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[TowerTalk] Re: Things I need

To: <>
Subject: [TowerTalk] Re: Things I need
From: (
Date: Mon, 24 Mar 1997 13:48:46 -0500 (EST)
In a message dated 97-03-24 12:36:52 EST, you write:

> Thanks for the information.  I will try to get some carbon steel schdule 80
>  masting here.  One of the weld shops here has a pretty good supplier.  As
>  far as where I was going to mount the rotor....about half way down the
>  section.  I gues you use some good old words and stick it in there.  Would
>  be nice to have it at the top where it wouldn't be such a hassle, but I
>  think that it might bode better for the rotor to have it lower.  I don't
>  know...I am just a shade tree mechanic here....but I was thinking about
>  way down the top section.
        Lower mounting does a couple of things.  It allows the longer mast to
act as a torsion bar to absorb some of the wind-induced torque.  Imagine how
much torque a 30 or 40 foot internal mast could absorb, thus relieving some
(most?) of the load from the rotator.

      Lower mounting also allows you to lower the center of gravity of your
mast/antenna system.  It also decreases the bending  moment on your rotator
(by having less mast sticking out the top); this may be a minor point.  On
the other hand, imagine a 20 foot mast system with 18 feet sticking out of
the tower with antennas attached with 2 feet of mast in the tower to the
rotator.  Talk about a BIG pry bar on the rotator!  More mast in the tower
decreases this effect.

     Having the rotator shelf in the direct vicinty of a guy attachment point
means that the wind torque that manifests itself at the rotator will be
transfered immediately to the guys with a minimum of intermediary twisting of
the tower.  That's non-engineering talk but I think you get the idea.

     Any other pluses?  Or minuses?  Further TowerTalkian input solicited.

73,  Steve  K7LXC


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