Rotary piston internal combustion engine

A rotary piston internal combustion engine including a housing having a two lobed epitrochoidal inner peripheral surface, end casings for the housing, an output shaft journalled in the end casings, a three flanked rotary piston within the housing mounted on the shaft eccentrically with respect thereto and geared to rotate at one third speed of the output shaft whereby working chambers are formed between the rotor flanks and the inner surface of the housing, the rotor having side seals which engage with inner side faces of the end casings, a cooling circuit around which a cooling medium is circulated for cooling the rotor, the cooling circuit including at least one internal passageway provided in the rotor and a passageway in each end casing, the internal passageway of the rotor and the passageways of the end casings aligning as the rotor rotates, and the cooling circuit further including a cooling heat exchanger, a circulating pump and connecting ducting, the cooling medium being provided by blow-by gasses which have leaked from the working chambers past at least one of the side seals of the rotor to the cooling circuit.