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Load cell testing: How much force does a bounce test produce?
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By 20 kN
From Hawaii
Jun 12, 2012

After reading the thread from Axledavis about bounce testing, I got a bit curious as to how much force a bounce test in the real world actually produces. Two members in that thread said they bounced around in a sling, or dropped a weight in a sling, and got an impact force of around 4 kN. That seemed excessively high to me, especially considering Metolius quotes a hard bounce test at 2 kN. So I decided to replicate real-world aid bounce tests and see how much force they produce. This testing is non-conclusive; it is simply for fun. It is, more or less, a test of how much force I will inflict on pieces I test, rather than an absolute statement regarding bounce testing forces.

The point of this thread was to be as real world as possible. So I conducted this test in Yosemite, on an aid route, on aid placements (an A0 bolt ladder). I conducted the tests using all the gear I normally use on a wall, and in the exact manner I would test a placement on a wall. In every case, I tested the placement quite aggressively Ė I didnít hold back.

-I used a 5,000 lb load cell with a rated accuracy of .02%, and a computer driven strain gauge analyzer that sampled the load cell at 500Hz.

-I weigh 158 lbs

-On the tests I was wearing a rack, the rack weighed 17.5 lbs

-I was using Yates adjustable daisy chains (nylon)

-I was using Metolius wall step 8-step aiders

(1) I conducted six different tests. The first set shows an aider bounce test versus a daisy bounce test, but without a rack.
(2) The second set is the same as the first, but with a [nearly] full El Cap clean aid rack (which weighs 17.5 lbs).
(3) The last set was an absolute worst possible case scenario where I was hanging only from the load cell and no part of my body was touching the lower piece. The first test in the series showed an aggressive daisy test. The second test shows an excessively aggressive daisy test where I was literally slamming myself down onto my daisy as hard as possible. This test was more aggressive than any bounce test I would use on a wall. I was wearing the rack in both tests in this series.













The absolute highest force incurred on the top piece occurred during the last test (the excessively aggressive test,) and racked in 681 lbf. or 3.03 kN. However, that test was synthetically extreme. The highest force incurred during a realistic aggressive bounce test was 643 lbf. or 2.86 kN. But again, I was hanging solely from the piece which is not realistic in a wall climbing scenario. So the highest force incurred using an aggressive daisy bounce test that is realistic to a wall climbing scenario is 618 lbf. or 2.75 kN.

So my testing seems to imply that a hard bounce test in your aiders will produce 400-550 lbf and a hard bounce test directly on your daisy chains will produce 500-600 lbf. I find it unlikely that I would be able to produce a higher impact force using conventional nylon pocketed daisy chains simply because I was bouncing around hard enough that if I were fified into a pocketed daisy, the aggressive bouncing would likely result in the fifi coming out of the pocket. However, it is possible that using a Dyneema daisy chain would result in a higher impact force; maybe I can test that in the future.


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By Newton
From Colorado Springs, CO
Jun 12, 2012
Monastery action.

This is awesome! Thanks for testing. That route looks kinda slabby in the pic; do you think you could get higher forces if you were bouncing under a roof?


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By Aric Datesman
Jun 12, 2012

As one of those who gave data previously, I must say clearly you don't weigh enough or have enough strength to give useful data on this. Maybe *you* can only hit sub-3kN, but I've measured 4kN+. I do like your fancy charts, but have to say I have reservations about using a 22kN load cell to measure on the bottom 10% of its range. Typically bad form, IME. As is stating something as definitive sounding as "more aggressive than I wouluse on a wall", when you've done... How many is it now? Two? Three? Not sure that qualifies you to speak authoritatively on the subject. To put it a friendlier way, RGold puts it at ~4kN and my data agrees, so....


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By Steve86
Jun 12, 2012

Completely unrelated to this, how did you attach that spreader bar to your aiders? I've got the same ladders and hadn't previously considered an after-the-fact spreader bar but now I'm intrigued. If you've posted this elsewhere I must have missed it. Thanks.


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By Aric Datesman
Jun 13, 2012

Oh, and why bump the old thread to point at a new one rather than just answering the question where it was asked?


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By Princess Mia
From Vail
Jun 13, 2012
Chillin' at City of Rocks

Very interesting from an engineering perspective. It would be fab to have more rigorous testing at steeper angles and with climbers of different sizes.
Nonetheless the information from different testers do suggest forces from 2-4 kN.


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By Alex Quitiquit
From Salt Lake City
Jun 13, 2012
meow

Nice work on your analysis. It's interesting to see the different load scenarios. This type of data analysis helps keeps climbers safe, at least the ones who are methodical with their protection. Regardless of the bump or not, an interesting post...

Maybe do the same test with well placed nuts and cams... I would like to see what kind of spikes of load force might occur.


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By NC Rock Climber
From The Oven, AKA Phoenix
Jun 13, 2012
tanuki

Very interesting information. Thanks for posting up. I appreciate this and the other testing that you have done with your load cell.


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By 20 kN
From Hawaii
Jun 13, 2012

Steve86 wrote:
Completely unrelated to this, how did you attach that spreader bar to your aiders? I've got the same ladders and hadn't previously considered an after-the-fact spreader bar but now I'm intrigued. If you've posted this elsewhere I must have missed it. Thanks.

I added them myself. I just got some PVC, threaded it with webbing, and sewed the webbing to the aider. I than sewed another piece of webbing over the stitches to provide increased abrasion resistance.


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By cjdrover
From Somerville, MA
Jun 13, 2012
Taken at MWV Icefest 2014.

Aric Datesman wrote:
As one of those who gave data previously, I must say clearly you don't weigh enough or have enough strength to give useful data on this. Maybe *you* can only hit sub-3kN, but I've measured 4kN+. I do like your fancy charts, but have to say I have reservations about using a 22kN load cell to measure on the bottom 10% of its range. Typically bad form, IME. As is stating something as definitive sounding as "more aggressive than I wouluse on a wall", when you've done... How many is it now? Two? Three? Not sure that qualifies you to speak authoritatively on the subject. To put it a friendlier way, RGold puts it at ~4kN and my data agrees, so....


Wow. Douche-iest response award! Different people, slightly different results. Not a big deal, and not an attack on your work. You sound like a kid arguing on the playground.

OP clearly stated:
20 kN wrote:
This testing is non-conclusive; it is simply for fun. It is, more or less, a test of how much force I will inflict on pieces I test, rather than an absolute statement regarding bounce testing forces.


@ 20 kN: Thank you, great contribution (especially since I also weigh about 158...)


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By The Lingering Fart
Jun 13, 2012

Aric Datesman wrote:
As one of those who gave data previously, I must say clearly you don't weigh enough or have enough strength to give useful data on this. Maybe *you* can only hit sub-3kN, but I've measured 4kN+. I do like your fancy charts, but have to say I have reservations about using a 22kN load cell to measure on the bottom 10% of its range. Typically bad form, IME. As is stating something as definitive sounding as "more aggressive than I wouluse on a wall", when you've done... How many is it now? Two? Three? Not sure that qualifies you to speak authoritatively on the subject. To put it a friendlier way, RGold puts it at ~4kN and my data agrees, so....


Stop. Breathe deep. You don't need to freak out over every little field test, especially where the tester admits the test is not conclusive and just for fun.


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By Jake Jones
From The Eastern Flatlands
Jun 13, 2012
Me and the offspring walking back to the car after a day of cragging.

Aric Datesman wrote:
As one of those who gave data previously, I must say clearly you don't weigh enough or have enough strength to give useful data on this. Maybe *you* can only hit sub-3kN, but I've measured 4kN+. I do like your fancy charts, but have to say I have reservations about using a 22kN load cell to measure on the bottom 10% of its range. Typically bad form, IME. As is stating something as definitive sounding as "more aggressive than I wouluse on a wall", when you've done... How many is it now? Two? Three? Not sure that qualifies you to speak authoritatively on the subject. To put it a friendlier way, RGold puts it at ~4kN and my data agrees, so....


So, basically what you're saying is that you suffer from PID (pompous internet disorder) and that you consider RGold to be a definitive source of credible information- which I would not argue. The guy has been doing it forever and knows his shit. You also appear to be saying that if RGold came to a sudden halt, it would take a four man team one solid week to dig you out of his ass. Especially considering that your head is so unjustifiably big.


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By Leeroy
Jun 13, 2012

Aric Datesman wrote:
As one of those who gave data previously, I must say clearly you don't weigh enough or have enough strength to give useful data on this. Maybe *you* can only hit sub-3kN, but I've measured 4kN+. I do like your fancy charts, but have to say I have reservations about using a 22kN load cell to measure on the bottom 10% of its range. Typically bad form, IME. As is stating something as definitive sounding as "more aggressive than I wouluse on a wall", when you've done... How many is it now? Two? Three? Not sure that qualifies you to speak authoritatively on the subject. To put it a friendlier way, RGold puts it at ~4kN and my data agrees, so....



Who pissed in your cheerios Aric?


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By Ryan Williams
Administrator
From London (sort of)
Jun 13, 2012
El Chorro

Aric Datesman wrote:
As one of those who gave data previously, I must say clearly you don't weigh enough or have enough strength to give useful data on this. Maybe *you* can only hit sub-3kN, but I've measured 4kN+. I do like your fancy charts, but have to say I have reservations about using a 22kN load cell to measure on the bottom 10% of its range. Typically bad form, IME. As is stating something as definitive sounding as "more aggressive than I wouluse on a wall", when you've done... How many is it now? Two? Three? Not sure that qualifies you to speak authoritatively on the subject. To put it a friendlier way, RGold puts it at ~4kN and my data agrees, so....


Your constant pissing contest with 20kn is getting old. He made it completely obvious that this test was for fun. He did it to find out how much force HE would create. I weigh exactly 158 lbs. so I'm happy to have that information. It is much more relavent to me than how much force some 200 pound guy can create on his awesomely acurate load cell.

Please, do take everyones advice and just leave the guy alone. We're tired of your nonsense.


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By Darren Mabe
From Flagstaff, AZ
Jun 13, 2012
wham bam hand jam. Wrapping up the final moves of Twist of Fate, Oak Creek Canyon. <br /> <br />photo: Blake McCord

Besides, Aric, one of us might just start pickin apart one of your tests...


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By Aric Datesman
Jun 13, 2012

Let me put it this way:
1. His methodology is flawed and his results are half of what they should be
2. Incorrect information is not *good* information

So if that gets me the douchebag award, so be it.


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By Aric Datesman
Jun 13, 2012

Darren Mabe wrote:
Besides, Aric, one of us might just start pickin apart one of your tests...


Go right ahead.


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By Ben Gordon
From La Canada, CA
Jun 13, 2012

Thanks 20kn. I am more of a lurker here but I always really enjoy these kind of analyses. As a new climber I am always curious about the ball park of forces that gear can take and how much force my body generates.


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By Jake Jones
From The Eastern Flatlands
Jun 13, 2012
Me and the offspring walking back to the car after a day of cragging.

Aric Datesman wrote:
Incorrect information is not *good* information So if that gets me the douchebag award, so be it.

That doesn't get you the douchebag award. Your crap tone and condescending words do. You can disagree with someone and be critical of someone's information without reacting the way you did- and you know it. So does every other poster that called you out for it. Do you have a personal beef with this guy, or are you being a shitdick for the hell of it?


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By Alicia Sokolowski
From Brooklyn, NY
Jun 13, 2012
Hanging out waiting for Die Antwoord to come on stage

Aric Datesman wrote:
Let me put it this way: 1. His methodology is flawed and his results are half of what they should be 2. Incorrect information is not *good* information So if that gets me the douchebag award, so be it.


He said it was for fun, so drop the hysterics please.

I found it interesting and would welcome more from 20kN.


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By BurtMachlan
Jun 13, 2012

Aric Datesman wrote:
As one of those who gave data previously, I must say clearly you don't weigh enough or have enough strength to give useful data on this. Maybe *you* can only hit sub-3kN, but I've measured 4kN+. I do like your fancy charts, but have to say I have reservations about using a 22kN load cell to measure on the bottom 10% of its range. Typically bad form, IME. As is stating something as definitive sounding as "more aggressive than I wouluse on a wall", when you've done... How many is it now? Two? Three? Not sure that qualifies you to speak authoritatively on the subject. To put it a friendlier way, RGold puts it at ~4kN and my data agrees, so....


Sounds like you are incapable of giving an unbiased response since apparently 20kn hurt your feelings previously.


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By Aric Datesman
Jun 13, 2012

Jake Jones wrote:
That doesn't get you the douchebag award. Your crap tone and condescending words do. You can disagree with someone and be critical of someone's information without reacting the way you did- and you know it. So does every other poster that called you out for it.


So noted.

Jake Jones wrote:
Do you have a personal beef with this guy, or are you being a shitdick for the hell of it?


Yes, I have a beef with him. Mostly centered on his habit of talking out his ass in an authoritative manner about things he's not qualified to comment on and spreading incorrect and potentially dangerous information. I also think he's a selfimportant prick, but would overlook that if he's stop the other stuff.


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By Aric Datesman
Jun 13, 2012

BurtMachlan wrote:
Sounds like you are incapable of giving an unbiased response since apparently 20kn hurt your feelings previously.


What does any of that have to do with his methodology being flawed and results incorrect?


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By BurtMachlan
Jun 13, 2012

Aric Datesman wrote:
What does any of that have to do with his methodology being flawed and results incorrect?


I just think your crush on 20kn is cute... apparently he left you for another guy and now you are upset?


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By Jake Jones
From The Eastern Flatlands
Jun 13, 2012
Me and the offspring walking back to the car after a day of cragging.

Aric Datesman wrote:
So noted. Yes, I have a beef with him. Mostly centered on his habit of talking out his ass in an authoritative manner


Perhaps, but not in this case.
"This testing is non-conclusive; it is simply for fun."
Nothing authoritative about that.

Aric Datesman wrote:
about things he's not qualified to comment on

Not qualified to comment on. So, let's say I make dynamic rope, but I'm not a climber. Am I qualified to comment on the dynamic properties of a rope? Gray area at best. He's commenting on the loads that were recorded on a load cell. He's very forthright with the information and how he arrived at it. It's not NASA material, but for the layman, it's pretty thorough. Do you really have to be a hardcore Yosemite A5 guy with two decades in to know how to administer a load test on a piece of equipment? I lean toward no. Now, would the above experience help bring more accuracy to a test? Certainly. But that's not your argument.
Aric Datesman wrote:
and spreading incorrect and potentially dangerous information.


Yes, that deviation in test results is truly life-threatening. The inability of new aid climbers to decipher whether they are light or heavy and whether or not a bounce test will yield 3 or 4kn has left many an aiding n00b in the most dire of circumstances. Or... maybe it's not that big of a deal. Maybe heavier climbers that carry larger racks know that they're going to put more force on placements.
Maybe you're looking for any excuse to jump someone's shit because you don't particularly jive with their online persona.

Aric Datesman wrote:
I also think he's a selfimportant prick, but would overlook that if he's stop the other stuff.


Ah yes, the meat of it all. You should have led with this statement and omitted the rest, because it's all nonsensical bullshit. You find someone whom you've never met (I'm assuming- logical. It is afterall an internet forum) to be loathesome and self-important; perhaps even unjustifiably arrogant with his goddamned load cell and his tests with no experience to back them! How dare he!! You'd "overlook" it. I'm sure the underling internet peasants would be grateful. LOL. There's a saying man: If you meet three or more assholes in a day, they're probably not the asshole. Settle down and stop being a turd in a punchbowl. It's gonna give you an anurism one day. Then you won't be able to be a hardman anymore.


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By Darren Mabe
From Flagstaff, AZ
Jun 13, 2012
wham bam hand jam. Wrapping up the final moves of Twist of Fate, Oak Creek Canyon. <br /> <br />photo: Blake McCord

i think 20kN's test and results are no more or less quick and dirty than Aric's:

Aric Datesman wrote:
FWIW RGold, playing around with a load cell I was hitting ~4kN bouncing around on a shoulder length dyneema sling done up as a foot loop (I'm a hair under 200 without gear). Was just curious, so didn't record any logs of the data though.


2, 3, 4 kN. whatever.

the OP is psyched and was motivated enough to take the time to do all that and share it.


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