Motors Part 1
Motors.
by James Slough Zerbe.
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 cooperated 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 s.p.a.ce 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.