Disclosed are various embodiments for a motor/generator comprising: a rotor adapted to rotate about a longitudinal axis, the rotor comprising a first partial toroidal magnetic cylinder defining a semi-circular tunnel, wherein the plurality of magnets forming the first partial toroidal magnetic cylinder have substantially all like poles facing inward toward the semi-circular tunnel, the semi-circular tunnel having an entrance and an exit forming an open throat defined by a space between the entrance and the exit, and a stator positioned about the longitudinal axis within a rotational path of the rotor.