Wheels go in oposite directions as you go down the road. Yep conclusion edit incoming
I had a little think about this with my little bit of Newtons elbow thought I have left. The pulley not being keyed could be the key reason (see what i did there)
If the pulley spins it could drag the nut off if it wasnt, what it is.
If it was keyed to the shaft I maybe inclined to say it should be the other way round.
Fast running out of techy brain cells today.
J
My 3 words........
Spontaneous bolt loosening.
Another 2 words...
Case closed !!!!