Great Engineers & Scientists

Editor's Note: This is the second in a two-part series about Frank Julian Sprague, a Connecticut-born inventor known as the "father of electric traction". Sprague's electric railways transformed urban transportation, and his electric elevators enabled skyscrapers to rise above the urban landscape.

Part 1 of this series ran last week.

The Sprague motor was the first in a series of technological breakthroughs. After building the first electric motor to maintain constant RPMs under different loads, Frank J. Sprague learned how to return power to the main supply for electric motor-driven equipment. Thomas Edison's former associate then designed a system of compound field-magnet windings that kept commutator brushes in a fixed, non-sparking position. The development of a three-point, wheelbarrow-style suspension for axle-mounted gear motors completed this round of accomplishments, enabling Sprague to start work on his next major project.

The Richmond Union Passenger Railway

In 1887, the Sprague Electric Railway & Motor Company began work on the Richmond Union Passenger Railway, the world's first large-scale electric trolley system. Prior to this project, there had been 74 attempts – the best only marginally successful – to build smaller systems across North America and Europe. In February 1888, Frank J. Sprague confounded his critics by completing an electric railway that was safe, convenient and reliable. Within two years, Sprague could boast that 110 electric railways with his equipment were either built or under contract. His closest competitor, the Thomson-Houston Company, soon modified its design to incorporate Sprague's methods of electric traction. General Electric and Westinghouse also built products that were based on Frank J. Sprague's designs.

Horizontal Transportation Turns Vertical

In 1890, Edison's General Electric Company purchased the Sprague Electric Railway & Motor Company. Two years later, Frank Sprague parted company with Thomas Edison again, this time to form the Sprague Electric Elevator Company. According to researcher Evelyn Jutte, Sprague believed he could apply lessons learned from electric railways to "vertical transportation". Although electric elevators were not new, existing models were not powerful enough to reach the tops of skyscrapers. Sprague believed his electric traction technologies could achieve higher speeds and longer runs, and developed the multiplying sheaves and operator controls to prove it.

When the Postal Telegraph Company offered to buy six elevators for its New York headquarters, Frank J. Sprague had to agree to install hydraulic units if his electric ones failed. The backup plan proved unnecessary, however, when Sprague ran four of his elevators at 325 feet per minute with 2500-pound loads, and the other two at 400 feet per minute with 1800-pound loads. Subsequent inventions included floor control, acceleration control, and automatic elevators. Sprague also connected individual control circuits to a master control switch, permitting the non-synchronous operation multiple elevators at the same time. Finally, after building 584 elevators for some of the largest buildings in North America and Europe, Sprague sold his business to the Otis Elevator Company.

Improving Electric Traction

Over the next several decades, Frank J. Sprague continued to develop electric railways and electric elevators. In 1895, he designed a multiple-unit system for running large-scale electric railways. He also served on the Commission for Terminal Electrification of the New York Central Railroad, and designed automatic controls which forced electric trains to obey trackside signals. During the second half of the 1920s, Frank J. Sprague returned to vertical transportation, inventing a way to run two independent elevators – one local, the other express – in a single shaft to conserve floor space. A floating lower limit for the upper car and a floating upper limit for lower car permitted not just joint actuation and control, but also safe operation. Like many of his previous inventions, Sprague eventually sold his dual-elevator to another company, this time Westinghouse.

"A Prodigious Capacity for Work"

During the course of his long career, Frank J. Sprague earned a gold medal at the Paris Electrical Exhibition, the grand prize at the St. Louis Exhibition, and the Edison Medal from the American Institute of Electrical Engineers. In addition, the Franklin Institute bestowed both its Elliot-Cresson Medal and Franklin Metal. Three days before he died on October 25, 1934, Frank J. Sprague learned that he had been selected to receive the John Fritz Gold Medal for 1935. As his son Robert C. Sprague later wrote, "All through his life and up to his last day, Frank Sprague had a prodigious capacity for work.

Resources:

http://www.ieee.org/web/aboutus/history_center/richmond.html

http://en.wikipedia.org/wiki/Frank_J._Sprague

http://www.bera.org/articles/sprague.html

http://www.theelevatormuseum.org/e/e-1.htm

http://www.arlingtoncemetery.net/fjsprague.htm

http://americanhistory.si.edu/archives/d8069e.htm