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Re: [TowerTalk] Mast and Thrust Bearing questions

To: "towertalk" <>
Subject: Re: [TowerTalk] Mast and Thrust Bearing questions
From: "K8RI on Tower talk" <>
Date: Fri, 7 Jul 2006 22:18:57 -0400
List-post: <>

> Chris:  Rule of thumb is 1/3 of the mast inside the is a rule
> you should follow.  Rohn TB3 thrust bearings will last a very long time
> if you DONOT lubricate them.  If you do, then expect failure.  They are

Mine lasted about 5 years and it's completely shot. OTOH it was beat to 
death from having a lot of antennas well above it.  When the antenna work is 
done  and the TB-3 replaced (with another TB-3) the top arrays are not going 
back up. Just the tri-bander and the 7L 6-meter Yagi.

> designed to run dry and unless you rotate the beams constantly ie 24
> hours a day every day then it should last you a lifetime.  It is a good
> idea to put a boot on the mast to keep water out of the bearing....look
> for a rubber collar in the plumbing section.  If you don't have ice
> don't worry about it.
> A second lower thrust bearing is a good idea if you ever need to pull
> the rotator.  It need not be a thrust bearing tho. You want to
> eliiminate side movement is all.  If you use a second TB3 then do not
> tighten the capture nuts except when you are lifting the mast to pull
> the rotator.  It is almost impossible to get two thrust bearings aligned
> such that there is no twist.  Leaving the lower one loose keeps lots of
> trouble from happening.
> A second rotator plate with the mast running through the hole and a
> piece of oak with a hole drilled about 1/8 inch larger than the mast and
> bolted to the shelf will do the trick for far less money.  When you need

That's a good idea. The only things I'd do differently would be to soak the 
Oak in hot oil  for a few hours and to make the hole a "slip fit".  What'd 
really work nice would be to do it in a "pressure cooker"  that could be 
sealed off while it was cooling. This would create a vacuum as it cooled and 
drive the oil deeper into the Oak when the air was let in.  OTOH if you have 
a wife this might be better done in secret, but she still might wonder why 
things out of the cooker are now tasting strange.

I belive Ash is another good wood for bearings.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
> to pull the rotator just put a U bolt and saddle on the mast and resting
> on the top of the oak to keep it from slipping down while the rotator is
> out.
> Good luck and do it all safely.  73 bob de w9ge
> Christopher J Galbraith wrote:
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