I think the problem can be approached using Pythagoreans Theorem and =
force vectors....
a|\ c
|_\
b
a^2+b^2=3Dc^2
Shrinking the ac angle (making steeper) causes b (lateral force) to =
shrink. To equalize b (lateral force) with other runs of shallower =
angle, and a (vertical force) being constant, then c (tension on guy =
wire) must be increased.
David Johnson
KB5YLG
----------
From: Roger L. Elowitz[SMTP:K2JAS@worldnet.att.net]
Sent: Sunday, December 15, 1996 8:15 PM
To: towertalk@contesting.com
Subject: Guy Line Tension
Hi Guys,
I know that this just might sound a bit silly with all you big guns and =
tall
towers but... who better to turn to for advice?
I just put up a 3-section (9-ft ea) push up mast on the top of my garage
with the lowest section bracketed to the side of the house for just =
about
it's full 9-foot length. The second and third sections are guyed in =
three
directions with 1/8th inch diamond braid dacron Kevlar core line that is
supposed to be rated at 450# tensile strength.
On the top of the mast is a Ham-M rotor, a Cushcraft A-144-11 2m beam, =
about
4 feet above that is a 23-el ATV beam and way above that (about 8-ft) is =
an
AEA isopole for two meters.
Now the question I have has to do with guy line tension. My friend, who =
is
an Industrial Arts teacher and who helped me install the set-up, says =
that
the guy lines which run down to the garage roof at a steeper angle than =
the
guys to the house roof- need a greater amount of tension to keep the =
mast
vertical. This he claims is because of the shallower angle naturally
requires more tension.
Well, I have a bad track record when it comes to doubting people, =
(BETTER
stainless IS NOT MAGNETIC) but, I had the opinion that the angle of the =
guy
to the tower should make NO DIFFERENCE when it comes to tensioning them =
and
that I should aim for equal tension in all the lines.
To be on the safe side..... I left the guys with the steeper angle much
tighter than the others. Of course, I don't have a tension gauge so I =
really
have no idea if I am anywhere near the maximum rating on this guy =
material.
I do know that the mast is as vertical as I can possibly make it.
Your thoughts on this subject- on the reflector, would be much =
appreciated
as perhaps this subject applies equally to guying any structure with any
material.
Thanks all,
Roger, (easily snookered) K2JAS =20
=20
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|