Tom, et. al.,
A couple of field days ago we put up a tower with one of the anchors
reeeeaaaalll far away: they guys on this side were very long.
When we tightened all the guys, the long ones were "looser" then the others
- they sagged like crazy. But, we cranked away with the come-along, and
finally the tower BENT OVER at the lower guy point.
Out take-away was, "Keep all sets of guys symmetric."
-Rex-
K1HI
Rex Lint
Merrimack, NH
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of N1MM
Sent: Thursday, January 14, 2010 3:14 PM
To: Tower and HF antenna construction topics.
Subject: Re: [TowerTalk] FW: Guy article in CQ
WC1M said:
<snip>
I agree that the tension must be the same in all three directions, but not
only in magnitude. It must also be the same for the horizontal and vertical
vector components of the force along each guy wire.
<Snip>
The horizontal force components of a stationary tower guy point where the
three guys intersect is always zero. If they were not, the tower would be
moving. F=ma.
Why must the vertical components be equal? If a tower is guyed as designed
with three symmetric guys, the vertical components will be unequal as soon
as the wind starts to blow. The windward leg(s) will be in tension, and the
leeward leg(s) in compression.
Bear in mind that Rohn 25 can be erected to 200' and Rohn 45 to 300'
according to manufacturers specs. If your tower is a third of that, there
is a LOT of excess capacity in the strength of the legs. (Calculate the
downward force of the guys that are not being used.)
Tom - N1MM
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