"Jerry Stuckle" wrote in message
...
On 10/13/2014 10:12 AM, Ralph Mowery wrote:
"Lostgallifreyan" wrote in message
Rohn towers specifies about 10 % for their guy cables. That is for the
4000
breaking of 3/16 cable they recommend 400 pounds of tension on the guy
cables.


That is STATIC tension - that is, when no wind is blowing. Tension
increases significantly when there is a wind. Rohn tower specs are
designed to withstand winds of 85mph, IIRC (I last did commercial tower
work in 1972 or so, so I don't remember the exact specs). At that wind
they have maybe a 50% safety margin. Still significant for new cable,
but when your guys are 25 years old, the tower should still withstand
that wind.

And yes, some of the towers I put up over 40 years ago are still
standing. But I'm sure they've had some maintenance since that time.


Yes, static tension. I was thinking along the same line for the wire
antenna. YOu only want to put a fraction of the breaking tension on the
wire to allow for the wind and if on a swaying support like a tree.

Rohn 25g is specified for several differant wind speeds. Probably with
difffrant ammounts of antenna surface area. Sometimes either more or larger
guy wires are used.
I put a 60 foot tower up for myself about 10 years ago and it is still up.
Don't think we had any 75 mph winds, but could have during the gusts. I
tried to meet their specs or beter when I put it up. I know a couple of
local hams that over the years did not put them up to what I would have
thought was to specs and then came down.



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