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[TowerTalk] Installing Big Grips

Subject: [TowerTalk] Installing Big Grips
From: "Donald Chester" <>
Date: Fri, 04 Aug 2006 02:25:30 +0000
List-post: <>
Several years ago I had to replace all 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 
the guy 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 cable clamps.  
As I recall I, purchased the Big Grips from Texas Towers.  They arrived with 
no written instructions whatever, but it appeared pretty obvious how they 
went together so I installed the new insulators with no difficulty.

Now, I have just recently read for the first time on a couple of websites 
that I ran across, that with the type 502 insulators I used, you are 
supposed to begin wrapping the grips at the SECOND set of paint marks, while 
with metal thimbles you begin at the first set of marks.  When I assembled 
mine, I began the wrap at the first set of paint marks, which seemed the  
obvious way to do it, and the assembly appeared to have gone together 

I would like to hear from others how you attached these insulators using Big 
Grips.  Does anyone know the reason why it would be recommended to begin at 
the second set of marks instead of at the first?

It has been 8 or 10 years since I installed those insulators, and I noticed 
just a couple of weeks ago that one of the insulators is freshly cracked, 
and the bottom part of the insulator that makes up the eyelet where the wire 
threads through is missing.  The part of the insulator that takes the 
compressive strain 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.  I am wondering if beginning the wrap too close to the insulator 
might have led to the failure by causing the wire to exert excessive 
pressure on the end of the insulator.  I see no lightning zorch marks on the 
broken insulator, nor is there any evidence of metal residue from a bullet.

It would seem that beginning the wrap at the second  set of marks would 
leave short, spiraled   sections of wire between the wrapping and the 
u-shaped section of wire that loops through the insulator, which would have 
less strength than straight unkinked wire, plus the pre-forms would be 
gripping a shorter length of wire.  Supposedly, utility pole guy grips are 
unsatisfactory for tower use because they have slightly less length than the 
ones designed for tower use.  Wouldn't beginning at the second marks defeat 
the advantage of using the Big Grips?

I also read on one website that with Big Grips the guy tension should be 
precisely set at the recommended 10 percent breaking strength of the guy 
wire, in this case 3/16" EHS, which would come out to 400 lbs if I recall 
correctly.  Not having a reliable tension gauge, I eyeballed mine, 
tightening each set of guys until each cable felt tight without excessive 

Maintaining the tension precisely at 10% would require readjusting the 
tension  at least twice a year, since I have noticed that during the coldest 
weather my guy wires tense up as the steel contracts, and they noticeably 
loosen up during hot weather, as indicated by the amount of sag and the feel 
of the cable.  I could see how too much tension could pose a danger of 
slippage, but what kind of failure could be caused by tensioning them at a 
little  less than 10%?

Also, does the manufacturer of Big Grips publish any written instructions?

This tower has been up for over 25 years, and broken guy insulators has been 
the only failure I have ever had.

Don k4kyv


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