Rotary Steam Engines: Page 4

Updated: 15 April 2018

Moss engine added
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Race engine: 1871
Left: The Race rotary engine: 1871

This engine was patented by Washburn Race of Lockport, New York. Race was his surname and there is no suggestion that this engine was intended for any form of racing.

In Fig 1, D is the steam inlet pipe. C is a hollow shaft through which the steam exhausts.

From US Patent 116,352 granted 27 June 1871

The engine uses two swinging abutments h and h' that double as inlet valves, but this time they are constrained in the hope of making them move smoothly, rather than just banging about in the cylinder. The valves open because of the steam pressure behind them; the speed of opening is controlled by the incline i attached to the rotor. (Top left of Fig 2) The inlet valves are closed again by the ramp S, also attached to the rotor. Steam exhaust is through the duct k into the hollow central shaft.

Apart from his patent, Washburn Race is unknown to Google, so it is fair to conclude that this engine did not thrive.


Stocker Rotary Engine: 1872
Left: The Stocker Rotary Engine: 1872

"The sector pistons are each connected through central concentric shafts to slotted cranks in which a sliding box and link connect to a crank on a shaft eccentric to the sector shaft. A differential movement of the sectors is produced while rotating which rotates the driven shaft by the outside slotted crank connections."

An example of the "pursuing pistons" approach to rotary engine design. Reuleaux says, that as a consequence of the large area between the outer surface of the pistons and the inside of the cylinder, "The joint between piston and chamber can without difficulty be made steam-tight,..."

From "Mechanical Movements, Devices and Appliances" Hiscox, 1899


Moss Rotary Engine: 1875
Left: The Moss Rotary Engine: 1875

This engine comes from Dublin, Ireland. The inventor claims that it is the first single-cylinder rotary engine with no dead-point, ie no dead-centre position where it will not move when steam is applied. This seems highly unlikely.

Secondly he appears to claim that constant torque is obtained whether the engine is run expansively or not; this seems doubtful but his explanation of the steam flow is too obscure for any judgment to be made.

There is no menton of a patent, which is unusual. Charles E Moss and his engine are unknown to Google.

Thanks to Paul Burke for drawing this engine to my attention.

From English Mechanic and World of Science 1875


The four rotary steam engines below were illustrated in the US journal "Manufacturer & Builder" for June 1880. Extracts from the contemporary description are in green text. The seals and packings- usually the Achilles Seal of these machines- is highlighted in red or pink, where feasible.

The Pillner-Hill rotary steam engine .
Left: The Pillner-Hill rotary steam engine; cross-section. An English design of the "gear-pump" type.

"The Pillner-Hill has two cylindrical overlapping chambers, and two systems of rotary pistons, which may be compared to cogwheels. These wheels, by the close contact of their cogs, prevent the passage of steam between them, and they are adapted steam-tight to the interior of their cylinders by metallic packing in the tips of their teeth."

The Pappenheim pump appears again. This design appears to be reversible; by rotating the plug cock on the right steam can enter on either side of the rotors. There seems no possibility of expansive use of steam; it probably worked but it would have been dreadfully inefficient. The design is related to the gear-type oil pumps widely used in car engines. This was the type of engine built by Murdoch.

Anonymous rotary steam engine
Left: An anonymous design, (though it looks very much like the Birdsall Holly engine) again of the "gear-pump" type.

Once more the exhaust "eduction" pipe is no bigger than the inlet. The expansive use of steam looks to be impossible. Engines like this are inherently reversible, given suitable steam connections.
The design is similiar to the Roots blower widely used as a supercharger for IC engines.

Anonymous rotary steam engine
Left: Another anonymous design reminiscent of the Shorrocks blower, which was once much used for supercharging IC engines.

"...has four distinct pistons, which slip in and out in the eccentric hub."

At first this looks unworkable as the steam volume expands and then contracts again before the exhaust port is reached allowing no work to be done. However the pipe at the left may not be the exhaust, but an alternative steam inlet for reversing, and there is probably an exhaust port at the bottom, not shown in this contemporary drawing.
The twiddly bit on the right appears to be just a steam admission valve.

Anonymous rotary steam engine
Left: A anonymous rotary design that typifies a common approach to the problem; hinged "abutments" that swivel out of the way as the three "pistons" on the rotor go past.

"The engine has three pistons, two abutments, and two induction and eduction ports."

Here there is at least the possibility of expansive use of steam. However, note that the exhaust "eduction" pipe is no bigger than the inlet. This looks suspicious, but might just be bad drawing.
Rotary steam engine designers were very fond of "abutments" that swung out of the way (or were knocked out of the way) at convenient times, though they inevitably made the engine inherently non-reversible, like this effort here. Given that it has three pistons and two abutments, this might be the Cartwright engine of 1797.

See also the Knowles rotary engine, which has its own page. Its exact date is unknown but appears to be around 1880.

The story of the Rotary Steam Engine continues on Page 5 of this gallery.

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