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Re: [TowerTalk] Adding guys to self supporting towers

To: towertalk@contesting.com
Subject: Re: [TowerTalk] Adding guys to self supporting towers
From: Jim Lux <jimlux@earthlink.net>
Date: Tue, 13 Aug 2013 05:37:05 -0700
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
On 8/12/13 11:28 PM, Roger (K8RI) wrote:
On 8/12/2013 5:06 PM, Richard Karlquist wrote:
The topic of adding guys to self supporting towers has been
discussed a number of times on this reflector, but I am
still not clear on exactly why it supposedly won't work.

You forgot to add the guy tension.
This is a bit more simple than the analysis  that gave leg compression, but
  if i use the right trig function...it's a rough view of the forces.



Self supporting towers are much more complicated as they have leg
compression that a pier pin mounted, guyed tower does not and must be
stronger for a particular wind load



complicating all this is that for some towers, the limiting member is the diagonal cross braces. They tend to be longer and skinnier, and so have lower buckle loads for column loading. So while the vertical members might take the load without failing, the diagonals may not.

The distribution of uniform vertical load between corner tube/angle and diagonal is tricky: typically it's not something simple like a free pivot attachment, so you have to deal with bending and torsional loads and the relative stiffnesses of the members at that scale as well.

You need to get the engineering analysis for the tower in question and start looking at it in detail.
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