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Modern Steam Patents

(updated January 12, 2008)

The following links are to patents on the Google patent site.  Most are for interesting components or concepts patented in the latter days of mainline steam in the United States (~1945-1955).

ACE 3000 Patent- 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- 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- 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- A patent by boiler manufacturer Babcock & Wilcox for an improved tender arrangement.

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

Reverse Gear for Franklin Type "B" Poppet Valves- Shows a reverse gear for Franklin Type "B" or "RC" (rotary cam) poppet valves, as well as the rotary cam drive gear.

Franklin "Long Compression" Poppet Valves- 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.

Combustion air preheaters- Combustion air preheating is common on power plants but almost unknown on steam locomotives.  Preheating improves combustion efficiency, and in the case of this patent, was claimed to reduce boiler maintenance by reducing stresses caused by incoming cold air.  These particular preheaters are mentioned in Eric Hirsimaki's book on Lima as having been applied to a C&O 2-10-4 in the 1930's.  However, the man in charge of their testing said they so dramatically reduced boiler maintenance most of the railway's boilermakers could be laid-off and he recommended against their adoption!
Geared Balancing Shafts - Balancing shafts, geared to the crankshaft, have been used in certain internal combustion engines for many years to reduce vibration.  This patent shows a design for applying this concept to 2-cylinder steam locomotives, which were impossible to balance completely with the normally used method of adding weights to the driving wheels.

Watertube boiler patent #1- Will Woodard, famed chief engineer of the Lima Locomotive Works, was convinced that water tube boilers held promise for steam locomotive applications.  He wasw 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
Watertube boiler patent #3 

Watertube boiler patent #4 (high-wheeled locomotive)

Rotary expander driven steam locomotive- 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.

Exhaust steam over-fire jets- Over-fire jets were applied to steam locomotives to introduce "secondary" combustion air to the firebox to improve combustion.  The extra air was admitted above the fire to aid in the combustion of gases released by incomplete combustion of coal.  Most designs used live steam jets blowing through openings in the sides of the firebox to induce air to flow into the firebox.  This patent covers over-fire jets which would have used exhaust steam to induce the secondary airflow. This would have had the advantage of being largely self-regulating, as the harder the engine was worked the more secondary air would be admitted. 

Dynamic Brakes- Conventional train braking systems relied on brake shoes pressed against the wheels of the cars and locomotive to retard the train.  The brakes were actuated by vacuum or compressed air and worked well in most instances.  However, in mountainous areas which required extended brake applications, overheating of the train's wheels could result and brake shoe wear was rapid. "Dynamic" brakes were made popular shortly after the introduction of diesel-electric locomotives.  This form of braking turned the diesel locomotives drive motors into generators which fed their current to electrical resistance grids on the top of the locomotive.  This could be used to help slow trains on long down grades without the use of conventional brakes.  The ability to use dynamic braking was considered to be a significant advantage of diesel locomotives over steam.  However, a form of "dynamic" braking was possible with steam: the counter-pressure brake. This basically converted the locomotive's cylinders into a compressor, which retarded the train.  This form of braking was employed on several mountain railways in Europe but seems to have been almost unknown in the U.S.  This patent covers details for an improved form of counter-pressure braking for steam locomotives.

Nuclear reactor design for locomotive - In the 1950's, nuclear energy was thought to be the power of the future, and designs were prepared for everything from nuclear powered aircraft to nuclear powered railroad locomotives.  This patent covers the design for a nuclear reactor for a locomotive, which would have course been steam powered.  Fortunately, it wasn't long before designers realized that the potential drawbacks to nuclear power in these applications (imagine a train wreck with a nuclear locomotive) outweighed their potential benefit.  Nuclear power is used to power trains, but via generating electrical power at large stationary plants which powers electric locomotives.

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