Frank J. Sprague Inventions Information

Frank Julian Sprague (July 25, 1857 in Milford, Connecticut – October 25, 1934) was an American naval officer and inventor who contributed to the development of the electric motor, electric railways, and electric elevators. His contributions were especially important in promoting urban development by increasing the size cities could reasonably attain (through better transportation) and by allowing greater concentration of business in commercial sections (through use of electric elevators in skyscrapers). He became known as the "Father of Electric Traction".

Sprague was born in Milford, Connecticut in 1857 to David Cummings Sprague and Frances Julia King Sprague, a school teacher:79 His mother died when he was ten, and was sent by his father to live with an aunt in New York. He attended Drury High School in North Adams, Massachusetts and excelled in mathematics. After graduating high school, Sprague went to Springfield, Massachusetts to take an entrance exam for West Point, but somehow unexpectedly was taking the four day entrance exam for the United States Naval Academy in Annapolis, Maryland. He got the highest score (twelve others took the exam), and to go to the school he needed to borrow money. A local contractor and a bank loaned him four thousand dollars, and he travelled to Maryland.[page needed] There, he graduated seventh (out of thirty-six) in the class of 1878.

He was commissioned as an ensign in the United States Navy. During his ensuing naval service, he first served on the USS Richmond, then the USS Minnesota. While in Asia, Sprague wrote stories he filed for the Boston Herald.[page needed] While his ship was in Newport, Rhode Island, in 1881, Sprague invented the inverted type of dynamo. After he was transferred to the USS Lancaster, flagship of the European Squadron, he installed the first electric call-bell system on a United States Navy ship. Sprague took leave to attend the International Exposition of Electricity of 1881 in Paris and the Crystal Palace Exhibition in Sydenham, England in 1882, where he was on the jury of awards for gas engines, dynamos and lamps.

In 1883, Edward H. Johnson, a business associate of Thomas Edison, persuaded Sprague to resign his naval commission to work for Edison.:81 Sprague, who begun at a salary of $2,500, was neither happy with his salary nor his assignments. Sprague wanted to focus on motors, while motors bored Edison he was consumed to make his incandescent lighting work. Edison sent Sprague to run the construction departments where Edison had built central stations for the lighting system. Sprague was sent to Sunbury, Pennsylvania and Brockton, Massachusetts.:85

One of Sprague's significant contributions to the Edison Laboratory at Menlo Park, New Jersey, was the introduction of mathematical methods. Prior to his arrival, Edison conducted many costly trial-and-error experiments. Sprague's approach was to calculate using mathematics the optimum parameters and thus save much needless tinkering. He did important work for Edison, including correcting Edison's system of mains and feeders for central station distribution.

In 1884, he decided his interests in the exploitation of electricity lay elsewhere, and he left Edison to found the Sprague Electric Railway and Motor Company.

By 1886, Sprague's company had introduced two important inventions: a constant-speed, non-sparking motor with fixed brushes, and regenerative braking, a method of braking that uses the drive motor to return power to the main supply system. His motor was the first to maintain constant speed under varying load. It was immediately popular, and was endorsed by Edison as the only practical electric motor available. His regenerative braking system was important in the development of the electric train and the electric elevator.

Sprague's inventions included several improvements to designs for systems of electric streetcars collecting electricity from overhead lines. He improved designs for a spring-loaded trolley pole that had been developed in 1885 by Charles Van Depoele, devised a greatly improved mounting for streetcar motors and better gear designs, and proved that regenerative braking was practical. After testing his trolley system in late 1887 and early 1888, Sprague installed the first successful large electric street railway system – the Richmond Union Passenger Railway in Richmond, Virginia, which began passenger operation on February 2, 1888. Long a transportation obstacle, the hills of Richmond included grades of over 10%, and were an excellent proving ground for acceptance of his new technology in other cities, in contrast to the cable cars which climbed the steepest grades of Nob Hill in San Francisco at the time.

By the summer of 1888, Henry M. Whitney of the West End Street Railway in Boston had witnessed the simultaneous startup of multiple streetcars on a single power source, and had signed up for conversion.:10 By January 1889, Boston had its first electric streetcars — which would be the first in the Americas to go underground some eight years later — and which had become so popular and noteworthy that poet Oliver Wendell Holmes composed a verse about the new trolley pole technology, and the sparking contact shoe at its apex::10

Within a year, electric power had started to replace more costly horsecars in many cities. By 1889 110 electric railways incorporating Sprague's equipment had been begun or planned on several continents. In 1890, Edison, who manufactured most of Sprague's equipment, bought him out, and Sprague turned his attention to electric elevators. However, he continued to be interested in the use of electricity for urban transportation and proposed a major expansion of London's Underground in 1901.

Sprague's system of electric supply was a great advantage in relation to the first bipolar U-tube overhead lines, in everyday use since 1883 on the Mödling and Hinterbrühl Tram.

While electrifying the streetcars of Richmond, the increased passenger capacity and speed gave Sprague the notion that similar results could be achieved in vertical transportation — electric elevators. He saw that increasing the capacity of elevator shafts would not only save passengers' time, but would also increase the earnings of tall buildings, with height limited by the total floor space taken up in the shaftways by slow hydraulic-powered elevators.

In 1892, Sprague founded the Sprague Electric Elevator Company. Working with Charles R. Pratt he developed the Sprague-Pratt Electric Elevator. The company developed floor control, automatic elevators, acceleration control of car safeties and a number of freight elevators. The Spague-Pratt elevator ran faster and with larger loads than hydraulic or steam elevators, and 584 elevators had been installed worldwide. Sprague then sold his company to the Otis Elevator Company in 1895.

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Sprague's experience with elevator control led him to devise a multiple unit system of electric railway operation, which accelerated the development of electric traction. In the multiple unit system, each car of the train carries electric traction motors. By means of relays energized by train-line wires, the engineer (or motorman) commands all of the traction motors in the train to act together. For lighter trains there is no need for locomotives, so every car in the train can generate revenue. Where locomotives are used, one person can control all of them.

Sprague's first multiple unit order was from the South Side Elevated Railroad (the first of several elevated railways locally known as the "L") in Chicago, Illinois. This success was quickly followed by substantial multiple-unit contracts in Brooklyn, New York and Boston, Massachusetts.

From 1896 to 1900 Sprague served on the Commission for Terminal Electrification of the New York Central Railroad, including the Grand Central Terminal in New York City, where he designed a system of automatic train control to ensure compliance with trackside signals. He founded the Sprague Safety Control and Signal Corporation to develop and build this system. Along with William J. Wilgus, he designed the Wilgus-Sprague bottom contact third rail system used by the railroads leading into Grand Central Terminal.

During World War I, Sprague served on the Naval Consulting Board. Then, in the 1920s, he devised a method for safely running two independent elevators, local and express, in a single shaft, to conserve floor space. He sold this system, along with systems for activating elevator car safety systems when acceleration or speed became too great, to the Westinghouse Company.

The effect of Sprague's developments in electric traction was to permit an expansion in the size of cities, while his development of the elevator permitted greater concentration in cities' commercial sections and increased the profitability of commercial buildings. Sprague's inventions over 100 years ago made possible modern light rail and rapid transit systems which still function on the same principles today.

The iconic Sprague-Thomson rolling stock of the Paris Métro, in service from 1908 to 1983, is still referred to as les rames Sprague (Sprague trainsets) today.

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