> Chris: Rule of thumb is 1/3 of the mast inside the tower...it 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
> Good luck and do it all safely. 73 bob de w9ge
> Christopher J Galbraith wrote:
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