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vivalargo


Dec 1, 2008, 9:30 PM
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Pull vrs. Drop Testing
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In reviewing most of the testing done world wide, the vast majority are slow pull tests, even though no one ever falls like this, and gear is never impacted with super heavy loading (in a real world climbing situation) via slow impact. It's like mashing a car with a hydraulic compactor, instead of driving it at speed into a brick wall. If you want to know how the car actually responds in a wreck, you have to go for the head on.

We need to encourage those with drop towers to start doing the work, tedious and involved as it is.

JL


(This post was edited by vivalargo on Dec 1, 2008, 9:31 PM)


suilenroc


Dec 1, 2008, 9:36 PM
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Re: [vivalargo] Pull vrs. Drop Testing [In reply to]
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Not sure of the point to this thread... Climbing equipment manufactures are doing drop tests and independent companies/organizations are in fact doing drop tests. Ever noticed that climbing gear is rated in kN?


(This post was edited by suilenroc on Dec 1, 2008, 9:39 PM)


Partner rgold


Dec 1, 2008, 10:36 PM
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Re: [vivalargo] Pull vrs. Drop Testing [In reply to]
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Right on, John. I wish the AAC was more active in supporting such testing. (I think it would be hard for them to be less active...)

The distinction between the value of drop testing vs, pull testing comes into sharp relief when one sees the relatively recent tests on dyneema slings, which will break in a factor-2 fall. Nylon slings of the same sort will withstand such a fall, in spite of the fact that their pull-tests give lower tensile strengths.

On the other hand, when it comes to metal gear, I think I remember Chris Harmston saying some years ago on rec.climbing that drop and pull testing yielded essentially equivalent results.

Moyers has done some interesting drop-testing on what happens when gear pulls. If I can find the reference I'll send it, or maybe someone here already has it.

Two things I think came from Moyers drop tests are

1. The rope does recover (spring back) in the interval between blowing the first piece and loading the next one down. Because of this, we can say that extracting a piece can reduce the load on subsequent pieces.

2. Tie-in knots absorb a small but not insignificant amount of the load. But not after the first fall when they have tightened up.

The Technique and Materials section of the Italian Alpine Club has carried out and extensive drop-testing program; these guys are light-years ahead of us in their knowledge of belay forces. Some of their work is available through the Canadian Alpine Club web site. I have a translated version of their report on anchor loads somewhere. Again, maybe someone here has a link.

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.


truckyme


Dec 1, 2008, 10:57 PM
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Re: [rgold] Pull vrs. Drop Testing [In reply to]
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Polymers like spectra and nylon are very sensitive to strain rates. All materials have a plastic flow rate. That means that each material has a rate at which it reacts to stresses. So, the faster that they are loaded the less time the material has to react to the stress.

During a slow pull test alot of the energy goes into deformation. where with a fast loading like a drop test the material doesn't have time to deform enough to account for all that energy (think silly putty). IIRC spectra melts at the break due to all that energy going into such small deformation and the material cannot accommodate.

Sorry if this is sorta hard to follow. I can clarify if needed.


(This post was edited by truckyme on Dec 1, 2008, 11:17 PM)


knudenoggin


Dec 1, 2008, 11:20 PM
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Re: [rgold] Pull vrs. Drop Testing [In reply to]
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rgold wrote:
The distinction between the value of drop testing vs, pull testing comes into sharp relief when one sees the relatively recent tests on dyneema slings, which will break in a factor-2 fall.
Which tests were these?
Recall that Kolin Powick's testing of "girth-hitched" HMPE slings all showed
survival of UIAA drops (near FF2)--that's a knotted sling.
cf http://www.bdel.com/...ta/qc_kp.php#current
[Kolin's 20061109 test of nylon & HMPE slings]

In reply to:
On the other hand, when it comes to metal gear, I think I remember Chris Harmston saying some years ago on rec.climbing that drop and pull testing yielded essentially equivalent results.
Not just metal gear: I know a fellow who eyed plots of force on some
nylon ruptures, and they broke at same force--rapid or slow (and I think
that Moyer's results so show). Kolin's results (op cit.) however showed
a change in which sling (of mixed-materials cases) broke, if not also force.

In reply to:
2. Tie-in knots absorb a small but not insignificant amount of the load. But not after the first fall when they have tightened up.
Hmmm, YMMV on length of fall--the knot has a fixed length of material
to yield, which percentage of fall length varies. And, then, not all tie-in
knots are created equal. (-;

In reply to:
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.
And translating to English directly touches more than just USA, as a
national-body concern (CA, UK, AU/NZ).

*kN*


majid_sabet


Dec 1, 2008, 11:20 PM
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John
Contact Mike Gibb of R4R or Tom Moyer. they have done some drop test on many climbing related gear especially daisy and cords. I have seen some of their drop test videos and does look scary.

MS


USnavy


Dec 1, 2008, 11:46 PM
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Re: [suilenroc] Pull vrs. Drop Testing [In reply to]
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suilenroc wrote:
Climbing equipment manufactures are doing drop tests and independent companies/organizations are in fact doing drop tests. Ever noticed that climbing gear is rated in kN?
That statement only has some very limited truth to it. The only things that UIAA tests dynamically are ropes and helmets (and possibly via ferrata lanyards). Biners, slings, pro, and all the like are tested with a hydraulic puller. Manufacturers generally test their gear in accordance with UIAA standards since they are generally design it to meet UIAA standards.


(This post was edited by USnavy on Dec 1, 2008, 11:47 PM)


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Dec 2, 2008, 4:17 AM
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I see some purpose in Largo's post.

Why is gear not drop tested? [If this is the line of thought he is going.]

Hardware is staticly pulled to failure. We know the manufacturers state the maximum dynamic loading (MDL) on their gear, or at least thier suggested failure load. Why not subject this gear in a drop rig with loads that have been calculated to meet and/or exceed the MDL of the piece. It's a great idea and it would be interesting to see the results of a load-to-failure drop on a piece of hardware.


adatesman


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binrat


Dec 2, 2008, 10:56 AM
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There is an ACMG guide out by Invermere BC thathas both a slow pull machine as well as a drop tower. He was once the owner of Rigging for Rescue before Mike Gibbs bought the company. He has done lots of drop tests on many things.

binrat


vivalargo


Dec 2, 2008, 11:24 AM
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Re: [epoch] Pull vrs. Drop Testing [In reply to]
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epoch wrote:
I see some purpose in Largo's post.

Why is gear not drop tested? [If this is the line of thought he is going.]

Hardware is staticly pulled to failure. We know the manufacturers state the maximum dynamic loading (MDL) on their gear, or at least thier suggested failure load. Why not subject this gear in a drop rig with loads that have been calculated to meet and/or exceed the MDL of the piece. It's a great idea and it would be interesting to see the results of a load-to-failure drop on a piece of hardware.

The climbing world would never let gear manufacturers rate a rope's fall capacities with data from a slow pull test, and yet most of the other gear and systems (cordelette, et al) are slow pulled tested even though they are subjected to falls.

Claims that slow pull and drop testing yield the same results are not terribly convincing.

JL


roy_hinkley_jr


Dec 2, 2008, 12:30 PM
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vivalargo wrote:
Claims that slow pull and drop testing yield the same results are not terribly convincing.

Actually, there's quite a bit of testing to support the validity of static pulls for most climbing gear. On things like harnesses, it's actually more brutal. All of this was discussed extensively when there was a movement afoot to create ASTM standards. That effort was abandoned when the conclusion was reached that the UIAA standards were adequate to protect companies from lawsuits, their primary purpose.

Rgold is correct that the AAC is absolutely pathetic when it comes to testing gear and improving climbing safety (cordelettes are a great example). Instead they focus money on a lame museum, a nice library, and feel-good projects and parties that don't help the majority of climbers.


vivalargo


Dec 2, 2008, 2:02 PM
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Re: [roy_hinkley_jr] Pull vrs. Drop Testing [In reply to]
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roy_hinkley_jr wrote:
vivalargo wrote:
Claims that slow pull and drop testing yield the same results are not terribly convincing.

"Actually, there's quite a bit of testing to support the validity of static pulls for most climbing gear."

I think this is probably true per individual pieces of gear - i.e., how "strong" is this SLCD or that biner. But for systems, such as belay rianchor rigging, et al, for slow pull testing to be valid it would have to have been contrasted with drop tests, with both drop and pull test results worked up into a proper statistical model, contrasted, etc. If this has actually been done, I'd very much like to see it.

"On things like harnesses, it's actually more brutal."

It's likely more brutal with any single piece of gear, though I certainly don't know for sure, nor have I seen those contrasting tests that would prove it so.

"All of this was discussed extensively when there was a movement afoot to create ASTM standards."

When, exactly, was this, and who was it who extensively discussed it? Not doubting this information, I just am totally in the dark about the facts of this.

"That effort was abandoned when the conclusion was reached that the UIAA standards were adequate to protect companies from lawsuits, their primary purpose."

Again, I think this was all in reference to individual pieces of gear, such as nuts and cams and biners and ropes. But the relative strength and performance perameters of said gear is not and has never been the topic of these long winded discussions on fall factors and whether or not we should clip through the anchor and the forces involved when falling directly onto the belay anchor and rigging for equaization and no extensions cha cha cha. Clearly, pull testing would not disclose what we need to know about the above; and I question anyone who claims that it would. How would they know that without contrasting both drop and slow pull testing?

"Rgold is correct that the AAC is absolutely pathetic when it comes to testing gear and improving climbing safety (cordelettes are a great example). Instead they focus money on a lame museum, a nice library, and feel-good projects and parties that don't help the majority of climbers.

A very crucial point, IMO. I'm going to start putting the screws to the AAC about getting this all straightened out. At the very least we could have the extensive Italian test results translated and interpreted, and perhaps use that as a starting point. We're in dire need of hard facts; and if I learned anything from the first batch of drop tests we did (with Jim at Sterling), the results were sometimes quite diferent than what we had thought all along.

JL


(This post was edited by vivalargo on Dec 2, 2008, 2:05 PM)


gunkiemike


Dec 2, 2008, 2:32 PM
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Re: [epoch] Pull vrs. Drop Testing [In reply to]
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epoch wrote:
I see some purpose in Largo's post.

Why is gear not drop tested? [If this is the line of thought he is going.]

Hardware is staticly pulled to failure. We know the manufacturers state the maximum dynamic loading (MDL) on their gear, or at least thier suggested failure load. Why not subject this gear in a drop rig with loads that have been calculated to meet and/or exceed the MDL of the piece. It's a great idea and it would be interesting to see the results of a load-to-failure drop on a piece of hardware.

I don't think I've ever seen MDL ratings...on anything. Care to point me to some from any of the major gear companies.


roy_hinkley_jr


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The ASTM climbing committee was in the mid-90s. It consisted of manufacturers, retailers (mostly REI), editors, and interested public with meetings at OR and elsewhere. Shut down after a few years. A related ASTM committee did pass standards for sleeping bag ratings and pack volume.

You're correct that UIAA/CEN/ASTM are only about individual gear, they have never tested systems. That's more of a BMC, DAV, CAI on their own thing...but not the good ol' AAC (or ACC). Occasionally a university prof or grad student does something somewhere too but it's very haphazard and often poorly researched. Rescue teams probably do more testing than anyone but a lot of that isn't useful for climbers (Moyers stuff for example). Sharing of info is a very weak point to this day.


vivalargo


Dec 2, 2008, 3:46 PM
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Re: [gunkiemike] Pull vrs. Drop Testing [In reply to]
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gunkiemike wrote:
epoch wrote:
I see some purpose in Largo's post.

Why is gear not drop tested? [If this is the line of thought he is going.]

Hardware is staticly pulled to failure. We know the manufacturers state the maximum dynamic loading (MDL) on their gear, or at least thier suggested failure load. Why not subject this gear in a drop rig with loads that have been calculated to meet and/or exceed the MDL of the piece. It's a great idea and it would be interesting to see the results of a load-to-failure drop on a piece of hardware.

I don't think I've ever seen MDL ratings...on anything. Care to point me to some from any of the major gear companies.

Man, I've never even heard of the term, "MDL." Sounds like a very workable idea but I wonder where it has been hiding all these years - and it's not like I haven't combed through most all this stuff. Apparently not well enough. Thanks to Epoch for bringing this up.

That much said, to post a valid MDL figure you would have to have drop tested to determine this, unless folks are just assigning a static pull rating to the MDL - which is total BS if so (I can hardly imagine this is the case).

Like I have said elsewhere, the reason gear manufacturers (the only folks who have UIAA approved drop towers and all the required gear) only test individual components is that's all they sell. There's no money in testing rigging systems to determine how shock loading occurs, or if this or that sling configuration equalizes or not, etc. Moreover, the closer I look the less it seems that anyone really wants to do the involved drop testing when they can do the much easier slow pull tests and fob off those numbers for most everything.

It remains an open question as to who is going to actually test what needs testing per the questions that keep surfacing on this and other sites per anchors, et al.

JL


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gunkiemike wrote:
epoch wrote:
I see some purpose in Largo's post.

Why is gear not drop tested? [If this is the line of thought he is going.]

Hardware is staticly pulled to failure. We know the manufacturers state the maximum dynamic loading (MDL) on their gear, or at least thier suggested failure load. Why not subject this gear in a drop rig with loads that have been calculated to meet and/or exceed the MDL of the piece. It's a great idea and it would be interesting to see the results of a load-to-failure drop on a piece of hardware.

I don't think I've ever seen MDL ratings...on anything. Care to point me to some from any of the major gear companies.
I guess that what I meant by the manufacturers stating the MDL is the advertised maximum load of the gear. I assume that during R&D they actually take plenty of individual pieces to complete failure.

I agree, though, with the opinion that the loading characteristics between a static pull and a dynamic pull are different.


vivalargo


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epoch wrote:
[I agree, though, with the opinion that the loading characteristics between a static pull and a dynamic pull are different.

"Opinion" is right, since I don't know that the loading characteristics between a static pull and a dynamic pull are all that different. I'm not sure anyone really knows, since you'd have to do a stack of tests using both pull methods to determine the differences. Some tests, like for extention/shock-loading would have to be dynamic tests, but for others, who knows, really?

JL


rightarmbad


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Unless some research shows up that slow pull testing, can mask a significant failure mode under dynamic conditions, then there will be no change to testing.


vivalargo


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rightarmbad wrote:
Unless some research shows up that slow pull testing, can mask a significant failure mode under dynamic conditions, then there will be no change to testing.

I think this logic is exactly backwards - and if this logic ever gets challenged in a court of law, I believe it will stand no chance because the assumption (that slow pull testing is all that is required to get a full picture of the consequences) is largely unproven.

The "research" is basically functional, real world climbing, which involves dynamic loading scenarios.
As mentioned earlier, in automotives, they don't allow accident testing to take place in a slow, hydraulic compactor - they require that cars be driven into walls, since that's an actual accident, not a replicatd accident in slow motion (compactor).

Where is the testing supporting the belief that dynamic and static loading result in such similar figures that research is required for the industry to change their ways? Who decided this, when, and on the basis of what comparative (slow pull vrs. drop testing) testing? Like I said, whoever has accepted this prima facia is almost certainly in for a rude awakening if ever challenged in court, which is the main reason companies test gear in th first place (to avoid getting sued).

I'm all but certain that no one actually knows that slow pull testing does not "mask a significant failure mode under dynamic conditions." Sure, this is the case with individual pieces of gear, such and cams and nuts and biners, which put out similar numbers if slow pulled or drop tested. In face, Colin at Black Diamond explained to me how they test SLCDs and
biners and so forth and they dop test the crap out of stuff under far harsher conditions than you could ever encounter in the field (for instance, using static cord with static tie-ins and dropping stuf a country mile - essentially TRYING to break stuff) - but, what about systems (belay systems, rigging systems, and issues like using a redirect off the belay) - these are what remaikn huge question markms for all of us.

Consider the drop tests Rock and Ice mag. did a few years ago on using a Spectra daisy chain as a belay anchor tie off. You could have slow pull tested all the components in the system - the anchor, the rigging (cordelette), the biners, the spectra daisy itself, and all would have returned high performance numbers. But when they actually dropped a 150 lb. weight onto a Spectra daisy connected directly to an anchor, shit started blowing up.

Again, the testing normally done is with individual pieces of gear, whereas systems and procedures - the topic of discussion on these threads - remain huge unknowns and are IMO not going to give up thir secrets with slow pull testing.

Enough said.

JL


(This post was edited by vivalargo on Dec 4, 2008, 10:51 AM)


yokese


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rgold wrote:
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.

Link to the Italian reports, please?.


patto


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vivalargo wrote:
rightarmbad wrote:
Unless some research shows up that slow pull testing, can mask a significant failure mode under dynamic conditions, then there will be no change to testing.

I think this logic is exactly backwards.
Scientific and engineering theory support this logic. You need to realise that slow pull testing is identical to dynamic pull testing except that the time scale is significantly expanded. For this reason slow pull testing is MORE severe in most cases than 'dynamic' pull. The material is subjected to high forces for a longer period of time.

Dynamic testing becomes more severe than static when the rate of onset of the force is larger than the rate at which the material can adjust to the new force. The force wave propagation in metal is EXTRAORDINARILY fast. For this reason metal gear is not a problem. Furthermore due to the presence of dynamic rope means that the onset of the force is (relatively) slow and smooth. The point being dynamic testing is not more severe than static.

This is of course NOT true for the rope. Even in the case of a 0m fall. If the rope isn't pulled tight beforehand then the peak force experienced by the rope is double the weight of the purpose. This is because the rope experieces a sharp edge loading profile.

Finally, I think you are missing the key difference between ROPE testing and the rest of the gear. ROPE testing isn't about testing the maximum force that it will hold, it is about testing the energy absorbing ability of the rope. It is this energy absorbing profile that determines the forces that will be exerted on the rest of the gear.


vivalargo wrote:
The "research" is basically functional, real world climbing, which involves dynamic loading scenarios.
As mentioned earlier, in automotives, they don't allow accident testing to take place in a slow, hydraulic compactor - they require that cars be driven into walls, since that's an actual accident, not a replicatd accident in slow motion (compactor).

Not really relevent. Science, engineering and common sense indicates that compactor testing has no relevance to automobile crashes. Crashes are about a car resisting/absorbing the forces produce by its own inertia. Alot more complicated than simple tensile forces, the only way to replicate it is crashes.


vivalargo wrote:
but, what about systems (belay systems, rigging systems, and issues like using a redirect off the belay) - these are what remaikn huge question markms for all of us.

There is a two good reasons why these are being heavily tested. 1. They are too variabe to construct meaningful tests. 2. They are not sold.


vivalargo wrote:
Consider the drop tests Rock and Ice mag. did a few years ago on using a Spectra daisy chain as a belay anchor tie off. You could have slow pull tested all the components in the system - the anchor, the rigging (cordelette), the biners, the spectra daisy itself, and all would have returned high performance numbers. But when they actually dropped a 150 lb. weight onto a Spectra daisy connected directly to an anchor, shit started blowing up.

Well if you create a belay without an energy absorbing component then don't be surprised if the forces start going off the scale.


vivalargo wrote:
Again, the testing normally done is with individual pieces of gear, whereas systems and procedures - the topic of discussion on these threads - remain huge unknowns and are IMO not going to give up thir secrets with slow pull testing.

You are right that there might be 'secrets' to be discovered in odd non conforming systems and procedures. However considering most single pieces are large strong enough to handle a fall of any kind, in can be concluded that more complicated systems can also handle such falls. Of course if you mean by non conforming procedures such as having no energy absorber then sure extreme forces can and do happen.

Your quest to discover more is very noble. However in my opinion there is little need to subject individual pieces to dynamic testing when slow pull is cheaper more measurable, reliable and repeatable.


maldaly


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vivalargo,
I'm sorry, but I take exception to your comment that manufacturers only test gear so we don't get sued. Bullshit. I climb and fall on the gear we make, Peter Metcalf climbs and falls on his gear, Doug Phillips climbs and falls on his gear and on and on. To say that the only reason we test gear is so we don't get sued is, ill-informed myopic and disrespectful.

Shame on you.

We test our gear to the best of our ability because we climb on it and, more importantly, our friends, including you, climb on it; and we HATE it when our friends get hurt.

We do, however, test to industry norms in part, to cover our asses and, in part, to offer comparative results between brands and models. Without an agreed upon standard there is no possible way to compare one product against another.

Whew! Now that I've got that out of my system, I'm happy to discuss if the current standards set by CE and the UIAA are appropriate. Personally, I don't think they are. The best data out there seems to indicate that the tests for metal products--cams, nuts, carabiners--are adequate but incomplete. The tests for webbing based products, however, need some work. For any test to useful, it has to be repeatable, measurable and, most importantly, relevant. It seems like recent tests--anecdotal and otherwise--have shown that tests for webbing don't really evaluate what is going on in a climbing situation. They aren't relevant and need to be revised.

The flip side of this is that we're not seeing a lot of gear failures that might be avoided by refinements in testing. Carabiners always have and always will break when the gate is open. Ropes will always get cut over an edge and climbers will still get dropped when their belayer thinks that their Cinch or Grigri is autolocking and climbers will continue to die when they set up their anchors without thinking. Refined testing and more data won't solve this plague.

Fewer accidents will happen when climbers stop chatting up the babe next to them and start thinking about what they are doing at the moment. Fewer accidents will happen when climbers worry less about how to rig the latest and most fashionable equalized, cordaletted anchor and start thinking about how to find and place anchors which are bomber and then make them multi-directional. Fewer accidents will happen when sport climbers begin to realize that the time to teach someone how to re-thread an anchor isn't when the climber arrives at the chains for the first time.

Okay, enough rant for now. I'm in Florida and a long way from any rock worth climbing so please excuse this quick fix. More later, no doubt.

Climb safe,
Mal


(This post was edited by maldaly on Dec 4, 2008, 7:40 PM)


vivalargo


Dec 4, 2008, 7:58 PM
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Re: [maldaly] Pull vrs. Drop Testing [In reply to]
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maldaly wrote:
vivalargo,
I'm sorry, but I take exception to your comment that manufacturers only test gear so we don't get sued. Bullshit."

Hold on, cowboy. I never said that preventing lawsuits was the ONLY reason companies test gear. I talk to Kolin over at BD and know what's up. I probably should have said that the threat of lawsuits - amongst other reasons - necessitates testing. In any event, no disrespect intented.

That much said, it's hard to imagine getting more resistance from people about the need to do more actual drop testing ON ANCHORING SYSTEMS, not on individual pieces of gear, for which slow pull tgesting is probably sufficient. Fact is, while I understand that companies do not sell anchoring systems, slow pull tests can contribute only so much here, as can other mechanical models from which things are being extrapolated.

The simple truth of the matter is that we don't know the real low down on something as basic as shock loading, and what kind of forces are generatred during the cascade failure of pieces in a belay anchor.

But it's late just now - I'll try and get more into this later. But for now, the big problem is that while we know the absolute holding power of many of the components of a anchor chain (nuts, cams, biners, runners, et al), our knowledge of the system is still very much lacking.

JL


altelis


Dec 4, 2008, 9:58 PM
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Re: [vivalargo] Pull vrs. Drop Testing [In reply to]
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1) you totally cheestitted that quote

2) john, your gripe hardly seems to be with the gear manufacturers, eh? holding them accountable for not testing systems that may or may not be ubiquitious or made from their products seems like you are just lashing out. perhaps your initial impulse to look towards the AAC was more appropriate. in fact all in all the beginning of this thread was far better than the end.

i must preface this next point with: i really have the utmost respect and gratitude for your work and your writing. HOWEVER, the end of this thread has not shown some of your best attributes. it has reduced you to whining and pointing blame at those who do not deserve it.

i was excited by the start of this thread and by this point feel like i may just not return. hmph.

~alex

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