Forums: Climbing Information: The Lab:
Testing a "Dynamic Belay"
RSS FeedRSS Feeds for The Lab

Premier Sponsor:

 


Carnage


Jan 26, 2011, 8:38 AM
Post #1 of 55 (6047 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Testing a "Dynamic Belay"
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

It doesnt take too much searching to find people saying something along the lines of

"dont use a gri-gri on gear because it's not a dynamic belay"

soon after there may be a post like this:

"I belay on gear all the time with a gri-gri, and my partners are still alive"

I want to test this. Does the gri-gri really matter: does the inch or two of rope slipping dissipate enough energy to make a difference in the peak force of the fall?

I feel like it's fairly easy to test this is a pretty real world situation. Setup a force meter on the top piece, have a weight attached to a rope, and have a real person attached to the other end. Drop the weight from several heights, simulating real world fall factors (including something close to FF2). There would be some safety precautions that would need to take place but it should be doable.

Let me know what you think. What suggestions you have, or links to an article with similar tests. I'm not interested in someone spewing about their beliefs, i'm interested in numbers. Also, dont link me the petzl fall simulator, i'm not talking about the case when a leader takes a whipper on a gri-gri attached to the anchor, im interested in whipping on a gri-gri attached to the person.

note:substitute cinch for gri-gri if you want...


jt512


Jan 26, 2011, 8:45 AM
Post #2 of 55 (6038 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21890

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (2 ratings)  
Can't Post

Carnage wrote:
It doesnt take too much searching to find people saying something along the lines of

"dont use a gri-gri on gear because it's not a dynamic belay"

soon after there may be a post like this:

"I belay on gear all the time with a gri-gri, and my partners are still alive"

I want to test this. Does the gri-gri really matter: does the inch or two of rope slipping dissipate enough energy to make a difference in the peak force of the fall?

I feel like it's fairly easy to test this is a pretty real world situation. Setup a force meter on the top piece, have a weight attached to a rope, and have a real person attached to the other end. Drop the weight from several heights, simulating real world fall factors (including something close to FF2). There would be some safety precautions that would need to take place but it should be doable.

Let me know what you think. What suggestions you have, or links to an article with similar tests. I'm not interested in someone spewing about their beliefs, i'm interested in numbers. Also, dont link me the petzl fall simulator, i'm not talking about the case when a leader takes a whipper on a gri-gri attached to the anchor, im interested in whipping on a gri-gri attached to the person.

note:substitute cinch for gri-gri if you want...

If you don't want people to post their opinions, then maybe you shouldn't post yours. For instance, where do you get the idea that a dynamic belay consists of an "inch or two" of rope slipping through the belay device, and where did you get the idea that a Cinch and a Grigri would produce equivalent results (ie, "substitute cinch for gri-gri if you want")?

Jay


Carnage


Jan 26, 2011, 8:53 AM
Post #3 of 55 (6026 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [jt512] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

My assumptions and their backing:

Cinch vs grigri: they both lock on the rope quickly, and in most cases don't let the rope slip (i know the cinch slips under high FF, if we want to test that, go for it, i'm trying to minimize the test cases) I think most people thing of the gri-gri and cinch as interchangeable when they're talking about dynamic vs non-dynamic belays

"inch or two of slippage" when i catch a fall on an ATC my brake had is typically gripping the rope less than 5-6 inches from the device both before and after a fall. The max distance that my hand would be down the rope is in the 1.5 feet range (again, approx). Given the fact that i dont notice much slippage, and how much rope is in play elsewhere in the fall, i'm hypothesizing that there is very little slippage in a typical fall. I'd like to test this hypothesis as well. I'm sure it will be a function of force, but what would the typical and worst case scenarios be?

edit to add: when i said dont post your opinions, i meant i dont care about answers like "i never belay trad with a grigri cause its bad" if you have a valid claim to backup your statement, let me hear it, but the main objective would be to provide test cases for an experiment.


(This post was edited by Carnage on Jan 26, 2011, 8:55 AM)


billl7


Jan 26, 2011, 8:59 AM
Post #4 of 55 (6012 views)
Shortcut

Registered: Oct 13, 2005
Posts: 1888

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

Carnage wrote:
I want to test this. Does the gri-gri really matter: does the inch or two of rope slipping dissipate enough energy to make a difference in the peak force of the fall?
You will have to decide which belay device to test.

ATC? If you changed an "inch or two" to a "foot or two", I'd say you're starting to get warmer. Edit: for hard lead falls.


(This post was edited by billl7 on Jan 26, 2011, 9:00 AM)


jt512


Jan 26, 2011, 9:14 AM
Post #5 of 55 (5993 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21890

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (2 ratings)  
Can't Post

Carnage wrote:
My assumptions and their backing:

Cinch vs grigri: they both lock on the rope quickly, and in most cases don't let the rope slip (i know the cinch slips under high FF, if we want to test that, go for it, i'm trying to minimize the test cases) I think most people thing of the gri-gri and cinch as interchangeable when they're talking about dynamic vs non-dynamic belays

First of all, if most people think that, then most people are wrong. By design, the Cinch is dynamic above a considerably lower force than the Grigri, so the Grigri and Cinch are most certainly not substitutable as the "static" belay device. Secondly, why would you design an experiment based on "what most people think"?

In reply to:
"inch or two of slippage" when i catch a fall on an ATC my brake had is typically gripping the rope less than 5-6 inches from the device both before and after a fall. The max distance that my hand would be down the rope is in the 1.5 feet range (again, approx). Given the fact that i dont notice much slippage, and how much rope is in play elsewhere in the fall, i'm hypothesizing that there is very little slippage in a typical fall. I'd like to test this hypothesis as well. I'm sure it will be a function of force, but what would the typical and worst case scenarios be?

In a "typical" fall, if you are using an ATC, and you actually know what you are doing (which is rare), you have the option of allowing as much rope as you like slide through the device to provide as dynamic a belay as you want, including the option of letting no rope slide through the device. That's one reason that Grigris aren't a good idea for trad; you never have the option to provide a dynamic belay.

In a severe fall, with an ATC you have no choice: unless there is a lot of friction in the system, the belay will be dynamic, and a lot more than two inches of rope will pass through the belay device. So, for either type of fall, the assumption implied in your first post that the difference between the devices comes down to one or two inches of rope slipping through the device is wrong.

At any rate, something similar to the test you are proposing has been done, and published. You can probably find it on the Web, and see if it answers your questions. I don't recall the results quantitatively, but qualitatively the impact force was much higher for the grigri than for any other device tested.

Jay


(This post was edited by jt512 on Jan 26, 2011, 9:20 AM)


Carnage


Jan 26, 2011, 10:13 AM
Post #6 of 55 (5940 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [jt512] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

jt512 wrote:
In a "typical" fall, if you are using an ATC, and you actually know what you are doing (which is rare), you have the option of allowing as much rope as you like slide through the device to provide as dynamic a belay as you want, including the option of letting no rope slide through the device. That's one reason that Grigris aren't a good idea for trad; you never have the option to provide a dynamic belay.

Jay

a technique i've seen described, but i've never seen it used. Properly executed, i'd admit, that this would decrease the force on the piece. Just like a properly executed hop during a fall w/ a grigri will decrease the impact force.

I've been looking for the research you hinted at, and i've been unable to find it. I did however find a post by rgold on mountain project. http://theclimbinglab.com/tiki-index.php

The summary paragraph of his post:
In reply to:
In summary, as with a number of issues in climbing (equalizing belay anchors, backing up rappels, wearing helmets, etc.), there are practices that are effective a large majority of the time but which may not work well or at all in a very small number of exceptional cases. Since the rope doesn't slip in most climbing falls, there is usually no difference in imposed peak load for a Gri-Gri and ATC-type devices. However, in high fall-factor low-friction circumstances, the rope slippage is a potential safety valve that may keep peak loads within the limits sustainable by trad gear, where as the same gear will blow with a Gri-Gri. I say "potential safety valve" because without gloves, it isn't clear that rope slippage will be controllable. If the belayer cannot maintain full strength grip or even loses control, rope slippage becomes not a safety valve but a liability. Moreover, even if the belayer hangs on, the burns sustained can range from annoying to exceptionally severe---as in down to the bone.

Using an ATC-type device rather than a Gri-Gri means (if you were to think logically about it) that you want the potential safety-valve effect that might come into play in exceptional circumstances. Not wearing gloves turns that potential effect into a liability and so contradicts choosing the ATC-type device---at least that's the way it appears to me.

which means to me, in most cases, it doesnt matter. When it comes to high FF, you either use a gri-gri and hope the gear holds, or use an ATC and use gloves.

Rgold does not link to any sources, but mentions them, i've again been unable to find them. i did find http://web.mit.edu/...55_rope_behavior.pdf which hints at it, however the graph listed as experimental verification VAI Belaying forces w/ slip specifically says fix point belay.


jt512


Jan 26, 2011, 10:38 AM
Post #7 of 55 (5926 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21890

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

Carnage wrote:
jt512 wrote:
In a "typical" fall, if you are using an ATC, and you actually know what you are doing (which is rare), you have the option of allowing as much rope as you like slide through the device to provide as dynamic a belay as you want, including the option of letting no rope slide through the device. That's one reason that Grigris aren't a good idea for trad; you never have the option to provide a dynamic belay.

Jay

a technique i've seen described, but i've never seen it used. Properly executed, i'd admit, that this would decrease the force on the piece. Just like a properly executed hop during a fall w/ a grigri will decrease the impact force.

I've been looking for the research you hinted at, and i've been unable to find it. I did however find a post by rgold on mountain project. http://theclimbinglab.com/tiki-index.php

The summary paragraph of his post:
In reply to:
In summary, as with a number of issues in climbing (equalizing belay anchors, backing up rappels, wearing helmets, etc.), there are practices that are effective a large majority of the time but which may not work well or at all in a very small number of exceptional cases. Since the rope doesn't slip in most climbing falls, there is usually no difference in imposed peak load for a Gri-Gri and ATC-type devices. However, in high fall-factor low-friction circumstances, the rope slippage is a potential safety valve that may keep peak loads within the limits sustainable by trad gear, where as the same gear will blow with a Gri-Gri. I say "potential safety valve" because without gloves, it isn't clear that rope slippage will be controllable. If the belayer cannot maintain full strength grip or even loses control, rope slippage becomes not a safety valve but a liability. Moreover, even if the belayer hangs on, the burns sustained can range from annoying to exceptionally severe---as in down to the bone.

Using an ATC-type device rather than a Gri-Gri means (if you were to think logically about it) that you want the potential safety-valve effect that might come into play in exceptional circumstances. Not wearing gloves turns that potential effect into a liability and so contradicts choosing the ATC-type device---at least that's the way it appears to me.

which means to me, in most cases, it doesnt matter.

On most falls it doesn't matter—if the gear is good enough—because most falls have low fall factors. On most routes it critically matters because most routes have the potential for factor-2 falls.

But even with respect to falls, the belayer rarely knows whether the gear is good enough to withstand a static catch; belayers should probably be giving dynamic catches more often than they do.

In reply to:
When it comes to high FF, you either use a gri-gri and hope the gear holds, or use an ATC and use gloves.

Since you can't know ahead of time whether you are going to have to catch a factor-2 fall or not, you always have to be prepared to do so (on a multipitch route), so that means never belay the leader with a Grigri (above the first pitch, anyway) and always wear gloves.

Jay


Carnage


Jan 26, 2011, 10:55 AM
Post #8 of 55 (5913 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [jt512] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

so will you then agree that in a non FF2 situation ("most falls") it doesnt matter whether you use a grigri or an atc?

in a FF2 it will significantly increase the force on the anchor?


jt512


Jan 26, 2011, 10:58 AM
Post #9 of 55 (5907 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21890

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (2 ratings)  
Can't Post

Carnage wrote:
so will you then agree that in a non FF2 situation ("most falls") it doesnt matter whether you use a grigri or an atc?

Didn't I just answer that question in my last post?

My question is this: why are you even thinking about what matters in most falls? What is important is what happens in a factor-2 fall. I don't want to survive most falls; I want to survive every fall.

Jay


Carnage


Jan 26, 2011, 12:01 PM
Post #10 of 55 (5879 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [jt512] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

i do mostly single pitch trad and sport, so for me, grigri 100% of the time is fine.

From the people i've talked to, they say grigri is not appropriate for even single pitch trad, which is wrong. they seem to have a ur gonna die mentality.


Partner cracklover


Jan 26, 2011, 12:24 PM
Post #11 of 55 (5857 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Carnage wrote:
i do mostly single pitch trad and sport, so for me, grigri 100% of the time is fine.

OK, sounds like this conversation is over. You have come to your conclusion (which happens to be wrong BTW) *before* doing the research.

No reason to discuss this further - you're not serious about your objective.

And no way would I ever climb trad with you - not on anything I wasn't comfortable soloing.

GO


jt512


Jan 26, 2011, 12:26 PM
Post #12 of 55 (5856 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21890

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

Carnage wrote:
i do mostly single pitch trad and sport, so for me, grigri 100% of the time is fine.

If you only "mostly" do single-pitch trad (and sport), then how can using a grigri "100% of the time" be "fine"? You don't seem to understand the most basic of all principles of belaying: always be prepared to handle the worst-case scenario fall. Instead, you are apparently treating climbing as a game of Russian Roulette, relying on the statistical improbability of having to catch a factor-2 fall when you climb multi-pitch.

In reply to:
From the people i've talked to, they say grigri is not appropriate for even single pitch trad, which is wrong.

I agree with them, but probably for a different reason. I think that the finer-grained control over how dynamic your belay is that you get with an ATC vs. a Grigri is important when the leader is placing protection. I want to have the option of providing as soft a catch as possible. As the belayer, I don't know how good their pro is (and, for that matter, sometimes neither does the leader).

Jay


Carnage


Jan 26, 2011, 1:10 PM
Post #13 of 55 (5829 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [jt512] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

i was incorrect to say 100% of the time. To be clear, i was trying to say when i climb single pitch trad, i'll be using a grigri, when i do multipitch, i'll use an atc.

I understand what you're saying about handling the worst case scenario and quite honestly, i think we're on the same side of the topic.

cracklover from my understanding seems to think small lead falls on a grigri will equal death.


Partner cracklover


Jan 26, 2011, 1:38 PM
Post #14 of 55 (5810 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

You clearly don't have a clue.

A fall on the first or second piece can easily generate 10kN+ of force with a fully static belay. That's on single pitch. You blow that piece, and you're probably decking.

GO


Carnage


Jan 26, 2011, 1:43 PM
Post #15 of 55 (5803 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

fully static belay and grigri belay are not the same thing.


Partner j_ung


Jan 26, 2011, 1:44 PM
Post #16 of 55 (5801 views)
Shortcut

Registered: Nov 21, 2003
Posts: 18687

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Carnage wrote:
cracklover from my understanding seems to think small lead falls on a grigri will equal death.

Of course, that would depend somewhat on the quality of the protection. A drop-in stopper placement in a granite crack is one thing. A TCU in a bomb-bay flare is another entirely.


Carnage


Jan 26, 2011, 1:58 PM
Post #17 of 55 (5792 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [j_ung] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

j_ung wrote:
Carnage wrote:
cracklover from my understanding seems to think small lead falls on a grigri will equal death.

Of course, that would depend somewhat on the quality of the protection. A drop-in stopper placement in a granite crack is one thing. A TCU in a bomb-bay flare is another entirely.

I curious how accurate this claim is. The whole point of this thread was to get numbers to investigate this.


LostinMaine


Jan 26, 2011, 8:14 PM
Post #18 of 55 (5698 views)
Shortcut

Registered: May 8, 2007
Posts: 539

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Has anyone here caught a fall with a Cinch while in "feeding" mode? I wonder if this differs much from the Cinch catching a fall while in it's "locked off" mode.

I guess I have the opposite view from you, Carnage. I would be much more interested to test the Cinch specifically against the Gri-Gri as opposed to assuming one substitutes for the other. Though the Cinch does allow more slippage at a lower impact force, I wonder exactly how much slips and if that is enough to alleviate concerns of a static belay.


rocknice2


Jan 26, 2011, 9:11 PM
Post #19 of 55 (5673 views)
Shortcut

Registered: Jul 13, 2006
Posts: 1197

Re: [LostinMaine] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

LostinMaine wrote:
Has anyone here caught a fall with a Cinch while in "feeding" mode? I wonder if this differs much from the Cinch catching a fall while in it's "locked off" mode.

I had that happen to me once. Leader fell while clipping and I couldn't see him.
I was using the pinch technique and the rope slipped through a foot or two. Have to say that I did pinch hard but the slippage was slow. Once the leaders full weight loaded the rope it snapped the Cinch up and locked. I always had 3 fingers on the rope and could feel the slippage but like I said it was slow at first and then it locked up perfectly.

I now pinch it at the hinge and not at the edge.


Partner cracklover


Jan 27, 2011, 7:37 AM
Post #20 of 55 (5615 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Carnage wrote:
j_ung wrote:
Carnage wrote:
cracklover from my understanding seems to think small lead falls on a grigri will equal death.

Of course, that would depend somewhat on the quality of the protection. A drop-in stopper placement in a granite crack is one thing. A TCU in a bomb-bay flare is another entirely.

I curious how accurate this claim is. The whole point of this thread was to get numbers to investigate this.

I have done testing myself, and it is not hard to rip small-to-medium sized cams out of okay but not great placements at under 5kN. Not every time, but a good percentage of the time.

Your problem is that you know everything already, based on, so far as I can tell, exactly zilch. Not exactly the right mindset for learning.

GO


Carnage


Jan 27, 2011, 8:13 AM
Post #21 of 55 (5601 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

cracklover wrote:
Carnage wrote:
j_ung wrote:
Carnage wrote:
cracklover from my understanding seems to think small lead falls on a grigri will equal death.

Of course, that would depend somewhat on the quality of the protection. A drop-in stopper placement in a granite crack is one thing. A TCU in a bomb-bay flare is another entirely.

I curious how accurate this claim is. The whole point of this thread was to get numbers to investigate this.

I have done testing myself, and it is not hard to rip small-to-medium sized cams out of okay but not great placements at under 5kN. Not every time, but a good percentage of the time.

Your problem is that you know everything already, based on, so far as I can tell, exactly zilch. Not exactly the right mindset for learning.

GO

My problem is i cant find any information, thats why i proposed a test.

I dont argue that you can pull out a marginal piece with a grigri. My question is does the grigri really increase the force (as i've heard some people say). The goal would be to find out if a piece would have held if belayed by an atc, but popped because it's was belayed with a grigri.

i dont understand why you say i've already made up my mind. I;ve stated hypothesis that i want tested. obviously i have an opinion, an opinion that can change with relevant data.


Partner cracklover


Jan 27, 2011, 12:48 PM
Post #22 of 55 (5563 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

Carnage wrote:
cracklover wrote:
Carnage wrote:
j_ung wrote:
Carnage wrote:
cracklover from my understanding seems to think small lead falls on a grigri will equal death.

Of course, that would depend somewhat on the quality of the protection. A drop-in stopper placement in a granite crack is one thing. A TCU in a bomb-bay flare is another entirely.

I curious how accurate this claim is. The whole point of this thread was to get numbers to investigate this.

I have done testing myself, and it is not hard to rip small-to-medium sized cams out of okay but not great placements at under 5kN. Not every time, but a good percentage of the time.

Your problem is that you know everything already, based on, so far as I can tell, exactly zilch. Not exactly the right mindset for learning.

GO

My problem is i cant find any information, thats why i proposed a test.

I dont argue that you can pull out a marginal piece with a grigri. My question is does the grigri really increase the force (as i've heard some people say). The goal would be to find out if a piece would have held if belayed by an atc, but popped because it's was belayed with a grigri.

i dont understand why you say i've already made up my mind. I;ve stated hypothesis that i want tested. obviously i have an opinion, an opinion that can change with relevant data.

Do you understand the difference between a hypothesis and an assumption? In order to correctly test a hypothesis, your underlying assumptions must be true, otherwise your hypothesis itself may be faulty, or, barring that, the conclusions you draw from your observations may be faulty.

Furthermore, any experiment carried out under a strong enough preexisting bias is likely to only reinforce the observer's hypothesis, as any "outlying" data is simply discarded as faulty.

You have made it clear throughout that your opinion is already so biased that you have been up to this date been potentially putting the lives of all your climbing partners at risk because they are all wrong and you are right, regarding the safety of a grigri in single pitch trad.

Here are just a few of the incorrect assumptions you've stated as fact, and, in many cases, been called out on:

Carnage wrote:
I want to test this. Does the gri-gri really matter: does the inch or two of rope slipping dissipate enough energy to make a difference in the peak force of the fall?

Assumption #1: Only difference between the two is an inch or two of rope.
Assumption #2: Small amount of rope slippage in a short high factor fall makes little difference.
Possible assumption: The actual slippage is what "dissipates" the force.

In reply to:
note:substitute cinch for gri-gri if you want...

Assumption #3: Cinch and gri-gri are identical in such cases.

Carnage wrote:
so will you then agree that in a non FF2 situation ("most falls") it doesnt matter whether you use a grigri or an atc?

in a FF2 it will significantly increase the force on the anchor?

Assumption #4: Only FF > 1 create a large enough force to rip reasonably good looking gear.

Carnage wrote:
i do mostly single pitch trad and sport, so for me, grigri 100% of the time is fine.

From the people i've talked to, they say grigri is not appropriate for even single pitch trad, which is wrong. they seem to have a ur gonna die mentality.

Assumption #5: A grigri is always appropriate for single pitch sport.

GO


mikebee


Jan 27, 2011, 6:49 PM
Post #23 of 55 (5515 views)
Shortcut

Registered: Sep 15, 2006
Posts: 190

Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Another aspect of dynamic belay technique has been totally ignored here - the "jump". A belayer will often jump up as the rope comes tight against their harness to further soften the fall when the leader pops.

I'd suggest that a good belayer using a GriGri but prepared and able to execute a jump would be able to reduce the impact force far more than a belayer who was aiming to offer a dynamic belay through rope slipping through an ATC. I daresay the GriGri belayer would maintain better control of the rope throughout the process too. Obviously, a jump won't work in a FF2 scenario.


jt512


Jan 27, 2011, 6:59 PM
Post #24 of 55 (5512 views)
Shortcut

Registered: Apr 11, 2001
Posts: 21890

Re: [mikebee] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (2 ratings)  
Can't Post

mikebee wrote:
I'd suggest that a good belayer using a GriGri but prepared and able to execute a jump would be able to reduce the impact force far more than a belayer who was aiming to offer a dynamic belay through rope slipping through an ATC. I daresay the GriGri belayer would maintain better control of the rope throughout the process too.

Wrong on both counts. Regarding which technique is capable of decreasing the impact force more, clearly letting rope slide through the belay device is because, with practice, you can let as much rope slide through as you want, and therefore you can decelerate the climber as gradually as you want. Regarding control, when you lower do you let the rope slide through your brake hand, and if so, do you ever lose control of it?

Jay


(This post was edited by jt512 on Jan 27, 2011, 7:05 PM)


JimTitt


Jan 28, 2011, 1:17 AM
Post #25 of 55 (5469 views)
Shortcut

Registered: Aug 7, 2008
Posts: 975

Re: [jt512] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Hi jt, basically you´ve said it all.

To the OP
For a Grigri the slip appears to be around 3" for almost any length of fall, for the Cinch it is from virtually nothing up to lots of feet in a hardish fall (I´ve got some drop test results somewhere which are quite exciting in that respect).
For plates (ATC´s etc) the slip starts in feet and goes on up massively depending on impact, fall energy, belayer strength, number of runners, rope dia etc.

Plenty of tests on all this but as usual in German or Italian however outdoor testing with real belayers is quite difficult as the variables are all so large you don´t get much meaningful data and probably the conclusions would be misintepreted by the normal climber.

A big guy like me that bashes metal most of the time can get higher values with an ATC than a whippet-thin girlie with a Grigri anyway so its going to be hard to make any useful rule except:-
A Grigri hits harder than a plate all things being equal by about 30-50%.
The Cinch hits harder than anything on small falls but less than most in large falls.
Jumping in small falls is possibly worthwhile, in big ones it´s not.
Jumping is never as good as dynamically controlling the rope slip because as stated earlier the slip is measured in lots of feet and climbers don´t jump that well.
The peak force on the top runner occurs before the rope starts to slip through the device and to reduce this force you need to allow a lower initial slip value and then increase the breaking force which is why dynamic belaying is the way to go.
Force Factors are not particularly relevant, the length of the fall is. One can have a FF1 directly onto the belayer without any intermediate gear or a FF1.9 with 100 karabiners forcing the rope through such contortions that the belayer feels nothing. This is in fact why the Petzl calculator is useful as it allows for this to some extent.

Wear gloves.

Jim


Carnage


Jan 28, 2011, 9:38 AM
Post #26 of 55 (3113 views)
Shortcut

Registered: Mar 27, 2007
Posts: 923

Re: [JimTitt] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

Jim, thanks for your input. I guess i'm pretty much dead wrong.


caughtinside


Jan 28, 2011, 10:25 AM
Post #27 of 55 (3099 views)
Shortcut

Registered: Jan 8, 2003
Posts: 30371

Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

That is some good info. I often use a grigri for single pitch trad climbing, mostly on granite but some at Indian Creek. I've thought the jump was an adequate force reducer on the gear, but I guess not?

Probably caught 100 or so falls on gear on the grigri, only one piece pulled.

Not sure yet if I'll switch devices, been nearly clanged a couple times by the leader kicking something off.


Partner cracklover


Jan 28, 2011, 10:58 AM
Post #28 of 55 (3084 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [caughtinside] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

caughtinside wrote:
That is some good info. I often use a grigri for single pitch trad climbing, mostly on granite but some at Indian Creek. I've thought the jump was an adequate force reducer on the gear, but I guess not?

Probably caught 100 or so falls on gear on the grigri, only one piece pulled.

Not sure yet if I'll switch devices, been nearly clanged a couple times by the leader kicking something off.

On routes with small gear near the ground, or really sandy funky rock - be well worth considering.

Cheers,

GO


qwert


Jan 31, 2011, 3:46 AM
Post #29 of 55 (3026 views)
Shortcut

Registered: Mar 24, 2004
Posts: 2392

Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

One of the german tests Jim Tit mentioned is probably this one:
http://www.alpenverein.de/...5d9d8468a2e73a1e29d1

I wont translate it, but here is some words about it, and a quick look at some of the numbers they got:

The DAV tested a few belay devices (Tube (looks like it was a classic ATC), various forms of 8s, munterhitch/'HMS, GriGri and TRE) in a factor 0.4 fall.

The fixed the devices to the belay, and belayed with an artificial hand, where they could adjust the hand power, which is - according to a previous study - 209N on average.
so they ran the tests with a hand power of 100N, 250N, 400N and two Persons.

They measured the forces on the top piece and that are the results:

Code
Hand force:       |   100N   |   250N   |   400N   | Person1 | Person2  
Top force GriGri| 5.9kN | 5.6kN | 5.5kN | - not tested -
Top force Tube | 2.7kN | 3.8kN | 5.0kN | 3.8kN | 4.1kN
rope slip GriGri| 9cm | 8cm | 9cm | - not tested -
rope slip Tube | 182cm | 51cm | 22cm | 101cm | 66cm

Obviously this is -as mentioned - a fixed belayer and a small fall factor, but it is safe to assume that those observations also apply for bigger stuff.
The less the belayer grabs the rope, the less force the top piece will see if you are using a dynamic device. If you know how to do this, this can be used to give a soft catch/ help bad protection to stay in.
However if you simply dont have significant force, this might result in uncontroled slipage, that will burn you hand.
On the other hand, if you have strong hands, and simply lock up the rope, you can - if we are ignoring jumping or being pulled up - produce forces quite similar to the grigri.

I would be interested on how some "increased braking strength" tubes like the ATC-XP behave in this test.
I am simply going to claim that this will increase the top force/ reduce the slipage, and that this will reduce the hand force needed to make it static, and thus that there probably are quite a few folks out there who might as well belay trad with a grigri, since it wouldnt make a difference for them anyways.

qwert


(This post was edited by qwert on Jan 31, 2011, 3:50 AM)


Partner cracklover


Jan 31, 2011, 8:33 AM
Post #30 of 55 (3006 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [qwert] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Interesting study. Since I often belay trad with a TRE, that part was of particular interest to me.

On the moderate fall studied, the TRE (called Sirius in the study) was pretty much equivalent to the Gri Gri. This is not surprising, since it is supposed to lock down and slip at around 3.5 to 4 kN, which is above the amount felt by the belayer in this fall.

So, for the severity of fall studied, the TRE performed as advertised. But I would have liked to see if there *was* in fact this divergence for harder falls - since this is one of the pluses to me in using the TRE.

GO


qwert


Jan 31, 2011, 8:38 AM
Post #31 of 55 (3004 views)
Shortcut

Registered: Mar 24, 2004
Posts: 2392

Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

I didnt include the values for the TRE, since this thread is about the GriGri, but yeah, you're right, additional tests with higher fall factors would have been nice.

But unfortunately they havent done them.

qwert


Partner cracklover


Jan 31, 2011, 8:57 AM
Post #32 of 55 (2997 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [qwert] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

qwert wrote:
I didnt include the values for the TRE, since this thread is about the GriGri, but yeah, you're right, additional tests with higher fall factors would have been nice.

But unfortunately they havent done them.

qwert

As a TRE user, I did find one other reference interesting. If I translated correctly (and my German isn't so great these days, so who knows) - they imply that due to the results of the study, they don't recommend belaying a leader directly off the anchor with the GriGri or the TRE. And they explicitly state that while Petzl actually does not endorse such a method, TRE does.

I only ever belay with my TRE direct off the anchor when bringing up a second - never for a leader. And again, with harder falls, there might be more of a divergence between TRE and GriGri. But it's still worth keeping in mind, in case one is ever in a situation where it's tempting to belay the leader directly off the anchor.

I know there are other users of the TRE on this forum, so - sorry for the thread hijack - but I thought it might interest others too.

GO


Partner cracklover


Jan 31, 2011, 9:02 AM
Post #33 of 55 (2993 views)
Shortcut

Registered: Nov 14, 2002
Posts: 9974

Re: [JimTitt] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

JimTitt wrote:
This is in fact why the Petzl calculator is useful as it allows for this to some extent.

Hi Jim,

About a year ago the link I had been using to get to the Petzl calculator stopped working, and I have been unable to find the calculator anywhere on their site.

Do you have a new link to the calculator, or do you know if it still exists anywhere on the web?

Thanks,

GO


JimTitt


Jan 31, 2011, 12:47 PM
Post #34 of 55 (2949 views)
Shortcut

Registered: Aug 7, 2008
Posts: 975

Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (1 rating)  
Can't Post

The company is called TRE and the device the Sirius just to clear things up!
TRE published some test graphs for the Sirius where it was a bit less powerful than an HMS but they didn´t give any test details so that isn´t very helpful. We don´t know if the impact force is for the device alone or with a top runner, if it was tested alone then the lower impact force (than the HMS) corresponds with the findings of the DAV with a higher force because the rate of force rise for the Sirius is considerably higher than the HMS. (A bit complicated but due to the stretch in the rope, damping and friction on the runner the steepness of the force curve has a lot of influence on the peak forces further down the rope.)
Anyway your Sirius must be so worn out now it wouldn´t stop a falling raindrop!
The real objection from the DAV is that with both the Grigri and Sirius and a fixed belay the belayer has no control over the braking and cannot influence whether the climbers hits the rock hard or not.

The `high power´devices aren´t really that much more powewrful despite the attempts of the marketing guys! An ATC XP has been shown time and again to be about 20-30% more powerful than an normal ATC but the exact value depends on the drop.
One probem is that it is all so variable, one of the farm mechanics by my workshop can defeat a Grigri with one hand using an ATC XP because he is a monster whereas one of my climbing partner gives me a gentle stop with a Grigri because I´m 90kg and she is 55kg.
As we see it the desirable position is to have a more powerful device than a standard plate (we use the ATC XPfor this) which is easy to regulate which will allow for progressive stops no matter what the fall and also cover a greater range of ropes and belayers.
However it´s not so easy, we made a plate with 50% more power (than an XP) but then abseiling and lowering started getting a bit clunky with thicker ropes and we though customers wouldn´t like it so detuning was called for!

Jim


Partner j_ung


Jan 31, 2011, 1:12 PM
Post #35 of 55 (2938 views)
Shortcut

Registered: Nov 21, 2003
Posts: 18687

Re: [JimTitt] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Jim, does the Chicane address some of these issues, and if so, how? What are are its trade offs?


healyje


Jan 31, 2011, 1:35 PM
Post #36 of 55 (2930 views)
Shortcut

Registered: Aug 22, 2004
Posts: 4199

Re: [qwert] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Those ATC rope slip numbers look outlandish and like someone doesn't know how to belay with one. I've never had rope slip anywhere near those numbers in thirty-six years of climbing with either a hip belay or an ATC of any style/make and find them quite unbelievable.

Edit: Ah, 'artificial hand' - got it - ridiculous test design.


(This post was edited by healyje on Jan 31, 2011, 1:36 PM)


JimTitt


Feb 1, 2011, 12:10 AM
Post #37 of 55 (2892 views)
Shortcut

Registered: Aug 7, 2008
Posts: 975

Re: [healyje] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Hmmm, since in that particular test they (the DAV) also used two human belayers and the results where almost identical or even slightly worse then I think it is fair to accept they are right and you are wrong.
However it is possible that your 35 years climbing has given you higher than average hand strength in which case the slip will decrease dramatically, 400N which an old guy like me with 42 years experience can reasonably achieve gives 22cm slip. And it´s unlikely that in your 35 years of climbing you have been holding falls using a brand new 9.6mm rope every time, if you use a furry monster the slip will be negligable!

250N artificial hand - 1.7kN 51cm
Test belayer 1 - 1.7kN 66cm
Test Belayer 2 - 1.5kN 101cm

Using a different design of hand which measured the force a different way and a lower FF and braking force Manin of the CMT (Italy) got 1.26kN and 86cm

Black Diamond and I test by pulling and so we have to calculate the slip from the power ratio and for the DAV fall we get 57cm and 52cm.

The climbing industry and the powers-that-be are kind in that they not only consider the capabilities of hairy assed old men with decades of experience but have to look after the interests of weak and feeble beginners and even `gasp´ delicate members of the opposite sex with their delicate, callus-free moisturised palms!

Jim


JimTitt


Feb 1, 2011, 12:16 AM
Post #38 of 55 (2889 views)
Shortcut

Registered: Aug 7, 2008
Posts: 975

Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

The Petzl calculator was pulled off or moved when then re-designed their site and I´ve not seen it since though to be fair I didn´t use it a lot since I can usually find the info another way.


healyje


Feb 1, 2011, 12:18 AM
Post #39 of 55 (2885 views)
Shortcut

Registered: Aug 22, 2004
Posts: 4199

Re: [JimTitt] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

JimTitt wrote:
Hmmm, since in that particular test they (the DAV) also used two human belayers and the results where almost identical or even slightly worse then I think it is fair to accept they are right and you are wrong.

Then the test design and belaying methods used therein were obviously faulty as given a rope of any diameter and a correspondingly appropriate-sized ATC there is no way for slippages like those to occur unless you are incompetent (i.e. faulty test design).


JimTitt


Feb 1, 2011, 12:41 AM
Post #40 of 55 (2880 views)
Shortcut

Registered: Aug 7, 2008
Posts: 975

Re: [j_ung] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

The prototypes where running over 50% more power than an XP and with thick ropes this was a pain, the impact forces where getting higher than we´d like and lowering and abseiling a problem with light people and double ropes. Conversly with thin ropes the performance was brilliant so what I did was reduce the thick rope force while trying to keep the thin rope performance which I more or less achieved.

The trade-off is you need to be more alert to the climber weight or any friction when you are going to be lowering, the difference between the high and low power sides is much more noticeable than usual so for lighter climbers and easy angled stuff you really want to be going to the low power setting or the rope feed is a bit jerky. Or you just tilt the plate with your thumb!

Publishing our internal test results is a bit of a difficult issue and we´ll probably have to wait for someone independent to do the tests.

Jim


qwert


Feb 1, 2011, 1:59 AM
Post #41 of 55 (2869 views)
Shortcut

Registered: Mar 24, 2004
Posts: 2392

Re: [healyje] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

healyje wrote:
JimTitt wrote:
Hmmm, since in that particular test they (the DAV) also used two human belayers and the results where almost identical or even slightly worse then I think it is fair to accept they are right and you are wrong.

Then the test design and belaying methods used therein were obviously faulty as given a rope of any diameter and a correspondingly appropriate-sized ATC there is no way for slippages like those to occur unless you are incompetent (i.e. faulty test design).
From what you are saying, it seems like you think that all slippages they measured are too high. So either you dont know what kind of length a cm is (its much less than an inch!) ;) or you have big hand strength and always lock up your ATC.
Obviously the 180cm are critical, especially when you are trying to hold that without gloves, but the 22 to 51 cm range seems realistic to me.
Thats about the range i let trough the device, if i try to actively give a soft belay.
Also i do not really see where their test design is faulty.
Yes - an artificial hand (which seems to be some kind of pulley thingy, if you look at the pic in the report) will never grab the rope just the same as a real hand, but thats probably what makes it usefull. With a real hand you might have all kinds of factors that will affect the holding power of said hand (smooth skin vs. rough calluses vs. leather glove; chalked hands vs. sweaty hands; slightly different position of the rope in the hand and of the hand compared to the belay device; etc.), independent of how much N the testee can produce.
And many of these factors will probably vary between test falls, even if you always use the same testee.
And with the artificial hand, you at least get compareable numbers between devices, and personally i think it is safe to assume that those numbers would translate to the real world to some amount.
The question is just how much. For example i have never seen slip like the 180cm, even when kids belay, but then its mostly ATC XPs (that do seem to have more holding power, although probably not as much as the marketing would make one belief), thicker or older ropes, and fall wheights under 80kg.

qwert


healyje


Feb 1, 2011, 2:58 AM
Post #42 of 55 (2859 views)
Shortcut

Registered: Aug 22, 2004
Posts: 4199

Re: [qwert] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

I'm talking about a fall happens and you lock up the ATC. In that instance if 8-20" of rope is streaming through the ATC then something is dreadfully wrong with the belaying in anything but an unexpected, unannounced, out-of-sight fall. Oh, and hand strength plays very little into the matter; in fact, if you're depending on 'hand strength' as a substantial factor in the belay you're kind of screwed up front. It's a matter of proper pairing of ATCs-to-diameter. I don't trad lead on single ropes smaller than 9.8 personally, but that's me and use a Kong Ghost on my 9.x cords and a Bug or Reversino on my 7.8 twins - no problem with slippage on any of them regardless of hand strength.

If you are talking about deliberately paying out slippage (which by and large I think is a bad idea in trad climbing except in rare situations), then anything is possible given how badly the demographic belays in general. Teaching people to pay out slippage? Again, by and large a lousy idea - better to teach them to use a screamer on any piece they are that concerned about it.

Hell, I've held solid lead falls on a 9.8 with a hip belay through a single non-locking biner going to the leader and not had any appreciable slippage - something's just not right or someone's not doing it right if they are getting those slippage rates when trying to lock it up - either that or the general situation out there is worse than I imagined.


(This post was edited by healyje on Feb 1, 2011, 3:04 AM)


JimTitt


Feb 1, 2011, 3:31 AM
Post #43 of 55 (2853 views)
Shortcut

Registered: Aug 7, 2008
Posts: 975

Re: [healyje] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

There is NO lower force limit where slip does not occur. The rope slips in all belay devices and methods, alone the stretch in the rope between the belayers hand and the device takes care of that!
Hand strength (more exactly the ability to grip a particular rope diameter) IS the determining factor in a given devices performance. The relationship between hand strength and braking force is almost perfectly linear.

Advising use of a screamer on anything but an extremely mild fall is incorrect.

Jim


healyje


Feb 1, 2011, 3:38 AM
Post #44 of 55 (2847 views)
Shortcut

Registered: Aug 22, 2004
Posts: 4199

Re: [JimTitt] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

We will have to agree to disagree.

And I'm not speaking of rope stretch - I'm speaking of brake hand position/distance from the device being unchanged and zero rope slip through the hand. If you are encountering either your hand moving towards the device or the rope slipping through your hand then something is wrong.

Grip-to-diameter is strictly a matter of appropriately sizing the rope to the device. Properly sized the diameter decrease shouldn't require more hand strength.

Any time there is concern about about a piece ripping then the answer should be put a screamer on it - not attempt a 'dynamic' belay unless you are a highly experienced and very competent belayer and even then I'm going with the screamer every single time.


qwert


Feb 1, 2011, 4:25 AM
Post #45 of 55 (2841 views)
Shortcut

Registered: Mar 24, 2004
Posts: 2392

Re: [healyje] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

healyje, so what you are saying is that you have a specific device for every rope size you use?
While it should be obvious to anyone that "extremes" such as using a fig8 with a single 8mm rope, or a reversino with a fuzzy 11mm rope should be avoided, This becomes less obvious with "normal" rope sizes between say 9.5 and 10.5mm, and the additional "holding power" their fuzziness will introduce.
Yes, i know that manufacturers normally rate their devices only for specific thickness rates, but this is somewhat irrelevant if we are going to take stuff like dry treatments, thight sheats and wear into account.
Essentially those factors can cause a 10mm rope to be harder to hold than a 9mm rope. Obviously its the beleayers responsibility to assess the rope, and belay accordingly, but since the handling of a rope can change even during a single climb, a device (and a belayer) should be able to handle a certain range of ropes.

I am going to side with the DAV (and jim Tit) here, and believe that the rope slip has to do with the hand force.
I do not know you, but i wouldnt be surprised if you hand force is simply above average and thus you lock up the device with no slip, essentially turning it into a static belay device.

And something on the screamers:
(slightly of topic, but since we are talking about a DAV paper, i think it should be mentioned)
It seems to me that screamers are strictly an american thing. I only hear about using screamers here, even to the point that people use only screamers instead of quickdraws while ice climbing.
I have never seen a screamer in real life - neither on the racks of my friends, nor on the racks of other climbers i encountered, no matter if those encounters where on trad, alpine or ice.


qwert


healyje


Feb 1, 2011, 5:04 AM
Post #46 of 55 (2832 views)
Shortcut

Registered: Aug 22, 2004
Posts: 4199

Re: [qwert] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

If you mean I use different ATCs for 10.x, 9.x, and sub-9.0 ropes then the answer is absolutely. It is critical to pair the device to the rope diameter and I personally don't really buy the idea that brake-side 'grooving' and groove texturing makes up enough of a difference compared to a properly [down]sized device. I also don't consider sub-9.8 cords 'normal' , but rather recent innovations whose use with an inadequate device (autoblocking or ATC) is just a bad idea in the hands of most of today's demographic.

Overall I don't use cords that 'fuzz' for the most part and don't consider fuzz / coating in the equation except relative to my roped-soloing device (Eddy) and there I'm exceptionally picky about my ropes and stiffness/fuzz/coating do get taken into account.

In the end I just can't and don't ascribe to the 'range of rope sizes' or 'one-size-fits-all' school of belay device selection. In fact, I think it's a poor idea in general and one borne of misplaced convenience.

In reply to:
I am going to side with the DAV (and jim Tit) here, and believe that the rope slip has to do with the hand force.

It definitely is if you are using the wrong size device.

Hey, I have completely average hand strength, again, it's all about careful device/rope pairing. And that's something that doesn't really happen much these days which I consider somewhat unfortunate as folks gravitate towards smaller and smaller cord diameters (usually for no good reason relative to the routes they are doing or their climbing level).

Screamers in the US are mainly only seen in aid and ice climbing and most screamered falls are probably by aid climbers. But I have a long history of free climbing over what most people would consider very marginal pro - stacked passive pieces, skyhooks, Crack 'N Ups, #1-3 Loweballs, and equalized RP nests. I've blown dozens of screamers taking repeated falls onto placements working some cruxs where the pro for sure wouldn't have held without them. On really delicate placements I pre-slice the screamers at an steep angle with a razor blade in order to flatten out their loading curve so it's less jarring. Overall, I wouldn't trust any of those screamered placements to the unpredictable vagaries of attempts at a 'dynamic' belay - I want the belayer to just lock it up and I'll take care of the 'dynamic' protection of my placements if they need it.


(This post was edited by healyje on Feb 1, 2011, 5:31 AM)


Partner j_ung


Feb 1, 2011, 5:50 AM
Post #47 of 55 (2821 views)
Shortcut

Registered: Nov 21, 2003
Posts: 18687

Re: [JimTitt] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

JimTitt wrote:
The prototypes where running over 50% more power than an XP and with thick ropes this was a pain, the impact forces where getting higher than we´d like and lowering and abseiling a problem with light people and double ropes. Conversly with thin ropes the performance was brilliant so what I did was reduce the thick rope force while trying to keep the thin rope performance which I more or less achieved.

The trade-off is you need to be more alert to the climber weight or any friction when you are going to be lowering, the difference between the high and low power sides is much more noticeable than usual so for lighter climbers and easy angled stuff you really want to be going to the low power setting or the rope feed is a bit jerky. Or you just tilt the plate with your thumb!

Publishing our internal test results is a bit of a difficult issue and we´ll probably have to wait for someone independent to do the tests.

Jim

When are they available? I'd love to review one.


qwert


Feb 1, 2011, 6:19 AM
Post #48 of 55 (2813 views)
Shortcut

Registered: Mar 24, 2004
Posts: 2392

Re: [healyje] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

healyje wrote:
Overall I don't use cords that 'fuzz' for the most part and don't consider fuzz / coating in the equation except relative to my roped-soloing device (Eddy)...
where do you get that ropes? I want them!
I have managed to turn thin, slippery ropes that where really hard to hold into fuzzy fatties that got hard to feed through the device quite fast.

In reply to:
In the end I just can't and don't ascribe to the 'range of rope sizes' or 'one-size-fits-all' school of belay device selection. In fact, I think it's a poor idea in general and one borne of misplaced convenience.
One size fits all is surely a bad idea (though stuff like the edelrid zap-o-mat might lead to a "solution"), but you have to have some range, if you dont want to end up with 100 devices.

In reply to:
I want the belayer to just lock it up and I'll take care of the 'dynamic' protection of my placements if they need it.
So why do you not just give you belayer an autoblock, which us just as safe as an ATC or similar device, with the added safety function that it will still stop you fall if your belayer got knocked out due to rockfall or something similar?

I am not trying to start an internet argument, i am just curious, since i think i remember you as an oponent of autlockers.

qwert


hafilax


Feb 1, 2011, 7:40 AM
Post #49 of 55 (2801 views)
Shortcut

Registered: Dec 11, 2007
Posts: 3025

Re: [qwert] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

qwert wrote:
One of the german tests Jim Tit mentioned is probably this one:
http://www.alpenverein.de/...5d9d8468a2e73a1e29d1

I wont translate it, but here is some words about it, and a quick look at some of the numbers they got:

The DAV tested a few belay devices (Tube (looks like it was a classic ATC), various forms of 8s, munterhitch/'HMS, GriGri and TRE) in a factor 0.4 fall.

The fixed the devices to the belay, and belayed with an artificial hand, where they could adjust the hand power, which is - according to a previous study - 209N on average.
so they ran the tests with a hand power of 100N, 250N, 400N and two Persons.

They measured the forces on the top piece and that are the results:

Code
Hand force:       |   100N   |   250N   |   400N   | Person1 | Person2  
Top force GriGri| 5.9kN | 5.6kN | 5.5kN | - not tested -
Top force Tube | 2.7kN | 3.8kN | 5.0kN | 3.8kN | 4.1kN
rope slip GriGri| 9cm | 8cm | 9cm | - not tested -
rope slip Tube | 182cm | 51cm | 22cm | 101cm | 66cm

Obviously this is -as mentioned - a fixed belayer and a small fall factor, but it is safe to assume that those observations also apply for bigger stuff.
The less the belayer grabs the rope, the less force the top piece will see if you are using a dynamic device. If you know how to do this, this can be used to give a soft catch/ help bad protection to stay in.
However if you simply dont have significant force, this might result in uncontroled slipage, that will burn you hand.
On the other hand, if you have strong hands, and simply lock up the rope, you can - if we are ignoring jumping or being pulled up - produce forces quite similar to the grigri.

I would be interested on how some "increased braking strength" tubes like the ATC-XP behave in this test.
I am simply going to claim that this will increase the top force/ reduce the slipage, and that this will reduce the hand force needed to make it static, and thus that there probably are quite a few folks out there who might as well belay trad with a grigri, since it wouldnt make a difference for them anyways.

qwert
It's interesting that the top piece peak force goes down with increased hand strength using a GriGri. I wonder if pulling on the GriGri somehow keeps it from locking up as quickly?

I haven't looked at the paper but I'm assuming that the belay device is rigidly anchored in the tests. This might account for the discrepancy that healyje is talking about. The forces involved are more than enough to move a person around and, if the impulse is long enough, lift them. If the belayer is free to move I would bet that the slip figures get far smaller. I know that top roping, a lot more rope slips through when I'm anchored than when I'm not, especially with heavy climbers.


JimTitt


Feb 1, 2011, 11:26 AM
Post #50 of 55 (2766 views)
Shortcut

Registered: Aug 7, 2008
Posts: 975

Re: [j_ung] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

No idea about the marketing but I´ll be seeing the guys at a trade show on Tuesday and ask, I´ll try and score a few for selected testers as well.

Jim


healyje


Feb 1, 2011, 11:35 AM
Post #51 of 55 (859 views)
Shortcut

Registered: Aug 22, 2004
Posts: 4199

Re: [qwert] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

qwert wrote:
healyje wrote:
Overall I don't use cords that 'fuzz' for the most part and don't consider fuzz / coating in the equation except relative to my roped-soloing device (Eddy)...
where do you get that ropes? I want them!
I have managed to turn thin, slippery ropes that where really hard to hold into fuzzy fatties that got hard to feed through the device quite fast.
Mammut SuperSafe and Maxim Gliders don't.

qwert wrote:
One size fits all is surely a bad idea (though stuff like the edelrid zap-o-mat might lead to a "solution"), but you have to have some range, if you dont want to end up with 100 devices.

Again, I pass on the range, three devices covers 7-8, 9, and 10 really well and perfect to those diameters.

qwert wrote:
In reply to:
I want the belayer to just lock it up and I'll take care of the 'dynamic' protection of my placements if they need it.
So why do you not just give you belayer an autoblock, which us just as safe as an ATC or similar device, with the added safety function that it will still stop you fall if your belayer got knocked out due to rockfall or something similar?

I don't worry about the 'knocked out' argument - you are about 100 million times more likely today to be dropped repeatedly by grigri users before being held when one of them gets knocked out. There aren't a lot of people I trust with a grigri and I just find them a bit pointless for muiltipitch trad climbing which is pretty much all I do. I use one for aid soloing, but that's it.


(This post was edited by healyje on Feb 1, 2011, 11:43 AM)


airscape


Feb 2, 2011, 3:34 AM
Post #52 of 55 (811 views)
Shortcut

Registered: Feb 26, 2001
Posts: 4240

Re: [healyje] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

 
This is a most interesting discussion.


rightarmbad


Feb 2, 2011, 3:51 AM
Post #53 of 55 (804 views)
Shortcut

Registered: Mar 21, 2005
Posts: 217

Re: [airscape] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (2 ratings)  
Can't Post

I have only ever had a rope slip in my hand on one occasion.
A hard fall above the first bolt and I had just fed slack to clip the bolt and therefore my brake hand was very close to the device and the rope slipped when my hand got to the device.
At any other time, my hand does not slip.
The rope does sometimes creep through the device and my hand gets closer to the device, but unless my hand contacts the device, my hand does not slip.
I have never seen more than 4 or 5 inches in slip though.

If it is a big fall, then I have plenty of time to get my brake hand into a favorable position to create lots of braking and the rope generally doesn't slip.

Dynamic braking is achieved by body movement and letting my hand approach the device, never the rope slipping through my hand.

I don't think that I would be comfortable with a belayer that let the rope slip through their hand.


ncrockclimber


Feb 2, 2011, 6:20 AM
Post #54 of 55 (785 views)
Shortcut

Registered: Apr 6, 2006
Posts: 273

Re: [JimTitt] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

Great thread! Thanks, Jim, for posting all the useful information. I am looking forward to the Chicane coming out.

One other new device that is coming out is the Mammut Alpine Smart. It looks interesting. Like the original Smart, it is a locking assist device. The Alpine version gives you the added ability to use two ropes (both on lead and rappel) and auto-block.

I don't know if I really need another belay device (probably not!), but it is really cool to have all these options!


sp115


Feb 2, 2011, 6:22 AM
Post #55 of 55 (783 views)
Shortcut

Registered: Apr 17, 2007
Posts: 515

Re: [ncrockclimber] Testing a "Dynamic Belay" [In reply to]
Report this Post
Average: avg_1 avg_2 avg_3 avg_4 avg_5 (0 ratings)  
Can't Post

I'm looking forward to that too, should be here in the spring according to the US rep I spoke to.


Forums : Climbing Information : The Lab

 


Search for (options)

Log In:

Username:
Password: Remember me:

Go Register
Go Lost Password?



Follow us on Twiter Become a Fan on Facebook