What is a freewheel?

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.

An overdrive is sometimes mistakenly called a freewheel, but is otherwise unrelated.

Operating principles:

The inner and outer races are rotated relative to each other in one direction, while the other direction is not so torque transmission is possible

There are several types of freewheels exists:

• Roller type
• Sprag type

They can be classified based on operating principle:

• Overrunning clutch
• Indexing clutch
• Backstop

• Shaft diameter: 8 - 300 mm
• Torque: 1 - 1 700 000 Nm