In a message dated 96-10-16 00:38:44 EDT, you write:
>Steve, I asked you this question before I think. Should I use thimbles when
>attaching preformed guy grips to the tower leg? If so, then the thimbles
>that normally fit the grips are too small to fit around the tower leg, and I
>need to go several sizes larger on the thimble, and bend them to place on
>the tower leg, and straighten them out once installed.
>That seems to be a tedious operation. Won't the nice round tower leg provide
>adequate turning radius for the preformed grips?
>
>Sorry for being dense, but I don't want to get near collapsing towers, and
>want mine to stay up onmce installed.
>
Hi, Vic --
Hmm; a multi-faceted question. In ANY installation, the LXC law is to "
do what the manufacturer says". Although many hams just put the preform grip
around the leg and haven't had a catastrophe (yet), it isn't the Rohn spec.
Since you're in hurricane alley (100 MPH wind zone), I would follow Rohn's
specifications exactly. What that means is to use the guy assemblies
(GA25/45D) and not attach the guys directly to the leg.
In response to your first question, yes - use thimbles at ALL
terminations. Although the tower leg gives you a nice convenient radius for
the preforms, this technique does nothing for the wind induced torque that
will try to twist your tower down. This is the function of the guy
assemblies; to add torque resistance.
There is a specified size of thimble for each part of the guy wire
system; i.e. 3/16" preform grip takes a 7/16 to 3/8 inch thimble. BTW, the
'seat diameter' (which is the distance/radius required) for a 3/16" preform
is one inch minimum. Since 25G is 1.25 inch OD, it does give an acceptable
seat diameter for installing the preform grip directly on the leg.
Moving along, you'll need to use thimbles when using the guy assemblies
but they are smaller diameter than the legs and you shouldn't have as much
trouble getting the thimbles over them. There are different kinds of
thimbles. Many are teardrop-shaped; these are the ones that you'll have to
open up when installing them. Check with your local suppliers; there are
also thimbles that are U-shaped with enough clearance in the mouth that you
should have a minimum of fuss installing them. Yes, the whole process is
tedious but just think how well you'll sleep nights knowing you did
everything correctly.
73 and good luck, Steve K7LXC
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