There seems to be a bit of confusion about turnbuckle strength so here is
some information for your enlightenment:
The numbers published in hardware distributors catalogs relate to "Working
Load Limit". The distributors have no way to know your application and
publish a number thought to be safe for weight or load bearing applications
in general on a continuous duty cycle basis. Tower manufacturers, such as
Rohn, select turnbuckle sizes based on "Breaking Strength" or "Ultimate
Strength". The 7 strand Extra High Strength guy sizes like 3/16 EHS, 1/4 EHS,
etc. specified for tower guying are all rated for breaking strength so it is
logical to also use the same rating for turnbuckles.
If you will refer to the Rohn Tower Catalog (available from Tower Tech or
Texas Towers) in the Hardware & Accessories section, page number "form no.
88-2200-2R1, you will find a list of popular turnbuckle sizes with their
associated "Ultimate Strength" ratings.
25G model towers typically use 3/8 X 6 inch Eye & Eye turnbuckles with a
rating of 6000 lbs breaking strength (note to Earl Cunningham: I misquoted
this as 4000 lbs as I was reffering to the breaking strength of the
associated 3/16 EHS guy wire). 1/2 X 12 turnbuckles are rated for 11,000 lbs
(appropriate for use with 1/4 EHS guy wire) and generally used with 45G and
55G towers.
One of my distributor references shows an example of a 5 times safety margin
from "Working Load Limit " to "Ultimate Strength". Hence the 3/8 inch
turnbuckle 1200 lb "Working Load Limit" becomes a 6000lb "Ultimate Strength"
rating.
Earl decided to use a turnbuckle shorter than the 11,000 lb. 1/2 X 12 inch
version offered by Rohn but they have the same breaking strength. Does this
hurt anything? The answer is no, except Earls' pocketbook and since it is
his money, he gets to spend it as he sees fit. One thing is for sure: the
last item to fail in his installation be the turnbuckles!
Here is a summary of commonly used turnbuckle ratings:
Size Working Load Limit (WLL) Breaking
Strength Cost
1) 3/8EE (Eye & Eye) 1,200 lbs 6,000lbs
$10.00
2) 3/8EJ (Eye & Jaw) 1,200 lbs 6,000lbs
11.00
3) 1/2X 9EE 2,200 lbs 11,000 lbs
15.00
4) 1/2X9EJ 2,200 lbs 11,000
lbs 16.00
5) 1/2X12EE 2,200 lbs 11,000 lbs
17.00
6) 1/2X12EJ 2,200 lbs 11,000
lbs 18.00
7) 5/8X12EJ 3,500 lbs 17,500
lbs 21.00
All these sizes are readily available from Texas Towers stock. If you prefer
doing business with McMasters-Carr, their stock meets the same Federal
Specification FF-T-791b that our stock meets. You get to pay for the
telephone call, ours is toll free, 1 800 272 3467, You can't get their
catalog (I've tryed), ours is free for calling the 800 # and asking, You
don't have to help finance their teriffic overhead (ours in tiny in
comparison) and you get to talk to a friendly ham when you order from us.
Contrary to what you may have heard, we even ship 99%+ of our orders within
24 hours, usually same day.
73 to all, de Gerald Williamson, K5GW, Owner & General Manager, Texas Towers
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