Rotary Internal-Combustion Engines.

Updated: 19 Oct 2009
Cornu engine added
This gallery is in course of arrangement
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Rotary internal-combustion engine proposals exist in their hundreds, if not their thousands. The similarity with the rotary steam engine in the past is hard to ignore, the difference being of course that in this case a rotary engine achieved some success, in the shape of the Wankel , even if if it took a huge amount of development to get there.
If you have looked at my page on rotary steam engines, you will know that even with steam the problems of sealing and efficiency were severe. Things must surely be an order more difficult in a rotary internal combustion engine, where the pressures and temperatures are much higher.

This page used to contain other engines that were not strictly rotary designs, such as toroidal engines and The Scissor, pursuing-piston, or cat-and-mouse engines. These have now been moved to their own pages in the interest of faster downloads. See the Unusual IC Engines page for a full list.

This web page does not even attempt to provide a comprehensive list of the many rotary internal combustion designs that were promoted, as there are simply too many of them. The dates given here are not necessarily the date on which the proposal was made public, the patent was filed, or anything else precise. It simply means that the project was being actively developed and promoted at that time.
If you know of any good rotary IC engines that should be here, please let me know...

The list below links you to details of the engine, where such details exist on the page. It does not pretend to be a complete list. More engines will be added in time, but probably rather slowly. You know how it is. Of course you do.

Please ignore the #-numbers, this is just a filing system that attempts to keep all this organised. The greyed-out engines have not yet been delivered to the Museum.




Originator: Joseph Webb (of Dalston, in the county of Middlesex, England) British Patent No 1216, 1853.

Left: The Webb engine: 1853

This elegant drawing shows what is believed to be the first proposal for a rotary internal-combustion engine. The combustion gases enter through the central port A, passing through stationary valve B via ports C, D, E and thus into the passages F, G in the rotating piston H, and then expanding further into the volumes I, J and K formed between the rotating piston and the swivelling "buttresses" L, M and N. At the end of expansion the gases left through exhaust ports O, P and Q, which appear to be covered by movable flaps; it is not clear how these were actuated- presumably by some sort of cam mechanism. The swivelling buttresses were held in position against the piston by external weights, which would seem to rule out all but the slowest rotational speeds.

The piston goes round in a clockwise direction.

In the diagram buttresses L and N are making a line "seal" against the piston, which makes leakage inevitable. Ask Felix Wankel.

The combustion gases were presumably generated in some sort of pressurised external burner, but the Museum has currently no information on this, or on what fuel was proposed. Webb's patent application never got beyond the provisional stage, and there is no indication the engine was ever built.

Nice drawing, though.

Left: Animation of The Webb engine: 1853

The passages F, G in the rotating piston can be seen, and the exhaust ports with their swivelling flaps behind the piston.

Another fine animation by Bill Todd.


Originator: Paul Cornu (1881–1944)

Paul Cornu is much better known as a pioneer of the helicopter, though it is generally accepted he made no controlled flights; see Wikipedia. Little is known about this engine, built by Paul and his father Jules, but Leishmann and Johnson, in their paper "Engineering Analysis of the 1907 Cornu Helicopter" state that it would run unloaded but stopped immediately when it was asked to produce any power. See also: Cornu F, "Un pionnier de L´helicoptere: Paul Cornu (1881–1944)", Imp. Moriere, Lisieux, 1969.

This engine has a single sliding vane set in the piston (rather surprisingly, there is nothing that exactly corresponds to it in the Rotary Steam Engine Gallery) It looks like a rather crude production; that wonky spring pushing the vane outwards does not inspire confidence.


Originator: Wilhelm Jasper (New York)

The Jasper Explosive Motor (clearly not a prime mover for the nervous) used the same mechanical principles as the Behrens rotary steam engine and one can only speculate as to how Mr Behrens felt about this.

The holes 9 are "ignition inlets" and burners were maintained just outside these apertures. The sector plates 15 uncovered the ignition inlets and the inlet ports 4 at the appropriate times. The exhaust port is at 22. The engine was water-cooled, with cast water passages such as 27.

Currently nothing is known as to whether this engine was ever built and if so, what the results were. As Bill Todd pointed out to me, it's an inherently inefficient non-Otto cycle engine, as it has no charge compression at all.



Originator: Umpleby (England)

Left: The Umpleby engine: 1908

The Umpleby engine was an attempt to adapt the Cooley rotary steam engine to four-stroke IC operation. It is often cited as the first rotary IC engine, but as you can see above,there were certainly earlier patents, if not earlier working engines.

Facts are in short supply but Umpleby appears to have made little progess with the engine.

From Norbye


Originator: Felix Wankel (Germany)

Left: The Wankel engine: 1957

You don't need me to tell you that the Wankel is the best known of all rotary engines. The WWW carries a huge amount of information about it. There is a good Wikipedia article about it which I am not going to attempt to duplicate here. It does however make the very interesting point that Wankel engines are almost immune to catastrophic failure. A Wankel engine that loses compression, cooling or oil pressure will lose power, and die in a short period of time, but it will usually continue to produce some power during that period. Piston engines are more prone to seizure or part fracture that causes an instant and total loss of power.

In the Wankel engine a triangular rotor incorporating an internal ring gear is driven around a fixed pinion within an epitrochoidal chamber.

Although the Wankel has unquestionably seen more use than any other rotary, it still has problems with seal wear and high fuel consumption. It is not going to replace the piston engine.

The date given (1957) is the year in which the first prototype engine, the DKM54, ran.


Originator: Ralph Sarich (Perth, Australia)

This design gathered a lot of publicity in its day; See Wikipedia.

The Sarich Orbital engine had a number of fundamental and unsolved problems kept it from becoming a practical engine. Amongst these are key components that cannot be cooled and others that cannot readily be lubricated; it is very susceptible to overheating. To which we might add the usual sealing problems.

See United States Patent 4,037,997, "Orbital Engine With Stabilizing Plate", published 1977


Originator: Howard R Chapman (California, USA)

This engine should not strictly be in this gallery of the museum as it was not an IC engine, though it was closely associated with them; it was a "steam engine" powered by Freon. It was intended as part of a bottoming cycle to improve the efficiency of conventional IC engines.

Since it is fundamentally a steam engine, it is to be found in the Rotary Steam Engine gallery, here.

See United States Patent 3,743,451, "Rotary Engine", published 1973



Left: The Siddons S-engine: 1969

Originator: J R Siddons, Australia

This remarkable proposal has a spherical free piston that is bounced from one end of the S-shaped tube to the other, by means of the other cylindrical "pistons" at each end. The reaction force on the sphere as it traverses each curve of the S-tube causes the engine to rotate around the central axis. But what about the reaction force when the ball starts off?

Frankly, I don't think this is the way forward. (or indeed, around)


A huge number of patents for rotary IC engines have been registered. Here is a random sample.

US 2 927 560
US 2 958 312

These are external links; not responsible for the content of external sites. Some of these links are currently dead but are retained here as their titles are the only clue to tracking them down.

The Janova Engine. (University of Arizona)

The Ball Piston Engine. Dead link

The Rand Cam Engine. Dead link

The Antonio Sanchez Hybrid Engine (Spain)

The Dyna-Cam Engine Dead link

The Perlex Engine Dead link

The Veselovsky rotary engine

The Quasiturbine

The Rotary of Koushi Akasaka (Japan)

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