Rope Pad testing

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Rope Pad testing

Postby Scott McCrea » Nov 22, 2005 9:47 am

Below is a thread about rope pad testing from the previous NSS Discussion Board.

If you would like to find other threads/posts from the previous NSS DB go here:LINK



  #1  
03-12-05, 05:14 PM

Scott McCrea

Rope pad testing

Since the Rope cutting thread mentioned rope pads, I thought I'd post a link to some info on rope pad testing.

http://www.hse.gov.uk/research/crr_htm/ ... r01364.htm

Basically, it says that canvas was the best material they tested. They did not test fire hoses. Interesting stuff.
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Scott McCrea
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NSS 40839
Flittermouse Grotto
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  #4  
03-13-05, 09:34 AM

RescueMan

Quote: Originally Posted by Scott McCrea
Basically, it says that canvas was the best material they tested. They did not test fire hoses.


Oddly, they didn't test wool carpet, only nylon. And the best protection, by far, was by roller-type edge protectors.

They also tested only for cyclic vertical movement over an edge (rope stretch), not for lateral (sawing) motion.

An interesting finding was that, while edge pads generally helped on very sharp edges, on more rounded edges they accellerated wear of the rope (likely from heat generation).

- Robert
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  #6  
03-13-05, 04:23 PM

Ralph E. Powers

Thanks, that link worked better. The results and report (read half of it so far) are fascinating and worth reading. A lot of it was Greek but it wasn't written so technical that it was totally drowning me in jargon.

The report seems to reflect testing on different items and much of it we use, and the knots section was good to read about. The caver favored figure 8 knot held up well under their tests. Likewise the joining of two ropes together; double -fisherman (my personal favorite to use) seemed to be the strongest. Though I've never had a problem untying the knot after use. Seems that regular caving rappelling/ascents don't put as much of a load on it as they were during testing.

I've long used carpet pieces because they're easy to obtain and abundant. In-so-far I've never experienced wear and tear as the report shows even over a particularly craggy lip surface as roughened limestone. Again it seems that we (cavers) aren't placing as much wear and tear on the equiptment during normal use. Rescue usage I would imagine would be much higher.
On one occasion I've used the petzl edge rollers and found them to be very helpful. One of our party brought them along for "the just in case" and the "case" happened. The rollers performed well and were most helpful in our hauling the exhausted caver out of the entrance pit.

This report makes for good reading and important for all of us (vertically inclined) cavers. Two bats up.
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  #7  
03-14-05, 03:48 PM

RescueMan

Quote: Originally Posted by Ralph E. Powers
Rescue usage I would imagine would be much higher.


While the testing procedure (cyclic vertical movement of 50mm at 5 cycles per minute) was somewhat arbitrary, it was meant to approximate the rope stretch caused by a single person moving up or down or working on rope.

This research report looked at Personal Protective Equipment for Rope Access, which is professional work at heights and is very similar to what we do in caves: descending, ascending, and stopping to work along the way. It was NOT testing for rescue loads.

The test weight was 87 kg (191 lbs), to approximate one person with equipment. So I would think their results are VERY pertinent to the cave environment.

An interesting point they raised (but did not test for) was that an anchor far from the lip would cause more rope stretch at the edge but would also then spread the friction area out to more surface of the rope. This begs the question of whether there would be more or less wear in this case (they seemed to suggest it would be less).

- Robert
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  #8  
03-14-05, 06:24 PM

Ralph E. Powers

Quote: Originally Posted by RescueMan
An interesting point they raised (but did not test for) was that an anchor far from the lip would cause more rope stretch at the edge but would also then spread the friction area out to more surface of the rope. This begs the question of whether there would be more or less wear in this case (they seemed to suggest it would be less).


Okay, well I did say it was mostly greek to me so I was not realizing the paraelle between their tests and our caving. So okay, I look at the paper with a new perspective.

As far as rope wear over an longer surface area, I've had the experience where a rope was rigged over a 300' free-hanging drop (whoo hoo!) and there's a (seemingly) smooth ledge some fifty feet below where you get on rope and the anchor point. This spot had never been reported as a bad rub spot before.
On the ascent back up myself and another caver tandemed up the rope. He called down something that was disturbing. When I reached the spot I noticed some wear on the sheath of the rope we were on (PMI maxi-wear).
I looked at it closely and while it showed signs of some fuzzing the rope was still relatively intact... (my ascenders were above the rope and enabled me to pull the wear spot up and look at it more closely.
The next couple of cavers also tandemed up as we exited the cave. They were too far down and deeper (elsewhere) in the cave to hear anything (coherently) and we were getting cold.
Turned out that when the other two tandemed up the rub-spot had severely worn the rope down to the sheath was totally gone and the inner strands were showing. Scared the crap out of the first guy for sure.
The caver below managed to somehow get his weight off the rope enough for the top guy to haul up and tie a knot in the rope where it was worn away.

Thoughts on this was that myself and the caver I tandemed with were using rope-walker/double bungee systems. The two behind/below us were both using frog systems. It seems that our "rope walker" systems didn't put as much bounce on the rope as the frogs did. They told me that they were doing the "one on one off" method, which I believe is that the top climber goes up so many odd feet, sits and rest and the bottom climbs up til he almost touches the boot soles of the top guy. While this puts continual bounce on the rope it at least reduces the stretch had both of them climbed simultaneously. Either way this spot was now re-rigged and re-belayed. A close call for sure but puzzling that the usual spot all of the sudden starts getting "hungry". It's possible that the rope shifted off the smooth area during the first tandem. Many cavers had climbed on this spot before without protection because it was smooth/slick flowstone. Seems that it's not as smooth as we first thought.

Scott McCrea
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