tok-tokkie wrote: Hopefully you will regret what you posted:
On a F1 in Schools track of 20m with 30mm diam wheels the wheels turn 212 as the car traverses the track.
Typically they have 2mm axles with a 6x2 bearing:
d1 = 2mm d2=6mm ball = 0.8mm ID of outer race = 4.8mm OD of inner race = 3.2mm
Let us approximate what happens by assuming that the balls roll without slipping on both the inner and outer races.
If the bearing is mounted in the wheel and the axle is rigid in the body the then each rev of the bearing outer shell will drive the balls π*4.8 = 15mm
If the wheel is rigidly mounted on the axle which turns the inner race of the bearing which is mounted in the body the balls will be driven π*3.2 = 10mm
The balls run 50% further when the outer race rotates.
If the balls don’t slip then in the first case each ball will have run 15 mm along the inner race taking it 1.5 revs. In the second case the balls run 10mm along the inside of the outer race taking them just 240 degrees.
xpensive wrote:Right, let's try it this way then;
You mean that the friction of the bearing will be different if you spin the inner or the outer race, everything else equal?
Mounting the bearing in the wheel with the axle fixed in the body makes the balls run much faster compared to bearing in the body with rotating axle. 1 rev of the wheel makes the balls travel much further if the outer race turns as against the inner race. In your application you are looking for minute reductions in resistance.
I suggest that your formula is a first approximation of the truth. Bear in mind that the certainty of the data is pretty suspect so real precision is not required of the formula. I still think what I suggest is valid from a fundamental analysis point of view.
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