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Re: [TowerTalk] Thrust bearing shot

To: "K8RI on Tower talk" <>,<>
Subject: Re: [TowerTalk] Thrust bearing shot
Date: Sat, 13 May 2006 03:46:23 +0000
List-post: <>

     I used a self-centering industrial bearing at the top of my tower, similar 
to: .  I lube 
it once each year with marine grease.  It cost about what a TB-3 would cost 
($70 in 2001.)  Because it's self-centering, it will accommodate up to a +/- 2 
degree misalignment of the mast and bearing centerlines.  FWIW.

73 de
Gene Smar  AD3F

 -------------- Original message ----------------------
From: "K8RI on Tower talk" <>
> I thought I'd pass on some information.
> It seems like even with care planning for problems when pushing the limits 
> the problems turn up where we don't expect them.
> I'm running a 97 foot ROHN 45G.  The tribander is supported just above the 
> top of the tower on a 24' long, 2" structural steel tube with 1/4 wall over 
> an 1 1/2 tube  with 1/4 inch wall made up of two sections totaling about 44 
> feet. So the center section has essentially a 1/2 inch wall, supports the 
> TH-5 at 100' while the 7L C3i 6 meter beam at 115' is mounted on the 1 1/2 
> pipe right at the top of the 2".  The 144/440 array is 12 feet above the 
> 6-meter antenna at roughly 127'.
> The mast is supported by a TB-3 at the top of the tower with a second TB-3 
> about 12 feet below the top of the tower that just keeps the mast centered 
> with the rotator (PST-61) mounted at 17' below the top of the tower.
> I knew the leverage of the tall mast above the top of the tower would create 
> some pretty strong forces at the top of the tower, but after about 4 years 
> with lots of severe winds up here, the races in the TB-3 have worn to the 
> point where the upper race is setting right down on the washers for the 
> mounting bolts.  This is causing the bearing to bind to the point the PST-61 
> is unable to turn the mast.
> It appears as if I'm going to need to replace the upper bearing with a 
> pillow block arrangement of some sort with a fairly close fit.  If it 
> weren't for the massive side forces created by the leverage I'd use oil 
> soaked hard wood, but I think I'm going to need to get a split block of 
> steel or Aluminum machined to fit which will give a large surface area to 
> support the side forces without undue wear. I sure could use that milling 
> machine I was going to purchase before the market tanked back around the 
> turn of the century.
> And the day before I was going to order some LMR-600 and fittings for the 
> pigtails the price went up. <sheesh>
> Roger Halstead (K8RI and ARRL 40 year Life Member)
> N833R - World's oldest Debonair CD-2
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