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Freewheel mechanism Ratcheting freewheel mechanism (van Anden, 1869). In mechanical or automotive engineering, a freewheel or overrunning clutch is a device in a transmission that disengages the driveshaft from the driven shaft when the driven shaft rotates faster than the driveshaft.
The main advantage is that the driver does not need to leave the vehicle to connect the wheels to the axle. The disadvantage with this system is that most designs require the vehicle to move some distance (usually a whole wheel turn, often going backwards) after engaging the hubs in order for the hubs to engage or disengage.
A sprag clutch is a one-way freewheel clutch. It resembles a roller bearing but, instead of cylindrical rollers, non-revolving asymmetric figure-eight shaped sprags, or other elements allowing single direction rotation, are used. When the unit rotates in one direction the rollers slip or free-wheel, but when a torque is applied in the opposite ...
The Shimano Front Freewheel (FFS) was a proprietary bicycle drivetrain design of the 1970s that placed a freewheel between the pedal cranks and the front chainrings – enabling the rider to shift gears while coasting. [2] FFS rear freewheel is different than a standard freewheel because it's "stiff" with more friction than a normal rear freewheel.
A freewheel and freewheel hub A freehub (above) for use with a cassette and a threaded hub (below) for use with a freewheel. A freewheel (also known as a block) consists of either a single sprocket or a set of sprockets mounted on a body which contains an internal ratcheting mechanism and mounts on a threaded hub. Threaded rear hubs were ...
A slipper clutch (also known as a back-torque limiter) is a specialized clutch with an integrated freewheel mechanism, developed for performance-oriented motorcycles to mitigate the effects of engine braking when riders decelerate.
With the freewheel, a coasting engine could reduce its speed to idling, thus requiring only the small lubrication available from the closed, coasting, throttle. Freewheeling can also be used to help reduce high exhaust gas temperatures in two stroke models caused by prolonged use of the throttle at higher RPM.
A fan clutch is a thermostatic engine cooling fan that can freewheel at low temperatures when cooling is not needed, allowing the engine to warm up faster, relieving unnecessary load on the engine. As temperatures increase, the clutch engages so that the fan is driven by engine power and moves air to cool the engine.