A rotation piston internal combustion engine has a substantially stationary housing defining a plurality of blind holes, and a rotor rotatably mounted within the housing for rotation at a substantially uniform velocity about an axis. A hub has four pistons and is rotatably mounted within the rotor for rotation about the axis at a non-uniform velocity. Four crankshafts are each rotatably mounted through a respective rib of the rotor and coupled to a respective gear wheel so that the gear wheel rotates with the crankshafts. A ring gear is coupled to the housing for engaging the gear wheels to permit rotation of the gear wheels relative to the housing. The ring gear has a plurality of apertures having a second diameter, each corresponding in position to a respective blind hole in the housing. The ring gear is elastically coupled to the housing via a plurality of connector bolts mounted so that one end of each connector bolt is engaged in a blind hole of the housing and the other end of each connector bolt is engaged in a corresponding aperture of the ring gear with a tight fit, and each connector bolt has an elastic coating over the end engaged in the blind hole of the housing.