Topband: Installing Big Grips

[Donald Chester]

I posted the following message on Towertalk, and got limited response, but I 
would also be interested in what some of the members of this list who have 
had considerable experience erecting towers would have to say on the 
subject, as this could possibly explain my mysteriously self-destructing guy 
insulator:

Several years ago I replaced the insulators in the bottom set of guys on my 
Rohn 25 series-fed 160 m vertical due to a lightning hit that pulverised 
every single insulator at the bottom guy level.  Originally, all insulators 
were attached using three u-bolt cable clamps at each termination plus 
serving the strands, per the Rohn book.  With the replacement insulators I 
used Big Grip pre-forms instead of clamps.  As I recall I, purchased the Big 
Grips from Texas Towers.  They arrived with no written instructions 
whatever, but the assembly procedure appeared obvious so I installed the new 
insulators with no difficulty.

I just recently read on a couple of different websites, that with the type 
502 insulators, you are supposed to begin wrapping the grips at the SECOND 
set of paint marks, while with other terminations you begin at the first set 
of marks.  When I assembled mine, I used the first set of  marks, which 
starts the wrap right at the beginning of the helical formation of the dead 
ends.

I would like to hear from others how you attached insulators using Big 
Grips.  Does anyone know the reason it might be recommended to begin at the 
second set of marks instead of at the first?  The instructions I downloaded 
from the PLP website make absolutely no mention of this.

After some 8 or 10 years since I reinstalled the insulators, I noticed just 
a couple of weeks ago that one of the insulators is freshly cracked, and the 
bottom half is totally missing.  The part of the insulator that takes the 
majority of the compressive force remains intact, so I don't feel an urgent 
need to  replace it immediately, but I plan to do so as soon as I can gather 
up the materials.  Perhaps beginning the wrap too close to the insulator 
might have caused the wire to pinch the end of the insulator with excessive 
force.  I see no lightning zorch marks on the remains of the insulator, nor 
is there any evidence of metal residue resulting from a gunshot.

It would seem that beginning the wrap at the second  set of marks would 
leave short, helical   sections of wire between the wrapping and the 
u-shaped part that loops through the insulator, which would have less 
strength than unkinked wire, plus this would leave the pre-form gripping a 
shorter length of cable.  According to PLP, powerline guy grips are 
unsatisfactory for tower use precisely because they have less gripping 
length than the ones designed for tower use.  Wouldn't beginning at the 
second marks defeat the advantage of using the Big Grips?


Don k4kyv




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