Triaxial Loading

Since it's been enough time and nobody has answered, its 3 points of loading under tension, most problematic with a carabiner, (see the providence Ringling Brothers accident where a carabiner that was triaxially loaded broke, and dropped a bunch of people) though you can do it with shackles as well. In the case of the Ringling incident, they had 2 pear rings on a carabiner which caused it to break. The osha findings cited that a shackle would have abated that. With a carabiner, the strength is inline with the spine, so a triaxial load spread that out at an angle and therefore distribute the load in a way that lowers the overall strength of the carabiner and puts stress on it.

As far as I know, nobody recommends or says doing this with a carabiner is safe.
@josh88 and @RonHebbard and everybody else: sorry to be a bit of a ghost. We're on a big training compliance push around here. Anyhoo…..
Josh pretty much nails it, and since I have a thing for Black Diamond gear, here's some great stuff regarding what triaxial loading is, what it does to carabiners (yep, it's baaaaad).
https://www.blackdiamondequipment.com/en_US/qc-lab-off-axis-tri-axial-carabiner-loading.html
From the page linked above:

Bottom Line:

"In general, climbing gear is pretty robust, but that statement holds more true when the gear is used as designed and in typical loading scenarios. Once you start to stray off from ideal use (ie. off-axis loading, tri-axial loading, quad-axis loading), then you can see the ultimate strength reduced, even to the point, as in a nose-hooked scenario, where things become super sketchy.

So the bottom line is that you need to keep carabiners lined up along the major axis and try not to allow for multi-directional loading of carabiners, because it compromises their strength. "


Now, as for where we encounter this:
Lots of times, in my own anecdotal experience, in recreational climbing scenarios. In other words, folks who just don't know.
In terms of business, and again in my own anecdotal (and what I've heard from other friends who work in the air), mostly with aerialists with little to no training- or just enough to be dangerous. Truly, want make yourself crazy? Go jump into the "aerialist safety" type groups on the Book of Face. We also see this with more inexperienced riggers trying to cram a whole lot of stuff into too little space.
Do some reading- manuals and catalogues and websites will tell you all kinds of stuff you never knew you never knew. (For those of you who have been around, you'll recognize the acronym: RTFM)

How do we mitigate this stuff? Training! Always share knowledge to make others better. But make SURE you know what you're talking about. If you can train nothing else, train people to say "stop" when there is question or doubt. Sometimes it's hard to train courage to people for things like this, but it's totally okay to raise a concern and find out your fears were unfounded. Know why? Because if you say nothing, and someone is injured/dies or millions of dollars of gear crash down- how you gonna feel about yourself after that?

Now, the rest of the mighty CB should jump in here and call out what I missed. Seriously, go! :grin:
 
Thanks, Bill! Somedays I just bang my head on the keyboard to see how many keys I can hit at once. Somedays I do actual things.
-Brian
 
At the risk of impersonating Captain Obviousman, isn't triaxial loading one use of a pear ring?
 
At the risk of impersonating Captain Obviousman, isn't triaxial loading one use of a pear ring?
Sure is. But pear rings are built for that. Carabiners, definitely not.

As for shackles, we're talking as in making legs to a shackle? Watch out for that bridle angle that you don't go past the capacity of the shackle.
 

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