That relys an awful lot on precision timing of a mechanical device Gary, if the timing fails via some unforseen event and the paw bounces once it may be enough to keep it bouncing as the load accelerates out of control. I personally wouldn't trust something like that. The only electric brakes I've ever seen are in 1/4 ton industrial chain hoists, those work via a clutch and a mechanical gear lock together. The clutch is there to keep the load from gaining any kind of momentum until it can catch. For lighter loads the mechanical lock often isn't even needed and you can simply rely on the clutch, depends whole on the situations and the minds of the maker.