Activity on the "Solution to John Long's Anchor Challenge" and the "Improved sliding X: Is it really safer?" thread is dying down, so I thought I'd post a wrap-up in case anyone stumbles across this one in the future and wonders what the hell ever resulted (sorry for the length).

Not being shy of incautious posts, I'll cut right to the punch line:

THERE IS NO SOLUTION TO JOHN LONG'S ANCHOR CHALLENGE

At least not in the sense that there are any anchor designs that deliver equal loading of 2-, 3-, or 4-placement anchors at the instant of peak force and if the direction of the forces on the master point might change from those for which the anchor was originally adjusted ("the criteria"). Include the requirement that some provision is made for limiting gross extension in the event of a placement failure and, of course, some KISS component. That's the challenge, as I understood it, that spawned the lengthy thread.

The above conclusion means that any purported "best" designs will be compromises in some respects--but probably not the respects that most climbers would anticipate. Let me explain the reasons, then I'll illustrate what I think is the best compromise design.

After nearly 900 posts, I see only three designs that have come forth which have the potential, geometrically at least, to actually equalize 3 arbitrarily located placements and to have some pretense at limiting extension: the Craig Short + John Long design with which I started the "Solutio to..." thread, some version of Richard Goldstone's "chopolette," and the AstroGlide (although I'm unaware that a finalized version has ever been illustrated). (Charlesjmm points out that the Gordolette and Mooselette may also qualify, but not if adaptability to 4 placements is required. That also kills the AstroGlide.) Nevertheless I assert categorically that none of these designs actually meet "the criteria" and that no feasible design will ever be found that does.

The reason is simple: material passing around a carabiner (or even a pulley) is not 100% efficient, mainly due to friction. I posted a few measurements in the "Sliding X..." thread and there are also descriptions of the effect and its consequences in my book, The Mountaineering Handbook. charlesjmm posted in corroboration. Even with the simplest conceivable 2-placement configuration (narrow high modulus cord or tape around a climber's pulley at the master point), the imbalance of force on the two anchors will be more than 10%--in other words, not equalized. When you consider a useful 3-placement system, such as the alpine equalizer or any of the proposals mentioned above, and practical materials, the imbalance is so severe as to render "equalization" completely out of the picture. Anyone who doubts this should proceed with the awareness that skinny nylon webbing or 7 mm cord passing around a carabiner has a force conveying efficiency of about 66% (skinny Spectra/Dyneema over anodized HMS biners doesn't reach 80% efficiency; fat cord and skinny carabiners make things worse as does, I surmise, abrupt loading). Now figure in the number of times that the material must move around one carabiner or another in order for equalization to occur in any given anchor design and the picture should become evident as the inefficiencies build upon each other. This is a relatively easy assertion to confirm by tests for anyone who has good spring scales.


This was the reality I confronted when I drafted my book about two years ago and unfortunately nothing has been proposed since to change things. So what can be done? Either simplify and de-emphasize equalization in favor of redundancy and a more sophisticated analysis of force directions, or/and settle for an anchor design that doesn't pretend to equalize perfectly but which fails gracefully.

John Long has mentioned a design called the equalette that takes the latter course. The best illustration is by charlesjmm.
http://i2.tinypic.com/swfu6b.jpg
That is a 4-placement version; it should be clear that it is 25/25/25/25 when hit by fall force only if all legs are exactly the same length and only if the ultimate directions of forces on the master point(s) are what the clove hitches were originally adjusted for. The 3-placement version starts off at 25/25/50--not equalized. The master point configuration, presumably balanced between the two carabiners, also has twice the sliding friction that's necessary. The main benefit is that carabiner friction is low and failure is to equalized placements (in the 3-placement version, but not in the 4-placement version), unlike the 1-knot cordelette design, which fails to but one. A problem is that any shift in the direction of applied forces from those for which the clove hitches were originally adjusted results in immediate conversion to a 2-placement anchor and doubling the force on one (in the case of the 3-placement version) or two (in the case of the 4-placement version) of the placements--even before any placement failures occur. John may supply more details--and fall-simulating tests--when his new book appears.

Here's another proposal:
http://i2.tinypic.com/swftp5.jpg
The 3-placement version of this design starts off at a nominal 25/25/50 force distribution, mitigated somewhat by making the longest leg go to the most distant placement (fall force tends to shift to the least stretchy side, which in this case is the one with two placements). Starting off without geometric equalization seems an unavoidable compromise. The equalization component, which I have been calling a "troublette," has about half the sliding friction of the equalette master point (confirmed by measurements) and since the upper troublette bears only half the total force, the relative merit as far as sliding friction goes compared to the equalette is moot. The 4-placement version uses two troublettes joined together by a third and is nominally 25/25/25/25. When it comes to adjusting for any shift in direction of forces on the master point, troublette anchors adapt whereas equalette versions do not.

I am well aware that the design could be constructed with a single cordelette (long accessory cord runner) or in some cases with slippery Spectra/Dyneema runners while avoiding failures due to knot slip. I'm also aware that some of the designs proposed in the "Sliding x..." thread (such as mhabicht's) are similar and could be modified to eliminate problems (such as figure-8 knots "clipped in the butt") and achieve similar results. There are important points regarding the relationships of the limiter sections (in any design) that should be dug out of the "Sliding x..." thread before using these schema. This isn't a recipe, it's an illustration of what I believe to be the new school understanding: "perfect" equalization is not the objective of multiplacement anchor building--it can never be achieved, due to friction. The objectives should be to align the pro and cord so that the placements work together to achieve mutual security, abandon attempts at geometric equalization in favor of reducing friction at carabiners (which means reducing the number of strands running around carabiners), and ensure redundancy of load distribution so as to minimize adverse consequences of any single placement failure.

Are these the final words on equalized, multiplacement anchors? Doubtless not. There are many details that were addressed in the long "Sliding X..." thread and, if details are in your thoughts, you should go there. But the conclusion is clear: there is no simple recipe, no holy grail, for constructing effective equalized anchors. The best results will come from thoughtful compromises after abandoning some sacrosanct old school wisdom.

The Mountaineering Handbook,"]Mr. Friction is not your friend.

your master point is only 11kn now, as your going off of a single strand of a sling.

The equalette master carabiners are together supported by four strands, but that's why there's twice the sliding friction compared to the troublette.

The problem was/is that the important issue of carabiner friction was pretty much ignored. John Long put out some hints, but IIRC only two posters, charlesjmm and I, specifically focused on the effect of carabiner friction and offered any data.

Everybody should carry a chalk bag full of lard and smear it generously on all the carabiners and slings when they build an anchor, so they don't have to worry about friction.
Metolius could formulate a special anchor lard.
Or John Long could trade off his name, and market Long's Own Lard.
Include a free tube with every copy of his next anchor book.

This is a misunderstanding. Jim is perhaps distracted by the limiter knots and other things above the master point. The master carabiner is supported by two strands (one on each side) and should be good for 22 kN (based on BD runner specs), the same strength as typical HMS lockers. The equalette master carabiners are together supported by four strands, but that's why there's twice the sliding friction compared to the troublette.

Everybody should carry a chalk bag full of lard and smear it generously on all the carabiners and slings when they build an anchor, so they don't have to worry about friction.
Metolius could formulate a special anchor lard.
Or John Long could trade off his name, and market Long's Own Lard.
Include a free tube with every copy of his next anchor book.

Still, is a troublette, pre-tied generic or ad hoc, significantly better than a garden variety sliding-X? Only testing with fall-simulating forces can ultimately answer this question.

I heard a lot about the Idyllwild accident but in that case all the placements pulled- that is placement failure- not cordolette failure.
-pip

Isn't the issue (that we're all trying to address) the distribution of force across the pieces in an anchor? I.E. eliminating cascading placement failures due to a lack of force distribution.

If it were the strength of the cord used in the anchor that was the problem...it'd be a quick fix; bigger, stronger cord.

But it's what the cord is, or is not, doing to the pieces in the anchor. I don't think anyone here thought the problem with the cordelette was that we could snap the cord like your implying....

Jim

charlesjimm (and others), I am wondering if there is or should be any concern about the location of the limiter loop. In the initial proposed designs, the loop is on the spine of the carabiner. In your field test, the loop is on the gate side of the carabiner.