Explain the working of freewheel unit.

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written 7.7 years ago by

teamques10 ★ 64k

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.
When a vehicle going downhill or any situation where the driver takes his or her foot off the accelerator pedal, closing the throttle; the wheels want to drive the engine, possibly at a higher RPM.
To avoid this from happening we use a freewheel unit which disengages the driven shaft from the driveshaft.
It consists of an outer shell, pinion and collar assembly.
The outer shell has five notches containing five steel rollers fitted in it.
The notches are smaller at one end.

When the drive shaft starts to rotate, the rollers roll into the smaller end of the notch jamming between the shell and the pinion collar.
This forces the pinion to turn and the power is transmitted to the driven shaft.
However when the driven shaft starts rotating at the higher RPM, it drives the shell faster than the shell and armature.
As a result, rollers roll back to the larger end of the notch allowing collar to spin faster than shell armature.
Thus it prevents driven shaft from driving the driveshaft.

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