Abstract: A motion generating mechanism with a rotary output which comprises a support frame mounting a prime mover coupled through a gear reducer to drive a primary rotary member about a fixed first axis on which a sun gear is concentrically disposed. The primary rotary member carries one or more roller gears that are engaged by the sun gear such that the roller gears rotate about a second axis which is parallel to the fixed first axis and movable with respect to said first axis as the primary rotary gear is driven by the electric motor. Each roller gear has an upper portion on which is mounted a roller adapted to movably engage a slotted section formed in a plate member adapted to be driven by the roller for rotation about the aforementioned fixed first axis such that the motion of a selected point on the plate varies in a combined epicycloidal and harmonic manner relative to the velocity of the primary rotary member.