Abstract: An apparatus for translating a radial force applied to a crank into additional rotary motion by a crankshaft is described as including a crank mechanically coupled to the crankshaft that is adapted to extend away from the crankshaft and also toward the crankshaft. A spring is used to apply a biasing force to urge the crank toward the crankshaft. According to a first described embodiment, extension of the crank from the crankshaft acts upon flexible chain attached to the crank and to a cam so that extension of the crank causes additional rotation of the cam. The cam is attached to the crankshaft so that the extension of the crank also causes additional rotation by the crankshaft. According to a second embodiment, a pedal carrier arm is disposed at an angle intermediate a pair of members which define a primary crank and is held adjacent to each of a pair of rollers that are attached to the primary crank.