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ACR Anchor Method?
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By Greg D
From Here
Dec 3, 2010
Out of the blue.  Photo by Mike W. <br />

Mark Nelson wrote:
I say forget those unwarranted fears of shockloading and redundancy, make your anchors distribute loads with solid pro, good angles, and move fast.


Yes! Yes! Oooo. Mark. Talk to me baby.


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By Brendan Blanchard
From Strafford, NH
Dec 3, 2010
Obi Wan Ryobi - Darth Vader Crag, Rumney NH

JPVallone wrote:
If you needed this configuration for what ever reason, then wouldn't the locking carabiner in place of the ring accomplish the same thing without the extra piece of gear?


Yes, like stated above, but you would have to incorporate the third loop into the biner, and that would increase rope to rope friction by adding that loop to the mix. At that point, you might as well have a peak at the Sliding X configuration, that would be what it would essentially be.


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By Larry
From SoAZ
Dec 3, 2010

Joe Lee wrote:
There is no redundancy in the cord. If it frays over a sharp edge, the entire system fails.


That problem seems to be addressed by the backup clip-in to the strongest piece.


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By aaron hope
From Walnut Creek, CA
Dec 5, 2010
Staying Warm on South Face of Washington Column

Looks like I'm a little late here, but I've been using ACR for trad anchors for the last two years. Love it. Very quick setup. I learned it from some crusty Yosemite climbers who made the switch recently. I use 4 or 5mm spectra cord tied together(14-15KN)with a forged aluminum Omega Pacific rap ring (20 KN). Together, the set up is ridiculously lightweight and compact. Less than 3.0 oz.

It's true that there can be extension with the ACR if you're not careful. However, if you have one questionable placement, you can tie ONE leg of the ACR off to minimize extension without compromising dynamic equalization. IMO, ACR does such a good job at distributing load, that there is less of a chance of blowing a marginal piece by unconsciously load-favoring it. But if you really think that two or more legs in your system may blow, then maybe choose a different anchor method. Or find another place to build a belay. But I also tie into the anchor with the rope (not daisy) so there is some sort of stretch in the system if one or more pieces were to blow causing me to fall a couple feet onto the anchor.

ACR. Small and Lightweight.
ACR. Small and Lightweight.


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By rgold
From Poughkeepsie, NY
Dec 6, 2010
The traverse out to the Yellow Ridge on the Dogstick Ridge link-up.  Photo by Myriam Bouchard

The whole thing is perfectly equalized...

Who knows what effects friction will have, but the setup as pictured, in the absence of friction, distributes half the load to the leftmost piece and one-quarter of the load to each of the other two pieces.


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By rgold
From Poughkeepsie, NY
Dec 6, 2010
The traverse out to the Yellow Ridge on the Dogstick Ridge link-up.  Photo by Myriam Bouchard

What happened to the other 1/4 of the load?

I left an "each" out. Reread my comment, I edited it.

Perhaps I should have said it's as equalized as you are going to get it in a real world situation and left the physics to the math geeks.

Leaving physics to the math geeks is almost, but not quite, as dangerous as leaving mathematics to the physics geeks.

And the ACR, for example, does a better job of equalization.


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By Jon H
From Northern NJ
Dec 6, 2010
At the matching crux

aaron hope wrote:
Looks like I'm a little late here, but I've been using ACR for trad anchors for the last two years. Love it. Very quick setup. I learned it from some crusty Yosemite climbers who made the switch recently. I use 4 or 5mm spectra cord tied together(14-15KN)with a forged aluminum Omega Pacific rap ring (20 KN). Together, the set up is ridiculously lightweight and compact. Less than 3.0 oz. It's true that there can be extension with the ACR if you're not careful. However, if you have one questionable placement, you can tie ONE leg of the ACR off to minimize extension without compromising dynamic equalization. IMO, ACR does such a good job at distributing load, that there is less of a chance of blowing a marginal piece by unconsciously load-favoring it. But if you really think that two or more legs in your system may blow, then maybe choose a different anchor method. Or find another place to build a belay. But I also tie into the anchor with the rope (not daisy) so there is some sort of stretch in the system if one or more pieces were to blow causing me to fall a couple feet onto the anchor.


I've been tying mine out of 7mm perlon, but I really like the look of yours. Does a tremendous job at cutting out the bulk. I think I'm going to head to 5.5mm tech cord. FWIW, I would be very cautious about going down to 4mm spectra cord... that makes your margin of safety VERY thin.


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By rgold
From Poughkeepsie, NY
Dec 6, 2010
The traverse out to the Yellow Ridge on the Dogstick Ridge link-up.  Photo by Myriam Bouchard

Just another MP douche wrote:
Now I'm not a math wizz but I would think that you are actually loosing only 17% of "perfect" equalization? Please correct me if I'm wrong, and please go into great detail. Graphs and perhaps a pie chart or two would be nice.


Sorry, but you are still wrong. And now also imprecise---what exactly does "losing 17% of perfect equalization mean? I gave the theoretical distribution, which, of course, will be modified by the presence of friction (but not necessarily in the direction of better distribution). This particular configuration has been discussed over and over and over, there's nothing new about my comments. Try a search. They've got a whole server's worth of commentary over on rockclimbing.com, for example.

As for the who-needs-perfect-equalization-rant, you're the one who brought up perfect equalization with a set-up that doesn't come close, and you did so in response to a thread about something that does better.

Just another MP douche wrote:
Although you've probably got a theory that proves why this is better it seems to be a pretty good instance of where having better equalization would make an overall weaker system.


Now you are arguing with yourself, deciding that the failure of perfect equalization you originally proclaimed is actually a good thing, based on your evaluation of pieces stuck on a woody.

Meanwhile, I haven't commented either way about the need, if there is one, for equalization. I don't use the ACR, I tie in with the rope almost all the time, and my only observation is that of all the so-called equalizing systems, the ACR seems to be about the best.


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By Jesse Davidson
From san diego, ca
Dec 6, 2010
n cascades <br />

for those of you who say build the anchor with the rope, what do you do when you don't swap leads? Untie and then tie into the other end of the rope?


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By Buff Johnson
Dec 6, 2010
smiley face

Maybe another solution on that kind of switch instead of untie & retie; is 8 bight the rope ends and oppose dual hms lockers making the switch back to lead easier.


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By Larry
From SoAZ
Dec 7, 2010

Jesse Davidson wrote:
fwhat do you do when you don't swap leads?


Re-stack, or flip the stack, or just feed from the bottom.


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By Buff Johnson
Dec 7, 2010
smiley face

I don't see that working out when the rope is the anchor.


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By kennoyce
From Layton, UT
Dec 7, 2010
Climbing at the Gallery in Red Rocks

Justin Baker wrote:
What are you thoughts on the ACR Anchor Method: The Alpine Cock Ring Seems kinda cool, but also kidna gimmicky. One concern is clipping a biner to the rap ring. I have always been told biner to biner is bad practice, so is this the same kind of thing?


Have you never clipped a biner to a rap ring (or a chain link for that matter) at a belay station before? There is absolutely no problem clipping a biner to a rap ring, especially if it is a locking biner like you would use at a belay.


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By Larry
From SoAZ
Dec 7, 2010

Mark Nelson wrote:
I don't see that working out when the rope is the anchor.


Oh yeah right.

Either clove the second into a second biner on each piece, or slide the leader's clove out of the way, then clove the second in. Maybe use fig. 8 for the second instead of clove. Fewer strands per biner that way.


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By goatboywonder
Dec 7, 2010
Hiking around Lumpy

rgold wrote:
The whole thing is perfectly equalized... Who knows what effects friction will have, but the setup as pictured, in the absence of friction, distributes half the load to the leftmost piece and one-quarter of the load to each of the other two pieces.


Not trying to start anything here but I am not sure how you get this. Can you explain a bit more or point somewhere that does? Here is what I get:

If we neglect friction, we can assume that the tension in the cord is constant. We'll call that T. Each arm has two cords so isn't the force on each piece simply 2T? It seems (in a frictionless world) to be perfect balanced, regardless of the geometry.

Again, not trying to be a smart-ass, just a geek.


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By paulraphael
Dec 8, 2010

Lots of good points all around. I'm the guy who originally came up with the ACR, and am happy to see that some people have used it even more than I have.

My assumption is that there's still room for refinement, and also probably some undiscovered tricks and applications. I think the ACR would benefit from becoming open-source ... something hosted on a wiki page instead of just a static PDF on my personal site.

If anyone would be interested in contributing to an effort like this, please let me know.

It might also help put some weight behind it, so we could more easily convince the engineers at Black Diamond or Sterling to do the kind of drop tests we all want to see (in order to learn the real world effects of friction, etc).

Cheers,
Paul


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By rgold
From Poughkeepsie, NY
Dec 8, 2010
The traverse out to the Yellow Ridge on the Dogstick Ridge link-up.  Photo by Myriam Bouchard

goatboywonder wrote:
Not trying to start anything here but I am not sure how you get this. Can you explain a bit more...




Pulley Effect
Pulley Effect


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By slim
Administrator
Dec 9, 2010
tomato, tomotto, kill mike amato.

rgold, is this diagram for the ACR setup?


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By goatboywonder
Dec 9, 2010
Hiking around Lumpy

And the nerd-fest continues...

OK, I see where the confusion is. The free body diagram you posted is composed of two cords, each with fixed ends, but the ACR is not arranged that way. It is a single loop of cord with no fixed ends (the knot does add some constraint, though). Consider this (poor quality) FBD:

ACR Free Body Diagram
ACR Free Body Diagram


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By slim
Administrator
Dec 9, 2010
tomato, tomotto, kill mike amato.

i agree. rgold's diagram shows a 2nd pulley, which i don't see in the ACR setup (the ring and the biner that has the strand from piece A to piece C move in tandem).


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By paulraphael
Dec 9, 2010

Rgold's diagram shows a different anchor (setups like the equalette will distribute loads asymmetrically like that, when rigged for three pieces of pro).

The ACR distributes loads symmetrically in most of its iterations. There are ways to use it (like with four pieces) that are asymmetrical.


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By rgold
From Poughkeepsie, NY
Dec 9, 2010
The traverse out to the Yellow Ridge on the Dogstick Ridge link-up.  Photo by Myriam Bouchard

What happened here is that someone, I think the name was Just Another MP Douche (yeah, that's it I think) posted a picture of something that works exactly like the schematic diagram I posted, claiming it had "perfect equalization." After some corrections, Mr. Douche deleted all his posts, leaving my response without any antecedent.

The original subject having now vanished, I guess people interpreted my post as being about the ACR. But I was never talking about the ACR.


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By slim
Administrator
Dec 10, 2010
tomato, tomotto, kill mike amato.

rgold - that makes more sense. so, my big question is how is the ACR really that different from a simple cordalette setup with no limiting knots? i don't really see a big difference, other than the addition of the rap ring.(?)


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By Larry
From SoAZ
Dec 10, 2010

Regular cordalette trades poor equalization for no extension.

ACR trades extension for better equalization.


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By slim
Administrator
Dec 10, 2010
tomato, tomotto, kill mike amato.

i guess i can see maybe a slight improvement in equalization (due to fewer strands running over each other in one place), but it would be interesting to see how much better. i guess for me it is somewhat of a moot point, as i fall into the "anchor with rope" which offers better equalization AND no extension.


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