[TowerTalk] Thrust Bearing adjustment

[Jim Thomson]

##  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 at yahoo.com>
To: Tower Talk <towertalk at 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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