----- Original Message -----
From: <w3svj@juno.com>
Subject: [TowerTalk] 25G
>
> How risky is it to hoist 60 feet of 25G from somewhere above the C of G?
> The club (Steel City ARC, W3KWH) is trying to get the ATV repeater
> receive antenna a bit higher above the tree line. The antenna represents
> about 1.5 sq ft of windload.
>
> The plan is to assemble it all on the ground and secure the top guys as
> well as tie down the hardline. Of course the earth end of the guys would
> secured and the tower plumbed when it is upright.
>
> The concern is, will the tower buckle under its own weight before it can
> be swung to the vertical?
Nate:
I installed a 70 foot 25G tower several years ago much as you describe. I
marked the bottom of one tower leg and the corresponding stub with tape so
the tower would be oriented correctly with different lengths of guy
connected. All guys were pre constructed and turnbuckles ready to be put in
place, etc. We used a "cherry picker" crane from a local sign company
attaching to the tower about 15 ft above the Center of Gravity. Short tag
lines of steel cable were attached to the bottom of the tower to have
control of the tower. This type of crane allows the operator in the bucket
at the top to move the crane for correct alignment for placement. Once
placed on the stubs, the crane maintained control until the bolts were
placed and the lower guys could be connected and reasonably tensioned.
After the crane was gone, the upper three guys were attached and the lower
and upper guys were all were adjusted for proper tension, etc. No sign of
tendency to buckle of the tower was noted.
I don't think I would want to attempt this with a very large antenna on the
tower, but your antenna seems small enough. Incidently, as you know, Rohn
used to make a tilt over tower which tilted near the middle of the tower,
and the stresses on the upper part of the tower as it tilted over should
have bedn similar to the stresses of attaching a crane at the center. Also
when the tower was tilted, often a fairly heavy yagi or such was on the top
of the tower which should put much more stress on the tower than the antenna
you are planning to use. Rarely, the tilt over mechanism would try to break
from stresses as the towers aged, but the tower itself seemed to be plenty
strong.
We did pick a windless day....Good Luck.
73, Jay, W5SL, Austin, Texas
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