|
|
|
|
healyje
Feb 20, 2006, 12:18 AM
Post #126 of 915
(123898 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
In reply to: Perhaps the two are mutually exclusive
I think to some degree this is what makes this such a difficult problem - that equalization and extension are somewhat mutually exclusive goals. And to those I would add redunancy, which the AE-type anchors don't past muster on. As RGold points out, the minute you add a limiting knot to the works equalization goes out the window. While it doesn't necessarily "feel" right to look at, the "DuoGlide" rig you guys suggested does represent a pretty fair compromise of the three - equalization, extension, and redundancy. I like the AE rigs in general, and again as RGold points out, you can manage the extension problem by keeping them compact - but I would get quite nervous about the lack of redundancy in the case of using it for, say, a portaledge anchor. So I did play around with the DuoGlide, a bunch of different AE rigs, and I guess in the end I can live with the DuoGlide a bit more comfortably than the others even if I do get a tad nervous about relying on a single overhand knot if one side blew completely. But all-in-all in the end I just can't see any obvious way around the "mutual exclusion" problem no matter how "clever" I try to be.
Also, with regards to tied AE rigs - I did do one with alpine butterflies, but it seems so much simpler to just fold over a section of the doubled cord and tie a figure 8 giving two loops out the bottom for the anchor and one out the top for equalization.
|
|
|
|
|
dr.ed
Deleted
Feb 20, 2006, 12:41 AM
Post #127 of 915
(123898 views)
Shortcut
Registered:
Posts:
|
A very interesting and thought provoking thread. And kudos to John for an honest and open approach to rethinking his Anchors book recommendation.
Just musing about the topic I am trying to understand what the important issue is, so if I am way behind all of you I'm sorry.
The first issue being addressed is what rig distributes the load of a fall evenly among all of the anchors. In an idealized case, the cord rigging the anchors must be able to run unconstrained. In an impractical setup, each anchor has a pulley through which the rig ran, each strand connecting one anchor to another would also have a pulley, and those pulleys would connect together to the master point. In this case, the master point is free to move as is the rig, this would always distribute the load evenly.
If an anchor fails, then the rig lengthens by some amount shock loading the remaining anchors, evenly. This may still be too much loading for the remaining anchors.
If the rig is constrained from running free through all of the anchors, then there is no way to get an even distribution of a load among all of the anchors. That is a statement which may not be strictly true, and I will have to think about it more carefully, one anchor constraint may be possible, but I am sure that many are not. Richard might be able to give a proof actually, the master point lies on a surface of constraint.
Here is my guess at an optimum solution. For two anchors, a sliding X, for three anchors, three slideing X's. In this case, the load is almost always equalized by one of the X's among two anchors, with care it might be possible to have 2 of the X's equalizing. Now if any of the anchors fails, the X between the two surviving anchors takes over, with minimal shock and equalized load.
Still kind of tricky to set up.
This post is way to long and probably garbled... but maybe it helps illustrate the issues.
Ed Hartouni
|
|
|
|
|
vivalargo
Feb 20, 2006, 1:47 AM
Post #129 of 915
(123898 views)
Shortcut
Registered: Nov 26, 2002
Posts: 1512
|
In reply to: [JL: Unfortunately, limiter knots keep whatever leg you tie them in from equalizing through the biner that leg is on. GO
Not exactly what you mean by "through the biner," if you mean the pulley effect of just that anchoir that the biner is clipped through. But in the actual tests we've found that a 2 point anchor can be rigged with limiter knots and the rig (the Quad) achieves almost perfect equalization with a limited amount of direction of pull change as well. This is achieved, I think, because the master point slips along a section of cord strung between the limiter knots.
But we are getting down to brass tacs here, and that's a good thing. But as good as stuff can sound here on this thread, I've learned it all must be tested to know for sure.
JL
|
|
|
|
|
kachoong
Feb 20, 2006, 1:50 AM
Post #130 of 915
(123898 views)
Shortcut
Registered: Jan 23, 2004
Posts: 15304
|
In reply to: In reply to: Jeremy--As you wrote that Tom Cecil is field testing a similar rig with butterfly knots but I think your system looks cleaner and simplier. I think you'd want some limiter knots in the arms or the extension problem would be pretty considerable. So long as you have a sliding master point the limiter knots don't compromise equalization if the direction of pull doesn't get real screwy. That's a really clean looking system, Jeremy. Very cool system, Jeremy! JL: Unfortunately, limiter knots keep whatever leg you tie them in from equalizing through the biner that leg is on. However with a reasonably short cordelette, the extension if one leg blows is reasonably small. If I used this system, I'd probably use add a sling to make one leg much longer than the others. That way no one leg will create a major extension if it blows. GO
Good job Jeremy. I first looked at your setup and thought ....why isn't there a twist in each V coming down to your sliding lockers? So I set up myself and had a play and found when one piece pulled (despite the excess extention explained by John and Gabe) the locker was still 'captured' in the setup once fully extended on the remaining pieces.
|
|
|
|
|
cracklover
Feb 20, 2006, 2:10 AM
Post #131 of 915
(123898 views)
Shortcut
Registered: Nov 14, 2002
Posts: 10162
|
In reply to: In reply to: [JL: Unfortunately, limiter knots keep whatever leg you tie them in from equalizing through the biner that leg is on. GO Not exactly what you mean by "through the biner," if you mean the pulley effect of just that anchoir that the biner is clipped through.
Yup, that's what I meant. But it's more complicated than I first thought. Will play around some more, and then perhaps post my findings on a separate thread.
But if anyone has other new ideas, this seems a great place to put 'em out there.
Cheers!
GO
|
|
|
|
|
kachoong
Feb 20, 2006, 2:36 AM
Post #132 of 915
(123898 views)
Shortcut
Registered: Jan 23, 2004
Posts: 15304
|
Tried a few different things over the last half hour and came up with something I liked. It's just an idea to help throw in the pool. It's similar to Jeremy's, however I wasn't satisfied with the butterfly setup as it was too bulky and slower to set up than this one.
I also found that putting a limiter knot on the middle leg didn't allow it to slide and equalize. (unless I'm doing something wrong) :? It only worked with limiter knots on the outside legs.
My set up here uses clove hitches tied with the outside strand of the outside leg, tied to the 'bottom' of a locking biner (on each side), where the top of the biner is free to slide through the V's made with the centre piece. When it's loaded by the belayer the locking biners sit correctly and don't rotate at all when you slide from side to side. Again, as mentioned, friction causes problems the more pieces you use. This could be countered by using those pulley-type biners at each anchor point (you know, the ones with the little wheels on one end.) This picture shows no limiter knots on the outside legs. It would be preferable to use them if strength isn't considerably compromised.
http://www.rockclimbing.com/...p.cgi?Detailed=69733
|
|
|
|
|
moose_droppings
Feb 20, 2006, 2:59 AM
Post #133 of 915
(123898 views)
Shortcut
Registered: Jun 7, 2005
Posts: 3371
|
Dr Ed,
I've played with tha 3x's idea, have 1 hanging in my doorway right now, and your right, its a handfull to set up.
Like this,
http://i1.tinypic.com/o6bbt3.jpg
John, here's another try at the other one. Basicaly, you start out like a regular 3 legged cordelette anchor, but instead of tying of an overhead knot for the power point, just clip a biner to all the strands. Then tie a limiter knot on the middle leg right above the pp. This reduces extention if the middle leg blows. To reduce the extention on the outer two legs, clip a biner into the middle leg, right above the upper knot, out to the loop on the right outer leg, and another biner in the same spot on the middle leg, out to the loop on the left leg. The middle leg is kept at fixed lenght while the other two are allowed to share a common strand and equalize the whole works. If any one of the 3 legs blow, the extention is about 3". Since my 1st post I've set this up on another doorway downstairs here and swung from side to side on the anchor and the equalization is great throughout the arc.
Hope this mickey mouse drawing is a little clearer for you.
http://i1.tinypic.com/o6bn9y.jpg
|
|
|
|
|
cracklover
Feb 20, 2006, 3:15 AM
Post #134 of 915
(123898 views)
Shortcut
Registered: Nov 14, 2002
Posts: 10162
|
In reply to: Will play around some more, and then perhaps post my findings on a separate thread.
Okay, well my findings are simple, so I'll post 'em here. Tie a limiter on an outer leg of Jeremy's anchor and you're fine. Tie off more than one leg, or the inner of the three, and you lose dynamic equalization.
I also built Moose's setup. Brilliant! It's easy to set up, very successful at limiting extension, and allows a wide range of motion. I'd be curious to see how it performs on the machine John's using for testing. The only things I'd be concerned about are 1: Whether you get any larger forces if the pieces are spread out at a large angle, due to the pseudo American Triangle in the sytem and 2: whether all those slings can move freely in the event that one of the pieces blows.
One other note on building the Mooselette: you must make sure to create and clip a "crossed sling" with the outer strands, otherwise the lower limiter knot won't work.
Very cool work, guys!
GO
|
|
|
|
|
kachoong
Feb 20, 2006, 3:20 AM
Post #135 of 915
(123898 views)
Shortcut
Registered: Jan 23, 2004
Posts: 15304
|
In reply to: The only things I'd be concerned about are 1: Whether you get any larger forces if the pieces are spread out at a large angle, due to the pseudo American Triangle in the sytem and
This is all exciting stuff....
|
|
|
|
|
gordo
Feb 20, 2006, 3:59 AM
Post #136 of 915
(123898 views)
Shortcut
Registered: Nov 5, 2005
Posts: 111
|
Am I the only one right now who's thinking redundancy may be more important than perfect equalization? I've been building and building and changing and re-building...and everything I do along the lines of this thread leaves me wondering.
Jeremy's rig is perfect EQ, but I just couldn't live with it on top of a 300 foot wall. Given bomber pieces I'd feel safer with a good old, poorly EQ'd cordolette than any of these rigs with no redundancy. I just gotta have more than one loop of cord/webbing to put my life on. Given poor placements, I'd rather EQ with sliding x and combine with cordolette.
I know, never heard of one breaking. but it's possable.
I guess we're still looking for that perfect rig, I hope John shows us exacly what he's thinking soon :)
|
|
|
|
|
bloodyhands
Feb 20, 2006, 4:15 AM
Post #137 of 915
(123898 views)
Shortcut
Registered: Nov 29, 2005
Posts: 78
|
In reply to: Am I the only one right now who's thinking redundancy may be more important than perfect equalization?
I inspect my slings and cordelettes before every climb. I've never been that concerned with redundancy on trusted gear.
|
|
|
|
|
cracklover
Feb 20, 2006, 4:29 AM
Post #138 of 915
(123898 views)
Shortcut
Registered: Nov 14, 2002
Posts: 10162
|
In reply to: In reply to: Am I the only one right now who's thinking redundancy may be more important than perfect equalization? I inspect my slings and cordelettes before every climb. I've never been that concerned with redundancy on trusted gear.
Fair enough, but it wouldn't take a very big falling rock to slice through/crush a singl strande of cordelette.
You could clip directly into your best piece with your rope (with some slack in it) as a backup.
GO
|
|
|
|
|
bloodyhands
Feb 20, 2006, 4:47 AM
Post #139 of 915
(123898 views)
Shortcut
Registered: Nov 29, 2005
Posts: 78
|
In reply to: In reply to: In reply to: Am I the only one right now who's thinking redundancy may be more important than perfect equalization? I inspect my slings and cordelettes before every climb. I've never been that concerned with redundancy on trusted gear. Fair enough, but it wouldn't take a very big falling rock to slice through/crush a singl strande of cordelette. You could clip directly into your best piece with your rope (with some slack in it) as a backup. GO
Good point. Good idea.
|
|
|
|
|
gordo
Feb 20, 2006, 5:00 AM
Post #140 of 915
(123898 views)
Shortcut
Registered: Nov 5, 2005
Posts: 111
|
Ok, so the search goes on. I've got this one working right now. I call it the Gordo-lette ( :roll: Yeah, I know)
Sorry the pics are really bad, my flash quit.
http://members.cox.net/gbisapk/Gordo-lette.jpg
Drawing....very important to note that the inside strands on the outside loops are free to move.
http://members.cox.net/...esrc/Gordo-lette.bmp
This provides very little extension, and full redundancy. Cut any leg and you get the same extension as loosing any piece of the anchor. The cloves will need to be adjusted to get them level for whatever arrangement the pieces are in. Moving the master point around moves the cloved biners but keeps the system equalized. I'll get a better pic tomorrow if I haven't figured out the glaring reason this is dumb.
|
|
|
|
|
jakedatc
Feb 20, 2006, 5:30 AM
Post #141 of 915
(123898 views)
Shortcut
Registered: Mar 12, 2003
Posts: 11054
|
few things.. put it on a light background so it doesnt blend in. if you turn the flash off it should eliminate the glare and just use natural light.
are the oval biners at all weighted? if so having them horizontal like that seems like it wouldnt be the strongest orientation.
i like kachoongs the best so far. as long as it's redundant if any of the legs blow out it'll extend and still be ok. Simple and pretty speedy if you just leave the powerpoint and cloves intact on the rack.
conspiracty theory: JL has no anchor and is trying to suck us for information ;)
|
|
|
|
|
gordo
Feb 20, 2006, 5:37 AM
Post #142 of 915
(123898 views)
Shortcut
Registered: Nov 5, 2005
Posts: 111
|
In reply to: are the oval biners at all weighted? if so having them horizontal like that seems like it wouldn't be the strongest orientation. i like kachoongs the best so far. as long as it's redundant
The biners (would be locking if real) are only weighted in a failure mode, then it is weighted vertically.
I started with something like kachooongs...but I see it as zero redundency...am I missing something? Looks like if it blows the cord it's gone completely.
I like the conspiracy theory!! :lol:
I'll build this tomorrow with clothes line, start cutting strands and stuff, see what it's really doing. So far, it seems to be the best of all worlds. Pretty quick to rig too.
|
|
|
|
|
jakedatc
Feb 20, 2006, 5:57 AM
Post #143 of 915
(123898 views)
Shortcut
Registered: Mar 12, 2003
Posts: 11054
|
Cool.. seems like your knots sacrifice quicker equalizing(having to adjust the knots and slide them etc) for more redundancy.
glad you like it ;) we're keeping an eye on you john *squints* (and reading the Close calls book... though i'm not sure if thats such a good idea combined with an anchor thread... :shock: )
|
|
|
|
|
dr.ed
Deleted
Feb 20, 2006, 8:00 AM
Post #144 of 915
(123898 views)
Shortcut
Registered:
Posts:
|
Moose - not quite what I had in mind... instead of the third X connecting the two X's, the third X connects the two pieces which are not directly connected. Also, no knots...
my guess is to make this work, you have to put three 'biners (one for each X) and perhaps a cordellete to the three 'biners to a master point.
As I said, this gets complicated. But the idea is that you have optimally equalized the pieces, and reduced the effect of shock loading.
The shock loading comes from the change of momentum over the time to change the momentum. If the belay is "dynamic" the time to stop (change the momentum to zero) lengthens and the force decreases considerably.
F_shock = (delta p)/(delta t)
you can't do much about (delta p)...
|
|
|
|
|
healyje
Feb 20, 2006, 10:09 AM
Post #145 of 915
(123898 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
The difference in the central knot structures of the [pure] AE rigs shown so far adds up to "six of one - half dozen of the other" from my perspective. I don't really see any particular advantages to using either butterflies (Jeremy's) or cloves (Kachoong) over a doubled over figure 8 as shown below. And for that matter I'm not all that convinced that two carabiners makes all that much difference compared with one for equalizing when everything is said and done. If you folks think there are advantages to these other knot structures over the figure 8 below I'd be interested what you think they are and why.
But I do agree with Gordo on redundancy. In my previous post I also mentioned not being comfortable with the fact [pure] AE rigs lack redundancy and limiter knots (or two extra limiting carabiners ala Gordo) pretty much defeat the whole point of using them. The more I think about the whole affair the more it makes me want a completely redundant, double-stranded 5mm tech cord AE rig or a backup tech cord X on each half of the AE rig.
And John, are you now using "Quad" and "DuoGlide" interchangeably or is this yet a different one?
http://www.cascadeclimbers.com/...6299DuoGlide_008.jpg
http://www.cascadeclimbers.com/...6299DuoGlide_009.jpg
|
|
|
|
|
patto
Feb 20, 2006, 2:03 PM
Post #146 of 915
(123898 views)
Shortcut
Registered: Nov 15, 2005
Posts: 1453
|
In reply to: Am I the only one right now who's thinking redundancy may be more important than perfect equalization? I've been building and building and changing and re-building...and everything I do along the lines of this thread leaves me wondering. Jeremy's rig is perfect EQ, but I just couldn't live with it on top of a 300 foot wall. Given bomber pieces I'd feel safer with a good old, poorly EQ'd cordolette than any of these rigs with no redundancy. I just gotta have more than one loop of cord/webbing to put my life on. Given poor placements, I'd rather EQ with sliding x and combine with cordolette. I know, never heard of one breaking. but it's possable. I guess we're still looking for that perfect rig, I hope John shows us exacly what he's thinking soon :)
I completely agree.
I have never fooled myself into thinking that the pieces were truly equalised. Although equalising 3 or more pieces is very difficult, you can always achieve rough load spreading across two pieces, this in my eyes is enough.
|
|
|
|
|
gordo
Feb 20, 2006, 2:33 PM
Post #147 of 915
(123898 views)
Shortcut
Registered: Nov 5, 2005
Posts: 111
|
In reply to: [pure] AE rigs lack redundancy and limiter knots ( or two extra limiting carabiners ala Gordo) pretty much defeat the whole point of using them.
Trying not to sound defensive, as I'm not. I doubt this thing will be the answer. BUT.....
The beauty of the biners as I have them is that they don't defeat the equalization like limiter knots do. Build it real quick and move it around. The eq stays perfect because the biners don't tie the legs together, but rather connect the opposite sides strands for redundancy only. It acts like the AE except for limited extension and full redundancy.
After a lot of working it around, I've decided the way to do it is remove the biners after every use. Setting up the AE takes seconds, then adding 4 cloves on 2 biners takes about 2 minutes.
I've built every rig here, and more. I'm having a great time with this, glad to have something to do while the snow/ice keeps me indoors :(
|
|
|
|
|
dominic7
Feb 20, 2006, 3:18 PM
Post #148 of 915
(123898 views)
Shortcut
Registered: Mar 7, 2005
Posts: 18646
|
In reply to: In reply to: Perhaps the two are mutually exclusive John, I think to some degree this is what makes this such a difficult problem - that equalization and extension are somewhat mutually exclusive goals.
An important point. If you take, for arguments sake, that an equalizing system does not limit extension, we could look to other ways of limiting extension. Some general points:
"some" extension isn't necessarily catastrophic as shockloading isn't as much of a risk as it's made out in some circles The extension of a truly equalizing system is a function of the lengths of the legs. In general, a system will extend somewhere less 2x the length of the failing leg, depending on the angle of the leg. One might surmise that limiting the lengths of the legs would thus limit the extension potential of the system. The minimum safe length of the legs of any given anchor is different, where an anchor with vertically aligned legs could have the shortest and a horizontally aligned anchor the longest. An equalizing anchor could be constructed that allowed for adjustment of the leg lengths to bring them to the minimum length, thus minimizing the potential extension of the system.
For instance you could use a munter hitch in an equalizing anchor that you could slide up to the point where you felt the legs were the shortest they could be to give safe angles between the legs. Then you would have an equalizing anchor that had the minimum extension. I couldn't quite get it right but I have to run to work so this is all I could come up with:
http://rugby.net/images/domolette1.jpg
(sorry for the poor image quality - camera phone)
I would also like to point out that I am not a professional climber, or even a very good or experienced one for that matter. If you are reading this, do not assume that the above picture or anything I say represents something that is safe for climbing.
|
|
|
|
|
dingus
Feb 20, 2006, 3:26 PM
Post #149 of 915
(123898 views)
Shortcut
Registered: Dec 16, 2002
Posts: 17398
|
Most of these proposals totally blow the KISS principle out of the water. I think the chance of mis-rigging increase very quickly each time you add a knot to the assembly, especially if that knot is not a figure 8... the defacto standard.
I look at some of these riggings and imagine trying to teach that to Billy Bob Noob...
DMT
|
|
|
|
|
ambler
Feb 20, 2006, 3:45 PM
Post #150 of 915
(123866 views)
Shortcut
Registered: Jul 27, 2002
Posts: 1690
|
In reply to: In reply to: In reply to: Am I the only one right now who's thinking redundancy may be more important than perfect equalization? I inspect my slings and cordelettes before every climb. I've never been that concerned with redundancy on trusted gear. Fair enough, but it wouldn't take a very big falling rock to slice through/crush a singl strande of cordelette.
On an unrelated note ... for some reason this thread about equalization makes me think of Bridwell's infamous clove-hitched RURP belay (was it Sea of Dreams?). Anyone know an online source for that photo?
|
|
|
|
|
|
