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Steam Locomotion in the 21st Century

The Recent History of Steam Locomotive Development

Modern Steam Patents

updated 7 February 2022

The following links are to PDF's of US patents. Most are for interesting components or concepts patented in the latter days of mainline steam in the United States (~1945-1955), while a couple are from the 1980's when there was real interest in new coal-fired locomotives.

ACE 3000 Patent US4425763 The patent for the modern steam locomotive devised in the early 1980's by American Coal Enterprises, the locomotive which first inspired these web pages.

Mobile coal-fired fluidized bed power unit- US4633818 A patent by boiler manufacturer Combustion Engineering from 1987. This shows that ACE wasn't the only U.S. company thinking about modern steam in the 1980's.
Steam Powered Locomotive with Water Tube Steam Generator US2879717 A patent assigned to boiler manufacturer Babcock & Wilcox, undoubtedly forming a basis for the steam turbine electric locomotive built for the Norfolk & Western Railway, "Jawn Henry" (no. 2300).

Locomotive tender- US2691455 A patent by boiler manufacturer Babcock & Wilcox for an improved tender arrangement.

Franklin Poppet Valves- US2401764 Applied to a few modern steam locomotives in the U.S.; offered improved steam distribution over conventional piston valves.

Drive System for Franklin Type "A" Poppet Valves- US2183327 Shows the mechanism for operating Franklin Type "A" or "OC" (oscillating cam) poppet valves.

Reverse Gear for Franklin Type "A" Poppet Valves US2385957

Franklin Rotary Cam Type "B" Poppet Valves US2441156 Shows the valve arrangement for Franklin Type "B" or "RC" (rotary cam) poppet valves.

Franklin Rotary Cam Drive System- US2441199 Shows the drive system for Franklin Type "B" or "RC" (rotary cam) poppet valves.

*Franklin Type "C" "Long Compression" Poppet Valves- US2518403 A development of the Type B rotary cam poppets, the camshaft profiles were designed to improve the starting and low-speed traction of steam locomotives, one of their weak points compared to diesels.

 Franklin Type "B-1" Rotary Cam Poppet Valves US2518024 A late development which eliminated the need for manual cut-off adjustment by the engineer. The valves were controlled with a three-position lever with forward, "neutral" and reverse positions. Steam admission was regulated by a fairly complex cam profile which effectively gave full steam admission at low speeds, partial admission at medium speeds, and short admission at higher speeds. This gear was installed on only one steam locomotive US Army Transportation Corps (USATC) 2-8-0 611, which was preserved and currently belongs to a private owner. Franklin engineer Raymond Delano claimed that this gear gave similar steam economy while being significantly easier to repair and adjust compared to conventional piston valves.

Watertube boiler patent #1- US2318040 Will Woodard, famed chief engineer of the Lima Locomotive Works, was convinced that water tube boilers held promise for steam locomotive applications.  He was particularly interested in the adaptation of the LaMont marine-type forced circulation water tube boiler to steam locomotives, and this patent and the two below cover this concept.

Watertube boiler patent #2 US2318040

Watertube boiler patent #3  US2346716

Watertube boiler patent #4  US2366465 (high-wheeled locomotive)

Rotary expander driven steam locomotive US2417084 Many attempts were made to devise alternative driving arrangements for steam locomotives other than the traditional reciprocating pistons and rods.  This patent shows a design using twin-lobed rotary expanders, like the Roots blowers used as superchargers on GM 2-stroke diesel engines, to turn the drivers.

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