[TowerTalk] guys vs falling limbs

[Jim Thomson]

Date: Fri, 2 Dec 2011 17:23:35 +0000 (UTC)
From: w8zn at comcast.net
Subject: Re: [TowerTalk] guys vs falling limbs

I live on a small mountain outside D.C. and it is HEAVILY wooded. Just this spring I came home to find my 70ft tower laying across my roof. A 90 ft tree that seemed to be in perfect condition fell and took out my guys. I am now putting up a new tower and have adopted the "scorched earth" philosiphy. If it looks like it could even come close to my guys or tower, it's chain saw time. It takes too much time and money to have a tower and have it taken out by trees/limbs. If you even have to think about the choice between tower or tree, I suggest you find a different hobby or put up wire antennas. BTW, in 2003 I lost another tower by THREE trees falling on guys as a result of hurricane Isabel that came up the coast. Where's Paul Bunyon when you need him!!

Terry Price - W8ZN  ex K8ISK

##  A friend had a 160' rohn 45 tower, guyed with 3/8"  polygon rod  at 4 x levels.  The bottom 20'  was  just 1/4" EHS.    In a 45-50 mph wind one night, a 110' tree came down.... and the top 30' of the tree nailed the bottom 30'  of the polygon rod ! 
That tree was a LONG way away from the base of tower too.   The tree hit the polygon rod...then slid down, forming  a "U"  as it slid down.      Ok, once it got to the junction of the 1/4" EHS, the EHS won, and the  polygon rod  lost. 
Tree sliced through the top 2 x sets of polygon rods.    Then the SINGLE bolt that hold the back end of the equalizer plate, snapped off.   Then you have NO guys at all, and the tower came 
crashing down, fully loaded with yagi's,  4 x tic rings, etc.   A real mess...at 2AM.   I saw pix of the bottom end of the 2 x polygon rods  [ top 2 x guys].   It was in a thousand super fine strands, for the last few inchs !   Before the new tower went up,I strongly suggested he figure out what other trees could hit any of the 12 x guys.  Either cut em down full length or  top em, or a bit of  both.  The kicker was, the root system under the fallen tree was no where near as big as one would think. Bottom line is, you can have a tree that's say 260' away from the base of the tower..and easily bring the tower down.  Top 20-40' of a tree hitting the bottom 10-30'  of any guy wire is bad news.  That 3/8 solid fiberglass guy rod has a heck of a lot less shear strength  to it  VS 
1/4" EHS.      If that had been  3/8"  EHS, with eggs  in em,  it may well have been a whole different outcome.   The solid 3/8" polygon rod has loads  of tensile  strength, but way less shear strength.   I suspect that phillystran  is no better for shear either.

later... Jim  VE7RF