In a message dated 1/11/2007 2:19:46 P.M. Pacific Standard Time,
>> Steve, K7LXC@aol.com, Wrote:
>> I found this on ebay. It's a Rohn thrust bearing and it says that it's
"FRESHLY PACKED WITH WHITE LITHIUM GREASE". Gentlemen, these bearings are
supposed to be lubricated. Do not buy this unless you unpack the grease.
Don't be a loser like this guy.
> So you're all saying that lubrication should not be used with a Rohn
Yessireebob. It's designed to be unlubricated.
> 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
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
> The balls, by the way, were not shiny. They had a matte finish. Once I
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,
worn into a multiple scallop shape. The balls sat in those scallops and
would not turn.
Yes. That's what happens when it sits in one spot. The wind force causes
the steel bearings to hammer into the softer races.
> I don't know if lubrication would have made any difference in this case,
since the rotor had not turned for so long.
It wouldn't have because the races would still have gotten hammered.
> I would imagine that if the race had been filled completely (like we used
do with wheel bearings - the roller bearings that we squeeeezed the grease
into) that dirt would not have gotten in.
Au contraire. Actually the grease attracts dirt, girt, pollution
particulates, etc. so it would actually accelerate the wear with all that junk
it. The problem you described was due to it being in the same spot for a long
> For the time being, I have built back the bad races with TIG and am going
remachine the grooves and use new balls and see if I can reuse the bearing.
If not, I'll put up a STEEL bearing.
Like what? The machine shop type pillow blocks are not suited for outdoor
use and they only use a single small Allen screw to pin the mast.
> I really think the loser is the Rohn engineers who produced the TB2, TB3
Well, anything that sits outside for a long period of time is going to have
problems. It's an okay design that does have its limitations.
> Makes me really wonder why Rohn went bankrupt....
They were a victim of over-expansion during the big telecommunications
build-out in the 90's and got caught being overextended when everyone stopped
building tower sites.
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