[TowerTalk] aircraft bearing

[W0UN -- John Brosnahan]

At 11:41 PM 7/30/2005, you wrote:
>I'll go with John W0UN on this one.
>
>Been using a piece of lignum vitae (sp?) for years on a Telex 
>LP-1002 log periodic. last inspection indicates I'll only get around 
>another 50 years life out of it at the crazy rotation speed of 1 rpm!
>
>lignum vitae is what they used to make bowling balls out of back in 
>the old days...not sure what they use now.
>
>I'll bet a nice piece of mahagony would work just as well, its hard 
>and stable (won't warp).

Rohn used to supply a wood bearing for ham use.  Don't recall if it 
was OAK or something
else but it was adequate for many ham uses.

But I went with the UHMW just to see how long it would last.  Rush 
Drake used it in
Washington but then we all know there is no sun in Washington.  I'll 
climb my towers
the next time I am in CO to see what it looks like these days.  Been 
a couple of years
since I was up there.  In my case I mounted the UHMW on the BOTTOM of 
the top plate
so the plate itself provided a lot of the UV protection.  If you 
worry about the little bit of
exposed UHMW around the mast that is open to the sun in the hole in 
the top plate
you can always make a cover of rubber -- old inner tube or whatever.

If you end up using the UHMW to handle the vertical load as well, 
then the large
"washer" that sits on top of the UHMW to spread the weight over a 
larger area will
provide the UV protection needed.

--John   W0UN