Do centrifugal clutches work in both directions?

[Stormer]

TL;DR Summary

Will a centrifugal clutch work in the reverse direction, or will it loose almost all of the torque as compared to when it is driven in the correct direction?

As seen by the image below a centrifugal clutch has a pin/hinge in one end of each shoe arm and dependent on the angle of the shoe arm in the fully extended position that will create a wedging action to further increase the friction against the drum beyond the centrifugal force alone. Kind of like the wedging action of the sprags in a sprag clutch. And this wedging action will not happen if it rotates in the other direction, then you will only have the centrifugal force pushing out and creating the friction against the drum. But how much of the friction is caused by the centrifugal force compared to the wedging action? Will this kind of clutch almost not work at all if it is driven in the reverse direction?

 

[jrmichler]

The particular type of centrifugal clutch shown in the OP is designed to transmit torque in one direction.

But how much of the friction is caused by the centrifugal force compared to the wedging action?

That depends on the location of the pivots relative to the drum inner face. You can see this relationship better if you make a free body diagram (FBD) of one pivot arm.

 

[Baluncore]

Will this kind of clutch almost not work at all if it is driven in the reverse direction?

In general, centrifugal clutches do work in both directions.
The clutch shown will transfer more torque in one direction than in the other, because friction between the cams and the drum multiplies the contact pressure in one direction while reducing it in the other.

Depending on the cam angle selected, the centrifugal clutch may rapidly lock up in one direction, while always slipping in the other.
The critical cam angle that determines if it will grab and lock like a sprag, or smoothly engage like a clutch, will probably be the arctangent of the friction coefficient.

 

[jack action]

The keywords you are looking for are "self-energizing" and "self-locking". This is also the principle behind drum brakes which use the "self-energizing" portion to create a power brake assist for big machinery. The brake literally "self-actuates" itself to a point where it could "self-lock" if it is designed to do so (a safety brake for an out-of-control spinning shaft, for example). Here's a detailed lecture about vehicle drum brake design (and how complicated it can get):

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