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Re: [TowerTalk] Crank up tower bracing rubbing against cable

To: "SPWoo" <>
Subject: Re: [TowerTalk] Crank up tower bracing rubbing against cable
From: "Rick Karlquist" <>
Date: Thu, 18 Oct 2012 10:18:10 -0700
List-post: <">>
SPWoo wrote:
> Hi All,
> I've discovered that my less than a year old TX-472 tower has three places
> where the steel cable is rubbing against the tower.  Attached below is a
> link to some photos of the problem.  In one spot the interference has worn
> away a lot of metal and it caused some cable wear.  I was wondering if
> anyone has experienced this and what I could do to remedy it.  I've sent
> the photos to US Tower and I'm still waiting for their response.  I crank
> my tower down every day and sometimes under light wind condition.  I don't
> know if wind has anything to do with it.  Thank you and very 73.
> Best Regards,
> Jonathan Woo, W6GX
> (970) 646-1711
> _______________________________________________

I ran into this problem on my HDX-5106.  When raising it past about
70 feet, I would start to get vibrations.  If I backed it down a few
inches and restarted it would be fine for 5 or 10 feet and then the
vibrations would start up.  Bottom line is that a cable had been
wearing on a brace and the groove had gotten deep enough (about
1/8 inch) that the cable could catch on it.  I wouldn't be surprised
if the tower was just made wrong and it didn't matter until the
groove got worn.  It didn't seem to bother the cable; it just made
it shiny.

The brace in question was an "X" brace made of 1 inch solid rods
and was pushed in.  The inner sections prevented me from pushing
it out by coming in from the other side.  Instead, I built a
jig consisting of a 4 inch I-beam suspended about a foot away from the
tower face.  I got the I-beam at a metal surplus store in Redwoood
City, CA.  One side of it was braced against the tower rails
by a piece of 2 inch water pipe with a flanges on the ends.
One flange went to the beam and the other was screwed to a wood
block.  The wood block had a saddle machined into it to fit the
rail; I used a hole saw to make a round groove.  The other side
of the beam had a 20 ton bottle jack between the tower and the
beam.  I also had a wooden saddle on the bottom of the jack.
A chain went around the beam and then around the brace.  It took
several months to invent this fixture and fabricate it.  It
really was quite a non trivial mechanical project.   Amazingly,
it worked perfectly the first and only time I used it.  I was
able to pull the brace out exactly enough to just clear the cable.
The bottle jack allows a precision control of lift.
The brace happened to be in a place where it wouldn't have
interfered with anything if it was pulled out too far.  But it
was nice to know that I had really good control, since the
fixture does not work in "reverse" and the brace was too big
to whack with a sledge hammer to push it back in.  After this
fix, the tower worked perfectly again.  In 20 20 hindsight, I
realized that it had always made scary popping noises that I
thought were "normal" before doing the fix.  I had Skip replace
the cables just because the tower was 15 years old, so in case
the rubbing damaged them, it wouldn't be a problem.  I don't
think the cables were in any immediate danger of failing, but
as the saying goes, it is better to replace them too soon rather
than too late.  I'm not worried about a 1/8 inch nick in a 1 inch

Rick N6RK


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