Mechanics: The Science of Machinery. A. Russell Bond
Liberty engines began to be manufactured on a stupendous scale.
CUTTING WITH RED-HOT TOOLS
One of the most remarkable advances in machine tools was due to the studies of Fred W. Taylor. He entered a large steel plant in 1880 and was immediately struck with the enormous waste of effort on the part of the men in the plant. There was at that time considerable dissatisfaction among the workmen, and when Taylor endeavored to speed up work he was faced by the incontrovertible argument that he had no idea how much work a certain machine ought to turn out. There was nothing for him to do but either back down or study machine tools and discover their maximum capacity. This led him to investigate the matter of cutting speeds. For years he spent all of his spare time studying this subject, timing machines and experimenting with different types of cutting tools. He estimated that in the twenty-six years of his investigation he converted 800,000 pounds of steel into chips. What he wished to discover was the best depth of cut, the best speed of cutting, and the best speed at which the tool should be fed into the work. He soon discovered that, contrary to prevailing opinion, the round-nosed tool was better than the diamond-pointed tool, that the coarse slow-cutting speed was better than a fine cut at high speed. He discovered that the best method of lubricating the tools was to keep them bathed in a heavy stream of water, supersaturated with carbonate of soda, so as to prevent the metal from rusting. The best tool steel of that day was known as a self-hardening steel. Manufacturers of the cutting steels had warned Taylor that he must not use water on these tools. Taylor, however, was not satisfied to take the word of others, but proceeded to investigate the matter himself, and discovered that he could safely increase the cutting speed of his tools 33 per cent by the use of a heavy stream of water for lubricating purposes. This led Taylor and his associate, Maunsel White, to investigate the different kinds of tool steels, and eventually they evolved a chrome tungsten tool which could do from two to four times the work of other tools. Later vanadium was added to the alloy, further improving the tool.
At the Exposition in Paris, in 1900, foreign manufacturers were astonished to find enormous lathes operating at high speed with the cutting tools taking such heavy cuts and feeding so fast that the nose of the tool was actually heated to a dull red heat, and yet it kept its cutting edge perfectly. This was a revelation to tool makers abroad, and it led immediately to the adoption of American high-speed cutting tools.
The development of the automobile, which began to take on serious proportions at about that time, is responsible above all other machines for improvements in American machine tools, and for the extension of the American system of interchangeable manufacture. When automobiles came to be made on the interchangeable system and in enormous quantities so that the cost was reduced to within the limits of the average man’s pocketbook, they began to make mechanics of men who before that had never used a tool; and this new and widespread interest in machinery stimulated the production of better and more efficient tools. Hence the progress of machine tools in the past few years has been simply phenomenal.
CHAPTER IV
COUNTING SECONDS
YOU CAN measure civilization by its timepieces. The higher the civilization of a community the more it appreciates the value of time and the more minutely does it measure the passage of time. The savage divides his day into but two periods: the period of light and that of darkness; the early Romans divided their day into eight watches, four watches of daylight and four of night, but the higher and more complex civilization became, the smaller became the subdivisions of time. People began to feel the need of carrying the time with them, and about 1500 A. D. watches came into use, but it was not until 1665 that watches began to be equipped with minute hands, and it was almost exactly a century later that they were equipped with a second hand. To-day time means so much to us that we will fight our way into a subway express, instead of riding more comfortably in a local train, merely for the sake of saving five minutes. The tiny second hands of our watches divide the day into eighty-six thousand four hundred parts, and in some operations we measure time intervals down to the thousandth part of a second. Only among the most highly civilized nations are timepieces carried by the common people.
It used to be that time was made for slaves, but now time has made slaves of us. Shift the hands of the clock and the whole nation is forced to change its habits.
Time-measuring mechanism is given early prominence in this book because clocks were among the earliest machines invented, and they furnish an example of the wonderful ingenuity of inventors before the dawn of the modern era of machinery. Naturally this chapter must be largely historical.
The first thought of measuring time came from the ancient astronomers and astrologers, who, in watching the motions of heavenly bodies, the sun by day and the moon by day and night, found it necessary to keep a record of these motions and sought about for some mechanical means of doing so. The studies of the old astrologers were closely associated with religion, and as a consequence the most advanced intellects were centered upon astronomical matters and incidentally upon horology. Fortunately the design and construction of mechanisms for measuring time were not considered beneath the dignity of the scientists of those early days. Mathematicians felt free to record their investigations in this branch of mechanics, and as a consequence of the early cooperation of science and mechanics in this field much real progress was made, and the development of timepieces was more rapid than that of any other machine.
TELLING TIME WITH A LEAKY BUCKET
The ancient Egyptians early felt the need of a better clock than the sundial, because it operated only on cloudless days and was absolutely worthless to tell off the hours of darkness. Realizing that time is a measure of motion, they sought for some slowly moving body whose motion could be used to measure time, and naturally they turned to water. The earliest form of clock consisted merely of a leaking bucket. Either the bucket was filled with water which was allowed to escape through a very tiny orifice, or else the heavily loaded bucket was placed in water and the water was allowed to leak into the bucket until it sank. The period it took for a bucket to run dry or for a bucket to fill and sink indicated a lapse of an hour or some other standard of time.
The idea of subdividing this period was a later development. As the water leaked out of a bucket, the water level descended, but unfortunately not at a uniform rate. The weight of water in a full bucket made the drops come faster than when the bucket was nearly empty. Consequently the time graduations on the side of the bucket had to be set farther apart at the top of the bucket than at the bottom. Various ingenious schemes were devised for maintaining a uniform discharge. In one type of water clock or clepsydra a conical bucket was used so that there would be a constant relation between the head of water and the volume in the bucket and the time graduations could be spaced uniformly.
THE REMARKABLE WATER CLOCK OF CTESIBIUS
The most remarkable clepsydræ were those invented by an old Alexandrian mathematician, Ctesibius, who lived about 250 years before Christ. Ctesibius introduced the siphon principle into his clocks, and also employed gear wheels and even a cord and pulley. Furthermore, he was the first man to employ jeweled bearings in a timepiece. The use of jewels in timepieces was reinvented in 1704 A. D. However, Ctesibius used his jewels in a very different way from that in which they are used now, as will be described below.
FIG. 25.—THE JEWELED WATER CLOCK BUILT BY CTESIBIUS ABOUT 250 B.