Topband: Ends for older Phillystran

[Grant Saviers]

Thanks to all who provided info and suggestions.

I plan to run some tests, starting with a modification to my 20T "H" 
frame press so I can tension test specimens up to 10k lbs or so and 
measure force with a simple Dillon mechanical 5k# force gauge I have.  A 
lever arm will give me 2x and maybe 4x tension.  I've also talked with 
West Coast Wire Rope and Rigging here in Seattle, they have a 5k to 
500k# pull stand for up to 180' long cables that costs $150 per test 
hour.  6 to 8 tests can be run in that time for short/small cables (my 
home test samples will be 4 to 5' long).  If I can't break a test 
specimen, then they will.  With my press setup I can leave the tension 
on for a few days and check for slippage and cycle the test to some max 
tension value.

It appears that one solution to be able to use "old" Phillystran is to 
use wire rope clips and HD thimbles at the right quantity and tightening 
torque.  So, I plan an experiment with differing numbers of clips, 4 to 
6, and tightening torques (5/8" clips) from 35 to 95 ft-lbs (95 is the 
recommended wire rope value).  I think 3/4" heavy duty thimbles are the 
correct size for all experiments.

So the plan is to test 3 "corner conditions" assemblies to 10k# then to 
20k# (if I can), measuring the slippage or failure each time and then 
pull test whatever survives to failure at WCWR. (I hope I can watch!)

Since "new" Phillystran (11.2k# vs what I have is 45k#)  will set me 
back well over $4k for this tower (65G, 150'), this seems a reasonable 
way to find out if what I have can be made reliable for $200 of steel, 
clips, and some welding.

So, if you know more about designing a such a test or clips on 
Phillystran let me know.

Tom's multi-turn wrap termination is an interesting idea, it works for 
line and monofilament on fish-hooks.  Any suggestions on what the 
"thimble" would look like?  Kevlar is bend radius sensitive and fatigue 
prone.

Grant KZ1W

On 1/14/2014 7:54 AM, Tom W8JI wrote:
> I would never design and especially never test for the maximum steady 
> working load at a wind speed. The shock load of a bounce can strip the 
> ends. I had a friend who lost a tower from a straight line wind in a 
> normal thunderstorm because the outer layer stripped off. He used 
> three saddle clamps. I told him he should have wrapped the insulator 
> (he used insulators to transistion to steel) two or three turns before 
> clamping.
>
> This is not much different than getting hold of copperweld twinlead, 
> or anything else with a soft outside and hard core.
>
> Has anyone thought of a long rectangular bar with multiple champhered 
> holes, with the Phillystran woven through from side-to-side? With 
> enough weaves, this should self-tension with just a single clamp on 
> the far end. Regardless, I would test pull and see what breaks first 
> at what tension.
>
> 73 Tom
> _________________
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