AN ELECTRO-MECHANICAL CONTROLLABLE-PITCH PROPELLER

An electro-mechanical replacement for hydraulically-actuated controllable pitch propellers is described. The proposed mechanism applies a thread to the rotating shaft driven by the ship’s prime mover onto which a ferromagnetic nut is threadedly mated and spun by a stator-born electromagnet; the axial motion of the nut is used to manipulate the pitch of the rotatable blades. The design completely removes any mechanical coupling between the rotor and stator systems. An argument for the mechanism’s efficiency, ease of maintenance, and reduction of weight is provided in the form of reasoning by analogy for the already well studied differentiation between hydraulic and electric cylinders. Efficiency gains of 2-3 times, a doubling of mean-time-between failure, and a reduction of weight by 10% are inferred.