[TowerTalk] Phillystran Tension Gage

[K9MA]

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 at 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 at 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 at 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 at sdellington.us