Let me share a story from about 20 years ago. I had a UST crank up, HDX 555,
with a 20 ft moly steel mast and a tail twister. Th7DXX and a 2 element shorty
forty on top. Well below the 30 sq ft @ 50MPH rating of the tower. This was
in a southern CA coastal city where we generally did not get huge winds.
I was at work, only 4 blocks from home, when a storm blew in with gale force
winds (peak gusts of 65 mph). One of my sons (a ham) was at home and called me
to say that the tower and yagis were swaying side to side and he thought it was
going to bend. Rushed home and attempted to crank down the tower....unable to
do so due to lateral forces of the wind. Storm finally blew through. The
tower was actually bent to the point that it would NOT retract. A fairly
expensive crane got it down and the tower was tweaked enough that it was
unusable. A local engineer (also a ham) "speculated" that if the tower had
been equipped with a motorized pull down system I might have been able to
retract it in the wind but gravity didn't work because the sections bound on
each other.
I WOULD NOT push the envelope unless I had (and I know several who have done
this) a motorized pull down system linked to a wind speed detector that would
automatically cause the retraction to occur if I were not home to manually
activate it. Even that is not fool proof because if there is a power failure
the MPD won't work.
Jerry
N7WR
----- Original Message -----
From: john@kk9a.com<mailto:john@kk9a.com>
To: TOWERTALK@contesting.com<mailto:TOWERTALK@contesting.com>
Cc: jknodel@msn.com<mailto:jknodel@msn.com>
Sent: Sunday, October 15, 2006 5:49 PM
Subject: [TowerTalk] Am I asking for trouble? - tower loading
Why is this your only option. You didn't say which UST model you are
considering, so I will assume that it is the heaviest one in their catalog.
Perhaps they or another crankup tower company can make a heavier one for
you. If not certainly AN Wireless, Rohn, Glen Martin, etc make very strong
self supporting towers. Sooner or later you will mistakenly leave the tower
up or have it get stuck during a strong wind. I'm not sure how much safety
margin there is in the US Towers design or what will happen if it fails, is
this a risk that you wish to take?
John KK9A
To: towertalk@contesting.com<mailto:towertalk@contesting.com>
Subject: [TowerTalk] Am I asking for trouble? - tower loading
From: "jknodel M Knodel"
Date: Sun, 15 Oct 2006 10:57:46 -0700
I would like to get everyone's opinion on this -
I am planning on installing a US Towers crankup tower. These towers are
rated for windloads at 50mph and 70mph. I want to stack 2 beams on the
tower. These 2 antennas would exceed the tower's windload rating at 70mph
but would be well within the rating for 50mph. I plan to install a wind
speed meter and deligently crank down the tower every time the wind exceeds
50mph.
I cannot install a guyed tower at this location so this is my only option.
The crankup with these antennas and cranking it down in winds over 50mph is
my plan. Am I asking for trouble in doing this?? Thanks.
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