I have heard of persons using an automobile drive shaft coupling in a long
tubing-mast arrangement to provide some torsion relief to the tower and
rotator. In the lore that was passed along to me it was said that people
used the couplings from BMW drive shafts. Perhaps others on TT have real
data and not just "oral history" about such use.
I have always thought that this might offer a reasonable accommodation for
those who want to "push" the torsion specifications of the tower. When all
is said and done I would expect that the torsion force is transmitted via
the tube to the coupling and to some extend is dissipated in the coupling,
but I would think the mounting to the ground would have to be sufficient to
tolerate the final torsion force.
Tod, K0TO
-----Original Message-----
From: Jan L. Ditzian <ditzian@greenepa.net>
To: towertalk@contesting.com <towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Friday, July 03, 1998 9:01 AM
Subject: [TowerTalk] Torsion and masts
The TowerTalk reflector has been a wonderful source of
information and even deals related to towers and antennas, so I
thought I might push you guys for some more information.
I have been warned that one problem with very long masts used for
turning antennas is that there is rotational flexibility in the
mast. By the time one has 50 feet of mast between a rotor (at
the bottom of a tower, for example) and the antenna (at the top
of the tower, sitting on a thrust bearing) one may expect a fair
amount of turning in the breeze, or of lag in alignment between
the rotor and the antenna when the rotor turns. Furthermore,
this may result in some whiplashing of the whole system when the
antenna is turned and then stopped.
My question is whether wood (for example, 2x4 lumber) would
resist this rotational or torsional effect better than round
steel pipe or tubing (probably pipe due to cost)? Assume that
there is no weight on the mast (or lumber); the mast simply turns
the antenna that is sitting on the thrust bearing that is sitting
on the tower.
Please do not bother to excuse the bandwidth; I wanted to use it
and I did. This submission has been reviewed for correctness of
spelling, grammar, and punctuation, but a human being did the
review. The language has been tailored to the expected level of
reading ability of a majority of readers of the TowerTalk
reflector. I have attempted to offend the greatest number of
readers. If there are more anti-PC comments that can be made, I
cannot think of them. Your comments in matters related to this
final paragraph are best directed to me at ditzian@greenepa.net.
Comments on the technical questions are appropriate to
TowerTalk@contesting.com.
Thank you,
Jan, KX2A
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