The pitting (technically brinelling) of the bearing is typical of ANY ball or
roller bearing with intermittent or stationary use, with even vibration!
(Classic study of auto wheel bearing and rail shipping if you study vibration
failure)
You either WAY over design, or use a solid bearing. Classic in the old days was
bronze, but you had lubrication issues.
Today, the answer is...plastic
Filled nylons, filled acetyl, filled Teflon (stop cold flow issues if high
load), or if the budget is there, torlon or vespel. The latter two are so
expensive, once you get past prototype, it pays to have custom molds made, and
cast the smallest part you can to finished shape, but I'm fairly sure a disk
say one inch wide, with a 6-8 id (aka a big washer) 1/8 thick would hold a
large rotating tower with no problems
--
73 de KG2V
Charlie
> On Jul 14, 2018, at 12:53 PM, Kenneth Goodwin <krgoodwin@comcast.net> wrote:
>
> The T2X brake wedge is a lousy scheme. It allows the antenna to
> move/oscillate a total of 7 degrees in the wind which will pit most thrust
> bearings unless you park it in a different location every so often.
> Pointing accuracy is +/- 7 degrees 3 sigma. My current antenna is frozen
> since the rotator can't overcome the pits in the Rohn TB3 thrust bearing
> which means I didn't use the rotator enough. Hurricane Ike fractured my
> brake wedge although it continued to hold the antenna. I only keep my T2X
> because it continues to work after 30 years which must be taken as a great
> positive even if I hate the brake wedge!! Someday I will have to replace
> the thrust bearings in the tower whereas the design requirement was that
> only the rotator would have to be replaced over the tower's lifetime. Like
> NASA, the only problems I have are the ones I didn't think about. Ken K5RG
>
>
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