On 4/10/2014 5:45 PM, john@kk9a.com wrote:
The top bearing should hold the vertical load. I use the rotator bearing to
stabilize the mast vertically. Why do you need a second TB2US?
Depending on spacing and load arm, the top bearing can serve as a pivot
applying considerable lateral load to the rotator.
It is almost impossible to divide the vertical load equally, or even
nearly so. Too many variables to keep it that way if you could achieve
it initially.
As a rule of thumb, I use "the second, or lower bearing should be at
least twice the distance from the top bearing as the top antennas are
from the top bearing".
The bottom bearing should not be tight enough to hold vertical load.
Just close fitting enough to limit side motion. I use the bottom bearing
to hold the mast when removing the rotator.
Without the rotator and only the top bearing the lateral twisting moment
on the bearing can be enough to easily destroy the one bearing.
73
Roger (K8RI)
John KK9A
[TowerTalk] Thrust Bearing adjustment
from [Mike Fahmie] [Permanent Link][Original]
To: Tower Talk <towertalk@contesting.com>
Subject: [TowerTalk] Thrust Bearing adjustment
From: Mike Fahmie <wa6zty@yahoo.com>
Reply-to: Mike Fahmie <wa6zty@yahoo.com>
Date: Thu, 10 Apr 2014 13:46:43 -0700 (PDT)
I'm about to raise a 72' US Tower equipped with a pair of TB2US thrust
bearings
spaced about 3'. I'll be using a TailTwister2 Rotator. Is there a
procedure
for centering these components to preclude binding?
I doubt there is a way to make the two bearings share the vertical load, so
which one should I choose. I'm thinking that the top bearing should take
the
load and use the lower bearing to stabilize the mast laterally.
-Mike-
WA6ZTY
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