Two Opposite and Opposed Carabiners: Possibly Weaker Than a Single Carabiner

nicelegs wrote:These threads don't teach us anything about rock climbing. What they teach us about other climbers is a wonderful thing.

These threads are like asking a woman if there is another woman at work she doesn't like.

Bryan Hall wrote: I seriously doubt that. I have never in 8 years of climbing and guiding seen climbers flail on a top rope in such a way that the quickdraws move upwards, twist over each other and then settle onto an edge. Everything I know about physics, climbing, rope and anchor systems defies the possibility that the top rope caused a correctly set up anchor to do that.

Don't be so quick to doubt. If the climber spins up and over the belay side of the TR, this can cause havoc upstairs at the anchor. Especially if it's 2 QD's.

It's most likely a combination of things. Twist in the toprope, climber tried the adjacent route, there was a ledge along the route..... You get the idea. It's not that inconceivable to reproduce the picture above.

If someone is going to flail then a single master point with 2 locking biners is a good idea.

the rope is still the weakest, and NON-redundant link in the scenario. Wth? All this redundancy with a single point of failure, "the rope". Silly

I see the concerns that it raises. If two steel biners fail at half of a single ones rated value, then for aluminum it could be even worse.

My problem with this is the validity of the test. I wish 20KN would have posted the "study". All he posted was a video, and you cant tell much by that. If anything, it actually looks to me like the sling was girth hitched in the video, creating a pulley effect on the biners that would actually probably come close to accounting for the compounded force on the biners, explaining the "1/2" strength loss.

But it's all conjecture until you get actual facts for the "study".

Relevance to any real-world concerns aside, there seem to be some issues of vocabulary.

The 50 kN rating on the steel biners is presumably the level at which they break under load. These biners did not, as far as I can tell, break (the video is completely worthless in terms of understanding what happened to the biners). The gates apparently broke from the sideways loads imposed by the locking collars. That sideways load rating, if one exists, would be a completely different rating, not the 50 kN rating, and presumably much lower than 50 kN, so comparing the results to the 50 kN rating is sensational but misleading.

If one wanted a comparison with the 50 kN rating, the test should have continued until both carabiners broke and released the yellow sling. As it is, it appears that the gates have broken but the "climber" is still belayed on a pair of reversed links, albeit both open. Scary, but no fatalities, even of the virtual kind, yet. Meanwhile, the plausible assumption that you get double the gate-open rating of a single biner is untested.

So for example, if you get bust two BD Positron lockers this way, with a gate-open strength of 8 kN, your damaged system might still be able to withstand 16 kN or so before breaking.

As for methodology, there may be a difference between having a relatively narrow climbing rope provide the load and the relatively wide yellow sling used in the test. The narrower climbing rope profile is much more likely to allow the carabiners to rotate outwards, aligning their spines as the load is applied, so that the gates no longer press against the spines of the opposite biner, as in the picture posted by Joshua Reinig of the reversed D-shaped biners.

David Coley wrote: As someone who has had a powerpoint screwgate snap on him, often uses back-to-back snap gates rather lockers, uses two lockers to attach his silent partner and who sometimes leads using a pair of lockers rather than by tying into the rope, I would be very, very, interested in any results you come up with! Thanks.

I actually tried to replicate the results using two oval solid-gate non-lockers, and I couldent break the gates. I'll try with some lockers. What is a snap gate?

Spri wrote: My problem with this is the validity of the test. I wish 20KN would have posted the "study". All he posted was a video, and you cant tell much by that.

The OP did not post much more than what I included. But here is the link to the Facebook group where I got the info from: facebook.com/groups/RopeTes…

20 kN wrote: I actually tried to replicate the results using two oval solid-gate non-lockers, and I couldent break the gates. I'll try with some lockers. What is a snap gate?

A snap gate is just another word for a non locker

None of these test are very relevant considering that a force of 5kn is enough to kill you.

Ray Pinpillage wrote:This is why I only top rope with 7 HMS biners.

lol I use all 12 that I own. safety first. i also climb with a 20mm rope just in case

Xam wrote:This is all wankery anyway but the people that are saying that the loads are way higher then will ever be achieved on TR, while correct, are missing the point. The point is that the two opposite and opposed lockers failed at LESS THEN HALF of the rated strength of the individual lockers due to an interesting failure mode. These were steel biners rated to 50 kN. Scaling to a pair of nominal aluminum lockers rated to 24 kN would imply the same failure mode causing failure at something less than 12kN, which might be concerning. This, of course, scales even lower for lower rated non-lockers, which might be more susceptible to this failure mode. This is 20kN's point.

No. This is not his point. Reread the op. The gates of locking biners prevent the biners from hanging flush. When subjected to high loads, the gates get forced together leading to their failure. So, you cannot make any direct correlation to non locking biners that hang flush.

If you want to draw any conclusion, it is that biners that don't hang flush and forced together by a load, may lead to premature gate failure leaving the biner in a situation similar to open gate.

So, two aluminum lockers, gate open strength of 6kN each: Exceeding 12kN = moot point for top rope. Hard to achieve even in a lead fall. Then again, who takes a lead fall onto two opposite and opposed lockers.

Bearbreeder's points emphasize this thread is fun conversation but not relevant to real world scenarios.

seth williamson wrote:None of these test are very relevant considering that a force of 5kn is enough to kill you.

Incorrect. But, we are not talking about the force on the climber. We are talking about the force on an anchor that could cause its failure. So, any force that leads to anchor failure can kill you.

seth williamson wrote:None of these test are very relevant considering that a force of 5kn is enough to kill you.

It depends on how long you are subjected to the force. Exposure to 5G for an hour would kill you. But exposure to 5G for under 100mS (which is typical in rock climbing) is not dangerous at all (in most conditions). The UIAA allows for an impact force of up to 12kN for a reason. The military found that the maximum amount of force a paratrooper could withstand for a short burst is 12G. In racing collisions, drivers have survived very-short instances of force exceeding 100G, which for a 225 lb person would be 100kN.

As it relates to climbing, a climber subjected to 5kN in a lead fall is very unlikely to sustain an injury, let alone death.

@ greg D...I am sorry I wasn't more clear but I agree with what you said in the previous post (the one referencing my earlier comment) and don't think what I wrote is in opposition, just making a more general point perhaps unclearly. If you read what I wrote later it might become clear that I understand your points and agree with them.

I still think it is interesting to show how two opposite and opposed biners can fail at a load less then a single biner due to open gate failure from this kind of gate loading. I think it does apply to wire gate opposite and opposed ovals as I have seen the photos of them both opening simultaneously under top rope loads. And yes I agree that this will virtually never happen and the loads to cause both biners to fail are higher then would be observed in a TR...thus, why I called it wankery (i.e. an interesting discourse with little real world application).

To reiterate: I agree with what you are saying, never disagreed, and think that any failure to communicate these things is due to a lack of clarity and specificity in my previous points due perhaps to the medium of communication. I did not mean to draw any general conclusions with my posts...just trying to make clear to people that were dismissing the OP out of hand that they might have been missing the point.

So yes this is interesting, but not a myth and easily explainable. First the strength of the carabiner is strongest along its spine correct? So if you start moving that force farther away from the spine like when using smaller width spectra slings or a single rope compared to a 1 inch wide nylon sling you will start to see your minimum breaking strengths go down tremendously. Almost in half depend on the shapes of the carabiner. Pear shaped and some d-shaped carabiners have been seen to do this more. This was also the topic of some recent ITRS presentation over the last couple of years and has been reproduced numerous times in slow pull tests. The thing is is that if you understand the physics of carabiners especially in rescue situations using a two person load on static ropes, you will never even remotely approach half the MBS of carabiners if you set up and use your systems appropriately. Which is why we only use 1 single locking carabiner usually > 26kn in our rescue systems. Two carabiners were found to be too redundant especially in systems that were set up appropriately. So now transfer that to rock climbing where we use dynamic ropes with one person loads. One locking carabiner is perfectly safe at your anchors as long as you are not threeway loading your locking carabiner. Now this is a very simple explanation to this so I suggest you take a rigging for rescue class to learn the facts and myths of climbing gear physics. Anyways I hope this helps. By the way we use single Petzl AMD lockers all through out our rescue systems with comfort, always knowing what forces our rescue systems will see. Also the human body starts to see tissue damage at 8 to 12 kn depending on the governing teasing agency. Take care and thanks for bringing this to the attention of the climbing community.

Matt

20 kN wrote: It depends on how long you are subjected to the force. Exposure to 5G for an hour would kill you. But exposure to 5G for under 100mS (which is typical in rock climbing) is not dangerous at all (in most conditions). The UIAA allows for an impact force of up to 12kN for a reason. The military found that the maximum amount of force a paratrooper could withstand for a short burst is 12G. In racing collisions, drivers have survived very-short instances of force exceeding 100G, which for a 225 lb person would be 100kN. As it relates to climbing, a climber subjected to 5kN in a lead fall is very unlikely to sustain an injury, let alone death.

How do you figure that? 100kn = 22480.89 lbs. youre telling me that you can survive a force of 22480.89 lbs?

i can kill a man with my pinkie toe

seth williamson wrote: How do you figure that? 100kn = 22480.89 lbs. youre telling me that you can survive a force of 22480.89 lbs?

20kN's explanation pretty much sums it up as simply as possible. i am trying to come up with another simple analogy/example. one way of looking at it is that you can have a very high peak load with a small duration, so the total energy under the curve might not be that much compared to a lower peak load with a long duration.

an example of this is in vehicle dynamics (i worked testing and modeling vehicle dynamics on high speed trains for almost 10 years). sometimes you have really high lateral loads at the wheel/rail interface due to transient pieces of track (say a joint in the track, point of turnout, frog, etc). these extremely short duration loads at the wheel/rail interface aren't necessarily a cause for concern because they are so quick that they don't really result in much lateral movement of the vehicle.

on the other hand, if you had the same lateral load and it was applied over a long duration (on the order of several seconds) you would be in the ditch for sure.

there are a ton of factors that play into this - speed/acceleration, mass, stiffness of the items, damping of the items, etc. a climber's body is fairly soft in terms of stiffness, particularly considering our ability to 'bend' versus the tie in point. with a short duration load, like a lead fall, our bodies dissipate much of the energy through movement/deformation.

seth williamson wrote:None of these test are very relevant considering that a force of 5kn is enough to kill you.

Where on earth do you get that rubbish from? Zydrunas Savickas has lifted near enough that off the floor (504kg or 4.94kN).
Enough race drivers have survived over 100G and the record is over 200, F1 car cells are crash tested to 80G. Even airline seats these days are rated to 16G.