The central drive shaft, called the "eccentric shaft" or "E-shaft", passes through the center of the rotor being supported by fixed bearings. The rotors ride on eccentrics (analogous to crankpins in piston engines) integral to the eccentric shaft (analogous to a crankshaft). The rotors both rotate around the eccentrics and make orbital revolutions around the eccentric shaft. Seals at the apices of the rotor seal against the periphery of the housing, dividing it into three moving combustion chambers. The rotation of each rotor on its own axis is caused and controlled by a pair of synchronizing gears A fixed gear mounted on one side of the rotor housing engages a ring gear attached to the rotor and ensures the rotor moves exactly one-third turn for each turn of the eccentric shaft. The power output of the engine is not transmitted through the synchronizing gears. The rotor moves in its rotating motion guided by the gears and the eccentric shaft, not being guided by the external chamber; the rotor must not rub against the external engine housing. The force of expanded gas pressure on the rotor exerts pressure to the center of the eccentric part of the output shaft.