Down-to-Earth Rope Longevity Experiment

By Sean Cleary (cleary (at sign) Copyright by Sean Cleary, cleary (at sign), permission granted to reproduce electronically for noncommercial purposes only.
A discussion of rope longevity has prompted me to describe a simple experiment from a few years ago, when some of my partners and I decided to see how much my workhorse lead rope had deteriorated. The rope was three years old at that point and was about at the point where it should be retired as a lead rope and relegated to toproping/seconding use. That is, it had become fuzzy along most of the length of the sheath and was particularly worn and soft at the ends where the figure eights were always tied.

We decided to reproduce the high fall factor tests used by the UIAA as part (and only part) of their certification of new ropes. We didn't have any simple means of measuring impact force, which we would have preferred, but instead just decided to keep subjecting the rope to very high fall factor falls until it broke. That is much easier to do and lots of fun besides.

We found a suitable object, a large piece of pipe, which weighed about 70kg. This is a bit lighter than the normal UIAA 80kg test weight, but it was pretty convenient and is well more than what I weigh with a nice heavy rack and pack full of gear. We tied three harnesses for the pipe out of 1 inch tubular webbing and tied the pipe's harnesses to the "leader" end of the rope with a figure eight follow-through.

The piece of rope we used was a little more than 15 feet long and was hacked off the end of the lead rope. This was the most worn piece of rope; it was very soft and the sheath was completely fuzzed over. With the 8's tied in the ends it was about 13 feet long.

We anchored the other end (the "belayer" end) of the length of rope to a steel and concrete pedestrian bridge. We looped webbing around the bridge and tied the other end of the rope to that loop with another figure eight follow-through.

hauling pipe

We used another rope and a pulley to hoist the pipe above the anchoring point at the bridge to a point as far above the bridge as we could. Thus, we were trying to drop the pipe 26 feet on 13 feet of rope: a factor 2 fall and in principle, the most severe fall that should ever arise in a climbing situation. A fall factor 2 could arise in a climbing situation if for instance the leader climbs up from a belay ledge then falls fully past the ledge before placing any intermediate protection.

Here's what we decided to do:

    Before drop:                  After drop:

   wall                            wall
      ]                               ]
+13'  ] o   <= pipe                   ]
      ] |                             ] 
      ] |                             ]
      ] |  <= rope                    ]
      ] /                             ]
anchor]                      0' anchor]\
      ]                               ]|
      ]                               ]|   <= rope
      ]                               ]|
      ]                        -13'   ]o   <= pipe

Pulley and hoisting rope omitted for clarity/irrelevance.

hauling pipe

The rope held four severe falls. The first fall was actually greater than fall factor 2. The anchoring webbing was inadvertently pulled tight when we were hauling the pipe upwards for the first drop so we dropped it about eight feet further than the 26 feet we were aiming for. So that was really a fall factor 2.5 or so. The subsequent four falls were fall factor 2 and on the fifth fall, the pipe fell to the ground. Actually the webbing that held the pipe broke, even though it was triply redundant. The harnesses were cut at the somewhat sharp edge of the pipe. But nevertheless, the rope was pretty much destroyed by that point. The sheath was completely gone at the end of the bight on the figure eight on the anchor end and most (say 80%) of the strands exposed there were cut. There was a sickening smell like that when you cut the ends of webbing with a hot knife. The harness end figure eight has been impossible to undo!

Overall, I was pleased that the worn rope held a succession of very severe lead falls.

Things to think about:

  1. The fall was held by a figure 8 tied directly to a bombproof anchor. That was where the rope almost broke. In a normal climbing situation, that would have been held by a belay device and thus been more of a dynamic connection point. It would have been significantly more dynamic if the belayer had body weight as part of the belay chain. We didn't get any volunteers to hang out below a massive falling pipe and belay it, though. You'd get jerked around quite a bit and you'd want a pretty serious helmet for that pipe...
  2. I didn't realize that during the UIAA tests, they allow the unweighted rope to "relax" for a few minutes between next drops. We didn't allow any time for the rope to relax. In fact, after each drop the pipe dangled spinning on the end of the rope for a few minutes while I checked the rope and knots. So the rope was only unweighted when we were hauling the pipe upwards, which was not very long at all. Evidently this "relaxing" period is significant as it allows the fibers to return to their normal lengths and it allows the kern to cool somewhat.
  3. This was the softest and most worn segment of a reasonably worn rope. The part near the end takes a great deal of stress from falling since at that point, the climber is tied in and the knot gets very compressed in repeated falls.
  4. The rope probably elongated after each drop. We didn't measure its length between drops but we were of the general opinion that the rope was getting a bit longer each time. It also seemed like a sharper stop each time but again, that was merely our opinion. That would be consistent with my limited understanding of how impact forces are likely to rise as the kern of the rope is damaged further.
  5. The UIAA falls are actually not quite factor 2 falls, more like factor 1.8. The UIAA is a bunch of engineers in a laboratory with equipment meant to study and certify climbing equipment under controlled circumstances who do this for pay every day; we are a bunch of mathematicians and molecular biologists who decided to drop a pipe off a parking garage early one Sunday morning out of curiosity and comedy value. I'd take their opinions and conclusions more seriously than mine.
  6. This is a sample size of 1. Your mileage may vary. We did this experiment principally out of curiosity and that is all that our experiment was meant to satisfy. Your rope is different from that one; it has a different history and care. Nobody can say whether or not your rope will break under any circumstances with great certainty. I would recommend doing this experiment yourself for the following reasons:
You may have to hunt around to find a suitable place to do this. I would not recommend doing this in a climbing area since you may be likely to make a mess/ scar the wall/ break off holds when the rope does break. Also, you don't want to stress a piece of protection that severely unless it's really the security of the piece that you are interested in studying, not the piece of rope. And you don't want to leave a massively stressed-out bolt where someone else may be likely to want to use it for their own security.

The rope was an Edelrid 11mm with a dry treatment. It had been used for three years on regular weekend use and plenty of longer trips, for both cragging and alpine routes. It had never taken a lead fall of any length but had taken many toprope and seconding falls. Its dry treatment had long disappeared and it had been cleaned regularly. It had been soaked thoroughly by gritty glacial snow, rappelled on in thunderstorms when wet and dirty, and it had been dragged across soft sandstone and through dirt-filled granite cracks, etc. When new, it was rated for 6 UIAA severe (fall factor 1.8) falls. So I was pretty happy when it held 4 even more severe falls after 3 years of regular use.

Next time we're bored, maybe we'll see just how well TCU's actually hold...

Sean Cleary cleary (at sign)

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