I was watching footage of an ice climbing, anchor-building demonstration, where the instructor cautioned not to shock-load a static anchor because even a very short fall on a static rig could break a locking carabiner. I have heard this before, although, in thirty years of climbing, guiding, and rigging, I have never personally experienced it. I am pretty sure that I have loaded anchors to the extent that he described, although with no such consequence.

I am curious about whether anyone here has ever broken a locking biner by shock-weighting it on a static anchor?

Considering the breaking strength of a locker, it's hard to imagine a shock load scenario where the biner would break. I would think in that sort of catastrophic situation (e.g., a factor-2 fall on the anchor) that the components of the anchor itself would fail before the biner would. Of course, maybe I'm not clear on what exactly is meant by a "static anchor."

JL

Here is the video link:

I don't know if he was exaggerating his statement for the sake of instilling extra caution in his students, or if I am just missing something. My experience is that locking biners can take significant abuse in those circumstances.

There were actually a few things about his method that I didn't agree with. For instance, he made the point that two anchors in the same mound of ice is a bad idea in the event that one of the ice mounds breaks away. Sound advice, but then he preceded to fully weight the one anchor in that very spot, before backing it up and equalizing the system - instructing his students to do the same.

On page 144 of How to Ice Climb!, Craig Luebben describes drop tests in which carabiners (including at least one locker) broke. He goes on to comment that the test conditions were particularly severe. The instructor in that video might have been thinking of those experiments.

I was also struck by the guy's hanging from just one screw moments after recommending that the anchors not be too close. In his defense, he would probably say that one thing is to gradually transfer your weight to the screw, and quite another is to fall on it. Anchor failure is much more likely in the latter case. On the other hand, a beginner may easily misjudge a screw placement. A safer approach would be to use one of the tools as temporary second anchor.

Interesting. I don't know about breaking a carabiner after a short fall on a static anchor (seems unlikely), but there were at least three things this guy did that were unacceptable, especially in what seems to be an "instructional" video.

1. Ken, you already mentioned it: coming off belay on a single anchor point, before the whole anchor is built and equalized. There are occasions when you have to belay off of just a single point, but when you have the option of building a multipoint anchor, it doesn't make sense to come off belay until it's finished. He implies that there's a time benefit (the belayer could start dismantling his anchor), but it seems to me that benefit would be negligible.

2. This is pretty minor, but, again, since it's an "instructional" video, worth mentioning. He says that after you're clipped in, you "...say 'OK, I'm off belay', 'secure', whatever you say..." There should be no ambiguity about which command to use in a given situation or what it means, especially for beginners. Period. It's great if you're close enough that you can easily carry on a conversation, but how often does that happen? And it's also great if you're with a long-time partner when you hardly need to say anything at all, you just know, but that won't always be the case. If you've been climbing for a while, you tend to take this part of it for granted, but think of the potential consequences of ill-communication.

3. Mr. Editor cuts this last bit out, but if he does what I think he does, it's pretty bad. After he finished building the anchor, I think he's going to completely unclip from the first screw so that he can re-clip into his cordalette. In other words, there was a moment during which he was not on belay and also not clipped into the anchor. There would never be any situation that I can think of in which that would be necessary or desirable. There are no savings in time or in gear. He started to say something about it actually being "semi-dangerous", but, as I said, Mr. Editor steps in at that point.

In just 9 minutes, this guy has managed to lose all credibility with me, especially the last item. So just based on that, I'd be skeptical about anything he says. BTW, he didn't specifically say "locking" carabiners, and I'm not sure how that would make any difference anyway since lockers tend to be on the upper end of carabiner strength rating.

He says that he's going to do a "semi-dangerous thing," but after the cut he does the right thing. What happened in between? (It would be better if he had clipped into the upper shelf of the cordelette and kept the main power point for the belay, but at least he clove-hitches into the anchor before unclipping the lower screw.) This is not to defend him. The general impression I get is that this instructor is very tentative. I also don't understand why he's not teaching how to build an anchor sufficiently close to the ground that his students may see what he does.

I understand what he was saying about breaking a carabiner. Taking a fall on a static line (ie daisy chain) if you are above it, even a short distance. Since the daisy does not stretch, the full force of the fall is exerted on the anchor, and it could break even a locker.

I'm not all that impressed with some of the aforementioned things in the video, as well.

Force = mass x acceleration : a fall on a static anchor, i.e. falling on a static line or runner, with no dynamic link in the system results in extremely high acceleration(deceleration) whcih results in a much higher force than with a dynamic shock absorbing system.

A 1m fall on a static runner results in a fall time of about .319s and a maximum velocity of 3.13m/s.
d=a*t^2
v=a*t

If the system stretches 6cm, that gives a stopping time of .013s and a deceleration of 240m/s^2.

This gives rise to a force of 80kg x 240m/s^2 = 19200 N =19kN

Now of course I just made these numbers up, but if you believe a stretch of 6cm in a .5m static runner, then it is apparent that a breaking jolt could possibly be generated.

Although it is probably still unlikely that a force this high will actually be generated due to energy dissipation in the system, such as body movement or the harness slipping along the waist and stretching more, still it is probably possible.

I would say it depends on how the locker is loaded. Cross loaded or tri-axial loaded ( i.e. using a magic X) would greatly increase the chances or breaking even a locker. Lockers do not have much greater minor axis strength than standard carabiners.

But no I have not broken any lockers, and I doubt that there are many instances in climbing where a fall is ever static. Even falling on a nylon daisy is not truly static. If you want an example of the dynamic qualities of nylon try using a sling as a funkness device. I have broken 3/8" bolts, hangers and many carabiners with a real funkness device, but only ended up with a sore shoulder funking with a sling.

I am almost tempted to try it, myself, although I seriously doubt that the locker will break. I am more concerned with compressing my spine in even a one meter fall onto a static belay.

okay, here's what I don't get then with short falls - I take a leader fall while aiding, but forget to unclip myself from the lower piece using a double length runner or daisy - so about a 4+ footer & I hammer myself and the pro that arrests my fall. The pro is rated about 6kN-8kN, it holds no problem.

I feel there is something wrong in the model that is not correctly addressing how much energy & duration of which is actually generated that impacts the protection & carabiner(s) -- if we are actually coming up with numbers that could easily snap biners. I had the impression Luebben came up with actuals that this description of shockloading was not significant and was based more on fear.


Man, that video kinda had me scratching my head. I don't feel too comfy working exposed off one point. It looks to me like he also double clipped his daisy. I would've just put both screws in and made a quick clove & 8 with the climbing rope.

Also, I see that he had pre-tied off one of his ice screws and then sunk the screw to the hilt. This looked a bit sketchy to me, especially since that is the sole screw that he ends up committing to when he goes off belay. The sling can't be bomber, compressed between the ice and the screw head like that.

As for the static fall onto a biner, that might be a theoretical concern, but that guy has bigger things to worry about (like unclipping himself in a "semi-dangerous" way).