[BrianG]

For the tension, there are spring-loaded screws, probably four in all. The springs are the red dots - remember, it's a cut-away view. The problem with this is you have to have the CB seperate from the hub to adjust the tension, then have to muscle it back in the CB. Then again, you generally don't want too much slip since it's really intended for drivetrain protection so there shouldn't be much adjustment. The screw part could be eliminated, but then there would be nothing to stop the pads from gripping harder at high rpm due to centrifugal force (same problem as with using clutch shoes, mentioned earlier). The springs provide the force, the screws provide the limit.

It's hard to make stuff in Excel (but much faster) so it might not be readily apparent.

This version looks much easier and cheaper to build.