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[TowerTalk] An Engineering Question

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Subject: [TowerTalk] An Engineering Question
From: n7mb@primenet.com (Michael Bill)
Date: Tue, 27 May 1997 16:31:00 -0700 (MST)
Dave:

Actual experience in short guy wire distances... from my old QTH in Central
Illinois... I had 100' of Rohn 25G with a 5 el 20m beam (40')boom and a
6 el 15m above that.  the two guy wire were out only 45', the other at 60'.
This tower was up for 3 years in some VERY heavy ice storms, but held up
okay.  Now I did have them guyed 4 times (25,50,75, 100;) with the 1/4 EHS
with some large concrete pads, but it worked very well... All guy wires went
to single guy anchors...

for what it's worth..

73 de Mike/ N7MB

At 04:42 PM 5/27/97 -0400, David Clemons wrote:
>Hi,
>
>        I have a question concerning guy wire anchor placement.  I have
>two towers (one is 83 feet of Rohn 25 with a Hygain 155BA and 105BA, the
>other is 99 feet of Rohn 45 with Cushcraft 204-CD and 402-CD.)  A recent
>edition of the ARRL handbook says that the anchor distance should be
>between 60% and 80% of the tower height.  I have two anchors on each leg,
>with the lower two sets of guys on the inside anchor and the highest guy
>alone on the outside anchor.
>
>        Now the problem - the 13 acres of property behind me was bought
>last year and the new owners are putting up horse corrals for their
>boarding/training business.  We recently discovered that four of my guy
>anchors (both anchors on one leg of each tower) are actually on their
>property.  They have been nice enough to tell me it's ok, but two of them
>actually fall inside one of the corrals and I think it best to get them
>out of there.  I am not going to move the towers, so that means I have to
>put the anchors closer (the outer ones by 12 feet or so) and also
>probably shorten the towers somewhat.
>
>        The underlying question really is "how much can I cheat on the
>angle of the guy wires?".  Now there are those among you who will
>correctly tell me that any cheating is dangerous, and I understand that
>concept.  However, I am also aware that there is a different amount of
>danger associated with the anchor at 59% of the tower height than at 39%
>or 29%.  Also, my use of two anchors takes some strain off the anchor for
>the top guys - thus making the issue of the strain on the wire and tower
>legs more likely to be the critical problem.  The guy wire is 1/4 EHS,
>which I believe is rated for 6600 pounds.  The wires are broken up with
>insulators, and some of the wires are fastened with deadends while other
>connections are made using 3 cable clamps on each side.  (If it mattered,
>I could replace all cable clamps with deadends.)
>
>        Does anyone have any experience or idea of the reliability of an
>installation with the top anchor at 50% of the tower height?  How about
>as little as 40% (about 68% angle to the ground)?
>
>73, Dave Clemons K1VUT
>
>
>
>--
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>
>


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