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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