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Feb 15, 2006, 2:53 PM
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In reply to: There is little evidence in this post of any understanding of physics. Energy and force is being completely confused in this post, it makes hardly any sense at all. To answer the final question, not it is unlikely to absorb much energy and would do more harm than good. Screamers work because they exert a force over a distance. Most of the time when a piece blows it blows suddenly and at a single point, thus very little energy is absorbed. EDIT: Sorry I don't mean to be rude, I was just posting how I see it. I noticed your location is Bucharest, nice one! You english is good! :)
I must admit that I didn't care to explain all the steps and the result is a little mixed-up. I'll try to help you reconsider your oppinion.
Here we are again: you have to agree that during a fall the potential energy (m*g*h) is converted into cinetic energy (m*v2/2). In order to stop this movement (at speed V) this energy is absorbed by the system (rope, friction device, friction with biners and rock, etc)
Decelerating the fall will produce a force (m*a) which will load the system.
Of course, the longer the time to absorb this energy, the lower the force will be (the priciple applied for a dynamic belay...). What I was speaking of, was that any piece of pro that breaks will absorb some amount of energy. The deceleration produced in the process will apply on the system (it's true, for a very short time) a force equal to the breaking strenght of the piece.
I was thinking of this because I've seen a whipper when the falling guy un-zipped 15 m of crack ripping 3 pitons and breaking a #2 wired nut, and the piece which finally holded the fall was a # 1 nut rated at 4 kN. How else could you explain this ?
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landgolier
Feb 15, 2006, 3:21 PM
Post #52 of 915
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I want to get out in front of this one before any more foolishness goes down, so excuse me if this is a bit terse, but...
The equations to calculate this crap in a meaningful way aren't in a high school physics text, and they probably aren't in a first or second semester college text either.
If you knew a hell of a lot about the materials in question and had a crib sheet drawn from a book that said something like "Mechanics of Deformable Solids" on the cover, you might get there. But there's a reason why the world's expert on this topic is doing lab testing to determine the forces involved, not dicking around with f=ma and integrating over the distance of extension and crap like that. Unless you're a qualified mechanical engineer (not me, but I know there are some in this discussion, and I hope they agree with me), everybody needs to put away the TI-86 and the Addison Wesley physics book, and just chill out and wait for Largo to publish his findings and explain to this new extendomatic system he thinks we should start using.
Flame away, and my apologies to the people in this discussion that do know their stuff.
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tradklime
Feb 15, 2006, 3:42 PM
Post #53 of 915
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In reply to: I'm asking because you're the one that's spent endless hours on all those wall anchors of varying quality over the years - I haven't but would still like to and am trying to figure out if it's worth it to do all the Chongo/PTPP major construction projects with cordalette powerpoints, etc. or should you just throw in a couple of X's and call it good...
I don't have the experience level to draw from that you are looking for but I'll take a swing anyway...
Because John's tests include a section for climbing rope, the results likely won't directly transfer to the situation you are asking about, however, I'd say that a sliding-x (s) with limiting knots would be better than a cordalette. The amount of force generated in a fall of a few inches is very small. If you want the load to be shared by multiple pieces, you have to include some dynamic equalization.
The next best choice would be a Trango Alpine equalizer. I've been playing with the 3 ft. version and it has some neat properties. Even if you make it static by tying a knot in the middle leg, I think the equalization between the three pieces is better than trying to tie a perfect knot in a cordalette. That said, It does offer efficient equalization without any knots in the system, but intuitively (to me) the extension is a tad more than I'd like of a piece were to fail.
My unsolicited 2 cents
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tradklime
Feb 15, 2006, 3:50 PM
Post #54 of 915
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In reply to: .... Flame away, and my apologies to the people in this discussion that do know their stuff.
Very good point.
I still think discussion of the issue is valuable, even if it is based on conjecture, but we should all be very clear that it is mostly conjecture.
At least I'm willing to admit that on my part.
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dingus
Feb 15, 2006, 4:07 PM
Post #55 of 915
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I will be very interested in the final results as I reckon most of us would. I scraped cordelettes and such after a brief trial period and went back to X's with direct backups. I never bought this whole shock load bullshit, nor did I buy the cordelettes equalization properties.
I went back to my old ways out of convenience coupled with a sense of 'good enough.' Now it turns out that good enough may in fact be better anyway.
Cordelettes have their places. Love em for big walls belays and such. But for free climbing I find them to be a huge inconvenience and totally unnecessary. Just one more piece of bullshit to carry up a climb.
Cheerio
DMT
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vivalargo
Feb 15, 2006, 6:14 PM
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Hey, it's all good--and these questions are really worth answering. Thankfully I have access to questionably the best dude in the US to do all this testing, as well as all the UIAA test tower gadgets, computer analysis and so forth, without which dynamic load testing -- as seen in real world climbing -- would be impossible to conduct. FYI, most testing is slow loading or static loading and that has little to do with real world dynamic falls.
Another thing--don't forget that no matter if you're on a hard (tech cord/webing) or soft (nylon cord/webbing) system, so long as the line is belayed, rope slip at the belay device greatly limits the possiblity of a true "shock load," a term that has never been properly defined. If you have dynamic loading on tech cord/webbing sans belay--watch out folks. Picture a few haul bags connected to an anchor via a spectra sling(s), and have them bouncing around in a huge storm (hard to imagine but it happens)--that could actually bust the biners.
Lastly, we did a few tests to try and determine the degree of loading on a sliding x where one arm blows out and the other arm captures the entire load. The X had limiter knots and only extended, like, six inches. Also the piece that blew out held a good part of the load before blowing out--and this is a VERY important variable. But so far we have found no "load muiltiplication" or anything remotely like a shock load during the resultant "catch" by the remaining piece(s).
This is actually another series of tests that need to be thoroughly conducted--our testing is really to find out the performance differences (how well each system actually equalizes loading over the anchor points) between s cordelette, sliding x, and the "Duo Glide" or "Slider" rigging systems.
I've just about got the thing licked, thanks to the efforts of many experts (testers, statistical professors/climbers, et al, who I will name later) but it will still be a short while before everything is worked out.
An interesting note is that while the sliding x is the clear winner so far as equalization goes, it still had a tendency to be erratic, owing to the x clutching or binding on itself. The solution was simple--use a wide mouthed, anodized biner at the master point, and the loading on 2 points was just about equal (less than 10% difference).
More later . . .
JL
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maldaly
Feb 15, 2006, 7:04 PM
Post #57 of 915
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I'm w/ dingus all the way on this one. Loose the formulas and textbooks and lets figure out what actually happens in a loading situation. Mucho thanx for all the testingf largo. If there were a Mother Theresa award in the climbing industry, you'd deserve it; even if you stretch the morals a bit...
Mal
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dr_monkey
Feb 15, 2006, 8:33 PM
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This thread has been interesting and I am re-evaluating my preferred equalizing method (cordelette.) I used to think that the Alpine equalizer was to specialized a piece of equipment and due to shock loading. Now it is looking much better.
All of this discussion got me thinking though, this may be a little too far off topic, but... What would be the disadvantages of using a very dynamic material for either a cordelette or sliding-x? There must be some glaring problem I am overlooking, otherwise we would all use a length of a super stretchy twin to build anchors, right? Or better yet manufacturers would be making a specific cord or sling with optimal properties for the application. Maybe it would not make a big enough difference within the greater system?
Anyone out there have actual data or knowledge about this?
Cheers,
DRS
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landgolier
Feb 15, 2006, 8:49 PM
Post #59 of 915
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In reply to: This thread has been interesting and I am re-evaluating my preferred equalizing method (cordelette.) I used to think that the Alpine equalizer was to specialized a piece of equipment and due to shock loading. Now it is looking much better. All of this discussion got me thinking though, this may be a little too far off topic, but... What would be the disadvantages of using a very dynamic material for either a cordelette or sliding-x? There must be some glaring problem I am overlooking, otherwise we would all use a length of a super stretchy twin to build anchors, right? Or better yet manufacturers would be making a specific cord or sling with optimal properties for the application. Maybe it would not make a big enough difference within the greater system? Anyone out there have actual data or knowledge about this? Cheers, DRS
Bluewater makes something they call "dynamic prusik" in 6.5, 7, and 8 mils. It's not tested as a single, though, so can't say much is actually known about its properties. Can't hurt I guess.
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johngo
Feb 15, 2006, 10:20 PM
Post #60 of 915
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Largo and friends,
This has been a great thread! I echo the thanks of many here for the work you are doing on your new book, and for sharing some of the results with us. You'll sell a heap of books as soon as they're available. I'm teaching a few anchor classes this spring, and I want to be sure the students are getting the latest. This post has helped a lot. (And yes, the cordelettes on my rack are now catching some suspicious glances . . .)
Be Well,
johnGo
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slcliffdiver
Feb 15, 2006, 10:38 PM
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In reply to: A genuine shock load will only occur in those instances reflected in Duane Raleigh's recent tests for Rock and Ice, say, when someone is tied off to an anchor with a short shank of high tensile cord. He climbs a few feet above the anchor and falls. Here, you have true shock loading, where biners blow apart and anchors rip out because there's no rope slip at the belay device, no stretch in the rope, no human body to absorb loading, et al. JL
A few senerio's with the sliding X (belayer hooked in with sling or such):
Factor two fall a piece fails if it is a hanging belay the belayer falls directly onto the extended no stretch material and is probably accelerated by the tension in climbers rope and energy of falling climber and or possibly the spring force in the rope to climber.
Factor two fall a piece fails if it is a non hanging belay the belayer is probably accelerated by the tension in climbers rope and energy of falling climber and or possibly the spring force in the climbers rope to climber.
Hanging belayer is lifted by climber from a high factor fall and either losses control of the belay (hits something? on the way up) or the top piece fails and drops the belayer onto the anchor.
It's always been my understanding that the belayer is the source of potential shock loading and not the climber.
I skimmed through the posts fast so forgive me if this has been cover and I missed it. I just prefer there not to be "a generalized myth of shock loading" out there until I'm satisfied that these issuses have been adressed. I think I've posted here more than once and agree that a climber will not cause true shock loading it's the belayer. So maybe something worded a little more narrowly. Sorry if I'm missing or miss reading something but I'm short on time for the moment and just am uncomfortable with how I percieve things are being discussed and don't know how many people read then leave without comming back.
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tradklime
Feb 15, 2006, 10:46 PM
Post #62 of 915
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In reply to: A few senerio's with the sliding X (belayer hooked in with sling or such):
Attach yourself with a section of climbing rope, just as most do with a cordalette.
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healyje
Feb 16, 2006, 12:42 AM
Post #63 of 915
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Yet another day of being stupifyingly dense I guess...
So based on all this, if I arrive at some random anchor on WFLT, am I building a cordalette powerpoint ala Chongo/PPTP or should I simply be multi-X'ing it? I'm sure I'm missing volumes here at this point but it still seems like a pretty simple question to me.
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vivalargo
Feb 16, 2006, 1:49 AM
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In reply to: Yet another day of being stupifyingly dense I guess... So based on all this, if I arrive at some random anchor on WFLT, am I building a cordalette powerpoint ala Chongo/PPTP or should I simply be multi-X'ing it? I'm sure I'm missing volumes here at this point but it still seems like a pretty simple question to me.
Okay, say you've just finished the first bolt ladder on the Leaning Tower and come to a two bolt (bomber 3/8 inch SS bolts) anchor. Here are your options: You can certainly go with a cordelette because when the arms of the cordelette are virtually equal (so far as you can get them equal), you get adequate but not great equalization between the two bolts--so if the bolts are good, you should be golden. If you wanted a better ratio of equalization between the bolts, you'd go with the sliding x, and if you wanted better equalization still, you'd clip the materpoint off with a wide mouthed, anodized biner which keeps the x from binding, which it sometimes does.
But say you are on some other wall and get to belay where you have to hand build with nuts and cams placed in two vertical cracks that are close to each other, in which you have two primary placements in both cracks, totaling four placements in all. In this scenario, a cordelette would involve four arms that are all different lengths, a scenario that testing has shown to be a total bust so far as equalization goes. Here, a cordelette isn't even a redundant system, since most all the load will fall on the shortest arm--meaning the cordelette is a backed up, rather than a redundant, system.
The drawback with using the sliding x here is that it can only combine two placements, so you'd have to double up the system with two x's--no big deal, but extra hassle.
There is yet a third system called the Duo Glide that is looking probable as the best of them all--by far, but we still are working out the bugs in this thing since we only stumbled on the idea a few days ago.
If there is any interest in people doing some contrilled field testing of the Duo Glide, I'll post how it works and you guys can help figure out how to dial in the fine points. It so far looks amazing in the figures it's spitting out.
JL
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healyje
Feb 16, 2006, 2:18 AM
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John,
Sorry to be such a nuisance, but that was just what I was looking for! Thanks much and do keep up the good work as it is much appreciated.
Whatever the Duo Glide business is, count me in, I'd love to take a look at whatever you've come up with - particularly anything you appear to be as excited about as this...
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dood
Feb 16, 2006, 2:27 AM
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Very interesting indeed, and I'm looking forward to the final results. While raised on cordolettes, I've used the sliding X in situations where rockfall was a possibility, in an effort to give myself a little more mobility for dodging missiles. Now it is no longer a trade-off of mobility for a stronger anchor.
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slcliffdiver
Feb 16, 2006, 3:33 AM
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In reply to: In reply to: A few senerio's with the sliding X (belayer hooked in with sling or such): Attach yourself with a section of climbing rope, just as most do with a cordalette.
Exactly it's the "most do" part that's troubling.
There are currently some climbers that at least part of the time who hook into the the anchore directly or with static material (which in general I don't like). They are going to be in potentially more trouble if they go from a non extending system to an extending system with out realizing how things work or changing their habits.
Problems when the belayer is hooked to extending system.
Belayer shock loading the system ; tie in with enough rope to absorb most of the shock (more rope than the potential extension).
Belayer loosing control of rope because they lost balance and fell and or hit their tailbone or whatever because of the extension; limit extension watch where you are belaying from etc.
Many things in trad are situation specific. I'm concerned if their is a shift away from the no extension part of sere"ne" their will be potentially new problems for people who don't understand the new factors involved with a potentially extending systems when they've been operating under the principle of no extention for a long time. Specifically the potential for the belayers body to shock load the system. I'm not proposing a specific solutions or changes. I just think it would be wise include information on the potential downsides and precautions that need to be taken with potentially extending systems and I'm hoping that'll be included with a new anchor book if it includes or emphasizes systems that can potentially extend.
But it also disturbs me a bit that many trad climbers don't seem to reallize in general that the belayer can actually shock load the system. Trad climbers tend to be creative out of neccesity sometimes. If you don't understand the principles what you build can potentally be less than ideal. I just wish the trad climbing public at large would be better educated at how shock loading really works. And if the community ends up shifting a bit away from the "no extention" principle it seems like it will become a more important for more people to understand.
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curt
Feb 16, 2006, 3:40 AM
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In reply to: In reply to: I'm just curious if you consider shock loading a "myth" in general. That, along with normal multi-pitch, you don't need to worry about the X shocking in a hauling accident or in a case of a heavy bag slipping off a ledge, or maybe a portaledge getting slammed up and down in a storm. I can't tell whether, from your description of the role of belaying in all this, you mean just climbing as opposed to also including the forces involved with all the other various big wall activities. I'm asking because you're the one that's spent endless hours on all those wall anchors of varying quality over the years - I haven't but would still like to and am trying to figure out if it's worth it to do all the Chongo/PTPP major construction projects with cordalette powerpoints, etc. or should you just throw in a couple of X's and call it good... John and Curt, I guess I'm feeling incredibly stupid and dense on this because I'm not getting it at all. I think I've just been programming for way too many week/days/hours in a row now and am starting to lose it. Couldn't you guys show a little pity, put me out of my misery, and just answer this question for me because I really do want to know the answer?
What has been pointed out in the past is that a cordalette does a fairly poor job of equalizing forces on the various anchor elements. Even in the best case scenario with only two placements (or bolts) a cordalette will not truly equalize force on the two anchor points if the falling force is not exactly in-line with the masterpoint--as it was designed. The only exception to this rule is if the two anchor points are in a vertical line--i.e. one anchor element is directly above the other.
With three or more anchor elements things get much worse and a fall will transfer virtually all of the force of a fall to a single anchor piece--i.e. one anchor piece "sees" nearly 100% of the force on the anchor. Only after that piece fails does the next piece become significantly loaded--again with 100% of the force. So, clearly this is not optimal.
What I believe John is bringing to the party here is some actual data that suggest the failure of a "sliding x" anchor does not result in a huge shock load on the remaining anchor piece--if the other one should happen to fail. Perhaps this is because the two anchor elements in a "sliding x" anchor are at least truly sharing the force of a fall in a meaningful way, when initially loaded.
Curt
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healyje
Feb 16, 2006, 3:54 AM
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Curt,
Thanks for that. I basically got most of that part out of the thread, but couldn't tell in the end what John would suggest I do on arriving at an anchor on a big wall in light of this new data.
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vivalargo
Feb 16, 2006, 4:06 AM
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Okay, here is what we have so far found about so-called shock loading. Because our testing was basically to determine the equalization ratios of the cordelette and the sliding x, the main concern was to determine what happens to the dynamic load if one arm of a sliding x (with limiter knots) should blow out and the system should "extend" a few inches before the other arm holds. We are still doing more tests, but this kind of very minor extension so far looks to be insignificant SO LONG AS THE FALLING CLIMBER IS ON A DYNAMIC NYLON ROPE (THROUGH WHICH THE FORCE IS TRANSMITTED) AND THE ROPE IS BELAYED. If you have a piece of static cord and no belay, any extension/fall is very disruptive on the anchors. That's why a person should never tie into the anchor with a tech cord/web daisy. A daisy made out of anything but nylon is a serious liability because it can cause shock loading (as seen in the recent Rock and Ice expose). You ALWAYS tie into the anchor master point with the climbing rope. NO exceptions.
I can get even more technical if need be, but ain't that clear enough? Bear in mind that the above is basically only possible if the belay anchor is forced to take the entire loading--normal with bringing up a second, but here the forces are low, and if an arm of your tigging system blows from belaying a sceond, your anchor is not nearly "good enough."
JL
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desertclimber
Feb 16, 2006, 5:31 AM
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VivaLargo, have you tested the "sliding x" with a three-point setup?
We've always used sliding x's, but on occasion when the anchor is three points: Instead of using two separate x's (One for two pieces, then another between that x and the third piece) a sliding x with three pieces was built. Same principle, just a slightly different setup.
Curious, as I had not seen that mentioned anywhere in the thread...
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roy_hinkley_jr
Feb 16, 2006, 5:46 AM
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In reply to: If you wanted a better ratio of equalization between the bolts, you'd go with the sliding x, and if you wanted better equalization still, you'd clip the materpoint off with a wide mouthed, anodized biner which keeps the x from binding, which it sometimes does.
How much does the choice of sling material or biner affect this equalization? For example, does using a sling of plain ol' nylon supertape, one with a low ratio of spectra/nylon (12mm, though even weave and amount of fuzz could be factors), or one that's nearly all spectra (6-8 mm) matter in terms of friction? Is biner diameter (10mm vs 12 mm) as important as shape and anodizing? Have you tried the Trango Equalizer rig? Definitely post info on the Duo Glide!
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patto
Feb 16, 2006, 9:42 AM
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In reply to: this energy is absorbed by the system (rope, friction device, friction with biners and rock, etc)
Rock effectively absorbs no energy as the rock generally does not deform.
In reply to: What I was speaking of, was that any piece of pro that breaks will absorb some amount of energy.
Breaking pro absorbs only a very small amount of energy, as the distance of deformation is small. Certainly setting up a deliberately un-bomber piece to act 'like a screamer' is foolhardy.
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patto
Feb 16, 2006, 9:50 AM
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In reply to: I want to get out in front of this one before any more foolishness goes down, so excuse me if this is a bit terse, but... The equations to calculate this crap in a meaningful way aren't in a high school physics text, and they probably aren't in a first or second semester college text either. If you knew a hell of a lot about the materials in question and had a crib sheet drawn from a book that said something like "Mechanics of Deformable Solids" on the cover, you might get there. But there's a reason why the world's expert on this topic is doing lab testing to determine the forces involved, not dicking around with f=ma and integrating over the distance of extension and crap like that. Unless you're a qualified mechanical engineer (not me, but I know there are some in this discussion, and I hope they agree with me), everybody needs to put away the TI-86 and the Addison Wesley physics book, and just chill out and wait for Largo to publish his findings and explain to this new extendomatic system he thinks we should start using. Flame away, and my apologies to the people in this discussion that do know their stuff.
It is certainly possible to accomplish alot with basic F=MA physics. F=MA physics is indisputable as long as the correct assumptions are used. Certainly there is alot we cannot answer without real world testing. For example I cannot begin to tell you using basic physics the real world load sharing of 'equalised' anchors compared to the sliding-x. For that I think Largo's testing is fantasic.
However I can tell you that the so called 'shock loading' is negligable during extension of a sliding-x when there is no mass at the belay. (The weight of a biner and a belay device is negligable) I can tell you this because there is nothing to carrying that energy to produce the 'shock load'. That is undeniable physics.
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norushnomore
Feb 16, 2006, 10:18 AM
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Looks like Alpine Eq dude is getting vindicated here.
He pointed out few years ago these two issues:
1. Cordelette is very likely to put all the load on the shortest arm
2. Sliding x binds easily
Thus his invention with the ring to address both of the above.
So much for bashing him here
JL, please post the details of the Duo Glide, there is definitely an interest.
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