A crank apparatus includes a driven member rotatably mounted to a machine, and a crank arm attached at an inner end thereof to the driven member at a rotational axis of the driven member such that the driven member and crank arm rotate together. An axle is slidably mounted to the crank arm such that the axle is maintained substantially parallel to the rotational axis of the driven member as it slides from an inner point on the crank arm, to an outer point on the crank arm, and a bias element is arranged to exert a force on the axle toward the rotational axis of the driven member.