|Back||1 2 3 4 5||Next|
EDISON had no sooner designed his dynamo in 1879 than he adopted the same form of machine for use as a motor. The two are shown in the Scientific American of October 18, 1879, and are alike, except that the dynamo is vertical and the motor lies in a horizontal position, the article remarking: "Its construction differs but slightly from the electric generator." This was but an evidence of his early appreciation of the importance of electricity as a motive power; but it will probably surprise many people to know that he was the inventor of an electric motor before he perfected his incandescent lamp. His interest in the subject went back to his connection with General Lefferts in the days of the evolution of the stock ticker. While Edison was carrying on his shop at Newark, New Jersey, there was considerable excitement in electrical circles over the Payne motor, in regard to the alleged performance of which Governor Cornell of New York and other wealthy capitalists were quite enthusiastic. Payne had a shop in Newark, and in one small room was the motor, weighing perhaps six hundred pounds. It was of circular form, incased in iron, with the ends of several small magnets sticking through the floor. A pulley and belt, con- nected to a circular saw larger than the motor, permitted large logs of oak timber to be sawed with ease with the use of two small cells of battery. Edison's friend, General Lefferts, had become excited and was determined to invest a large sum of money in the motor company, but knowing Edison's intimate familiarity with all electrical subjects he was wise enough to ask his young expert to go and see the motor with him. At an appointed hour Edison went to the office of the motor company and found there the venerable Professor Morse, Governor Cornell, General Lefferts, and many others who had been invited to witness a performance of the motor. They all proceeded to the room where the motor was at work. Payne put a wire in the binding-post of the battery, the motor started, and an assistant began sawing a heavy oak log. It worked beautifully, and so great was the power developed, apparently, from the small battery, that Morse exclaimed: "I am thankful that I have lived to see this day." But Edison kept a close watch on the motor. The results were so foreign to his experience that he knew there was a trick in it. He soon discovered it. While holding his hand on the frame of the motor he noticed a tremble coincident with the exhaust of an engine across the alleyway, and he then knew that the power came from the engine by a belt under the floor, shifted on and off by a magnet, the other magnets being a blind. He whispered to the General to put his hand on the frame of the motor, watch the exhaust, and note the coincident tremor. The General did so, and in about fifteen seconds he said: "Well, Edison, I must go now. This thing is a fraud." And thus he saved his money, although others not so shrewdly advised were easily persuaded to invest by such a demonstration.
A few years later, in 1878, Edison went to Wyoming with a group of astronomers, to test his tasimeter during an eclipse of the sun, and saw the land white to harvest. He noticed the long hauls to market or elevator that the farmers had to make with their loads of grain at great expense, and conceived the idea that as ordinary steam-railroad service was too costly, light electric railways might be constructed that could be operated automatically over simple tracks, the propelling motors being controlled at various points. Cheap to build and cheap to maintain, such roads would be a great boon to the newer farming regions of the West, where the highways were still of the crudest character, and where transportation was the gravest difficulty with which the settlers had to contend. The plan seems to have haunted him, and he had no sooner worked out a generator and motor that owing to their low internal resistance could be operated efficiently, than he turned his hand to the practical trial of such a railroad, applicable to both the haulage of freight and the transportation of passengers. Early in 1880, when the tremendous rush of work involved in the invention of the incandescent lamp intermitted a little, he began the construction of a stretch of track close to the Menlo Park laboratory, and at the same time built an electric locomotive to operate over it.
This is a fitting stage at which to review briefly what had been done in electric traction up to that date. There was absolutely no art, but there had been a number of sporadic and very interesting experiments made. The honor of the first attempt of any kind appears to rest with this country and with Thomas Davenport, a self-trained blacksmith, of Brandon, Vermont, who made a small model of a circular electric railway and cars in 1834, and exhibited it the following year in Springfield, Boston, and other cities. Of course he depended upon batteries for current, but the fundamental idea was embodied of using the track for the circuit, one rail being positive and the other negative, and the motor being placed across or between them in multiple arc to receive the current. Such are also practically the methods of to-day. The little model was in good preservation up to the year 1900, when, being shipped to the Paris Exposition, it was lost, the steamer that carried it foundering in mid-ocean. The very broad patent taken out by this simple mechanic, so far ahead of his times, was the first one issued in America for an electric motor. Davenport was also the first man to apply electric power to the printing-press, in 1840. In his traction work he had a close second in Robert Davidson, of Aberdeen, Scotland, who in 1839 operated both a lathe and a small locomotive with the motor he had invented. His was the credit of first actually carrying passengers--two at a time, over a rough plank road--while it is said that his was the first motor to be tried on real tracks, those of the Edinburgh-Glasgow road, making a speed of four miles an hour.
The curse of this work and of all that succeeded it for a score of years was the necessity of depending upon chemical batteries for current, the machine usually being self-contained and hauling the batteries along with itself, as in the case of the famous Page experiments in April, 1851, when a speed of nineteen miles an hour was attained on the line of the Washington & Baltimore road. To this unfruitful period belonged, however, the crude idea of taking the current from a stationary source of power by means of an overhead contact, which has found its practical evolution in the modern ubiquitous trolley; although the patent for this, based on his caveat of 1879, was granted several years later than that to Stephen D. Field, for the combination of an electric motor operated by means of a current from a stationary dynamo or source of electricity conducted through the rails. As a matter of fact, in 1856 and again in 1875, George F. Green, a jobbing machinist, of Kalamazoo, Michigan, built small cars and tracks to which current was fed from a distant battery, enough energy being utilized to haul one hundred pounds of freight or one passenger up and down a "road" two hundred feet long. All the work prior to the development of the dynamo as a source of current was sporadic and spasmodic, and cannot be said to have left any trace on the art, though it offered many suggestions as to operative methods.
|Back||1 2 3 4 5||Next|
Edison, His Life and Inventions -by- F. L. Dyer and T. C. MartinBottom Content goes here. Wikipedia content requires these links..... Wikipedia content is licensed under the GNU Free Documentation License.