There are four different types of freewheeling clutch, also known as overrunning clutches. They are all used to freewheel or overrun in one direction while maintaining the driving rotational force in a different direction.
One of the main characteristics of all freewheeling clutch occurs when the driven shaft rotates faster than the driving shaft. When this happens, an overrunning clutch will disconnect the driving shaft from the driven shaft. This makes such clutches ideal for use with heavy duty applications and when backstops and dual or one-way drives are required, as well as with multiple speed drives.
The usefulness of a freewheeling clutch makes them a popular choice for machinery used in industries such as mining, agriculture and metal processing.
Below we take a look at the four types of freewheeling clutch.
Roller Ramp Overrunning Clutch
Roller ramp freewheeling clutches consists of cylindrical rollers in the wedge-shaped area between the outer cylindrical surface and the inner flat surface. The clutch is engaged when friction is generated between these surfaces and the rollers, which become wedged when the flat inner surface rotates in the driving direction. The roller ramp overrunning clutch is known to have a long lasting design.
Typical applications for roller ramp clutches include agricultural machinery, pumps and compressors, and these and other types of clutches are available through industrial clutches supplier Yorkshire’s YB Components.
Sprag Overrunning Clutch
Sprag freewheeling clutches work similarly to roller ramp clutches with inner and outer cylindrical shapes, but instead of the uniform rollers they use figure 8-shaped sprags that only move in one direction. These clutches provide better torque but their radial space restrictions limit the bore size.
A sprag clutch can be used in some automatic gearboxes to enable the transmission to change gears smoothly under load. Other applications include the starting turbine of a jet engine, and in helicopters where they help transfer power from the engine to the main rotor.
Wrap Spring Freewheeling Clutch
Wrap spring clutches feature a helical spring that tightens around a cylindrical sleeve to transmit torque in a single direction. They are usually found in low speed or light load operations.
Wedge Freewheeling Clutches
Wedge clutches provide high overrunning speed and torques and are usually a cost-effective alternative to other varieties of freewheeling clutch. They don’t use a cylinder-shaped outer housing but instead have a flat surface fitted with compact springs. This design tweak gives the wedge clutch a larger surface with which to increase torque and makes them very easy to look after and repair.
Source: YB Components