Deafcat said:There are actually two one-way clutches in the Ultra motor, a three-pawl freewheel for pedal input, and a one-way roller clutch or sprag clutch for the chainring output shaft. I've heard of that output clutch wearing or failing due to too large of a chainring and bad riding (too high of momentary torque loads), failure of the pedal freewheel only possible from too much pedal load as mentioned.
I've yet to damage either of them, though I'd like to replace the pedal freewheel with a sprag roller clutch to get rid of the noise... Onyx hubs on the bike so the only freewheel noise comes from motor. Maybe something I will re-engineer on next disassembly, worth it to have the parts drawn up anyway for community reference.
I've been thinking of retrofitting a sprag in replacement of the freewheel - I'll be interested in assessing the feasibility of doing that - let's collaborate on that.