ACR Anchor Method?

Colin Parker wrote:Most of the materials I've read cover systems utilizing a static cord. I've been using an equalette for about 4 years now. Where should I go to learn the appropriate technique for building an anchor with the rope? I'm curious to know how equalization is achieved...

Here is a method for tying in with the rope that is somewhat standardized and works for many situations. But there are times when some ingenuity and creativity are the best tools for adapting to what is available.



As for "equalization," it is something of a myth, regardless of what system you use. Fixed-arm systems like the one depicted distribute the load but do not equalize it. For more than two anchor pieces, I don't think there is any evidence that real equalization is consistently obtainable with any system that is practical to use in the field.

Jim Titt wrote:Well, as usual the DAV have done this one (Panorama 2/2009, also interesting for the dynamic and static tests on various sling materials tied with a clove hitch). 5m drop, 80kg, dynamic rope belayed with HMS on sliding X with 60cm legs. Hanging belayer weight 65kg. Single leg failure gave 40% higher force than the same test with no extension. Jim

In real life conditions the piece normally doesn't blow without first absorbing (quite a bit) of energy, I have a feeling this worse case scenario doesn't take that into account... On top of that, 60 cm is a very long way to a piece without any protection from extension. If your playing around with an extendable anchor, made from trad gear, when there's a possibility of someone taking high factor fall directly onto the anchor, AND in a hanging belay none the less... you should really question your abilities of risk assessment, your desire to live, and seek instruction from a professional before climbing again.

When your top piece blows and sends you down another 20 feet, there's no super elevated "shock loading" of the next piece down, the force just ends up being just a tad higher than it originally was, because before your gear broke rock, a lot of energy was transferred into it, lowering the forces. It doesn't send your belay partner flying towards the sky from "shock loading". AND.. if the blown piece was the least bit solid before blowing, our belayer would feel the fall, twice, rather than being "shock loaded" with one super elevated imaginary force all at once. What you guys are suggesting requires something to only be holding the blown leg of the anchor there until the force is applied, and then releasing it, combined with moronic belay configurations. Of course a piece of blown gear extending 60cm and thus dropping an additional person onto it, is going to result in a higher load.

Now what happens in a more realistic scenario.. say, a non-hanging belay, with a more reasonable 20cm extension, because we were smart enough to use a sling to extend that far away piece. Now our climber takes a fall shortly up the route, and since he was also smart enough to pre-place protection before leaving the anchor, instead of taking a factor two fall, he lifts his partner off of their belay stance, and a much more likely event plays out, in which case a nut placed for downward pull is lifted out of place, and our belayer shits his pants, but soon realizes what he read in his climbing books was true, and this "shock loading" term, is being tossed around incorrectly. But even if there was a factor two fall and a blown piece in this situation, the forces wouldn't be amplified anywhere near 40%.

Russell Bangert wrote: In real life conditions the piece normally doesn't blow without first absorbing (quite a bit) of energy, I have a feeling this worse case scenario doesn't take that into account...

In the case of a fall onto an extending anchor, blowing a piece will not absorb any fall energy, if by "absorb" you mean, as you should, a process that ultimately lowers the peak force.

The reason for this is that in order for the ultimate peak force to be reduced, the rope, which has stretched to absorb fall energy, has to be able to spring back and "start anew." This springing-back does occur (yes, it has been tested and documented) when a piece blows in a leader fall, because there is a brief interval when the rope is unweighted before the next piece is engaged. Nothing like this happens when an extending belay anchor suffers the failure of a piece; the continued fall of the leader and now also the belayer keeps tension on the tie-in and prevents any resetting of rope tension.

Hence, there will be no absorbing effect from a blown piece in the belay anchor and there is nothing here for the worst-case scenario to "miss."

Russel Bangert wrote:On top of that, 60 cm is a very long way to a piece without any protection from extension.

Agreed. That's a two-foot extension in the U.S. You'd have to be pretty incompetent to set something up like that. But remember that the real issue is not the extension by itself, but the ratio of the extension to the length of the belayer's tie-in, so shorter extensions are not automatically safer.

Russel Bangert wrote: When your top piece blows and sends you down another 20 feet, there's no super elevated "shock loading" of the next piece down, the force just ends up being just a tad higher than it originally was, because...

None of this is relevant to a factor-2 all onto the belay.

Russel Bangert wrote:Now what happens in a more realistic scenario..

The "realistic" scenario provided is constructed not to test the belay anchor. All proper arguments about anchors have to address the worst-case scenario, because almost everything, competently constructed or not, works in most cases.

At the end of this quote, we get a totally unsupported appeal to the author's authority,

Russel Bangert wrote: But even if there was a factor two fall and a blown piece in this situation, the forces wouldn't be amplified anywhere near 40%.

Maybe or maybe not. We really don't know, and let's hope no one has to find out the hard way.

The bottom line is that, for anchors involving three or more pieces, there doesn't seem to be any clear evidence that "self-equalizing" systems, in spite of their theoretical advantages, can defeat their inherent friction and so do any better, on a regular basis, then fixed-length systems.

Nonetheless, a self-equalizing system that can be simply and rapidly deployed (like the ACR) may have some uses. If a piece does blow, then even with friction such systems can be far better at distributing the load than fixed arm systems. Here the trade-off ends up being between higher anchor loads because of the extension and the entire load being sequentially transferred to a single piece, neither scenario being exactly appealing.

The ability of a self-equalizing anchor to reorient can also occasionally be useful. Although I almost never use them, I did recently set one up for the following situation: the leader's first piece was obviously going to be a small cam in a horizontal a short distance horizontally from the belay, after which the route went up. A leader fall would pull the belayer (me) sideways, but if the small cam (blue alien) blew, the pull would be straight down. I had a two-piece anchor for this, both pieces excellent, but I couldn't get in any more, so I used a sliding-X. The leader did fall in this case, and their next piece pulled, producing a factor 1.8 fall onto the blue alien, which held, but only after pivoting towards the belay so that only two cams were left in the crack---it very nearly blew as well. Had it gone too, the reorienting ability of the self-equalizing belay would have been put to the test.

Had I used a fixed-length tie-in in and had the blue alien failed, one piece of the anchor would have gotten the load horizontally, followed by a vertical loading of the other piece. In this case, momentary slack in the leader's rope would have allowed for energy absorbtion when the blue alien failed, so that the subsequent fall would not be factor 2.

I think these particular pieces were each excellent, but am certainly glad I didn't have to find out whether my judgements were accurate or not, and consider the use of the reorienting property of the set-up to have been a wise choice in retrospect.

Bumping this thread to ask two questions:

1. Anyone have any new thoughts or ideas? It's been a few months since anyone has weighed in.

2. Any new thoughts on integrating an upward pull piece into this anchor? The last suggestions (IIRC) were just an upward piece rigged to a sling clipped to either the power point or the belayer's harness. Thoughts?

John Braun wrote:Bumping this thread to ask two questions: 1. Anyone have any new thoughts or ideas? It's been a few months since anyone has weighed in. 2. Any new thoughts on integrating an upward pull piece into this anchor? The last suggestions (IIRC) were just an upward piece rigged to a sling clipped to either the power point or the belayer's harness. Thoughts?

Thoughts no but I´ve done a lot of testing on the various systems over the last few months, the ACR performs just the same as a conventional sliding X in the equalisation stakes with an off-angle load, in other words badly (Load Split 16%/28%/56%) and with failure of one of the outer pieces the impact force on the centre piece is just over double that of a fixed (no extension) setup.

After hearing what Jim has to say, I'll add some thoughts that are somewhat new for me:

(1) Sliding systems are similar to fixed systems in performance if none of the anchor pieces blows, and do not confer equalization advantages.

(2) An emerging rule of thumb for any anchor rigging is that one of the pieces is likely to get half the load.

(3) If one of the anchor pieces does blow, then sliding systems seem to be worse than fixed systems in terms of the increased load to the remaining pieces.

Ultimate conclusion: don't use sliding systems for three-point anchors.

I'd like to see the test results, including all the details of the test circumstances that lead to these conclusions.

+1

Anybody know a link for where we can find them?

paulraphael wrote:I'd like to see the test results, including all the details of the test circumstances that lead to these conclusions.

I´m afraid you´ll have to wait until I´ve finished writing it all up, the whole subject of the dynamics in belays is complicated and the amount of testing to get reliable and realistic results is enormous.
Or would you like a short paper specifically on the ACR which fundamentally no worse than other similar systems but has no specific advantages either.

I'm sure we can all wait for the whole whole report. I'm glad you're planning a thorough writeup.

Jim Titt wrote: I´m afraid you´ll have to wait until I´ve finished writing it all up, the whole subject of the dynamics in belays is complicated and the amount of testing to get reliable and realistic results is enormous. Or would you like a short paper specifically on the ACR which fundamentally no worse than other similar systems but has no specific advantages either.

I would be interested, in the face of all this postulating, how many users on this site have ever actually had a partial belay anchor failure...one, two pieces blowing....

My bet: < 1%.

Mike wrote:People probably hate to see posts like this in threads like these, but... Why not just anchor with the rope instead of bringing all the extra thingamajigs along? You are already tied in to a super-strong, super-dynamic cord. Just use it.

+1 here, the simplest system is the best! Also, although I understand the twist in the cordelette around the rap ring, anytime you twist a cord/rope you also weaken it! Great to know how to do, but I see minimal useful applications. Cool post!

BirminghamBen wrote:I would be interested, in the face of all this postulating, how many users on this site have ever actually had a partial belay anchor failure...one, two pieces blowing.... My bet: < 1%.

That's because most climbers are careful enough to avoid falls onto the anchor altogether. Anchors aren't important because you're likely to fall onto them, but because of the catastrophic consequences in the rare case that you do and the anchor fails.

The low number of factor-2 falls is why threads like this go on for so long, fueled mostly by speculation. We lack the real world experience to know for sure what works and what doesn't.

paulraphael wrote: That's because most climbers are careful enough to avoid falls onto the anchor altogether. Anchors aren't important because you're likely to fall onto them, but because of the catastrophic consequences in the rare case that you do and the anchor fails. The low number of factor-2 falls is why threads like this go on for so long, fueled mostly by speculation. We lack the real world experience to know for sure what works and what doesn't.

Quite so. In fact the amount of armchair theorising and speculation on the subject compared with experience or even testing is amazing, probably the most discussed to no effect and misunderstood subject ever to crop up in climbing.

One reason for the difficulty is the moment you start to look at one part another slight difficulty pops its head up and the complications and variables become exponentially harder to keep in view, at least if a few more belays failed we would have something to work on.

To obtain a definitive answer (if there is one) and with help from others in the industry I decided to review all the available information and then do the testing required to give an accurate overview of the potential and pitfalls of every belay system. Currently I have performed over 400 hours of testing and have 700 drop and pull test tables (which normally are between 1500 and 2000 data sets each), 300 force diagrams, 80 graphics and 120 pages of notes, all of which have to be written up in a way the general public could understand. In my normal capacity as a climbing equipment designer and manufacturer I´ve done a number of similar projects but this is by far the worst and most complex.

The good news is that as far as I can tell it doesn´t really matter what you do, the number of different ideas related to the minimal incidence of belay failure is proof of this.

The bad news is that anyone who claims their system is `better´is wrong since in some circumstances this will be so and in others not.

Richard Gold´s advice and comments on this thread are well worth reading and remembering, he has a good grasp of the complexities and his opinions are almost 100% correct, a rarity in discussions on equalisation and belays in general.
John Long (who is probably most responsible for the entire equalisation controversy) is also on record stating that in his normal climbing he just uses the rope, like every experienced climbers always has done and probably will continue to do.
Having tried and tested every possible (and some pretty impossible) systems I too will continue to join up a load of pieces of gear in a generally haphazard way and clip the rope into them, confident it won´t get any better unless I use a couple of bolts.

Jim Titt
Bolt Products
Germany

Thanks for the research Jim. Looking forward to reading that report.

Interesting how the actual research is starting to verify what the old farts have been saying about all these different anchor methods since this nonsense first started getting espoused.

When it comes to actually understand the physics involved in this a little bit of knowledge is a dangerous thing. I agree that most of the discussions around anchors and anchor building are full of emotions and rhetoric. Some people seem to be very emotionally attached to the subject. Glad to see honest and applicable research happening. This could go a long way towards dispelling many of the myths that are commonly held by climbers regarding their preferred belay anchor.

John Braun wrote:Bumping this thread to ask two questions: 1. Anyone have any new thoughts or ideas? It's been a few months since anyone has weighed in. 2. Any new thoughts on integrating an upward pull piece into this anchor? The last suggestions (IIRC) were just an upward piece rigged to a sling clipped to either the power point or the belayer's harness. Thoughts?

ACR-VV (vince variation)
In my first post to this thread a year or 2 ago, I referred to a variation of ACR that I have used which incorporates a 4th leg for the upward pull, affectionately "the vince variation". I have always tied the ACR this way since it came out. 3 pieces were great but I always used one for the upward pull in any anchor I built and 2 for the top just didnt do it for me. Now 3 for the downward and one for the up makes me happy. I always wanted to post a picture of my alleged ACR-VV but never got around to it until today @ Carderock, MD.

I have always carried 2 ACRs on lead and at least one was the "VV". I use the regular flavor sometimes on ICE for building that bomber anchor with 3 screws.

I am not endorsing this setup for anyone else to use and I don't mind if you do or not, it's just what I have used for years and feel confident I could hang a truck off this anchor.

Jim Titt wrote: I´m afraid you´ll have to wait until I´ve finished writing it all up, the whole subject of the dynamics in belays is complicated and the amount of testing to get reliable and realistic results is enormous. Or would you like a short paper specifically on the ACR which fundamentally no worse than other similar systems but has no specific advantages either.

Jim, did anything ever come of all your research, testing, and notes? It sounds like you put quite a bit of effort in, and I'm sure a lot of us would love to see the writeup. This post is from over two years ago, so I'm sorry if you posted somewhere else and I've missed it.

wow I took this last picture...man how time flies...I have been ice climbing more than climbing rock.... love to read more info on this

At the top of this page is someone who talks about the inferiority of "sliding systems".

Recently DMM showed a video of how badly the strength of slings is reduced by any type of knot (particularly dyneema slings). So, "equalizing" a sling that's put through 2-3 pieces by knotting it, does indeed make for a redundant anchor, but apparently one severely compromised in strength.

Have opinions changed regarding the non-redundant, but sliding ACR after this video?

The DMM video showed that rope is vastly superior to slings, but it's pretty complicated to even roughly equalize with rope, isn't it?

-TPC

It's important that you view the right DMM videos, there are many of them.

More dramatic, with some exploration of “shock loading”

youtube.com/watch?v=Vrgadjo…

Slower, more data:

dmmclimbing.com/knowledge/h…

Previously I referred to another poster's link, but that DMM video is something else entirely, about dyneema cord.

Nothing new about knots reducing strength. But a typical cordelette with 3 pieces has 6 different strands. I wouldn't worry about strength loss to the knot.

And no, it isn't at all complicated to build an 'equalised' anchor with climbing rope. I an many others do it all the time. It is quick and easy.