Generalized polygonal Wankel engines
The trigonal Wankel engine is kinematically based on the motion where a circle pm of radius 3d, as the moving pole curve, rolles on the circle ps of radius 2d, as the standing pole curve in the interior. Then the regular trigonal rotor with circumcircle of radius ρ > 3d, fixed concentrically to the moving pole circle, describes its orbit curve cρ . This orbit curve cρ is crutial in forming the engine space. Answering a question of István Revutzky, we prove (and animate by computer) that cρ is a convex curve iff \rho bigger or equal to 9d. The parallel curve cρ+r with distance r will be the solution to the engine space if the triangle rotor touches cρ+r with small roller circles of radius r centred in the vertices of the triangle. All these concepts will be generalized - with animation - to a k-gonal rotor (2 < k natural number) in a unified way.