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adatesman
Jun 16, 2009, 12:41 AM
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yokese
Jun 16, 2009, 12:44 AM
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adatesman wrote: yokese wrote: I had a bit of free time and already started parsing the previous page into a excel file (or any other program that accepts csv files). Just FYI I'll be uploading my excel file in the next hour or so, so unless you have that much free time...
Oh, thanks.
I'll grab a coffee then. 
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healyje
Jun 16, 2009, 12:53 AM
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adatesman wrote: curt wrote: philbox wrote: healyje wrote: It would take some work and expense, but I would think it would be possible to make a statically-positioned test jig that is epoxy-faced with rough, natural granite from a headstone / countertop company and to also angle the bottom of the jig in a degree or two so it isn't dead parallel - and then do a dynamic drop test. That would be about as close to real-world conditions as you could get. Would likely take some financial assistance and time, however. To what purpose would this test jig be of use. There would be no way that any test would be repeatable. Rock is way too varied even individual pieces. The only true test is to make the test as repeatable with consistent materials that the test jig is made out of i/e steel with a known pattern. I agree. While you might get some additional insight into how the cams perform against that particular rock type, the CE/UIAA ratings and tests are done with textured steel plates. So, it certainly seems best to stick with those. Curt FWIW this topic got tossed about a year or two ago (I forget whether it was here on RC or over on ST), and Mal@Trango chimed in that he had problems using rock for the fixture as it would crack or wear out quickly. I'll see if I can find the post.... EDIT- Wow, that was quick. I threw "crack fixture stone" into the search on ST and the only thread it threw back was exactly the one I was looking for. Be sure to scroll up for the rest of the discussion, as it was specifically about how to build a crack fixture for testing cams. Link to ST post
Well then just surface the steel plate to the equivalent of a medium file so there's no longer any question of the friction involved and still toe the plates in a degree or two so they aren't dead parallel and then dynamically drop test a bunch of them. That would play to the Aliens' strength and between that and drop testing eliminate any lingering quibbles about the testing.
As for 'axles bending because they're slipping' - do you really care why the axles are bending below the units' rated strengths? And if any of the proponents of that theory can, I'd appreciate them explaining to me how the slipping bends axles as opposed to the reverse.
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josephgdawson
Jun 16, 2009, 1:07 AM
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blondgecko wrote: josephgdawson wrote: Correct me if I am wrong, but I would guess rock has a higher friction coefficient that the metal he is using in his rig to hold the cams while pulling on them. Coefficient of friction between aluminium and mild steel: 0.61 Coefficient of friction between aluminium and rock: varies, but around 0.3 on average Draw your own conclusions.
That is fascinating and counter intuitive, at least to non-experts. I stand corrected.
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ptlong
Jun 16, 2009, 1:25 AM
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One interesting perspective is to compare the failure loads with the ratings of a comparable cam. For example the Metolius TCUs are rated at 5kN, 8kN, and 10kN for cams that are comparable in size to blue and black Aliens, green Aliens (too bad their there are no samples), and yellow and larger Aliens, respectively.
Looking at it in this way only three samples tested below their TCU-comparable levels: two yellows (at 99% and 93%) and one black (at 90%).
While this isn't an excuse for an apparent failure for Aliens to meet their own specifications it is actually somewhat encouraging in terms of their useability.
I have to take exception with whomever said the only true test is a UIAA jig. It may be more repeatable in the lab but obviously what matters most is what happens in the field. To the extent that the test jig represents that reality faithfully is another question.
(This post was edited by ptlong on Jun 16, 2009, 1:26 AM)
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hafilax
Jun 16, 2009, 1:27 AM
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It would surprise me if friction could be described by a single parameter over the entire range of normal forces in a pull test. The deformation of the lobes into the holder has to have an effect otherwise surface roughness wouldn't matter (and maybe it doesn't).
Rock is incredibly variable. If there is a direct relationship between the friction between surfaced steel and different rock types then building rock surface holders just adds complexity with no real advantage in the end.
I guess the major difference between rock and steel would be crystal breakage and compression of the stone. Those would be rock failure modes and wouldn't be appropriate tests of cam strength. It would probably be pretty straight forward to extrapolate the effects of the forces from a cam on rock.
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adatesman
Jun 16, 2009, 1:39 AM
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angry
Jun 16, 2009, 1:49 AM
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Trying to put down just the pertinent facts.
Tests 10, 11, and 13 appear to be missing.
Test 3 had a braze failure at 9.34 with a rated strength of 12.01
Test 7, the black alien, had a head failure at 6.64kn and slipped out at 5.26. It should have held 8.27
Of the 21 Aliens tested, 14 of those failed below their rated strength. Of those 14 that failed below their rating, 1 had a braze failure. It was test 3, the yellow alien mentioned above.
Of the 21 aliens tested, 16 slipped out of the fixture either above or below the rating.
Of the 21 tested, 2 failed below their ratings on the "failure mode of stem test" those were 3 and 7.
To me, this is incredibly confidence inspiring. The worst of the aliens tested held loads greater than a fall would have generated and the rest held more than they were rated for.
Aric, I know you're trying to alert us to a safety issue but really, you've proven the reliability of aliens.
Clearly they are tested on a different surface than you've got and that accounts for all but 2 of the failures. Those failures are somewhat concerning if you're in a place where you've got to belay off a single cam and a factor 2 is possible. Otherwise, everything looks great.
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ptlong
Jun 16, 2009, 2:03 AM
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adatesman wrote: ptlong wrote: I have to take exception with whomever said the only true test is a UIAA jig. It may be more repeatable in the lab but obviously what matters most is what happens in the field. To the extent that the test jig represents that reality faithfully is another question. That was probably me and was most likely just me being imprecise with my language... What I meant was that the UIAA test is the only standardized test we have and until better one comes along we're kinda stuck with it. I agree that it doesn't exactly represent real-world usage or placements, but it seems to do a fairly good job of testing strength of the components. IMO the fact that there aren't more failures in the field is likely a result of fall forces typically being significantly lower than what the gear is rated for, so for it to happen you need not only bad gear but also a particularly bad fall.
It was actually Philbox, not you.
These samples do not include any ultra-low load failures. Below Alien specifications? Yes. But they're pretty comparable to Metolius TCU and Master Cam strength ratings. There may well be really bad Aliens out there but this particular casting of the net failed to bag any, at least in terms of the pull tests.
The problem of misdrilled axle holes is a different issue that requires more investigation.
edit: Have you noticed a correlation between axle hole alignment (predicted cam angle at jig setting) and failure load?
(This post was edited by ptlong on Jun 16, 2009, 2:05 AM)
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angry
Jun 16, 2009, 2:24 AM
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It's definitely a matter of perception.
I'm not here to argue that Aliens are doing something right or wrong, or to defend them. I just love the pieces and want them to catch a fall.
After reading this, I believe they will.
Certainly with the failure modes and standard deviation among the failures, they wouldn't pass muster in a larger scale operation.
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adatesman
Jun 16, 2009, 2:24 AM
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adatesman
Jun 16, 2009, 2:27 AM
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currupt4130
Jun 16, 2009, 2:46 AM
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angry wrote: It's definitely a matter of perception. I'm not here to argue that Aliens are doing something right or wrong, or to defend them. I just love the pieces and want them to catch a fall. After reading this, I believe they will. Certainly with the failure modes and standard deviation among the failures, they wouldn't pass muster in a larger scale operation.
After reading angry's argument I'm leaning with him.
Aric, I thoroughly enjoy reading your tests. I'm a civil engineering student at Virginia Tech but have always had an interest in this kind of testing and destruction, even before I was in civil eng.
Anyway, I got a chance to look at your pull test rig at the Rendezvous and was quite impressed.
Some things about the Aliens do bother me, and you have addressed them well, but I will continue to climb on mine as well.
Thanks for all your dedication to uncovering the discrepancies in CCH's production methods. Hopefully it leads to them getting a better hold on their operation. For the time being, I'll bounce test the hell out of mine and climb on.
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blondgecko
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Jun 16, 2009, 2:50 AM
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adatesman wrote: angry wrote: It's definitely a matter of perception. I'm not here to argue that Aliens are doing something right or wrong, or to defend them. I just love the pieces and want them to catch a fall. After reading this, I believe they will. Certainly with the failure modes and standard deviation among the failures, they wouldn't pass muster in a larger scale operation. Good to hear... I'm not really wanting to argue either; just wanting people to make informed decisions about their safety. Personally I'm not comfortable with how this plays out statistically, so won't be climbing on Aliens ever again. If you're fine with it, good luck and godspeed. 
... just make sure that speed isn't downwards.
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healyje
Jun 16, 2009, 2:50 AM
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angry wrote: I'm not here to argue that Aliens are doing something right or wrong, or to defend them. I just love the pieces and want them to catch a fall. After reading this, I believe they will. Certainly with the failure modes and standard deviation among the failures, they wouldn't pass muster in a larger scale operation.
The whole point of quality programs in manufacturing is to insure the products that make it out the door are consistently performant to the designed [stated] specifications. The idea being that it's NOT a bell curve of adherence to those specifications. When a manufacturer can't control the performance and quality of their products you are being told such a bell curve exists. When it does, by definition, there are going to be shipped edge cases that fail at low loads and that is exactly what has been documented on four years of threads here on RC.
You, as a retail buyer then must insure that any Alien you buy isn't one of the edge cases. A CCH 'Tensile Tested' stamp means nothing because cams with that stamp have failed. The only way to be sure any Alien you own or buy isn't a bad edge case is to test it yourself or find an independent third party to do so.
Again, far from proving Aliens will catch a fall, this testing, along with the existing RC documentation, shows that some Aliens will always fail and fail badly. So long as you're not the one they fail on, you're golden and all is right with the world.
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curt
Jun 16, 2009, 2:58 AM
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blondgecko wrote: adatesman wrote: angry wrote: It's definitely a matter of perception. I'm not here to argue that Aliens are doing something right or wrong, or to defend them. I just love the pieces and want them to catch a fall. After reading this, I believe they will. Certainly with the failure modes and standard deviation among the failures, they wouldn't pass muster in a larger scale operation. Good to hear... I'm not really wanting to argue either; just wanting people to make informed decisions about their safety. Personally I'm not comfortable with how this plays out statistically, so won't be climbing on Aliens ever again. If you're fine with it, good luck and godspeed. ... just make sure that speed isn't downwards.
32ft/s^2
Curt
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healyje
Jun 16, 2009, 3:19 AM
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Just want to see like aspects side-by-side...
(This post was edited by healyje on Jun 16, 2009, 9:50 AM)
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cracklover
Jun 16, 2009, 6:18 AM
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Well, I'm afraid I didn't have the patience to wait for Adatesman to publish his spreadsheet. Being a database guy, and working for an analysis company, I hope you'll forgive me for being anxious to mine the data.
With that said...
adatesman wrote: ptlong wrote: edit: Have you noticed a correlation between axle hole alignment (predicted cam angle at jig setting) and failure load? Haven't gotten that far yet... to do that properly I need to estimate where each cam was contacting the fixture and plot that out. On the to-do list, but not for today. Perhaps tomorrow or Thursday.
I did exactly that. I found no direct correlation between actual angle-at-contact and pullout force. I can send you the data, Aric, if you want to add it to your spreadsheet.
Other correlations I didn't see: cam lobe softness, or how much the axle wound up bent.
The fact that cam lobe softness had little correlation was extremely surprising. I suspect this is probably due to the fact that there are numerous other factors that have an equal or greater effect, creating "noise".
Of course, on the last issue - axle bending, this is a question of causation versus correlation. We don't know if, in some cases in which the cam slipped out at a low force, the axle bending is what caused the failure, while in other cases in which the cam slipped out at a very high force (above the rated strength) the axle bent because of the high force. So we really need to know the strength of the axle to see where the causation lies.
The only two factors that I found with good correlation to relative pullout force (percent of rated strength) were the age of the cam and the size of the cam.
In general, the newer cams performed better relative to their spec. Also, in general, larger cams performed better relative to their spec.
I have a couple of other preliminary conclusions, but I'll sleep on them. More on this tomorrow.
GO
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healyje
Jun 16, 2009, 9:52 AM
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What's the status on axle hardness/strength?
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adatesman
Jun 16, 2009, 2:36 PM
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healyje
Jun 16, 2009, 3:02 PM
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What would it cost to have them tested somewhere?
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adatesman
Jun 16, 2009, 3:09 PM
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cracklover
Jun 16, 2009, 3:50 PM
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Further thoughts...
Variability of materials, angles, and Braze: Well, for many years, the word on the street about CCH was that 1 - They were not a real manufacturing outfit, but simply a machine shop. But 2 - They were artisans, and Dave W. was a perfectionist, who made sure that Aliens were well crafted. Turns out, looks like part 1 was more indicative of the actual output than part 2. More than anything else, I think this test shows that every piece that comes out of their shop is unique, with its own foibles.
So the question is, maybe they're all a little funky, but despite that, can they consistently do what they are supposed to? If I were forced to give a one word answer to that, of course I'd have to say no. But unfortunately the real answer is impossible to give in a simple yes or no.
The failure mode for every one of the modern Aliens that did not meet spec was to pull from the placement. Each of these, when the head was tested separately, failed at well over the rating. Further, Aric's tester was significantly less rough than it could be, and so probably is only indicative of certain placements. My take on that is as follows:
In a slightly bottlenecked or dished placement, or in very rough rock, it is likely that they would all pass. Similarly, in a flaring or in a very hard and slick parallel placement, it seems likely that they would all fail. For placements in between, who knows?
But the argument has been made that those that fail held "well enough". This argument can be further broken down into two ideas:
angry wrote: To me, this is incredibly confidence inspiring. The worst of the aliens tested held loads greater than a fall would have generated.... <snip> Those failures are somewhat concerning if you're in a place where you've got to belay off a single cam and a factor 2 is possible. Otherwise, everything looks great.
Patto wrote: One interesting perspective is to compare the failure loads with the ratings of a comparable cam. For example the Metolius TCUs are rated at 5kN, 8kN, and 10kN for cams that are comparable in size to blue and black Aliens, green Aliens (too bad their there are no samples), and yellow and larger Aliens, respectively.
Angry's argument is, to my mind, baseless. It is actually very easy to generate fall forces in excess of 5-7kN. If you fall early on a pitch, a FF of 1/3 - 2/3 can certainly generate that. All but one of the blue and black Aliens failed at under 7kN. (Unfortunately, we don't know either the angle or the softness of the one that did better.)
Patto's argument is much more sound. Essentially, just lower the ratings to the industry standard for that size cam, and the climber can expect the cam to perform to spec. Given the performance of all but the older cams, I think that's reasonably fair. But the variabilities in materials, shaft positioning, and holding strength says to me that there are no guarantees on this one either.
My takeaway at this point is as follows: there is enough "the cam is good in this situation but bad in that one" that I will, henceforth, recommend to new leaders that they *not* buy Aliens for their first set of small cams. I just think that a new leader is not prepared to deal with this level of nuance.
For more experienced leaders, I would strongly recommend that they test all their cams to at least 1/3 breaking strength, avoid placing them in flaring or very smooth and hard parallel placements, and then don't expect anything better than 80% of their rated strength.
GO
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roy_hinkley_jr
Jun 16, 2009, 4:19 PM
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angry wrote: Aric, I know you're trying to alert us to a safety issue but really, you've proven the reliability of aliens. Clearly they are tested on a different surface than you've got and that accounts for all but 2 of the failures. Those failures are somewhat concerning if you're in a place where you've got to belay off a single cam and a factor 2 is possible. Otherwise, everything looks great.
Bingo! Bears repeating. This witch hunt is an amusing waste of time. There are a LOT more things to worry about while climbing than cam ratings.
OTOH this testing has been valuable in showing people how limited the value of UIAA certification is on cams. A lot of similar weaknesses apply to other UIAA standards as well. Remember that the purpose of standards is to reduce lawsuits.
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ptlong
Jun 16, 2009, 5:13 PM
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adatesman wrote: ptlong wrote: The problem of misdrilled axle holes is a different issue that requires more investigation. Why is that? It seems fairly cut and dried to me, but I've also spent a lot of time playing around with what happens when you move off the center point of the spiral and know that its generally bad.
The question is how it affects the failure load of the cams. None of these twenty or so Aliens from R&S failed at really low levels in your test jig even though it appears they had misdrilled holes. So why not? Is this because the predicted cam angles for the test jig settings weren't that bad? And if so can you really predict with certainty what these cams would fail at for different jig settings?
I'm still curious why Jay couldn't get consistent results measuring the centers while others could. Is there a possibility the errors are being overstated?
Bottom line, I don't see it as a cut and dried issue since the cams in question didn't fail at dangerously low forces (and apparently no correlation between predicted cam angle and failure load was found).
(grammar edit)
(This post was edited by ptlong on Jun 16, 2009, 5:15 PM)
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