Armington & Sims Steam Engine, 1888

This high speed engine was built by the Armington & Sims Engine Company, Eagle Street, Providence, RI. It was first delivered to the Narragansett Pier Electric Light Company. It was later used to power the Sea View Railroad that ran from East Greenwich to Narragansett. It has a 12″ bore and a 12″ stroke and produces 75 horsepower at 350 RPM with 175 PSI of steam. This square design is still the preferred ratio of bore to stroke. It has a balanced crankshaft and a Rites governor.

The application of the steam engine to the generation of electric power from about 1881 onward required the development of engines capable of operating at much higher speeds than the 80 RPM of the long stroke engines typified by the three examples of Corliss engines in this museum. Close control of engine speed is needed to avoid flickering of electric lights which receive power from engine driven generators.

The Armington & Sims is an example of a single cylinder, horizontal high speed automatic engine. High speed because it operates at about three times the speed of its larger predecessors. It is called an automatic engine because of the sensitivity of its flywheel mounted inertia governor. This governor detects the speed as well as the rate of change of speed, which results in a much more rapid response to sudden variations in the engine’s load. This governor consists of heavy weights mounted on pivoted arms held inward by stiff coil springs in tension. The pivot points are offset and on the opposite side of the shaft center from the weights rather than at the shaft center as in the Watt governor. The mass of the arm is so distributed that when engine load changes gradually the governor acts as a centrifugal governor, but with a sudden change in load the inertia of the arm augments the centrifugal action resulting in a very high response speed. Edison came to Providence and contributed suggestions to Gardner Sims on this design. Edison had previously studied centrifugal governors to get more exact speed control in his photographs. Edison replaced the Porter Allen engines in the Pearl Street station with Armington & Sims and for many years preferred them.

When the Sea View Railroad discontinued service in 1922 Henry Ford bought the engine and generator and moved it to his museum in Dearborn, MI. The Henry Ford museum had several of these engines and donated this engine to the NEWSM.