On 18/03/2014 23:39, Brian Gaff wrote:
Is this the Wankel one with that weird triangular piston rotaor?

No, it is a 19th century design, with five air cooled cylinders that
rotate around a fixed vertical crankshaft. Having the cylinders rotating
does away with the need for a flywheel, giving a good power to weight
ratio, and creates a forced draught over them that improves cooling
efficiency.

Similar designs were used in world war I fighter aircraft. However, the
gyroscopic effect made turning them rather interesting.

Colin Bignell