Re: [TowerTalk] Phillystran Tension Gage

[K9MA <k9ma@sdellington.us>]

I can't find it now, but a couple years ago I found some calibration 
data comparing the Loos PT-2 on 3/16 EHS compared to the SS wire rope it 
was designed for. I recall that the PT-2 read perhaps 10 percent high on 
the EHS. (The true tension was lower than the PT-2 indicated.) Since EHS 
is very stiff, that makes sense. However, K7LXC, in "Up the Tower", made 
a similar measurement, and found little difference in the readings. 
These measurements were all made with a piece of 19 strand 3/16 SS in 
series with 7 strand EHS and a commercial tension gauge.
If anyone succeeds in finding those measurements, let me know.

My Phillystran guys have the usual EHS tails near the ground, so I just 
measured the tension on the EHS. I'm not sure why anyone would want to 
use Phillystran all the way to the ground.
73,
Scott

On 7/25/2021 10:01 PM, n0tt1@juno.com wrote:
> It's all about the diameter of the wire under test and the
> amount of deflection when the mechanics of the Loos presses
> on that wire to deflect it between two points on the instrument.  The
> amount of
> deflection is indicated on the Loos dial which is calibrated to read
> tension.
> Different diameters of flexible cable will cause the Loos to read
> differently
> even if the tension is the same.  So the Loos, and similar gages,
> should be calibrated for the cable to be tested.  Note that the usual
> guy wire like 3/16" EHS will read differently if a tension gage is
> rotated about the axis of the wire.   That's because the wire isn't
> perfectly round due to the standing.
>
> Charlie, N0TT
>
> On Sun, 25 Jul 2021 13:04:06 -0700 Ken Alker <ka6ken@alker.net> writes:
> > If my conclusions are correct, the chart appears to be based upon the
> >
> > breaking strength of a different type of wire than one would use for
> > a
> > tower.  The chart appears to be based upon stainless steel cable
> > (for
> > sailboats) rather than zinc coated cable (for towers).  The SS cable
> > has a
> > higher breaking strength, hence, using the Loos would mean one would
> >
> > over-tention the guys on a tower if using the % scale, rather than
> > the LBS
> > scale.
> >
> > --On Sunday, July 25, 2021 3:49 PM -0400 john@kk9a.com wrote:
> >
> > > Why are you concerned with the Loos gauge's breaking strength
> > chart?  I
> > > just use the table to set the guy wires to the recommended
> > tension
> > > (usually 10% of its breaking strength).
> > >
> > > John KK9A
> > >
> > >
> > >
> > > Ken Alker ka6ken wrote:
> > >
> > > I'm new to this, but did a lot of research and found that the Loos
> > PT2
> > > appears to be calibrated for wire with a breaking strength of
> > 4545-5000
> > > lbs, while the Rohn 3/16EHS500 wire has a breaking strength of
> > 3990 lbs.
> > > I  assume, based on specs on various types of wire rope found at
> > > <http://www.wcwr.com/catalog/webcat.pdf>, that the Loos PT2 is
> > calibrated
> > > more for 1x19 Stainless Steel type 304 wire rope used for
> > sailboat
> > > rigging  (4700 lbs) rather than zinc coated 3/16EHS500 (3990 lbs).
> >   Here
> > > is my math  based upon the chart found on the Loos gauge (from the
> > web
> > > site quoted by  Tim, below):
> > >
> > >   LBS   %  LBS/%
> > > ----  --  -----
> > >   240   5  4800
> > >   300   6  5000
> > >   420   9  4666
> > >   500  11  4545
> > >   640  14  4571
> > >   840  18  4666
> > > 1030  22  4681
> > > 1240  26  4769
> > >
> > > In conclusion, perhaps one should pay more attention to the "LBS
> > TENSION"
> > > portion of the Loos chart than the "% BREAK STRENGTH" if using the
> > Loos
> > > for  3/16" EHS (assuming it deflects in the same way that the
> > sailboat
> > > wire rope  deflects), or one may overtension their guys.
> > (Although,
> > > perhaps the error  when tensioning to 10% of breaking strength
> > when
> > > tensioning to 400lbs, or  600lbs in the case of Phillstran, isn't
> > big
> > > enough to worry about?)
> > >
> > > Even then, however, I'm very curious as to why the Loos numbers
> > are all
> > > over the map (4545-5000) rather than consistent at one breaking
> > strength;
> > > it is not just rounding error since their "LBS TENSION" appears to
> > be
> > > +-10  lbs.
> > >
> > > Ken, KA6KEN
> > >
> > > _______________________________________________
--
Scott  K9MA

k9ma@sdellington.us

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