Pulled quote from below:
"... most of the officials i worked with in FL and here in KH6
seem to think that towers fall over at the base sideways."
Well I'd better delete these photos from my website real quick:
http://tinyurl.com/2wgq5t
You'll want to examine photo 040, where the bottom of the tower
came to rest about 8 feet to the east of the 6-yard concrete base.
This was a 90 foot self supporting tower with a Mosley PRO-67B
at the top and a Diamond 144/440 vertical on the mast.
My situation is the exception to Bill's comment "just about every
tower failure...". It was an intense storm front (downburst or wind
shear event) that ripped my tower from its base. These high winds
(100 ~ 150 mph) are not uncommon in the Midwest.
Gary, KØGX in a nearby suburb lost trees and suffered tower damage
in a similar storm about 2 years ago. His aerometer recorded 125+
mph wind speed. His tower stood, although it was bent. Both of our
QTH's are within an 80 mph wind zone. See page 12 at:
http://www.tcdxa.org/September2006Grayline.pdf for Gary's saga.
It includes an interesting photo story how an existing tower base
was retrofitted for a different brand tower.
Airplanes have been known to get into trouble or crash if they
encounter wind shear. An onboard detection system was mandated
for commercial aircraft after 1993. More info here:
http://www.geo.mtu.edu/department/classes/ge406/jmedward/windsheer/index.html
I agree that "most" guyed towers will come down within a "semi-
predictable" circumference of the base. (There's always exceptions.)
The weight and restraint of the guy wires play a major role in this.
I toured the 1971 Shoreview, MN collapse of a 1200 foot tower and
the wreckage was contained within a fraction of the tower height.
I worked one block from that site. The tower was there in the
morning and disappeared later in the day. Seven workers lost
their lives in that accident.
73 de Bob - KØRC in MN
----------------------Original Message thread---------------------------
Message: 1
Date: Sun, 2 Sep 2007 00:05:51 EDT
From: Cqtestk4xs@aol.com
Subject: Re: [TowerTalk] Setback requirements (was "permit in hand")
To: TOWERTALK@contesting.com
Message-ID: <c3c.1c25db02.340b909f@aol.com>
Content-Type: text/plain; charset="US-ASCII"
In a message dated 9/2/2007 3:25:07 A.M. Greenwich Standard Time,
w7ce@curtiss.net writes:
Is there an automatic assumption
that standard engineering practice is questionable with tower designs and
that they are likely to fall down? Nobody makes that assumption with 100'
plus high commercial buildings.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
That seems to be the case...most of the officials i worked with in FL and
here in KH6 seem to think that towers fall over at the base sideways. A
hundred foot tower falls over 100 feet. Yet, just about every tower failure
I've
ever seen as a result of hurricanes or seen posts of on the internet that did
not happen.
It's hard.....and expensive to argue with ignorance down at city hall.
Bill K4XS/KH7XS
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