Post
by Rich Stephens » Tue Feb 17, 2004 2:05 am
I know we were talking about bearings and spacers/washers months ago and I promised to do some drawings that would simplify the discussion of preload considerations and running bearings as radial pairs and what not. Rockin' Ron of California Bearing has mentioned on another forum that he will be creating some soon.
Today I read the following, from George Powell:
"Bearings are very precision parts, ground to tenths of a thousandth inch, but the truck axles they go on vary greatly in diameter, and more importantly, the truck casting is not usually square to the axle, nor is the nut always square to the axle. In order to use spacers and tighten up the axle nut, everything has to be perpendicular to the axle. If the casting, spacer or nut are not perpendicular to the axle, then when you tighten the nut, the inner races of the bearings will be unevenly loaded, and the clearance between the bearing and axle will allow a slight cocking of the bearing race, making the inner and outer races no longer co-axial. Ever tighten up a wheel nut and have the wheel not spin free, or get stuck in one place…this is the result of poorly made trucks or spacers (often both).
"In reality, most trucks are not made precisely enough to allow you to tighten up the nut with spacers in place, so skaters have merely adapted by backing off their nuts a little (the proverbial 1/4 turn) to allow the wheel to spin freely. This solves the problem of free spin, but when the skater turns, more friction is created than should be by the cocking that will happen when the bearings are side loaded."
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more motivation to send our trucks to the machine shop. Do any of you go to the extreme of making the inner edge of the axle nut perpendicular!?!