It is composed of three parts:
- The inner housing which is fixed to the hub.
- The outer housing where the sprockets to be installed.
- The mechanism between the outer and inner housing.
For the mechanism, two different constructions may be used. The most common is the ratchet.
The inner and outer casings are beared with a Cupconus-bearing so that the two housings can rotate freely relative to each other.
Between the two rows of balls, the outer housing is provided with teeth and the inner house of two pawls.
At the moment that the outer housing will turn faster than the inner house, the pawls engage the outer housing and thus form a fixed connection between the outer and inner housing.
At the moment that the outer housing rotates more slowly than the inner housing , the teeth drag on the two pawls and the outer housing can rotate freely about the inner housing. When freewheeling you can hear the ticking of the two pawls.
Shimano has a freewheel (Silent clutch hub, literally silent coupling) with cylindrical paddles similar to those found in some back-pedaling brakes (fig. 62).
The cylindrical pawls are pressed between the outer and inner housing, at the moment that the outer housing where the chain wheels sit on it will rotate faster.
They come loose again as the inner housing, which is connected to the hub, is running faster.
The advantage of this construction is that the freewheel is silent in the freewheel mode. The hub is intended primarily for recreational use.
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