. Replace parts (12) and (21), and connect up leads to plugs
as before described, taking the leads to the plugs in the order that
the brush makes connection with the distributer terminals (at the
magneto end), and connecting the motor ends of leads in the firing
order. With Cylinder No. 1 in firing position, run lead from Plug
No. 1 to the terminal connecting with that distributer segment on
which the brush is resting. Determine the distributer rotation and
find the next sector energized. A wire from this sector will lead to the
cylinder next in firing order, and so on.

In any other magneto, the spark must be timed in the magneto by
very closely observing the point at which the breaker contacts open.
When, as in the majority of cases, the breaker lever is actuated by a
cam striking a flat or roller follower, note particularly the point at
which the cam touches the follower, and neglect the contacts for the
time being. Turn the armature back and forth until the cam barely
touches the follower plate or roller on the contact arm. An extremely
light pressure further applied will start to separate the points. This
is the point at which the spark will occur.

Usually this is far more difficult to perform than to describe since
the pull of the magnets at this point tend to suddenly "flip" the
armature over, and past the breaking point. With some magnetos
it is almost impossible to hold the armature shaft against the pull
of the magnets when holding the shaft with the fingers. After you
have tried this job several times you will appreciate the genius of
the man that devised the setting key. Turning the shaft by means
of the coupling make the matter easier for the reason that there is

228 IGNITION, TIMING, ETC.

more leverage, but in some cases the construction prevents this from
being done.

When the spark is set to occur before the piston reaches center, the
engine is first centered and is then turned back against rotation until
the measuring rod moves down the required amount. Block the
motor at this point, call this your center, and proceed setting the
magneto as before. When the engine is not marked it is best to set
the spark on the true dead center, first, for experiment. If this does
not give good results then set the spark to occur before center. The
Eisemann Company have a special coupling in which the two halves
are divided into degrees. When the magneto is once set and is not
satisfactory, the halves may be moved on one another according to
the scale until the desired results are obtained without dismounting
the magneto.

When a specific timing is given, by the maker of the motor, and
the wheel is not marked, it is generally given in degrees measured
on the crank-circle. This is an awkward measurement to make for
the average man, but by aid of the magneto chart on pages 225-227
it is easily performed, since by this means the degrees can be con-
verted into inches of piston travel and measured through the cylinder
head by the rod previously described. With the stroke known, start
at the bottom of the chart and follow up to the diagonal line that gives
the required degrees. Follow horizontally to the left-hand column of
figures which will give the distance of the piston below the top center.

Example. A motor has a stroke of 5 inches, and the fully retarded
spark is to occur 25 degrees before top center. Find distance of
piston below top center in inches.

Start at 5 inches at bottom of chart and trace up to the intersection
of this line with the diagonal 25. Now follow horizontally to the left
from this point to the left vertical row of figures where it will be
found that the distance is 9/32 inch. After setting engine on top
dead center, insert rod through head and turn crank against rotation
until the rod sinks 9/32 inch. The crank is now at an advance angle
of 25 degrees.

The timing of the magneto given in this article assumes that the
breaker contacts are new or at least in good order. When thor-
oughly cleaned and in good order, the points should not be apart by
more than 1/64 inch when fully open. If the gap is much wider than
this it will interfere with the timing. Some makes, notably the Bosch,
have a gauge for setting this distance. Due to burning and wear, this
gap gradually increases, so that to maintain correct timing, the width
of the gap between the contacts should be occasionally inspected.
In the Remy transformer type the gap should be from 0.025 inch to
0.03 inch. If motor misses when idling or pulling light the gap should
increased. If it misses when pulling heavy loads, decrease the gap.

PART XIII

STORAGE BATTERIES AND STARTING REPAIRS

CARE OF STORAGE BATTERIES.

Modern storage cells do not require a great deal of attention, but
like any other part of the car do require occasional inspection and
considerate treatment. When trouble is experienced with the cir-
cuit, and you are sure that the battery is at fault, proceed carefully
for it is an easy matter to ruin the cells through improper treatment.
The contents of the following table should be carefully observed in
making any corrections to a lead and sulphuric acid type battery.

Discharged Cells. Never allow the voltage to drop below 1.8
volts per cell, for below this point there is danger of sulphation. It
is far better to start recharging when the voltage drops to 1.9. The
hydrometer test gives even a better idea of the condition of the bat-
tery than the voltmeter since it takes the condition of the electrolyte
into consideration.

When all of the cells are in good condition their gravity will test
within 25 degrees or "Points" throughout the series. A wider varia-
tion between the individual cells indicates trouble in the high or low
cell.

Gravity above 1,200 indicates that the cells are more than half
charged. Gravity below 1,150 indicates that the cells are completely
discharged. Maximum gravity at full charge is 1,280 to 1,300.

Evaporation. In the course of time there is a loss of solution
due to evaporation and to the spray passing through the vent holes.
In all cases the level of the electrolyte should be kept above the tops
of the plates since a low level causes sulphation of that part of the
plate that comes into contact with the air and also causes a reduc-
tion in the current capacity of the cell.

Never pour pure acid or a strong solution of acid into a cell in
renewing the electrolyte. The acid never mixes with the solution
immediately and therefore soon attacks the active material on the
plates. Renew all of the solution at the proper specific gravity after
thoroughly mixing in another vessel, and allow it to cool thoroughly
before pouring it into the cells. If it is desired to use the old solu-

229

-oU IGNITION, TIMING, ETC.

tion, remove it from the cells before adding the acid, mix thoroughly
with the new, and cool before pouring back.

If any particular cell regularly requires more water than the
others, a leaky cell is indicated. Repair or renew the cell imme-
diately. Sometimes a defective vent will cause excessive waste of
electrolyte.

Low Gravity Cells. When the gravity of any one cell is lower
than the others, say by more than 25 points, and if successive reaclings
show that this difference is increasing, the cell is not in good order.
If there is no leak in the battery jar, the low gravity generally indi-
cates that there is an internal short circuit due to sediment, shedding,
or buckled plates, and this trouble should be corrected immediately
only by an expert battery man. Continued short circuits will even-
tually destroy the cell for the reason that they act in the same way
as a continuous external load.

Standing Idle. A battery which is to stand idle for any length of
time should first be fully charged as a protection against current
leakage. It is not wise to permit a battery to stand idle for more
than six months with the electrolyte in the cells. A battery not in
active service should receive a freshening charge at least once in
every two months. It should be given a thorough charge after an
idle period before being replaced in service. After standing idle for
two months or more it should be charged at one-half the normal rate
to the maximum gravity.

Before leaving the battery for a prolonged idle period, disconnect
the wires leading to the various circuits so that it will not lose its
charge through any slight leaks in the wiring of the car. In cold
weather it is best to store the battery in a heated room, for the elec-
trolyte freezes at 20 degrees below zero.

When the batteries are to be left out of service for more than
six months, proceed as follows: Discharge at the rate of about one
ampere until the lamps burn with a dull red glow, empty out the acid
and wash cell out thoroughly with clean water. Fill battery up with
distilled water and discharge until there is no further current. Repeat
the operation once more, and then fill up to the vent tubes with dis-
tilled water. The battery can now be set away for an indefinite period,
the battery being visited occasionally to make up the water lost by
evaporation.

Another method is as follows: Fully charge battery, empty acid
from cells, clean out thoroughly, fill with distilled water, and let stan^
for a few moments. Empty cells, and repeat the operation three
times, about one day between operations. Drain battery dry and set
away in dry place.

Voltage Too High. Never allow the voltage to rise above 2.65

IGNITION, TIMING, ETC. S61

volts. A high voltage denotes that the density of the electrolyte is
too high and therefore should be diluted with water.

Electrolyte or Solution. Only the purest of acid and distilled water
should be used in making up the battery solution. Never use the
commercial sulphuric acid commonly sold at drug stores as this con-
tains traces of iron, platinum and lead which are highly injurious to
the cell. Mix the electrolyte only in glass or porcelain vessels, as
the acid will dissolve enough of a metal container to work havoc
with the plates. Never stir a solution with an iron rod.

The electrolyte consists of one part of chemically pure sulphuric
acid to four parts of distilled water. Pour the acid into the water,
never the water into the acid. Severe explosion is likely to take
place under the latter condition. Rain water can be used in an emer-
gency, but should not be left in the cells longer than absolutely
necessary.

Loss of Capacity. Loss of capacity may be caused by the active
material shedding from the plates, by internal short circuits, by sedi-
ment in the bottom of the cells, by broken separators, by excessive
temperatures or by the shrinkage of the active material.

Open Vents. When charging a battery be sure that the vent caps
are fully open, for the generation of gas due to the charging process
may burst the cell if not liberated.

Full Charge. A cell may be considered fully charged when, with
the rate of current flow specified by the makers, all cells are gassing
freely (bubbling) and evenly and the gravity shows no increase for
one hour. The gravity should never be lower than 1,150 before
charging. Six-volt batteries cannot be overcharged if the voltage of
the generator is below 7 volts.

Care of Terminals. Keep the battery terminals thoroughly
greased to prevent corrosion and the breaking of the conductor wires.
The acid spray carried through the vent caps not only destroys the
terminals but is also likely to carry the dissolved metal back into
the battery solution and ruin the plates.

Charging. Start charging as soon as the voltage drops below 1.8,
taking care not to exceed the charging rate specified by the maker of
the battery. Be sure that the vents are open before closing the charg-
ing switch. When connecting the charging current to the batteries
be sure that the positive pole of the line is connected to the positive
pole of the battery so that the current flows "backwards** through the
battery or in a direction opposite to that given by the cells when dis-
charging. The positive wire is marked "POS" and is generally
painted red.

-- IGNITION, TIMING, ETC.

DYNAMO AND MOTOR TROUBLES.

While there is comparatively little trouble with the motor or
dynamo end of the self-starting system, all of the moving parts will
wear in the course of time and will require attention. The majority
of the diseases to which the dynamo is heir can be cured by the owner
if he will take the trouble to systematically observe the symptoms of
his patient and proceed carefully in accordance with the following
instructions.

Primarily, the principal indications of trouble are sparking at the
brushes and commutator, heating of the armature or field, noise, failure
to generate in the case of a dynamo, or failure to start in the case of
the motor. Before proceeding with dynamo or motor tests be sure
that the battery and the external wiring are not at fault and that the
switching and regulating systems are working freely. Wire is usually
the part of the circuit that is the least protected from the effects of
moisture and abrasion and therefore is the part to be first placed under
suspicion. Even when protected with a metal conduit the insulation
of the wire often deriorates before trouble is experienced with the
battery, motor or dynamo.

Remember that moisture and oil are two of the greatest enemies
of insulation and therefore of the electric system as a whole, and do
not fail at all times to protect the windings and wiring if the most
important point has been neglected by the maker of the machine.

SPARKING AT THE BRUSHES.

Remove hand-hole plates or doors above the commutator and exam-
ine the parts when the machine is generating or when using a maxi-
mum amount of current. Note whether the connections are tight,
commutator is rough or cut, or whether the brushes are pressing with
the proper tension on the surface of the commutator. Clean all of the
current carrying surfaces before proceeding further with the
inspection.

Poor Contact. Clean commutator thoroughly with gasoline after
removing brushes. Soak brushes thoroughly in gasoline and carefully
scrape off sharp corners on the bearing surfaces. If brushes are of
carbon, alcohol is better than gasoline or benzine.

See that the bearing surface of the brushes is perfectly smooth and
glossy and that the brush bears evenly on the commutator throughout
its entire width. Slightly bevel the trailing and leading edges so that
there is no danger of the corners scratching the commutator. If there
are low spots in the bearing face of the brush there will not be suf-
ficient area for the conduction of the current. Grind them to a unt»

IGNITION, TIMING, ETC. 233

form, even, concave surface with a piece of sand paper mounted on a
block curved approximately to the outline of the commutator.

Tension Springs. The tension springs feeding the brush often
slacken, lose their temper, or slip from their moorings so that the
brush is not held on the commutator with sufficient pressure. This
allows the brushes to joggle and hence to spark. Tighten the spring
so that it gives a firm bearing yet without excessive friction on the
commutator. Do not make it any heavier than necessary to stop the
sparking. The slot in the brush holder in which the brush slides is
often either too large or too small for the brush. If too large the
brush will joggle, if too small or tight, the brush will bind so that the
spring will not be able to feed it with the proper pressure on the com-
mutator. See that the connection between the brush and the brush
holder is electrically perfect so that current can enter the brush prop-
erly. See that the brush holder allows the front edge of the brush
to bear exactly parallel with the edges of the commutator bars. A
brush worn too short may release the spring tension.

Chattering. A chattering noise while the machine is running, with
an excessive vibration in the brush, may be caused either by the brush
or the commutator. If in the brush, it is generally caused by a loose
brush or loose brush holder, by a very hard carbon brush, or by insuf-
ficient spring pressure. If the commutator is lubricated by a slight
amount of vaseline applied with a rag it will often be found to stop the
noise. Never use oil, especially when applied with an oil can. If it
must be used slightly dampen a soft rag and apply while the machine
is running. Paraffin wax applied with slight pressure is an excellent
lubricant.

Grooves. Grooves either in the brushes or commutator are often
produced by grit or hard spots in the brushes. Use the best grade of
carbon (Soft), or the proper grade of copper for the brushes.

Uneven Spacing. The tips of the brushes should bear on the com-
mutator at points diametrically opposite to one another. The truth of
this position can be determined by counting the number of commu-
tator bars that lay on either side of the brush. This number should
in all cases be equal. Uneven spacing is not a common trouble with
automobile generators as the brush holders are generally fastened in
a fixed position.

Dirty Commutator. Clean with gasoline or benzine. See that there
are no copper filings or dust on the insulation at the ends of the bars
or between the lugs at the point where the armature wires are fastened
to the commutator bars. If oil is thrown from the bearings upon the
commutator a shield should be installed to protect the insulation.

Grooves. If the surface of the commutator appears to have a series
of fine cuts or grooves grind down with a piece of very fine sand or

'^^■^ IGNITION, TIMING, ETC.

glass paper mounted on block. The face to which the sand paper is
applied should be curved approximately to the radius of the commu-
tator so that the cutting will be even. If the grooves are very deep
it is easier to remove the armature and turn the commutator down on
a lathe. This also insures a perfectly cylindrical commutator. While
the grooves are generally caused in the first place by the brushes, the
grooves on the commutator react on the brushes causing rapid wear,
sparking, and brush chatter.

Never use emery in grinding down, nor carborundum as these
materials have the property of sticking into the copper bars after the
operation. Thoroughly clean off all copper dust and sand particles
caused by grinding.

When the cutting of grooves is persistent even after having changed
the brushes, look to the tension springs of the brush holder, for these
may be causing too much pressure on the brushes. The armature or
commutator should have a small amount of end play in the bearings to
prevent the brushes from tracking continually in one path.

Burned Bars. Black burned spots on the commutator may be
caused by chattering brushes, insufficient spring tension, or by open
circuit or grounds in the armature windings. A ground in a commu-
tator bar or a short circuit between two adjacent bars will also cause
a burned spot. Burning due to brush trouble is generally spread uni-
formly over the entire surface of the commutator, and in the path of
the brushes. Burning due to armature winding troubles occurs at
only one or two bars, the principal burning being at the trailing edge
of the bar, or at the point where the last live bar leaves the brush. If
this is allowed to continue, the insulation will be eventually burned
out between the bars, and the entire commutator grounded. Burned
bars should be sand papered down as described in (8), and the insula-
tion between the bars should be repaired by digging out the burned
mica and replacing the burned spot with fresh mica mixed in shellac.
Dig out only that portion that is burned.

Out of Round. When the commutator wears out of round, it causes
the brushes to vibrate rapidly up and down, thus producing burns and
unnecessary vibration. It also unbalances the rotating mass to a cer-
tain extent and is a factor in producing bear-wear and uncomfortable
noise. The only remedy is to turn the commutator down in a lathe.

High Bar. Owing to the loosening of the end retaining rings or
to shrinkage of the commutator insulation, a bar often rises above the
adjacent bars, causing burns, noise and^unnecessary brush wear. When
this occurs the armature should be removed and sent to a competent
armature repair man for this is a trouble that cannot usually be made
satisfactorily by the amateur. If the repair must be performed by the
garage man or owner it can sometimes be done by tapping down the

IGNITION, TIMING, ETC. ^ii5

bar with a piece of wood and a mallet, tightening the end nuts that
hold the bars on the commutator spider, and then turning the whole
down on a lathe. Care should be taken not to injure the insulation at
the ends of the bars.

Low Bar. Symptoms and treatment the same as for high bar.

Weak Magnetic Field. A weak magnetic field will cause sparking,
especially in the case of a motor, since this produces a change in the
commutating point on which the brushes should rest. A weak field
may be caused by a poor external connection, which in turn causes
undue resistance in the field circuit, or by a short circuit, broken field
wire, or dampness in the windings. A grounded or wet wire leading
to the field winding will also cause a weak field. In a generator, a weak
field will cause a fall in voltage when the fault is in the shunt field,
and a maintained high voltage when the fault is in the series field, the
lighting generators all being of the differentially wound compound
type.

A weak motor field causes a reduced torque with a load, and over-
speeding with the load removed. The only remedy is to replace the
wires leading to the fields externally, or to rewind the field coils if the
trouble is internal. If a switching device is included in the field circuit
see that it is making proper contact and that all connections are tight.

Excessive Loads. When the motor or generator are carrying an
excessive current, sparking is almost certain to appear. An excessive
current in a generator may be caused by a defective current regulating
device which causes the voltage to rise too far above the voltage of the
battery, or it may be caused by a defective field winding in cases where
no regulating device is used. The faulty field results in a high charg-
ing voltage. Sparking sometimes occurs when the voltage of the bat-
tery drops to a very low point due to large drafts of current by the
battery. ^

An excessive motor load may be caused by a cold stiff engine, by
leaving the clutch in when starting the engine, by attempting to drive
the car with the starting motor, or by having the ignition advanced
too far. Hot bearings in either the starting motor or the automobile
engine will produce the same results.

Short circuits and grounds in the wires leading to the battery and
in the external circuit are often the cause of abnormal currents through
the generator. Test out the wiring on the chassis of the car.

Friction. Try out the engine, starting motor, and generator for
bearing and gearing binding and friction. Be sure that the pistons
are not stuck, and that no parts are frozen together during cold spells.
It should be remembered that an engine always cranks heavier in cold
than in warm weather owing to stiff oil.

Short Circuited Armature Coils. Remove all filings, copper dust.

236 IGNITION, TIMING, ETC.

solder and other metallic connections behind the commutator bars.
See that the clamping rings are perfectly insulated from the bars, and
that no bridge exists through dust or solder. Test for grounds and
see that the brush holders are perfectly insulated.

Broken Armature Coils. Examine commutator bars at the point
where the connection is made to the wires leading from the armature
windings. If a loose or broken wire is found at this point it should
be replaced. If the coil is broken in the armature, rewinding is the
only sure remedy, but it can be temporarily repaired by bridging across
the broken coil on the ends of the commutator lugs. Connect the bar
leading to the broken coil to the next bar on either side across the
mica. In cases where the brush holders can be shifted or the brushes
turned in the holder, the brush should be turned so that it will bridge
across two bars simultaneously. Temporarily, the two bars lying on
either side of the bar that connects with the broken coil can be con-
nected together with a jumper, and the ends of the broken wire
removed from the lug.

In adopting any repair that shorts or cuts out an armature coil,
remember that the voltage and speed will be varied according to the
number of active coils cut out. Prompt rewinding is the only safe
course.

HEATING.

Overload. Too many lights, or too many amperes supplied to or
taken from the machine may cause heating. Defects in the cut-out
mechanism, or in the field windings will cause overloads. Running
the car on the starting motor will cause excessive heat, as will a stiff
cold engine.

Defective Cut- Out A defective cut-out will allow the current from
the battery to rush back through the generator when the voltage of
the generator falls below the voltage of the battery.

Short Circuit (External). A short circuit in the wires leading to
the various parts of the car will put a heavy load on the generator and
consequently will cause over-heating.

Moisture. Dry out the fields or armature by gentle heat either in
an oven or by sending a small current through the coils. When it is
known that the motor has been wet if should be dried before running
it, or before trouble has developed.

Short Circuit (Internal). A short circuit due to dirt at the com-
mutator, or to abraded insulation in the armature winding will cause
heating. A ground in the armature windings will often have the same
effect as a short circuit. In the field coil a short circuit or moisture
will produce a weak field (See 13), causing trouble at the brushes and
the commutator, or heating in the shunt fields of the generator.

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