Hi Bill,
I just calculated the torque on the tower element and compared them with
manufacturer recommended maximum torque. I found a small difference between a
stiff ground mounting and flexible ground mounting. I also tested
different locations of the guy wire attachment and selected the "best" point.
That's why the guy wires are attached 16 feet from the top. I did not make any
calculations of stress on the individual legs (which I probably should have
done to know for sure everything is within limits) but reasoned that; as
the tower is suppose to be self-supporting it should be better with guy
wires. As I have the guys anchors at the 100% point I am not concerned that
things will go wrong. Better: If it goes wrong it will be regardless what I
tried.
You are right though, the stress on the tower legs is critical as it is
what makes the tower stand.
Hans - N2JFS
In a message dated 10/7/2011 6:45:24 P.M. Eastern Daylight Time,
baycock2@centurytel.net writes:
Hans--
I wondered, because I'd always heard that Tower leg compressive stresses
were a critical factor. Did you monitor them?
My tower has four guys, but mostly for access and stability rather than
stress. (It is a folding unit) It is interesting to follow the tower leg
forces and the Guy stress as the wind direction is rotated from the "between
leg" direction to the "In Line" direction for different numbers of anchors.
Bill--W4BSG
On 10/6/2011 7:54 PM, _HansLG@aol.com_ (mailto:HansLG@aol.com) wrote:
Hi Bill,
With"stiffness" I mean how much the tower will move for a specific wind
pressure. In my calculations I assumed that the tower moved 1" for a give
wind. Then I calculated how much the tower moved for the same wind force
with
different guy anchor point. I found that minimum move was for an anchor
distance of ~142%. (probably sqr(2)) under the assumption of no guy wire
sag
(which is impossible).
I was just "playing around" with a spread sheet and was interested to see
where the optimum point was. 0% anchor point is no good for obvious reason
but an anchor point very far away is not good either as the guy wire is
springy and a too long wire will allow the tower to sway in the wind.
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