Vapaakytkin

Vapaakytkin, also known as a freewheel clutch or one-way clutch, is a mechanical device that allows rotation in one direction but prevents rotation in the opposite direction. It essentially acts like a ratchet mechanism, but with a continuous engagement when rotating in the allowed direction. When force is applied in the direction of free rotation, the internal components engage and transmit the torque. When the direction of force reverses, the internal components disengage, allowing the driven component to spin freely without affecting the driving component.

These devices are commonly found in bicycles, particularly in the rear wheel hub, allowing riders to coast without pedaling. In this application, pedaling forward engages the vapaakytkin, propelling the bicycle, while pedaling backward or stopping pedaling allows the wheel to continue rotating independently. Other applications include power tools, automatic transmissions in vehicles, and various industrial machinery where intermittent or unidirectional rotation is required. They can be designed with different mechanisms, such as roller clutches, sprag clutches, or pawl-and-ratchet systems. The primary function remains consistent: to enable rotation in one direction while blocking it in the other.