DAVID JONES wrote:
Yikes David!
Tough request! Comments interspersed.
< Hi and thanks for taking the time to read this.
< The winter storms we have been getting here over the past few years
seem <to be getting stronger and stronger. I put a 60' freestanding
tower up <over recent years, and on it I have a 4 element 5 band quad.
Last year I <put 3 guys on the tower at around 45'. They were not
extremely strong <wires, but I put them on to give that little extra
support.
< During the winter we had 2 very severe wind storms the worst had
winds <of 95mph+. The tower was fine but the quad had minor damage
around $20.
< It is the tower I want to protect in the high winds, as the quad
can be <repaired easily without much expense.
< This summer I am going to replace my temporary wires with a more
<substantial arrangement. I intend to put just one set of wires on at
around <48' up the tower. I do not want to go higher as it would begin
to get close <to the quad. (Bottom of the elements are around the 54')
<Questions
<1. Do I put a set of 3 guy wires or 4 guy wires equally spaced
around the <tower.
This question is very hard to address without lots of detailed info
about the tower.
If there would be a "rule of thumb", one would guy the tower based on
the number of faces (or legs) on it. Three leg towers get 3 guys, etc.
But that is not a definitive conclusion without more info and
examination.
<2. What direction should they face taking into account the worst
storms <come from the SW, W, NW.
This is an equally tough call. Generally, for 3 guy directions, guy
loads are highest when the wind is 30 deg from any guy anchor. When the
wind is in line with any anchor, the tower combined stress is least.
When the wind bisects a pair of guys, the guy loads are least, but the
tower deflections, and hence combined stress are greatest.
One needs to know what is limiting the tower, to decide which way to go!
<3. How far should the guys be anchored from the base of the tower, I
<appreciate the ARRL suggests at least 60% of the tower height, but if
needed <they could go up to 60ft from the base.
80% of tower height is the widely acceptable distance.
<4 The tower weighs around 750kg (1650 lbs), any idea what size of
load <may be on the guy wires, in such high winds. (I appreciate this
would be <hard to calculate as surface area would need to be known, a
ball park figure <would be great however ). If it is of any help the
tower is 24"X18" and <made from 2" angle iron)
What is the tower rated safe wind speed with how much antenna area,
compared to what you are doing?
If you obtain a copy of the tower design spec, for your tower, you can
figure this one out.
< A lot of questions but any answers to any of them would be very
much <appreciated. If you wish you can reply to me directly at
<glenn@gi0kvq.freeserve.co.uk
Unfortunately, there is not nearly enough information present to try and
answer the questions. If the necessary information was present, finding
the answers would still be far from a trivial exercise.
You might try contacting the tower manufacturer for more info and advice
on what you are trying to accomplish.
You can find some interesting reading on this subject at the URL below.
Follow the link to the Guyed Tower Study.
Good luck, and try to talk to the tower designers, they will be able to
provide the best info.
--
73, Kurt, K7NV
YagiStress - The Ultimate Software for Yagi Mechanical Design
Visit http://www.freeyellow.com/members3/yagistress/
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