Mechanics: The Science of Machinery. A. Russell Bond
frame. But a wheel is something that is distinctly a human creation. Whoever invented it must have been a real genius, a James Watt or a Thomas Edison of his day. Certainly we owe more to the invention of the wheel than we do even to so revolutionary a machine as the steam engine, or the flying machine. How it was ever first conceived is a mystery. Maybe this primeval genius got his idea from seeing a stone rolling downhill, or he may have seen a tumbling weed rolling along the ground before the wind. It may be that the forerunner of the wheel was a roller shaped out of a log, for certainly primitive civilization must have advanced enough to have known how to hew timber before it would have been capable of fashioning a wheel. Some observant man might have noticed that he could drag a heavy timber over a rolling log much more easily than he could along the bare ground, and gradually the roller evolved into a wheel.
We can speculate upon the evolution of vehicles and transportation, once the wheel was invented. Of course, the first method of transporting loads was to carry them in the arms. Possibly loads were placed on skids and dragged along by one end. Away back in early times, it was discovered that two persons could carry more than twice as much as one, if the load were placed on a couple of poles. There was no friction to contend with, and not only was the load cut in two, because each man bore half of it, but the position of the load was such that it could be borne more easily. After the wheel was discovered, some one must have conceived of the idea of dispensing with an assistant by placing a wheel between the poles of the stretcher, thus making a crude wheelbarrow. It is more likely that two wheels were first used, making a cart of the stretcher, because the crude workmen of those days could hardly have produced anything but a very wobbly wheelbarrow. At any rate, the wheel, or pair of wheels, robbed one man of his job. Only one bearer was required where before two had been used. Labor costs were immediately reduced 50 per cent.
DISPLACING MEN WITH MACHINES
In the very earliest days of invention machines began to displace men. Had there been unions in those days, no doubt there would have been strenuous opposition to the introduction of this substitute for an honest worker. But among the ancients, even more than at the present time, invention meant greater production rather than less work, because the laborer of that time was not a hired man but a slave. There was no object in cutting down labor when it cost practically nothing. The only stimulus to invention was greater production.
The invention of the wheel meant the dawn of transportation, which is the backbone of civilization, and from it resulted no end of other inventions. It made it possible for communities to come into closer touch with each other. It meant circulation—an interchange of knowledge and of products. Food was transported from one locality to another, enabling certain communities to dispense with agricultural work and specialize in certain lines of manufacture; for they could barter their products for food raised by other communities. There are some tribes to-day which are most backward because they are separated from other tribes by rivers, while other tribes similarly placed owe their progress to the fact that they have developed sufficient skill to build crude bridges and thus gain access to the outside world.
RAISING WATER
In Egypt the wheel had a wonderful effect on agriculture. In that dry land water is, and always has been, most precious. No wonder the Nile was venerated! It meant life—life to crops, and hence life to man. How to raise water from this stream of life in time of drought was the great problem of the Egyptian. As slave labor was cheap, it was customary to haul up the precious water, a bucket at a time, and pour it over the fields. Then some one discovered that this process could be simplified by using a shadoof or swape; in other words, a long pole fulcrumed near one end, with a heavy rock for a counterbalance lashed to the shorter arm, and a bucket tied by a long rope to the longer arm of the lever. This primitive machine is still to be found in some rural districts. With this contrivance, a heavier load could be lifted than by hand, because, when raising the bucket, the weight of the rock would assist in lifting the water. After the swape came all manner of ingenious devices for lifting the water. There were seesaw arrangements which would scoop up some of the water at each oscillation of the seesaw, and in one ingenious contrivance there was a succession of seesaws by which the water was raised to a considerable height, whence it poured down into ditches that irrigated the fields.
Then some one invented a water wheel or a great wheel, fitted with buckets, which was turned by human or ox power, and which poured a steady stream of water into the irrigating ditches.
But the greatest invention was that of the engineer who actually made the river turn the wheel. It was probably on the Nile that the noria, as this machine was called, was first put into service.
The wheel was provided with paddles, so that the current made it revolve, and the water spilled out of the buckets into a trough as they were turned over by the wheel. We can imagine the triumph of the ancient inventor who developed that machine. True, the river might arise in its wrath now and then and wreck the machine, but in wrecking the wheel it had to flood the land, which, after all, was exactly what was aimed at. The anger of the river was short-lived; it soon quieted down and went on placidly turning the wheel which robbed it of the precious water. It was a great event in the history of engineering. The Nile had been harnessed. One of the great powers of nature had been set to work.
CHAPTER II
THE ANATOMY OF A MACHINE
EVERY animal is a complex machine, provided with its own motive power and a brain for directing the operation of its own mechanical elements. Not satisfied with the mechanism that nature has put into the human machine, man has reached for other elements and devised mechanisms of his own in order to supplement the human machine and increase its efficiency. At first, as we have seen, these elements were hand tools of the crudest sort; but they were gradually improved and then they were combined into what we term machines. In developing these machines, he naturally took his own system as a pattern and was guided to a large extent by an examination of his own physical structure. We see this very clearly in the names of the different parts of machinery, which are taken from the names of similar parts in the human frame. Almost every member of the body is used in mechanical terminology. For instance, we have the “head” and the “foot,” the “arms” and the “legs,” the “fingers” and the “ankles,” “elbows,” “shoulders,” “trunk,” “hips,” and various parts of the face, such as the “eyes,” “ears,” “nose,” “mouth,” “teeth,” “lips,” and even the “gums,” to indicate parts of machinery which have some remote resemblance to these features.
Before we can understand machinery we must have some general knowledge of the elements of which it is composed. Probably most of the readers of this book already possess a fair knowledge of machine elements and mechanical movements and they can well afford to skip this chapter. However, for the benefit of the uninitiated, we must put a machine on the operating table, dissect it, and explain its anatomical structure. We cannot attempt a very detailed study, but will confine ourselves to the most important elements.
Every machine is made up of movable parts and fixed parts, the latter serving to guide or constrain the motion of the former; for no combination of elements will constitute a machine unless the parts are constrained to move in certain predetermined directions.
THE LEVER
Among the moving elements the first to be considered is the lever, which really forms a broad classification comprising many elements that will hardly