[TowerTalk] Rohn TB3 or TB4

[AB7R]

The thrust bearings at array solutions look very nice and have zerc fittings
on them.  Going to order one for my hg-70HD.

Greg
AB7R


-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]On Behalf Of john at kk9a.com
Sent: Friday, January 12, 2007 3:55 PM
To: TOWERTALK at contesting.com
Subject: [TowerTalk] Rohn TB3 or TB4


I bought a Rohn TB-3 four years ago and when I received it and turned it by
hand and it would often lock up.  I returned it and got a replacement, which
turned a little easier.  I installed the bearing on my Aruba tower and after
several months it started to bind.  The binding was only noticeable when
turning by hand as somehow the rotator was able to turn the mast.  I then
sprayed a little WD40 into the bearing and it turned easier, however I
quickly replaced the Rohn bearing with one made by Create.

John KK9A



To: towertalk at contesting.com
Subject: [TowerTalk] Rohn TB3 or TB4
From: "Roger Kissel"
Date: Thu, 11 Jan 2007 15:08:00 -0500
List-post: mailto:towertalk at contesting.com


So you're all saying that lubrication should not be used with a Rohn thrust
bearing ?

I just took down a tower that had not been used for quite a few years. It
had a Triband beam and a TB3. I thought I had hit the jackpot.

Until I tried to turn the bearing. It was locked up !

I disassembled everything and took it alll home. When I got the bearing into
the shop, I put it in the vise and tried to turn it. Still couldn't turn it.
So I removed the allen screw and removed the bearings so I could take the
races apart.

The balls, by the way, were not shiny. They had a matte finish. Once I got
the races apart, I could see why it would not turn.

First, the races are aluminum. Poor (No, BAD) engineering practice, IMO. The
balls, sitting in one place for years, wore into the aluminum race and the
AlO2 that had developed over the years, ground into the races. It also
ground into the steel balls, giving them their matte finish.

The outer race which is the main flange that bolts to the tower plate, was
worn into a multiple scallop shape. The balls sat in those scallops and
would not turn.

I don't know if lubrication would have made any difference in this case,
since the rotor had not turned for so long.

I would imagine that if the race had been filled completely (like we used to
do with wheel bearings - the roller bearings that we squeeeezed the grease
into) that dirt would not have gotten in.

For the time being, I have built back the bad races with TIG and am going to
remachine the grooves and use new balls and see if I can reuse the bearing.
If not, I'll put up a STEEL bearing.

I really think the loser is the Rohn engineers who produced the TB2, TB3 and
TB4.


Makes me really wonder why Rohn went bankrupt....


RoGrrr
KC8HZ

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