Gate Chatter... Myth or fact? .. Deadly or lifely?

Jim's Accident

Thanks for the link Kbobby.

I see nothing in the ANAM report that indicates the biner broke due to chatter or being open when fallen on. Many possibilities exist...nose of biner caught in ice screw hanger, biner cross loaded over rock or ice bulge, etc.

Will S wrote:nose of biner caught in ice screw hanger, biner cross loaded over rock or ice bulge, etc.

it does say it was the rope end biner which somewhat rules out nose hooked, the break description of the recovered biner sounds like what BD's testing produced from major axis pull testing, but you're very right on nothing to do with gate chatter

Mitch Musci wrote:Consider the fact that most leader falls generate between 4-7kn of force on the system. And if you look at the open gate strength of most carabiners, it is typically 7kn or greater.

It is more like 2-5 kN in the real world, at least for single pitch falls with climbers weighing 160 lbs or less. I have done a bit of testing in the real world, and I have never been able to break 5 kN, not even with a full on running belay, a rope with a high impact force rating, and a fall on the first bolt. I have taken 30' whippers higher up on routes and barely even broke 4kN. Mind I am only 160 lbs with gear, so if you weigh more that will change. But in reality, generating over 7kN in a single pitch environment is hard.

However, if you load the carabiner far from the spine, then the carabiner will not hold its rated load, and it is possible to break the biner. I have broken carabiners rated for 25kN with only about 15kN when I loaded the biner at the 3/5ths mark (away from the spine) as opposed to along the spine. I suspect the majority of the biners that have failed in the real world with the gate open were either class X carabiners, loaded far from the spine, loaded with the nose pinched against a pin or against a bolt, or had a deep grove worn in them. I also suspect that using twin ropes can reduce the strength of the carabiner to some extent as they place the load closer to the middle.

Price wrote:A few years back we were having this conversation and some aid climber was claiming that he unclipped ~20 pieces in a single fall. He attributed all of this to gate flutter. I'll see if I can find the post. It was quite amusing.

I remember that post, I called that guy out. The only possible way that could have happened that I can think of is all 20 of those pieces were pins, he used a single carabiner with no sling on all 20 of the pins, and he backclipped them all. But even then, the statistical chances of all 20 coming unclipped are immeasurably low. Furthermore, if his aid line was hard enough to require 20 pins in a row, he would be experienced enough not to make that mistake. I just cannot think of any conceivable scenario where that would be even remotely plausible.

From what we figured out the biner broke from gate chatter,

As noted this was the rope end biner......

On a sling that hung approx 4-6 inches from the ice, so no spine contact onto the ice......

As written in ANAM.......

I was there, I lived it, I wrote it...

The "broken" piece was never recovered.......

That biner broke when weighted because the gate was open or partially open from gate flutter.....

I had the same batch biners tested and broken in gate open and gate closed tests....

Both tests showed the biners breaking in the range as per spec.

Jim Amidon wrote:From what we figured out the biner broke from gate chatter, As noted this was the rope end biner...... On a sling that hung approx 4-6 inches from the ice, so no spine contact onto the ice...... As written in ANAM....... I was there, I lived it, I wrote it... The "broken" piece was never recovered....... That biner broke when weighted because the gate was open or partially open from gate flutter..... I had the same batch biners tested and broken in gate open and gate closed tests.... Both tests showed the biners breaking in the range as per spec.

I read the report. Sorry to hear you had to go through that, I am glad to see you made it. However, despite reading the report I am a bit blurry on a few specifics. Let me make sure I got this right. You were about 90' off the deck with three pieces between you and the ground. You were leading on an 9.8mm and an 8.5mm rope which was clipped to the pieces as a twin rope system. You fell ripping the first two pieces and took a 70' whipper onto the third piece. The rope end of the biner on the quickdraw on the third piece broke upon loading. Is that correct? If you dont mind me asking, why were you using a 9.8mm and 8.5mm rope as a twin? And lastly, do you remember the open gate strength rating of the biner and your approximate weight? I am just curious as to the factors that attributed to the carabiner's failure.

6 pieces total........

2 ripped.......

One biner failed.....

9K open gate strength...

Twas early on in climbing for me, and I do not remember if one of us forgot to bring another skinny along, but those were the ropes we used and we mistakenly used them as twins, instead of two singles....

Weight with gear dunno maybe 185-90lbs

Jim, thanks for sharing your experience. Personally, I think you are correct that the gate on that carabiner fluttered during your fall.

The largest contributing factor toward your accident was almost certainly clipping those two ropes as twins:
(1) The higher impact forces from the two ropes clipped in parallel almost certainly contributed to ripping out the ice screw, and likely the piton as well (though it is tough to say, because Specters are iffy anyway).
(2) Because the ropes were of different diameters, they would have run through the protection at different speeds. This can lead to vibrations in the carabiner, which could have caused the flutter.
(3) The high impact forces from the two-rope system, in the fluttering carabiner could easily have peaked above 9kN.

In any case, I am glad you are still around to tell your story. Thanks again.

(1) The higher impact forces from the two ropes clipped in parallel almost certainly contributed to ripping out the ice screw, and likely the piton as well (though it is tough to say, because Specters are iffy anyway).
(2) Because the ropes were of different diameters, they would have run through the protection at different speeds. This can lead to vibrations in the carabiner, which could have caused the flutter.
(3) The high impact forces from the two-rope system, in the fluttering carabiner could easily have peaked above 9kN.

Yes this was the conclusion reached........

And yes gate flutter is real

Jim Amidon wrote:6 pieces total........ 2 ripped....... One biner failed..... 9K open gate strength... Twas early on in climbing for me, and I do not remember if one of us forgot to bring another skinny along, but those were the ropes we used and we mistakenly used them as twins, instead of two singles.... Weight with gear dunno maybe 185-90lbs

Well, I can fully understand why the carabiner broke then. You were using twin ropes, rather thick twins at that which means the combined impact force rating of those ropes may have exceeded 12 kN, and the load would have been placed closer to the middle which means the carabiner may not have been able to hold the rated 9kN load, especially if the 9.8mm rope was in the middle and the 8.5 was against the spine. Plus, 190 lbs flying 70' down onto a piece is a pretty serious fall. I am glad to see you made it out alive.

Was the belayer anchored down, or did he get pulled up into the air?

Here is some high speed imaging of gate chatter. Took it with my buddy in my lab.

youtube.com/watch?v=a3XhgVB…

Thanks, JLP. We were probably too liberal in stating the 2nd conclusion with the data we got, but we were still shocked that both gates open on impact. Hopefully in the next couple months we will do a more controlled study, watching for impact point, measuring impact force and force required for gate actuation (we had one that we recorded where the gate opened completely and bounced off the back of the biner, but it was an older one :) ).

I imagine this can become more of an issue with older biners as spring tension lessens somewhat.

I witnessed the gate open on one of my draws while falling. The nature of the fall resulted in the draw violently smashing into the rock which opened the gate very momentarily. I both saw and heard the gate open mid fall. Fortunately the gate closed before I fully weighted the rope so no harm came. I was using an old school Petzl Spirit (2nd generation).

That said, gate chatter is very low on my lists of worries.

edit: old topic. 2012. Nice.

20 kN, it was an old Petzl Spirit that we tested that opened all the way :). What a coincidence.

Eric Hardester wrote:20 kN, it was an old Petzl Spirit that we tested that opened all the way :). What a coincidence.

Well, fortunately those biners have a 9.5kN open gate rating then.