How Strong is Strong?

There’s no question that climbing gear is crazy strong. Each successive whip proves that (go team!), but how do we really know that our carabiner won’t fail on the next fall?

One might have said, “High-Clip, you idiot, look at the rating. That carabiner can take many kN…it’s been strength tested…chill dude.” So, being the nerdy physics student I am, I checked out these ratings on my go-to quickdraws, finding myself quite confused. The strength ratings are in kN, but in my mind that just describes weight…surely no one expects a 25 kN climber, right? Obviously that’s impossible, so I consulted Black Diamond, inundating them with questions about impulse and force and N*s and all units with a Newton and what they really mean and what are they really measuring…

As it turns out, researchers at BD don’t actually expect a climber to weigh 25 kN, but they are measuring force and they do mean in Newtons. The ratings are the maximum forces that the gear can withstand before failure. To see what I mean, check out BD’s QC Lab where you can watch total destruction.

Yet, maximum force doesn’t really describe what happens when a climber falls, and so there must be some sort of testing that better simulates falling. Plus, what about wear over time? Strength of old draws? Unfortunately, much of BD’s testing is proprietary, so I can’t detail exactly what happens during testing, but there are more test simulating real-life falls, old/worn gear, and strength over time. On top of that, BD has people who go out and abuse the life out of the gear in the last part of the prototype phase (how cool is it to have that job?!?!). Clearly, BD tests climbing gear more than sufficiently…but what sorts of treasures has KP (Kolin Powick, the mechanical engineer who runs the QC lab at BD) uncovered? Here’s some oversimplified fun facts I’ve gleaned from KP’s conclusions:

• Ropes never really recover from falls, but some rest/loosening knots helps soften successive falls
• Quickdraw gates have to face the same direction
• Belay loops can still function while being cut 80% through
• Webbing doesn’t last forever, and neither does metal!
• The ends of an old rope can’t withstand the same forces as the middles can
• Draws in gyms need to be replaced more often from abrasion than from other forms of wear

I could go on and on, but the point is climbing gear is CRAZY strong, PLEASE leave the strength testing to the professionals (do not try these at home), and there will be more to come on strength testing! I’d love to hear what gear questions or fun facts you guys have, so be sure to let us know! Lastly, don’t mind my nerdy puns if I end up responding with a whole load of ‘em.

Ah, classic Newton.

14 Replies to “How Strong is Strong?”

1. nice article, is there dynamic testing: taking the 100 kg weight and dropping it 50 m to simulate a fall? Pulling static load off a rope tied to an aluminum clasp is not really testing a fall in a real-life situation… What does it mean “ropes really recover from falls…” this is also true to metal, do they test how many times you can “fall” using the same rope? That would be the most interesting parameter in this kind of post. Good “nerdy” work, even if the language is a bit sarcastic 🙂

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1. Thank you! The more real-life tests are proprietary. Yes, BD does do quite a bit of wear testing. You should totally check out BD’s QC Lab where KP goes into specifics about a lot of this stuff!

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2. Excellent article! I trust BD right next to mother and apple pie. May I add a thought about equipment?
British friend and climbing partner Dave Gregory climbed for 65 years before his death at 82 a couple of years ago. His climbing career is amazing in many ways, not least because he was one of the hard Yorkshire lads of the fifties (Whillans once bailed him out of a French jail) and he survived climbing hard with the most primitive equipment (he used to walk railway tracks looking for loose bolts of various dimensions that could be turned into protection.) He was a lad and he found a kindred American spirit in me. Nothing pleased us more than to find gear left by careless others, though he was always more pleased than I. I did (and do) have my limits.
We climbed a fine route (Euphoria?) on Pennyroyal Arches fifteen years ago. The descent was via rappel. The last station gave me more than a casual qualm. A living-room sized boulder on a wide ledge was the anchor. It was wrapped with forty feet of the worst webbing I’ve ever encountered – rope-burned, chewed by rats, attacked by demented dwarves with hatchets and sun-faded. Dave gave it a yank and pronounced it sound. He threaded the ropes through it and made ready to rappel. I anchored myself, clipped a long runner to our ropes with a locker and prepared to take his weight when the ratty sling failed. He gave me a quizzical look: you doubt my judgment?
Hey – insurance is insurance and it’s free.
Needless to say, he got down in fine shape called a cheery “Off rappel.”
My turn.
Never, before or since, have I worried more about my weight. I thought helium thoughts all the way down.

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