In a message dated 97-03-25 19:03:17 EST, firstname.lastname@example.org (Steve Zettel)
> I'll be using 3/16" EHS for guywire and the 3/16" preformed big grips at
> the terminations and insulators. Can the 500D insulators be used with the
> 3/16" big grips, or is it necessary to use the bigger 502 size insulators?
> I know the 3/16" big grips will physically fit through the holes in the
> 500D and the compressive strength of the 500D is, I think, 10,000 lbs, but
> something is telling me I read to use the 502. I just can't remember where
> or what the source documentation would be. Looking at the 500D with a
> big grip threaded through, the bend radius of the insulator that the big
> grip runs over looks kind of small (without tension on the big grip, it
> doesn't come close to conforming to the insulator radius).
I'm still trying to track down more definitive info on porcelain
insulators but the 502 is rated at 10,000 pounds which is kind of overkill
for 3/16 EHS. On the other hand, they're not that expensive. I'm not sure
about the 500 yet.
> Second question, again concerning 3/16" preformed big grips, and thimbles.
> I have 5/16" heavy duty galvanized thimbles that are specified for use
> 3/16" preformed big grips. Again, holding one of the thimbles inside the
> eye of the big grip and squeezing the grip closed by hand so the legs of
> the grip cross where they would when threaded onto the guywire, the fit is
> sloppy loose to the point that I can't see what would keep the thimble in
> the eye of the grip before tension is applied to the guy. Granted, the
> shackle or eye of the turnbuckle passing through the big grip and thimble
> would keep the thimble from falling completely out, but if the thimble
> to get canted or misaligned in the big grip before tension were applied,
> and then a 400 lb strain were taken on the guy, I could see there'd be
> ned to pay. The 5/16" thimbles I have on hand are 2 1/2 inches from the
> tips of the open end to the outside diameter at the top of the closed end
> and 1 3/4 inches across the widest part of the eye. They are, of course,
> 5/16 inches wide across the channel the big grip lays in. Is this the
> "right stuff"?
For 3/16 inch Preforms, the factory spec for thimble size is 7/16 to
3/8 inch. The purpose of the oversized thimble is to maintain the proper
Preform termination radius. As far as a loose fit, yes - they are not
automatically held in position. You can either flip the thimbles into place
during final installation or use a little electrical tape to hold it in
place. With the weight of your finished guywire (EHS, Preforms, insulators,
etc.) it'll be fairly heavy so once the thimble is flipped into place, it
should stay there while you do the initial tensioning.
The Preforms come with 2 crossover marks that are painted on. The
first one is for a normal thimble installation. The second set of crossover
marks is to be used when installing it through an insulator; this gives the
Preform a gentler angle off the insulator and less stress on the device. Be
sure to follow this spec.
BTW, rotator selection is a whole 'nother discussion. And you haven't
even mentioned the mast yet. Lots to do and decisions to make.
73 and GL, Steve K7LXC
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