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[TowerTalk] ratings on wire rope

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Subject: [TowerTalk] ratings on wire rope
From: (N2TK)
Date: Mon, 3 Sep 2001 19:32:26 -0400
I am using 1/4" wire rope to tilt over my tower. When my tower is near the
ground I have a maximum pull of 2900 lbs. on the pulley. Since I am going
through a single sheave on the gin pole from a winch, I assume that the
maximum pull on the pulley is 2900/2 = 1450 lbs.

I understand that 1/4" wire rope has a breaking strength of 7700 lbs. I have
heard that you should take the breaking strength and divide it by 3.5 for
the load rating - 7700/3.5 = 2200 lbs. I would think this would give me an
okay safety rating?? Comments?

However, one wire rope company told me that when you use cable clamps on the
end of wire rope it reduces the strength by 20%. Was also told if you have
the end of the wire rope "weaved" over a thimble, then strength of the wire
rope is reduced by only 5%. Is this correct?

If I am losing 20% strength of the wire rope then,
7700 x .8/3.5 = 1760 lbs. Is this cutting it too close? Comments please.

If I have the cable company weave the end then,
7700 x .95/3.5 = 2090 lbs.

Is either method sufficient, or should I be looking at 5/16" wire rope?


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