Abstract: A mechanism for powering a combine header unit at infinitely variable speeds. A primary motor is coupled to a primary input shaft via a clutch, a variable-speed secondary motor is directly coupled to a secondary input shaft, and the header unit coupled to a header output shaft. A planetary gear-train couples the primary input shaft, the secondary input shaft, and the header output shaft to each other. A primary brake is coupled to the primary input shaft, and a secondary brake coupled to the secondary input shaft. A control circuit is employed to command the operation of the clutch, the secondary motor, the primary brake, and the secondary brake in response to operator commands.