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Re: [TowerTalk] ab621

Subject: Re: [TowerTalk] ab621
From: jim Jarvis <>
Date: Sun, 23 Nov 2008 17:23:04 -0500
List-post: <">>
N3CW wrote:
      I notice on my AB-621 that as you crank up the mast, the full  
weight of
the mast sections, rotator, and antenna is taken up by the winch cable,
which loops around a pulley and comes down to attach to a trolley  
(where the
platform that lifts each mast section is).  The cable which supports  
all the
weight has a threaded compression fitting, and one nut holds the  
whole thing
together.  If this one nut would fail (strip out) while you are  
cranking up
the mast/antenna, it seems like the whole configuration would come  
down inside of the launcher base, at least for 6 feet until the mast hit
      My question is this - does anyone know what kind of margin of  
you have with the AB-621 design for this one very important nut? I'm
wondering since the mast originally was not designed to crank up 100  
--Ed, N3CW--


If you search the archives on this reflector, you'll find a reference  
to the AB621 manual.
That will take you to the specs, and testing procedures for the tower.

the tower IS designed to crank up 100 lbs.   It's a batallion  
microwave tower, and
the plan was to have a cross arm with two dishes topside.

I don't know the quantitative answer, but I suspect that your concern  
would be allayed
if you were to read the specs, and then calculate the force necessary  
to strip out
that nut you were concerned about.    If you were really worried, you  
could always
double nut the thing.

I've sold my 621, so don't have access to the info any longer.

As a practical matter, though, I had mine up at 100', with a 2 el 40  
and 8 el lpda,
with no problems (until the oak tree attacked it.)    Deadweight load  
on that winch
cable had to be 250-300 lbs.



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