[TowerTalk] Which Thrust Bearing to Use

[charlie at thegallos.com]

<snip>
>   Aluminum is  22 ppm/degree C
>   Steel is 12
>
> UHMW PE is about 100
<snip>
> SO let's take an example of a 2" diameter mast.  going from -40C to 60C
> is 100 degrees, and probably wider than the range most ham towers will
> see.  So that's a change in diameter of, worst case 100*100 ppm or 1%
>
> Your 2" hole that just clears at -40 will be 2.02" at +60C.  I don't
> think you're going to have a big problem with that 10 mil extra clearance.
>
> If you have a 20 foot mast sticking up above the top, and 5 feet in the
> tower, that 0.02" slop will turn into 0.1" at the very top of the mast.

Don't forget that your MAST is going to expand 12*100 ppm too, so it'll be
a bit less than that

Nylatron 66 is at 80ppm, go with MD grade it is 50ppm