you’re the one that has been arguing for pages that tri-axle loading is a concern with the rig that the AMGA teaches because you think 9kn at the belay is the MCE in a top rope fall. So, one of us is propagating bullshit, the other is countering it. And guess what? The guy countering it is not the guy who finally admitted the MCE load at a TR anchor is more likely 5kn.

This entire argument was not about O&O biners. It was about your claim that the OP’s pic of an AMGA taught rigging technique was dangerous due to tri-axle loading. Where have you been?

The 9kn that the report suggest as a standard for single-pitch climbing is not based on the potential of TR falls, and the report makes this clear. It is based on FF 1, which will not happen in a TR situation. How many times will people have to point this out to you before you finally get it?

I wasn’t claiming my experience as imparting credibility in this argument, as you repeatedly use yours

The syndrome you suffer from is what I call “The Ignorance of Experience”. It’s a very real risk in rescue personnel. The sufferer ignores data that disagrees with what they’ve internalized as gospel over their years of experience.

While that’s nice you’ve had a long career, anyone that thinks 9kn at the belay in a TR situation is even remotely possible is a CLIMBING DUMBASS. You need to stick to your area of expertise, rescue rigging, and leave the climbing systems advice to people that actually know what they are talking about.

The mistake you’re making here is in thinking I have something to learn in this argument.

Can we put it to rest now?

... no carabiner is designed for such load...

According to Petzl, this carabiner can be loaded in three directions.

that looks totally fine despite what some "expert" may say

whether you opposed lockers or not is your choice ... but make sure they are both LOCKED if you dont ... and every locker eventually has its gate rubbed against rock when unsupervised ... as anyone with real top rope set up experience will attest to ... the climbers moves all over the place, the rope gets flipped here and there ... it wont destroy yr locker or make it dangerous, biners are tough

Very lively discussion guys. Thanks for the input. So I just went ahead and bought some 11mm static rope to setup my anchors. My rigged setup is pictured below.

I know some folks don't like the clove hitch (it's adjustable!) and others don't like the two loops on a bite at the master point (it makes me happy), but all I really want is to prevent falling to my death! Hopefully this will do the job. :)

Thanks again for your insight. It's been a real help and might have contributed to my long life!

Opposite/opposed locking 'biners on two loops made from overhands on a bite. I know O and O doesn't matter for lockers, but it helps me remember to pay attention.

[image]http://swatyy.webs.com/setup.jpg[/image]

One leg is a figure eight. The master point is made to length and the second leg is adjusted on a clove hitch to equalize the anchor.

For those of you who don't like clove hitches, what knot would you suggest and why is it better?

[image]http://swatyy.webs.com/legs.jpg[/image]

*edit: I bought *static* rope, not dynamic. ;p

More importantly than locked is that the gate opening is facing down, so the screw gate won't screw up.

Aluminum lockers aren't as tough as you might think. There have been plenty of broken 'biners, including broken locking sleeves from torsional or impact forces.

You can argue that O&O biners are always right for every application only if your experience and imagination are extremely limited.

Free-hanging 'biners (which are ideal for a top-rope anchor) are not always possible. On a slabby-topped route, the 'biners are going to be pressed into the rock (I've seen many like that). If the anchor cord loop is parallel to the rock face and the 'biners are perpendicular to the rock (not uncommon), then one of the gates will be pressed into the slab and rubbing on it.

That not only puts excessive wear and possible breaking force on the gate sleeve and risks unlocking it, but also moves the paired 'biners out of alignment so that the rope can get pinched between the respective spines.

This pinching, with excessive friction on the belay line, is also possible with a two-loop anchor sling (something like the picture on the right below).

[image]http://tawkroc.org/files/2010/06/top-rope-config-draws-432x256.jpg[/image]

I've been in EMS and technical rescue for quite a few years now. It has long been my opinion that anyone with any skill at the job would never be willing to rise above the rank of lieutenant, lest they not be able to do the job they love. It has also long been my opinion that anyone with any brains at all would defect before ever rising to a rank above lieutenant or to "municipal emergency manager," because they'd get a better job if they could.

Once again, you're completely misrepresenting my argument (i.e. building a straw man). My argument against ti-axial loading in any situation is that no carabiner is designed for such loads, every manufacturer issues specific warnings against using it in that fashion, and it's completely irresponsible to suggest on a beginner's forum that it's OK.

Yeah, and a top-rope situation would still never generate enough force to make this even remotely a concern.

I'm not "seriously saying" it, I'm quoting from a study by one of the world's leading rope system physicists.

My argument is completely independent of the potential loads at a TR anchor. And you continue to state that I "think 9kn at the belay is the MCE in a top rope fall", when I never stated so. I merely quoted a recognized expert who determined that to be a credible load limit for all falls less than FF1, which includes top rope and gym climbing.

I made clear that my own assumption is a MCE for top-roping of 5 kN at the anchor.

Actually, quite a bit of this thread has been focused on O&O biners, and my argument that, with lockers, it can be dangerous and is always unnecessary in a top rope anchor still stands.

If you had read the report with the thoroughness you continue to demand of me, you would know that the conclusions were based on all falls less than FF1, such as in top-rope and gym climbing. Attaway is very specific about that, but you continue to deny it on order to misrepresent his findings and support your own conclusions.

And anyone who states unequivocally that a serious rope loading event can never occur in top-roping either has a very limited imagination, very limited experience, or is deliberately deceptive or willfully ignorant.

But I am not arguing simply from my own personal experience (which is more far extensive than yours). I've quoted studies by two credible experts in the field, and I base my arguments on years of research and study of my own. Unlike a mere practitioner, who only needs to know enough to get by, as a long-time instructor I have to know my subject inside out in order to be able to train others. That's my responsibility as a teacher.

Part of my reputation in the international world of rigging and rescue is that I take nothing for gospel and, in fact, have published articles critical of much of the gospel of rope rescue (so much so that the publisher included a disclaimer indicating that it did not represent their own judgement and offered their advertisers an opportunity to respond).

Your "expertise" seems to be limited to "28 years on the sharp end".

The only reason you "have nothing to learn" is because you are far too pig-headed to be capable of learning. And because you refuse to recognize that you are merely projecting your own character flaws onto me - a habit that people routinely do when they haven't taken the time for adequate self-reflection.

Calling people names in CAPITAL LETTERS imparts no credibility to your rants (in fact, it seriously undermines them).

I'm right
You're not
I'm smart
You're clever but dense
I know about stuff
You don't
I'm qualified
You're not. No wait, you're over-qualified

Since you're not going to quit repeating yourself ad nauseam, let's just both pretend you won the argument and leave it at that.

There's a difference between the fallacy of arguing from authority and including a person's education, background and credentials as a reason to accept as credible his methodology and conclusions.

As I stated. But, as you first stated (above) before your initial criticism of his assumptions and methodology, you "only skimmed it".

I'm relatively certain that Attaway would welcome your critique. But I'm not particularly interested in arguing about assumed assumptions, especially when the author already offered sufficient caveats and disclaimers about those assumptions.

We should certainly look closely at Attaway's report, and his record does impart a degree of credibility, but it does not make what he has written into gospel.

As I stated. But, as you first stated (above) before your initial criticism of his assumptions and methodology, you "only skimmed it".

Nice work misrepresenting what I wrote. Look again and you'll see that the two statements you so misleadingly juxtaposed were from two posts an hour and a half apart. In the intervening time, I took a closer look a the report before I said anything more about it.

The bottom line... it is unrealistically high for TR falls, which are unlikely to generate FF1 falls.

Bullshit

Which is exactly the same thing I said. And, as already noted in another response, I accept nothing as gospel and expect others to be skeptical of anything presented as such.


Actually, it was you who just misread (and hence, misrepresented) what I wrote above. I noted that immediately after admitting to having "just skimmed it", you offered a number of methodological criticisms. So I was glad to see that you actually took the time to read what you had previously critiqued without adequate perusal.

I didn't catch that discussion in his paper (I only skimmed it), but I can think of several reasons that his Monte Carlo approach could be flawed. Mainly, it seems like he assumed the distributions of the various factors were independent, but this may not be so. For example, the distribution of fall factors may be correlated with the distribution of climber weights, or with the condition of the rope. What might this mean? One possibility: Climbers who climb a lot may tend to be more comfortable taking high-factor falls. They may also tend to use their ropes more, in which case that high-factor falls would tend to occur disproportionately on well-worn ropes, and high impact forces would occur more often than if all variables were independent. On the other hand, frequent climbers may be fitter and lighter than climbers who climb occasionally, which would tend to reduce the severity of those falls and reduce the impact force.

With that said, the bigger problem that I have, though, is that it appears that he generated his distribution of fall factors from stated information from surveys. This is of course subject to bias by those reporting the numbers, but the real problem is that he generated his distribution of single pitch/TR fall factors simply by truncating the distribution. This is going to give an extremely conservative distribution, biasing in favor of high fall factors. If you asked people for the biggest factor fall they've ever taken on TR, I am confident that you would come up with a very different distribution that you get by simply truncating the distribution of all fall factors.

I didn't catch that discussion in his paper (I only skimmed it), but I can think of several reasons that his Monte Carlo approach could be flawed. Mainly, it seems like he assumed...

This thread...

[image]http://www.stevenhumour.com/wp-content/uploads/2011/02/polar-bear-facepalm.jpg[/image]

there is utterly no way you are seeing 9 kn at the belay device in a real world top rope situation with dynamic rope that i know off ... you would have to be climbing above the anchor ... and not just 1-2 feet above it

or the belayer would need to be using a static rope and not paying attention with slack buildup at all ... since the OP i dont think is using static rope ...

But top ropes are commonly set up with static ropes, and some belayers don't pay attention and do let slack build up. But, you're wrong regardless. Even with a dynamic rope, if the belay is static, the force on a top rope anchor could conceivably exceed 9 kN:

[img]http://jt512.dyndns.org/images/tr-impact.png[/img]

Source: http://jt512.dyndns.org/impactcalc

Jay

But top ropes are commonly set up with static ropes, and some belayers don't pay attention and do let slack build up. But, you're wrong regardless. Even with a dynamic rope, if the belay is static, the force on a top rope anchor could conceivably exceed 9 kN:

[img]http://jt512.dyndns.org/images/tr-impact.png[/img]

Source: http://jt512.dyndns.org/impactcalc

Jay