Wankel rotary engine powered thousands of aircraft. One of several problems: It spewed castor oil on its pilots.

Click to open image viewer. This somewhat unique artifact is an air-cooled, two-stroke cycle rotary aircraft engine designed and built by Paul Daniel of the Daniel Engine Company of Bound Brook, New ...

In a world dominated by pistons, the rotary engine was something different for motorists. It was the vision of German engineer Felix Wankel, built on the belief that the up-and-down motion of pistons ...