[TowerTalk] Horizontal tower movement at the top

[SavageBR at aol.com]

>You have got to be kidding! April Fool's Day was over a month  ago!!
 
Bruce
 
From: "W7CE" <w7ce at curtiss.net>
>To:  <towertalk at contesting.com>
>Subject: [TowerTalk] Horizontal tower  movement at the top
>Date: Sun, 6 May 2007 14:20:36  -0700
>
>Does anyone know how much horizontal movement is considered  acceptable at
>the top of 100' tall Rohn 25G, 45G and 65G towers?  I  don't see any mention
>of it in the Rohn catalog.  I know that the  tops move, I just don't know 
>how
>much is considered  normal.
>
>I'm considering a rather unusual tower installation at my  QTH.  Because of
>large trees that occasionally lose branches during  wind storms and property
>line constraints, a guyed tower isn't  practical.  For years I've had my 3
>element yagi on top of a 95'  Doug Fir tree and it has worked well there.  I
>watched it during our  record setting wind storms last winter and the top of
>the tree was only  moving about 6-7" (less than the diameter of my Ham IV
>rotator).   This is a big tree with a 42" diameter base and an 8" diameter
>stump at  the 95' level where the antenna is mounted.  The problem with  this
>installation is getting up to the antenna to do maintenance, plus  I'm
>planning on replacing it with a new SteppIR as soon as I figure out  how I'm
>going to mount it.  What I'm thinking about doing is  installing 100' of
>tower as close to the tree as practical (less than 3')  and attaching it to
>the sides of the tree with angle iron at 20'  intervals.  With this 
>approach,
>I don't think the tower  could ever come down unless the tree itself did
>also, which is unlikely  based on our soil type and the excellent health of
>the tree.  I  would then mount the antenna on the top of the tower.  This
>would  give me a much easier way to climb up to the top.  I can use 25G,  45G
>or 65G for the installation, whichever would be best.  25G would  be the
>easiest to install because of it's weight and I suspect that it is  the best
>choice.
>
>I'm looking for opinions on the viability  of this solution.  Will the
>movement of the tree in the wind stress  the tower too much or will it about
>the same amount of movement that a  guyed tower would normally experience in
>a big wind?   Opinions?  Suggestions?  Am I thinking a little too far  
>outside
>the box?
>
>73,
>Clay   W7CE




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