[TowerTalk] Rohn 25G screw-in guys

[n4kg@juno.com]

MakeMyDay raises an interesting question about
possible slip in guy grips when my guys lengthened
after 2 trees fell on them during a tornado.

After inspecting the grips at the anchors, I could not
see any sign of slippage (i.e. difference in color or
a ring on the guy wire above the grip end).

Visual inspection of the grips at the first insulator
revealed the ends of the guy wire were still visible
just inside the crossover point of the grips.

My conjecture is that the guy wires stretched.
It IS possible that they may not have been EHS.
Most of my 1/4 inch guy wire was obtained surplus
from either utility or CATV service.

I have seen two toppled towers in the last 30 years.
In both cases, the guy wires pulled through CABLE
CLAMPS due to strong winds. In neither case was
there a contributing factor such as falling trees.
In both cases, only 2 *cable clamps* were used 
at the failed junction, a clear violation of Rohn's
recommended 3 clamps PLUS served ends of
the cable wire. If you must use clamps, be sure
to use at least 3 and be sure to tighten them properly.

In addition to the above two fallen towers, I heard a
story about a new 120 ft R25 tower installation where
a storm came through the night after the tower was
erected.  The story teller reported receiving a frantic
call from the owner in the middle of the night reporting
that the tower was swaying frantically as the top 3 levels
of guys had come loose.  Only the bottom set was holding
the tower up.  

The upper guys had pulled through the CABLE  CLAMPS 
at the anchor.  It is a common fault of inexperienced installers 
to NOT tighten each side of the clamps equally by alternating 
the tightening sequence.  I have seen loose clamps on 
Field Day where one side was tight but the other was loose,
presumably because the loose side was tightened first but
not re-tightened after the second side was tightened.

I suggest that improper installation is MUCH less likely
with guy grips than with cable clamps.

de  Tom  N4KG


On Sun, 06 Aug 2000 07:15:31 +0100 MakeMyDay <makemyday@worldnet.att.net>
writes:
> n4kg@juno.com wrote:
> > 
> > Have you checked for guy wire stretch / lengthening?
> > 
> > With time, the wires or grips will pull closer to the insulators
> > and thimbles,  reducing tension in the guys.
> > 
> > When two trees fell on the top set of guys (1/4 inch)  for my
> > 130 ft tower, they pulled (arched) the top of the tower about
> > 12 inches or so.   The anchors did not appear to have moved
> > so I assume the guys stretched.
> 
> Or perhaps the cable has partially pulled out of the preforms in 
> places....

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