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Re: [TowerTalk] Tower in Tree...bad feelings..

Subject: Re: [TowerTalk] Tower in Tree...bad feelings..
From: "Dan Zimmerman N3OX" <>
Date: Wed, 9 May 2007 13:46:39 -0400
List-post: <>
>All I am saying is that tower/antenna work is hazardous enough in "normal"

Which is why any "weird" endeavor such as this should be approached
from a sound, rational engineering perspective, informed, of course,
by the voice of experience.

I don't think that it's necessarily good advice, though, to avoid
doing something because it's simply out of the ordinary as long as the
analysis of the situation shows that it would be safe.  What really
needs to happen here is a stress analysis of a tree-tower model under
wind loading.  The growth of the tree can be dealt with... the forces
the tree exerts on the tower and vice versa under wind loading,
however, should be known before proceeding.

The tree would be modeled well as a tapered round beam; the material
properties of Douglas Fir are available, though they're for dry wood,
not a live tree. The material and section properties for Rohn towers
are also available.

Put it all together, apply a realistic load based on a realistic wind
profile for your location, and you can get a good estimate of the
stress distribution in the tree-tower system.

Honestly, the answer might not be obvious.

is apparently some links to some free/demo structural analysis software

has material properties.

I'm not a structural engineer, I just play one on TV (I've run a lot
of structural analysis on an physics experiment I'm building for my
Ph.D., but it won't kill anyone if the structure yields) so I can't
and don't want to advocate any particular approach, but maybe you can
run your own analysis and convince yourself that the tower won't be
stressed too much.

What I can say is that I would be comfortable using that tree as a
support for a big beam. I'd probably be comfortable climbing it.  What
I can't say is whether or not the tower will break the tree or the
tree will break the tower.

It would be a shame to abandon this idea because no one else has done
it or because someone's emotional reaction is that it's a bad idea.

It would be a much bigger shame if a tower section came loose with you on it.


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