This unique model airplane engine is an OS 49-PI Type II Wankel engine. The Wankel engine was designed by Felix Wankel, and was used early on in pumps before being applied to auto engines. In 1970, the OS engine company, in conjunction with the German model building company Graupner, developed the first Wankel for use in model airplane flying.
Power Output: 1.27 bhp at 17,000 rpm
Weight: 335g (11.8oz)
Practical rpm: 2,500-18,000 rpm
Crankshaft thread: 1/4-28
Propeller: 9×6-7, 10×4-6 or 11×4-5