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
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
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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