[TowerTalk] Phillystran Tension Gage

[Grant Saviers]

Calibrating against the actual fiber is *probably* good enough for ham 
tower work, BUT

Be aware that the Kevlar fibers of Phillystran behave very differently 
than steel wire.  The Kevlar fiber is very strong axially with about 60% 
the modulus of steel.  The fiber also has very complex lower modulus 
behavior longitudinally, the fibers are anisotropic.

The Loos gauge is based on the isotropic (equal in all directions) 
modulus of steel, approximately the deflection of a beam center loaded 
and simply supported at both ends.  A simple equation that can be looked 
up on the web, that doesn't apply to Phillystran.

If the Kevlar "beam" was isotropic, then the Loos gauge on Kevlar would 
deflect 1/0.6 more on the same diameter as EHS (IE the exact diameter of 
the actual fiber or wire bundle if all air was removed - weight per foot 
is the easiest means to get the value for both).  A 0.22" diameter of 
the PE Phillystran sheath, isn't that value.

So perhaps the best use of a Loos gauge is to get all guy tensions equal 
and use a simple force gauge to measure the tension.  Sometimes cheap on 
ebay ("dillon force gauge") and all mechanical (D shaped steel ring and 
dial gauge).

They can be made on a milling machine, google for instructions.  Like 
these.  They work in tension or compression.

https://scienspec.com.tw/userfiles/files/MODEL%20X.PDF

Grant KZ1W


On 7/13/2021 14:43, n0tt1 at juno.com wrote:
> Kurt,
> 
>> Perhaps, and I don't know,
>> does Phillystran require something more complex, and specialized than
>> any other material under tension that fits in the gauge?
> 
> Not really.  The guage should be calibrated for whatever cable one
> intends
> to measure.  It's that simple.
> 
> 73,
> Charlie, N0TT
> 
> On Tue, 13 Jul 2021 12:27:43 -0700 KD7JYK DM09 <kd7jyk at earthlink.net>
> writes:
>>
>>> After searching far and wide to come to the conclusion there is
>> none
>>> commercially available, I built my own tension gauge
>>
>> I'm super confused here.  I haven't looked for tension gauges since
>>
>> putting up my own mast in 2013, and haven't looked again until a few
>>
>> moments ago.  I got 22.71 million hits for sites, and enough pics to
>>
>> choke the internet, with tension gauges ranging from small handheld
>>
>> models for string, to gauges for suspension bridges, most in the
>> range
>> of anything any of us would ever use, wire, rope, cable, you name
>> it.
>> If price is a concern, and it's a one-shot deal, look at belt
>> tension
>> gauges at an auto parts store.  Even the companies that supply bits
>> and
>> pieces for our hobby, supply the tools, and gauges to install, test,
>> and
>> use them (look up guy wire tension gauge, or cable tension gauge, or
>>
>> even rigging gauges if you're into boating).  Perhaps, and I don't
>> know,
>> does Phillystran require something more complex, and specialized
>> than
>> any other material under tension that fits in the gauge?
>>
>> Kurt
>>
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