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[TowerTalk] Thrust Bearing adjustment

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Subject: [TowerTalk] Thrust Bearing adjustment
From: "Jim Thomson" <jim.thom@telus.net>
Date: Thu, 10 Apr 2014 18:22:42 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
##  I forgot to add that the lower bearing comes into play when mast is raised 
a bit..and rotor  is out.   At that point, I use the locking ring on the lower 
bearing.  I also use a spare  OR-2800 mast clamp and clamp around the chromolly 
mast.  This ensures the weight is on the lower bearing.   Of course b4 u raise 
the mast a foot, the top bearings ecentric collar  must be loosened..... then  
retightened after mast goes up 1 foot. 

I would not recommend  not using the lower bearing at all....and only relying 
on the gaping hole in the lower bearing plate.  In most cases its too much 
slop.   Some have also used a sheet of .5 to 1.0 inch thick  UHMW  with a 2 or 
3 inch hole in it.   Hole is bige enough to not bind... but still allows to 
restarin the mast in the lateral direction.   Then u can still use a u clamp or 
spare or-2800 mast clamp, dx eng super clamp etc.. on the hb uhmw bearing...to 
take the weight.... while doing rotor repairs. 

Jim  VE7RF 





Jim is right on the money.  The second bearing in the middle is loose all the 
time until you need it to hold the bottom of the mast after raising the mast 
off the rotator for a rotator fix.

When I put in my Tri-Ex LM-470 I took the existing rotator plate and put it 
inside my Duplicator™ machine.  After inserting 50 cents and pressing the start 
button I had an exact duplicate.  Both rotator plates went into the tower, the 
lower one for the rotator (about 3-4' down) and the second one between the top 
and the rotator.  I built a mast raising fixture/winch on the second rotator 
plate to raise and lower the mast on the tower and for future rotator service.  
It works great!  Rather than using a bearing on that plate, I used four small 
pieces of HDPE plastic with radiused ends to match the diameter of the mast, 
used as sliders.  After the install was complete the raising fixture/winch was 
removed along with the plastic sliders...now it is just an empty plate with a 
large hole in the middle of it.

The important thing here is this has to be considered at the beginning of the 
project!  You can't get the second rotor plate in there once everything is in 
place.  (Unless you have a crane come in and hold up the entire antenna array 
while you put the second plate in there.)

Chris
KF7P







On Apr 10, 2014, at 17:40 , Jim Thomson wrote:

Date: Thu, 10 Apr 2014 13:46:43 -0700 (PDT)
From: Mike Fahmie <wa6zty@yahoo.com>
To: Tower Talk <towertalk@contesting.com>
Subject: [TowerTalk] Thrust Bearing adjustment

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

##  DON’T  use the set screws in the 2nd ..lower  TB2US.   I use two of the 
same bearings on my UST-HDX-689.   Lower bearing is 4 foot down from the top.   
PP rotor is 6 foot down from the very top.   2 foot between
lower bearing and rotor.    The tb2us uses an eliptical locking ring.   It will 
either lock CW..or CCW.    Just make sure u know which way it went on.   A 
small recessed partial hole on the locking collare is whacked with a drift 
punch..to lock the ring.

##  so leave the bottom bearing loose....so it only takes the lateral 
load..that’s it.    You can only ever line up 2 things...not 3.   So with the 2 
bearings +  rotor.... it becomes the top bearing and rotor...never the middle
bearing.    And I sure as hell would not rely on that top double plate and 
cylinder  on the UST towers to take all the load...esp when rotor removed..mast 
elevated a bit...and only the top bearing used.  Not with
a 20 ft mast.... with  14 ft above the tower..and 6 foot into the tower.     
Which becomes   15 ft above and 5 ft below..when rotor is removed.   The double 
plate at  the top of the tower and cylinder has a set screw..used to lock the 
mast  when rotor is removed.   I would supplement that   with some temp u bolts 
on the mast +  angle steel..so the mast  doesn’t rotate in a high wind with 
rotor removed.

Jim  VE7RF
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