Abstract: Apparatus of dual partially independent mechanism to propel bicycles or other vehicles, having a bottom bracket shell attached to a frame, a pair of main shafts mounted separately in said bottom bracket shell, a pair of propulsion levers supporting operating pedals, a pair of arcs each arc attached to each propulsion lever which is mounted on each main shaft, a pair of chains, each chain hooked with one end portion to one arc, and the other end portion of the chain entrained around one of the two freewheels which are mounted on a wheel hub which is disposed rearwardly of the bottom bracket shell, a pair of springs, each spring hooked from one end portion of a chain to the rear portion of each lever respectively.