Originally Posted by
Kontact
The bearings aren't static, but there is simply no way that anything round can strictly roll when the spindle race diameter is different than the cup race diameter. Something has to slip, as you can clearly see in the gif I posted.
And really, how can you read about "excessive skidding" without wondering why there would be any skidding? That skidding is what has to happen for the reasons I stated.
Bearing preload makes sense when the bearing is going to support thousands of pounds on the axle, heat up greatly or have large load variations. None of which apply to bikes. You have all the information necessary, but keep coming to the wrong conclusions. And you didn't even understand the bearings you are preloading.
I posted at 10am. Apparently you are equally good with time conversions.
The bearing balls rotate. At the outer periphery, i.e., the outer race or cup, they roll with a surface movement at a given rate. Now transfer that same ball rotation rate to the bearing inner periphery, i.e., the inner race or spindle; You will have the same surface rate, no slipping, however because the inner race is smaller diameter, it will have a *higher rotational speed*, revolutions, than the speed differential at the outer race. If, for example, the inner race contact diameter is 1/2 the outer race contact diameter, the inner race rotational speed with be 2X the speed differential compared to between the balls and the outer race.
The Nuvinci/Enviolo variable speed hub uses this principle by varying the contact diameter to vary the speed ratio, with no ball slippage at any of the contact points. It is, in effect, a variable race ball bearing.