I'm not sure when Trylon started making crank-ups. As far as
I know, they never have. They make self-supporting
free-standing towers, as well as guyed commercials towers,
but not crankups.
Can they fall down under really bad conditions, or if something
goes wrong? Yes, of course. So do very large guyed towers,
including 100'+ ham towers, and 1500' foot commercial towers.
We've all seen the pictures, and we should plan and build to
avoid that. But if it gets hit by an F5 tornado or by extremely
severe ice and wind, all you'll have left is a slab and scrap metal,
no matter how many and how thick your guy wires.
----- Original Message -----
From: "Wendell Wyly - W5FL" <firstname.lastname@example.org>
To: "'Dave NØRQ'" <email@example.com>; "'towertalk reflector'"
Sent: Friday, June 11, 2004 11:44 PM
Subject: RE: [TowerTalk] Broken Self Supporting Crank Up Tower
Trylon makes one of the better self supporting crank up towers and is
probably the one I would buy.
That said, a Trylon T600 64 foot tower with 1/2 inch radial ice with 100 mph
winds is rated for 0.00 sq foot ant load! At 85 mph and 1/2 inch ice the
Flat antenna max load is only 4 sq ft which is smaller than almost any
antenna with ice on it. Also rated with a maximum lateral thrust of 116
pounds and antenna weight of 300 pounds centered and balanced on the tower.
The antenna cross section in square feet typically far exceeds the ratings
with 1/2 inch radial ice. This does not include the typical two or three
feedlines and control lines, rotor, thrust bearing, mast, mast to boom flat
plates, antenna switch boxes, etc., that most of us use routinely on our
towers that also triple in square footage under icing conditions. Most
antennas are rated in flat square feet and most tower loads are rated in
round square feet. It may be marketing strategy, but you can't have it both
ways. Trylon shows these calculations at a safety factor of 1.0, which is
not comforting. At my location in North Central Texas, these conditions are
routinely exceeded several times a year, although this is a "70 mph area and
I have a Catagory C location".
I believe these are a few of the reasons why several crank up self
supporting towers have come down in Texas. The tower I saw went down under
no icing conditions, but high winds and gusty winds, which are even worse
since few antennas are really balanced for wind loading.
After thinking about it, I will stick with guyed towers.
[mailto:firstname.lastname@example.org] On Behalf Of Dave NØRQ
Sent: Friday, June 11, 2004 9:12 PM
To: towertalk reflector
Subject: Re: [TowerTalk] Broken Self Supporting Crank Up Tower
Though I agree with the intent of the comments, which I think was
"too many guys overload their towers or don't install them correctly",
I think that it is quite incorrect to categorize all self-supporting towers
in the same way.
We all probably know of hams that have done shoddy or under-
engineered installations -- because towers sometimes fall down ---
both guyed and self-supporting ones, I might add!
When I put up my self-supporting Trylon T600 64' a few years ago,
I selected the size, not based on my area's wind speed of 70 mph,
but on 100 mph. With only 15 sqft of antennas on it, I think that it
will continue to support itself quite well. And it if does fall, my house
will probably be missing or severely damaged, in which case the broken
tower will be the least of my concerns.
Self-supporting towers are great, even here in Texas,
IF DONE CORRECTLY. Guyed towers are fine, too,
IF DONE CORRECTLY.
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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