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Re: [TowerTalk] Thrust Bearing adjustment

To: "Jim Thomson" <jim.thom@telus.net>, <towertalk@contesting.com>
Subject: Re: [TowerTalk] Thrust Bearing adjustment
From: "Jeff AC0C" <keepwalking188@ac0c.com>
Date: Thu, 10 Apr 2014 20:44:58 -0500
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
Being a tower rookie, I learned this lesson the hard way, needing to replace a rotor and no lower bearing.

Necessity being the mother of invention, it turns out that for a 25G tower and a 2" mast, you can use 3 2x4 to serve as a centering method. There is just enough space for each 2x4 to slip between the mast and the inside two tower leg verticals. With all 3 in place, the play is a fraction of an inch. In advance, I put a stop screw into the facing end of each one so they would not slip out. It's not very sexy but it works great. A pair of big-mouth Vice grip clamps were used to prevent mast rotation.

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- From: Jim Thomson
Sent: Thursday, April 10, 2014 8:22 PM
To: towertalk@contesting.com
Subject: [TowerTalk] Thrust Bearing adjustment


## 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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