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1500 foot tower mishap

To: <>
Subject: 1500 foot tower mishap
From: (
Date: Tue, 15 Oct 1996 17:00:04 -0400
In a message dated 96-10-15 16:10:01 EDT, you write:

>       I'm curious as to what is meant by the tower "collapsing".  I 
>would have envisioned a severed guy wire to have caused the tower to bend 
>over at the next lower guyed section, and all sections below that one to 
>remain in place.  Perhaps that idea has no engineering data to back it up?
>       Several years ago during a gale, a 75 foot pine tree broke (10 feet
>up from the ground) and fall across a set of guys holding up 85 feet of Rohn

>tower.  The tower folded up at each guyed section (3 total) and hit the 
>ground with such force that the schedule 80 water pipe was bent at about 
>a 30 degree angle where it came out of the thrust bearing.  This, of 
>course, is not the same case as above because of the downward force 
>applied by a few tons worth of pine tree.  (Needless to say, I was 
>thankful that God allowed it to happen a couple hours after my children 
>had finished feeding the pigs and chickens.  The whole thing made so much 
>noise that my wife thought something had hit the house, which was about 
>60 feet away from all the action.)

Hi, Dave --

     Thank goodness no one was hurt.  A tree hitting the guy wires causes a
different scenario and your damage is probably typical.  A big alder tree
landed on the guys of W7XR's 40M tower (55G with star bracket on top with 2
guys per guy point) and just stretched the guy wires.  I don't think 45G
would have come through as unscathed.   See how handy over-engineering
something can be?
>       I currently have two towers, each having three sets of guy 
>wires.  I put the high set of guys on one anchor, and the lower two sets 
>on a separate anchor.  This I feel is safer in case an anchor lets go.
>(Incidently, what let go in the tree accident was the guy wire clamps and 
>the tower sections which bent but not the anchors.)
>       If I should ever lose a top guy wire or its anchor, should I expect 
>to have the tower collapse instead of bending?

      Interesting question.  According to the information that I've seen, a
guyed tower will fall typically within a circle around its base approximately
30% of its height.  It doesn't "fall over" because it is constrained, or
tethered, by the remaining guy wires.  Talk about a pile of scrap...

    BTW, this probably shoots the heck out of tower building set-back

73,  Steve K7LXC

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