I suppose every installation is different. Even if I completely loosened the
bolts on the bearing and on the rotator, my mast is confined inside the
rotator's bracket and it could not drop. Perhaps if you had a rotator like
Telrex, the mast could slide all the way through.
John KK9A
Tim Duffy k3lr wrote:
Hello Dave,
Great advice.
I use this clamp on top of my bearings:
https://www.dxengineering.com/parts/dxe-sds-300p
Along with the additional backing plate:
https://www.dxengineering.com/parts/dxe-sdsbp-300
This clamp when properly tightened - does not slip
73
Tim K3LR
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of
Leeson
Sent: Sunday, June 22, 2025 12:56 PM
To: Tom Hellem; towertalk
Subject: Re: [TowerTalk] Thrust Bearing Concerns
Two thoughts: I can't find the reference just now, but I recall an awful
years-ago tower accident in which a ham was injured and trapped on his
tower when the thrust bearing bolts broke and the loaded mast fell onto
his hands. So I'd be concerned about any thrust bearing setup that
relied only on the clamping bolts.
I have had good luck with adding one or more clamps on the mast just
above the bearing, typically heavy U-bolts or machined bolted clamps.
There may be other more formal clamps that can perform this function.
Once I loaned my tower to some visiting hams to put a temporary contest
Yagi on my mast, and when they left they didn't know to replace the
clamps; the swooshing noise of the mast slipping down ended with the
boom of my own antenna hitting me in the head and shoulder. Luckily it
was cold and I had a thick hat on, or it could have been very much
worse. So if you use this approach, be sure to check that the clamping
is tight before you do anything else on the tower. I use two, just for
the extra redundant reliability.
Caution and plenty of your own research is strongly recommended.
Dave, W6NL/HC8L
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