Mel:
Actually tube, if you are refering round sections, shapes are a little more
expensive than angle. The round section has full symmetry and is a more
efficient shape in compression loading than an angle shape due to the lack
of symmetry of the angle. Tower legs are actually sized by their compression
load carrying capacity, assuming a trussed type tower with diagonals, not by
flexural strength. Actually an angle shape is the worst type of cross
section next to a flat bar for axial load capacity.
Tube shapes are also more difficult to fabricate in three dimensions.
However being more efficient they can be lighter in a pounds per foot sense
and present a smaller x-section to the wind.
So in summary the use of tubular in tower legs comes from efficiency in
section; weight; and wind load area decision by the manufacturer or
designer.
73
Hank Lonberg, P.E. / KR7X
Beaverton, OR USA
Kr7x@arrl.net <mailto:Kr7x@arrl.net>
Hank.Lonberg@harrisgrp.com <mailto:Hank.Lonberg@harrisgrp.com>
Team Pantelleria - IH9P - African Italy - CQWW DX SSB
http://www.qsl.net/ih9p/
<http://www.fortunecity.com/skyscraper/eudora/126/ih9p.html>
-----Original Message-----
From: Mel Martin [SMTP:mel@interlink.net]
Sent: Tuesday, December 07, 1999 6:50 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Tower construction
Reading the mail, it seems many of the popular towers in the States
use tubular legs. We tend to use different brands up in Canada, and it seems
to me construction is more commonly using open L shaped legs, (my tower is a
20" face Leblanc and Royale) which avoids a number of problems I've seen
documented on the reflector recently. In addition, it's not as easy to see
defects or deterioration inside a tubular leg. I'm just wondering why
manufacturers still use tubing. Is it stronger? ...cheaper? ...easier to
fabricate?
--
Mel Martin
mel@interlink.net <mailto:mel@interlink.net>
VE2DC
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