I've seen this grease/no grease thread for years and never gave it much
thought. But, I now have to wonder why anyone would design a bearing with an
aluminum body/race ? The reason I say this is that I took down a tower several
years ago that had a TH6DXX on a TB3. The system had been idle for several
years with the antenna rocking back and forth the whole time. Even tho the
brake on HAM-M was set there's still some movement. As a result, the bearings
ground into the race and dug out pot holes to the point that the bearing would
not turn at all.
IMO, they should have designed in a grease zerk and recommended it be used.
When you cut or file aluminum it only takes a short while before it oxidizes.
Aluminum oxide is extremely hard (that's what they use for sandpaper) and when
the steel balls run over it, it breaks the oxide apart, giving you grinding
compound. During the idle period, the bearing ground itself to death. Had
there been grease in the race, it might have slowed down the self-death of the
So at this point the ROHN engineers and I are at odds. But I'm not a mechanical
engineer, nor am I a lubrication engineer, nor am I a metallurgist. (I only
play those on the internet, ya know....) Granted the bearing tolerances were
so sloppy that contaminants will not be of great significance and even tho it
turns so slowly, after what I saw with this one, I would not consider operating
it dry. Granted, many greases dry out over the years so something like a
synthetic grease should be used.
What I did, since the bearing was of no use/value in its condition, was to
disassemble it and welded up the chewed up races so I can recut the races in my
machine shop. If it works, I have a decent bearing. If it doesn't work then
I'll use a sealed steel bearing when I put up my next tower.
> Message: 2
> Date: Thu, 13 Oct 2011 13:42:39 -0500
> From: Bill Aycock <email@example.com>
> Subject: Re: [TowerTalk] Best Grease for Rotor bearings ?
> I just looked at the Rohn catalog page for the TB3 and TB4 and there is
> no note about Lubrication. This was the older Rohn catalog that Champion
> used to furnish. The bearings are in the accessory pages at the end of
> the 25G section.
> On 10/12/2011 10:26 PM, firstname.lastname@example.org wrote:
> > Doug has a question:
> > ----- Original Message -----
> > Would either of you gentlemen please provide for me the instructions from
> > Rohn that states that their TB-3 thrust bearings are to be run dry. I know
> > that they are sold dry. I am looking for facts from Rohn that say that
> > these bearings should not be lubricated. I am not interested in any
> > information except from Rohn.
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