Topband: Ends for older Phillystran

[donovanf at starpower.net]

Another alternative is to wrap two turns of the Phillystran around a short length of three inch diameter steel pipe or tubing. 
Then pass a large shackle through the tubing to fasten it to the steel cable. 
Cut the tubing to fit the shackle, so that the Phillystran can't slip off the end of the tubing. 

73 
Frank 
W3LPL 

----- Original Message -----

From: "Ashton Lee" <Ashton.R.Lee at hotmail.com> 
To: "Tom W8JI" <w8ji at w8ji.com> 
Cc: n2ic at arrl.net, "Bill Wichers" <billw at waveform.net>, "Group Topband" <topband at contesting.com> 
Sent: Tuesday, January 14, 2014 7:11:06 PM 
Subject: Re: Topband: Ends for older Phillystran 

As a very crude analogy what you want to be able to do is use a steel cable from the anchor through the middle of something like an automobile wheel, Then the Phillystran wants to take a couple of lazy turns around the rim of the wheel and then get clamped to itself. While there are probably better engineered alternatives to the auto wheel the idea is that the turn be of a large smooth radius and have a high total friction such that the clamps don’t actually hold against much pull. 

If you look at old sailing ships that’s how they are rigged… with big wooden thimble blocks. 


On Jan 14, 2014, at 12:02 PM, Tom W8JI <w8ji at w8ji.com> wrote: 

>> The bar idea would probably significantly reduce the allowable tension on the cable, similar to what knotting does, due to the force at each "bite point" weakening the cable. I suppose if the cable was sufficiently oversized this wouldn't pose a problem, but I'd certainly expect such a clamping method to effectively reduce the allowable tension significantly below the normal rated load. 
>> 
> 
> I wouldn't do anything as tight as a knot, especially when both surfaces have significant yield. The holes would have to be chamfered to prevent cutting through the jacket. It wouldn't be much different than an insulator if done correctly. It is all about not making the short turn radius a knife. 
> 
>> I'm actually a little surprised a dead end / preform isn't supposed to be used with the straight-strand version of the cable. Those grips work by compression of the cable they are "grabbing", and it's a fairly even pressure over the length of the gripped area. If one could be found that was the correct diameter for the cable being used it might be worth a shot, but I completely agree with Tom -- TEST ANYTHING YOU TRY BEFORE USING IT FOR REAL! He's also correct that dynamic loading is much worse than static loading. Wind causes vibration in towers and guys and that can cause your clamps to loosen over time, especially if they were marginal to begin with. 
>> 
> 
> There has to be considerable pressure on the jacket squeezing it into the inner fiberglass. I'd be reluctant to use a grip on something that has a tendency to slide. I don't think it will squeeze hard enough. The newer Phillystran has much less tendency to have the jacket slide over the center. 
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