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antiqued
Mar 1, 2006, 11:55 PM
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Craig
Maybe it is overkill in the thought department, but some of us are considering (and stated a long, long time ago, in web spaces somewhere or other) that static belays can happen - when the full length runout goes bad, or when the rope snags around your leg, a root, catches in a crack, or snarls up badly and jams in the tube.
I'm sure that most belay failures don't involve full factor 2 falls of that static nature, but that is the 'gold standard' for designing a belay.
Sometimes you can't afford the gold standard - those may be the times when it is most important to understand how to get closer to it.
And rock failure does happen - new routing last year I pulled a piece out of a deep,clean looking parallel crack with a testing jerk - rock failure, with absolutely no visible cue. Even before that, my idea of redundancy is to use different cracks - I'm not as happy with three cams in a Yosemite splitter as I am adding some other feature.
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justthemaid
Mar 2, 2006, 12:37 AM
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In reply to: In reply to: Unlike the mooselette and gordolette, the charles-rig seems to work in vertical Incorrect. If you take out the 2 biners that restrict extension, it will swing in 360degrees. When placed in a vertical, you can utilize the biners from the pro connections to reduce the extension. Two less biners in vertical orientation.
Oops- sorry Moose, I spoke to soon. You are correct. I didn't start testing all this stuff in the vertical till this morning.
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roy_hinkley_jr
Mar 2, 2006, 1:13 AM
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Craig, your forces chapter is a step in the right direction but I'm hoping Largo will go the extra mile. So far, he's done a mediocre job explaining this stuff and you only scratch the surface (granted you cover a lot more ground). An entire book on anchors really should explain the basics in clear language and with good diagrams.
Your book is an accomplishment in that it brings a lot of information on many subjects together. It's also highly irritating in that I haven't found a chapter yet without technical inaccuracies, historical falsehoods, and/or broad statements that don't hold up. You really should have let more climbers proof the manuscript. It's a good counterpoint to FOTH but not a replacement, or a first choice, by a long shot. Can't say that I've seen anything in it that hasn't been written about before but it's a decent compilation.
In reply to: And Rob.calm, you might already be leading on a static rope. Ropes lose a lot of energy absorbing capability as they age or after they have been fallen on repeatedly.
This is but one example of where you're blowing smoke out your butt. It's off topic for this thread so we'll just leave it at that.
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billl7
Mar 2, 2006, 3:04 AM
Post #405 of 915
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In reply to: I've been messing with the charles-rig. I'm finding I have to put extra turns in the upper biner of the central line to even it up (which isn't really a big deal I guess.).... I'll keep playing.
Couple minor comments:
a) unbalance the two strands in one direction and all the load is on the outer pieces; unbalance the two strands in the other direction and the middle piece gets half the load with 1/4 load out to each side.
b) some amount of symmetry (angles between pieces) is required in order to distribute the load across all three pieces under varying directions of load; otherwise, for all but the initial load direction, only two pieces are loaded (albeit equalized!);
And as knudenoggin mentioned, lose the middle piece and an outside piece and the cordalette fully extends. Granted, must have two of the three pieces fail for this.
Bill L.
edit: added comment "b"
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healyje
Mar 2, 2006, 3:09 AM
Post #406 of 915
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Jake, could you add the moosolette to that list in the post or does moose have a picture other than the diagram? Thanks for that list post.
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rgold
Mar 2, 2006, 3:15 AM
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I believe in the utility of mathematical models, but unfortunately one needs to know what assumptions are built in. At one time, Petzl gave the mathematics used by their model, and it was the standard conservation of energy calculations of the sort set forth in Attaway and known for more than sixty years. Although a very useful first approximation, these calculations should not be viewed as "real world" results.
The current incarnation of the calculator looks the same as the older version, but no longer has an accompanying account of the mathematics (at least that I could find). If you try a factor 2 fall belayed by a Reverso on the Petzl calculator, you get an anchor load of 2 kN and 4 m of slip through the belay. Now I have had the unpleasant task of holding a factor 2 fall once, and I can guarantee that nothing anywhere near 4 m went through my (hip) belay. If you let a enough rope slip through the belay under tension, you can keep the impact arbitrarily low, but whether this is what will happen in most cases, and therefore whether this represents something about the "real world," is open to question. It certainly is hard to believe that the four-piece distributed load anchor that failed in the Middle Cathedral Rock tragedy had no piece able to withstand 2 kN. On the other hand, if we are to believe the 2 kN number as a feature of the "real-world," then a properly equalized four-point anchor made up of RP's should be able to stop a factor 2 fall onto the belay. Wanna tie your grandmother to such an anchor with you, lob off an 80 kg weight, and stop a factor 2 fall as an expression of your confidence in this result? (Those of you who hate your grandmother need not reply.)
I might add that the Italian mathematical model, which seems to be the best around, and which has the added benefit of having its results verified by actual drop tests, predicts a 1.5 kN upward load on the belay anchor when catching a much less severe factor 1 fall through a single protection point. The model includes the effects of lifting the belayer and of the belayer's friction against the wall, effects that won't be present in the factor 2 scenario. The Petzl calculator predicts an impact only .5 kN larger for a fall with double the fall factor, fewer mitigating factors, and no intermediate runner, presumably by virtue of letting 4 m of rope run through the belay under tension. I'm just not sure this is telling me real-world information that I should base my anchor policies on.
I think what we have in this thread is a very interesting brain-storming session in which people are looking for a practical way to create a genuinely equalized anchor, one that will satisfy the "very severe" constraints that the rigging actually equalizes the peak load to the anchor.
Of course, most anchors will not need this kind of rigging, because the individual pieces will be good enough so that the redundancy offered by the classical non-orientable anchor is sufficient. On the other hand, when faced with less than perfect placements, it seems absurd not to have at least the option of a practical equalizing construction. If there is a way of doing this that is neither overly time intensive nor overly gear intensive, why wouldn't we all want to know this? No one (well, almost no one) is saying you have to use some complicated sliding set-up on every anchor. But why should you use an inferior non-orientable distributed anchor in a bad situation if a far better practical option is available? That's what I think this thread is about.
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cracklover
Mar 2, 2006, 4:32 AM
Post #408 of 915
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A few notes.
First, by popular demand, an actual photo of a Mooselette:
http://i26.photobucket.com/...riker/mooselette.jpg
Second, regarding the mooselette in a vertical crack setup:
In reply to: If you take out the 2 biners that restrict extension, it will swing in 360degrees. When placed in a vertical, you can utilize the biners from the pro connections to reduce the extension. Two less biners in vertical orientation.
You're right. Nifty. The real trouble with the mooselette in a vertical crack (this is a problem that's common to most of these setups, not just the Moose setup) is the difficulty of telling which strand is which.
Third, the charlesjmm setup is a bit finicky. The knots must be tied just right, or all of the force may go on the outer two pieces (whether it's three pieces or four, the same thing happens). Here's a picture illustrating a poorly tied charlesjmm anchor:
http://i26.photobucket.com/...riker/charlesjmm.jpg
Note that the crossed section is the only load-bearing section - the middle strands are loose.
If you tie the knots incorrectly with slack on the *other* side, it's less serious. Then what happens is that the crossed section bears no load, and the only defect is that the middle piece(s) bear twice the force of the outer two pieces. Here's a pic:
http://i26.photobucket.com/...iker/charlesjmm2.jpg
GO
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jakedatc
Mar 2, 2006, 5:17 AM
Post #409 of 915
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Moose... ur in the game! :P
u may all now return to the comforts of your slide rules and number crunching ;)
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billl7
Mar 2, 2006, 5:51 AM
Post #410 of 915
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In reply to: Third, the charlesjmm setup is a bit finicky. The knots must be tied just right, or all of the force may go on the outer two pieces (whether it's three pieces or four, the same thing happens). .... If you tie the knots incorrectly with slack on the *other* side, it's less serious. Then what happens is that the crossed section bears no load, and the only defect is that the middle piece(s) bear twice the force of the outer two pieces.
Another thought: Although the latest charlesjmm offers the possibility of full distribution across varying angles (assuming symmetric-enough placements), it seems that the cost is possible full extension for a two out of three piece failure as mentioned by knudenoggin. In practice, is it rediculous to worry about 2/3 piece failure??
And I'm a NOOB in this area so take the above with a grain of salt.
Bill L.
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knudenoggin
Mar 2, 2006, 7:12 AM
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In reply to: I now retract my previous comment that equalizing 4 equally strong placements is essentially impossible (but stand by my comment that attempting it is tantamount to concluding that none would hold body weight).
well aligned w/expected load, and in having thus to anchor on either side of that
line, one necessarily gets some load amplification from a broader angle,
becomes more vulnerable to a pendulum swing if losing anchorage to either
side, and so wants essentially double/backed-up surety on both sides of the
likely load axis?
(And, 6mm nylon cord was suggested, no? --that's not all so hefty!)
You seem to regard the Petzl calculator as Trvth: how has it been verified?
Are JL's current tests able to be correlated with Petzl F.C. predictions?
*knudeNoggin*
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healyje
Mar 2, 2006, 9:51 AM
Post #412 of 915
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Well, I'm a bit late to the moosolette, but now that I rig one I find it one of the more clever solutions - good job...
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healyje
Mar 2, 2006, 1:20 PM
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Charles, Like that one too for the minimal amount of hardware required...
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billl7
Mar 2, 2006, 2:02 PM
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In reply to: 3) Loosely setup the limiter knots on the outer legs at approximately the same height. 4) Apply a downward tug so as to remove slack. It’s neat to see how the power point calibrates itself. No further knot adjustment is needed.
Looks like that would do the trick. Wish I had thought of that myself - I'm such a rock. :lol:
I'll try that later but if someone gets a chance sooner, try setting the X before applying the downward tug as it seems that this would set the knots a tiny bit closer to the sweet spot.
Impressive work Charles!
Bill L.
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flyinglow
Mar 2, 2006, 2:12 PM
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charlesjmm: I like your setup, but the extension gets really ugly if 2 pieces blow on your 3 point setup. except for that unlikely prospect, it looks great.
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oldrnotboldr
Mar 2, 2006, 6:22 PM
Post #417 of 915
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I really like the looks of your set up Charles. I'm giving it a try in a couple of weeks on an upcoming ice climb. I'll try and remember to check back in after using your design. Thanks.
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justthemaid
Mar 2, 2006, 6:23 PM
Post #418 of 915
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In reply to: charlesjmm: I like your setup, but the extension gets really ugly if 2 pieces blow on your 3 point setup. except for that unlikely prospect, it looks great.
I've been trying to figure out a way to reduce the extension in this screnario. There's not really a good way. Actually, you get semi- ugly extension. Your failed piece of pro would likely jam in the biner preventing really ugly extension. Probably be pretty epic untangling the mess. Then again, if there is a possibility of 2 pieces failing, there probably should be a 4th piece in the mix.
Thanks for the pics Charles. I'm actually having better success working left to right (or right to left). i.e.:
1) Tie the left knot loose then even it up.
2) Twist the central twist- then even up again.
3) Tie the right knot loose-then even up.
4) Tug the whole thing tight to equalize.
It's a bummer the mooselette can have total failure if a strand is cut. I guess you could always just back it up by tying in directly with the climbing rope to 1 or 2 pieces.
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knudenoggin
Mar 2, 2006, 7:28 PM
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In reply to: where anchor performance is maximized.
loading, as I suspect the considerable friction of adjustment around 'biners will
see some significant bias at the anchor legs (the nearest one going slack).
There was a test of a theoretical "5-to-1" MA hauling rig posted to a canyoneering
forum which measured an actual MA of 1.6-to-1 (!!); a lot more is lost going
around even 'biners than one would think.
(Rig measured was: load up to inline Fig.8 loopknot, on up & around HMS 'biner,
back through loopknot eye, back through 'biner, back through eye, and
then hauled.)
*kNoggin*
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kachoong
Mar 2, 2006, 8:51 PM
Post #420 of 915
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I guess no one has commented on my design. With limiter knots six inches above the clove hitches on each outside leg, it works great for three placements. I should try four to see if it works. It doesn't fail if the cord is cut anywhere except the powerpoint itself. Equalization is broad and it works in vertical placements. Extention is minimal (with limiter knots) and set up is very quick and not fiddly at all. You don't need to have the cloves perfectly positioned for them to work.
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oldrnotboldr
Mar 2, 2006, 8:58 PM
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Maybe I'm looking at it wrong. It seems that if one outer leg and the center popped, wouldn't that shift the force to one strand of the cordelette?
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kachoong
Mar 2, 2006, 9:36 PM
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In reply to: Maybe I'm looking at it wrong. It seems that if one outer leg and the center popped, wouldn't that shift the force to one strand of the cordelette?
What I like about some of the others over mine is that you're clipping your powerpoint biner into more than one strand.
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parin
Mar 2, 2006, 9:38 PM
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In reply to: It doesn't fail if the cord is cut anywhere except the powerpoint itself.
Forgive me if I don't understand your design, but it seems to me that if any of the upper periphery cord is cut, the entire anchor fails.
Your design looks much like the trango alpine equalizer; it shares many of its features and short-commings.
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kachoong
Mar 2, 2006, 9:40 PM
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In reply to: In reply to: It doesn't fail if the cord is cut anywhere except the powerpoint itself. Forgive me if I don't understand your design, but it seems to me that if any of the upper periphery cord is cut, the entire anchor fails. Your design looks much like the trango alpine equalizer; it shares many of its features and short-commings. |
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kachoong
Mar 2, 2006, 9:49 PM
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Is that powerpoint knot a bunny-ears without "folding" the upper loop over the rest of the knot and in behind it? That's how I see it..... anyone?
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