@Casper: Thanks for your answers too and specially the hint about the clutch. I never came to the idea that it basically works like a slipper. But it makes sense

He probably can adjust the preload accoridng to the grip level. Once it exeeds a certain torque it slips.
Can you actually buy this clutch in the states or is it commonly used over there ?
Regards
Florian
I know they are working on stuff.......