A crank transmission having a crankshaft for connection to at least one foot or hand crank and at least one gear wheel driven by means of the crankshaft (5) is proposed. A coupling unit is provided between the crankshaft and the gear wheel. Under load, the coupling unit has at least temporarily an angular offset between a crank-side receiving region and an output region connected to the gear wheel for receiving and outputting the torque generated via the crank.

A ride-along vehicle may include a spring/chain guard that covers a spring and chain assembly and provides an attachment point for the spring. The guard may have a narrow portion that covers and helps retain the chain on a sprocket as well as a wider portion that covers the spring. In another embodiment, the spring can be connected to a fulcrum that has a chain retention pully, gear, guide, or wheel that keeps the chain tight in loop to improve the pump-action operation of the vehicle. An improved pumper arm and steering mechanism may include a pivot joint that is provided by rods, pins, or bolts attached to opposite sides of the pumper arm. The universal joint between the steering arm and the pumper arm can be aligned with the center of the pivot point to prevent rocking of the steering arm as the pumper arm is actuated.

A ride-along vehicle may include a spring/chain guard that covers a spring and chain assembly and provides an attachment point for the spring. The guard may have a narrow portion that covers and helps retain the chain on a sprocket as well as a wider portion that covers the spring. In another embodiment, the spring can be connected to a fulcrum that has a chain retention pully, gear, guide, or wheel that keeps the chain tight in loop to improve the pump-action operation of the vehicle. An improved pumper arm and steering mechanism may include a pivot joint that is provided by rods, pins, or bolts attached to opposite sides of the pumper arm. The universal joint between the steering arm and the pumper arm can be aligned with the center of the pivot point to prevent rocking of the steering arm as the pumper arm is actuated.

Disclosed is a rotation transmission mechanism including: an internal rotation member inserted by a crankshaft of a bicycle; and an external rotation member configured on the internal rotation member. The internal rotation member includes: an internal rotation member body. The external rotation member includes: a circular ring part configured at an outer side of the outer circumferential convex parts; and inner circumferential convex parts protruding to an inner circumferential side of the circular ring part and configured alternately with the outer circumferential convex parts. Elastic deformation parts are configured between the outer circumferential convex parts and the inner circumferential convex parts on a rotation direction side of the advancing outer circumferential convex parts. The outer circumferential convex parts are formed in such a manner that a surface on the rotation direction side is greater than a surface on an opposite side of the rotation direction.

A crank transmission having a crankshaft for connection to at least one foot or hand crank and at least one gear wheel driven by means of the crankshaft (5) is proposed. A coupling unit is provided between the crankshaft and the gear wheel. Under load, the coupling unit has at least temporarily an angular offset between a crank-side receiving region and an output region connected to the gear wheel for receiving and outputting the torque generated via the crank.