Shay locomotive

The Shay locomotive was the most widely used geared steam locomotive. The locomotives were built to the patents of Ephraim Shay, who has been credited with the popularization of the concept of a geared steam locomotive. Although the design of Ephraim Shay's early locomotives differed from later ones, there is a clear line of development that joins all Shays.

Ephraim Shay (1839–1916), was a schoolteacher, a clerk in a Civil War hospital, a civil servant, a logger, a merchant, a railway owner, and an inventor who lived in Michigan.

In the 1860s he became a logger and wished to devise a better way to move logs to the mill than on winter snow sleds. He built his own tramway in 1875, on 2 ft 2 in (660 mm) gauge track on wooden ties. This was much more efficient than his competitors because he could log all year round.

Two years later he invented the Shay Locomotive. In about 1877 he developed the idea of having an engine sit on a flat car with a boiler, gears, and trucks that could pivot. The first Shay only had two cylinders and the front truck was mounted normally while the rear truck was fixed to the frame and could not swivel, much as normal drivers on a locomotive. He mounted the 3-foot (914 mm) diameter by 5-foot (1,524 mm) tall boiler centered on the car with the water tank over the front trucks and the Crippen's engine mounted crossways over the rear trucks. Shay experimented first with a chain drive from the engine through the floor to the truck axle. It is not known if he powered one or both axles, but he soon found that the chain drive was not practical and he next tried a belt drive. It did not take long for the idea to become popular.

Shay applied for and was issued a patent for the basic idea in 1881. He patented an improved geared truck for his engines in 1901.

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