[TowerTalk] Installing Big Grips

[K8RI on TowerTalk]

> 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

If you are refering to wrapping the individual metal strands, step wise 
fashion no additional clamps are needed. That is about as neat and stong a 
connection you can get. U-bolt clamps in general form a spot that is 
slightly weaker than the adjacent cable.


> 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.

I've had several shipments of the things and so far as I recall each 
shipment came with a data sheet. The sheet was with the rest of the 
paperwork as I recall.  HOWEVER I received the guyline in the same shipments 
and the information for the Big Grips *may* have come with the guy line 
instead of the Big Grips themselves.
>
> 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

Some Big Grips have two marks, mine in both sizes _only_have_one.  The marks 
are to aid in the wrap starting point depending on the size of the thimble, 
or insulator.  Larger thimble or insulator needs the wrap to start farther 
out.

To answer the one question, which I accidentally snipped, Yes, starting the 
wrap too close to an insulator so that the Big Grip "pinches" the corners of 
the insulator can cause stress. With insulators being some what fragile it 
is something to be avoided as any additional stress is an additional point 
for failure.  When that stress point becomes... well... a point the 
likelyhood of failure goes up.

Of course that is why insulators are designed so that should the insulator 
fail completly the two cables are still in a fail safe configuration with 
each looping through the end of the other.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from home page)
>