[TowerTalk] Phillystran Tension Gage

[R. David Eagle]

 This is a good discussion!  I have learned alot so far!  I did a little digging around and I think I am going to rig up a deflection gizzmo to measure the tension and see how it turns out.  I have some spare phillystran so a test rig is in order.
Thanks to all...
DaveKB8NNU

    On Tuesday, July 13, 2021, 10:56:57 PM EDT, John Simmons <jasimmons at pinewooddata.com> wrote:  
 
 Grant (and all),

This thread is getting really interesting to me. I'm certainly no 
mechanical engineer but I'm beginning to understand how these things 
work and can certainly see what the Loos gauge issues are with Kevlar.

So, having looked up S-type load cells and Dillon force gauges, I have a 
couple questions. 1: How does one put a gauge inline with the guy, set 
the tension and then remove it and restore the same tension? The S-type 
load cell is basically a Wheatstone bridge, so what is the 'excitation' 
voltage required? Some 'cookbook' style instructions would be very helpful.

I say all this because I'm one of the schmucks that ran his Philly all 
the way down to the anchor. This summer I plan to change the HF Yagi at 
the top of my 80' 25G to one with much more torque from wind force and 
want to make sure the guy wire tensions are correct.

73,
-de John NI0K

Grant Saviers wrote on 7/13/2021 6:46 PM:
> 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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