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Carnage


Jan 26, 2011, 8:38 AM
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Testing a "Dynamic Belay"
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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
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Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
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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
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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
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Re: [Carnage] Testing a "Dynamic Belay" [In reply to]
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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.


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Jan 26, 2011, 1:38 PM
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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
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fully static belay and grigri belay are not the same thing.


Partner j_ung


Jan 26, 2011, 1:44 PM
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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
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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
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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
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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.


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Jan 27, 2011, 7:37 AM
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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
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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.


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Jan 27, 2011, 12:48 PM
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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
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Re: [cracklover] Testing a "Dynamic Belay" [In reply to]
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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
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Re: [mikebee] Testing a "Dynamic Belay" [In reply to]
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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
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Re: [jt512] Testing a "Dynamic Belay" [In reply to]
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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

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