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Non-Wankel Rotary Engines

Nature Always Does it First

The F1-ATPase enzyme has a tiny structure 10x10x8 nm that is analogous to an engine block, and a drive shaft. It rotates at 30 to 240 rpm. The "block" is based on a triangular arrangement of three subunits.

Hiroyuki Noji, Ryohei Yasuda, Masasuke Yoshida, and Kazukiko Kinosita Jr., "Direct Observation of the Rotation of F1-ATPase", Nature 386 (Mar. 1997), pp. 299-302. Separately there are a diagram and four ".mov" files (400 to 1700 KB) available.

O'Brien, C. (1994), "New Enzyme Structure Reveals Cell's Rotary Engine", Science, 265(5176), 1176-7.

Bacterial flagellum form a larger rotary motor from a complex of about 100 protein molecules. H.C. Berg and R.A. Anderson, Nature 245, 380-382 (1973).

side view
side view

Engine Types

There are three main types of true rotary engines:

  1. Wankel types based on eccentric rotors (Wankel, Quasi Turbine, Veselovsky, Shah)
  2. Scissor action types using vanes or pistons (RandCam, Cir-Com, Thalo, Sanchez, RVICE, Tschudi, Kauertz, and Virmel)
  3. Revolving block types ('cat and mouse' types) (Mercer, Selwood, and Porsche).

Popular Science, "Rivals to the Wankel: A Roundup of Rotary Engines", Jan. 1967, pp. 80-85.

Rand Cam

The Rand Cam Direct Charge engine (formerly called Rotary Diesel) is one of the main alternatives to the Wankel type RCE and was invented by James McCann in 1983. It is being developed by Reg Technologies of Richmond, British Columbia, Canada. It uses sliding vanes, but manages to avoid valves. A NASA Rand Cam rotary diesel aircraft project successfully completed Phase 1 in June 1999. Evaluation and improvements have been contributed by CIRA, W. Virginia University and has been contracted with Adiabatics, Inc. to build a second prototype. A technical article is referenced through one of the EREN search pages.

The Axial Motor (DRAE) is related to the Rand Cam. They have an informative second site with some more information. It includes a comparison of a few rotary engines.

There is an article with an illustration about the RandCam in the Kansas State Engineer magazine (Vol. 81, No. 3, Spring 1996). Note that the article by Theron Muller is inaccurate about the Wankel in several points: 1) Compression ratios are 8 or 9, about the same as piston engines, not the 4:1 stated. 2) The chamber is epitrochoidal, not circular. 3) The Rand Cam will not be the first diesel rotary, the Curtiss-Wright and Rolls-Royce engines predate it by decades. 4) The statement "There just was not any way to keep the engine together efficiently", exhibits muddled concepts. 5) Any problems with dieseling rest with the Rand Cam, and not the Wankel, since the timing never "gets off a little", owing to the fixed geometry.

Lockheed Martin was developing a rotary powered Unmanned Aerial Vehicle for tactical reconnaisance. The page linked in the next paragraph indicates this might be a Rand-Cam. The engine will have two rotors, "large displacement", stratified charge, oil cooling, and will take heavy fuel (JPG-5 and 8). The advantages needed are high power to weight ratio, low vibration at 6000 rpm, and low parts count for logistic simplicity.

Rand-Cam and Alliant TechSystems propose to power a UAV with this engine (Pop. Mechanics, Sep. 1995, Jan. 1994).

A possibly related development is the AR-741 engine from UEL (UAV Engines Litd., United Kingdom). It flew in Maryland in March 1997 in the Pioneer UAV 201 aircraft, according to a press release. The AR-80-1010 engine is used in the Hermes 450S Unmanned Airborne Vehicle

Another UAV using a "rotary piston engine" of some kind (unspecified) is the Dragon.

Miscellaneous (alternatives to the alternative to the alternative engine)

The Pelleja Rotary Internal Combustion Engine site has an informative animation of a novel rotary engine concept that uses spring-loaded seals. The inventor, from Brampton, Ontario, Canada, has analysed the Wankel rotary engine and chosen a modified approach aiming at improved performance. A demonstrator model has been run and photographs are at the site.

The Ball Piston Engine site is well-organized and informative. It includes diagrams and test results. The engine has a dozen balls that move around in an elliptical chamber.

The Cir-Com Goodman Circular Rotary Engine was invented by William A. Goodman who was awarded patent 5,036,809 on Aug. 6, 1991, which he assigned to Cir-Com Development Corporation. It seems there is a full scale model in existence to simulate the engine, and several proposed designs. The site does not explain the principles of operation but has several interesting pictures. It appears to be a multi-bladed design.

The Antonio Sanchez Hybrid Engine from Spain is described at a web site in English(o) and en Espaņol(o). It is a scissor-vane type of engine because it contains internal reciprocating pistons.

Oldrich Nos mentions his Continuous Combustion Rotary Engine invention.

The RVICE Rotary Vane Internal Combustion Engine (RVICE) does not have a working model in existence. Dana Michael Inman admits it appears to be similar to an earlier Bancroft design, who did build some prototypes.

The Dyna-Cam Engine is claimed by some to be rotary, but it actually uses reciprocating pistons with a sinusoidal cam for a crankshaft.

The Newbold powerplant is said to be a turbo reciprocating rotating-block engine. I found out by starting at one of the EREN search pages.

Koichi Hirata has invented a Rotary Displacer Stirling Engine. This means it is not an internal combustion engine, but an external combustion engine.

The OX2 Engine may or may not be a rotary type of engine. It claims to have a spinning block and no crankshaft, but does have pistons. The web site is remarkably devoid of diagrams but has a video.

Pangman has invented a rotating vane engine. I found a reference at one of the EREN search pages.

Wolf Brinsbury of Kokua International has designed a Radial Rotary Engine with diagrams and photographs of a working model. It might be a vane type.

The "something for nothing" folks are at it again. Hartmann has resuscitated an article from Popular Mechanics June 1979 that describes a mis-named "magnetic wankel motor". The inspiration for the wankel designation is the stator that has an air gap that varies from 0.1 mm to 5 mm away from the circular rotor. It is claimed to use less current than conventional motors. It has no connection to Wankel shapes or principles. T.E. Bearden also references the article, but includes a very deep mathematical physics discussion that is impressive.

The "Rev." Clarence G. Horn claims to have patent rights (5,484,272 filed 1994-06-20, granted 1996-01-16) on a new rotary engine called the ELROTO, with a unique mechanical timing system, 35 years in the making. Said to offer "seven (7) time more power then [sic] reciprocating engines of today". This is yet another vane type.

Perlex Inc. Rotary Power Engine. This is not a Wankel rotary engine but is instead a variation, rooted in the Ramelli device from Italy, 1588. The site has a few pictures. It is claimed to provide double the gas mileage at one eighth size and weight. There is also a text page which reads like a press release about a test on Nov. 1, 1985.

Another possible rotary engine is the Split-Cycle engine from Australia.

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Copyright © 1998-2000 Alan Marr. This update notice was last updated May 16, 2000. You can help. You may send your comments or questions to