Orbital engine

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Engine incorporating OCP (Orbital Combustion Process), on display in Jakarta

The Sarich orbital engine is a type of internal combustion engine, invented in 1972 by Ralph Sarich, an engineer from Perth, Australia, which features rotary rather than reciprocating motion of its internal parts. It differs from the conceptually similar Wankel engine by using a shaped rotor that rolls around the interior of the engine, rather than having a trilobular rotor that spins "in place".


The theoretical advantage is that there is no high-speed contact area with the engine walls, unlike in the Wankel engine in which edge wear is a problem. However, the combustion chambers are divided by blades which do have contact with both the walls and the rotor, and are said to have been difficult to seal due to the perpendicular intersection with the moving impeller.

Sarich worked on the concept for a number of years without ever producing a production engine. A prototype was demonstrated, running on the bench with no load. The engine, which produces very high revs, has eight moving parts in the six-chambered version depicted in the patent application, plus valves for each chamber. It can supposedly be powered by compressed air or steam[1] and can be run as a pump.

In the patent, the engine is described as two-stroke internal combustion engine,[1] but the patent claims that with a different valve mechanism it could be used a four-stroke engine.[1]

A blower is required as the two stroke cycle does not provide suction to draw the mixture into the chamber.[1]

Technical Problems[edit]

The Sarich orbital engine has a number of fundamental unsolved problems that have kept it from becoming a usable engine. Some key components cannot be cooled and others cannot readily be lubricated, so it is very susceptible to overheating.[2] At one press conference at which Sarich presented the engine, automotive engineer Phil Irving (designer of the Vincent Motorcycle and Brabham Formula One engines) pointed out a number of technical difficulties. Some processes developed for the engine could be used for other engines, such as the Orbital Combustion Process, an air/fuel precompresser for injection.


See also[edit]


  1. ^ a b c d https://www.google.co.in/patents/US3787150
  2. ^ "Fuel saving follies". ABC Radio National: Ockham’s Razor. 2009-08-30. Retrieved 2012-06-29.