thanks for passing this info along!
Sam N5FO
From: Dick Green WC1M
Sent: Saturday, October 22, 2016 1:23 PM
To: 'Donald Chester', towertalk@contesting.com
Don,
Could you post a copy of your conversion chart?
Below is my conversion chart for my 110' Rohn 555 tower, which uses
HPTG67001 Phillystran guys with 1/4" EHS leaders from the guy anchors to a
level that's about 15' off the ground (to protect against vandalism, brush
fires, etc.) The guy lengths vary with height and direction because my tower
is on a steep hill, but the EHS portions are 29' on two sides and 37.5' on
the remaining (downhill) side, or roughly 20%-30% of each guy length.
I calibrated the Loos gauge against a Dillon dynamometer attached in line
with the EHS portion of the actual guys using a Klein grip and come-along.
Loos Loos Dillon
Reading Chart Reading
26 450 300
27 500 400
30 660 450
31 720 500
32 780 600
33 840 660
34 900 700
35 1000 765
36 1100 850
37 1200 1000
73, Dick WC1M
-----Original Message-----
From: Donald Chester [mailto:k4kyv@hotmail.com]
Sent: Saturday, October 22, 2016 12:29 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Guy Tensioning
> The Loos gage from Champion is easy to use to adjust the tension. In my
case 10 % of the 4,000 lb rated cable and phillystran.
> Fred KC5YN
I use the better grade Loos gage for my 3/16" guys. Well worth the cost.
The calibration chart that comes with the instrument is correct only for the
19-strand wire rope it was designed for, which is what they use for sailboat
rigging. The stiffness of the cable determines the reading as much as does
the tension. The chart that comes with the gauge is WAY off and totally
useless for EHS guy cable. I'm sure it would be just as far off, if not
more so, with phillystran.
I made up a conversion chart by purchasing a few feet of the exact type of
19-strand rope the gauge was designed for. I attached the wire rope to a
piece of 3/16 EHS guy cable, using a small strain insulator and a couple of
cable clamps, and strung the whole thing between two trees, with a
come-along and a turnbuckle at one end. I tightened the cable in increments
with the come-along and fine-adjusted the tension reading with the
turnbuckle, at each step recording the tension of the 19-strand rope
according to the Loos chart, then moved the Loos to the EHS and again noted
that reading, and thus made up my chart. With the two pieces tied together,
they both have the same tension, so the tension reading on the wire rope has
to be the same as the tension on the EHS, thus allowing me to make up an
accurate chart for 3/16 EHS. That same procedure would work equally well
with phillystran; I would make up a separate chart for each.
Before acquiring the Loos I had always tensioned my guys by feel and by
eyeballing the sag. I was amazed how poorly that had worked and how
non-uniform the tension was between different levels of guys.
The only time I ever set the tension all the way to 10% of breaking strength
is in winter when the temperature is in the 20s or less. You might not
believe how much the ambient temperature affects guy tension. If they are
tensioned to 10% on a warm summer day, the entire guy system will be grossly
over-tensioned when the temperature drops to single digits. I think of 10%
as the maximum tension to be reached with temperature variations, not as the
normal operating tension. Since my 127' of Rohn 25G is used only as a
vertical radiator and to hold up a single dipole, there is not a lot of wind
loading, and I don't think the guy wire tension is all that critical.
Don k4kyv
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