The Genius of Frank J. Sprague Still Resonates in the Modern World

What you’ll learn:

• Insight into Frank J Sprague’s lifetime of invention.
• How his electric motor and braking system revolutionized inner city transportation.
• Looking at his legacy in the modes of transportation we use today.

In today’s world, most of us take for granted the modern amenities we use daily in every major city around the world. Commuting to work on subways, trains, and elevated railways, or using elevators in high-rise homes and businesses, is nothing more than a passing thought for most of us as we try to navigate our busy lives.

Nearly a century and a half ago, cities looked much different than they do today, and that same technology we take for granted didn’t exist. That would all change with the vision and ingenuity of a single electrical engineer—Frank J. Sprague (Fig. 1). He had a hand in developing the electric motor, electric railways, and electric elevators.

Sprague’s contributions helped lay the cornerstone for promoting urban development by allowing for greater concentrations of businesses in commercial areas. No longer would cities be spread over great distances; they would instead go vertical via high-rises and skyscrapers.

Greater concentrations of commuters could also navigate the inner cities more efficiently. This was due to Sprague’s non-sparking motor with fixed brushes, regenerative braking, and an energy-recovering mechanism that slows down moving vehicles by converting the kinetic energy, which could be used immediately or stored for later usage.

Sprague’s Early Years… and Thomas Edison

As a young kid, Sprague had an affinity toward math and excelled in school. So much so that he was set to attend West Point but wound up attending the U.S. Naval Academy. In 1881, while in the Navy, Sprague invented the dynamo and installed the first electric call-bell system, which uses electric alarm bells, as well as the 1MC system to communicate with the crew during his stint on the USS Lancaster. By 1883, Sprague resigned his naval commission, persuaded by Edward H. Johnson, and went to work for Thomas Edison.

While working for Edison, Sprague developed a reliable DC commutator motor that could be used with industrial machinery. It provided increased torque and variable-speed control. A key aspect of machinery at the time often required variable performance under different loads.

He also helped with the installation of Edison’s innovative three-wire electrical light systems and improved his power-distribution system by correcting and improving the design of the mains and feeds in central stations. Doing so helped ensure that power was delivered reliably over long distances at the correct capacities.

One of Sprague’s more eclectic contributions to Edison’s inventive endeavor was introducing his engineers to the idea that mathematical formulas could be used for R&D instead of the standard trial-and-error method utilized in the engineering fields at the time. Sprague also developed formulas to calculate the optimal cable sizing for carrying different current loads, an innovation that helped save costs.

Working with Edison wasn’t exactly a match made in heaven. Sprague wasn’t interested in electric lighting. His attention focused on motors, which didn’t interest Edison at the time, so he sent Sprague to run the construction departments for his central power stations that supplied electricity to Edison’s lighting systems. While he helped Edison correct his system of mains and feeders for central station distribution, Sprague eventually left and founded the Sprague Electric Railway & Motor Company in 1884.

Non-Sparking Motor and Regenerative Braking

Sprague’s innovations continued at his company, introducing a pair of important inventions mentioned earlier: the constant-speed, non-sparking motor with fixed brushes (Fig. 2) and regenerative braking. His motor was the first to maintain a constant speed under varying loads, which was extremely popular and was hailed by Edison as the only practical electric motor available. The regenerative braking system was of incredible importance in the development of the electric train and electric elevator, which at the time were driven by hydraulic power.

Sprague’s regenerative-braking motor design was a game-changer in the early days of the electric motor. In essence, his motor could also act as an electric generator. When the streetcars needed to slow down, the system would switch the configuration of the motors, transitioning from using power to generating power.

The kinetic energy of the moving streetcars drove the motors, converting the energy into electric current, which subsequently could be fed back into the system and used to slow the streetcars down. Most of that energy could be reclaimed while braking instead of dissipating as heat.

Setting the Bar with Electric Streetcars

Sprague’s legacy was notable for his many inventions in electric power, but more so for his contributions to improving electric streetcars. He made some design improvements and upgrades to Charles Van Depoele’s spring-loaded trolley pole, devised improved mounting for streetcar motors and better gear designs, and made regenerative braking practical.

Sprague also developed a trolley system in late 1887 and installed the first successful large electric street railway system, the Richmond Union Passenger Railway in Richmond, Virginia. It began transporting passengers in 1888.

Before 1850, it was common to see horse-drawn carriages in the streets as the primary mode of transportation. Soon after, it was realized that by using rails, greater loads could be pulled more quickly. Railways soon became prevalent in most larger cities, laying down the infrastructure that would ultimately see cable cars rather than horse-drawn carriages, and with the advances in electrical power, electric motors soon drove those cable cars.

A great example of that notion is the creation of Chicago’s “L” (elevated) transit system, which was initiated in 1888. Early operations of the L began in 1892, with steam-powered trains transiting over a 3.6-mile route. Extensions were made during that time to accommodate passengers who would attend the World’s Columbian Exposition in 1893. Shortly after, ridership fell, leading to financial difficulties for the South Side Rapid Transit Railroad Company (SSRT) that owned the system at the time in 1895.

The SSRT assets would be later sold to a new company known as the South Side Elevated Railroad (SSE), allowing it to resume service, and by 1897, the company decided to transition from steam-powered engines to electric traction. To do so, the SSE hired engineering firm Sargent & Lundy to begin electrification of the “L,” and a new power generation station was built to handle the load.

The company sent out contracts to build the electrical equipment. However, most bidders proposed using locomotive motor cars to haul trailers to maintain compatibility with the city's other elevated rails as well as power the trains with 600 V DC delivered through an uncovered third rail on either side of the running rails.

All of the companies that bid on supplying the electrical equipment had devised the same solution—using "locomotive"-style motor cars hauling trailers. This system had the same drawback as steam locomotives, which required a "relay" motor car at the terminals. Sprague was hired as a consultant to oversee the electrification of the system and proposed the idea of using “multi-unit operations” (MUs) (Fig. 3), which would enable the engineer to control the motors of an entire train of cars from a single operating position at the front of the train. This would eliminate the need for separate motor and car trailers.

Sprague successfully demonstrated his MU technology with a two-car train at the General Electric Company plant in Schenectady, N.Y. Just over a week later, he bested himself with the successful operation of a six-car train.

The first successful demonstration on the "L" took place on November 12, 1897, for officials of the South Side Elevated and Union Elevated companies. The train was then tested during actual traffic conditions and was deemed a success, and in the Spring of 1898, the electrification work was completed. Finally, on April 15, 1898, the first trial run over the entire line with an electrically powered MU train was conducted, and several days later, the first 20 electric cars entered revenue service.

Sprague’s passion for motors allowed him to overcome some of the great challenges at that time with several comprehensive systems he designed or improved upon, including improved energy systems, wheel suspension, automatic controls, and automatic braking systems (a safety feature). His success proved the efficiency, safety, and financial viability of an electric-powered streetcar. So much so that within a decade, horse-powered carriages and cable cars were all but obsolete.

Electric-Powered Elevators

After seeing Richmond’s viability of using Sprague’s electric-powered trolley system, Boston quickly followed suit and became the second city to adopt his design. By 1905, 20,000 miles of streetcar tracks had been laid in the U.S., and his systems had been used as a basis for competitors at the time, including Westinghouse and General Electric.

By 1890, Sprague sold his Electric Railway & Motor Company to Edison and formed a new venture that aimed to tackle vertical transportation. With the Sprague Electric Elevator Company (Fig. 4), the inventor looked to phase out hydraulic and pneumatic steam elevator systems with those powered efficiently by electricity.

Sprague and associate Charles Pratt partnered to bring his electric-powered elevators to fruition. The pair employed the same method Sprague devised to power his electric street railway system of returning power to main supply systems. The new elevator could carry heavier loads and move more quickly than hydraulic or steam elevators (Fig. 5). He would sell nearly 600 elevators for buildings around the world before selling the Sprague Electric Elevator Company to the Otis Elevator Company five years later in 1895.

Sprague would go on to continue his work, serving on the Commission for Terminal Electrification of the New York Central Railroad, where he designed an automatic train control system to ensure compliance with trackside signals. In fact, he established a new company, the Sprague Safety Control & Signal Corporation, to build the system. He would also go on to serve the Naval Consulting Board during World War I, after which, he went back to developing safety systems for elevators—even devising a system to run two elevators in a single shaft at different speeds.

An Award-Winning, Everlasting Legacy

After an amazing career that spanned a lifetime, Sprague would pass away on October 25, 1934, at the age of 77. His son Robert would pick up his torch and go on to found and head the Sprague Electric Company as its president and CEO. During its height, Sprague Electric employed 12,000 people worldwide. The company became a leading manufacturer of capacitors and other electronic components before it was bought by General Cable in 1979 and then Vishay Intertechnology in 1992.

His developments in electric traction helped cities grow larger, while his electric elevator systems could carry the weight of that expansion. Sprague’s achievements are numerous and denoted through his many awards and achievements. Among them were the gold medal at the International Exposition of Electricity held in Paris in 1889, the grand prize at the Louisiana Purchase Exposition in 1904, and the Elliott Cresson Medal in 1904.

Sprague would also go on to win the Edison Medal of the American Institute of Electrical Engineers (now IEEE) for "meritorious achievement in electrical science, engineering and arts as exemplified in his contributions thereto" in 1910. His legacy can be seen in the modern light rail and rapid transit systems we still use today, over a century later.