>
I've got a US Towers TX-455 that I'm about to purchase a new M2 OR2800
for. I called US Towers and asked what they offer in the way of a
bearing plate to be situated just above the rotator. Apparently, they
/don't/ offer a bearing plate. Their plate that is designed for
rotators isn't meant to mount a bearing due to the way it's
manufactured. Their concern with using their rotator plate as a bearing
plate centers around the fact that the plate doesn't permanently attach
to the tower, but merely sits down inside of it, held in place by the
three horizontal members (rungs) that it rests against - thus making for
a situation where side loads placed on the plate could be transferred to
one of the three (or all three) of the rungs - possibly bending them.
> Next, I called M2 and asked what I should do to promote a long life and
prevent damage to their rotator with it mounted inside of TX-455 top
section. Their answer, "Just use a thrust bearing."
> The TX-455 top section is flat. That's where the thrust bearing
goes.... on the very top of the tower. Several inches below it is
another flat plate that's also welded into the tower. Between the top
plate and the plate down below it is a center tube that's welded between
them that the 2" mast will ride in.
> With a 21' long, 2" O.D. 1026 DOM tube projecting 16' out of the top
of
this tower - what possible protection could a thrust bearing at the very
top of the tower offer the rotator more than five feet down, inside the
tower? I'm concerned about with the side loads on the rotator head
created by wind forces on the mast and antennas above the fulcrum.
> Is my thinking wrong on this? Shouldn't I try to mitigate the side
thrust on the rotator head, just above it?
Traditional amateur thinking is that having a thrust bearing will
allow you to take some/all of the vertical weight off of the rotator. But the
rotator bearings want some weight to seat the bearings. The M2 Orion wants
ALL of the weight on the rotator. This is in the vertical plane.
But wind forces on the mast are mostly horizontal making a thrust
bearing marginally useful. I've installed arrays where there was no weight on
the rotator due to using a TB. Was that fatal for the rotator? Not really.
Your UST tower has a sleeve (kind of a mast bushing) on the top of
the tower where it actually handles the mast side-load from the wind so it
makes a thrust bearing redundant and not necessary. Save yourself the money
and skip the TB.
Cheers,
Steve K7LXC
TOWER TECH -
Professional tower services for amateurs
Cell: 206-890-4188
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|