In a message dated 8/3/2006 9:38:11 P.M. Pacific Daylight Time,
towertalk-request@contesting.com writes:
> 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
perfectly.
Well, not perfectly. The second set of overlap marks are for when you're
putting them over insulators. If you use the first set, the angle of the
Preforms is more acute and puts more strain on the grip strands.
> 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.
Well, you need to observe the LXC Prime Directive to "DO what the
manufacturer says" which is use the 2nd marks for insulators. Unfortunately
this
information isn't widely disseminated or known to amateurs so yours is a
common
mistake. Probably not fatal - but a mistake.
> Supposedly, utility pole guy grips are
unsatisfactory for tower use because they have slightly less length than the
ones designed for tower use.
Not supposedly, DEFINITELY unsatisfactory. The Preformed grips are
precision pieces of hardware and are only compatible with specific cables. For
3/16" wire rope there are 8 or so grades of cable and they're all different;
e.g. different OD, different lay, different number of strands, etc. You can
only
use the grip for a particular cable - no exceptions.
> Wouldn't beginning at the second marks defeat
the advantage of using the Big Grips?
No. The factory knows best.
> 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
sag.
> 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%?
The tension on the guys that you mentioned - 400# - is at 70 degrees F. The
tension varies with the temperature so your observations are correct but
perhaps your tension isn't. A relatively cheap and accurate way to measure
your
tension is with a Loos Tension Meter. They're available from
_www.championradio.com_ (http://www.championradio.com) . I know the owner real
well and
they're a good company to do business with. I'll bet you a nickel that your
tension
is either too high or too low. Without measuring it, you're taking a wild
guess.
Cheers,
Steve K7LXC
Champion Radio Products
Cell: 206-890-4188
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|