Transcriber's Note
Italic text is denoted by _underscores_ and bold text by =equal signs=.
Whole numbers with fractional parts are denoted as 7-3/4.
_Every Boy's
Mechanical
Library_
[Illustration]
MOTORS
Every Boy's Mechanical Library
By J. S. ZERBE, M.E.
Price, per volume, 60 cents, Net. Postage extra.
AUTOMOBILES
This is a subject in which every boy is interested. While few mechanics
have the opportunity to actually build an automobile, it is the
knowledge which he must acquire about every particular device used, that
enables him to repair and put such machines in order. The aim of this
book is to make the boy acquainted with each element, so that he may
understand why it is made in that special way, and what the advantages
and disadvantages are of the different types. To that end each structure
is shown in detail as much as possible, and the parts separated so as to
give a clear insight of the different functions, all of which are
explained by original drawings specially prepared to aid the reader.
MOTORS
To the boy who wants to know the theory and the practical working of the
different kinds of motors, told in language which he can understand, and
illustrated with clear and explicit drawings, this volume will be
appreciated. It sets forth the groundwork on which power is based, and
includes steam generators, and engines, as well as wind and water
motors, and thoroughly describes the Internal Combustion Engine. It has
special chapters on Carbureters, Ignition, and Electrical systems used,
and particularly points out the parts and fittings required with all
devices needed in enginery. It explains the value of compounding,
condensing, pre-heating and expansion, together with the methods used to
calculate and transmit power. Numerous original illustrations.
AEROPLANES
This work is not intended to set forth the exploits of aviators nor to
give a history of the Art. It is a book of instructions intended to
point out the theories of flying, as given by the pioneers, the
practical application of power to the various flying structures; how
they are built; the different methods of controlling them; the
advantages and disadvantages of the types now in use; and suggestions as
to the directions in which improvements are required. It distinctly
points out wherein mechanical flight differs from bird flight, and what
are the relations of shape, form, size and weight. It treats of kites,
gliders and model aeroplanes, and has an interesting chapter on the
aeroplane and its uses in the great war. All the illustrations have been
specially prepared for the work.
CUPPLES & LEON CO., Publishers, NEW YORK
[Illustration]
_Every Boy's Mechanical Library_
MOTORS
BY
J. S. ZERBE, M.E.
_Author of Aeroplanes--Automobiles_
_ILLUSTRATED_
NEW YORK
CUPPLES & LEON COMPANY
Copyright, 1915, by
CUPPLES & LEON COMPANY
CONTENTS
PAGE
Introductory 1
The Subject. The Inquisitive Trait. The Reasons for Doing
Things. The Mystery of Mechanism. Curiosity which prompts
Investigation. The Sum of Knowledge.
Chapter I. Motors and Motive Power 5-21
The Water Fall. Water moves in One Direction only. What is
Energy. Stored or Potential Energy. Kinetic Energy.
Friction. Resistance. Inertia. The Law of Bodies. Internal
and External Resistance. Momentum. Energy Indestructible.
Wind Power. Rectilinear Motion. Oscillating Motion.
Movements in Nature. How Man Utilizes the Various Movements.
Kinds of Potential Energy. The Power in Heat. Energy in
Steam. Energy from the Sun. Power from Water. The Turbine.
Calculating Power of a Turbine. Horse Power. Foot Pounds.
Power and Time. Gravitation. Utilizing the pull of Gravity.
Taking Advantages of Forces. Pitting Forces Against each
Other. Centripetal and Centrifugal Forces. Power not Created.
Developing the Power of Motors. Experimenting.
Chapter II. The Steam Generator 22-31
Water as an absorbent of Heat. Classification of Boilers.
Mode of applying Heat. The Cylindrical Boiler. The Cornish
Boiler. The Water Tube Boiler. Various Boiler Types. Compound
Steam Boiler. Locomotive Steam Boiler. Vertical Steam Boiler.
Chapter III. Steam Engines 32-59
The Original Turbine Engine. The Reciprocating Engine.
Atmospheric Engine. The Piston. Importance of the Valve.
Expanding the Steam. Balanced Valve. Rotary Valve. Engine
Accessories. Efficiency of Engines. How Steam acts in a
Cylinder. Indicating the Engine. Mean Efficiency.
Calculating Horse Power. Condensation. Atmospheric Pressure.
The Condenser. Pre-heating. Superheaters. Compounding. Triple
and Quadruple Expansion Engines. The Steam Turbine. Pressure
and Velocity. Form of Blades. Compounding the Jet.
Chapter IV. Fuels and Combustion 60-67
Solid Fuels. Liquid Fuels. Combustion. Oxidation. The
Hydro-Carbon Gases. Oxygen and the Atmosphere. Internal
Combustion. Vaporizing Fuel. Explosion by Heat Compression.
How Compression Heats. Elasticity of Gases. Advantages of
Compression. The Necessity of Compression.
Chapter V. The Internal Combustion Engine 68-82
Fixed Gases. Gas Engines. Energy of Carbon and Hydrogen.
The Two-Cycle Type. Advantages of the Two-Cycle Engine. The
Four-Cycle Engine. The Four Cycles. Ignition Point. Advantages
of the Four-Cycle Type. The Loss in Power. Engine
Construction. Valve Grinding. The Crank Shaft. The Cams.
Chapter VI. Carbureters 83-101
Functions of a Carbureter. Rich Mixtures. Lean Mixtures.
Types of Carbureters. The Sprayer. The Surface Type.
Governing a Carbureter. Primary Air. Needle Valve. Secondary
Air. Requirements in a Carbureter. Size of a Carbureter. Rule
for Size of Carbureters. The Throttle. Flooding.
Adjustability. Surface Carbureters. Float Chamber.
Chapter VII. Ignition, Low Tension System 102-120
Electricity. Magnetism. The Armature. Characteristics of
Electricity. Make and Break System. Voltage. High and Low
Voltage. Low Tension method. Disadvantages of Make and Break.
Amperes. Resistance. Direct Current. Alternating Current.
Induction. Generating Electricity. Primary Battery. Making a
Dry Cell. Energy in a cell. Wiring Methods. Series Connection.
Multiple Connection. Series Multiple. Watts. Testing a Cell.
Testing with Instruments. Simple Battery Make and Brake
System. To Advance the Spark. The Magneto in the Circuit.
Magneto Spark Plug.
Chapter VIII. Ignition, High Tension 121-140
Magnetos. Alternating Current. Cutting Lines of Force.
Plurality of Loops. The Electro Magnet. The Dynamo Form. The
Magneto Form. Advantages of the Magneto. Induction Coil.
Changing the Current. Construction of a Coil. Primary Coil.
Secondary Coil. Contact Maker. High Tension with Battery and
Coil. Metallic Core for Induction Coil. The Condenser.
Operations of a Vibrator Coil. The Distributor. Circuiting
with Distributor.
Chapter IX. Mechanical Devices Utilized in Power 141-157
The Unit of Time. Horse Power. Proney Brake. Reversing
Mechanism. Double Eccentric Reversing Gear. Balanced Slide
Valve. Balanced Throttle Valve. Engine Governors. Injectors.
Feed Water Heaters.
Chapter X. Valves and Valve Fittings 158-171
Check Valve. Gate Valve. Globe Valve. The Corliss Valve.
Corliss Valve-operating Mechanism. Angle Valve. Rotary Valves.
Rotable Engine Valves. Throttle Valves. Blow-off Valves.
Pop-Safety Valves.
Chapter XI. Cams and Eccentrics 172-178
Simple Cams. Wiper Wheels. Cylindrical Cam Motion. Eccentrics.
Triangularly-formed Eccentrics.
Chapter XII. Gears and Gearing 179-190
Racks and Pinions. Mangle Rack. Controlling the Pinion. Dead
Center. Crank Motion Substitute. Mangle Wheels. Quick Return
Motion. Accelerated Motion. Quick-return Gearing. Scroll
Gearing.
Chapter XIII. Special Types of Engines 191-201
Temperatures. Artificial Heat. Zero. Liquids and Gases.
Refrigeration. Rotary Engines. Caloric Engines. Adhesion
Engines.
Chapter XIV. Enginery in the Development of the Human Race 202-207
Power in Transportation. Power vs. Education and the Arts.
Lack of Power in the Ancient World. The Early Days of the
Republic. Lack of Cohesiveness in Countries Without Power.
The Railroad as a Factor in Civilization. The Wonderful
Effects of Power. England as a User of Power. The Automobile.
High Character of Motor Study. The Unlimited Field of Power.
Chapter XV. The Energy of the Sun, and How Heat is Measured 208-216
Fuel Economy. Direct Conversion. The Measurement of Heat.
Caloric. Material Theory. Heat Transmitted in Three Ways.
Conduction. Convection. Radiation.
Glossary 217
LIST OF ILLUSTRATIONS
FIG. PAGE
1. Undershot Wheel 13
2. Overshot Wheel 14
3. Primitive Boiler 24
4. Return Tubular Boiler 25
5. Cornish, or Scotch Boiler 25
6. Water Tube Boiler. End view 27
7. Water Tube Boiler. Side view 29
8. The Original Engine 33
9. Horizontal Section of Tube 33
10. Steam-Atmospheric Engine 35
11. Simple Valve Motion. First position 38
12. Simple Valve Motion. Second position 38
13. Effective pressure in a Cylinder 42
14. Indicating pressure line 44
15. Indicating the Engine 45
16. Compound Engine 53
16a. Relative Piston Pressures 54
17. Changing Pressure into Velocity 55
18. Reaction against Air 56
19. Reaction against Surface 56
20. Turbine. Straight Blades 57
21. Curved Blades 58
22. Compound Turbine 58
23. Two-Cycle Engine. First position 71
24. Two-Cycle Engine. Second position 73
25. Two-Cycle Engine. Third position 73
26. Four-Cycle Engine. First position 75
27. Four-Cycle Engine. Second position 75
28. Four-Cycle Engine. Third position 76
29. Four-Cycle Engine. Fourth position 76
30. Valve Grinding 81
31. Carbureter 87
32. Carbureter 95
33. Surface Carbureter 98
34. Dry Cell 108
35. Series Connection 109
36. Multiple, or Parallel Connection 110
37. Series-Multiple Connection 111
38. Circuit Testing 113
39. Make and Break, with Battery 114
40. Make and Break, with Magneto 117
41. Magneto Spark Plug 119
42. Illustrating Alternating Current 122
43. Alternating Current. Second position 122
44. Alternating Current. Third position 123
45. Alternating Current. Fourth position 124
46. Making the Circuit 125
47. The Dynamo 126
48. The Magneto 126
49. Current by Induction 128
50. Induction Coil 129
51. Typical Induction Coil 130
52. Contact Maker 131
53. Typical Circuiting, Jump spark Ignition 132
54. Metallic Core, Induction Coil 133
55. Condenser 134
56. Vibrator Coil and Connections 135
57. The Distributer 137
58. Circuiting with Distributer 138
59. Illustrating the Unit of Time 142
60. The Proney Brake 143
61. Double Eccentric Reversing Gear 146
62. Reversing Gear, Neutral 146
63. Reversing Gear, Reversed 147
64. Single Eccentric Reversing Gear 147
65. Balanced Slide Valve 148
66. Valve Chest. Double Port Exhaust 149
67. Balanced Throttle-Valve 150
68. Watt's Governor 151
69. The Original Injector 152
70. Injector with movable Combining Tube 154
71. Feed Water Heater 156
72. Check Valve 158
73. Gate Valve 159
74. Globe Valve 160
75. Corliss Valve 162
76. Corliss Valve-operating Mechanism 163
77. Angle Valve 164
78. Rotary-Valve 165
79. Two-way Rotary 165
80. Rotary Type 166
81. Two-Way Rotary Type 166
82. Butterfly Throttle 167
83. Angle Throttle 167
84. Slide Throttle 168
85. Two-slide Throttle 168
86. Blow-off Valve 169
87. Safety Pop Valve 170
88. Heart Shaped 173
89. Elliptic 173
90. Double Elliptic 173
91. Single Wiper 174
92. Double Wiper 174
93. Tilting Cam 174
94. Cam Sector 175
95. Grooved Cam 175
96. Reciprocating Motion 175
97. Pivoted Follower for Cam 176
98. Eccentric 177
99. Eccentric Cam 177
100. Triangularly-formed Eccentric 178
101. Rack and Pinion 180
102. Rack Motion 180
103. Plain Mangle Rack 181
104. Mangle Rack Motion 181
105. Alternate Circular Motion 181
106. Controlling Pinion for Mangle Rack 182
107. Illustrating Crank-pin Movement 183
108. The Dead Center 184
109. Crank Motion Substitute 184
110. Mangle Wheel 185
111. Quick Return Motion 186
112. Accelerated Circular Motion 187
113. Quick Return Gearing 188
114. Scroll Gearing 189
115. Simple Rotary Engine 196
116. Double-feed Rotary Engine 198
117. Adhesion Motor 200
INTRODUCTORY
The motor is the great dominating factor in the world of industry. Every
wheel and spindle; every shaft and loom, and every piece of mechanism
which has motion, derives it from some sort of motor.
The term _motor_ has a wider significance than any other word. A steam
engine is a motor, and so, also, is a dynamo, a water wheel or a wind
mill.
It would be just as descriptive to call a wind mill a wind _motor_, or a
steam engine a steam _motor_, as to adhere to the old terms; and, on the
other hand, since it would be out of place to call a dynamo or a wind
mill an engine, the word _motor_ seems best adapted to express the
meaning of every type of mechanism which transforms energy into motion.
In considering the subject I shall proceed on the theory that the boy
knows nothing whatsoever of the subject, nor the terms used to designate
the various phases, subjects and elements. It must be elementary in its
character, and wholly devoid of technical terms or sentences.
While it is necessary to give information in a book of this character,
on the methods for figuring out power, it must be done without resorting
to the formulas usually employed in engineering works, as they are of
such a nature that the boy must have some knowledge of the higher
mathematics to follow out the calculations employed.
Indeed, every phase should be brought within the mental view of the boy,
and to do this may occasionally necessitate what might appear to be long
drawn out explanations, all of which, it is hoped, will be the means of
more clearly presenting the subject.
The opening chapters, which treat of the fundamentals, will be as nearly
complete as possible, and thus lay a foundation for the work we shall be
called upon to perform, when we treat of the structures of the different
parts and devices in the various types of motors.
The object is to explain power in its various phases, how derived, and
the manner in which advantage is taken of the elements, and substances
with which we are brought into contact. The reasons for each step are
plainly set forth with the view of teaching the boy what power means,
rather than to instruct him how to make some particular part of the
machinery.
_The Inquisitive Trait._--My experience has impressed me with the
universality of one trait in boys, namely, that of inquisitiveness. Put
a machine before a boy and allow him to dissect it, and his curiosity
will prompt him to question the motive for the particular construction
of each part of its make-up.
_The Reasons for Doing Things._--He is interested in knowing the reason
why. Every boy has the spirit of the true investigator,--that quality
which seeks to go behind or delve down deeply. This is a natural
instinct.
_The Mystery of Mechanism._--If this taste is gratified, and he thereby
learns the mystery of the machine, what a wonderful world is opened to
him! The value of the lesson will depend, in a large measure, on the
things which he has found out for himself. It is that which counts,
because he never forgets that which he has dug out and discovered.
_Curiosity Which Prompts Investigation._--I recall a farmer's boy whose
curiosity led him to investigate the binding mechanism of a reaper. It
was a marvel to him, as it has been to many others. He studied it day
after day, and finally, unaided mastered the art. That was something
which could not be taken away from him.
It was a pleasure to hear him explain its operation to a group of boys,
and men, too, in which he used the knot itself to explain how the
various fingers and levers coöperated to perform their functions. It was
an open book to him, but there was not one in the group of listeners who
could repeat the explanation.
_The Sum of Knowledge._--It is the self-taught boy who becomes the
expert. The great inventors did not depend on explanations. A book of
this character has a field of usefulness if it merely sets forth, as far
as possible, the sum of useful knowledge which has been gained by
others, so as to enable the boy to go forward from that point, and thus
gain immensely in time.
There is so much that has been developed in the past, with reference to
the properties of matter, or concerning the utility of movements, and
facts in the realm of weights, measures, and values of elements which he
must deal with, that, as he studies the mechanical problems, the book
becomes a sort of cyclopedia, more than a work designed to guide him in
the building of special engines or motors.
The Author.
MOTORS
CHAPTER I
MOTORS AND MOTIVE POWER
What makes the wheels turn round? This simple question is asked over and
over again. To reply means pages of answers and volumes of explanations.
The Water Fall.--Go with me to the little stream I have in mind, and
stand on the crest of the hill where we can see the water pouring down
over the falls, and watch it whirling away over the rocks below.
The world was very, very old, before man thought of using the water of
the falls, or the rushing stream below, to grind his corn or to render
him other service.
Water Moves in One Direction Only.--What the original man saw was a body
of water moving in one direction only. When he wanted to grind corn he
put it in the hollow of a rock, and then beat it with a stone, which he
raised by hand at each stroke. In doing so two motions were required in
opposite directions, and it took thousands of years for him to learn
that the water rushing along in one direction, could be made to move the
stone, or the pestle of his primitive grinding mill, in two directions.
It took him thousands of years more to learn another thing, namely, that
the water could be made to turn the stone round, or rotate it, and thus
cause one stone, when turning on another, to crush and grind the grain
between them.
Now, as we go along with the unfolding of the great question of
_motors_, we must learn something of the terms which are employed, to
designate the different things we shall deal with, and we ought to have
some understanding of the sources of power.
What Is Energy?--The running, as well as the falling water represent
energy. This is something which is in the thing, the element, or the
substance itself. It does not come from without. It is not imparted to
it by anything.
Stored or Potential Energy.--At the top of the falls, look at that
immense rock. It has been there for centuries. It, also, has energy.
There is stored within it a tremendous power. You smile! Yes, the power
has been there for ages, and now by a slight push it is sent crashing
down the precipice. The power developed by that fall was thousands of
times greater than the push which dislodged it.
But, you say, the push against the stone represented an external force,
and such being the case, why do you say that power is within the thing
itself? The answer is, that not one iota of the power required to push
the stone off its seat was added to the power of the stone when it fell.
Furthermore, the power required to dislodge the stone came from within
me, and not from any outside source.
Here we have two different forms of energy, but both represent a moving
force. The power derived from them is the same.
Kinetic Energy.--The energy of the falling water or stone is called
_Kinetic_ energy. In both cases the power developed came from within
themselves and not from any exterior source.
The difference between Potential and Kinetic Energy is therefore that
Potential Energy represents the capacity to do work, while Kinetic
Energy is the actual performance of work.
Friction.--In every form of energy there is always something to detract
from it or take away a portion of its full force, called _friction_.
When a shaft turns, it rubs against the bearings, and more or less power
is absorbed.
When a wheel travels over the ground friction is ever present. The
dislodging of the stone required ten pounds of energy, but a thousand
pounds was developed by the fall. The water rushing along its rocky bed
has friction all along its path.
Resistance.--This friction is a resistance to the movement of a body,
and is ever present. It is necessary to go back and examine the reason
for this. As long as the stone was poised at the top of the precipice it
had latent or potential energy, which might be termed _power at rest_.
When it fell it had power in motion. In both cases gravity acted upon
the stone, and in like manner on the water pouring over the falls.
Inertia.--Inertia or momentum is inherent in all things and represents
the resistance of any body or matter, to change its condition of rest or
standing still into motion, and is then called _Inertia of Rest_, or the
resistance it offers to increase or decrease its speed when moving, and
is then called _Inertia of Motion_.
Inertia or momentum is composed by the weight of the body and its speed
and is measured by multiplying its weight by its speed.
The law is, that when a body is at rest it will remain at rest
eternally, and when in motion it will continue in motion forever, unless
acted on by some external force or resistance. An object lying on the
ground has the frictional resistance of the earth to prevent its moving.
When the object is flying through space it meets the air and has also
the downward pull of gravity, which seek to bring it to rest.
These resisting forces are less in water, and still less in gases, and
there is, therefore, a state of mobility in them which is not found in
solids.
Internal and External Resistance.--All bodies are subject to internal,
as well as external resistance. The stone on the cliff resisted the
movement to push it over. Weight was the resisting internal force, but
when the stone was moving through the air, the friction with the air
created external resistance.
Energy Indestructible.--There is another thing which should be
understood, and that is the absolute indestructibility of energy. Matter
may be changed in form, or in the direction of its motion, by the change
of kinetic into potential energy, or vice versa, but the sum total of
the energy in the world is unalterable or constant.
The tremendous power developed by the stone when it plunged through
space and struck the rocks below, developed a heat at its impact. Thus
the moving force which was a motion in one direction was converted into
another form of energy, heat. The expansion of the material exposed to
the heat also represented energy.
When powder explodes and absolutely changes the form of the substance,
its volume of expansion, if it should be retained within a vessel, would
perform a certain amount of work, and the energy is thus transferred
from one form to another without ceasing.
Wind Power.--Primitive man also saw and felt the winds. He noted its
tremendous power, but he could not see how a force moving in one
direction only could be utilized by him.
Rectilinear Motion.--This movement of the wind in one direction, like
the water flowing along the bed of the river, is called _rectilinear_
motion. It required invention to convert rectilinear into circular
motion.
Oscillating Motion.--When he threshed his grain and winnowed it by
shaking it to and fro, to rid it of the chaff, the idea of using the
wind to produce an oscillating motion did not occur to him. After
circular motion was produced, the crank was formed and thus the
oscillating movement was brought about.
Movements in Nature.--All movements in nature are simple ones, of which
the following are illustrations:
1. _Rectilinear_, which, as stated, means in a straight line.
2. _Circular_, like the motion of the earth on its axis, once every
twenty-four hours.
3. _Oscillatory_, like a to and fro movement, the swaying branches of
trees, or the swinging of a pendulum.
How Man Utilizes the Various Movements.--What man has done is to utilize
the great natural forces in nature in such a way as to produce these
movements at will, in either direction, with greater or less speed, at
regular or irregular intervals, and at such amplitudes as are required
to perform the necessary work.
Kinds of Potential Energy.--Now, materials have within themselves
_potential_ energy of various kinds. Thus, powder, if ignited, will
burn, and in burning will expand, or explode, as we term it. This is
true also of oils and gases. The expansion pressure produced from such
substances depends on the speed at which they will burn, and in so
confining the burning substances that a great pressure is produced.
The Power in Heat.--The pressure of all such substances against the
confining medium depends on heat. Any gas which has 523 degrees of heat
imparted to it will expand double its volume. If one cubic inch of
water is converted into steam the latter will occupy one cubic foot of
space under atmospheric pressure,--that is, it will expand over 1700
times.
Energy in Steam.--If the steam thus generated is now subjected to 523
degrees of heat additional, it will occupy over 3400 cubic inches of
space. It will thus be seen why steam, gas, and gasoline engines are
called _heat engines_, or heat _motors_.
Energy From the Sun.--Many attempts have been made to utilize the heat
of the sun, to turn machinery, but the difficulty has been to secure
sufficient heat, on the one hand, and on the other to properly cool down
the heated gases, so that the various liquid and solid fuels are
required to make the heat transformations.
Power From Water.--In the use of water two forms are available, one
where the water is moving along or falling in a constant open stream;
and the other where the flowing water is confined and where its flow can
be regulated and controlled. The latter is more available for two
reasons:
First: Economy in the use of water.
Second: Ability to control the speed or movement of the motor.
With running or falling streams a large surface is required, and the
wheels turn slowly. Two well-recognized forms of wheels have been
employed, one called the undershot, or breast wheel, shown in Fig. 1,
and the other the overshot, illustrated in Fig. 2.
[Illustration: _Fig. 1. Undershot Wheel._]
In both types it is difficult to so arrange them as to shut off the
power or water pressure when required, or to regulate the speed.
The Turbine.--Wheels which depend on the controllable pressure of the
water are of the turbine type. The word is derived from the Latin word
_turbo_, meaning to whirl, like a top. This is a type of wheel mounted
on the lower end of a vertical or horizontal shaft, within, or at the
bottom, of a penstock. The perimeter of the wheel has blades, and the
whole is enclosed within a drum, so that water from the penstock will
rush through the tangentially-formed conduit into the drum, and strike
the blades of the wheel.
[Illustration: _Fig. 2. Overshot Wheel._]
A column of water one inch square and twenty-eight inches high weighs
one pound,--or, to express it in another way, the pressure at the
bottom of such a column is one pound, and it is a pound for each
additional 28 inches.
If there should be a head or height of water column of seven feet, the
pressure on each square inch of water at the bottom of the penstock
would be three pounds to the square inch. Assuming the opening or duct
leading to the wheel blades should be 12 × 12 inches, and also the
blades be 12 × 12 inches, the area would be equal to 144 square inches,
and this multiplied by three pounds would equal 432 pounds pressure
against the blades.
Calculating Power of a Turbine Wheel.--The power of such a wheel depends
principally on two things. First, the arrangement of the blades with
reference to the inflowing water; and, second, the discharge port, or
ability of the water to free itself from the wheel casing.
Let us assume that the diameter of the wheel at the center of the blades
is two feet, which would, roughly estimating, give a circumference of
six feet, or a travel of each particular blade that distance at each
turn of the wheel.
If the wheel turns one hundred times a minute, and this is multiplied by
the circumference of the wheel (six feet), the result is 600 feet. This,
again, multiplied by 432 pounds (which represents the pressure of the
water on the entire discharge opening), and we have a product of
259,200, which represents _foot pounds_.
This means the same work as if 259,200 pounds would have been lifted
through a space of one foot in one minute of time. To ascertain how much
power has been developed we must know how many foot pounds there are in
a horse power.
Horse Power.--It is determined in this way: any force which is capable
of raising 550 pounds one foot in one second of time, is developing one
horse power. A man might have sufficient strength to raise such a weight
once, twice, or a dozen times in succession, but if he should try to do
it sixty times a minute he would find it a trying, if not impossible
task.
Foot Pounds.--If he should be able to lift 550 pounds sixty times within
a minute, he would have lifted 33,000 pounds one foot in one minute of
time (550 × 60), and thus have developed one horse power.
As the water wheel, in our calculations above, raised 259,200 pounds in
that period of time, this figure divided by 33,000 shows that a little
more than 7-3/4 horse power was developed, assuming, of course, that we
have not taken into account any waste, or loss by friction, or
otherwise.
This method of determining one horse power should be carefully studied.
Always keep in mind the main factor, 33,000 pounds, and this multiplied
by one foot, the result will be 33,000 _foot pounds_,--that is, one
horse power.
It would be just the same, however, if it were possible to raise one
pound 550 times in one second, or one pound 33,000 times within a
minute.
Power and Time.--You are thus brought face to face with another thing
which is just as important, namely, that, in considering power, time, as
well as energy, must be considered. If a man, by superior strength,
could be able to raise 550 pounds once within a second, then skip a few
seconds, take another hold, and again raise it that distance, he would
not be developing one horse power for a minute, but only for one second
while he lifted the weight. For the whole minute he would only develop a
certain number of foot pounds, and less than 33,000 foot pounds.
If, within a minute, he succeeded in raising it one foot for six times,
this would be six times 550, equal to 3,300 foot pounds, or just
one-tenth of one horse power for one minute; so _time_ is just as
important as the amount lifted at each effort.
Gravitation.--Now, let us examine power from another standpoint. Every
attempt which man makes to produce motion is an effort to overcome some
resistance. In many cases this is "weight or gravity." While humanity
unceasingly antagonizes the force of gravity it is constantly utilizing
the laws of gravitation.
Utilizing the Pull of Gravity.--The boy laboriously drags his sled to
the top of the hill against gravity, and then depends on that force to
carry him down. We have learned to set up one force in nature against
the other. The running stream; the moving winds; the tides; the
expansive force of all materials under heat, are brought into play to
counteract the great prevailing agency which seeks to hold everything
down to mother earth.
Utilizing Forces.--The Bible says: Blessed is he who maketh two blades
of grass grow where one grew before. To do that means the utilization of
forces. Improved machinery is enabling man to make many blades grow
where one grew before. New methods to force the plow through the soil;
to dig it deeper; to fertilize it; and to harvest it; all require power.
Pitting Forces Against Each Other.--Man has discovered how to pit the
forces of nature against each other, and the laws which regulate them.
Centripetal and Centrifugal Forces.--Gravity, that action which seeks to
draw all matter toward the center of the earth, is termed _centripetal_
force. But as the earth rotates on its axis another force is exerted
which tends to throw substances outwardly, like dirt flying from the rim
of a wheel. This is called _centrifugal_ force.
Man utilizes this force in many ways, one of which is illustrated in the
engine governor, where the revolving balls raise the arms on which they
swing, and by that means the engine valve is regulated.
Power Not Created.--In taking up the study of this subject start with a
correct understanding of the source of all power. It is inherent in all
things. All we can do is to liberate it, or to put the various materials
in such condition, that they will exert their forces for our uses. (See
Page nine, "Energy Indestructible.")
A ton of coal, when burned, produces a certain amount of heat, which, if
allowed to escape, will not turn a wheel. But if confined, it expands
the air, or it may convert water into steam which will turn ponderous
machinery. Niagara Falls has sent its great volume into the chasm for
untold centuries, but it has never been utilized until within the last
twenty years. The energy has been there, nevertheless; and so it is with
every substance of which we have knowledge.
The successive steps, wherein the experimenter and the inventor have
greatly improved on the original inventions, will be detailed as we go
along through the different types of motors.
Developing the Power of Motors.--This development in the art is a most
fascinating study. It is like the explorer, forcing his way through a
primeval forest. He knows not what is beyond. Often, like the traveler,
he has met serious obstructions, and has had to deviate from his course,
only to learn that he took the wrong direction and had to retrace his
steps.
The study of motors and motive power is one which calls for the highest
engineering qualities. In this, as in every other of the mechanical
arts, theory, while it has an important function, occupies second place.
Experimenting.--The great improvements have been made by building and
testing; the advance has been step by step. Sometimes a most important
invention will loom up as a striking example to show how a valuable
feature lies hidden and undeveloped.
An illustration of this may be cited with respect to the valve of the
steam engine. For four hundred years there was no striking improvement
in the valve. The various types of sliding and rocking valves were
modified and refined until it was assumed that they typified perfection.
At one stroke the Corliss valve made such an immense improvement that
the marvel was as much in its simplicity as in its performance.
The reasons and the explanations will be set forth in the section which
analyzes valve motion. In this, as in other matters, it shall be our aim
to explain why the different improvements were regarded as epochs in the
production of motors.