This invention relates to improvements in rotary fluid motors operable with an expansible fluid such as steam, freon and the like.  With the present problems of pollution of the atmosphere by exhausts of conventional gasoline combustion engines, considerable attention is being given to the development of engines which are virtually smogless with no polluting exhaust into the atmosphere from the engine proper. 
Steam engines are well known and provide a smogless type of exhaust.  However, such engines are usually quite complicated and to date have failed to provide a suitable replacement for gasoline combustion engines.