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Neoshade
Aug 17, 2011, 10:12 PM
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OK, please don't hate, this is one of my first posts, and I KNOW that everyone is sick of equalette and other invented anchor discussions, especially from those who haven't read every single comment and thread so far, and John Long is probably getting death threats from trolls and old-school climbers alike. However, I gotta throw out another one. (assuming it hasn't been done already)
One more caveat - I really love that the discussion that's been going on, and I truly believe that better anchor designs are forthcoming, and that awareness and discussion and testing are a GOOD thing, despite the massive amount of overdesign and confusion (this stuff is for mostly trad and alpine anchors that need equalization for safety.
So, as many people have noted, a more complex anchor is less effective because it's difficult to make, has greater possibility for mistakes, and in the environments of alpinism and big walls, wasting time means losing daylight, freezing your partners, and then hurrying, which is far more dangerous than most fractional amounts of equalization and load sharing. I'll be the first one to admit that I've thrown a single 11mm sling over a rock horn and yelled "On Belay!" because we were way off course on a knife edge at 12,000' and it was getting dark.
So, aside from the dogged chase for SRENE perfection, a useful anchor should use standard climbing gear, rig quickly, and be simple enough for brief visual inspection.
I also second the need for a single master-point biner in all real word use. (double equalette biners are great for setting TR anchors with pro at your weekend crag, but impractical for trad climbing)
On that note, I tend to ignore the 2-biner redundancy for equalettes, and just sliding-x the thing. I just don't care that much about friction binding on the X. It's so much better than the cordalette, when dynamic equalization is needed, let's not split hairs.
On the subject of equalization - I don't know how John Long's tests were conducted for off-axis loading, but from what I've noticed in the Real World, the rope is pulled and wiggled in the direction of a fall while climbing before a fall takes place. So, if the anchor is pulled in the direction of the impending fall ahead of time, as the climber moves around, then it's pre-equalized in that direction already, and any friction binding of the X is not a concern.
Lastly, I love the 2 leg equalette, It's my new go-to for sport routes with anchor bolts in weird places (not side-by-side) and it's stupid simple to tie, keep tied, and it works. It's really just a sliding X with limiter knots if you're only using 2 legs and a single MP biner instead of 2.
Lots of the variations on this so far are really great, like the tripplette, clove-hitching the pro on a sliding W, and Paul Raphaelson's and others' methods of just throwing a sling or climbing rope clove on additional pro (3rd or 4th piece) and leave the primary rig alone.
My rigging solution is a very simple adaption to the equalette or almost any of these ideas.
The limiter-knotted sliding X, or with double MP biners, the equalette is great with 2 legs, but has trouble maintaining simplicity and equalization with 3 or 4 pieces. And if it's not equalizing, or it's hard to get tied right, then screw that; you might as well use a cordalette or any other simple, classic method (ie: climbing rope cloves with a MP knot).
So, as others have mentioned using knots other than a clove hitches to each piece to get an equalette leg unto multiple pieces of pro, how about Ultrabiker's figure 8?
The knot is a double figure 8 on a bight, with Ultrabiker's modification being to use each of the three loops created as legs of an anchor.
It's an amazing knot for adjusting legs, as one strand from each leg slip-knots through the knot to the next leg, so that it can self-equalize as long as it's not loaded, just by pulling the 8 around.
However, as an anchor rig itself, it's not at ALL redundant for cuts, it can possibly extend if the rope slips through the knot, and the MP itself lacks stout redundancy in having all single strands and only 1 knot to rely on for the whole rig.
BUT - this knot is perfect for a secondary anchor on a cordallete or equalette.
Each lef of a Double-Figure-8-on-a-bight can self-equalize, and the whole thing can be adjusted for length pretty darn easy.
My preference is to find a good anchor for 2 or 3 peices, whatever works for my situation, and then just throw extra slings or draws at additional pro as needed to extend legs, or make a meta-rig (if there's a better term, illuminate me :P) to eqaulize two pieces before connecting them to a single leg.
basically, tie a 2-leg equalette, or 3 leg cordalette, and then throw a little sliding-X on any extra pieces and clip them to a leg.
This not only keeps the anchor simple, uses gear you've got on you, and keeps the SRENE properties of the primary rig, but allows far greater equalization and customization for the circumstances.
Don't make your primary rig too complex. Just fix your pro as needed and use a simple anchor.
So, the culmination of all this blab (really, I could have just used quotes from all over these forums, I know) is that there is a way to take the simple 2-leg limiter-knotted Sliding X or an Equalette, and add additional pro at no further cost to you or your tired brain!
1) Make yourself your favorite 2-peice anchor rig with some 20' cordalette or whatever, use those limiter knots and slings to extend pro as you feel necessary.
2) Take a leg that needs to be split among 2 pieces of pro, and tie a Double-Figure 8 on a bight (a 2 second knot with your eyes closed) and clip the loops of the double 8 to the pro.
3) Congrats! You've now got a meta-rig that will self-equalize with just a bit of wiggling until it's loaded, and can be adjusted with a simple squeeze-push-fiddle-pull at any time thereafter, easier than a clove.
http://www.flickr.com/...2896@N00/6054296344/
Pros:
- It won't mess with your primary rig and its SRENE properties.
- It will self-equalize between the peices before loading, while using only a knot in the 7mm perlon (or whatever)
- It will slip a little under load, further equalizing, not perfectly, but darn well.
- Any extension to do failure of pro is small and not worth caring about, because the knot doesn't slip much, and cause it's a little meta-rig, not your whole anchor.
- The whole darn thigs ties and equalizes in a few seconds.
Cons:
- Doesn't self-equalize perfectly. Needs Wiggling.
This is for real world stuff, where we're either at the belay to give it a shove as needed, and where the climbing is being actually belayed, with the rope tugging the anchor around enough to get it equalized-ish. That's all we're looking for. Load distribution among pieces of pro, not laboratory pefect equalization. Also, this knot allows some slippage, enough to provide the distribution of force we need.
- Shortens up one side of an equalette, so now your limiter knots aren't in the middle!
Oh no! Just go tie another knot on the other leg. Use up some rope. Like a fig8 perhaps? That should about even it out. :P Otherwise, this is a common problem with the equalette, not so much my knot application.
- I'll wait for you guys to fill in the rest :)
Lasty, let's not name anything else with a "lette", shall we? Neoshade's Rig, whatever. And if this has been done by someone else, and completely debunked, feel free to trash on me all you want. I'd deserve it.
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patto
Aug 17, 2011, 10:40 PM
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Nothing is wrong with a simple cordalette setup. Or even better use the damn climbing rope.
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Stormeh
Aug 17, 2011, 11:59 PM
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Your pictures are very pretty. Also, seems like a good setup. I'd use it in place of the equalette but I'm not exactly sure what the advantages are using the double fig 8 over just cloving one strand of the leg to each piece as in the classic equalette.
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mbrd
Aug 18, 2011, 12:49 AM
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c'mon, "neoshadelette"? doesn't that sound swell?
(gotta edit this- i wasn't referring to you as "neoshadelette")
(This post was edited by mbrd on Aug 18, 2011, 12:51 AM)
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Neoshade
Aug 18, 2011, 4:17 AM
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Dear Patto,
I love cordalettes, I've been using them for years, but we now know that a cordalette doesn't equalize for shi* when loaded off-center. Even just a inch or two off center. So while it's all well & good for most climbs and TR anchors, it is in great need of a replacement for trad traverses and crappy pro that needs a decent distribution of the load.
If you don't care, use the cordalette for everything. You probably won't die, and will more likely never climb anything sketchy enough to need equalization. Good for you.
No one's telling you what anchor to use, this is The Lab, and we're discussing theory.
Dont' troll.
(This post was edited by Neoshade on Aug 18, 2011, 4:18 AM)
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Neoshade
Aug 18, 2011, 4:28 AM
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In reply to: "Stormeh"...I'd use it in place of the equalette but I'm not exactly sure what the advantages are using the double fig 8 over just cloving one strand of the leg to each piece as in the classic equalette.
I haven't had a chance to take any whippers on it yet, and will post back when I do, but let me know if you or anyone wants to give it a go. I really want to see how well it equalizes the arm parts under a fall.
And that is also the answer to your question - it beats cloves because it equalizes the 2 pieces on the arm of the equalette (or whatever you're tying). Cloves don't do this at all: If you swing the MP around, only one of the two pieces of pro is getting the load of the whole arm.
Cloves are great, but the idea is that this is just as fast, equalizes much better, and even easier to adjust.
Tie it (if you know the double 8) and yank it around. It self-adjusts most of the way with a loose knot, and will equalize further under load. It's pretty sweet.
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Neoshade
Aug 18, 2011, 4:32 AM
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*Note
The Pros and Cons I mention near the end of my post, referring to "the knot" - I'm just talking about the use of a double-8 on the leg(s) of an Equalette, Sliding X or similar anchor for additional pieces of pro.
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potreroed
Aug 18, 2011, 4:32 AM
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I've been climbing for 45 years and have never used a 'lette of any type. Why complicate things? I'm with patto on this one. Use the rope and the PAS which you'll have already girth-hitched on your harness if you're smart.
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mbrd
Aug 18, 2011, 4:39 AM
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really? no room for equalizing marginal placements to protect shady spots?
guess i'll never be a hardman...
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patto
Aug 18, 2011, 6:58 AM
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Neoshade wrote: No one's telling you what anchor to use, this is The Lab, and we're discussing theory.
We if we are going to discuss theory could you please explain how the above device equalises dynamically? Furthermore lets discuss how no extension and dynamic equalisation are mutually exclusive. Finally how about we discuss how extension in a typical scenario results in shock loading the anchor and can result significantly higher forces.
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Neoshade
Aug 18, 2011, 8:28 AM
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patto wrote: Neoshade wrote: No one's telling you what anchor to use, this is The Lab, and we're discussing theory. We if we are going to discuss theory could you please explain how the above device equalises dynamically? Furthermore lets discuss how no extension and dynamic equalisation are mutually exclusive. Finally how about we discuss how extension in a typical scenario results in shock loading the anchor and can result significantly higher forces.
I don't want to get to far into it, Really, much of all that has been discussed over and over elsewhere in these forums.
But basically, the Doudle Figure 8 will allow rope to slide from one loop to another a bit until the knot is loaded. That's what I mean by dynamic equalization - it equalizes on the fly as the rope moves. I'll look more into other discussions of the knot, most importantly how much slippage and equalization takes place under a fall load. Sorry, can't say yet. Good point. There are other tricks to make it slide continuously without ever tightening the knot though, should one wish. (I'll post later).
Also, extension causing "shock loading" and "significantly" higher forces has been debunked a long time ago. Jim Ewing at Sterling Ropes conducted load cell testing completely disproving the idea, showing there is almost no concern over small amounts of extension (a foot or less), that overall force was not increased during tests where a piece blew, and that "shock loading" is a vague term that doesn't apply to a system involving an elastic climbing rope.
Read Climbing Anchors by John Long. All that testing is in the book, the book which starting all this new anchor discussion.
Finally, This thing is suposed to extend if a piece blows. Not very much, that's the whole point of limiter knots and using this double Figure 8 as only a small part of the rig.
But nonetheless, I'm proposing the use of the double 8 based on the premise that you're up to date on the subject of small extension being OK, and moved on.
We're talking about starting with an equalette here, so if you don't like anything sliding with the understanding that some extension is inherent, then there's not much more to discuss (without repeating other, older threads).
See this thread for discussion on sliding X's, limiter knots and shock loading:
http://www.rockclimbing.com/...um.cgi?post=1306133;
And further details on the testing done:
http://www.supertopo.com/...id=307091&tn=108
(This post was edited by Neoshade on Aug 18, 2011, 8:30 AM)
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patto
Aug 18, 2011, 9:49 AM
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Neoshade wrote: Also, extension causing "shock loading" and "significantly" higher forces has been debunked a long time ago. Jim Ewing at Sterling Ropes conducted load cell testing completely disproving the idea, showing there is almost no concern over small amounts of extension (a foot or less), that overall force was not increased during tests where a piece blew, and that "shock loading" is a vague term that doesn't apply to a system involving an elastic climbing rope. Read Climbing Anchors by John Long. All that testing is in the book, the book which starting all this new anchor discussion.
Thinking that shock loading has been debunked is highly dangerous! It has not been. Shock loads can easily result in forces 10-20 times higher, this has been shown repeatedly in testing*. *Testing of masses taking high factor falls on static cord/sling.
The testing discussed was fundamentally flawed as there was no mass on the belay. High school physics would tell you that without a mass on the belay the 'shock loading' isn't a problem. However as soon as you add a mass to the belay such as a 80kg belayer then suddenly extension on the anchor becomes a big concern.
As far as your design goes Neoshade I have no issue with it. However I do wish to impress upon you and others that J. Long's book is highly misleading regarding 'debunking' shock loading.
Anyway I'll try to step away from the discussion. 
(This post was edited by patto on Aug 18, 2011, 3:49 PM)
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JimTitt
Aug 18, 2011, 10:24 AM
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Can´t see it´s equalised anyway, looks like 50/25/25 to me.
Equalising the right pieces by nylon sliding on nylon, you´re joking right?
Increased loading with increasing extension is inevitable, is real and not to be ignored.
Use the rope or clove hitches.
Jim
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billl7
Aug 18, 2011, 12:59 PM
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JimTitt wrote: Can´t see it´s equalised anyway, looks like 50/25/25 to me. Equalising the right pieces by nylon sliding on nylon, you´re joking right? Increased loading with increasing extension is inevitable, is real and not to be ignored. Use the rope or clove hitches. Jim
+1 on all the above points.
I used the equalette and a variation of it for quite a while. I've pretty much gone back to simpler means.
It is worth repeating that the primary anchor quality is bomber individual pieces. If there aren't good placements: continue the climb until there are, downclimb until there are, bail on a couple of the iffy placements*, or consider finding a very good stance and hope your partner won't be too pissed.
Bill L
* Edit: If you really feel like you've gotten yourself into a situation where you must use them, equalize two or three and rap (endanger only yourself).
(This post was edited by billl7 on Aug 18, 2011, 1:31 PM)
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dan2see
Aug 18, 2011, 1:53 PM
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Thanks for showing us your alternate method for anchor-building. Ideas like this are interesting and should always be analyzed.
But ... (hey you knew there'd be a "but")
Sometimes I'll try something, but every time I get creative, I get into trouble. It's not worth it.
So when I see a pair of bolts, I make an equalette or "X", and on gear I stick to cordalette.
No fooling around, stick to standard methods. Get it done and get it on.
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kaizen
Aug 18, 2011, 2:08 PM
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patto wrote: Thinking that shock loading has been debunked is highly dangerous! It has not been. Shock loads can easily result in forces 10-20 times higher, this has been shown repeatedly in testing. The testing discussed was fundamentally flawed as there was no mass on the belay. High school physics would tell you that without a mass on the belay the 'shock loading' isn't a problem. However as soon as you add a mass to the belay such as a 80kg belayer then suddenly extension on the anchor becomes a big concern.
Patto - do you have any reference for these subsequent tests? I've seen you post this in other threads, and have yet to find any further tests that back up that statement. Not trying to pick a fight, just genuinely curious what you're referencing.
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rgold
Aug 18, 2011, 3:02 PM
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There are no further tests that I know of. (*) Patto's comment is based on the description of the original tests, which makes it absolutely clear that (1) they do not model what can happen with a factor-2 leader fall onto the anchor in the real world, because, as he says, the tests contained no mass corresponding to the belayer, and (2) the dismissive results of the tests as performed were easily predictable from the set-up.
The tests modeled a rope soloing fall of the climber onto an anchor that extends. The extension in the anchor was very small compared to the amount of rope in the system for absorbing fall energy, so it is no surprise that the conclusion was that the anchor extension mattered little.
Having a mass corresponding to the belayer is critical, because if the belayer is dragged off the stance, the only part of the system absorbing that fall energy is the belayer's tie-in, and the length of that relative to anchor extension could be small enough to result in much increased anchor loads.
(*) Edit: From Jim Titt in Germany:
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.
Of course, results like this were predictable and were predicted.
As for this anchor, it is a variation in the highly non-equalizing genre of 50/25/25 configurations, using a figure-8 variation instead of clove hitches to possibly getting better distribution to the two low-load pieces. If you need equalization, the ACR is a better bet. The rest of the time, I'd go with the rope by itself or (say on a wall) the classical cordelette.
(This post was edited by rgold on Aug 18, 2011, 3:41 PM)
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JimTitt
Aug 18, 2011, 3:39 PM
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As I´ve posted elswhere:-
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.
I wish John Long would sort his book out, generations of climbers have survived without all this (and his) pure speculation and half-baked ideas, though equalising by movement inside a knot has probably got to be the stupidest idea yet.
Jim
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patto
Aug 18, 2011, 3:57 PM
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kaizen wrote: Patto - do you have any reference for these subsequent tests? I've seen you post this in other threads, and have yet to find any further tests that back up that statement. Not trying to pick a fight, just genuinely curious what you're referencing.
I was more referring to the many tests of short falls onto static slings/cord. FF2 falls can result in 20x the forces. In the case of extension you are more likely looking around FF0.5 falls. The effects of shock loading a thus lower but still quite significant in the case of sling/cord.
JimTitt wrote: I wish John Long would sort his book out, generations of climbers have survived without all this (and his) pure speculation and half-baked ideas, though equalising by movement inside a knot has probably got to be the stupidest idea yet.
I'm glad somebody else has said it. I've been banging on about this for years but we continue to get new 'elettes' being invented based on a false premise.
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kaizen
Aug 18, 2011, 4:39 PM
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rgold wrote: There are no further tests that I know of. (*) Patto's comment is based on the description of the original tests, which makes it absolutely clear that (1) they do not model what can happen with a factor-2 leader fall onto the anchor in the real world, because, as he says, the tests contained no mass corresponding to the belayer, and (2) the dismissive results of the tests as performed were easily predictable from the set-up. The tests modeled a rope soloing fall of the climber onto an anchor that extends. The extension in the anchor was very small compared to the amount of rope in the system for absorbing fall energy, so it is no surprise that the conclusion was that the anchor extension mattered little. Having a mass corresponding to the belayer is critical, because if the belayer is dragged off the stance, the only part of the system absorbing that fall energy is the belayer's tie-in, and the length of that relative to anchor extension could be small enough to result in much increased anchor loads. (*) Edit: From Jim Titt in Germany: 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. Of course, results like this were predictable and were predicted. As for this anchor, it is a variation in the highly non-equalizing genre of 50/25/25 configurations, using a figure-8 variation instead of clove hitches to possibly getting better distribution to the two low-load pieces. If you need equalization, the ACR is a better bet. The rest of the time, I'd go with the rope by itself or (say on a wall) the classical cordelette.
RGold, thank you for this concise response, it is greatly appreciated.
Jim - do you know if there is an online publication of the study you mention?
Thanks for the explanation Patto.
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Neoshade
Aug 18, 2011, 4:40 PM
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JimTitt wrote: Can´t see it´s equalised anyway, looks like 50/25/25 to me. Jim
Wow. Big apologies. That was just blatantly stupid of me. I completely failed to address some major issues, and I definitely over-claimed the whole self-equalizing properties of this.
Also, sorry Patto for getting preachy and aggressive when I was treating John Long's work and the extension testing like gospel and just beating the bible at you. I think the community at large needs better, more extensive testing much more that it needs new rigging ideas in order to move forward right now.
1) It is not perfectly equalized. It's definitely a 50/25/25. I find that is OK myself, as most of my real world placements have better pro and sketchier pro, and offsetting the load is handy.
Also note that you can tie the same knot in both legs for a 25/25/25/25.
2)The double 8 is definitely not self-equalizing in the classic sense, as it's a knot in the cord, and not a carabiner or ring sliding along the cord. So, to be more precise, this knot will adjust itself a good amount while still loose, a nice advantage over clove hitches.
JimTitt wrote: Equalising the right pieces by nylon sliding on nylon, you´re joking right? Jim
Yes, it's nylon on nylon, but that's actually pretty normal use for cord/rope. We're not talking about lowering off a sling, but rather casual sliding of the knot during belay, and a small amount of slippage as it's loaded. That's not very dangerous or uncommon. Think Munter Hitch or the cinching of your harness knot during the first fall or take. That's all. No crazy friction danger here. Also, I like double 8 here only as a smaller knot. However there are people that have been climbing on full size Double 8 anchors for a while. (ie: Ultrabiker)
So what I mean to say, is that the Double 8 is a quick and versatile replacement for cloves on additional pro. It can also be adjusted at any time very easily, and less importantly, it will somewhat self-equalize while the knot is still loose. Further slippage of the knot under load for a dynamic equalization is possible, but I can't say without more research & testing. (I really need to see how the knot slips or equalizes under fall loads, that's very important to know. Right now I only believe it slips an inch or so and equalizes. But that remains to be seen for a sloppy knot and for small Vs large forces.)
I'd really love to hear from anyone that has used Ultrabiker's Fig 8 for the entire anchor rig, or who has any further experience with the knot.
JimTitt wrote: Increased loading with increasing extension is inevitable, is real and not to be ignored. Use the rope or clove hitches.
As far as small extension (4-10") and increased loading goes, that is going to need some serious looking into. My entire concept is based on small extension being OK, and Jim Ewing's testing and John Long's opinions being valid. If the equalette & limited Sliding-X is debunked as dangerous for reasons of extension, then we all need to go back to cordalettes, manual equalizing, and bomber MP knots.
However, the Double 8 needs its own testing to see if it slips a little (self-equalizing) or tightens up bomber under high fall loads. Really, I want to address this so badly, please pardon my lack of info.
JimTitt 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.
Well shucks, I feel like being a John Long believer is now a black mark upon my soul. :-/
Did they use limiter knots? Or was the extension a full meter or so?
I'd really like to see the data if you can find it. I'm still a little unsure how the FF are so high for small extensions. Is the rope under full stretch at the time and no longer helping?
Thanks again all for the input, I really want to know more about the Double 8 and how it takes falls.
I still think it's a nice improvement over cloves. (in the world of acceptable equalizing & extension)
(This post was edited by Neoshade on Aug 18, 2011, 4:51 PM)
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hugepedro
Aug 18, 2011, 5:08 PM
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JimTitt wrote: Can´t see it´s equalised anyway, looks like 50/25/25 to me. Equalising the right pieces by nylon sliding on nylon, you´re joking right? Increased loading with increasing extension is inevitable, is real and not to be ignored. Use the rope or clove hitches. Jim
Definitely not equalized, so this business about the knot equalizing is just silly, even if it were desireable to have it do so (which, as you point out, it is not).
But, I don't care about 50/25/25. Most anchors never take the force equally in real world falls anyway. I'll take bomber pieces and a good stance over dynamic equalization any day.
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JimTitt
Aug 18, 2011, 5:17 PM
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The whole equalising knot thing is madness, first you really ought to know that the friction of nylon on nylon is relatively high, 2.5 times that of nylon on metal so you are in the shit there with any thought of equalising anyway. And when one piece blows either the knot unravels, gets cut by the loaded strand sliding through (nothing like a Munter by the way) or whatever but you don´t know.
So, like others, you are publicising a system which you have sketchily though through, with no theoretical justification and no testing either, in other words you have no idea what will happen. Super, we know other people like that!
Of course there were no limiting knots, I would have written "a limited extension sliding X" if that had been the case. The extension was 60cm as this was the length of the failed leg and to get those sort of force increases dropping a belayer 60cm onto a sling is very understandable.
The article was referenced but if you really need a link to get into the biggest database of climbing safety related articles it is http://alpenverein.de/...r.php?tplpage_id=165 and you go through the archive to 2/2009 and download the pdf.
Jim
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Neoshade
Aug 18, 2011, 6:08 PM
Post #24 of 88
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So, In the interest of "dynamic equlization" (which a knot really can't claim) I thought I'd take a whack at the hornets' nest :D
Haters be hatin', so...
Yo Dawg! I heard you like Sliding-X's...
So put I a Sliding-X on yo' Sliding-X!
Now THAT'S a handy little truly-self-equalizing leg on a cordalette (or equalette in this case).
Seriously, the Double-8 is a pretty sweet and versatile knot!
Enjoy. (And bring on the hate  )
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vencido
Aug 18, 2011, 7:00 PM
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If I get hooked up with a partner that has a big hunk of accesory cord tied together with a double fisherman's and then extra fisherman stopper knots (tied 3" from the end of the main knot) I'll quickly come to the conclusion that he tends to waste time and overthink things.
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Neoshade
Aug 18, 2011, 7:14 PM
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One last point on the whole "a knot is equalizing" thing.
Why are people getting all panties-in-a-bunch about a knot slipping a little and cinching down a little? This happens during loading of every single knot ever!!
The Double 8 for a little rig on one leg only needs about 1inch of slip between the loops to equalize from a 3 foot movement in Master Point down below! This is TINY and normal for all knots as they come under load!
What I'm saying is, that when the double 8 tightens up under load - as all knots do - it actually equalizes a LOT during this 1 inch of rope movement through the knot!
Go try it out. Hang it on a wall and pull it off axis, and fall as hard you can on it. The darn thing works! And, again, I'm only offering it up here for use in only small loops on one leg on an anchor: For a situation where the tiny amount of rope taken up in a knot during loading is enough to get the equalizing you're looking for. And this knot does it.
Again, it's just an alternative to clove hitches, and I'm looking for constructive criticism and input, I'm sorry for making any claims other than "What do you think of this?"
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Neoshade
Aug 18, 2011, 7:19 PM
Post #27 of 88
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vencido wrote: If I get hooked up with a partner that has a big hunk of accesory cord tied together with a double fisherman's and then extra fisherman stopper knots (tied 3" from the end of the main knot) I'll quickly come to the conclusion that he tends to waste time and overthink things.
hahaha, That was the first cordalette I ever tied. I did it while killing time sorting my gear. Seriously, who cares?
Thanks for trolling jerk.
(This post was edited by Neoshade on Aug 18, 2011, 7:28 PM)
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JimTitt
Aug 18, 2011, 7:34 PM
Post #28 of 88
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Before you make claims about how the knot equalises under load perhaps you ought to actually test it under real loads, 6kN is generally considered the minimum one to use.
I´ve already know (and have given you) the information of how to calculate why it won´t in any way, shape or fashion begin to be remotely equalised so I don´t need to bother.
For your sliding X variant the need to slide through 3 karabiners makes it a similarly useless proposition and it would be more effective (though still not equalising) if you short-hitched into the karabiners. You can replace the funny 8 with an overhand.
If you want dynamic equalisation then friction must be eliminated.
Use the rope or clove hitch, you may love your funny 8 but I´ve never found any useful application for it in 44 years climbing, instructing, 7 years living aboard a sailing boat and 15 years in the marine industry. The same goes for the sliding X.
Jim
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Neoshade
Aug 18, 2011, 7:46 PM
Post #29 of 88
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Thanks for the link to the DAC info, BTW, but I can't read German, and unfortunately Google won't translate a PDF.
I'd love to see the research though, and figure out how to measure 6kn myself under a dynamic load. (static weights are pointless)
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JimTitt
Aug 18, 2011, 8:45 PM
Post #30 of 88
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A force is a force but that´s going to get complicated, for their tests you need the dynamics anyway.
But being a good chappie I have actually wandered over to my workshop, beer in hand (it´s 10.30 at night here) and pull-tested your knot theory.
As usual (for us anyway) we set up a 60° two-point anchor and start pulling with the centre-point offset to the side (and line of pull) and see what the loads are on each anchor point. This gives the ratio of the unevenness of the load you will get in practice with dynamic equalisation (if that´s the word to use).
I pulled at 6kN with 6mm cord.
Simple equalisation (just on a single strand, no X or whatever) - 1.53:1
3 karabiner sliding X as in your example - 3.71:1
Funny 8 - 7.25:1
So now you can put this into your diagrams and work out the loadings you get in reality when you start your equalisation from one side or the other. And then you will appreciate why 95% of the systems are worthless and the rest not much better. And why "nearly true equalisation" has to be accompanied by "using a collection of large and very expensive pulleys throughout the system".
Jim
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Neoshade
Aug 18, 2011, 8:54 PM
Post #31 of 88
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The use of a double 8 for the entire anchor can be found in disucssion here:
http://www.rockclimbing.com/...ew_flat;post=2127276
[edit] In discussing the use of a double 8 as an anchor...
USnavy wrote: This method is similar to what Beth Rodden uses and well... she climbs 5.14 trad. I took Beth's multi-pitch class in Red Rocks last month and she taught us to build the anchor using the rope and tie a double loop figure eight similar to what’s in the picture.
I'll take Beth Rodden over many other people. (and further innuendo)
(This post was edited by Neoshade on Aug 19, 2011, 2:10 PM)
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JimTitt
Aug 18, 2011, 9:26 PM
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Using an Alpine Butterfly to belay is a lot older than me, it has no relevance to what you are doing as far as I can work out.
Quoting US Navy won´t get you any bonus points or do anything for your credibility!
Jim
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rgold
Aug 18, 2011, 11:18 PM
Post #33 of 88
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If you need to get a 5.14 climbed, you probably want Beth Rodden over Jim Titt (sorry Jim, I don't even know you, just guessing...) But if you want authoritative advice about anchors, not only do you want Jim Titt over Beth Rodden, I'd guess Beth Rodden isn't on any conceivable short list.
Most climbing "knowledge" is seat-of-the-pants BS, typically justified by, "I've never heard of procedure XXX ever faiiing." There is little reason to believe that very good climbers know any more about the subject than the average climber. They are both going on a combination of folklore and tradition.
Part of the lesson of all this is that there is a wide range of procedures, many of which are very far from optimal, which are still good enough most of the time, primarily because "most of the time," circumstances do not provide a severe test.
With nylon rubbing on nylon, the SSE is even further from optimal then similar concoctions. It probably won't engender a total catastrophic anchor failure, because such things are very rare under all circumstances. But if your anchoring philosophy involves doing what you can to stack the deck in your favor, then the SSE doesn't seem like a sensible option to me.
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patto
Aug 18, 2011, 11:31 PM
Post #34 of 88
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Neoshade wrote: Also, sorry Patto for getting preachy and aggressive when I was treating John Long's work and the extension testing like gospel and just beating the bible at you.
Neoshade wrote: Well shucks, I feel like being a John Long believer is now a black mark upon my soul. :-/
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Neoshade
Aug 19, 2011, 3:17 AM
Post #35 of 88
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JimTitt wrote: Using an Alpine Butterfly to belay is a lot older than me, it has no relevance to what you are doing as far as I can work out. Quoting US Navy won´t get you any bonus points or do anything for your credibility!
Uh, Jim, you lost me. Is the thread and discussion I referenced talking about an Alpine butterfly? I don't think it is. The discussion I linked to and quoted USnavy from is about the Double Figure 8 or "bunny ears" knot that I've used here in the rig.
Alpine Butterfly is a rather elegant knot too though.
And BTW thanks for the testing. 
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Neoshade
Aug 19, 2011, 3:07 PM
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Wow Jim,
I just took a look at your credentials and other forum posts.
I tip my hat to you sir! I was not not aware that was arguing with a professional! :)
So you're telling me that a carabiner Sliding-X like I used in my second set of photos (right, 3 carabiners in total, counting the pro) doesn't equalize at ALL when the Centre-Point / Master-Point is pulled to one side before loading??
Wow. OK.
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acorneau
Aug 19, 2011, 3:34 PM
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This whole mess reminds me of something some students came up with for anchoring a double-line rappel...
(This post was edited by acorneau on Aug 19, 2011, 3:35 PM)
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Triple Double8.jpg
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Neoshade
Aug 19, 2011, 4:08 PM
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Ha!
OK, that's a little ridiculous!
This setup is an obvious FAIL with it's terrible angles, but it looks like it's quick to tie, super easy to adjust, and otherwise bomber.
(Except for one other thing - I don't much like the double 8 in primary anchor rigging, for lack of redundancy in the strands, especially if they can slip at all under load.)
Anyone else?
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JimTitt
Aug 19, 2011, 4:56 PM
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rgold wrote: If you need to get a 5.14 climbed, you probably want Beth Rodden over Jim Titt (sorry Jim, I don't even know you, just guessing...) But if you want authoritative advice about anchors, not only do you want Jim Titt over Beth Rodden, I'd guess Beth Rodden isn't on any conceivable short list.
Ha! If you want a 5.14 bolted then I´m your man, climbing-wise I´m a few digits short somewhere. Though if I can have the age-related allowance at one number grade per decade I´m on!
(I´m really a 58 yr old onsight 5.11d´ish bumbler who should be 10kg lighter and I´ve been like that for 40 years now so no prospect of sudden improvement).
I´m on holiday for 3 weeks in the world centre of trad climbing (the UK) where cordalettes and their relatives are looked upon as madness and only for beginners so I´ll try to bash out an article on anchoring and the physics.
Jim
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JimTitt
Aug 19, 2011, 5:44 PM
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Well I´m a professional when it comes to making some types of climbing gear (at least the tax man says so) and I know a lot about frictional dynamics in climbing gear, whether there is any money in anchoring systems is debatable!
The killer all the way through the whole equalisation thing is the resistance over the karabiner or ring, 1.6 is the magic number (roughly) and is the factor (usually called the karabiner factor) you always end up using when you look at the approximate forces on one side against the other. And until this is eliminated you cant get equalisation, add another turning point and you add another lot of "unequalisation".
Your sliding X has three turning points and a quick test gave a karabiner factor of 3.71:1 (for the relatively thin 6mm cord and 12mm diameter karabiners a single bend gave 1.53:1 and if you multiply 1.53 X 1.53 X 1.53 you get 3.58 so obviously it was near enough).
So when you load the centre point slightly off to one side with say 5kN one of the anchors gets 3.94kN and the other gets 1.06kN, whether you call that equalised is a matter of opinion! And don´t even look at an Alpine Equaliser!!!
Your Funny 8 was a dead man walking because I knew beforehand that the resistance of nylon on nylon is far higher than over metal so it would be horrific, with our 5kn load you will get 0.6 on one side and 4,4 on the other, basically you could just tie to one piece and chuck the other one down the cliff.
I shall try to find time to write an article and show how to simply calculate all this but then what will happen to the endless creativity we see?
Jim
Jim
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hugepedro
Aug 19, 2011, 6:26 PM
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Neoshade wrote: Ha! OK, that's a little ridiculous! This setup is an obvious FAIL with it's terrible angles, but it looks like it's quick to tie, super easy to adjust, and otherwise bomber. (Except for one other thing - I don't much like the double 8 in primary anchor rigging, for lack of redundancy in the strands, especially if they can slip at all under load.) Anyone else?
Think you got that backward. There is nothing wrong with the angles, and it's ridiculous overkill so "quick to tie" would not be one of its features.
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JimTitt
Aug 19, 2011, 7:45 PM
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It´s a sort of chicken and egg thing really. In all my climbing career I can only really remember one fatality from a failed belay in the sense we are discussing because typically cragging one has more time and spends more effort on getting a worthwhile belay. And anyone who is playing for months in his bedroom working out these systems is going to be so anal about his gear placements that nothing will ever fail anyway.
On the other hand a friend of mine has had 8 belay failure fatalities in one year in his local area because it is mountaineering where clip the peg and go is normal, replacing the rotting pegs with bolts cured that but that is another whole ball game.
So one set of climbers will probably be safer than another, even though the system itself isn´t but there we are.
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Neoshade
Aug 19, 2011, 9:38 PM
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+1 drecter & Jim.
Thanks again for the friction info Jim, I think it'd be helpful for a lot of us "bedroom anchor geeks" to have some hard info to work with. My claims were based on nothing more than familiarity with the knot in general, and yanking as hard as I could on it. Nothing above a 1 Kn.
So I guess I can only offer the double 8 for use as an alternative to cloves, (not for any "self equalizing" abilities) being faster to tie and adjust for myself, but probably not for others.
FYI - I get into this stuff out of curiosity and study. When I'm at the crag I still use the classic simple methods I was taught
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patto
Aug 19, 2011, 10:08 PM
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The thing is that cordalettes can do a pretty good job of equalising everything.
If its just two pieces horizontally in line with each other then predicting the fall line and trigonometry will ensure 'even enough' loading.
Three pieces are much harder to equalise. But personally I have no issues with 50:25:25. This obsession with perfect equalisation was created by JLong.
The thing is that I currently don't even own a cordalette. I build my anchors out of climbing rope. Its just as fast, more flexible, stronger and dynamic. I create a statically equalised anchor and its totally bomber.
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vencido
Aug 19, 2011, 10:19 PM
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patto wrote: I build my anchors out of climbing rope. Its just as fast, more flexible, stronger and dynamic. I create a statically equalised anchor and its totally bomber.
90% of anchors I make I just use the rope.
But occasionally I know from the parking lot that I'll be leading every pitch, or that I'll need to lead the second half of the route.
On these occasions I bring two cordolettes with me.
Do the never ever cordolette people just use slings if they will be leading everything?
Or do you swap ends or something else I'm not naming?
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patto
Aug 20, 2011, 7:53 AM
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vencido wrote: Do the never ever cordolette people just use slings if they will be leading everything? Or do you swap ends or something else I'm not naming?
I currently don't own a cordalette so I have no choice but to use the rope. I currently have no plans to buy another cordalette. (Slings rarely suffice for the trad anchors where I climb.)
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rgold
Aug 20, 2011, 2:52 PM
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I never swap ends. I'll carry cordelettes for long multipitch routes and for inexperienced seconds, but what I do at each stance is governed by the complexity of the anchor. With simple anchors and on shorter routes where an extra minute is far from critical, I'll usually just rebuild the anchor for the second.
Since I use half ropes for everything, anchor-building is simplified considerably and rebuilding really takes very little time. One reason it is simple and fast to rebuild a double-rope tie-in is the absence of the almighty but rarely essential power point. Independent connections to parts of the anchor can be undone while still leaving the party tied in. (The most obvious example of this is the two-piece anchor with one rope tied to each piece.)
Another thing that helps with changeovers is having an installed tether on the harness. I clip mine to the best single piece (but loosely enough so that if the anchor is loaded it will be the ropes that take the load). Being clipped this way means that anything can be undone and changed and I'll still be tied in. It also means, in the ordinary case of shared leads, that as soon as the leader is off belay I can start taking apart the anchor and so will usually be very close to ready to climb (just the final piece to clean) as soon as they are on belay.
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mbrd
Aug 21, 2011, 4:35 AM
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coming in late here, so sorry if i am asking stupid questions, but are you saying you initially clip the most solid piece and the rope when you arrive at the belay? good plan...
and regarding the issue of cleaning up the belay as the lead has swung, you're just talking about scrapping what isn't gonna help henceforth in a fall, right? i mean you're not bagging the whole station, are you?
i guess i know that how much prelim cleansing of the station one can do depends a lot on the upcoming pitch, but i am wondering if there are more efficient transitions i could be considering.
the embarrassing thing is that all this brainwork is happening on my couch- and my part is not even really good brainwork. it's also a sort of mediocre couch...
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rgold
Aug 21, 2011, 4:54 AM
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mbrd wrote: ...are you saying you initially clip the most solid piece and the rope when you arrive at the belay?
Yes. But the rope is eventually set up to take any belay load. If I am trying for speed/efficiency and am climbing with experienced partners, I'll say "off belay" as soon as I'm tethered in to the first (good) piece, so that the second can take me off belay and start getting ready to climb while I'm setting up the rest of the belay anchor.
mbrd wrote: ...and regarding the issue of cleaning up the belay as the lead has swung, you're just talking about scrapping what isn't gonna help henceforth in a fall, right? i mean you're not bagging the whole station, are you?
I'm not sure we understand each other here. When the tethered-in leader calls "off belay" and continues to set up the belay anchor, the second takes the leader off, puts on or tightens up their shoes, puts on the pack if there is one, and dismantles every part of the anchor except the single piece they are tethered to. When the leader takes up the rope and calls "on belay," the second un-tethers and removes the final piece and is ready to climb.
I should emphasize that the procedure is for experienced parties on long routes who consider time savings to be worth a small extra risk. There is a period when both leader and second are both tethered to a single piece with neither belaying. There is no reason to be doing this on short multipitch climbs.
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Neoshade
Aug 21, 2011, 7:27 AM
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I see what rgold is saying as classic SOP (standard operating procedure)
As the leader, you say "Off Belay" once you're safe, and clipped into a personal anchor (The rope coming off your harness or a sling/PAS/daisy). Then your second begins dismantling the anchor below and prepares to climb. The second only removes the last 1 or 2 pieces (how little or much he leaves depending on the security of the anchor and his hanging/standing position to it), as the last act before climbing up with the shout from above of "On Belay!"
The idea is, when you're at a belay station, and ready to work the rigging, only 1 or 2 pieces of pro are needed to call it "safe" and switch out the belay. You're not going anywhere, and building or dismantling the rigging has to take place somehow. and overlapping the belays (building a rig on belay, or dismantling most of a rig on belay) is considered overkill by most experienced climbers.
However, (because it can't be emphasized enough) Never take even the shortest fall on a nylon or dyneema personal anchor sling. If you clip in with a personal anchor, and not the rope, cinch it tight to your belay, sit your a$$ down and don't climb even a foot above it. This is the exception to the rule that will get you killed. And violating this simple rule is really the only case for overlapping the belay as long as you and your second understand your anchors/pro.
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patto
Aug 21, 2011, 10:34 AM
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Yep. All that is part of efficient multipitch climbing.
Getting your anchor set up should take only a few minutes. You should call Safe/OffBelay as soon as you feel appropriately secure. One bomber piece and I'll do that, two if I'm feeling paranoid.
As a second you should putting shoes and and dismantling the anchor. and be ready to go as soon as you hear the signal.
Interchanges are what make efficient multipitch climbing. I aim for a speed of 30mins per 50meters. But it all depends on the difficulty of the terrain.
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mbrd
Aug 21, 2011, 4:06 PM
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sorry if i was unclear- turns out you've been clear enough for both of us.
we're on the same page here.
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jktinst
Sep 2, 2011, 6:16 PM
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Jim, please, do write that article.
In the swing resulting from an off-centre loading, some of the equalization systems make the tape or cord run through several of the biners or rings involved (Alpine equalizer, ACR, upper right part of Neoshade's latter system, etc.) whereas for others, it runs only through the central biner (eg the two-arm equalette with extension-limiting knots). I can feel that the former have more friction than the latter. On the other hand, in an off-centre loading situation, the pro closest to the direction of pull is initially going to get a greater portion of the load. So, without a more detailed description of the test, I keep wondering if the large difference you are reporting is really due solely to biner friction or if it might be due to a combination of friction and skewed loading.
Although this discussion has put a big question mark for me over the equalizing set-ups that involve friction over multiple biners, for now, I remain convinced that, even with less-than-perfect distribution of the load and the need to pick a compromise between the range of equalization and the limitation of extension, low-friction equalizing belays are still preferable to the alternatives that don't equalize at all under an off-centre load. Intuitively, I do buy into the belief that some equalization of multiple pros is better than loading each one sequencially.
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patto
Sep 2, 2011, 9:54 PM
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jktinst wrote: Intuitively, I do buy into the belief that some equalization of multiple pros is better than loading each one sequencially.
A well configured statically equalised anchor will roughly equalise the load over the pieces. If dynamic rope is used it will equalise even more so.
In the vast majority of cases the load is only going to be in two possible directions the closest piece or directly down. So unless the closest pieces is at a significantly different angle from the down direction then you don't have a problem.
If its factor twos that you are designing for then you ALREADY know the direction.
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JimTitt
Sep 5, 2011, 10:44 AM
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jktinst wrote: Jim, please, do write that article. In the swing resulting from an off-centre loading, some of the equalization systems make the tape or cord run through several of the biners or rings involved (Alpine equalizer, ACR, upper right part of Neoshade's latter system, etc.) whereas for others, it runs only through the central biner (eg the two-arm equalette with extension-limiting knots). I can feel that the former have more friction than the latter. On the other hand, in an off-centre loading situation, the pro closest to the direction of pull is initially going to get a greater portion of the load. So, without a more detailed description of the test, I keep wondering if the large difference you are reporting is really due solely to biner friction or if it might be due to a combination of friction and skewed loading. Although this discussion has put a big question mark for me over the equalizing set-ups that involve friction over multiple biners, for now, I remain convinced that, even with less-than-perfect distribution of the load and the need to pick a compromise between the range of equalization and the limitation of extension, low-friction equalizing belays are still preferable to the alternatives that don't equalize at all under an off-centre load. Intuitively, I do buy into the belief that some equalization of multiple pros is better than loading each one sequencially.
The angles aren´t relevant, in practice you don´t have the option to change them anyway and the effect is what matters not the cause.
However since I´m working on the cause as well I did the easy thing to check and eliminated the angles altogether by arranging the points vertically above each other. You get the same results except that the narrower the angle between the pieces makes the sensitivity of the load direction more and more sensitive until the vertical case where the difference between the high and low on the pieces is physically impossible to detect and it is going to be impossible to manually equalise as well.
The big question is are there alternatives which give better results than equalising systems which often give results worse than just guessing. As the DAV decided the benefits of minimising extension are clear whereas the benefits of dynamic equalisation are effectively non-existent so redundancy is the choice giving clear benefits.
Jim
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patto
Sep 5, 2011, 11:09 AM
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JimTitt wrote: jktinst wrote: Jim, please, do write that article. In the swing resulting from an off-centre loading, some of the equalization systems make the tape or cord run through several of the biners or rings involved (Alpine equalizer, ACR, upper right part of Neoshade's latter system, etc.) whereas for others, it runs only through the central biner (eg the two-arm equalette with extension-limiting knots). I can feel that the former have more friction than the latter. On the other hand, in an off-centre loading situation, the pro closest to the direction of pull is initially going to get a greater portion of the load. So, without a more detailed description of the test, I keep wondering if the large difference you are reporting is really due solely to biner friction or if it might be due to a combination of friction and skewed loading. Although this discussion has put a big question mark for me over the equalizing set-ups that involve friction over multiple biners, for now, I remain convinced that, even with less-than-perfect distribution of the load and the need to pick a compromise between the range of equalization and the limitation of extension, low-friction equalizing belays are still preferable to the alternatives that don't equalize at all under an off-centre load. Intuitively, I do buy into the belief that some equalization of multiple pros is better than loading each one sequencially. The angles aren´t relevant, in practice you don´t have the option to change them anyway and the effect is what matters not the cause. However since I´m working on the cause as well I did the easy thing to check and eliminated the angles altogether by arranging the points vertically above each other. You get the same results except that the narrower the angle between the pieces makes the sensitivity of the load direction more and more sensitive until the vertical case where the difference between the high and low on the pieces is physically impossible to detect and it is going to be impossible to manually equalise as well. The big question is are there alternatives which give better results than equalising systems which often give results worse than just guessing. As the DAV decided the benefits of minimising extension are clear whereas the benefits of dynamic equalisation are effectively non-existent so redundancy is the choice giving clear benefits. Jim
I like your work. That is what I have been arguing for 4 years on this site. But the sliding-x never seems to die around here.
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livinonasandbar
Sep 5, 2011, 3:09 PM
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potreroed wrote: I've been climbing for 45 years and have never used a 'lette of any type. Why complicate things? I'm with patto on this one. Use the rope and the PAS which you'll have already girth-hitched on your harness if you're smart.
Ed, if you're not swapping leads, what do you do? Just untie and swap rope ends?
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JimTitt
Sep 5, 2011, 4:12 PM
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Since time immemorial or even before I and Ed started climbing it was standard practice that the first climber clips into a karabiner using a fig.8 to form a loop. The other climber does the same, slipping the loop up from underneath through the first climbers loop and clipping on.
Removal for the first climber to continue leading is then easy.
Jim
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JimTitt
Sep 5, 2011, 4:21 PM
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My pleasure Sir.
I´ve just been trying some tests with average punters to see how well they achieve equalisation and one of the most popular `equalising´methods got a load distribution of 85%, 15% and 0% and with no apparent way of pre-determining which was going to be which.
We were impressed!
Jim
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potreroed
Sep 6, 2011, 4:51 AM
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livinonasandbar wrote: potreroed wrote: I've been climbing for 45 years and have never used a 'lette of any type. Why complicate things? I'm with patto on this one. Use the rope and the PAS which you'll have already girth-hitched on your harness if you're smart. Ed, if you're not swapping leads, what do you do? Just untie and swap rope ends?
I have done that a few times but not very often. I almost always belay off my harness facing the wall with a re-direct and stack the rope by butterflying it across the rope in front of me. When my partner is secure it's a simple matter of flipping the whole stack over onto him/her so it feeds out properly.
(This post was edited by potreroed on Sep 6, 2011, 5:39 AM)
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qwert
Sep 6, 2011, 1:19 PM
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JimTitt wrote: My pleasure Sir. I´ve just been trying some tests with average punters to see how well they achieve equalisation and one of the most popular `equalising´methods got a load distribution of 85%, 15% and 0% and with no apparent way of pre-determining which was going to be which. We were impressed! Jim
Which popular method was it, how did you set up the test, etc.
Was this just you playing around, or will this eventually lead to a bigger report, and hence you cant publicise your intermediary results?
qwert
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JimTitt
Sep 7, 2011, 8:19 PM
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I´m writing a bigger article but I´ve been touring around in a tent with my family for the last 3 weeks so not a lot of internet or writing time. Got back home a couple of hours ago so I´ll press on a bit!
Jim
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cracklover
Sep 7, 2011, 10:18 PM
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JimTitt wrote: I´m writing a bigger article but I´ve been touring around in a tent with my family for the last 3 weeks so not a lot of internet or writing time. Got back home a couple of hours ago so I´ll press on a bit! Jim
Any chance you could toss a Mooselette in the mix if you're testing anchor methods? Just like the Dos Equis Man - I don't always use a cordelette, but when I do, it's always in Mooselette form.
Been using it for about 5 years, and am happy with it. But it sure would be nice to get real numbers.
Here's a link: http://www.rockclimbing.com/...rum.cgi?post=2512061 (3 posts down on that page)
BTW, it seems much happier if you use a big pear or HMS style biner on the powerpoint - wide side up. A small biner will pinch the strands together and make the friction bad.
GO
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jktinst
Sep 10, 2011, 10:27 PM
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JimTitt wrote: The angles aren´t relevant, in practice you don´t have the option to change them anyway and the effect is what matters not the cause. However since I´m working on the cause as well I did the easy thing to check and eliminated the angles altogether by arranging the points vertically above each other. You get the same results except that the narrower the angle between the pieces makes the sensitivity of the load direction more and more sensitive until the vertical case where the difference between the high and low on the pieces is physically impossible to detect and it is going to be impossible to manually equalise as well. The big question is are there alternatives which give better results than equalising systems which often give results worse than just guessing. As the DAV decided the benefits of minimising extension are clear whereas the benefits of dynamic equalisation are effectively non-existent so redundancy is the choice giving clear benefits. Jim
I’m afraid that I didn’t understand any part of Jim's response in relation to my questions but I don't want to bug him for more explanations if a more complete article is coming.
This thread has sent me back to pore over the Ewing tests reported in the Long&Gaines book, converting the results to units that could be compared with this thread. Having done this, I thought that it might be helpful to this discussion to provide a synopsis. Apologies to those who are already familiar with the tests and sorry once again for a long post.
In the tests, a 100kg weight was dropped for 0.5 m and stopped by a 0.5 m length of dynamic rope attached to the central biner of a two-arm system (FF1). Each attachment point measured the portion of the load that it was subjected to. The rigs tested mimicked 2 placements in a horizontal crack (arms of equal length at 24 deg) or in a vertical crack (arms of unequal lengths at 0 deg). The tests compared the cordelette and the sliding X. The equalette was introduced later in the "unequal" configuration only. Many experimental protocol details were left out of the report (although nothing critical as far a I can tell) and a few points are a bit unclear; eg how come that, using slings of the same length, the "equal" tests ended up with the same arm lengths for both riggings (70 cm), whereas for the "unequal" tests, the arms of the cordelette rig were significantly shorter (55 & 12 cm) than those of the sliding X and equalette (100 & 45 cm for both). I'll also skip the comparisons of different cord and tape materials (nylon, high tensile) that don't seem essential for this discussion.
The results reported were the differences in load "felt" by each arm. What would have been useful for this discussion is the average dynamic load (sum of each arm's load) resulting from the drops. The closest the book comes to giving this is "about 1500 to 2000 lbs". I translated this as 8 kN +/- 1 kN and used 8 for the calculations of equalization ratios.
- Cordelette equal: mean difference of about 0.9 kN for an equalization ratio of about 1:1.25.
- Sliding X equal: about 0.25 kN for a ratio of 1:1.06.
- Cordelette unequal: about 3.3 kN for a ratio of 1:2.40 with high "regular" variability.
- Sliding X unequal: 1 kN for a ratio of 1:1.29 with generally consistent results but with occasional tests yielding a much greater difference ("outlyers"). These were considered to be caused by the "clutch effect" (resulting from one strand crossing over the other on the underside of the central biner's basket bar and occasionally effectively squeezing/braking it against the bar, limiting equalization).
- Sliding X unequal with the clutch effect manually eliminated (not an option while climbing): 0.5 kN (1:1.13).
- Equalette unequal: 0.5 kN (1:1.13).
The very poor equalization performance of the cordelette unequal was attributed to the fact that the shorter arm stretched a lot less than the longer one (even using static cord), causing it to bear a much greater portion of the load. I am not sure that using dynamic rope instead of static materials (as suggested by patto) would have made any difference: the longer arm would still have stretched more than the short. Given this explanation, it would have been useful for the tests to use the same arm lengths in both systems. If they had, the cordelette might not have looked quite as bad but there is no doubt that the sliding X would still have equalized significantly better. This also means that in drop tests with the equalette and the sliding X, some of the material from the long arm ran through the biner to compensate for the lesser stretch on the short side. The interesting thing in the context of this discussion is that it did so much more efficiently than the 1:1.5 ratio suggested by Jim for a single biner's friction.
Of course, this "stretch" explanation does not necessarily work to explain the poorer performance of the cordelette equal. It seems quite improbable that the difference reported could be ascribed to the very small differences in arm lengths resulting from the difficulties in making the two arms exactly the same length with the cordelette. A more likely reason is the difficulty in releasing the weight from a position exactly in line with the central biner. Most of the drops were probably inevitably very slightly off-center, resulting in somewhat uneven loading of the two attachment points. Of course, similar practical experimental constraints would have been encountered with the sliding X but, as the unequal tests suggest, this rig's dynamic equalization capabilities must have taken care of these small variations.
An analysis of equalization tests using 3-arm systems and off-centre drops, describing the experimental protocols clearly in addition to providing the results, would complement and expand on the Ewing tests very nicely and would be very gratefully received. By experimental protocols, I mean not just the rig configurations but also the steps involved in setting them up, whether, for example, the rigs were redone from scratch for each drop test or if several drops were performed after a single setup, etc. It may sound like too much information but these details could turn out to be essential for a proper interpretation of the results.
Despite my introductory sentence, I must say that I'm quite impatient to find out more about how the "85-15-0" test was performed and on what rig. I have a very hard time imagining a rig generally considered to be equalizing and a test protocol that would repeatedly yield "0" load on one of the 3 arms with no apparent way of pre-determining which. All I can think of would be a highly friction-challenged rig tested with an off-centre drop without having pre-stretched the 3 arms first (ie having left the arms randomly and unevenly slack after rigging it) but even then...
I am particularly interested in off-centre drop tests because not only do they probe the limits and efficiency of equalization of a particular rig but they are also much more representative of a real fall. Of course a fallen leader will always end up exactly at the vertical of the central biner with a cordelette or any other system that uses a central biner but it's where he starts from that matters and very rarely will he start falling exactly above the central point.
Eagerly awaiting complementary information.
(This post was edited by jktinst on Sep 11, 2011, 12:40 AM)
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JimTitt
Sep 11, 2011, 8:23 AM
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Well I didn´t really understand your question!
If you test two points vertically above each other you (I got) get a load split of 61%/39% unless you are unbelievably skilfull. This isn´t substantially different from a 60° included angle between the points (64%/36%) or a 90° angle (61%/39% as well) so one can safely ignore the angles except the total load is being increased.
One has to differentiate between static and dynamic equalisation. When you set up a sliding X or whatever it is initially in the static mode where the climber decided where the centre karabiner was going to be. As the load direction is moved offcentre the equalisation stays static until the karabiner slips when we move into dynamic equalisation. For pretty well all the systems I´ve tested the load angle has to be about 13° before the dynamic condition is reached, until then you can just tie a knot in the middle and clip into that and one is not testing the dynamic equalising properties at all.
From your description it looks like the tests were not testing the dynamic equalisation but rather the equalising skills of the tester. The DAV drop test on a sliding X was offset but probably not enough and they got a ratio of 1.3:1.
How good we are at equalising is something else I´ve been checking. From what I´ve seen so far a 2 horizontal point system we can get fairly good, an unequal legged system is poor and a vertical sytem very poor. The 3 piece ones are more difficult!
Your last paragraph touches on one of the problems with restricting testing to one particular case, while most of the time the load may assumed to end up directly below the belay karabiner in other scenarios such as rescue, on traverses or where the rope snags the load may be angled from the vertica- or where the belay builder expectedl. So we are better off testing for the equalising properties of the system rather than how well the system equalised under any particular condition if you see what I mean!
Jim
(This post was edited by JimTitt on Sep 11, 2011, 4:51 PM)
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patto
Sep 12, 2011, 10:29 AM
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The irony in all this effort put into micromanagement of anchor design is that multipiece anchors almost always receive significantly lower loads than single piece protection running belays.
The question needs to arise what scenario are you rigging the system for.
*high fall factors
*unexpected load directions
*one piece failing
There is no such thing as a worst case scenario of all aspects. For example you can't have a factor two fall from an unexpected direction.
As far as I am concerned my primary concern is about redundancy and limited/no extension in case of the rare event of piece failure. Additionally preventing a factor 2 fall is VERY important. Clipping the anchor and belaying lower than the anchor will achieve this.
As far as I am concerned two solid pieces is fine for many of my anchors. Tie them back to the belay and get on with the job.
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jktinst
Sep 16, 2011, 3:00 AM
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The question in my first message was based on my belief that off-centre drop tests inherently yield uneven loading no matter how good the equalization. When your earlier post mentioned that you got very uneven loading from 3-arm systems that are often considered to be equalizing and that the main reason for this was cord or tape friction over biners or rings, I felt that I had to ask whether some of the "unevenness" of the loading might not also be simply due to the "off-centredness" of the test. The fact that you did not understand the question made me wonder if in fact off-centre drop tests really do inherently yield uneven loading as I first thought.
A quick survey of climbing buddies with science and engineering training yielded a not-quite-convincing 2 in favor of "off-centre drop tests will inherently, albeit very temporarily, put a greater load on the anchor that is closest to the direction of the fall" and 1 in favor of "efficient 2-arm equalizing systems equalize the load no matter how off-center the drop" (disregarding friction at this point).
Maybe you (and other engineering-minded contributors) would care to shed some light on my dilemma.
With regards to your latest reply, I understand now that, with an experimental protocol yielding a given distribution split among two unequal arms, the split remains essentially the same regardless of the angle between the arms. Only the overall load increases with the angle. My question was not about this but thank you for the clarification.
For the DAV offset drop test on a sliding X yielding a 1:1.3 equalization ratio that you mentioned, was the offset less than the 13° you consider to be the cut-off for visible biner movement? Was it done on unequal vertical arms? It's interesting that it yielded a result that is essentially identical to the Ewing/Long/Gaines tests on the unequal but centered sliding X. Your 40:60 split means a ratio of 1:1.5 but, without the experimental protocols, comparing your, the DAV and the Ewing/Long/Gaines tests together makes no sense at all.
I was initially frustrated with the Ewing/Long/Gaines tests because I felt that a drop from the exact mid-point of a 2-arm system was unrealistic. However, their results with the unequal systems clearly showed efficient dynamic equalization despite the centered drop. Of course it is not the same as an off-centre drop test but, in both cases, equalization means that the cordage must slide through the biner. This is why I have a hard time with your assertion that, since the biner is not seen to move unless the drop is off-centre by more than 13°, you’re effectively in a static equalization situation and you might as well put a knot in the sling. It seems to me that the Ewing/Long/Gaines tests clearly demonstrated that you don’t need obvious biner movement to have dynamic equalization but that putting a knot in the sling quite effectively turns dynamic equalization into static non-equalization.
(This post was edited by jktinst on Sep 16, 2011, 3:01 AM)
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JimTitt
Sep 16, 2011, 7:03 AM
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If the system is truly frictionless then an off-centre drop will load the pieces equally since by definition there is no opposing force on the centre point, the load difference must be infinitely small since the moment one force is greater than the other the central point will move and make them equal.
Since however there is friction the pieces will be unequally loaded and as the friction remains then the unequal loading remains as well.
You´ve misread what I wrote, the difference in the DAV test was 1.3:1 which is considerably different to the tests you quoted.
If the centre point karabiner doesn´t move for whatever reason there can be no dynamic equalisation only the original static equalisation. It doeasn´t matter why the karabiner doesn´t move, it can´t tell the difference between a knot and friction and simply remains in the same place.
What you have to remember is that as the load moves off-centre the proportion taken by each leg merely changes until either the karabiner moves or if it is knotted the load on one leg becomes zero.
For an 60° included angle system and a single cord the load proportion changes like this as you offset the load (these are test results so a bit erratic, I´ll work out the theoretical ones sometime):-
0° 50%/50% 1:1
2,5° 48%/52% 1.08:1
5° 44%/56% 1.27:1
7,5° 42%/58% 1.38:1
10° 38%/62% 1.63:1
12,5° 37%/63% 1.7:1
13° Slip
15° 36%/64% 1.78:1
After the slip point the split remains the same in a sliding system but with a fixed karabiner the split continues to increase until 30° when the load on one leg is zero. Obviously the split and the point at which it becomes 0 on one leg varies with the included angle of the pieces with narrower angles naturally being worse. With the pieces vertical it´s not only virtually impossible to equalise by hand but the slightest angular change completely unloads the upper piece immediately whereas a wider angle is much less sensitive for both initial equalising and angular movement, shame it loads the gear more though!
As you can see a degree or two error in the initial equalisation would make a considerable difference (easy for me as I just watch two readouts but still a fiddle, with the knotted set-ups its a real nightmare).
While the offset drop tests are representing one particular scenario which might occur (though selected on no particular basis as far as one can tell) they certainly aren´t testing the dynamic equalisation of the system, one needs to move the load angle a lot more than they did.
If the offset the DAV and the others used is considered the real life maximum then clearly one save the effort of trying to get dynamic equalisation, however since scenarios could (do) exist which can give far greater offset then either one has to improve the equalisation or avoid them or do something different again.
Jim
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LostinMaine
Sep 16, 2011, 10:44 AM
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I'll start off by saying that I am no engineer and that I haven't picked up the Long and Gains anchors book in a while. If I recall, they had a series of box and whisker plots describing a fair amount of variability in some of their tests.
In my world of statistics, it is often the variability, rather than the mean or theoretical "true" value, that is of interest. On the tests that some of you have run, do you also find wide variability in the drop tests with off-center loading? I suspect the loading variability among successive drop tests would be much higher with "equalizing" configurations like the sliding X rather than the fixed powerpoint of something like a cordelette.
If that is the case, I am much more concerned about potential spikes in unequal loading distribution rather than mean values of how anchors handle force distribution the bulk of the time. For example, if the sliding X would somewhat equalize much of the time, but bind unexpectedly on occasion (occasions which may not have been predictable or preventable beforehand), those occasional spikes would be enough for me to choose a static anchor instead.
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cracklover
Sep 16, 2011, 3:09 PM
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LostinMaine wrote: I haven't picked up the Long and Gains anchors book in a while.
Um... go do that. It does not say what you think it says.
In reply to: I suspect the loading variability among successive drop tests would be much higher with "equalizing" configurations like the sliding X rather than the fixed powerpoint of something like a cordelette.
Nope. Look at the chart in the back, and the data series labeled cordelette unequal arms.
GO
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LostinMaine
Sep 17, 2011, 12:58 AM
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cracklover wrote: LostinMaine wrote: I haven't picked up the Long and Gains anchors book in a while. Um... go do that. It does not say what you think it says.
Just reread, and it says exactly what I thought it said. To restate it differently, I'm not so much concerned with the load distribution, rather the unpredictable variation that cannot be accounted for in an anchor setup.
cracklover wrote: In reply to: I suspect the loading variability among successive drop tests would be much higher with "equalizing" configurations like the sliding X rather than the fixed powerpoint of something like a cordelette. Nope. Look at the chart in the back, and the data series labeled cordelette unequal arms. GO
Looking on page 187, under the heading "sliding X unequal length" second paragraph is the statement "In terms of consistency in equalization from test to test, the sliding X unequal length configuration was as consistent in the absolute differences in load generated across repeated falls. Interestingly, though, while it tended to be very consistent across repeated measures, this anchor was also the most likely of all configurations to produce an occasional extreme difference in load. In other words, although tests showed this configuration to be generally consistent, it generated some unpredictably dreadful equalization." This was attributed to what they referred to as the clutch effect and was manually removed in successive tests.
However, the box and whisker plot on page 189 shows that the cordelette unequal had the greatest loading difference between legs and the greatest variability as well. This data set does not even remotely back up the words in the text. "Extreme" difference in load is not at all indicated in the box plot for the sliding X. I wonder if they chose to only report data for the sliding X where Jim Ewing manually separated the strands.
I was simply curious if others had noted this variability in similar tests conducted.
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jktinst
Sep 17, 2011, 3:34 AM
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I did note that and used the term"outlyers" in my synopsis to identify the issue even though I wasn't prepared to make my post much longer by discussing it. The narrow error whiskers on the sliding X unequal suggest that these outlyers were not included in the stats, only discussed in the text. However, those stats must be those of regular sliding X tests because, for the sliding X with clutch effect manually eliminated, the average result is lower (as low as the equalette).
Of course, not having the raw data, it's hard to gauge what an "occasionally extremely high" sliding X unequal result might be compared to the "regularly low" ones and compared to the high and "generally highly variable" cordelette unequal results.
Interesting that you should say that this question mark over the sliding X results might send you running back to a static equalization option when the equalette was clearly shown to have superior equalization with no outlyers.
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patto
Sep 17, 2011, 4:36 AM
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OK. We all know the desired solution that people seem to be trying to solve. PERFECT EQUALISATION ALL THE TIME.
However, do we even know what is the problem that is being attempted to be solved?
As far as I am concerned when I am climbing I don't normally face problems that need perfect equalisation or even 'good' equalisation.
It seems to me we are after an unachievable solution to a problem that doesn't even exist.
(This post was edited by patto on Sep 17, 2011, 4:37 AM)
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LostinMaine
Sep 17, 2011, 1:31 PM
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jktinst wrote: I did note that and used the term"outlyers" in my synopsis to identify the issue even though I wasn't prepared to make my post much longer by discussing it. The narrow error whiskers on the sliding X unequal suggest that these outlyers were not included in the stats, only discussed in the text. However, those stats must be those of regular sliding X tests because, for the sliding X with clutch effect manually eliminated, the average result is lower (as low as the equalette). Of course, not having the raw data, it's hard to gauge what an "occasionally extremely high" sliding X unequal result might be compared to the "regularly low" ones and compared to the high and "generally highly variable" cordelette unequal results. Interesting that you should say that this question mark over the sliding X results might send you running back to a static equalization option when the equalette was clearly shown to have superior equalization with no outlyers.
The reason is that I don't care much at all about equalization - especially when it is so variable as to be unpredictable. I would much prefer to identify the strongest pieces in the anchor and force the load onto those, thereby reducing the likelihood that an unpredictable, extremely high load shifted onto a supposedly equalized anchor component that was suspect from the start.
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JimTitt
Sep 17, 2011, 5:53 PM
Post #76 of 88
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In the dynamic equalising tests we don´t get much variation, only a few percent here or there which is normal with textile testing. The clutch effect isn´t occuring because at the moment I´m only concentrating on using cord for various reasons and anyway can be eliminated using 2 karabiners instead.
For the manual equalising some set-ups are more prone to wild outliers than others, the unequal leg and non-horizontal ones being particularly bad. Remove the visual clues (blindfold) or distort them (by specifying the direction of pull at an angle for example) and things get really bad.
I´ve pondered what to do with the outliers, on one hand safety chain theory says they are worst case and so must be the rule but on the other hand one has to accept that it is a queastion of the belay might get this huge load and one of the pieces might fail (or be likely to do so). As set-up that gives rare outliers and not too excessive could reasonably be accepted since the chance of all three combining is going to be very low. systems which consistently give wildly varying results are probably not so desirable. What I´ve done is take the bunched consistent results and given them as an average of what you´d normally expect to achieve and given the worst we saw as well. as well a description of how erratic the results are and how desirable I think each system is.
Greater accuracy than a general indication of good and bad is anyway essentially worthless since we are attatching to gear which is in itself an unknown quantity.
Personally I agree that it is better to go for the good gear rather than compromise it for a nominal (and probably non-existent) increase in safety using poor pieces in the primary set-up. The idea is to stack the odds in our favour and concentrating on the good gear with systems which give consistent results has to be better than using an erratic system on a mixture of good and bad gear.
I still use the rope and clip the rest of the rubbish with whatever´s left on my rack in hope!
Jim
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philbox
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Sep 18, 2011, 8:36 AM
Post #77 of 88
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I've been having a play with the triple bunny ears. http://www.ehow.com/...gure-eight-knot.html
Each arm has equal amounts of rope i/e the same number of strands going to each piece in a three arm anchor. A little more fiddly to manipulate to more or less equalise than the double bunny ears.
Great discussion too by the way. I've had a play with load cells and equalisation. We came up with exactly what Jim Titt says about needing expensive pulleys to try to gain close to perfect equalisation.
With any anchor set up I do now I am looking for each piece to be bomber. Thus I am looking more for redundancy than equalisation.
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LostinMaine
Sep 18, 2011, 11:32 AM
Post #78 of 88
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I'm not sure I would consider known, massive unequal loading as outliers (at least not statistically to analyze a data set). Since this is a known phenomenon that can be recreated independently, it isn't "fair" to jacknife them out of analysis as it appears Long and Gains have done (though to be fair, I'm not sure they did this, it just appears that the figures do not correspond to their text).
This was the part that I was curious about - the high loading in an unequal "equalizing" system is repeatable.
Thanks!
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JimTitt
Sep 18, 2011, 4:47 PM
Post #79 of 88
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Outliers in tests for dynamic equalisation can´t in any way be ignored since it is a purely mechanical function with fairly clearly defined errors. If outliers occur one needs to look very carefully for the cause and prove that this really is the problem. Normally you would need to show you can both eliminate the outliers and create them as well, just using one of these as proof isn´t acceptable.
Outliers in a human performance can either be incorporated in the overall results or noted seperately to show that most of the time we achieve a given result but we may sometimes not!
Finding out how well people equalise is suprisingly difficult because they know they are being tested so tend to be more fussy than normal. I tried with one person keeping equalising until they were bored when things started to get sloppy, in real life which results apply is going to depend on a lot of things like whether they are fussy beginners, is it raining, was the route easy etc so all I can do is give some vague idea of what pattern does emerge and which systems are more prone to erratic results.
Since there are other, even more vague factors in play more accuracy would anyway give a false picture of the overall effect.
Jim
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jktinst
Sep 21, 2011, 10:08 PM
Post #80 of 88
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JimTitt wrote: If the system is truly frictionless then an off-centre drop will load the pieces equally since by definition there is no opposing force on the centre point, the load difference must be infinitely small since the moment one force is greater than the other the central point will move and make them equal.
JimTitt wrote: You´ve misread what I wrote, the difference in the DAV test was 1.3:1 which is considerably different to the tests you quoted.
JimTitt wrote: If the centre point karabiner doesn´t move for whatever reason there can be no dynamic equalisation
JimTitt wrote: With the pieces vertical it´s not only virtually impossible to equalise by hand but the slightest angular change completely unloads the upper piece immediately
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JimTitt
Sep 22, 2011, 6:29 AM
Post #81 of 88
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Confusion reigns! Perhaps I didn´t make it very clear to start with.
There are two ways to vary the loading on an equalising system. You can offset the drop weight onto an initially equalised system but you get the pendulum effect you discuss. Or you can alter the angle of load so that straight down isn´t down any more if you see what I mean (the same as if you started with your anchor equalised at a different angle to the load angle, for example if the belayer is stood to one side).
Both scenarios can and will exist in normal life and should be considered.
Edit to add:- My thinking is that the first (offset weight) tests the ability of an anchor to re-position the weight whereas the second (changed angle) tests the anchors ability to dynamically equalise. Since the basic concept is dynamic equalisation we should be performing the second test.
With an offset weight and a fixed karabiner the belay will be equalised in the end by virtue of the weight taking up a position below the fixed point (providing you got the point equalised correctly first).
With an change in angle of load with a fixed karabiner you get a reduction on one side as I described.
With a dynamic equalising system you also get a progressive reduction on one leg until you overcome friction and this reduction will remain effectively constant so the belay is then unequalised and remains so.
Where and what the peak loads are we will find out, it´s taking a bit of time because my normal drop tower can´t cope with weights swinging around (like most it has a sliding weight) and I have to build something different.
As to the rest;- I´m not trying to duplicate anyones tests nor compare with them, someone else can do that. Using someone elses methodology is only a way to prove what they did was correct, not that their test protocol was correct in the first place. The world of science (and climbing literature) is full of errors from this approach and it is better to try to work from first principles to determine exactly what to and how to test.
Jim
(This post was edited by JimTitt on Sep 22, 2011, 9:36 AM)
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jktinst
Sep 25, 2011, 7:56 PM
Post #82 of 88
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Oooh boy! And I did know, once upon a time, that drop towers have the weight on a fixed track with no swinging possible but I was focused on the fact that ultimately, we need to model an arrest of a leader falling directly on the belay from a position up and off to the side of it, which will necessarily involve some swinging. So it was with those blinders on that I read everything you reported. Sorry.
Based on what I just said, you can probably gather that I don’t necessarily agree that it is better to do a "track drop" on a system that has been pre-equalized in a direction different from that of the track (ie different from down) rather than a "DAV-like" offset drop + swing. After all, equalization is just a means to ensure a more even spread of the force of an FF2 fall and it seems to me that the DAV tests mimic such a fall pretty realistically.
Pretty much the only result I understand from the report is that illustrated in Fig 4 showing that the ratio on a sliding X is 59:45 (the 1:1.3 ratio you had mentioned) with the higher load on the arm furthest from the axis of the drop. Of course I still wonder when, during the drop and swing, that measurement was taken but I'll assume for now that the ratio is representative of the highest load applied to each arm (for those who haven't looked at the report: this adds up to more than 100% because the fairly wide 60 deg angle results in an overall load on both anchors higher than that applied by the dropped weight).
I'm also guessing from previous posts here that the second test (with the fuse blowing one arm and leading to an additional 60 cm shock-loaded drop of both leader and belayer) is what led them to conclude that it was more important to rig for redundancy and no extension than for equalization. However, I find it quite frustrating to see an illustration of an extension-limited sliding X in the report and have no idea whether there is any result or discussion corresponding to it.
Despite this conclusion that redundancy and no extension should take precedence over equalization, the lone result I understand, if anything, encourages me to stick with internally-redundant, extension-limited equalizing systems. I don't know if they tried to extrapolate from two-bolt anchors to 3 (and more) clean pro systems but that is where equalization becomes important, IMO. I feel that 59:45 was really pretty good for a drop offset by 1m laterally on a sliding X made with a tape sling (which is more prone to the clutch effect than cord). It also seems to me that this result could actually be applied to improving equalization, although I'm going out on a limb extrapolating on a single result while understanding nothing of the rest of the report.
Since stacked binary systems (2 stacked 50:50 systems giving a theoretical distribution of 50:25:25) are pretty direct extrapolations of the DAV test and since that is the kind of rig I use most frequently for 3-pro belay anchors, I'll take them as an example. In many cases, between the topo and a quick look around from the belay, it is pretty clear where the next pitch starts with respect to the belay location, ie, which side of the belay an FF2 leader fall would have to be on. Say it would be on the left. If you rig the belay with the two "25" arms to the left, according to the DAV test, a fall will load the further "50" arm even more. Back of an envelope calculations applying the DAV ratio to each part of the system suggest that you might get something like 20:25:60. If, on the other hand, you rig the belay with the two "25" arms on the right, you might get something in the order of 45:25:35, which would be much better and plenty good enough for me.
You might also make the friction work to advantage even if the next pitch starts straight above the belay by simply pre-equalizing the biner in a position shifted towards the two "25" arms. By doing so, you'd artificially create an offset drop that will, again, yield a better distribution than the 50:25:25 theoretical values. Since you get to decide how to stack and which way to shift, you should also be able to do it so the "50" arm is clipped to the stronger one of the outside pros.
(This post was edited by jktinst on Sep 26, 2011, 2:15 AM)
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JimTitt
Sep 26, 2011, 8:18 AM
Post #83 of 88
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The drop tower thing is a problem because the weight has to pass the fixed point of whatever you are testing so it is offset, usually forwards. When the weight hits the end of the rope for example it swings backwards and when the rope breaks it goes somewhere, the health and safety guys don´t find having an 80kg weight flying uncontrolled through the air the coolest thing in the world so either you build a big tower outside to allow it to be contained or you slide the weight between two steel girders. For the belay stuff we have to allow the weight to move so need an open system which is why the DAV tests were done on their climbing wall, not the drop tower they normally use.
In reply to: After all, equalization is just a means to ensure a more even spread of the force of an FF2 fall and it seems to me that the DAV tests mimic such a fall pretty realistically.
We should test to see if dynamic equalisation occurs at all and with what limitations. Once we know whether it occurs or not we can then apply this knowledge to different scenarios, not as has previously been done, select a scenario and extrapolae the results to all cases. Especially when the scenarios chosen have never been tested or proven to initiate dynamic equalisation anyway.
The load split from the DAV will almost certainly be the highest force felt by each piece since this is the point of interest, these peak loads may have a time offset but this is normal in dynamic systems and doesn´t alter the load felt and thus the potential for failure.
The limited sliding X was not tested as the it was considered too laborious, in particular untying the knots after loading was considered impracticable (I´d agree with that!).
Their conclusion is that since in their test using a sliding X only resulted in a 3% benefit in equalising the force compared with a fixed system but had the potential for a 40% worse result if one peice failed then a fixed system is preferable. As I´ve mentioned above, this is one scenario and I wouldn´t agree with this conclusion in others for example where the load angle changed substantially more or less.
Jim
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jktinst
Sep 28, 2011, 10:40 PM
Post #84 of 88
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At first, I couldn’t figure out how the central loop of the "Kräfteverteilung mit Reihenschaltungsschlinge" was rigged but I found a more detailed method for it in here http://www.alpenverein-muenchen-oberland.de/...latzbau_juli_091.pdf(p.17). It seems that the apparently improved equalization of this system with respect to the tape-cordelette system can only come from 2 sources :
- greater stretch on the single-strand arms compared to the double-strand arms of the cordelette; and/or
- slippage of the clove hitches linking the single-strand arms to the anchor biners.
If the first effect is significant, it would support Patto’s assertion earlier in this thread that using dynamic cord for the cordelette would improve equalization.
I’m not sure that I would consider either of these two effects a particularly advantageous trade-off in order to achieve a distribution ratio approaching that of the sliding X while using a fixed biner. For those who do consider this an OK trade-off, I’ll mention that you should be able to achieve similar (apparent) increases in equalization with a classic cordelette. Adding a clove hitch on each pro’s biner, adjusted so that one strand of each arm is statically equalized with the others arms and the other strands are left slack would not only provide a static equalizing stretch similar to the "Kräfteverteilung mit Reihenschaltungsschlinge" but, unlike it, this cordelette variation would be adaptable to multi-pro systems and provide a separate back-up strand for each arm.
I keep going on with the "apparently" regarding the DAV measurements. That’s because I have questions about their measurements too. Having a single overall load distribution ratio representative of the highest load that each arm was subjected to is good but the time factor remains pretty critical, in my opinion, because that is what will make the difference between real dynamic equalization and successive loading of each pro in turn over the course of the swing.
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JimTitt
Sep 29, 2011, 7:37 AM
Post #85 of 88
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The central knot is a bowline on a bight which is considered to be the best knot for forming a loop in tape, single or double. Apart from being strong and secure it has the advantage that it is easily undone after loading.
One problem with tying an overhand or fig.8 in cord is that there is so much material in the knot with considerably different length paths, unless you pre-tied a cordalette and pre-loaded the each strand to tighten it up you will never be able to control the load split. The other problem is to judge where the knot will end up and thus where you should equalise to, with unequal leg systems this is a real problem and multiple piece systems it seems impossible.
The highest loads on each piece are all that is interesting since the purpose is to find systems which reduce the potential of any piece becoming loaded to failure. That one piece recieves it´s maximum load before the other makes no difference to succes or failure of the system and is anyway inevitable unless you can eliminate friction.
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jktinst
Sep 29, 2011, 2:52 PM
Post #86 of 88
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"Bowline on a bight" rings a bell. I must have seen the name in a manual but I’d never stopped before to decipher the diagrams and try it out. Thanks for the info on it. It does seem pretty useful. I was taught the butterfly knot, which I like for its 3-way pull compatibility but it does cinch pretty tight and makes only a single-stranded loop. Thanks also for the reality check on the "successive loading" issue. I was hung up on that but, of course, what’s bad about successive - as opposed to simultaneous - loading is that it will put a disproportionate share of the load on one pro, which, as you point out, will be reflected in the overall distribution ratio.
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JimTitt
Sep 29, 2011, 5:12 PM
Post #87 of 88
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Bowline on a bight is dead handy, it´s a common knot for tying in with in Germany in it´s re-threaded form. It has two great virtues, it can take ring loading and is easy to untie after loading.
In tape it´s handy because you get a doubled thickness for the karabiner loop, it´s probably the strongest knot around and you can still untie it after loading, we use it for the pulling end when we are textile testing for this reason.
Certainly some people seem to have not really considered how the loading occurs, with sliding systems and friction the peak loads will have a time split but with fixed systems the loads should be simoultaneous. We see the time offset in the loads clearly with drop tests on belay systems where the peak loads on one part may well occur when there is no load on another. This is where you need traces of the forces to seperate the different parts out, of course whether it makes a difference is another thing and whether we can do anything about it is yet another!
Jim
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donwanadi
Nov 10, 2011, 6:22 PM
Post #88 of 88
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Neoshade wrote: So, In the interest of "dynamic equlization" (which a knot really can't claim) I thought I'd take a whack at the hornets' nest :D Haters be hatin', so... Yo Dawg! I heard you like Sliding-X's... So put I a Sliding-X on yo' Sliding-X! [image]http://farm7.static.flickr.com/6061/6056219593_1fc4f87916_b.jpg[/image] [image]http://farm7.static.flickr.com/6188/6056788414_4f98506ffd_b.jpg[/image] Now THAT'S a handy little truly-self-equalizing leg on a cordalette (or equalette in this case). Seriously, the Double-8 is a pretty sweet and versatile knot! Enjoy. (And bring on the hate )
Looks like you made a poor man's Trango Alpine Equalizer. 
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