Jawn Henry: Experimental coal-fired steam turbine locomotive, built
in 1954 by Baldwin-Westinghouse for the Norfolk & Western Railway.
The locomotive weighed some 409 tons, was rated at 4,500 horsepower, produced 199,000 pounds of tractive effort, and could haul more tonnage on less fuel than convention steam engines, but at lower speeds. The engine was scrapped in 1957.
MacArthur engine: Redesignated name for the Mikado-type (2-8-2) steam locomotives in honor of General Douglas MacArthur. The locomotive was used by a handful of railroads during World War II.
Mallet: A type of articulated compound steam locomotive with two sets of cylinders, rods, and drive wheels under one boiler. The non-swiveling rear engine works at boiler pressure, and the swiveling front engine uses exhaust steam from the rear engine.
Developed by Swiss inventor Anatole Mallet (mal-LAY, but often
pronounced MAL-ley in the U.S.), this type of locomotive was
substantially bigger than its predecessors, and was popular between
Mike: Short for a Mikado (2-8-2) steam locomotive.
Pop valve: The safety or pressure release valve on a steam locomotive boiler.
Quarter-locked: Condition of a steam locomotive when it is
stopped so that the drive rods are directly aligned with the piston
which does not allow for the locomotive to be moved. The two sides of a steam locomotive are "quartered" (one-quarter rotation out of phase with each other) to prevent quarter-locking from occurring.
Radius rod: On a steam locomotive, the small rod that transfers motion from the valve gear mechanism to the valve rod.
Saddle-tank: A steam locomotive which carries its water supply in a tank which straddles the boiler.
Shay: Type of geared steam locomotive desinged by Ephraim Shay and built by the Lima Locomotive Works. The most common of the geared steam engines, it featured a set of vertical cylinders on the right of a boiler offset to the left. The cylinders drove a longitudinal shaft that drove the axles through bevel gears.
Smoke deflector: An object placed on both sides of a steam locomotive's boiler near the smokestack that would create air currents to lift the smoke above the boiler. The purpose of the deflector was to increase the crew's visibility and keep smoke out of the cab.
Superheater: A series of coils containing freshly created steam that pass through flue gasses to increase the temperature of the steam and make it more powerful. Once steam has passed through superheater coils, it adds 25 to 30 percent more power to an engine.
Thermic syphon: In a steam locomotive firebox, a funnel-shaped steel fabrication that connects the bottom of the throat sheet and the crown sheet. Water flows upward through the syphon, connecting the coolest and hottest parts of the locomotive boiler. Syphons improved water circulation in the boiler and insured more uniform temperatures in the boiler, increasing fuel efficiency.
Three-cylinder steam locomotive: A steam locomotive containing a third cylinder located under the smokebox between the two outside cylinders. It transmitted power to the driving wheels by means of a main rod which was connected to the center of a specifically designed crank axle.
Water glass: Device in the cab of a steam locomotive by which the water level in the boiler may be monitored by the engine crew. Indicates the depth that water is covering the boiler crownsheet, as it should be to prevent an explosion.
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Steam Locomotive Definitions