[TowerTalk] Mast and Thrust Bearing questions

[David Robbins K1TTT]

I have had 2 tb-3's at 150' above peru mass for 22 years without touching
them.  At least 4 others also up for periods from 20 to 7 years, never a
failure here.  Never a drop of lube.


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of K8RI on Tower talk
> Sent: Saturday, July 08, 2006 02:19
> To: towertalk
> Subject: Re: [TowerTalk] Mast and Thrust Bearing questions
> 
> 
> 
> 
> > 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
> www.rogerhalstead.com
> > 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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