Originally Posted by
Duragrouch
OK, got it, yes, the balls are rotating the reverse of the spindle. But they're along for the ride with the spindle. Worst-case forces is if the balls start to seize up, and in that case, the cup will try to rotate in the same direction as the spindle, which would try to back out the cup, except, the precession forces, based on the rotating radial load and slack in the threads, wants to rotate the cup opposite the spindle direction, tightening it.
There another thread right now, suddenly spindle got tight; Lockring had loosened just enough that the cup promptly tightened on the bearings, due to precession.
Precession is the description of why things don't just line up, but it isn't an explanation of the forces involved: The spindle, balls and cup form an impossible gear train because the cup is not allowed to move at the rate the bearings are trying to turn it. If the spindle, bearings and cup were cogs, the spindle would be locked up. A sun and planetary gear system wouldn't be useful if the center input gear could turn without the outer ring turning in kind, and BB cups don't turn.
The reality is that the balls are smooth and they are not rolling on either the spindle or the race, they slipping to make it possible for the spindle to turn without the cup turning in kind. Those friction forces of the balls trying to roll but being forced to slip like a car tire on ice is what pushes the cup looser or tighter.
It is also a reminder why preload is foolish - the balls are already backslipping, and preload just increases that friction more.
I don't see why you think your illustrations help clarify anything, but I don't think you get what is actually happening in a bearing system.