Geared Locomotives - Pacific Coast Shay (Lima Shay)
The Shay geared locomotive was invented by Ephraim Shay in 1879 to meet the
needs of the logging industry. There was a demand for a strong, flexible type of
locomotive to negotiate steep grades and tight curves. The Shay was first built
with diminutive two cylinder vertical steam engines and used on locomotives
weighing twenty tons. A three-cylinder vertical engines were soon added.
The steam engine is mounted on the right side of the boiler and the boiler is offset
to the left to compensate for the engine’s weight. The front view of a Shay shows
the boiler being offset from the centerline of the locomotive; however, it is the
offset of the boiler that keeps the locomotive in perfect balance.
The connecting rods of the engine are coupled to a crank shaft which is connected
to the drive shafts by universal and slip joints. Small pinions are attached to the
driving shafts and engage the gears on the truck wheels.
The geared wheels are only located on the “engine side” of the locomotive with
two geared wheels per truck. There are two trucks under the locomotive. In later
years, one or two additional powered trucks were used under an auxiliary tender.
The Shay locomotives were built by The Lima Machine Works (later called The
Lima Locomotive Machine Works) of Lima, Ohio.
Shay locomotive near Antigo, Wisconsin, about 1908.
Shay Locomotive near Aberdeen, Washington.
The Iron Steed, a Shay geared steam locomotive owned by the
Mt. Tamalpais and Muir Woods Railway (a "gravity" railroad) of
Marin County, California.

Site Coordinator: Lori Niemuth Last updated: December 27, 2007