Abstract: A rotary engine having a three apex rotor rotatably and eccentrically mounted on a driven shaft. The rotor having a central internal ring gear meshing with an eccentrically mounted pinion gear. The pinion gear drives the driven shaft with a 1:1 ratio and the eccentricities of the rotor and the pinion gear are of equal magnitude and direction so that the gears stay in contact. The eccentricity of the gears is not fixed with respect to the size of the gears. The pinion gear is fixed on a shaft spaced from the driven shaft and supports the ring gear and the rotor as it is driven by the rotor.