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Frank Julian Sprague (July 25, 1857 in Milford, Connecticutmarker - October 25, 1934) was an Americanmarker 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".

Childhood, education

Sprague was born in Milford, Connecticutmarker in 1857. He attended Drury High School in North Adams, Massachusettsmarker and excelled in mathematics. In 1874, he won an appointment to the United States Naval Academymarker in Annapolis, Marylandmarker. There, he graduated seventh (out of thirty-six) in the Class of 1878.

U.S. Navy, inventor

He was commissioned as an ensign in the U.S. Navy. During his ensuing naval service, he first served on the USS Richmond, then the USS Minnesota. While his ship was in Newport, Rhode Islandmarker, 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 U.S. Navy ship. Sprague took leave to attend the Paris Electrical Exhibition in 1881 and the Crystal Palacemarker Exhibition in Sydenhammarker, England in 1882, where he was on the jury of awards for gas engines, dynamos and lamps.

Joining the emerging electrical industry

In 1883, Edward H. Johnson, a business associate of Thomas Edison, persuaded Sprague to resign his naval commission to work for Edison. One of Sprague's significant contributions to the Edison Laboratory at Menlo Park, New Jerseymarker 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 & Motor Company.

By 1886, Sprague's company had introduced two important inventions: a constant-speed, non-sparking motor with fixed brushes, and a method to return power to the main supply systems of equipment driven by electric motors. 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 method of returning power to main supply systems was important in the development of the electric train and the electric elevator.

Richmond: inventing the trolley-pole

Sprague's inventions included a system on streetcars for collecting electricity from overhead wires. His spring-loaded trolley pole, invented in 1880, used a wheel to travel along the wire. In late 1887 and early 1888, using his trolley system, Sprague installed the first successful large electric street railway system, the Richmond Union Passenger Railway in Richmond, Virginiamarker. 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 Hillmarker in San Franciscomarker at the time.

Within a year, electric power had replaced 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.

Electric elevators

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 shaft ways 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 shaft ways by slow hydraulic-powered elevators.

In 1892, Sprague founded the Sprague Electric Elevator Company, and with Charles R. Pratt 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.

Multiple unit train controls

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 in locally known as the "L") in Chicago, Illinoismarker. This success was quickly followed by substantial multiple-unit contracts in Brooklyn, New Yorkmarker and Boston, Massachusettsmarker.

New York: Grand Central, elevators in skyscrapers

From 1896 to 1900 Sprague served on the Commission for Terminal Electrification of the New York Central Railroad, including the Grand Central Terminalmarker in New York Citymarker, where he designed a system of automatic train control to ensure compliance with trackside signals. He founded the Sprague Safety Control & 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.

Heritage, awards

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.

Sprague was awarded the gold medal at the Paris Electrical Exhibition in 1889, the grand prize at the St. Louis Exhibition in 1904, the Elliott Cresson Medal in 1904, the Edison Medal of the American Institute of Electrical Engineers, now IEEE, in 1910 'For meritorious achievement in electrical science, engineering and arts as exemplified in his contributions thereto', the Franklin Medal in 1921 and the John Fritz Gold Medal (posthumously) in 1935.

"All through his life and up to his last day, Frank Sprague had a prodigious capacity for work," his son Robert wrote in 1935. "And once having made up his mind on a new invention or a new line of work, he was tireless and always striving for improvement. He had a brilliantly alert mind and was impatient of any half-way compromise. His interest in his work never ceased; only a few hours before the end, he asked to have a newly designed model of his latest invention brought to his bedside."

Frank and Harriet Sprague had two sons, Robert and Julian. Robert founded the Sprague Electric Company which became a leading manufacturer of capacitors and other electronic components.

After Sprague died in 1934, his widow Harriet turned over a substantial amount of material from his collection to the New York Public Librarymarker, where it remains today accessible to the public via the rare books division. He was buried at Arlington National Cemeterymarker in Arlington, Virginiamarker, and she was interred beside him after her death in 1969.

In 1959, Harriet Sprague had donated funds for the Sprague Building at the Shore Line Trolley Museummarker at East Haven, Connecticutmarker, not far from Sprague's boyhood home in Milford. The museum is the oldest operating trolley museum in the United States, and has one of the largest collections of trolley artifacts in the United States.

In 1999, two of Frank and Harriet's grandsons, John L. Sprague and Peter Sprague, cut the ribbon and started an 1884 Sprague motor at a new exhibit at the Shore Line Trolley Museum. There, a permanent exhibit, "Frank J. Sprague: Inventor, Scientist, Engineer", helps tell the story of the part electricity played in the growth of cities as well as the role of the Father of Electric Traction. Entrepreneur Peter Sprague was Chairman of National Semiconductor from 1965 until 1995. John Sprague was President and Chief Executive Officer of Sprague Electric Company from 1981 to 1987.


Further reading

  • Frederick Dalzell. Engineering Invention: Frank J. Sprague and the U.S. Electrical Industry, 1880-1900. MIT Press, 2009. ISBN 978-0-262-04256-7
  • William D. Middleton and William D. Middleton III. Frank Julian Sprague: Electrical Inventor and Engineer. University of Indiana Press, 2009. ISBN 978-0-253-35383-2
  • Harold Clarence Passer. Frank Julian Sprague, father of electric traction, 1857-1934. Harvard University Press, 1952.
  • Harriet Chapman Jones Sprague. Frank J. Sprague and the Edison myth. New York, William-Frederick Press, 1947.
  • Brittain, J.E. "Frank J. Sprague and the electrification of urban transportation" in Proceedings of the IEEE, Vol. 85 (7), July 1997. pp. 1183 - 1184.

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