In a message dated 5/17/2010 6:18:19 P.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> Hi TTers,
I got that Rohn 45 tilt-over down and home last week. In remarkably good
condition. Only thing I wondering about is the TB3 thrust bearing and how to
lubricate it. It turns freely but has a notable rumbling sound and feel to
it. I notice at the bottom of the inside shaft area where to mast passes
through, is a recessed Allan head fitting/plug. Would this be the place to
remove and squirt in some white grease? And then replace the plug?
Removal of the Allen screw allows you to remove the ball bearings and
then take the bearing apart.
This bearing should NOT be lubricated with anything. All that does is
give airborne grit and crud a place to attach to, thus accelerating the
failure of the bearing. The bearings are not sealed so it's easy for junk to
get into the bearings and races.
The TB-3 (and TB-4) are both aluminum races with steel ball bearings.
It is very common for older TB's to have the rumbling you describe since in
wind gusts, the steel bearings can get pounded into the softer aluminum
races. This means the bearing is on its last legs. I wouldn't reinstall it.
Well, if you were just going to use it as a bushing without tightening the 3
bolts, it'd last for years. The actual value of a thrust bearing is the
subject of some conjecture since most or all of the weight of a mast and
antenna array should be on the rotator.
Cheers,
Steve K7LXC
TOWER TECH
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