These quicklinks all broke at forces 5 times higher than they would realistically ever experience as part of a rap anchor.

Summary of statistical argument for those who don't care:

My calculation of the confidence interval was correct, but the interpretation of it was not. I maintain that whether or not you can assume normality is largely at the discretion of the user.

My apologies for poor tone used earlier.

However, I do wonder about the statistical signifance of the sample size relative to the box of 50 that I pulled them out of. How does that compare to testing 1000's out of millions produced?

isn't it about our statistical confidence? How do you know you #2 cam won't break during a normal fall?

If, after 1000 tests no device failed under 5000 pounds you can be pretty confident none would break at 3000 pounds.

If our quick links are highly variable we can still establish an expected range of failure and work within that. Could we not?

But the bigger issue here, which apparently I am the only one who understands, is we have no valid statistical reason to believe that the very next link you pull out of the box won't be junk.

I simply want to know two things
1. what is the average strength of the device
2. is that strength likely going to diminish quickly over time.
3. What are the forces I can expect to generate on that device.

We have no basis to rule out, for example, that the distribution is normal, except for 1 unit in 500 that is junk.

Another pertinent question is whether or not that "junk" unit is easily identifiable. I would bet that one of these units that would fail below the rated SWL would have visible and/or functional defects that would be obvious. But statistically, we have no groundts to predict that either.

Does anyone know of or have a report of a single quicklink that has broken in climbing applications?

I have heard of plenty of biners but never a quicklink.

Most of the gyms I go to have quicklinks on the bolt of the draw. These probably take more falls more often than anything out there. I don't think they're ever replaced.

I've still not heard of one breaking.

Jay

I realize that the discussion is on the quicklinks in question, not quicklinks in general.

For a good many years (most of technical climbing's history) quicklinks manufactured by reputable climbing companies have not been available.

These are extremely recent. I don't know if I've ever rapped off a petzl or fixe brand quicklink. I bet I've rapped off over 1000 different quicklinks. I had no clue of the history of them, who manufactured them, or the QC process involved.

Almost all other climbers are in the same boat. All over the world, not just in America.

Then gyms also use QL's and I've never seen one of them branded at all.

With the enormous use of quicklinks with all manner of variability in their quality, I hardly believe that Tradklime's are the only ones of dubious origin. I have yet to ever hear of a QL specific accident or failure. Ever.

I don't follow this sort of thing though, this is a legit question. So maybe someone who does follow this can tell me. Has a quicklink ever been broken by a climber?

You know... since there's not that many in a box, it wouldn't be too hard to proof them individually by breaking a loop of 6mm cord. That'd be enough to proof the individual piece to ~12kN and could be done with a couple long pieces of pipe or 2x4's (think levers...). It would also be low enough to not prevent later use.

These quick links are garbage. Let me guess: the OP doesn't want to pay for quality hardware.

Jay

I assume you are referring to me since I sent the subject quicklinks to Aric, and it's certainly

Frankly, with your reaction to this, I don't understand how you clip bolts that you didn't install yourself. And how do people justify TRing off of 2 quick draws at the top of a climb, when they could use lockers. And how do people justify only placing 3 pieces of gear for an anchor when they could place 10.

You may feel that this limited testing is sufficient to determine these quicklinks are junk...

It's a good idea, 4-5 kN is probably enough.

It's funny to me that up in your ivory tower you feel the need to selectively quote to be misleading.

In 20 years of posting on internet forums, listserves, and the like, I am proud to say I have never, ever done that. Perhaps you just didn't understand something for a change.

Edit: What is especially odd about your accusation is that I quoted your post in its entirety!

Jay