At 07:53 AM 6/29/2005, Dale, KG4OLE wrote:
>Hi All,
>I have a just acquired a Hy-Gain HG-37SS self supporting tower and am
>looking for any information that would help in satisfying the local code
>compliance office. The tower specifications say it is rated at 50 MPH
>fully extended (36 feet) with a 9 square ft antenna load. The code
>requirement at my QTH is 80 MPH. A little short of the requirements but
>the code compliance office is willing to accept a wind survival of 80 MPH
>with the tower retracted (Nested) and the 3.22 sq ft wind surface area
>antenna which I plan to use. I have gone to MFJ ,new owner of Hy-Gain,
>but no luck yet.
>
>If anyone has any information or engineering data on this tower to
>indicate the wind survivability rating in the retracted position I would
>be forever grateful.
How rigorous an analysis is the code compliance guy going to want? To a
first order, the loads you're worried about are the compression and tension
loads at the base. They'll be linearly proportional to the height and wind
velocity squared, so, if the antenna is rated at 50 mi/hr at 36 ft, the
loads will be similar at 80 mi/hr with the height of the tower at 36 *
(50/80)^2 = 14 ft. Does the tower collapse that much? This back of the
envelope calc completely neglects the windage area of the tower, which is
probably a significant part of the overall loads, and for which dropping
the tower probably helps. Is there a requirement to be able to drop the
tower under load (many telescoping towers bind horribly if there's a
lateral load)?
>TNK,
>Dale <KG4OLE>
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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TowerTalk@contesting.com
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