Adjustable cycloidal speed reducer

A drive mechanism comprising an input shaft having eccentric means mounted thereon and an output shaft with said input and output shafts being rotatable at relatively different speeds, a movable member adapted for orbital movement imparted by said eccentric means and connected to said output shaft for imparting movement thereto, a plurality of rotatable, tapered concentric bearings each having a tapered bearing surface adapted for bearing contact with a peripheral surface of said movable member, each said bearings having a longitudinal axis parallel to a main common axis of said input shaft and said output shaft, means for moving said bearings axially relative to said peripheral surface of said movable member to achieve contact between said bearing surfaces and said peripheral surface, and selectively adjustable means for rigidly maintaining said contact.