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vivalargo


Dec 5, 2008, 9:59 PM
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Re: [roy_hinkley_jr] Pull vrs. Drop Testing [In reply to]
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This from the Beal Rope web site:

"The Italian Alpine Club has conducted numerous practical tests, has filmed them, and has measured the loads all along the security chain. On the basis of these results Dr. Bedogni has established a mathematical model allowing the calculation of the loads developed along the security chain in all configurations."

This info apparently ended up in a document or treatise, and we definately need a translation of same.

JL


(This post was edited by vivalargo on Dec 5, 2008, 10:01 PM)


vivalargo


Dec 5, 2008, 10:18 PM
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Re: [vivalargo] Pull vrs. Drop Testing [In reply to]
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http://www.alpineclubofcanada.ca/services/safety/forms/BelayTechniques.doc

http://personal.strath.ac.uk/andrew.mclaren/Turin2002/CD%20congresso/Computer%20mathematical%20models.pdf

VERY bad translations of some of the Italian work.

JL


brenta


Dec 6, 2008, 5:57 AM
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Re: [vivalargo] Pull vrs. Drop Testing [In reply to]
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If the work by the Italian CCMT is this, http://www.caimateriali.org/...odiAssicurazione.PDF, I think I can help. It will take a while, though. Probably a month. Is it possible to attach a PDF file to a post?

The two links above are related to the contents of the booklet, but both predate it. The second, is the paper that Bedogni presented at the 2002 Conference on Nylon and Ropes (http://www.caimateriali.org/index.php?id=31). It's been a while since I looked at this and other papers on simulating belay systems. As I get older, my memory gets less reliable, but I seem to recall that I had reservations on how the slippage of the rope through the carabiner was modeled. Pavier does a better job on that count, but then throws in a magic adjustment in the equations to allow their forward integration to yield meaningful results. I hasten to say that this is not my field of expertise, but I got the impression that there's work left to do.

(This post was edited by brenta on Dec 6, 2008, 6:04 AM)


jt512


Dec 6, 2008, 7:43 AM
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Re: [brenta] Pull vrs. Drop Testing [In reply to]
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brenta wrote:
Is it possible to attach a PDF file to a post?

Apparently you can, but it has to be < 150 kB.

Jay


(This post was edited by jt512 on Dec 6, 2008, 7:44 AM)
Attachments: StandardEqn.pdf (93.2 KB)


Partner rgold


Dec 6, 2008, 8:16 AM
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Re: [brenta] Pull vrs. Drop Testing [In reply to]
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brenta wrote:
If the work by the Italian CCMT is this, http://www.caimateriali.org/...odiAssicurazione.PDF, I think I can help. It will take a while, though. Probably a month. Is it possible to attach a PDF file to a post?

Brenta, I'd pay to have a good English translation of this! In fact, I think I'll get an estimate from our local technical translation service...

Maybe I (we) could get the AAC to host it on their site, since it is much bigger than the .pdf limit here. If it generated some traffic, it might help to pursuade them to attend to climbing safety studies.


greatgarbanzo


Dec 6, 2008, 8:19 AM
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Re: [suilenroc] Pull vrs. Drop Testing [In reply to]
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So... you are saying that drops= KN strength and dead weight= lb?

Oh boy.


greatgarbanzo


Dec 6, 2008, 8:21 AM
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Re: [rgold] Pull vrs. Drop Testing [In reply to]
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Hey man! if you can find a way to get me that report I will translated for you.

I am super interested on the subject.


jt512


Dec 6, 2008, 8:23 AM
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Re: [greatgarbanzo] Pull vrs. Drop Testing [In reply to]
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greatgarbanzo wrote:
So... you are saying that drops= KN strength and dead weight= lb?

Oh boy.

Let's not go there in this thread, ok?

Jay


vivalargo


Dec 6, 2008, 8:36 AM
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Re: [jt512] Pull vrs. Drop Testing [In reply to]
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Yo, Greatgarbonzo. ¿Donde en Venezuela vive usted? ¿Maricaibo? Eyyyy, calor! La mayor parte de mi vida familiar en Valencia. Sería fantástico si usted podría traducir el documento italiano. Buena suerte.

LARGO


Partner rgold


Dec 6, 2008, 9:57 AM
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Re: [greatgarbanzo] Pull vrs. Drop Testing [In reply to]
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greatgarbanzo wrote:
Hey man! if you can find a way to get me that report I will translated for you.

I am super interested on the subject.

Just click the link and download the .pdf.


brenta


Dec 7, 2008, 8:06 AM
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Re: [rgold] Pull vrs. Drop Testing [In reply to]
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Jay, thanks!

Rgold, I'm about one third through the ordeal. Maybe the one-month estimate was a bit too conservative. I'd be curious to know the estimate by the technical translator. I'd guess $1000 or thereabout.

Like everybody else here, I'd like to see a greater involvement of the AAC in these matters. I like the idea of having the Italian Alpine Club study hosted on the AAC site. I presume the authors should be contacted, especially if the English version is to incorporate the figures.

Let me know if you want to see drafts of the translation.

(This post was edited by brenta on Dec 7, 2008, 9:27 AM)


greatgarbanzo


Dec 7, 2008, 9:40 AM
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Hello there!

Are you already working on the translation of the Italian article?

I am already working on it and thought that it would be kind of dumb to do it twice rigth?

Care to share the burden? We can do like half and half!

Anyhow, if you are like really busy... well, dont worry, I will get it done pretty soon, is not like I NEED the help...

Let me know your thoughs.


brenta


Dec 7, 2008, 12:37 PM
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Re: [greatgarbanzo] Pull vrs. Drop Testing [In reply to]
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Greatgarbanzo, I've gotten to page 18 so far. I'll be glad to collaborate. I've translated the tables and the figure captions, but I've done nothing with the graphs and photographs.

I'm typesetting the translation with LaTeX. This allows me to follow the original very closely (it is also typeset with LaTeX) while adding hyperlinks to the document (something missing from the original). I'm striving for a literal translation. As a result, some of it sounds a little stilted, but I'm going to worry about that at a later time.

(This post was edited by brenta on Dec 7, 2008, 5:17 PM)


greatgarbanzo


Dec 7, 2008, 7:46 PM
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Allrigth!

In that case, since you are way ahead of me, just let me know the pages you would like me to translate.

Then, I could just send you an email with the translated text so that you can add it to whatever you are doing.

I´ll do all the graphs and photographs! dont worry about those!


brenta


Dec 7, 2008, 8:25 PM
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Very well! Why don't you start from Chapter 2? I already have the bibliography page.


vivalargo


Dec 9, 2008, 3:37 PM
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One of the things folks could do who have a slow pull rig is to start testing the various rigs used to connect (and equalize) 3 placements into an anchor array - cordelette, equalete, et al. Might reveal some secrets.

JL


tugboat


Jul 19, 2011, 10:39 PM
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Re: [roy_hinkley_jr] Pull vrs. Drop Testing [In reply to]
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wow...lots of opinions and info to read thru and absorb here. I still need to go thru all the post, but i thought i would give my two cents that i collected from when i started my company. I bought a pull tester and started the testing after getting my hands on the UIAA standards and methods for testing manual. I was surprised at the time that all the UIAA certs of the time called for relativley slow hydraulic type pulls and not dynamic tests.

So i consulted with several structural engineers at the time. My main question was; "is the force i receive from my slow hydraulic pull representative of a dynamic force number?".... Basically they said "yes"... they replied "a force is a force is a force no matter how you get there". Now in terms of general physics i understand what they are saying; eg 'if the webbing breaks at 5000lbs with a slow steady load, it willl break at the same number when it hits that number dynamically (in general....my qualification added)

BUT.... Over many years of busting sewn goods and harnesses i've come to learn that there is other variables going on that come into play when testing things at slower or faster rates. some of these are, but not limited to; heat genrated over time and its dissipation and how it impacts the sewn joint. The settling of fibers in differnet forms over differnet time periods, the legth of time itself that the product is exoposed to the load....and so on.

Now some of these issues are significant variables to be investigated for climging and other industrys' purposes and some are not. Spectra's heat properties come to mind.

I will restrain with my comments here so as not to show ignorance to those who know much more than myself regarding these issues.

On the otherhand,...when i started building stuff, i needed basic numbers to work with and basic standards to build to... UIAA and its standards and methods combined with my engineers' explanations at the time sufficed.

But i do beleive that there are "dynamic" issues in certain scenarios that need to be examined and understood.


jbrown2


Jul 20, 2011, 8:00 AM
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Re: [rgold] Pull vrs. Drop Testing [In reply to]
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It would be very helpful to get their reports translated from Italian. I begged the AAC to do this with little or no results that I'm aware of. It is really close to a scandal that such thorough work has not found its way to an international audience

------

Google Translate.


Partner rgold


Jul 20, 2011, 8:15 AM
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Google translate does such a bad job it is hard to tell what the reports say. Both climbing and engineering terminology are not dealt with. Plus GT typically doesn't operate on tables and graphs.


tugboat


Jul 20, 2011, 9:45 AM
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Re: [rgold] Pull vrs. Drop Testing [In reply to]
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Actually, i think one of my main questions to the engineers was "does a slow pull force represent what will effect the climber/performer vs a dynamic force?"....and thats where they were emphatic that a force is a force. The variables i see in this case are time exposed to the force.... but the question still remains as to how this effects products.


Partner rgold


Jul 20, 2011, 10:25 AM
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Re: [tugboat] Pull vrs. Drop Testing [In reply to]
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Of course a force is a force. But your engineers, as far as I know, are wrong about there being no difference in whether the force builds up slowly over a relatively long period of time or builds up over very short intervals.

They should know, just for one example, that things like the magnitude of viscous damping depends on velocity, and that, mysterious as frictional effects are, there seems to be a difference between static and sliding friction.

They should also know that inertial effects might be significant, as in pulling paper towels off a roll slowly without separating them as opposed to a rapid snap that separates a sheet.

I have seen tests on sliding-X load distribution that reached contradictory results depending on whether the tester used slow pull or weight-dropping techniques. Differing friction behavior under these different types of loads might have accounted for this. And we've all seen videos of dyneema slings breaking under dynamic impact loads when nylon slings do not, even though slow-pulling determines dyneema is stronger than nylon.

If you want to know what might happen to climbing gear under leader falls, I suspect dynamic loading is the only way to get even first approximations.


tugboat


Jul 20, 2011, 9:21 PM
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yup...Rgold... i agree with you. thats why i "qualified" what they said in my post. At the time, like i said, i didn't understand why the UIAA testing procedures were almost all non dynamic pulls.... now i know why, and understand more about how dynamic loads can change the test...


tugboat


Jul 20, 2011, 11:27 PM
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In reply to:
If you want to know what might happen to climbing gear under leader falls, I suspect dynamic loading is the only way to get even first approximations.

Rgold... i would think that due to several factors "first approximations" are better achieved by using one's testing bed and load cell to get first impressions of one's product. When working on a new product, design, or variation, drop testing hundreds of samples just doesn't make sense.

First i would nail down the basic loading strength with my pull tester (this can be hundreds of pulls just on one given pick point out of 25!). Then i take those samples and build a full prototype. Then, back to the testing bed and more neccessary adjustments are made.

Finally once the product is proven at this stage, i would go to the drop testing step. Drop testing requires a much higher work load and time alotment than pulltesting. A single drop test, depending on one's facility, can take a full days work. Whereas, pull testing and tweaking samples of a new product can yield tens of tests and variations in a day. This process can be critical if one is working on a completly new design.

Its a matter of praticality and manufacturing process.

But in the end...i agree,... the product, should be drop tested.

Just food for thought...

Peace...


JimTitt


Jul 21, 2011, 12:56 AM
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rgold wrote:
Of course a force is a force. But your engineers, as far as I know, are wrong about there being no difference in whether the force builds up slowly over a relatively long period of time or builds up over very short intervals.

They should know, just for one example, that things like the magnitude of viscous damping depends on velocity, and that, mysterious as frictional effects are, there seems to be a difference between static and sliding friction.

They should also know that inertial effects might be significant, as in pulling paper towels off a roll slowly without separating them as opposed to a rapid snap that separates a sheet.

I have seen tests on sliding-X load distribution that reached contradictory results depending on whether the tester used slow pull or weight-dropping techniques. Differing friction behavior under these different types of loads might have accounted for this. And we've all seen videos of dyneema slings breaking under dynamic impact loads when nylon slings do not, even though slow-pulling determines dyneema is stronger than nylon.

If you want to know what might happen to climbing gear under leader falls, I suspect dynamic loading is the only way to get even first approximations.

You underestimate us!
We do know the difference between the application speed of loads and even have a name for it. Rate of strain graphs are commonplace for most materials.
And we know a lot about friction as well!

The standards and their tests are based on a mixture of theory and practical experience, we can use an item which has for many years giving trouble-free to set a standard which to the normal climber may seem a bit peculiar!

The impact speeds encountered in climbing are generally so low in engineering terms that rate of strain has little relevance except in karabiners, textiles are a bit different and here one would expect the experience gained in drop tests to guide the design.

To understand what is happening in a fall drop testing is useful but expensive and innacurate. Pull testing on the other hand is cheap and repeatable and for hardware isthe test of choice as the system defines them as a non-dynamic part. Only dynamic elements where the standard limits the maximum force are tested dynamically.

There is no repeatable and accurate drop test available as there is no standardised rope to test with, a matter long discussed to no effect for technical reasons. We have ways to work around this but none are good enough to be acceptable to any standards organisation and one still needs to take the results with a healthy sceptiscism!
And one then has to ask, "what drop test"? The UIAA test drop distance was set on the pragmatic basis of the drop towers available and the height of a standard industrial unit and is of no particular importance, to achieve "proper" drop results we are going to have to be building 200m high towers to get worst case with commonly used 70m ropes.

And despite what another poster wrote, ropes used to be tested under slow pull and my first three ropes were certified using this system.

Jim


tugboat


Jul 21, 2011, 1:21 AM
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Well formulated thoughts and writing Jim,.... thanks for composing such a succint answer.

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