You MAY - and I repeat MAY - be seeing a difference in the "rated strength"
methods of two different industries.
1/4" EHS is rated at its minimum ultimate breaking strength i.e. 6700 #. It
is known in the tower industry that we apply a "factor of safety" of two to
the design load on the guys per EIA-222. That is if the tower and antennas
put a 3000" load on the guy wire we know we must select a guy wire that
will hold at least 6000#.
Shackles are used in the construction industry. The rating that you MAY be
seeing is "safe working load". This usually has a "safety factor" of 3 to 5
applied to the ultimate breaking strength. It depends on the manufacturer
and the standard under which the shackle is rated. This would say that the
shackle COULD HAVE an ultimate breaking strength of 6000# to 10,000#. You
need to look at the manufacturer's catalog, or call the manufacturer to
determine exactly what factor of safety is included in their rating.
You have to understand the rating system to understand what they are trying
to tell you.
This is kind of like how some people rate towers in ads, only in reverse.
;)
de n0yvy steve
Disclaimer: I and my company agree on at least one thing: My opinions are
my own.
______________________________ Reply Separator _________________________________
Subject: Rohn shackles/T-Bars
Author: AA7BG Matt Trott <aa7bg@initco.net> at ccmgw1
To: <towertalk@contesting.com>
Date: 6/4/96 3:29 PM
Can anyone tell me why Rohn would advise (in their catalog) using 3/8
shackles with their torque bar guy package. I guess my pea-brain just
doesn't understand how some of this stuff is rated. Let's say you're using
1/4" EHS guy cable. This is rated at 6700#. Now if you use the 3/8 shackles
at the torque bars isn't this a "weak" link. Near as I have been able to
find out, these shackles are "rated" at 2000#! I've tried 1/2" shackles, but
the pins are too big to go thru the hole in the torque bar. The reason I
don't just slip the thimble thru the torque bar is that I'm using P-stran
which requires oversize thimbles. I really, really, really doubt that the
3/8" thimbles would ever break, but I just don't understand the rating
differentials of 6700# vs. 2000#. It just bugs me, man.
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AA7BG aa7bg@3rivers.net Matt Trott
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