No, I did not include the catenary curve in my calculation. actually, the
spring coefficient doesn't come into the calculation at all.
I figure the effect of the curve would act similar to the stretch movement.
Maybe that was to oversimplify the whole thing. I would like to see how the
"spring" coefficient looks for the curve. I just assumed that Hooks law is
valid there too.
Hans - N2JFS
-----Original Message-----
From: N4ZR <n4zr@comcast.net>
To: Hans Hammarquist <hanslg@aol.com>; TowerTalk <TowerTalk@contesting.com>
Sent: Fri, Dec 14, 2018 9:29 pm
Subject: Re: [TowerTalk] Fwd: guying distance
Hans, I wonder, did your analysis take into account the catenary curve caused
by the weight of the guy wire? K1TTT did a nice, complete analysis of what's
involved, somewhere on his web site. I believe K7NV also has a lot to say
about this on his web site, based on finite-element analysis. From memory, the
catenary curve is much more of a factor than EHS stretch - that's why tower
manufacturers specify both a size and a static tension value for each guy, to
take out much of the catenary. FWIW, my 97-foot Rohn 25 tower had single guy
anchors at 85 feet from the base, and guy sets at 31, 62 and 92 feet.
73, Pete N4ZR
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On 12/9/2018 11:30 AM, Hans Hammarquist via TowerTalk wrote:
Just to throw in my ten cents:
I did a calculation once regarding how far out from the tower you should attach
the guy wires. The calculation took into account the springiness of the wires
(Yes, a guy wire stretch like a spring when you pull on it.) I found (I don't
remember the exact value) that if you attached the guy wire ~130% from the
tower you had the smallest movement on the tower due to the spring action of
the wire.
If you think about the extremes a guy wire attached 1) very close to the tower;
a small stretch gives a large movement, 2) very, very far away from the tower:
a small force gives a lot of stretch of all that wire.
Also remember the closer the attachment point is to the tower the more
down-force you will put on the tower.
Further thoughts: I use four guy wires at 90 deg angle as that is less critical
with the angle between the wires and a somewhat smaller tension on each wire
(~10%). I have a square "strong-place" on/in the tower for the attachment of
the four guy wires. That gives an easy attachment for the wires and is
unloading any "pull-apart" forces on the tower.
73 de,
Hans - N2JFS
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