On 12/7/2015 9:15 AM, wosborne44@gmail.com wrote:
I have a 50 foot Universal Aluminum tower which I would like to extend
to 80-100 feet and guy it to offset the fact the base sections would not
be large enough for Universal's design drawings at that height. Anyone
have any experience good or bad in trying to do something like this?
Thanks,
William Osborne--K5ZQ
I am in process of designing two identical 88 foot Heights
towers. These sections are from the legacy Heights company,
not the current reincarnated one. The legacy sections are
fairly light duty construction, and won't handle much load
at 85 MPH in the self supporting configuration. After
extensive FEA calculations with guyed configurations,
I came to the conclusion that the sections smaller
than 22 inches are not useful for serious towers, even
with guying. I had been worried that they would not
handle the wind torque, but it was even worse than
that. They could not even handle the thrust.
The larger sections, with guying, can handle a fairly
large antenna, like 20 square feet, both in terms of
thrust and torque.
As far as guying is concerned, Heights towers, at least,
have the braces welded to the *outside* of the tubes.
This means that a Rohn clone guying bracket that wraps
around the outside doesn't work. I think I have a
guying solution that will work. I need to make a wooden
model of it to make sure there are no interferences with
the braces, etc.
The towers will be tilted up in one piece with the antennas
in place on tilt plates using a 50 ft Glen Martin tower as
a fixed gin pole (*not* a falling derrick.) I looked
into that and decided against it. The tilt up scheme
was another reason why the smaller sections were problematical.
They "failed" on the way up.
I have two of the old Heights fold over piano-type hinges
to use at the base. These are supposed to use an acme
threaded rod with a motor. The threaded rod lift is
a complete non starter for these sizable towers, hence
the ginpole. I'm just using them as hinges.
BTW, the fact that the braces are on the outside rules out
a Hazer type solution (other than the Voyager type).
We are looking at applying for a permit in a few months.
Any drawings from the manufacturer are useless for a permit
anyway, unless they use EIA-222-G, which is a completely
different concept from the previous versions.
Rick N6RK
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