A penny added to the discussion:
My 85' tower is a mix of Height and Universal's aluminum tower pieces, some 8'
some 10'. During the time I was designing and evaluating I found that my tower,
self-supporting, should be able to take 80mph wind. I decided to add guy wires
and, by placing one set of wires at the (I don't remember exactly) the 70'
point the survival rate went to 130mph so I decided to add guy wires. Against
all belief, you add allowed wind speed by adding guy wires to a self supporting
tower as long as they are attached at the "right" spot. This gives the top 15'
"sticking out" above the rest of the structure.
You can vision a guyed tower as part of a sinusoidal curve. You want to have as
many "periods" as possible on the loading curve in order to get the best
survival. The top portion of the tower will act like a self supporting tower
with its "base" at the guyed support point. The tower structure will therefore
actually be stronger if you attach the guy wires below the top instead at the
top of the tower.
I never got the tower fully tested (Thank G-d) even if Sandy gave it a good
beating. The eye passed right over my place in Vermont and I believe I had wind
gusts around 80 mph.
73 de,
Hans - N2JFS
-----Original Message-----
From: kstover <kstover@ac0h.net>
To: 'Steve Walter' <stevewalter90@gmail.com>; towertalk
<towertalk@contesting.com>
Sent: Sun, Apr 29, 2018 2:13 pm
Subject: Re: [TowerTalk] Antenna wind load vs tower specs.
....
Other questions: The Rohn catalog shows the top guys on an 80' 45G at 65'.
Does this mean that if the guys were at the top the wind load would be 31.9?
80/65 x 25.9.
Is it correct to assume that a second Big Tri at 40' on my 45G would impart
an EPA at the top of the tower of 11.1 sq ft? 40/80 x 22.2.
Theres obviously a wide safety margin built in thats keeping a lot of
overloaded towers up in the air.
Am I over-thinking this?
Steve WA3A
--
Steve Walter
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