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MOTOR-CAR PRINCIPLES
MOTOR-CAR PRINCIPLES
_THE GASOLINE AUTOMOBILE_
BY
ROGER B. WHITMAN
ILLUSTRATED
[Illustration: Decoration]
NEW AND ENLARGED EDITION
D. APPLETON AND COMPANY NEW YORK, LONDON MCMX
COPYRIGHT, 1907, 1909,
BY D. APPLETON AND COMPANY
INTRODUCTION
The development of the gasoline automobile at home and abroad has
produced a great variety of designs, good, bad, and indifferent, but
the advancement of the industry has weeded out the unsatisfactory and
improved the good until with few exceptions the leading makes show
a striking similarity in all but details. The advantages of certain
forms of construction have been recognized, and their adoption by the
large majority of makers has produced what may be called a standard
type.
The object of this book is to explain the principles that underlie
automobile construction and operation, and to illustrate the
movements and mechanical combinations adopted in present-day
practice. It is not the intention to explain the exact details of
construction of the different cars, and the illustrations have
been prepared with the sole object of making the principles clear,
for with an understanding of these there should be no difficulty in
comprehending any particular application of them.
The lubrication table on pages 244 and 245, which was prepared by Mr.
T. D. Hanauer, is reproduced through the courtesy of the _Scientific
American_.
* * * * *
The advantages of magneto ignition for internal combustion engines
are so obvious that designers and inventors have directed their
attention to the perfection of apparatus that will improve present
methods. The number of systems proposed for the purpose is very
large in comparison with the number in actual and practical use,
and as in a work of this size it would be impossible to describe
the many methods for the application of the magneto that are on the
market, attention has been given only to those that are in actual,
everyday use. The absence of a practical treatise on the principles,
application, and care of low and high tension magnetos is the reason
for the addition of the appendix to this work.
R. B. W.
CONTENTS
CHAPTER I
GASOLINE-ENGINE PRINCIPLES
PAGES
Properties of gases—Steam-engine principles—Gasoline-engine
principles—Combustion and explosion—Events of cycle—Four-cycle
and two-cycle engines—Strokes of cycle—Fly wheel—Valves—Inlet
stroke—Inlet valve closing—Compression-combustion stroke—Advantages
of compression—Instant of ignition—Advancing and retarding
ignition—Limit of compression—Power stroke—Heat losses—Opening of
exhaust valve—Exhaust stroke—Clearance—Back pressure—Steam and
Gasoline engines compared—Gasoline—engine power 1-19
CHAPTER II
ENGINE PARTS
Crank shaft—Crank-shaft bearings—Relative position
of cranks—Connecting rod—Wrist pin—Piston and piston
rings—Automatically and mechanically operated valves—Cams
and cam shaft—Secondary shaft—Two-to-one gears—Valve-lifter
rod—Valve locations—Muffler—Engine cooling—Cooling by
Water—Pumps—Radiators—Pressure and gravity systems—Cooling by
air—Lubrication 20-36
CHAPTER III
ENGINE BALANCE
Vibrations of engine—One-cylinder engine—Horizontal
double-opposed—Two-cylinder vertical—Four-cylinder—Firing
order—Balance of three- and six-cylinder engines—Comparison of engine
types 37-46
CHAPTER IV
TWO-CYCLE ENGINES
Principle—Construction—Ports—Cycle—Action—Advantages and
disadvantages 47-51
CHAPTER V
CARBURETION AND GASOLINE FEEDS
Carburetion—Carburetor—Carburetor parts—Carburetor action—Necessity
for auxiliary air—Auxiliary air inlet—Automatic and mechanically
controlled air inlet—Carburetors with side and central
mixing chambers—Mechanically controlled carburetor—Surface
carburetors—Gravity feed—Pressure feed—Check and relief valve 52-73
CHAPTER VI
IGNITION
Ignition system—Electric current—Parts of ignition system—Flow
of current—Conductors and insulators—Resistance—Measurements of
current—Lead and return wires—Grounding the return—Generators—Dry
cell—Storage cell—Electrolyte—Hydrometer—Battery connections:
series, parallel and multiple—Magnetism—Magnets—Magnetic
lines of force—Magnetic field—Field and armature—Magneto and
dynamo—Switch—Switch parts 74-90
CHAPTER VII
IGNITION—(_Continued_)
Ignition systems—Make-and-break
system—Igniter—Tappet—Connections—Primary induction coil—Action of
coil—Induced current—Magneto—Jump-spark system—Secondary induction
coil—Primary and secondary circuits—Timers—Mechanical and magnetic
vibrators—Spark plug—Circuit—Condenser—Secondary distributer 91-111
CHAPTER VIII
TRANSMISSION
Transmission parts—Clutches—Friction-cone clutch—Reversed
friction-cone clutch—Multiple disk clutch—Internal expanding
clutch—Change-speed mechanisms—Sliding gear: progressive and
selective types—Use of clutch in changing gear 112-131
CHAPTER IX
TRANSMISSION—(_Continued_)
Planetary type of change-speed mechanism—Individual clutch—Friction
type—Final drive—Turning the direction of the power—Bevel
gears—Single-chain drive—Propeller-shaft drive—Universal
joints—Live axle—Floating axle—Torsion rod—Double-chain
drive—Jack shaft—Differential—Bevel-gear differential—Spur-gear
differential—Driving-gear ratios 132-160
CHAPTER X
RUNNING GEAR
Steering—Front axle—Steering knuckles and arms—Drag link—Steering
principles—Steering mechanisms—Brakes: contracting and
expanding—Brakes: single- and double-acting—Running brake—Emergency
brake—Engine as a brake—Brake equalizer—Tires—Tire construction—Tire
inflation—Skidding—Antiskid devices—Springs—Shock absorbers—Distance
rods 161-178
CHAPTER XI
TROUBLES
Ignition—Circuit—Battery—Magneto—Coil—Spark
plug—Igniter—Timer—Secondary
distributer—Switch—Gasoline—Tank—Carburetor—Compression—
Cooling—Freezing—Lubrication
179-202
CHAPTER XII
LOCATING TROUBLE
Make-and-break ignition—Jump-spark ignition—Carburetor—Engine will
not start—Engine will not deliver full power—Weak explosions—Missing
explosions—Missing at high speed—Engine starts well, but comes to a
stop—Overheating—Engine comes to a stop—Noises 203-219
CHAPTER XIII
MAINTENANCE AND CONSTRUCTION
Inspection—Washing the car—Tires—Care of the engine—Care of the
chains—Valve grinding—Care of the steering mechanism—Care of the
springs—Adjusting the vibrators—Matching coils—Adjusting the
carburetor—Setting the valves—Ignition wiring 220-242
LUBRICATION TABLE 244-245
APPENDIX
Magnetism—Induction—Magneto principles—General magneto troubles—Low
tension ignition system—Setting up, care and troubles—Low tension
magneto with secondary coil—Direct high tension magneto—Bosch
two-spark magneto—Bosch four-spark magneto—Dual systems—Magnetic plug
ignition—Inductor magnetos 247-326
TESTING CHART _Between_ 326 and 327
INDEX 327-339
LIST OF ILLUSTRATIONS
FIG. PAGE
1. Engine Actions 3
2. Gasoline Engine Cycle 7
3. Gasoline Engine in Section 21
4. Crank Shafts 22
5. One-Throw Crank Shaft 23
6. Connecting Rod 23
7. Piston and Piston in Section 24
8. Piston Rings 24
9. Conical Valve Seat 25
10. Automatic Inlet Valve in Cage 25
11. Cam Action 27
12. Four Arrangements of Valves 29
13. Circulation of Cooling Water 31
14. Types of Pumps 32
15. Radiator Constructions 33
16. Radiator and Fan 33
17. Engine Arrangements Showing Order of Firing 40
18. Two-Cycle Engine 48
19. Carburetor Principles 54
20. Automatic Carburetors 59
21. Mechanically Controlled Carburetor 63
22. Float-Feed Carburetor with Gravity Gasoline Feed 65
23. Pressure-Feed Gasoline System 67
23A. Types of Float Valves 69
23B. Types of Auxiliary Air Inlets 71
24. Battery Connections 85
25. Make-and-Break Ignition 92
26. Types of Timers 99
27. Mechanical Vibrator 104
28. Magnetic Vibrator 104
29. Spark Plug and Spark Plug in Section 107
30. Ignition Circuit 108
31. Friction Cone Clutches 115
32. Multiple-Disk Clutch 117
33. Sliding Gear—Progressive Type 122
34. Selective Type 127
35. Planetary Type 133
36. Individual Clutch and Friction Drive 139
37. Propeller and Single-Chain Drives 143
38. Typical Universal Joint 144
38A. Types of Shaft Drives 145
39. Live Axle—Non-floating Type 147
40. Live Axle—Floating Type 147
40A. Dead Axle with Driving Shaft 149
41. Torsion Rod 150
42. Double Side-Chain Drive 151
43. Differentials 154
44. Two Arrangements of the Drag Link 162
45. Steering Principles 163
46. Steering Mechanisms 165
47. Three Varieties of Brakes 168
48. Springs 175
49. Distance or Radius Rods 177
50. Jump-Spark Wiring Diagrams 237
51. Jump-Spark Wiring Diagrams 239
52. Make-and-Break Wiring Diagram 241
53. Make-and-Break Wiring Diagram 241
ILLUSTRATIONS IN APPENDIX
1. Magnetic Lines of Force 250
2. Armature 256
3. The Armature and Lines of Force 256
4. The Armature and Lines of Force 257
5. The Armature and Lines of Force 257
6. The Armature and Lines of Force 258
7. The Armature and Lines of Force 259
8. Make-and-Break System 271
9. Eisemann Ignition System 285
10. Wiring Diagram, H.-T. Magneto Interchangeable with
Secondary Coil 298
11. Wiring Diagram, Two-Spark Magneto 302
12. Timing Diagram, Two-Spark Magneto 304
13. Diagrams showing Position of Shield Revolving about Armature 309
14. Wiring Diagram, Four-Spark Magneto 312
15. Timing Diagram, Four-Spark Magneto 314
16. Bosch Jump-Spark Dual System 318
17. Remy Inductor 321
18. Inductor Giving Six Waves 321
19. Magnetic Igniter 324
20. Wiring Diagram of Magnetic Igniter System 324
MOTOR-CAR PRINCIPLES
CHAPTER I
GASOLINE ENGINE PRINCIPLES
The action of a steam, gasoline, or hot-air engine depends on the
principle that when air or other gas is heated it expands, and that
if it is confined in a space that will not permit it to expand,
in striving to do so it creates pressure against all parts of the
chamber in which it is contained. The more a gas is heated, the more
it will expand if it is free to do so, and if not free, the greater
will be the pressure that it will exert in striving to expand.
Pressure may thus be generated by heat, and following along similar
lines, heat may be produced by pressure, for when the pressure of
a gas is increased by compressing it, or forcing it to occupy a
smaller space, the gas will become heated. The reverse is also true,
that when a gas is cooled, its volume is reduced, which reduces
the pressure that it exerts; similarly, reducing the pressure by
permitting the gas to expand reduces its temperature.
To state these principles in another form, to create pressure in a
gas it must either be heated or compressed into a smaller space,
and to reduce its pressure it must either be cooled or permitted to
expand.
The action of a locomotive, the most familiar type of steam engine,
is no mystery, and the production of steam in the boiler, its passage
to the cylinder, and the application of its steady pressure against
first one side of the piston and then the other, resulting in the
turning of the driving wheels, are well understood. Water being
converted into steam in the boiler, pressure is created because of
the tendency of the steam to expand, but the only place in which it
may expand is the cylinder, where in so doing it moves the piston.
[Illustration: FIG. 1.—ENGINE ACTIONS.]
A gasoline engine is similar to a steam engine in that its piston is
moved by the pressure exerted by a heated and expanding gas; it is
different in that the pressure is produced inside of the cylinder
by the combustion of an inflammable mixture of gasoline vapor,
instead of being generated in a boiler away from the cylinder. The
heat of the combustion creates great pressure, and as the piston is
the only part that can give before it, it is moved from one end of
the cylinder to the other, this motion being utilized in the turning
of the crank shaft. The combustion, which is so rapid that the
generally accepted term for it is explosion, can occur only after the
mixture has been drawn into the cylinder, and so prepared that it
ignites quickly and burns completely, with the object of obtaining
the greatest possible heat from it in the shortest possible time. In
order that one explosion may be followed by another, the burned and
useless products of combustion must be expelled to make place for a
fresh charge of the inflammable mixture.
These successive events, forming a =cycle=, must be performed as
long as the engine runs, and the constantly changing pressure in the
cylinder due to the movement of the piston allows a fresh charge to
enter, prepares it, and expels the products of combustion after the
pressure that they have exerted has been utilized.
While in the great majority of steam engines the steam acts first
on one side of the piston and then on the other, in an automobile
gasoline engine the pressure is exerted on only one side, the
combustion of the mixture taking place between the piston and the
closed end, or =head=, of the cylinder. The other end of the cylinder
is open, and the piston slides between the ends, its movement from
one end to the other, called a =stroke=, corresponding to a half
revolution of the crank shaft.
Gasoline engines are divided into two classes, according to the
number of strokes of the piston that are necessary to accomplish the
cycle; in the most usual type, four strokes are necessary, the class
being called the four-stroke-cycle, or =four-cycle=, in distinction
to the two-stroke-cycle, or =two-cycle=, in which but two strokes are
necessary.
Of the five events that compose the cycle, three (the =inlet=, during
which the fresh mixture enters the cylinder, its =compression= or
preparation, and the =exhaust= of the burned gases) are performed
by the piston; during the =power= event the piston is moved by the
pressure resulting from the combustion, while the =combustion= event
is due to an outside source. In the four-cycle type of engine,
which is in almost universal use for automobiles, the events are
considered with reference to the movement made by the piston
during which they are performed, and may be called the =inlet=,
=compression-combustion=, =power=, and =exhaust strokes=. In order
that the engine may continue to run, it is obvious that the events
must be performed in the correct order, and that the failure of one
will affect all the others.
During the inlet stroke, a charge of fresh mixture enters the
cylinder as the piston makes an outward stroke from the closed
toward the open end. When the piston makes the following inward
stroke, the mixture is compressed and combustion occurs, the pressure
from which drives the piston outward on the power stroke. This is
followed by another inward stroke, which pushes the burned gases
out of the cylinder. It will be seen that power is developed during
only one stroke of the four, the other three being required in
the preparation for the following power stroke. The movement of the
piston over these three dead strokes is secured by attaching to the
crank shaft a heavy =fly wheel=, the momentum of which, acquired
during the power stroke, keeps the crank shaft revolving and the
piston in motion while the events are performed.
[Illustration: _SUCTION STROKE_ _COMPRESSION STROKE_
_POWER STROKE_ _EXHAUST STROKE_ FIG. 2.—GASOLINE ENGINE CYCLE.]
The space between the piston and cylinder head in which the
combustion occurs is called the =combustion space=, and the =inlet=
and =exhaust valves= open into it, the first being that by which the
fresh mixture enters, and the second that by which the products of
combustion escape. The device for igniting the mixture projects into
the combustion space, and the means of ignition in universal use for
automobile engines is an electric spark.
INLET STROKE
During the stroke (Fig. 2), the piston is moved outward by the crank
shaft, which is revolved either by hand or by the momentum of the
fly wheel. This movement increases the size of the combustion space,
thereby reducing the pressure in it, and the higher pressure of the
atmosphere outside of the cylinder will force fresh mixture into the
combustion space, the inlet valve being open to admit it. If the
piston moves slowly, the mixture will be able to enter fast enough to
keep the pressure in the combustion space equal to that outside, but
at the high speed at which a gasoline engine is run the piston will
reach the end of its stroke before a complete charge has had time to
enter, so that the pressure in the combustion space will still be
below that of the atmosphere. If the inlet valve closed at this point
so that no more mixture could enter, the combustion of the partial
charge would result in a lower pressure than would be possible with
a full charge; the inlet valve should therefore remain open until
the piston reaches the point of its next inward stroke at which the
pressure in the cylinder equals that outside.
COMPRESSION-COMBUSTION STROKE
The compression and the combustion of the charge occur during the
next inward stroke of the piston.
The period between the bringing together of the liquid gasoline and
air and its admission to the cylinder is too brief to secure perfect
combination, and the mixture that results is not satisfactory. A
portion of the air will not have been able to come into contact with
the gasoline, and much of the liquid will not have been vaporized;
what passes into the cylinder consists of pure air, liquid gasoline,
and a more or less perfect mixture of the two. The combustion of this
would be slow and incomplete, resulting in loss of power and waste of
fuel. In order to render the mixture more perfect, advantage is taken
of the heat that is produced by compression; the inward stroke of
the piston raises the temperature of the mixture by compressing it,
the heat rendering the gasoline more volatile, and the compression
forcing it into combination with the air. Even this does not result
in the formation of a perfect mixture, for the period is too short to
effect it. The failure of an engine to deliver full power may often
be traced to this condition, for the air and gasoline vapor, instead
of being thoroughly combined and mixed, will be in layers, so to
speak, and the combustion will be slow and uneven. Future development
of the internal combustion engine will no doubt eradicate this, to
the increase of efficiency and economy.
The charge of inflammable mixture can produce a certain amount of
heat, and the more rapidly and completely this heat is obtained, the
greater and more sudden will be the rise in pressure. The pressure
will be greater when the mixture is contained in a small space than
when in a large, and as the combustion space is smallest when the
piston is at its inmost point, the greatest pressure will be obtained
if combustion is complete at this point. If the combustion of the
mixture were instantaneous, it should be ignited at this point; but
even though very rapid, it nevertheless burns slowly enough to make
it necessary to ignite it sufficiently before the end of the stroke
to have the combustion complete as the piston comes into position
to move outward. The instant at which the mixture must be ignited
in order to produce this result depends on the speed of the piston,
for the interval between the ignition of a good mixture and its
complete combustion does not vary to any great extent. When the
piston is moving slowly, the mixture may be ignited toward the end
of the compression stroke, for there will be sufficient time for
complete combustion by the time the stroke is ended; but when moving
at high speed, ignition must occur much earlier in the stroke, as
otherwise the piston will have completed the compression stroke and
begun to move outward on the power stroke before the mixture is
entirely burned. The instant at which ignition occurs also depends
on the mixture that is used, for its quality and proper combination
make a difference in the rapidity with which it burns. The better the
quality of the mixture, the faster and more completely it will burn,
and ignition may occur later in the stroke than would be possible
with a mixture of poor quality. As the mixture is ignited by the
passing of an electric spark in the combustion space, the difference
in the instant at which it occurs may be secured by permitting the
spark to pass earlier or later, and this is under the control of the
driver.
When ignition occurs early in the compression stroke, the spark is
said to be =advanced=, in distinction to a =retarded= spark, which
passes when the compression stroke is more nearly complete.
If the spark is advanced too much, combustion will be complete before
the piston has reached the end of the compression stroke, and it
will be necessary to force it to the end of the stroke against the
pressure by the momentum of the fly wheel, in order that it may get
into position to move outward on the power stroke. In such a case,
the momentum may not be sufficient to overcome the pressure, and
the piston will be brought to a stop. A retarded spark results in
the combustion of the mixture being completed after the piston has
begun to move outward on the power stroke, and the pressure will
then be reduced because it is exerted in a larger space, the piston
consequently being moved with less force; if the spark is still
further retarded, the combustion will not be complete by the time the
exhaust begins, and the heat from only a portion of the mixture will
be utilized, because it will still be burning as it is forced out of
the cylinder.
The position at which the spark occurs is one of the means by which
the speed of the engine is controlled, for the low pressure that
results from a retarded spark moves the piston at low speed, while
the greater pressure from an advanced spark drives the piston outward
with more force and higher velocity.
While high compression of the charge improves its quality, and
results in combustion being more rapid and complete, it has limits,
and if carried too far the heat generated by the compression will be
sufficient to ignite the mixture. This would have a bad effect on
the operation of the engine, for the pressure would then be produced
at the wrong point of the stroke, retarding instead of assisting the
revolution of the crank shaft. Modern practice has shown that in
engines that are maintained at a proper temperature the best results
are obtained by compressing the mixture to from sixty to eighty
pounds to the square inch; there are instances in which a higher
compression is obtained, but the liability to ignite the mixture
prematurely makes it undesirable.
POWER STROKE
The increasing size of the combustion chamber as the piston moves
outward on the power stroke permits the gases to expand, and in doing
so the temperature will fall, the pressure decreasing in consequence.
A further decrease in pressure is caused by the hot gases being in
contact with the metal cylinder and piston, which absorb heat. The
more slowly the engine runs, the longer the gases will be in contact
with the cylinder walls, and the more opportunity there will be for
loss of heat from this cause; at higher speeds, there will be less
time for heat to be absorbed by the cylinder walls, and more will be
utilized in expanding the gases and producing work.
Even at the outmost position of the piston, the combustion space
will not be large enough to permit the gases to expand until their
pressure has dropped to that of the atmosphere, so that they will
still be exerting pressure. By opening the exhaust valve, the gases
will have an outlet for expansion, and will begin to rush out. While
the pressure might be utilized against the piston to the end of the
power stroke, it has been found that better results are obtained by
opening the exhaust valve before the piston reaches the end of the
power stroke. There is then a higher pressure forcing the gases out
than there would be later in the stroke, and the greater quantity
of gases that escapes leaves less to be expelled during the exhaust
stroke.
EXHAUST STROKE
The inward movement of the piston pushes out of the open exhaust
valve the gases that have not escaped through their desire to expand.
The exhaust valve remains open for the entire stroke, but when the
engine is running at high speed the piston moves so rapidly that
the gases cannot escape fast enough to prevent their being slightly
compressed. When the piston is at its inmost point, the gases are
still flowing through the valve because of this slight compression,
and if the valve closed, a portion would be retained. The best
results come from the closing of the exhaust valve not at the end
of the exhaust stroke, but a short time after the piston has begun
to move outward again, during which period the compression forces
the gases out. The exhaust valve closes at the point when the slight
compression has been reduced to the pressure of the atmosphere by the
escape of the gases and the enlargement of the combustion space.
If the piston completely filled the combustion space when at its
inmost point, all of the burned gases would be expelled, but the
necessity for leaving a space in which combustion may take place
renders this impossible, and a small portion of the burned gases
therefore remains in the cylinder. The space between the cylinder
head and the piston when at its inmost point, called the =clearance=,
should be as small as possible, in order that the amount of these
gases remaining in the cylinder may not be sufficient to contaminate
the fresh charge and weaken the pressure of its combustion.
The passages through which the burned gases are led away from the
cylinder must be large and free from obstructions, for if a free
flow is not permitted back pressure will be set up, which will
prevent the largest possible amount of gases from escaping, and leave
a greater portion to contaminate the fresh charge.
The power that a gasoline engine is capable of developing depends
on the size of the cylinder, the pressure acting on the piston, and
the speed at which it operates. A steam engine, which obtains its
pressure from a boiler, can do work as soon as the steam is turned
into the cylinder, but a gasoline engine must be running before it
can be called on to deliver power. Because of the cycle of events on
which its operation depends, the piston must be forced to perform the
inlet and compression strokes before pressure can be developed, and
it is necessary to revolve the crank shaft by outside means until a
charge of mixture has been taken into the cylinder, compressed, and
ignited, when the engine begins to work by the pressure from the
combustion, and takes up its cycle. Not until this has been done can
it be called on to do work.
A steam engine can be made to deliver more power than it is built
for by increasing the pressure acting against its piston, and the
full pressure of the boiler can be utilized when extra work is
necessary. The power developed by a gasoline engine being greatly
dependent on its speed, and there being no reserve by which greater
power can be developed in emergencies, it is necessary for an engine
of this type to be perfectly adapted to the work that is desired of
it. At excessive speeds the piston acquires great momentum, which
must be overcome at each end of a stroke by the crank shaft, and
while a speed above normal may be attained, it results in the quick
destruction of the bearings and the severe straining of the engine.
The best results in efficiency and long life accompany the running of
the engine at the slowest speed possible for the development of the
required power.