Discussion Topic |
|
This thread has been locked |
WBraun
climber
|
|
|
Nov 28, 2008 - 05:42pm PT
|
That's all I've ever used for a belay device since it first came out.
A Gri-Gri.
I don't know why everyone is so scared of this device.
I works perfect. I hate all those stupid ATC type units. Blah!
|
|
healyje
Trad climber
Portland, Oregon
|
|
|
Nov 28, 2008 - 06:48pm PT
|
Well, Werner, we simply disagree, I personally don't care for grigris at all and I do own two of them...
|
|
tito
climber
|
|
|
Nov 29, 2008 - 12:07am PT
|
JL,
Today, I was looking over the test results in your latest Climbing Anchors book, and I have to say, the way you present the results of the tests to the reader makes them difficult to evaluate. You state the difference in force that each leg of the anchor felt after subjecting the anchor to a factor 1 fall, e.g. the left side felt 1 kN less than the right side. Is that significant? You never say what the total force was on the anchor, so it is difficult to interpret those numbers. What I want to know as a reader is what percentage of force went to each leg, e.g. the left side felt 60% of the force and the right side felt 40% of the force, so that I can determine how good the equalization was.
It would also be nice to know the actual force felt by each arm, so that we could see how much of the force friction dissipated. For instance, if one leg of an equalette felt 4 kN and the other felt 3 kN, then we would know that 1kN was dissipated by friction--which would give us great insight into how big a role friction actually plays when a rope runs over a biner at the power point.
Finally, the graph on p. 189, which purports to show the results of your tests on each type of anchor using some bizarre stick-connected-to-bar graphs, has no accompanying explanation. What do the shaded rectangles and the numerous vertical lines mean? I am pretty sure I know what some of the lines mean, but for others I have no idea.
Therefore:
1) If you could post answers to any of those questions here, I would be most grateful, and I will pencil them into the margin of my book.
2) I suggest you present the results of the raw data in a more meaningful way in your new book.
Sorry for going off topic, but I thought JL would be most likely to see these comments here.
|
|
Sir loin of leisure...
Trad climber
X
|
|
|
Nov 29, 2008 - 12:08am PT
|
ALL BOW BEFORE THE SAGE WISDOM OF WERNER....gri gri,s rule...
|
|
Karl Baba
Trad climber
Yosemite, Ca
|
|
|
Nov 29, 2008 - 12:38am PT
|
John wrote
"One assumption which is pretty unrealistic is that the clip is made to the power point of the anchor. Usually the leader clips the topmost piece, or one bolt if the anchor is bolted. So the (usually higher) force in the "clip" scenario is being applied to the anchor in a very un-equalized way.
JohnR"
Here's my take, if the leader clips the topmost piece, or one bolt if the anchor is bolted, it's usually because the anchor is bomber. If the anchor is not bomber, the leader is more likely to clip the powerpoint (or just say his prayers) Of course the leader will try to get a good piece in asap but if a good piece was very close, why is the belayer using a crappy anchor? (out of rope?)
There's always so many factors.
as for those scenarios, I can see how your scenario #1 john may seem the same to my questioned scenario but I bet we'd be shocked to see how different the forces on the anchor would be between falling right on a gri-gri fastened to the anchor and falling on the belayer. Human meat is like a big screamer. We have all kinds of give in us, and of course, there is the harness and rope tie in to consider.
PEace
Karl
|
|
Largo
Sport climber
Venice, Ca
|
|
|
Nov 29, 2008 - 12:46am PT
|
The test results, figures and graphs were worked up by two nationally recognized statistics profs, Larry Hamilton and Callie Rennisson. The whole point of the thing was not be a raw data source but for two experts to review the data, crunch the numbers and for the book to present provisional rules of thumb. Maybe Wottles can provide you with the actual figures if you could provide him good enough reason to dig them up.
JL
|
|
tito
climber
|
|
|
Nov 29, 2008 - 01:01am PT
|
> The whole point of the thing was not be a raw data source but ... for
> the book to present provisional rules of thumb.
Then it doesn't make much sense to state what the actual difference in forces between the two legs was. All most readers care about is how well the tested anchors distributed the forces. Was it 60%-40%? 70%-30%? When you state that the difference in force between the two legs of a tested anchor was 2 kN, how is the reader to know whether that is closer to 50%-50% or 70%-30%?
That is sort of like a knot book saying that a knot weakens the cord by 3 kN instead of 25%(which is what they actually do).
My post gives you some reader feedback for the new edition. You can take it or leave it.
|
|
nick d
Trad climber
nm
|
|
|
Nov 29, 2008 - 01:26am PT
|
Who cares what Tito thinks, I'm waiting for Jermaine to chime in.
|
|
JohnRoe
Trad climber
State College, PA
|
|
|
Nov 29, 2008 - 08:09am PT
|
Karl wrote
"I bet we'd be shocked to see how different the forces on the anchor would be between falling right on a gri-gri fastened to the anchor and falling on the belayer. Human meat is like a big screamer. We have all kinds of give in us, and of course, there is the harness and rope tie in to consider."
I agree. Another unrealistic thing about these models is to see the climbers as point masses. They are not even rigid bodies, let alone point masses, at the scale of the effects that we're considering. We are also neglecting rope slippage (dynamic belay) if an ATC type device is used.
I bet though that, even if one incorporated all these effects into a more realistic model, the overall pattern of the numbers would still be the same... after a comparatively short distance, clipping the anchor loads it more in a fall than not clipping. (But the belayer is loaded much more in the factor 2 situation.)
Peace
JohnR
|
|
sibylle
Trad climber
On the road again!
|
|
|
Nov 29, 2008 - 10:21am PT
|
Someone said:
"Personally I would never consider clipping a belay device directly to a fixed anchor."
and jstan said:
"Amen, brother! In general I consider this, a commercial activity at best, and one that breeds entirely the wrong long-term 'sensibilities'; at worst, I think it's slovenly in a way that divorces you from any number of sensory pathways to knowing what is going on with your partner. I only even redirect under rare circumstances."
I've climbed in Europe. Almost all European guides and climbers clip the belay device directly into the anchor and were shocked to see me clip my device to my harness. One of them said,
"Do you still do that? Haven't you learned modern techniques?"
I've been yelled at by climbers who worked as guides in Europe for belaying incorrectly when I clip the device to my harness.
So are most Europeans belaying incorrectly? Or are Americans? Or is it a mattter of style, taste, and judgment?
I clip the device to a GOOD anchor when belaying a heavy second. Once recently, I could not easily do so and had to hold someone who weighed 60 or 70 pounds more than me on my harness for a long while and could hardly breathe.
What I mentioned earlier - what if a climber that weighs 100 to 120 pounds belays a climber who weighs 180 to 220 pounds? Have any of you caught a leader who weighed almost one hundred pounds more than you?
I have. It sucks no matter how you belay them.
|
|
Karl Baba
Trad climber
Yosemite, Ca
|
|
|
Nov 29, 2008 - 12:35pm PT
|
It's not just europe. 10 years ago I took the YMS clinic for prospective guides and the AMGA certified leader (actually it president at one time) taught that his favorite method of bringing up the second was a gri-gri on the powerpoint of a cordalette anchor.
I tried it out and found it to be way better than anything I'd done before. You still get plenty of "feel" for the climber (like fishing) if you use your hands on both sides of the device when bringing up the second. It's so easy you get a better cool down at the belay and makes it easy to manage the rope for the next lead.
Don't knock it if you ain't tried it. The AMGA and the euro scene are not a bunch of reckless dummies.
Peace
Karl
|
|
TradIsGood
Chalkless climber
the Gunks end of the country
|
|
|
Nov 29, 2008 - 12:57pm PT
|
There is a difference between bringing up a second off the power point and catching a fall on the power point.
With the GriGri, or any autolocking device, the rope does not slip. Effectively the coefficient of friction is infinite. So the load on the power point is just the weight of the second. If the second falls, the fall factor is (or should be) much lower than one. Thus the load on the anchor is minimal.
If one were to belay a leader off the power point with such a device, it would reduce the load similarly, since there is no "pulley" in this system. I have not seen this done in practice. I guess though, it might serve to limit the anchor load to a factor 2. I am not familiar enough with the spec's of the gri-gri, though to comment with any conviction on that.
I have used the reverso to belay off the power point when I am not concerned that I might have to lower the second. When that is a concern I often will belay with a Munter hitch. (This has a slightly higher load, since some tension is required on the tail.)
|
|
jstan
climber
|
|
|
Nov 29, 2008 - 01:14pm PT
|
Sibylle:
The two attributions above are reversed.
If someone criticizes another's technique but cannot give a persuasive argument you know right away what to do. To my mind belaying directly off an anchor with a device fails on two counts. First it materially increases shock on the entire system. A system you personally did not build so you do not have detailed knowledge of its shortcomings. Secondly if the anchor does fail you may entirely lose the belay. I have never belayed off a seat harness. If I were using a seat harness I would probably belay off the waist loop since that is what I know. If both the tie-in and the belay both come off the crotch loop you better have a loop of 1" tubular directly backing that up to your waist loop. Being retarded I consider even the waist loop on a harness to be too complicated to merit complete trust. Best thing to do would be to use a swami under the harness if you really need a harness and tie them together as a backup for each other.
Things are never what they seem. Here I need only refer to T.M. Herbert's story of the waist loop that had a piece of masking tape on it.
The problem you raise about climbers of very different weights has not gotten the attention it deserves. On an extended climb I would be inclined to drag along an extra rope when this is a factor. Might turn out to be necessary. And when you can see a worrisome scenario coming up it always helps to let the leader know they have a problem with which to deal.
Long time ago I accidently found myself above one of those ceilings in Eldorado belaying about a 180# French climber on doubled nines. Somehow he thought one of the ropes was impeding him so he threw one off leaving me holding him on a single nine and looking at an 80 foot lower in free space - over my gym shorts. Dead weight with no friction in the system is very unforgiving. Fortunately while he was occupied throwing off the rope I had been busily building some friction into the belay.
This kind of thing is completely missing from indoor climbing by the numbers. Frankly I don't know how a person can stay interested in that stuff. But there are a lot of things I don't know.
|
|
JohnRoe
Trad climber
State College, PA
|
|
|
Nov 29, 2008 - 01:37pm PT
|
Question for rgold or another modeler out there:
After one of Karl's posts above, I got interested in the question of what happens in a factor 2 fall when the belayer is connected to the anchor by a dynamic tether (the climbing rope) rather than statically.
The conventional wisdom is that the dynamic tether will reduce the peak load on the system. That is certainly what I expected to find.
But the model shows something quite different: the dynamic tether increases the peak anchor load, from 7.6kN to 10.1kN in the standard example (4m rope out, 1m tether).
What happens is that the fall gets the belayer moving as well as the leader, and the anchor then has to stop both of them!
OK, questions: Has anyone else tried to model this effect? Do you believe that it is real?
If it is, then under most circumstances the extra force it produces on the anchor in the factor 2 situation (scenario 1) is pretty close to the "pulley effect" force in scenario 2 (anchor clipped, belayer static). This leaves scenario 3 (anchor clipped, belayer free to be pulled upwards) as the theoretical winner.
Standard anti-geek disclaimers apply.
|
|
rgold
Trad climber
Poughkeepsie, NY
|
|
|
Topic Author's Reply - Nov 29, 2008 - 01:42pm PT
|
Sibylle (and others),
The use of anchors in Europe for direct belays is, to some extend, a byproduct of their more extensive array of bolted stances, is it not?
I don't think it will be long before the European example and the pressures exerted in this country by climbers less and less competent in the trad arts and more and more enamored of modern conveniences will lead to very extensive bolting of trad anchors here too. It has certainly already started, and when it becomes more or less universal, this discussion will be moot.
In the meantime, here, for whatever it is worth, is my approach to the anchor-clipping dilemmas. YMMV.
I'd like to begin with the assumption that the anchor is NOT "bombproof." The definition of a bombproof anchor is you can do whatever you want. Let's talk about the real world, not about the very occasional crap anchor that we also sometimes have to accept, but about the greyer spectrum of anchors that are probably ok but, if we are honest with ourselves, are not "bombproof." I must say that I mistrust the judgement of people, regardless of their experience, who insist they don't have to belay off such grey cases say, 5-10% of the time. Every anchor bombproof, pitch after pitch, year after year? I don't mean to be offensive, but I'd say, no way. Neither common sense nor statistics suggest this could be true.
If you do not accept that some of the time you are belaying off anchors that may not be bombproof, read no further. Your problems are over, one way or another. Go ahead an clip whatever. But if you are prepared to admit this particular view of reality, then I think you'll also agree, perhaps after some quiet reflection on how many of your anchors have been put to any kind of severe test, that you may not really be so good at judging which of those grey cases are worse and which are better. After fifty years of placing anchors, from soft iron through cams, tricams, brassies, and ball nuts, this is at least my conclusion for myself. And the only person I have ever met who I think might be a whole lot better than me is John Stannard, because he is the only person I know of personally who has placed gear, made an evaluation, and then tested the placement to see how his judgements corresponded to reality. Anyone else like that out there, I defer to your superior judgement and your wisdom in acquiring it.
So, if you haven't stopped reading in disgust or outrage, then you are in a position to admit that a certain fraction, hopefully quite small, of your anchors may not be all that great, and, sadly, that you may not be omnsicient when it comes to perceiving which ones are better and which worse. It gives me absolutely no pleasure to support this position by noting that in virtually all the cases I have heard about in which parties have been swept from the cliff because of anchor failure, the climbers involved have been experienced, and their experience was not good enough.
All of this leads me to the basic view that one should, as much as possible, arrange to load at least those grey-spectrum anchors as little as possible, applying a broad definition of "greyness" in view of our fallibility as judges of anchor integrity where huge forces are involved. The result is, as practical matter, I rarely clip any portion of a trad anchor when leading.
However, I do, in a certain sense, believe in belaying off the anchor. Many of us here have caught humongous falls with hip belays, and we know that with the right approach and appropriate levels of attention, it is an unpleasant but not catastrophic experience. But anyone with an appreciation for the possible forces, and anyone who as experienced them first-hand, cannot be utterly sanguine about the potential for belayer injury and/or loss of control. I think the anchor needs to play a role, and not as an afterthought after the belayer has collapsed.
So here's what I do, for upper and leader belays. I use a modified harness belay that is, in practice, only partially on the harness. I always tie into the anchor with the rope---what I am about to describe would be compromised if I used low-stretch sling or cord. My tie-in is typically snug, with at most a very small amount of slack; "play" would be a better word. Doing this fast and right requires clove hitches, in my opinion. I am not worried about their integrity.
Now here's the critical detail: I clip my belay device into both the harness belay loop AND the tie-in knot loop of my anchor rope. This means that loads to the belay device are transmitted to the anchor directly, rather than loading up the belayer's harness first. However, since the anchor rope stretches, the belayer has some opportunity, in the case of the high loads of a factor-two fall, to resist with appropriate stancing, to use Joe's term, and thereby reduce to some extent the total load to the anchor. Since the connection is direct, the increase in load guaranteed (sorry, Karl) by the pulley effect after the break-even point is not a consideration.
This is what I do most of the time, because I think it will result in the lowest anchor loads consistent with belayer safety. Whether, in reality, my anchors need this tender consideration is not much of a factor in my decision, because I do not pretend to know for sure.
When this system is used for upper belays, the stretch in the anchor rope is minimal and you basically have a belay off the anchor. There is absolutely no discomfort in holding a fallen second; I've done this, for example, while they prussicked up five or six feet to clear an overang. There's no pain because they are hanging on the anchor, not on you.
But, unlike the modern direct belay off the anchor, this one has some extra load-reducing capability if your communications screw up, your second accumulates some slack and then takes a leader fall. Because then, the stretch in the anchor tie-in and the connection to the harness gives the belayer the opportunity to resist, given appropriate stancing.
It should be clear that there is nothing time-consuming or at all complicated about this; there is in fact no difference in set-up time from the usual approaches. It does mean, for upper belays, that the belayer has to be actively engaged in the belaying process, rather than eating snacks, applying sunscreen, snapping photos using both hands, practicing tai-chi, and other lapses of attention now viewed as both acceptable and desirable because of locking anchor belays.
|
|
nick d
Trad climber
nm
|
|
|
Nov 29, 2008 - 02:03pm PT
|
John R., I think there is a mistake in your model. If there is an increase in the load on the anchor it should only be the weight of the belayer hanging on it. Your numbers sound like the belayer is falling with the leader and both their weights are impacting the anchor. This should not be the case.
I don't see any way that a dynamic rope can increase the load on the anchor. Am I seeing it wrong?
|
|
rgold
Trad climber
Poughkeepsie, NY
|
|
|
Topic Author's Reply - Nov 29, 2008 - 02:08pm PT
|
John, an excellent point. I have thought about it but hadn't got around to the modelling. It does seem possible that a falling belayer would make clipping the anchor at least equivalent to the factor-2 choice in terms of anchor load. One of the advantages and reasons for the tie-in method I just described above is that it passes the load directly to the anchor rather than through the belayer, and so either eliminates or at least mitigates the effect you suggest, depending on how much the belayer tie-in stretches.
I believe, as much as possible, in the belayer adopting good old-fashioned braced stances, and suspect that this can further mitigate the peak loading effects of a pair of coupled harmonic oscillators. I'm pretty sure bracng played a significant role in the one factor-two fall I've had to hold; I was well-braced yet still driven to my knees by the impact. My quads were sore as hell the next day, indicating a significant level of resistance. The anchor, by the way, consisted of a single piece, and as you can tell, it held.
By the way, I think the anchor loading results of connecting the belayer to the anchor with low-stretch slings or cord would be much more substantial; that stuff has significantly higher "modulus."
I've had extensive experience, years ago, catching practice high fall-factor falls with weights. That experience convinces me that, in most circumstances, the belayer will be pulled violently up to the clipped anchor if they are not anchored down, with results no more predictable than what may happen to a belayer stressed by a factor-two fall. But the peak loading shouldn't occur until the belayer has hit the anchor, at which point there is no longer any pulley effect.
|
|
Karl Baba
Trad climber
Yosemite, Ca
|
|
|
Nov 29, 2008 - 02:11pm PT
|
RGold wrote
"Now here's the critical detail: I clip my belay device into both the harness belay loop AND the tie-in knot loop of my anchor rope. This means that loads to the belay device are transmitted to the anchor directly, rather than loading up the belayer's harness first. However, since the anchor rope stretches, the belayer has some opportunity, in the case of the high loads of a factor-two fall, to resist with appropriate stancing, to use Joe's term, and thereby reduce to some extent the total load to the anchor. Since the connection is direct, the increase in load guaranteed (sorry, Karl) by the pulley effect after the break-even point is not a consideration."
You might want to review Jroe's last post. It seems that your technique is the worst of both worlds to some degree. In a big factor two fall, the anchor is going to have to hold you and the leader, and you still have the disadvantage of being pulled down.
In reality, I'm sure it's likely that some mitigating factors will ameliorate this issue but it does for the other scenarios as well, which brings me back to my practicality based view that whatever helps you catch the leader in any scenario without risking losing the belay is safer than worrying about the whole anchor pulling (since that is amazingly rare where I climb)
Now I do want to note, since some have missed it, that I only belay directly off the anchor using a gri-gri, to bring up the second. I've aid climbed enough to have years and years of experience to know my anchors are always going to be good enough for those forces (there may be a handful of times I didn't do it because of a sub-optimal anchor)
A not-insignificant advantage of the gri-gri belay of the second is this. If there is a spray of rockfall from above (and this happens!) It would be possible for the belayer to fall and the belayer to get hit by rocks at the same time. With the gri-gri belay, the second still gets caught. With a regular device or hip belay, he could be dropped easily. This scenario is probably as likely as a seemingly good anchor failing in some of the discussions we've had above.
on another note, in lead situations, where I'm belaying off my harness.
To me, a real safety factor is putting a little or a lot of my weight in my harness by somewhat hanging on the anchor. That way, if the leader falls, I'm not knocked off my feet as easily or slammed into the wall, where I might let go!
peace
Karl
|
|
JohnRoe
Trad climber
State College, PA
|
|
|
Nov 29, 2008 - 02:13pm PT
|
nickd
Here's what the model says: Think about the moment when the falling leader comes taut on the rope. The belayer (hanging) has to develop the force to stop the leader. This force is transmitted to the anchor through the belay tether. The force in the belay tether makes it stretch (because it is assumed to be dynamic). So, the belayer starts moving downwards. Now the belayer and the leader are both moving down and they both have to be stopped...
See "systems of second order ordinary differential equations" in a calculus text...
The question is whether in reality there is so much damping in the system that this is just irrelevant theorizing.
|
|
Karl Baba
Trad climber
Yosemite, Ca
|
|
|
Nov 29, 2008 - 02:18pm PT
|
THere are so many way of seeing this and so many factors involved, I just think it would be a great magazine article or a serious contribution post if some of you geeks and those with access to testing devices (maybe get sponsored by gear makers) set up some scenarios at a crag and tested various setups and got real world numbers.
Seeing how theory and practice match up in climbing would give us a baseline to see how useful the theory is
Peace
Karl
|
|
|
SuperTopo on the Web
|
Let us know!