[TowerTalk] Some Notes on Installing Big Grips

[Donald Chester]

A major problem I have had when using Big Grips on guy wires is lack of installation instructions. About 20 years ago I purchased some from Texas Towers, and more recently from Hill Radio in Illinois, and in both instances the grips arrived with no instructions whatever. This time, I was able to download instructions on-line from the PLP website, but I lacked internet access 20 years ago. I don't know if this is the fault of PLP or the vendors who re-sell the product, but you would think that any product that requires a specific, systematic installation procedure critical to safety, as these grips do, would come with instructions.  A mistake I made 20 years ago, precisely due to the lack of instructions, was to use the first set of crossover marks instead of the second when installing them on 502 guy wire strain insulators. They seem to have worked OK, although I did have one insulator to break in two a few years later, but no way to determine if the Big Grip installation had anything to do with it, or if it was a defective insulator. 

The installation instructions I downloaded recommends splitting each leg of the grip into two sections up to the crossover mark before installing them on the cable, and then wrapping each one of the four sections one at at time. This makes the job much easier and the wrapping comes out more uniform, than wrapping them whole legs at a time.
One  precaution I would recommend is to be extremely careful when splitting the legs, since the glue used with the grit material sometimes tends to stay in one piece and pull off one of the sections as they are separated. There is no mention of this in the instructions. I used a knife to help separate the grit material at every first indication this was about to happen.

I  suspect that's the reason PLP recommends discarding a set of grips after they have been removed and re-installed on the cable more than two times; each removal and re-wrapping likely results in some loss of grit material. 

I recently replaced the broken insulator and used a new set of grips (this time using the second crossover mark). I examined the old set of grips, and the grit substance still looks intact. I can't see why they don't recommend re-using grips that have been in place longer that three months, but to be on the safe side I used fresh ones with the new insulator. Perhaps the grit material is somehow compromised after a certain amount of time.

There's another serious problem with the PLP instructions; they are somewhat ambiguous in their explanation of the first and second crossover points, making no specific mention of using them with insulators. I found out the correct procedure the first time, after the fact, only through recommendations from multiple third parties.

Another precaution when using Big Grips with insulators is to make sure the contour of the hole in the insulator closely follows that of the U-bend of the Big Grip. I talked to one of the engineers at PLP about this and he told me there had been several Big Grip failures due to improper insulators. Apparently, "johnny ball" strain insulators are no longer made in USA, and problems have occurred with ones now made in Brazil and China not properly fitting the Big Grip. If the stress of the load is not spread uniformly over entire U-bend, but  concentrated at one or two small points, the brittle nature of the wire used to make the grips may cause stress cracks to appear in the strand, and ultimately, catastrophic failure.

Don k4kyv