Rope Comparison

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Rope Comparison

Postby ndonaldj » Apr 6, 2012 4:28 pm

Along with compiling a list of locking carabiners, I have made a google doc comparing static ropes.
https://docs.google.com/spreadsheet/ccc ... 3ctQmtEcVE

I don't know what the best way to attache it would be, Its in a google doc spreadsheet. I tried attaching a screenshot for easier viewing, but its telling me 'It was not possible to determine the dimensions of the image'. So I hope the link is good enough.
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Re: Rope Comparison

Postby PeterFJohnson » Apr 6, 2012 5:35 pm

I was able to access the document.

Out of curiosity, at what weight or %MBS are the elongation figures you listed?
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Re: Rope Comparison

Postby ndonaldj » Apr 6, 2012 5:41 pm

They are all listed at 300lbF, I'm not sure why I haven't specified that.
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Re: Rope Comparison

Postby PeterFJohnson » Apr 6, 2012 6:46 pm

Did you have to calculate that from various manufacturer's data?Is the relationship between elasticity of rope and load roughly linear?
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Re: Rope Comparison

Postby Bob Thrun » Apr 6, 2012 9:04 pm

I wonder about the data. It would make a good technical article if you gave sources. Each manufacturer seems to give elongation data differently, if at all. To get the stretch at a given load, you need to find elongation curves. I found only one manufacturer that gives curves for all its ropes. The curves are printed so small that it would be hard to pick off 300 lbs on a curve that goes to 6000 lbs. There is some hysterisis, a rope does not shrink all the way back to its original length after being unloaded. Some manufacturers give the stretch at 15 % of the breaking strength.

You have some ropes listed as having a Technora sheath and nylon or polypropylene core. It is usually the other way around, with a Technora core. The Technora/Technora combinations are shown as having more stretch than nylon/nylon. Technora has extremely low stretch while nylon has the most stretch of the fibers listed.
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Re: Rope Comparison

Postby chh » Apr 7, 2012 8:38 am

Bob Thrun wrote: The Technora/Technora combinations are shown as having more stretch than nylon/nylon. Technora has extremely low stretch while nylon has the most stretch of the fibers listed.


I noticed that as well, which can't be right. I also find the lack of a more standardized method of elongation testing annoying. Lacking that companies could still test however they wanted, but provide the data you know?
Your words of caution are no match for my disaster style!
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Re: Rope Comparison

Postby Bob Thrun » Apr 7, 2012 1:06 pm

Yale Cordage publishes elongation curves for all its ropes. It makes a Technora/Technora rope called Tech-Kern. It is sold as a high temperature rappelling rope. The fiber decomposes at 800 deg F. At that temperature aluminum would soften. Tech-Kern is made in only one size, 11.4 mm, which is close to the sizes in the table that ndonaldj posted. The fiber is denser than nylon, so the rope weighs 7.6 lbs per 100 feet. It has an average breaking strength of 21,000 lbs. The 300 lb standard is 1.4% of the breaking strength. I am copying the published elongation curve. The colored area under the curve is energy absorption. It is hard to read, but it looks like there is 0.1% elongation at 300 lbs.

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