[TowerTalk] Triangular Crank-Up Wind Load Model

[Michael Tope]

----- Original Message ----- 
From: "Kinney John-r17512" <J.Kinney at freescale.com>
To: <towertalk at contesting.com>
Sent: Monday, January 16, 2006 4:12 PM
Subject: [TowerTalk] Triangular Crank-Up Wind Load Model


>I have a question pertaining to my Hy-Gain HG52SS tower or any other
> tower of this type for that matter.  The question: Does anyone have a
> model or has anyone attempted to model the wind loading of this type of
> tower, at heights less than full extension?  This tower is rated at 9
> square feet at 50 MPH average wind speed.  It would be interesting, to
> me at least, to see a graph or table stating the increase in wind load
> capacity as the tower is lowered to its resting height (21 feet.)  I
> asked this question via email directly to Hy-Gain, after their purchase
> by MFJ, but never received a reply.
> Thanks for the bandwidth.
> 73's
> John Kinney KA7CVJ
> 

I haven't done this analysis, John, but when I posed a similar 
question to Karl Tashjian at Tashjian Towers (old Tri-ex), he 
told me something surprising. On the Tashjian LM470, the 
wind rating actually drops when the antenna is partially nested 
because of the way the sections have additional bracing in the 
areas where the sections overlap when the tower is fully extended. 
So as you lower the tower the wind rating drops for while as the 
tower is partially retracted and then come back up to a much 
higher value when the tower is fully retracted. 

73 de Mike W4EF...................