Abstract: A bicycle crank mechanism comprises a main crank, a follower crank, and a connecting lever disposed between free ends of the main and follower cranks. A second fixed fulcrum shaft of the follower crank is arranged obliquely upwardly and backwardly of a first fixed fulcrum shaft of the main crank, the follower crank extending downward beyond a line connecting the first and second fixed fulcrum shafts from the second fixed fulcrum shaft such that the second free fulcrum shaft is swung below the line connecting the first and second fixed fulcrum shafts. A pedal is attached to a projection end of the lever and arranged in the vicinity of the free end of the main crank, the pedal being rotated along a non-circular track passing between the first and second fixed fulcrum shafts, and the first fixed fulcrum shaft being located at an internal area of the track.

Abstract: To reduce the load alternately imposed on the rider's legs when the pedals are stepped and to use the muscle of the entire legs in a well balanced manner, thereby naturally returning the pedals to the initial position of the stepping operation without forming an unnatural bending state of each leg at the returning track of the pedal.