Freiläufe

Freiläufe are mechanical components or arrangements that permit rotation in one direction while preventing rotation in the opposite direction. They are used to decouple a driven component from its driver when power is interrupted, to allow coast­ing, and to protect against back-driving. Freiläufe can be built as freewheel mechanisms, one-way clutches, or overrunning couplings. They appear in a variety of systems, including bicycles, machinery, and automotive or industrial equipment.

In bicycles, Freilauf refers to the freewheel or freehub system that allows the rear wheel to rotate independently of the pedals when the rider stops pushing, enabling coasting. Older designs used a separate freewheel in the hub, while modern setups typically employ a freehub body with pawls inside that transmit torque only when pedaling forward. This arrangement prevents the pedals from turning while the bike coasts downhill.

In other machines, one-way clutches or freewheel devices are used to prevent back-driving of a drive shaft, to allow idle rotation, or to protect gears and bearings. Common types include sprag-type, roller-type, and pawl-type one-way clutches. In automotive and industrial applications, Freiläufe can decouple a driven shaft during overrunning, such as in starter motors to prevent reverse rotation, or in conveyors and power tools to permit free rotation when the drive is stopped. The choice of device depends on load direction, speed, reliability, and maintenance requirements.