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[TowerTalk] hoisting cables

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Subject: [TowerTalk] hoisting cables
From: (
Date: Thu, 19 Aug 1999 12:07:17 EDT
In a message dated 99-08-18 07:33:28 EDT, writes:

> What is the major difference between "wire rope" and "aircraft" cable? It
>  seems to me that aircraft cable would require the survivability of
>  flexing many, many more times than the occasional use that is required on
>  a tower operation. It's hard for me to believe that the big, bad boy
>  lifting machines use aircraft or stainless cables.

      In general, wire rope refers to those products that consist of metal 
strands laid in bundles that make up what we call cables, guy wires, etc. 

      There can be as many as 8 different grades of wire rope for a 
particular wire size ranging from low strength to EHS (extra high strength). 
And they all have different materials, configurations and applications. SS 
aircraft cable is just one grade of cable. 
>  Do we typically consider the safe working load to be 10 percent of the
>  claimed breaking strength of the cable? 

      I've seen safe working loads from 10% to 25% of the ultimate breaking 
strength. It depends on the cable and the application.

      Guy wire tension OTOH does use 10% of the UBS as the standard tension. 

> Is that about the same rule of
>  thumb that is used in prestressed guy wires? 

      You don't normally run across prestressed guys in amateur 
installations. What context are you using 'prestressed guy wires' in? 

>  Is stainless worth the cost differential for longevity verses lowered
>  ratings?
       I would say "probably". I suspect that the reason that crank-up 
manufacturers haven't used SS cable is because of the cost. Tom, N6BT, of 
Force 12 who has recently taken over the Tri-Ex crank-up line said that he 
will be using SS cable in all of their crank-ups. But you'd have to talk to 
the manufacturer about the adviseability of substituting materials on their 

      I recently wrote a multi-part series on guy wires that covered most of 
these topics. It appeared in my "Up The Tower" column in CQ Contest magazine. 

Cheers,   Steve    K7LXC
Tower Tech

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