Abstract: The conventional pedal crank drive from DE 43 11 404 C2 has second crank arms (2), connected to the outside of the first crank arms (1), by means of a rotating joint (3) and each comprises a pedal (5), with adjustable angular inclination. Said drive system has the problem that the extended pedal crank unit does not have the required stiffness before the bottom deadpoint to convert the full pedal traction force into torque. According to the invention, said problem is overcome whereby a carrier plate (4) is arranged on the first crank arm in the vicinity of the rotating joint (3) with an angular adjustment and a ratchet mechanism (7) is arranged on the second crank arm, such that the rotating joint is periodically locked in the region of the bottom deadpoint and hence a double length rigid force arm is formed, whereby the pedal traction force is ergonomically converted into maximum torque with the large radius from A to B.