Rope Breakage Research
- Thread starter Bart_
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ghostice
Been here a while
Thanks for the clip. I have written on Buzz before that folks that work at height should go to their local Alpine Club sections or rock climbing clubs when they run a practice belay session using dummies to make fall arrests - everybody doing this the first time will be surprised at how violent things can quickly get, even with a relatively low fall factor on a modern dynamic line. Add in a static line like arborists use and yikes. As with negative rigging I suppose, it's not only the weight of the piece that makes things scary quickly - it's the distance of the fall (acceleration is after all a squared variable). Stay safe out there.
Knotted strength is less, and it didn't break at the knot so that checks out. The part that broke is out of frame so we cannot see if it broke at another knot, a bend over a lip, or a different form of termination.
bobs yeruncle
Participating member
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- Golden Horseshoe
yeah, as the woman notes it is intended for use securing a static load and not intended for dynamic loads like fall arrest.
in the video they show a clip of a mountaineer falling on a rope into a crevasse, but the environment there acts as an energy damper as we see the rope cut into the packed snow along the edge of the crevasse. it's unclear whether the rope in that clip juxtaposed with the drop test is meant to show the same cordelette they test and how it is meant to be used in practice (personally i suspect not). hard is easy is a rock climbing youtube channel, not an alpinist or mountaineering youtube channel. was it a reasonable clip to use? i can't say
consider that dynamic ropes used in rock climbing are energy damping via stretchiness, meant to safely catch a climber taking a fall of up to a few metres. static climbing ropes used in arboriculture are low-stretch for efficient access at height and work positioning. setting aside bonking into obstacles, flailing cutting tools etc etc and imagining a fall from an anchor point into open space, a fall that a rock climber could safely repeat again and again on a dynamic rope would be much more dangerous, potentially deadly for an arborist on a static rope because the energy from the fall isn't dissipated by a stretchy rope and belayer. there is a significant safety factor built into arborist rope meant for life support to take into account knotting, bends over equipment and branches, wear and tear during typical service lifetime, but they aren't actually designed for safe fall arrest. cordelette is used in relatively short lengths for building floating anchors, and not for fall arrest. like any climbing discipline alpine mountaineering has its own history, culture, and standards which won't necessarily align with other disciplines like rock climbing, rope access tech, arboriculture, as we see from the guy in the video, a rock climber, being disturbed that anyone would consider the 6mm cordelette ok to use. but 'use by whom, and for what?' are important questions to keep in mind imo.
That is unrelated to breaking strength, it just means that the impact force of a given fall will be higher. A dynamic rope with an ideal breaking strength of 14 kN will also break below that with a knot in the system, or when bent over an edge.
ghostice
Been here a while
And I have always wondered about the climbers paradigm that, to a rope, anything with a bend radius of less than 4X the rope diameter or whatever it exactly was, IS a “sharp” edge, yet as we go to thinner and thinner ropes and smaller/ thinner biners maybe the ropes will see more of a sharp “edge” in a fall? The biner may pass a static strength test, but what effect on a spaghetti rope in a fall? To an old guy, much of the new style gear seems to cut down somewhat on the “margin” we had - in abrasion a rope could stand or whatever. In engineering, we can cut down on corrosion allowance in a design, but down the road . . . . ? My two cents.
A common view is that if it passes the UIAA drop test it has adequate margin. A minimum five 1.78 fall factor drops with a rigid 80 kg mass and a rigid belay, in comparatively quick succession, is an extremely harsh test. A carabiner with a somewhat smaller yet smooth radius than the 5mm test spec is unlikely to reduce performance as much as a yielding human body will increase it, and nobody is going take five falls in a row like that. Documented rope failures in actual use always seem to involve cutting, chemicals, neglect, or misuse like via ferrata without an absorber. One exception that comes to mind is a fairly recent accident where the rope was pinched producing an extremely high fall factor, much like the via ferrata case, but not by way of what many would consider misuse.
Of course people are going to have different expectations about safety margins and the safety of the activity in general. It is also worth considering that heavier climbers have a lot less margin than light climbers when using the same equipment.
ghostice
Been here a while
Maybe drifting off topic a bit, but also seen, once, a glacier rope on a crevasse rescue carve into an aluminum biner such that it was tossed after the fun was over. Coulda been glacial till/ grit on the rope after traipsing around but I still am left to wonder. I remember when we went to the first nines on some ice climbs - with the old guys, there was pause, then eventually it became the norm. I guess I come down on the side of "can we get away with it, sure probably", should we in all cases, "not sure". And it is subjective to each. It's a lot to me like the current european style of alpine minimalism and moving fast - cool, until there's a storm or boo-boo maybe. And it is different if the rescue chopper (maybe even these days with warm pizza service?) is a sat or cell call away. But if you're in really remote areas, it can be a different game, is all. Or maybe it's the single malt and my birth sign again (the Cringing Chicken). Cheers and stay safe out there.
Addenda: Remembered this, but couldn't find it for a bit - Via Ferrata Accidents - big jolt on a fall - remember ANSI Z - don't fall !!!!! Work Positioning does not equal fall arrest !!!!!
Addenda: Remembered this, but couldn't find it for a bit - Via Ferrata Accidents - big jolt on a fall - remember ANSI Z - don't fall !!!!! Work Positioning does not equal fall arrest !!!!!
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