Machines useful for wind turbine and ship propulsion purposes include a wind turbine generator or a ship propulsion motor with two concentric air gaps. In one embodiment, the machine includes a rotor with an inner rotor core and an outer rotor core; and a double-sided stator with an inner stator side and an outer stator side. The double-sided stator is concentrically disposed between the inner rotor core and the outer rotor core.