Ok, there’ve been a lot of threads discussing the safety of a “sliding x” anchor equalizing system. Everybody knows the big problem with the “sliding x”; if one anchor fails, the remaining anchor will be severely shock loaded.

The most common way to reduce the possible shock load (other than using a different equalizing system) is to tie an overhand knot in both legs. If one anchor blows, the rope bearing biner will drop only a short distance onto the overhand knot.

My question: Has anyone given thought to how much relative strength the sling has with the biner loaded onto the overhand knot in this configuration? It seems to me like it might be significantly weaker, but I hesitate to abandon my favorite equalizing system.

Your thoughts, please.

Ok, there’ve been a lot of threads discussing the safety of a “sliding x” anchor equalizing system. Everybody knows the big problem with the “sliding x”; if one anchor fails, the remaining anchor will be severely shock loaded.

Funny this should come along just now. I'm just finishing redoing the anchor books into one big anchor building omnibus. We're basically done --all that's left is a bit of editing, and incorporating a slew of drop tests we did with Sterling Ropes (conducted by America's leading drop/test dude, Jim Ewing, with statistical analysis by trad master Dr. Larry Hamilton and climber/fitness model/criminology professor, the esteemd "Crimpgirl," Dr. Callie Rennisson).

The tests were to determine, once and for all, which system was better at load sharing when sustaining a dynamic fall (Factor 1 for our testing)--the Cordelette, or the Sliding X. Both rigging systems were tested when rigged to vertical and horizontally oriented anchor points. In the vertical configuration--as you find in a crack--the rigging systems have unequal sized legs; in the horizontal configured anchor (as found, for instance, with bolts placed side to side on top of a sport climb), the legs are as close to equal as they could be tied.

Moreover, each set up was tested with several diameters of high tensile strength cord and webbing (Dyneema, Technora, Spectra, et al), as well as with old style nylon cord and webbing.

It is still too early to release the results, but I can say right now that there is a significant difference in load sharing performance between the two systems, and much that has been written about the cordelette's equalizing capacities is strictly untrue.

More later. I'm just eyeballing the graphs I got from Jim, Larry and Crimpy. At least now we finally know what's up with these systems, and that's a real good thing.

JL

Shockloading the big problem? I was always bothered more by the lack of redundancy in the sling.

The improved sliding x does offer a bit of redundancy; even if part of the sling fails ( provided that it fails above the knot) the rope will still be caught. If the the sling fails below the knot, you are indeed, thoroughly f**ked. But this never bothered me; my anchor sling's in excellent condition.

Shockloading the big problem? I was always bothered more by the lack of redundancy in the sling.

Largo, thanks for a great post. I'm looking forward to the new book.

Just a bit of thinking out loud here. Did you do any testing where part of the anchor failed? The OP brings up a good point regarding the shockload potential vs the limited equalization. I'm trying to imagine a test rig that would have one bomber anchor point and one that could be rigged to fail at less than the applied force. Thus a test could be done that simulated a partial failure each trial. Have you done anything like that?

That sounds like an easy question to answer, but it's not. Yes, Jim started doing some tests like this just to see what figures came up. It's easy to rig: you just tie off one anchor with a piece of sling that gives out at, say, 1,000 pounds, and you do a drop that generates 1,200 pounds.

What makes this tricky is that so long as you are climbing with a dynamic rope that is belayed, true "shock loading" never really occurs owing to the stretch in the rope and, most importantly, rope slip through the belay device. In other words, when a Sliding X is configured with limiter knots, the few inches of extension will never produce a true shock load, or anything even approaching that kind of stress.

A genuine shock load will only occur in those instances reflected in Duane Raleigh's recent tests for Rock and Ice, say, when someone is tied off to an anchor with a short shank of high tensile cord. He climbs a few feet above the anchor and falls. Here, you have true shock loading, where biners blow apart and anchors rip out because there's no rope slip at the belay device, no stretch in the rope, no human body to absorb loading, et al.

This doesn't happen when a placement blows out on a Sliding X or a Cordelette, owing to flex and give in other parts of the system during loading.

JL

Largo, thanks for a great post. I'm looking forward to the new book.

Just a bit of thinking out loud here. Did you do any testing where part of the anchor failed? The OP brings up a good point regarding the shockload potential vs the limited equalization. I'm trying to imagine a test rig that would have one bomber anchor point and one that could be rigged to fail at less than the applied force. Thus a test could be done that simulated a partial failure each trial. Have you done anything like that?

Thanks again, You stated exactly what I would suspect and basically the test that I would propose as well. I was more interested to see if there was data to suport what the diagnostics would suggest. My belief is that there is a significant reduction in force prior to the piece pulling (unless it is really bad) and the that in the minor extension that occurs only minimal energy is regained.

What I'm saying here is that it was thought by some that the Sliding X (with limiter knots) was a poor choice