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Cwm
Trad climber
East
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Topic Author's Original Post - Aug 4, 2013 - 01:55pm PT
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This article on fall factors from Beal has some interesting data. Their point is to show that the ropes impact force is a critical component in how much force gets put on the top piece of protection. Im assuming the data is valid, though it also serves their marketing, so Id like to know more.
What caught my eye, however, is that in the four examples they give the differences in impact force on the last runner between the classic dynamic belay and the autolock device belay arent that largeat least not as large as I would have expected. Maybe I am reading it wrong, but it makes me wonder if it would be safer to just use an autolock?
Article: http://www.beal-pro.com/anglais/facteurchute.php
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Dr. Christ
Mountain climber
State of Mine
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in the four examples they give the differences in impact force on the last runner between the classic dynamic belay and the autolock device belay arent that largeat least not as large as I would have expected.
hmm, that's about what I would have expected... 4-6 kN larger for the autolock. Seems significant when biners are what, 8kN cross gate and I don't know how to place gear so it only holds ~2 kN. The last example is showing that the high angle between pieces sucks, regardless of the belay technique.
I assume the autolock belay is without the now standard belayer jump.
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johnboy
Trad climber
Can't get here from there
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An assisted locking belay device does have some slip to it providing a somewhat dynamic belay.
I don't know what an auto locking belay device is.
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the Fet
climber
Tu-Tok-A-Nu-La
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The last example is showing that the high angle between pieces sucks, regardless of the belay technique.
Yes. Rope drag really gives you a feel for how quickly that friction can add up.
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Reeotch
Trad climber
4 Corners Area
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There are a lot of situations, such as overhangs and traverses, where the last thing you want to do is lock off the belay immediately. You can cause real harm to the leader by doing so.
Weather to lock off, pay out (dynamic), or reel in rope as fast as you can totally depends on the individual situation. Making blanket generalizations about belaying (or any other technical aspect of climbing)is a dangerous way of not thinking.
What is needed is at least a basic understanding of the principles involved. A good belayer is constantly assessing the situation and adjusting their plan accordingly.
Too many lazy inattentive belayers out there. Belaying is an art and a science. Don't forget you are holding someone else's life in your hands! Boredom can be deadly.
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Ihateplastic
Trad climber
It ain't El Cap, Oregon
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For me, this actually begs another question I have been pondering. In days of yore we all belayed around our hips. Caught some nice ones that way. Then came belay plates and finally expensive devices that let you nap while belaying on walls.
But... Let's just say some of the younger climbers and/or sport climbers found themselves on a longer route and their $80 belay device got dropped. Would they know HOW to PROPERLY do a hip belay? (or is it an hip belay? Oh bother!)
And would you feel safe leading a pitch knowing someone trained on technology was now relying on something they read about in history books?
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Cwm
Trad climber
East
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Topic Author's Reply - Aug 4, 2013 - 03:44pm PT
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hmm, that's about what I would have expected... 4-6 kN larger for the autolock ...
I was only looking at the Beal rope data (blue histogram), as it is the "low impact force" rope they were studying. In Example 1 (no friction) the dynamic belay created 5.6 kN and the autolock device generated 8.85 kN for a difference of 3.25 kN. This was the biggest difference. Ex 2 was 5.1 vs 7.0, difference = 1.9 kN; Ex 3 was 6.5 vs 7.5, difference = 1.0 kN and Ex 4 was 7.5 vs 8.35, difference = 0.85. The last example is the overhang, and it has the smallest difference. I expected overall larger differences. Again, I could be reading this wrong, but it seems like as long as there is a little friction (what they call rub points) in the system, the differences range from less than 1 to about 2 kN.
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johnboy
Trad climber
Can't get here from there
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I'd use a munter before I'd use a hip belay depending on the circumstances.
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Dr. Christ
Mountain climber
State of Mine
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Am I reading that graph correctly? Are the number you mention for a 7.2mm and the numbers I mentioned for a 12mm?
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Cwm
Trad climber
East
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Topic Author's Reply - Aug 4, 2013 - 04:42pm PT
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Am I reading that graph correctly? Are the number you mention for a 7.2mm and the numbers I mentioned for a 12mm?
Dr. C., It is confusing, isn't it? You are right, my numbers are from the 7.2, but I don't believe it is referring to millimeters. I think those numbers refer to the rope's impact force. Beal's point is that ropes made with lower impact force generate much lower forces on the top sling in a lead than ropes made with a higher impact force (such as 12 kN). They say that all their single ropes (with one or two exceptions) are designed to have impact forces of around 7 kN, so that's where 7.2 probably comes from. And then, as I looked closer at the data, there weren't big differences in belay methods, which surprised me.
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Dr. Christ
Mountain climber
State of Mine
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I just had to zoom in! Stoopid eyes.
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ruppell
climber
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I think the graphs are all showing the same. Harder forces with an autoblock. Makes sense. How much harder though is what caught my eye. For there 9mm data using the first graph only. Which I believe represents a full without any friction in the system caused by rubbing(ie steep). The difference is over 50%. Doesn't seem right but i'll go with the study that was posted. If that is really the case I'm throwing away my Sum Fader right now.
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rgold
Trad climber
Poughkeepsie, NY
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A few things to consider:
(1) Remember that these are theoretical calculations, although the work by the CAI that went into its construction is impressive, nothing like what we see in this country. What we don't seem to have is any kind of variational range for the results, which makes it much harder to evaluate the comparisons.
(2) Both the pictures and the time of the studies indicate that relatively low-friction devices were used for the dynamic belays. More recent devices with notched grooves have significantly higher holding powers, which would suggest that the differences in the graphs would now be less.
(3) Those lower loads are the result of rope slipping through the belay device. My experience, both personal and anecdotal, is that most climbing falls are held without the rope slipping significantly or at all. For those falls, which seem likely to be a substantial majority of the falls, there is no reason to expect a significant difference between assisted locking devices and ATC-style devices.
(4) For fall/protection-system combinations that produce enough load to force rope slippage through the device, there are other potential problems that need to be balanced against the lower anchor loads that slippage achieves. The belayer may get severe rope burns and could lose control of the belay, and the leader falls farther and could hit something.
(5) The numbers at the base of the graph are NOT rope diameters, they are the UIAA impact ratings, in kN, for the ropes. But rope diameter plays a role too, because thinner ropes run through ATC-type devices more easily and can be much harder to control during a fall. It seems to me that at some point this will tip the scale decisively in favor of the assisted locking devices, though one cannot say the evidence is in.
(6) There are now many assisted-locking devices that allow the belayer to choose whether the belay will be dynamic or autolocking. The most convenient one of these is the Climbing Technology Alpine Up, which requires the device carabiner be moved from a slot to an adjacent hole. Other devices, like the Mammut Smart Alpine and the Edelrid Mega Jul, have to be unthreaded and reversed, but may have other advantages, such as lower weight and cost.
(7) As far as I know, we don't have slippage figures for the new crop of assisted-locking devices. The figure I've heard for the Grigri is 7 kN. If the assisted lockers slip at lower values, perhaps ejecting some slack under tension before fully locking, then they would post lower top-piece loads than the Grigri.
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JimT
climber
Munich
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Well yes and no, the values given for rope slip (and all the testing) are for a no-braking hand situation so donīt reflect the way the devices are intended to be used. As the title says semi-automatic isnīt automatic or in English terms braking assist isnīt auto-locking. What the slip values for normal belaying are isnīt given and for some devices isnīt known and hasnīt been tested.
The error rate article was unusually poor for the DAV but then thatīs what you get when you send a couple of students to observe climbers in the gym with a set of preconceptions. Exactly how they decided who to observe is not clear and how the gathered the data even less (for example did they actually measure the 1.5m from the wall?
The commonest "serious error" was failing to do a complete partner check including a safety knot in the rope end something Iīd fail on everytime and 88% of the people observed as well which suggests this is no longer an error but standard practice. Other common failures are standing too far from the wall, belaying someone more than 1.3 times the belayer weight, hand too near the device and so on, all of which are far too subjective to belong in a worthwhile study. Personally I thought the article and itīs conclusions was worthless.
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nopantsben
climber
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the beal info looks like bogus to me.
a bunch of constants that fell from the sky, no error bars or how many times their experiments were done, the results don't have any sort of variational range given with them .....
i can imagine that their conclusions are correct, but this is not exactly a scientific paper and thus hard to really interprete without more data and info.
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JimT
climber
Munich
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so would you say theres any relation towards the "slippage" of the device in "normal" usage ... one thing that stands out is the "slip" on the smart, and the DAV numbers on it .. and how mammut claims that it reduce the impact
from personal experience i can indeed say, anecdotally anyways, that there is definitely initial slippage on whippers ... and even raps ... especially with slick supple ropes
i think in the context of this thread were talking about slippage in terms of the top piece
No, I wouldnīt take the values of slip given in the article as relating to the values you get in normal use. Clearly a Click-Up that hasnīt been activated isnīt normal for example and we need to know the force multiplication for the devices to know what happens in normal life.
Itīs also an awkward fact that two plates with identical force multipication can give differing forces on the top anchor which rather throws a spanner in the works. The way the plate or device initially works on the rope before slip starts seems to have a greater influence on the final impact force as the maximum force from the device doesnīt coincide with the maximum force on the top piece when you look at the time plot.
The difference between the various types of belay device at the top anchor isnīt as great as the differences in the plates themselves especially when a live belayer is used as their movement takes the peak load down considerably.
The failure article is difficult because they donīt actually tell us what the failures are, only give an example for each category. Some of the examples they give in passing are things that I would have trouble quantifying, how far away from the wall is dangerous for example. Iīm qualified to teach in German climbing walls and I donīt know, certainly I donīt teach anyone the moment you are more than 1.5m away it is instant death!
Without knowing a lot more about how they selected, observed and the criteria they used itīs useless and to be honest itīs nothing that interests me since I donīt visit DAV climbing walls which are typically full of the sort of climbers I tend to avoid!
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rgold
Trad climber
Poughkeepsie, NY
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Thanks Jim and Bear for the "added value."
One of the things that seems possible is that the variation in impact loads from a single belayer catching multiple falls with the same device is equal to or even greater than the variation between devices. Perhaps then the advantage of assisted locking devices is that they cut down on the variation in anchor loads attributed to belayer activity. So in some sense, you have a better idea of what you can expect to get from the assisted locking belay, and you are perhaps protected from the extremes of belayer malfunction. (Lots of qualifiers here in view of the level of ignorance I'm speaking from...)
I don't think the current state of knowledge makes a clear case for ATC-type devices vs assisted locking devices when it comes to anchor loads, and for thin ropes, with our current state of knowledge, I think the assisted-locking devices come out ahead, although not decisively so.
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Cwm
Trad climber
East
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Topic Author's Reply - Aug 5, 2013 - 07:20pm PT
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I appreciate the added value, too. Good discussion here. Thanks.
So in some sense, you have a better idea of what you can expect to get from the assisted locking belay, and you are perhaps protected from the extremes of belayer malfunction. (Lots of qualifiers here in view of the level of ignorance I'm speaking from...)
The more I think about it, the more I am beginning to think in this way, as well. In a simplified way, I am thinking that the question comes down to where the greater odds of risk lie: with belayer error or excessive load on the high piece. Bear makes a point I resonate to: " i cant depend on dynamic catches, especially where the rope doesnt have a clean run." Even with a clean run, I can have doubts about the belay. Belaying is a skill, and skills need to be practiced. How often do we practice catching hard falls?
The cluster at Air Guitar is the kind of thing I worry about. Probably more to do with sketchy pro placement and maybe an inelastic rope, but I cringed when I read that the belayer grabbed the live end of the rope and became ensnared in it. To be fair, it seems that in this case an autolocking device probably wouldn't have made any difference, but my heart still sank in reading that.
My take-away from this so far is that climbing with a low-impact force rope and probably a pair of half ropes along with an autolocking device like the Smart alpine or Alpine Up seems to make good sense. It can help reduce belayer risk and reduce impact force on the top piece. Then, being careful about placing protection (it goes without saying, right?) and placing two pieces before the crux or a run out can help to further reduce the chances of blowing out protection since there is slightly more load with the autolock.
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Cwm
Trad climber
East
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Topic Author's Reply - Aug 6, 2013 - 05:02pm PT
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^^^^^^^ Helpful comments for more to consider. Thanks, mate.
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NutAgain!
Trad climber
South Pasadena, CA
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Straight up vertical cracks, I clip both ropes through every piece. Of course, also need to be careful to either clip all together or none together to minimize friction between adjacent ropes traveling different distances that could melt them. Sometimes I am sloppy in letting the ropes get crossed up though, which is just as bad.
This is the first thread that made me feel like a climbing dinosaur. I didn't even know there was anything fancier than a gri-gri. I always use ATC, or if I forgot it I use a munter hitch (works fine with double ropes). I used to try 'biner brakes but gave that up when I learned about the munter hitch.
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