Wankel Rotary Engine

This is a model of a Wankel internal combustion engine. The rotor turns freely by rotating the knob in the back.

I made the model as easy to print as possible. Parts that need to be glued include:

1) The spark plug, although that's optional.
2) The output (hex) shaft.
3) The shaft collar, which locks the eccentric shaft and rotor into position.
4) The turning knob.