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adatesman
Jun 1, 2009, 4:41 PM
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EDIT- A copy of the report submitted to the UIAA and CPSA, which contains all of the missing content below plus the subsequent analysis, is available here: Link
(This post was edited by adatesman on Aug 31, 2010, 7:40 PM)
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adatesman
Jun 1, 2009, 4:41 PM
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adatesman
Jun 1, 2009, 4:42 PM
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adatesman
Jun 1, 2009, 4:42 PM
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adatesman
Jun 1, 2009, 4:42 PM
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adatesman
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adatesman
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adatesman
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adatesman
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adatesman
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adatesman
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adatesman
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adatesman
Jun 1, 2009, 4:45 PM
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adatesman
Jun 1, 2009, 4:46 PM
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adatesman
Jun 1, 2009, 4:46 PM
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adatesman
Jun 1, 2009, 4:46 PM
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adatesman
Jun 1, 2009, 4:47 PM
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adatesman
Jun 1, 2009, 4:47 PM
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adatesman
Jun 1, 2009, 4:47 PM
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adatesman
Jun 1, 2009, 4:47 PM
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adatesman
Jun 1, 2009, 4:48 PM
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adatesman
Jun 1, 2009, 4:48 PM
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patto
Jun 15, 2009, 4:35 AM
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Absolutely fantastic work Aric. Very comprehensive. I hope you are finding some time for relaxationa and most importantly climbing despite all this! :-)
EDIT:In some ways I think most of the usual suspects around the Lab have said their piece on this issue. That said there are a few other forums that this is spreading to now that brand new cams have failed. Its good to get the word out.
(This post was edited by patto on Jun 15, 2009, 7:02 AM)
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marc801
Jun 15, 2009, 5:06 AM
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patto wrote: Absolutely fantastic work Aric. Very comprehensive.
The short version of all this: replace your Aliens with almost anything else. Don't buy any new Aliens. Don't trust any Aliens.
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josephgdawson
Jun 15, 2009, 8:52 AM
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I cannot draw the conclusion that we should replace all of our Aliens from the results in this test.
I do not see any problem with cams pulling out of the fixture below their strength rating (that is, slipping out of the device). 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. In fact, the flattening of the lobes under heavy loads could make the cams stick better in rock. The flattening could prevent rock from breaking.
I think a summary of the failures that are not due to slippage would be more fair and of more use than counting slipping as a failure.
Please correct me if I am wrong, but excluding failures due to slipping out of the rig leaves us with Sample 3 and Sample 7. In my mind these are the more disturbing failures. Sample 3, a used Yellow Alien, had its head pop off at 77.7% of its rated strength. Sample 7, a new Black Alien, slipped out of the rig in the initial test and then the stem failed in the stem test at 6.64KN, while the unit is rated at 8.27KN. As disturbing as these failures are, it should be noted that the Yellow Alien was used and the stem on the Black one failed below its rated strength after it had already gone through one test.
I think it is fantastic that adatesman is doing these tests. Thank you adatesman. I think adatesman did a great job in reporting the information in a standardized and transparent manner. The more data the better.
Adatesman, I must take issue with you being the one to moderate this thread when you are the one who performed the test and posted the results. I think it would strengthen the integrity if this thread if you turned the moderation of it over to a third party who may be more objective and would be less prone to taking any criticism of the test personally.
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patto
Jun 15, 2009, 10:35 AM
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Excellent post josephgdawson.
josephgdawson wrote: I do not see any problem with cams pulling out of the fixture below their strength rating (that is, slipping out of the device). 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.
That said notice the axle bending in most of these cases. It is this axle bending combined with significant lobe flattening that REDUCES the force applied to the lobes and thus reduces friction.
Furthermore notice the aliens that don't slip out. Most of these survive without bent axles and maintain a linear force graph. It seems clear to me the bending of the axle contributes significantly to the slipping out.
josephgdawson wrote: I cannot draw the conclusion that we should replace all of our Aliens from the results in this test.
josephgdawson wrote: In fact, the flattening of the lobes under heavy loads could make the cams stick better in rock. The flattening could prevent rock from breaking.
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blondgecko
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Jun 15, 2009, 10:55 AM
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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.
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adatesman
Jun 15, 2009, 11:32 AM
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mojomonkey
Jun 15, 2009, 1:00 PM
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A couple quick questions on method:
- Were the hybrids also tested in a "parallel" placement, or were you able to angle the plates on your fixture so both sets of lobes were ~ 50%, or split the difference such that one set is more cammed and one set less cammed?
- You pulled the cable loop directly, rather than the sling. Any thoughts on the impact of this? Black Diamond states, in the Camalot booklet that "Clipping directly into the wire loop with a carabiner can reduce the strength of the unit by up to 2 kN (450 lbf)."
- Can you document what the texture on your fixture is versus the min/max from the specification? I know I read it in another thread, but don't want to scan through that monster...
For what its worth, from an prior exchange with Dave Waggoner at CCH, the letter stamped on the head indicated who did the testing. I don't know if the tester is normally also the person who performed the brazing or not. Scanning through, it looks like all of the new units were tested by the same person, indicated by the "W" stamp.
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adatesman
Jun 15, 2009, 1:24 PM
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sethg
Jun 15, 2009, 1:47 PM
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Just FYI, regarding the clipping of the cable loop vs. the sling: In the instructions that come with tcus Metolius gives similar warnings. Metolius warns that clipping directly to the device instead of the sling reduces the strength. I have no idea why either.
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kennoyce
Jun 15, 2009, 2:28 PM
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Thanks for all of the hard work. As always I loved the report.
Just a note on the reduction in strength by clipping to the cable instead of the sling. The only reason I can think of a reduction in strength would be the tight bend of the cable around the biner rather than having the load distributed over the width of the sling. If this is the case then the weak point would be the attachment point of the carabiner. Since none of the cams tested failed at this point, the tested strengths shouldn't depend on weather it was loaded with the sling or with a biner.
Just a thought.
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shimanilami
Jun 15, 2009, 3:52 PM
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Great work, Aric. But I don't think it will change anyone's mind about Aliens. (I, for one, am still a fan.)
Have you done these same studies with other cams? Now that we know how good/bad the Aliens are, I'd like to see how others compare.
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adatesman
Jun 15, 2009, 3:59 PM
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jt512
Jun 15, 2009, 5:23 PM
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Aric, this is great work. Thank you for undertaking this monumental project. I have a couple of questions. Excuse me if they have already been asked; I haven't read the whole thread.
First, a question which naturally arises reading through your results is how do Aliens compare with other brands. I realize that you may have not undertaken a systematic study of other brands, and that to do so would likely be prohibitive in terms of time and cost. However, the question of mislocated axle holes is highly dependent on the accuracy of the software used and the skill of the person using it, and so, I think that presenting results of this measurement from other brands for comparison will help put the Alien results in context. Either other brands will also be found to have mislocated axle holes, or they will not. If they do, then that will either mean that all cams are equally bad in this regard, or that the measurement procedure is unreliable. If they do not, then presenting the results will strengthen the case that the problem is unique to Aliens.
The second question has to do with the presentation format. That is a lot of material to read in an online forum format. It would be much easier to read and digest if it could be downloaded and printed out. Any chance that you could compile this into a pdf and put it on a website (maybe this one, but not necessarily) for download. I could always host it on my web server.
Relatedly, it would also be nice to have the data in a data base (or at least a spreadsheet) to facilitate analysis. In the present "flat" format, even simple questions like "what percentage of tested cams were marked 'tensile tested'?" or "how do results compare for 'tensile tested' Aliens vs others?" are laborious to answer; whereas, if the data were in a spreadsheet, the answers would be only a few mouse clicks away.
Jay
(This post was edited by jt512 on Jun 15, 2009, 7:09 PM)
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shoo
Jun 15, 2009, 6:05 PM
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Can you also put this on the front page under the Destruction Theater? I think it deserves a place there.
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qtm
Jun 15, 2009, 6:52 PM
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jt512 wrote: However, the question of mislocated axle holes is highly dependent on the accuracy of the software used and the skill of the person using it, and so, I think that presenting results of this measurement from other brands for comparison will help put the Alien results in context. Either other brands will also be found to have mislocated axle holes, or they will not. If they do, then that will either mean that all cams are equally bad in this regard, or that the measurement procedure is unreliable. If they do not, then presenting the results will strengthen the case that the problem is unique to Aliens. Jay
I scanned in 28 cams. 9 Aliens, 7 BD Camalots, 8 Tech Friends, 2 WC Zeros, and 2 Master cams. I did multiple photographs of each since the first couple of times I wasn't sure if I were doing it right, and had some problems with rounded edges showing up as the lobe. This was primarily resolved using manual points.
In the end, all the Aliens show up as off-center. All the other cams are fine... except one BD C4 .3 cam.
I don't know why, but it always comes up off center; depending on how many points I pick, the center wanders around a bit. Close, but I can't get it to fit as easily as all the rest.
It's possible that the lobe is a little deformed, it might be one that I had to remove with the help of a nut tool and a big rock. The interesting thing is that the lobe on the other side scans in fine. That leads me to believe the software works as advertised.
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adatesman
Jun 15, 2009, 7:29 PM
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healyje
Jun 15, 2009, 9:54 PM
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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.
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angry
Jun 15, 2009, 10:08 PM
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I hate to be that guy but...
If anything, these tests have given me confidence in well placed newer aliens. I thought my old ones were fine but was leery of other peoples.
It appears that in most cases, the braze is quite good. The failure from your fixture isn't too realistic and is still more than enough.
There is some reworking of published ratings that need to be done and the cam axle hole thing needs to be addressed. In regards to falling on them and getting caught, they look good.
I am also inclined to think that the axles bend when the lobes slipped out, not that bending axles caused the lobes to slip. Look at the axles of the ones that didn't slip.
What do you suppose the heads would have held if the lobes hadn't slipped out?
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philbox
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Jun 15, 2009, 10:26 PM
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adatesman wrote: josephgdawson wrote: Adatesman, I must take issue with you being the one to moderate this thread when you are the one who performed the test and posted the results. I think it would strengthen the integrity if this thread if you turned the moderation of it over to a third party who may be more objective and would be less prone to taking any criticism of the test personally. FWIW I'm not the only Mod here in The Lab, just the one who happens to spend the most time here. I've asked the others to help keep an eye on this since I completely agree there's the potential for inappropriate use of powers. The only modding I did in the last thread was hiding a couple off-topic/silly posts in the first couple pages and banning the CCH shill after discussing it with the other mods. While these actions may have not been transparent to the general user base, everything was discussed at length in the Mod forum before being done.
There is at least one other mod who is keeping a very close eye on this thread, me. Aric is not doing this alone. He does take the lead in this thread which is right and proper given that it is his area of expertise. There has been much discussion on the mods forum as part of the oversight of Aric's modding within this forum. Aric is doing an awesome job here particularly given the subject matter. I and in fact all the mods and the management of this website have complete confidence with Aric.
What also should be noted is that this website has a policy of complete transparency as to mod actions. Nothing is deleted. We track and audit actions. This ensures that mods actions are reversible if it is thought that the action is not correct. Of course most actions are telegraphed back to the user via the PM system. We do however simply ship off to the recycle bin any scammer or spammer posts without referral to the scammer/spammer.
Aric's actions as a mod do in no way negate his work with this subject.
Bact to the topic at hand then.
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jt512
Jun 15, 2009, 11:09 PM
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adatesman wrote: jt512 wrote: The second question has to do with the presentation format. That is a lot of material to read in an online forum format. It would be much easier to read and digest if it could be downloaded and printed out. ... I'm almost done with it and will post a link to the PDF when its finished (currently resizing pics to knock it down from 110 pages).
Yikes! Sounds like a good idea.
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curt
Jun 16, 2009, 12:02 AM
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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
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adatesman
Jun 16, 2009, 12:08 AM
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yokese
Jun 16, 2009, 12:32 AM
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jt512 wrote: Relatedly, it would also be nice to have the data in a data base (or at least a spreadsheet) to facilitate analysis. In the present "flat" format, even simple questions like "what percentage of tested cams were marked 'tensile tested'?" or "how do results compare for 'tensile tested' Aliens vs others?" are laborious to answer; whereas, if the data were in a spreadsheet, the answers would be only a few mouse clicks away. Jay
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). I can upload it to the internet and share with anyone interested.
Edited: Not gonna do it. Adatesman is gonna upload his data file. (next post)
(This post was edited by yokese on Jun 16, 2009, 12:52 AM)
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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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adatesman
Jun 16, 2009, 5:36 PM
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drector
Jun 16, 2009, 5:36 PM
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angry wrote: It's definitely a matter of perception. [snip] After reading this, I believe they will. [snip]
angry,
If someone told you that your car might have been built with a bomb in it and it could go off at any time, would you still love your car? Now what if Aric told you that you have an Alien with a bad braze that will hold too little to catch a fall? You still want to use them?
The problem with manufacturing defects through bad QC is that it lets in the question of how many bad cams you have. Maybe you happen to be the guy with a rack of Aliens that all have a bad braze. There is no way to know and you are no longer a climber. You're a gambler.
The bad QC is the important issue. The tests confirmed that Aliens have badly placed holes in the lobes and bad brazing. It also suggests that the cam lobes are not properly hardened. There was even the one Alien that got its axle bent at a lower load than expected. It's all signs that using an Alien is like playing craps ... for you life.
I hope that all of your Aliens are manufactured properly and hold all of your falls. Good luck.
Dave
P.S. The Alien offsets I own are the best cams I have discounting the possibility that they might break.
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jt512
Jun 16, 2009, 5:39 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.
Well, there is a lot of variability in terms of how their strength, as measured by Aric, compared with their rated strength. The mean of (measured strength) / (rated strength) * 100% was 89.4% with a standard deviation of 16.0%.
The average is dragged down by the smaller cams. The two black Aliens in the sample had the lowest numbers (54.7% and 63.6%), and one of the two blue Aliens in the sample had the third lowest (69.8%).
The 13 Aliens in the sample that were rated for 2700 lbf did the best. They attained 98.0% of their rated strength, on average, with a standard deviation of 11.1%. The mean strength in this subsample was 2647 lbf, with a standard deviation of 300 lbf, giving a coefficient of variation of 11.3%, which is alarmingly high, and indicates the opposite of your conclusion. These data do not "prove the reliability of Aliens." They suggest the contrary.
In reply to: Clearly they are tested on a different surface than you've got and that accounts for all but 2 of the failures.
If Aric's testing has produced results equivalent to UIAA testing—and I'm not saying that it has—then the correct 3-sigma rating for the 2700-lbf-rating Aliens should be in the neighborhood of 1750 lbf. How can you state that such a large discrepancy is "clearly" due to different testing surfaces?
Jay
(This post was edited by jt512 on Jun 16, 2009, 6:33 PM)
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k.l.k
Jun 16, 2009, 5:48 PM
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You know, I don't even care about the numbers. Just look at those brazes in that photo that Healeyje linked.
Just frickin amazing.
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jt512
Jun 16, 2009, 6:13 PM
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adatesman wrote: The full explanation with diagrams and equations is over on Vaino Kodas' site, but what it boils down to is that assuming structural integrity of the unit, a cam will stay in place in a parallel placement regardless of force applied so long as the tangent of the cam angle is larger than the coefficient of friction between the lobe and the surface it is contacting.
Shouldn't that be "less than"?
Jay
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ptlong
Jun 16, 2009, 6:19 PM
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adatesman wrote: The test jig is terrible for representing how the cams would react in this regard, because the frictional coefficient between aluminum and steel is roughly double that of aluminum and most types of rock and therefore the cams will stick with far less available outward force. (Erm... make that should due to the other issues that effect it holding, such as lobe and axle deformation.)
I see. You're saying the jig surface friction is 2x greater than typical rock while angry is claiming the surface is the reason the cams were slipping out.
I don't doubt simple cam theory. I just want to see some proof that what you think you're measuring is real.
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adatesman
Jun 16, 2009, 6:33 PM
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jt512
Jun 16, 2009, 7:06 PM
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ptlong wrote: I'm still curious why Jay couldn't get consistent results measuring the centers while others could.
You're probably confused because you are assuming I am a competent photographer, whereas in reality I probably just suck. I have been unable to get images that meet the three criteria for the software to provide valid measurements of the cam center; namely, sharp focus, centering on the cam axle, and angle aligned with the cam axle. I have a long and tearful history of getting bad lab results, so there is a good chance that other people are getting better photographs than I.
That said, I'm still skeptical of the way people are doing these measurements. No one, as far as I can tell, has performed them in a manner that is controlled well enough to validate the procedure. The following questions remain open:- How much does camera angle and camera centering affect the measurement?
- If (1) is important, then how good has the centering and angle been in the photographs used?
- How much does manual selection of the sampled points bias the measurements or affect their reliability?
- Do repeated photographs and selection of sample points on the same unit produce consistent results?
- In a systematic comparison, how would results for Aliens and other brands compare?
Jay
(This post was edited by jt512 on Jun 16, 2009, 7:07 PM)
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roy_hinkley_jr
Jun 16, 2009, 7:21 PM
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jt512 wrote: That said, I'm still skeptical of the way people are doing these measurements. No one, as far as I can tell, has performed them in a manner that is controlled well enough to validate the procedure. Jay
Thank you Jay. These were such obvious questions they should have been addressed long ago. Similarly, there is a lot that Aric doesn't understand about what he's trying to test or the standards and how they are created. He'd rather insult Roy than deal with legitimate concerns about how he is going about things. Whatever.
The real issue is that there still isn't any safety concern that has been proven. Lots of doubts, mostly ill-informed conjecture, and certainly weak quality control. But all and all a tempest in a teacup.
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jt512
Jun 16, 2009, 7:43 PM
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roy_hinkley_jr wrote: jt512 wrote: That said, I'm still skeptical of the way people are doing these measurements. No one, as far as I can tell, has performed them in a manner that is controlled well enough to validate the procedure. Jay
To clarify, I was referring to the determination of the cam center.
Jay
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cracklover
Jun 16, 2009, 7:47 PM
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adatesman wrote: ptlong wrote: adatesman wrote: The test jig is terrible for representing how the cams would react in this regard, because the frictional coefficient between aluminum and steel is roughly double that of aluminum and most types of rock and therefore the cams will stick with far less available outward force. (Erm... make that should due to the other issues that effect it holding, such as lobe and axle deformation.) I see. You're saying the jig surface friction is 2x greater than typical rock while angry is claiming the surface is the reason the cams were slipping out. I don't doubt simple cam theory. I just want to see some proof that what you think you're measuring is real. Close... What I'm saying is that the frictional coefficient of aluminum on steel is ~2x the frictional coefficient of aluminum on rock. This coefficient is for the base materials and ignores special surface treatments like texturing. While the texture will certainly play a minor role in the cam holding, the mechanics behind how these things work is entirely based on friction and not dependent at all on the texture of the surfaces. Additionally I believe that the fact that some of the Aliens and all of the other cams I've tested did not slip out of the fixture points conclusively to the effect of the texture of the plates being negligible.
Aric, the trouble I'm having is that I don't see any correlation between effective cam angle and the point at which the cam slipped.
For example, here are the cams for which I was able to determine an effective cam angle, ordered by angle. I've broken them down into thirds for the purpose of getting averages:
sample rating failure failure angle RATING Soft avg failure avg rating
Mode kN % Lobes kN %
-----------------------------------------------------------------------------
3 12 braze 9.3 14 77.50% Y (not counted due to braze failure)
23 9.8 pulled 6.8 15 69.39% Y 11.24 90.94%
1 12 pulled 10.6 16 88.33% Y
15 12 pulled 13.5 16 112.50% Y/N
6 15.5 pulled 14 16 90.32% Y/N
9 12 pulled 11.3 17 94.17% N
14 12 broke cable 12.1 17 100.83% Y 11.86 94.38%
8 12 pulled 11.1 18 92.50% Y/N
18 12 broke cable 12 18 100.00%
2 15.5 pulled 11.4 18.5 73.55% N
21 12 pulled 12.6 19 105.00% N
12 12 broke cable 12 19 100.00% Y
17 12 pulled 11.8 20 98.33% Y
20 12 pulled 9.9 21 82.50% N 11.36 89.82%
19 12 pulled 12.6 21 105.00% Y
16 12 broke cable 14 21 116.67% Y/N
7 8.25 pulled 5.25 22 63.64% Y
4 15.5 pulled 12.6 22 81.29% N
5 15.5 pulled 13.8 23 89.03% N
Now you could make the argument that the cam angle in and of itself is not high enough to cause these cams to rip, but in conjunction with the very soft lobes on some of the cams, the effective angle quickly grows until it gets too high and the cam slips out of the fixture.
But the data doesn't directly support that, either. Of the four cams in this sample where the failure mode was not slipping (12, 14, 16, 18), you find them in the middle and upper third of cam angles, and all three that have hardness ratings had particularly soft metal lobes.
So, really, I'm at a loss to say why the cams are pulling from the fixture, though I can say pretty confidently that the softness of the lobes and the cam angle aren't the biggest factor.
I'm certainly curious to see what you find out about the axles. Perhaps that's the missing piece of the puzzle.
What do you think?
GO
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adatesman
Jun 16, 2009, 8:09 PM
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shoo
Jun 16, 2009, 8:10 PM
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angry wrote: 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.
I think you're paying attention to the wrong thing here.
Yes, all of these cams held an amount of force that would be expected in a lead fall under near ideal conditions (the point of debate being the plates used in the fixture).
However, the actual amount of force held had a very large variance (jt512, please chime in here if I say something wrong, it's been a while since my last stats course). Think about the force held on a distribution here. Large variance = wide distribution. The wider the distribution, the more cams there are that would be expected to fail below a given amount of force.
All we can really take from these tests (and for lack of more data and further analysis, this is even a stretch) is that the median and mean cam will hold a typical lead fall worth of force. However, given the wideness of the distribution, I would hazard a guess that there are probably plenty of cams out there that would not do so. Without knowing more about the distribution of force held by the cams, this is only a guess.
What really important here is the question of how many aliens are out there that WILL NOT hold a fall.
Given the unpredictability in the force held, the variety of failure modes, my guess would be quite a few
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boku
Jun 16, 2009, 8:13 PM
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adatesman wrote: As I mentioned in the OP, unfortunately my tester can't get reliable readings on the axles due to the V-anvil (the thing that holds it) being slightly off center which results in the penetrator sliding off when the main load is applied...
Aric, did you consider just cutting the axles in half and testing the cut face? Just curious.
Thanks, Bob K.
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hafilax
Jun 16, 2009, 8:17 PM
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boku wrote: adatesman wrote: As I mentioned in the OP, unfortunately my tester can't get reliable readings on the axles due to the V-anvil (the thing that holds it) being slightly off center which results in the penetrator sliding off when the main load is applied... Aric, did you consider just cutting the axles in half and testing the cut face? Just curious. Thanks, Bob K.
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qtm
Jun 16, 2009, 8:22 PM
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1. Very little. Aric demonstrated in the original thread, post #24.
2. Using the same technique, the non-aliens consistently produce good results while aliens produce offcenter results. Consistent results for dozens of cams from several people seems to indicate that the individual procedure doesn't make much a difference and isn't affected greatly by camera angle or zoom or whatever.
3. Manual selection produces much better results. As long as you select actual points on the lobe, which can be difficult if the lobe is worn or damaged.
4. Yes. To the point the aliens are consistent with what other people have posted.
5. Exactly as we have been saying.
So what exactly do you consider a controlled manner? The first round, I clamped the cam stem in a big clamp, took pictures from a controlled height at the same zoom.
Second round, I held the alien by hand, resting on the table, and the camera in macro mode 4" away, under different lighting.
A few pictures in a third test, backlit to give me a dark profile.
Consistent results (as long as I picked the points manually) all the way through. Results consistent with other people, whatever methods they used.
Seems obvious to me.
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cracklover
Jun 16, 2009, 8:30 PM
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How much does camera angle and camera centering affect the measurement?
I believe Aric addressed this in an earlier post on the misdrilled axle holes thread.
The gyst of it is that with enough angle you can get the central point to move around relative to the middle of the axle of course, because the axle is closer to the camera. With that said, I've not had the level of difficulty you have in getting the axle centered.
If (1) is important, then how good has the centering and angle been in the photographs used?
Certainly a valid question. I'll say this for my photos - whatever technique I've used has been good enough so that all the photos I've taken of my non-CCH cams has shown the center point to line up consistently, and all the repeat photos I've taken of the same cam has given me the same results.
How much does manual selection of the sampled points bias the measurements or affect their reliability?
Don't know.
Do repeated photographs and selection of sample points on the same unit produce consistent results?
For me, yes.
In a systematic comparison, how would results for Aliens and other brands compare?
Unfortunately (for many reasons) I don't have many other small cams at my disposal at the moment. Using the software on larger cams isn't really a fair comparison, since if they're off by a mm or two, you'd hardly notice, and the affect on the effective cam angle would be negligible.
GO
(This post was edited by cracklover on Jun 16, 2009, 8:31 PM)
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angry
Jun 16, 2009, 8:38 PM
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I feel like I'm really taking a beating here for my opinion on Aliens.
As I stated yesterday, I am not defending them to Aric nor do I think he's got an axe to grind.
I don't think of them as a car or a bolt or an airliner. I don't now, and never have used them with the implicit idea that they were infallible. That said, I've taken many many falls on everything I own. I probably owe everyone who's ever belayed me a handjob.
I'm an extremely cautious climber. I'm constantly weighing the cost/benefit of placing more pro or trusting my ability to climb on. I've got both eyes and my (overactive) imagination running the scenario of what would happen if I fell at any time and what would happen if my gear ripped. I'm happy to say that most of these scenarios are far more benign than I imagine them to be, I know this because in my time, they have ALL played out.
Leeper hangers, ice curtains collapsing while I'm on them, tipped out cams in choss, nuts between two crystals, ice screws in foam, a fixed RURP, blown tendons, and a core shot in my rope. Sorry, I don't hang it out so far that a cam holding 2kn (or 4) less than it should will affect me in any meaningful way.
Someone on this forum once said, "Three pieces between me and the ER/morgue" I completely agree.
In the end, I'm still more worried about the rock I place my gear into and the thunderstorms building behind me than I am about the ultimate strength of my cams.
Sorry for the drift Aric, but I felt that I needed to defend myself.
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cracklover
Jun 16, 2009, 8:53 PM
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Hey Angry, I didn't mean to put any kind of beatdown on you. In fact, I think we agree entirely, aside from two points:
1 - Spin. The spin you're putting on it is that Aliens are bomber. I don't think the evidence bears that out at all, especially for leaders just getting into the game.
2 - the difficulty of putting a > 5kN force on your gear. You know this, of course, but a fall early on a pitch, even a short fall, can put large forces on your gear. Unless I misunderstood, some of your posts belie that fact.
But overall, I'm in the same boat as you, and aside from two of my Aliens (with the worst drilled axles) I'll still be using them. Of course, I already have stated in other threads that I only trust them to around the 5kN that I've personally tested them.
GO
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jt512
Jun 16, 2009, 8:54 PM
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angry wrote: Sorry for the drift Aric, but I felt that I needed to defend myself.
I don't think anyone here is attacking you personally. We're just questioning your conclusions.
Jay
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adatesman
Jun 16, 2009, 8:57 PM
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jt512
Jun 16, 2009, 9:32 PM
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qtm and cracklover, I realize that several people have done enough work to answer some of my concerns informally, but no one has yet done a systematic, well-controlled study of the validity of the procedure, in which the methodology of the study and the results have been rigorously documented.
The procedure of estimating the cam center relies on the the subjective judgment of the operator to position the camera properly and to pick accurate sample points. For me to be convinced that this procedure produces valid, reproducible results, I would have to have been able to produce them myself (which I couldn't), or I'd have to see convincing data, presented in a manner that I could analyze. The effect of human error in this procedure needs to be studied more thoroughly and better understood. You may have informally examined this issue sufficiently to convince yourselves of the validity of your data, but to convince a skeptical third party, a more rigorous study is needed.
Jay
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cracklover
Jun 16, 2009, 9:39 PM
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adatesman wrote: When you were going through your analysis did you notice anything in regards to which axles bent most? I've been busy publishing all the photos to the web today so haven't been able to look at any of this yet. -a.
Here's the data:
axle sample rating failure angle rating average average avg %
bent number kn kn % angle fail kN rating
no 3 12 9.3 14 77.50% 18.4 9.4 77%
no 9 12 11.3 17 94.17%
no 8 12 11.1 18 92.50%
no 20 12 9.9 21 82.50%
no 7 8.25 5.25 22 63.64%
no 24 8.3 4.5 54.22%
slight 1 12 10.6 16 88.33% 18.2 11.8 99%
slight 14 12 12.1 17 100.83%
slight 21 12 12.6 19 105.00%
slight 12 12 12 19 100.00%
slight 17 12 11.8 20 98.33%
yes 23 9.8 6.8 15 69.39% 19.7 11.1 89%
yes 2 15.5 11.4 18.5 73.55%
yes 19 12 12.6 21 105.00%
yes 16 12 14 21 116.67%
yes 5 15.5 13.8 23 89.03%
yes 22 9.8 8.1 82.65%
very 15 12 13.5 16 112.50% 18.0 13.4 95%
very 6 15.5 14 16 90.32%
very 4 15.5 12.6 22 81.29%
This time I broke it into quartiles, based on the amount of bending I saw in your pics. I think it's pretty obvious that there's an excellent correlation both to the amount of force the cam saw, and to the relative strength of the cam (which is really just saying the same thing, but factoring in the size).
However I see no correlation to the effective cam angle, or to the general softness of the lobes. I haven't checked to see if cams with some soft and some hard lobes have a correlation. This one might be tricky, as it might depend on which lobes are soft (outer, inner, etc). But in general, simple softness of lobes doesn't have a correlation.
Of course the axle hardness numbers might be very interesting here, too.
The only conclusion to draw here is pretty simple - the more force the cam felt, both in absolute kN, and relative to the size of the cam, the more the axle bent. I know this is a no-brainer, but I'm afraid I don't see any more interesting correlations.
GO
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cracklover
Jun 16, 2009, 9:45 PM
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adatesman wrote: cracklover wrote: What do you think? I think we're entering the land of ill-informed conjecture Roy is complaining about.  Seriously though, I think there's a definite problem with Aliens there somewhere given that some of them didn't slip and other brands never seem to have a problem.
What I mean is that neither the degree of softness of the lobes, nor the degree of high effective angle due to mis-drilled axle holes, seem to explain the Aliens slipping from the fixture.
So since you're making the argument for those being the primary reason why Aliens are slipping out of the fixture, I thought perhaps you'd like to defend that idea in light of your data.
GO
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adatesman
Jun 16, 2009, 10:00 PM
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blondgecko
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Jun 16, 2009, 10:28 PM
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adatesman wrote: cracklover wrote: adatesman wrote: cracklover wrote: What do you think? I think we're entering the land of ill-informed conjecture Roy is complaining about. Seriously though, I think there's a definite problem with Aliens there somewhere given that some of them didn't slip and other brands never seem to have a problem. What I mean is that neither the degree of softness of the lobes, nor the degree of high effective angle due to mis-drilled axle holes, seem to explain the Aliens slipping from the fixture. So since you're making the argument for those being the primary reason why Aliens are slipping out of the fixture, I thought perhaps you'd like to defend that idea in light of your data. GO Gotcha... Um, well, you've looked at that part of the data more than I have and frankly I think you're right about the data not supporting my suspicions. Given that, I guess I don't have a theory that explains why they're pulling out. But that's certainly what they're doing, so there's a reason for it there somewhere. For argument's sake I will be retexturing my fixture again and testing a couple more and will report back with those results (it'll probably be next week sometime). In the meantime I'll see about finding somewhere to send the axles for hardness testing.
The wildly varying numbers for hardness say there's something going on with the alloy, but shear strength is the more applicable measurement here. Unfortunately, it's rather more difficult to measure.
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jamincan
Jun 16, 2009, 11:55 PM
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jt512 wrote: qtm and cracklover, I realize that several people have done enough work to answer some of my concerns informally, but no one has yet done a systematic, well-controlled study of the validity of the procedure, in which the methodology of the study and the results have been rigorously documented. The procedure of estimating the cam center relies on the the subjective judgment of the operator to position the camera properly and to pick accurate sample points. For me to be convinced that this procedure produces valid, reproducible results, I would have to have been able to produce them myself (which I couldn't), or I'd have to see convincing data, presented in a manner that I could analyze. The effect of human error in this procedure needs to be studied more thoroughly and better understood. You may have informally examined this issue sufficiently to convince yourselves of the validity of your data, but to convince a skeptical third party, a more rigorous study is needed. Jay
I don't think positioning the camera is necessarily subjective. The alignment of the camera with the axle would be best done with a tripod with a level, and then similarly ensuring that the cam lobe is level (fairly easy if taking the cam apart, harder if leaving it assembled, but certainly not impossible). The centring can be confirmed later by examining the centre of the axle with the centre of the photograph. If they coincide, you're good to go.
If confirmation is necessary, you could print of a logarithmic spiral, photograph it, and then compare it with either the original digital version of the spiral, or with the software Aric linked us to.
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hafilax
Jun 17, 2009, 12:09 AM
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It seems to me that the easiest way of getting at the cam angle at each spot is to measure the angle between a line drawn from the center of the axle and tangent at the intersection of the surface. That's how the logarithmic spiral was defined in the first place. You can do it with a protractor and dispense with all of this camera nonsense.
This whole fitting thing makes for a pretty image showing an off center axle but it's not really what people are interested in.
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jt512
Jun 17, 2009, 1:14 AM
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cracklover wrote: adatesman wrote: When you were going through your analysis did you notice anything in regards to which axles bent most? I've been busy publishing all the photos to the web today so haven't been able to look at any of this yet. -a. Here's the data: axle sample rating failure angle rating average average avg %
bent number kn kn % angle fail kN rating
no 3 12 9.3 14 77.50% 18.4 9.4 77%
no 9 12 11.3 17 94.17%
no 8 12 11.1 18 92.50%
no 20 12 9.9 21 82.50%
no 7 8.25 5.25 22 63.64%
no 24 8.3 4.5 54.22%
slight 1 12 10.6 16 88.33% 18.2 11.8 99%
slight 14 12 12.1 17 100.83%
slight 21 12 12.6 19 105.00%
slight 12 12 12 19 100.00%
slight 17 12 11.8 20 98.33%
yes 23 9.8 6.8 15 69.39% 19.7 11.1 89%
yes 2 15.5 11.4 18.5 73.55%
yes 19 12 12.6 21 105.00%
yes 16 12 14 21 116.67%
yes 5 15.5 13.8 23 89.03%
yes 22 9.8 8.1 82.65%
very 15 12 13.5 16 112.50% 18.0 13.4 95%
very 6 15.5 14 16 90.32%
very 4 15.5 12.6 22 81.29% This time I broke it into quartiles based on the amount of bending I saw in your pics.
Those groups are not quartiles.
In reply to: I think it's pretty obvious that there's an excellent correlation both to the amount of force the cam saw, and to the relative strength of the cam (which is really just saying the same thing, but factoring in the size).
Those correlations are neither obvious nor excellent. Visually, I see a reasonable correlation between the amount of bending and the absolute failure load, and no correlation at all between the amount of bending and the failure load as a percentage of rated strength. A quick logistic regression analysis backs this up. For the relation with absolute failure load, pseudo-R² = 0.28 (this statistic in some sense measures the strength of the relationship, ranges from 0 to 1—bigger is better), and the p-vaule is 0.035. For the relation with failure load relative to strength rating, pseudo-R² = 0.08, and the p-value is 0.21.
In reply to: The only conclusion to draw here is pretty simple - the more force the cam felt, both in absolute kN, and relative to the size of the cam, the more the axle bent.
That's only true for the absolute force, as noted above.
Jay
(This post was edited by jt512 on Jun 17, 2009, 1:16 AM)
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jt512
Jun 17, 2009, 2:29 AM
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cracklover wrote: Aric, the trouble I'm having is that I don't see any correlation between effective cam angle and the point at which the cam slipped.
We wouldn't expect to see a correlation between cam angle and the applied force at which the cam slipped. Accoding to Vaino Kodas's equations, there is no relationship between the applied force at which a cam would slip cam angle. If the cam angle is less than a critical value, the cam will not slip at any applied force; if the cam angle is greater than the critical value, the cam will slip at any applied force.
In reply to: For example, here are the cams for which I was able to determine an effective cam angle, ordered by angle. I've broken them down into thirds for the purpose of getting averages: sample rating failure failure angle RATING Soft avg failure avg rating
Mode kN % Lobes kN %
-----------------------------------------------------------------------------
3 12 braze 9.3 14 77.50% Y (not counted due to braze failure)
23 9.8 pulled 6.8 15 69.39% Y 11.24 90.94%
1 12 pulled 10.6 16 88.33% Y
15 12 pulled 13.5 16 112.50% Y/N
6 15.5 pulled 14 16 90.32% Y/N
9 12 pulled 11.3 17 94.17% N
14 12 broke cable 12.1 17 100.83% Y 11.86 94.38%
8 12 pulled 11.1 18 92.50% Y/N
18 12 broke cable 12 18 100.00%
2 15.5 pulled 11.4 18.5 73.55% N
21 12 pulled 12.6 19 105.00% N
12 12 broke cable 12 19 100.00% Y
17 12 pulled 11.8 20 98.33% Y
20 12 pulled 9.9 21 82.50% N 11.36 89.82%
19 12 pulled 12.6 21 105.00% Y
16 12 broke cable 14 21 116.67% Y/N
7 8.25 pulled 5.25 22 63.64% Y
4 15.5 pulled 12.6 22 81.29% N
5 15.5 pulled 13.8 23 89.03% N Now you could make the argument that the cam angle in and of itself is not high enough to cause these cams to rip, but in conjunction with the very soft lobes on some of the cams, the effective angle quickly grows until it gets too high and the cam slips out of the fixture.
I wonder if it isn't so much a function of the flat spots on the cam increasing the cam angle as it the flat spots making the cam essentially no longer a cam. Would you expect something like this...
...to really work like a cam? Or maybe it would. After all hexes hold in parallel cracks.
Jay
(This post was edited by jt512 on Jun 17, 2009, 3:07 AM)
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cracklover
Jun 17, 2009, 4:04 AM
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jt512 wrote: cracklover wrote: Aric, the trouble I'm having is that I don't see any correlation between effective cam angle and the point at which the cam slipped. We wouldn't expect to see a correlation between cam angle and the applied force at which the cam slipped. Accoding to Vaino Kodas's equations, there is no relationship between the applied force at which a cam would slip cam angle. If the cam angle is less than a critical value, the cam will not slip at any applied force; if the cam angle is greater than the critical value, the cam will slip at any applied force.
Let's say the point at which the angle is too great is 30 degrees. If the effective cam angle starts at 29, a little deformation, and presto, you're over the line. So the closer to that magic number, the less force should be required to push you over it. But... that's not exactly what we're seeing.
Now if the relative hardness of the cam lobes is a much bigger factor, then it might erase any correlation based on the starting effective angle. But... I don't see any correlation based on either a combination of the two, or on either individually.
In reply to: I wonder if it isn't so much a function of the flat spots on the cam increasing the cam angle as it the flat spots making the cam essentially no longer a cam. Would you expect something like this... [img]http://www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09_broken_left.JPG[/img] ...to really work like a cam? Or maybe it would. After all hexes hold in parallel cracks.
How exactly that flat spot affects the "friction" is waaaay beyond my paygrade. I'm really just a DBA/developer with a halfway decent grasp of basic physics and a good head for problem-solving.
I agree with Aric, though. Something is allowing the cams to slip, and it certainly seems to vary from cam to cam. I just don't think we've put our finger on what that key variable, or variables set is, yet. And it's distinctly possible that with such a small dataset, it may not be possible to find it for certain.
GO
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jt512
Jun 17, 2009, 4:40 AM
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cracklover wrote: jt512 wrote: cracklover wrote: Aric, the trouble I'm having is that I don't see any correlation between effective cam angle and the point at which the cam slipped. We wouldn't expect to see a correlation between cam angle and the applied force at which the cam slipped. Accoding to Vaino Kodas's equations, there is no relationship between the applied force at which a cam would slip cam angle. If the cam angle is less than a critical value, the cam will not slip at any applied force; if the cam angle is greater than the critical value, the cam will slip at any applied force. Let's say the point at which the angle is too great is 30 degrees. If the effective cam angle starts at 29, a little deformation, and presto, you're over the line. So the closer to that magic number, the less force should be required to push you over it. But... that's not exactly what we're seeing. Now if the relative hardness of the cam lobes is a much bigger factor, then it might erase any correlation based on the starting effective angle. But... I don't see any correlation based on either a combination of the two, or on either individually. In reply to: I wonder if it isn't so much a function of the flat spots on the cam increasing the cam angle as it the flat spots making the cam essentially no longer a cam. Would you expect something like this... [img]http://www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09_broken_left.JPG[/img] ...to really work like a cam? Or maybe it would. After all hexes hold in parallel cracks. How exactly that flat spot affects the "friction" is waaaay beyond my paygrade. I'm really just a DBA/developer with a halfway decent grasp of basic physics and a good head for problem-solving. I agree with Aric, though. Something is allowing the cams to slip, and it certainly seems to vary from cam to cam. I just don't think we've put our finger on what that key variable, or variables set is, yet. And it's distinctly possible that with such a small dataset, it may not be possible to find it for certain. GO
Well if it's cam angle, then, according to theory, you should be able to put the cam back in the jig, with the flat spots on the cam lobes against the test surfaces, and the cam should pull out under any force.
A note on the cam angles in your table: they probably are unreliable. Consider all the sources of error in them: error in camera angle, error in point selection, error in estimating the % retraction of the cams in the jig, error in estimating the test % retraction point in the photo, and error in estimating the cam angle at the estimated % retraction point. These errors attenuate the correlation between the true tested cam angle and the estimated tested cam angle; and hence, would attenuate any observed correlation between estimated cam angle and maximum force held. So even if there were actually a correlation between the tested cam angle and maximum force held, it could be obliterated by the cumulative effects of sources of error in the determination of the tested cam angle.
Jay
(This post was edited by jt512 on Jun 17, 2009, 4:41 AM)
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irregularpanda
Jun 17, 2009, 5:42 AM
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Can I chime in here with a question or two?
First off, this sort of hread isn't really my bag, normally I'm all about poopin' and fartin' jokes, on top of the occasional medical tangent.
So, with all this hubbub and thorough testing of aliens going on, I had a couple questions for Aric. I have several, and so does a friend. I don't have the time to spend analyzing my aliens, looking at the centering on the drill holes, or pull testing them. Is it possible to send some to you (about 10 or more) to have them looked at but not destroyed? Is it possible to make any sort of a prediction based on a pull test (just a pull, not a destructo-pull) combined with an analysis of the centering of the lobes?
I know that there is certain data you're still gathering, and certain conclusions can't be made without fully destroying the cam, and then sawing the head in half to inspect it. I guess I wanna know whether the distance from center has a direct correlation to failure, and want to have someone look at my cams. Would you be interested / have the time to do that Aric?
If you do, I'd send you a bunch of cams to play with, with the hopes that they not be utterly destroyed..... and perhaps a better understanding of which ones could be more dangerous than the others.
Thanks
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philbox
Moderator
Jun 17, 2009, 8:21 AM
Post #109 of 190
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jt512 wrote: ...to really work like a cam? Or maybe it would. After all hexes hold in parallel cracks. Jay
The difference being though that a hex would apply a torque to the sides of the crack whereas the pictured cam would in effect be pulling without that same torque. It would in effect be a parallel slug of alloy being pulled in an entirely centered manner.
That might be an interesting pull test, how well would a hex hold in the crack test fixture.
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hansundfritz
Jun 17, 2009, 1:08 PM
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cracklover wrote: I agree with Aric, though. Something is allowing the cams to slip, and it certainly seems to vary from cam to cam. I just don't think we've put our finger on what that key variable, or variables set is, yet. And it's distinctly possible that with such a small dataset, it may not be possible to find it for certain.
Only the manufacturer has the resources to generate a robust dataset!
The irony here is that so much is apparently wrong that it is difficult to determine which of the problems accounts for the slippage. I'm no engineer or stats guy, but the hardness of the axles seems to be a leading candidate.
Aric: what about the suggestions made up-thread to flatten the axles so that your hardness tester will work? Does the finished surface matter? Would any heating from the flattening process change the properties of the metal? In any case, you can always send them out later to see if your results were accurate.
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cracklover
Jun 17, 2009, 3:09 PM
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jt512 wrote: cracklover wrote: jt512 wrote: cracklover wrote: Aric, the trouble I'm having is that I don't see any correlation between effective cam angle and the point at which the cam slipped. We wouldn't expect to see a correlation between cam angle and the applied force at which the cam slipped. Accoding to Vaino Kodas's equations, there is no relationship between the applied force at which a cam would slip cam angle. If the cam angle is less than a critical value, the cam will not slip at any applied force; if the cam angle is greater than the critical value, the cam will slip at any applied force. Let's say the point at which the angle is too great is 30 degrees. If the effective cam angle starts at 29, a little deformation, and presto, you're over the line. So the closer to that magic number, the less force should be required to push you over it. But... that's not exactly what we're seeing. Now if the relative hardness of the cam lobes is a much bigger factor, then it might erase any correlation based on the starting effective angle. But... I don't see any correlation based on either a combination of the two, or on either individually. In reply to: I wonder if it isn't so much a function of the flat spots on the cam increasing the cam angle as it the flat spots making the cam essentially no longer a cam. Would you expect something like this... [img]http://www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09_broken_left.JPG[/img] ...to really work like a cam? Or maybe it would. After all hexes hold in parallel cracks. How exactly that flat spot affects the "friction" is waaaay beyond my paygrade. I'm really just a DBA/developer with a halfway decent grasp of basic physics and a good head for problem-solving. I agree with Aric, though. Something is allowing the cams to slip, and it certainly seems to vary from cam to cam. I just don't think we've put our finger on what that key variable, or variables set is, yet. And it's distinctly possible that with such a small dataset, it may not be possible to find it for certain. GO Well if it's cam angle, then, according to theory, you should be able to put the cam back in the jig, with the flat spots on the cam lobes against the test surfaces, and the cam should pull out under any force.
That's an excellent point. Aric, is this something you tried at any point with the cams that slipped out? And are there any that slipped out that are in good enough shape that they could be put in the tester, or were they all too dismantled afterwards for other testing purposes?
In reply to: A note on the cam angles in your table: they probably are unreliable. Consider all the sources of error in them: error in camera angle, error in point selection, error in estimating the % retraction of the cams in the jig, error in estimating the test % retraction point in the photo, and error in estimating the cam angle at the estimated % retraction point. These errors attenuate the correlation between the true tested cam angle and the estimated tested cam angle; and hence, would attenuate any observed correlation between estimated cam angle and maximum force held. So even if there were actually a correlation between the tested cam angle and maximum force held, it could be obliterated by the cumulative effects of sources of error in the determination of the tested cam angle. Jay
I'll agree with you to a point - the angle I'm estimating has a wide margin for error. But not so much so (IMO - I know our opinions differ on this) that it should wipe out any strong correlation. I'd estimate a margin of error no greater than 5 to 10 degrees.
Of course if there's a slim correlation between pullout force and effective cam angle, and not much differentiation between the best and worst effective angles (in this case, from 14 to 23 degrees, or not much more than the margin of error) then you'd need a big sample for the average of the errors to disappear.
I'd suggest that in any future tests you do, Aric, if it's possible to get a photo of the cam in the rig - shot straight on to the axle - before pulling, that would give us an actual measurable effective cam angle.
But if the theory holds true that the cams are slipping out when they get flat enough to go past the Kodas point, then any cams that start out with an angle close to that should fail at a much lower force. It's not necessary to get good precision on that one. Unfortunately, I don't know what that Kodas point is for Aric's rig. The number 30 degrees was being bandied around - but was that for cam on rock, or cam on steel?
GO
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jt512
Jun 17, 2009, 3:58 PM
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cracklover wrote: jt512 wrote: cracklover wrote: jt512 wrote: cracklover wrote: Aric, the trouble I'm having is that I don't see any correlation between effective cam angle and the point at which the cam slipped. We wouldn't expect to see a correlation between cam angle and the applied force at which the cam slipped. Accoding to Vaino Kodas's equations, there is no relationship between the applied force at which a cam would slip cam angle. If the cam angle is less than a critical value, the cam will not slip at any applied force; if the cam angle is greater than the critical value, the cam will slip at any applied force. Let's say the point at which the angle is too great is 30 degrees. If the effective cam angle starts at 29, a little deformation, and presto, you're over the line. So the closer to that magic number, the less force should be required to push you over it. But... that's not exactly what we're seeing. Now if the relative hardness of the cam lobes is a much bigger factor, then it might erase any correlation based on the starting effective angle. But... I don't see any correlation based on either a combination of the two, or on either individually. In reply to: I wonder if it isn't so much a function of the flat spots on the cam increasing the cam angle as it the flat spots making the cam essentially no longer a cam. Would you expect something like this... [img]http://www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09_broken_left.JPG[/img] ...to really work like a cam? Or maybe it would. After all hexes hold in parallel cracks. How exactly that flat spot affects the "friction" is waaaay beyond my paygrade. I'm really just a DBA/developer with a halfway decent grasp of basic physics and a good head for problem-solving. I agree with Aric, though. Something is allowing the cams to slip, and it certainly seems to vary from cam to cam. I just don't think we've put our finger on what that key variable, or variables set is, yet. And it's distinctly possible that with such a small dataset, it may not be possible to find it for certain. GO Well if it's cam angle, then, according to theory, you should be able to put the cam back in the jig, with the flat spots on the cam lobes against the test surfaces, and the cam should pull out under any force. That's an excellent point. Aric, is this something you tried at any point with the cams that slipped out? And are there any that slipped out that are in good enough shape that they could be put in the tester, or were they all too dismantled afterwards for other testing purposes? In reply to: A note on the cam angles in your table: they probably are unreliable. Consider all the sources of error in them: error in camera angle, error in point selection, error in estimating the % retraction of the cams in the jig, error in estimating the test % retraction point in the photo, and error in estimating the cam angle at the estimated % retraction point. These errors attenuate the correlation between the true tested cam angle and the estimated tested cam angle; and hence, would attenuate any observed correlation between estimated cam angle and maximum force held. So even if there were actually a correlation between the tested cam angle and maximum force held, it could be obliterated by the cumulative effects of sources of error in the determination of the tested cam angle. Jay I'll agree with you to a point - the angle I'm estimating has a wide margin for error. But not so much so (IMO - I know our opinions differ on this) that it should wipe out any strong correlation. I'd estimate a margin of error no greater than 5 to 10 degrees.
Since the measured angles ranged from 15 to 23 degrees, then errors ranging from 5 to 10 degrees would be huge. For example, it would be possible for the cams with the largest measured angles in the sample to actually have the smallest angles. Random error of this magnitude would seriously attenuate correlation coefficients.
In reply to: Of course if there's a slim correlation between pullout force and effective cam angle, and not much differentiation between the best and worst effective angles (in this case, from 14 to 23 degrees, or not much more than the margin of error) then you'd need a big sample for the average of the errors to disappear.
Random error always attenuates correlation. The errors don't average out with larger sample size.
In reply to: The number 30 degrees was being bandied around - but was that for cam on rock, or cam on steel?
31 degrees for aluminum/steel, based on Kodas.
Jay
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cracklover
Jun 17, 2009, 6:10 PM
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jt512 wrote: Since the measured angles ranged from 15 to 23 degrees, then errors ranging from 5 to 10 degrees would be huge. For example, it would be possible for the cams with the largest measured angles in the sample to actually have the smallest angles. Random error of this magnitude would seriously attenuate correlation coefficients.
I agree, as I said in my that post (I'm afraid I threw you off with that erroneous bit about a larger sample size.)
Really, you can see quite well from Aric's photos the point at which the outer edge of the cam touches the fixture. Being off by a small amount in my estimate on where the cam meets the fixture would typically only result in a difference of 1 degree cam angle. So the only issue is how well the photos he used to generating the cam angles centered on the axle.
That's where I'm getting my estimate of 5-10 degrees of error from, but I'll let Aric speak to that. Putting them on a scanner would, of course, solve the problem, but it's a little too late for that!
GO
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adatesman
Jun 17, 2009, 8:15 PM
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adatesman
Jun 17, 2009, 8:27 PM
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cracklover
Jun 17, 2009, 8:41 PM
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adatesman wrote: cracklover wrote: That's an excellent point. Aric, is this something you tried at any point with the cams that slipped out? And are there any that slipped out that are in good enough shape that they could be put in the tester, or were they all too dismantled afterwards for other testing purposes? No, I haven't tried it. It would be easy enough to reassemble one of the not-so-mangled ones to see what it does, so I'll give it a try. I doubt it will hold much of anything so don't think having half the head cut away will make a difference.
Cool.
In reply to: In reply to: I'd suggest that in any future tests you do, Aric, if it's possible to get a photo of the cam in the rig - shot straight on to the axle - before pulling, that would give us an actual measurable effective cam angle. Unfortunately the bolts in the side of the fixture are a bit too close together to get a good pic that way. That said I'll give it a try next time anyway.
I see. Not an insoluble problem though. The cam doesn't have to be positioned as it will be when being pulled. Turn it sideways and the cam angle will still be the same.
In reply to: In reply to: Unfortunately, I don't know what that Kodas point is for Aric's rig. The number 30 degrees was being bandied around - but was that for cam on rock, or cam on steel? 31 degrees is for aluminum on steel, so directly applicable to the fixture. Aluminum on rock is ~17 degrees.
Hmm, that gives me an idea...
GO
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adatesman
Jun 18, 2009, 12:35 AM
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angry
Jun 18, 2009, 1:37 AM
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The dark vs light axle issue is just one of sandblasting if I remember correctly. Axles were sandblasted then they stopped. Probably makes it easier to tell whether they'd been hardened or not.
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blondgecko
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Jun 18, 2009, 12:12 PM
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I just had an idea about the relationship between Rockwell hardness and strength. In particular, the question occurred to me: is it a linear relationship? So I went looking here - in particular at aluminium alloys 6061-T4, -T6 and -T8. Here's what I found:
6061-T4
Hardness: Vickers 75 (~HRB 9-10)
Shear strength: 165 MPa
6061-T6
Hardness: HRB60
Shear strength: 207 MPa
6061-T8
Hardness: HRB75
Shear strength: 185 MPa
Interesting, no?
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adatesman
Jun 18, 2009, 2:45 PM
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cracklover
Jun 18, 2009, 3:24 PM
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Okay, now we're getting somewhere. So I think I've had an "ah ha!" moment.
Please bear with me, this post is kinda long...
If we assume that the surface texture has the effect of increasing the friction required before the cam will slip (I think we all can agree on that, even if we don't agree on whether to call it "friction" or "shearing" or "abrasion") then I think the pics I posted above tell a pretty good story.
It would appear that the effective cam angle at which the cam lobes will slip under load in Aric's fixture is somewhere from 31 to 39 (with a tight grouping around 35-37 degrees).
This points to a good candidate for why Aliens slip out while other cams break first:
1 - The other cams tested had consistently harder lobes, meaning that as the cam lobes deformed, it would have taken more force to get the point where the effective cam angle reached 35 degrees.
Despite the fact that there was a good deal of variance in the softness of Alien lobes, *all* were significantly softer than those of the other cams (correct me if I'm wrong here, Aric).
2 - For the most part, the other cams tested were larger. A larger cam requires a larger volume of metal be deformed before the flat section of the lobe is big enough to create the effective cam angle of 35 degrees. Deforming more metal takes more force.
The cams that pulled out at the lowest forces were all among the smallest cams Aric tested: All the blacks and blues pulled at the lowest ratings, and then many of the yellow Aliens did too.
3 - All of the Aliens tested had an effective cam angle greater than the angle of the other cams. This means that before deformation of the cam lobe even begins, the cam is closer to the point of reaching the critical angle of 35 degrees. The higher the starting angle, the less metal needs to be deformed to reach the critical point. Which again, means less force required.
Even if the method of measuring the affect of the misdrilled axles on effective cam angle is imprecise, there's little doubt that in almost all of these samples, it resulted in a larger starting cam angle. Perhaps we don't have enough precision to predict the variance from cam to cam, without laying the lobes flat on a scanner bed, but on average, they were pretty consistently off in the direction of too high a cam angle.
In summary, I believe that the three factors I listed above combined to create the "perfect storm" required to allow the cam lobes to deform enough to reach the "Kodas point" of around 35 degrees. Whereas the other brands of cams tested were not subject to those three factors, and so they failed due to another means before their lobes could be deformed enough for them to pull out.
GO
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adatesman
Jun 18, 2009, 3:37 PM
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cracklover
Jun 18, 2009, 3:52 PM
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If I am right, then the method you're using to test hardness is exactly the right one. It's a measure of how much force is required to deform a set amount of metal. This is exactly the question that determines how much force is required to flatten the lobes enough.
Shear force could enter the equation, though, if the metal is so soft that it begins to smear off at a force lower than the force required to deform enough metal to reach the "Kodas point".
GO
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jt512
Jun 18, 2009, 5:27 PM
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cracklover wrote: 3 - All of the Aliens tested had an effective cam angle greater than the angle of the other cams. This means that before deformation of the cam lobe even begins, the cam is closer to the point of reaching the critical angle of 35 degrees. The higher the starting angle, the less metal needs to be deformed to reach the critical point. Which again, means less force required. Even if the method of measuring the affect of the misdrilled axles on effective cam angle is imprecise, there's little doubt that in almost all of these samples, it resulted in a larger starting cam angle. Perhaps we don't have enough precision to predict the variance from cam to cam, without laying the lobes flat on a scanner bed, but on average, they were pretty consistently off in the direction of too high a cam angle.
We have no evidence that cam angle in this sample is predictive of failure load. I have conducted a regression of failure load on cam angle, adjusted for strength rating, and the p-value for cam angle is 0.81. Cam angle is completely insignificant in the sample. Its effect has either been obliterated by measurement error, is swamped out by the harness issue, or a combination of both; or, its effect is physically insignificant, as long as the angle is sufficiently less than the critical angle. I suspect that its effect really is insignificant or that what little effect there is has masked by the hardness issue. Regressing failure load on hardness, again adjusting for strength rating, the effect of hardness on failure load is in the expected direction (harder is better). The effect is not statistically significant, but the p-value is 0.12, low enough to suggest that the effect may be real, but that we need a bigger sample size to detect it.
Jay
(This post was edited by jt512 on Jun 18, 2009, 5:36 PM)
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adatesman
Jun 18, 2009, 5:36 PM
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dynosore
Jun 18, 2009, 5:40 PM
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jt512if you don't mind, what would the sample size have to be for us to be 95% confident these results are +/- 1kn, based on the variability in the data? Hopefully that made sense. I can't remember how to calculate n.....it seems like the sample is big enough to draw conclusions, but I'm rusty.
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healyje
Jun 18, 2009, 5:48 PM
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adatesman wrote: Dammit Cracklover, you're making me want to go do more testing!
I can send a half dozen older Metolius and a #1 Master cam that was stuck in a crack for a year, assaulted by various parties, and finally funked out of the slot.
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cracklover
Jun 18, 2009, 5:49 PM
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jt512 wrote: cracklover wrote: 3 - All of the Aliens tested had an effective cam angle greater than the angle of the other cams. This means that before deformation of the cam lobe even begins, the cam is closer to the point of reaching the critical angle of 35 degrees. The higher the starting angle, the less metal needs to be deformed to reach the critical point. Which again, means less force required. Even if the method of measuring the affect of the misdrilled axles on effective cam angle is imprecise, there's little doubt that in almost all of these samples, it resulted in a larger starting cam angle. Perhaps we don't have enough precision to predict the variance from cam to cam, without laying the lobes flat on a scanner bed, but on average, they were pretty consistently off in the direction of too high a cam angle. We have no evidence that cam angle in this sample is predictive of failure load. I have conducted a regression of failure load on cam angle, adjusted for strength rating, and the p-value for cam angle is 0.81. Cam angle is completely insignificant in the sample. Its effect has either been obliterated by measurement error, or swamped out by the harness issue, or a combination of both. I suspect that it is has mainly been masked by the hardness issue. Regressing failure load on hardness, again adjusting for strength rating, the effect of hardness on failure load is in the expected direction (harder is better). The effect is not statistically significant, but the p-value is 0.12, low enough to suggest that the effect may be real, but that we need a bigger sample size to detect it. Jay
As we agreed before, I think the margin for error is too big compared to the range of values to see a statistically significant difference in pullout based on measured cam angle.
But you missed my point, (or I didn't make it clearly enough) which is that 1 - Based on the geometry of the Alien cam lobes, the angle starts off higher than that of other cams, and 1(a) even if the margin for error is too great to see a nice even progression, that doesn't change the fact that overall, the cams have an effective cam angle that's even higher than they would if the lobes were drilled properly.
So it's reasonable to assume that this plays a significant factor in explaining why the *overall population* of Aliens pull out before something else on the cams break.
Perhaps if Aric scans in the lobes, we can get a more precise measurement of axle hole to work with. Then we could see if that gets rid of enough slop in the numbers to improve the statistical correlation.
GO
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jt512
Jun 18, 2009, 6:21 PM
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cracklover wrote: jt512 wrote: cracklover wrote: 3 - All of the Aliens tested had an effective cam angle greater than the angle of the other cams. This means that before deformation of the cam lobe even begins, the cam is closer to the point of reaching the critical angle of 35 degrees. The higher the starting angle, the less metal needs to be deformed to reach the critical point. Which again, means less force required. Even if the method of measuring the affect of the misdrilled axles on effective cam angle is imprecise, there's little doubt that in almost all of these samples, it resulted in a larger starting cam angle. Perhaps we don't have enough precision to predict the variance from cam to cam, without laying the lobes flat on a scanner bed, but on average, they were pretty consistently off in the direction of too high a cam angle. We have no evidence that cam angle in this sample is predictive of failure load. I have conducted a regression of failure load on cam angle, adjusted for strength rating, and the p-value for cam angle is 0.81. Cam angle is completely insignificant in the sample. Its effect has either been obliterated by measurement error, or swamped out by the harness issue, or a combination of both. I suspect that it is has mainly been masked by the hardness issue. Regressing failure load on hardness, again adjusting for strength rating, the effect of hardness on failure load is in the expected direction (harder is better). The effect is not statistically significant, but the p-value is 0.12, low enough to suggest that the effect may be real, but that we need a bigger sample size to detect it. Jay As we agreed before, I think the margin for error is too big compared to the range of values to see a statistically significant difference in pullout based on measured cam angle. But you missed my point, (or I didn't make it clearly enough) which is that 1 - Based on the geometry of the Alien cam lobes, the angle starts off higher than that of other cams, and 1(a) even if the margin for error is too great to see a nice even progression, that doesn't change the fact that overall, the cams have an effective cam angle that's even higher than they would if the lobes were drilled properly.
No. I don't think I missed your point. Rather, I don't think the effective cam angles in the sample have an important effect on failure load—at least not when the plates are steel. So far, all the evidence points to lobe hardness. Your measurements of the "final" cam angles all modestly exceeding the critical angle, 31 degrees, are highly suggestive, I think, that the softness of the cam lobes is the most important predictor, after strength rating, of failure load. (And, I suspect that strength rating is a surrogate measure of cam size—the smaller the cam, the lower the failure load, since it takes less flattening to reach the critical angle.) Now, when the plates are granite, and the effective cam angle closer to the critical angle, we may see an effect of cam angle.
In reply to: So it's reasonable to assume that this plays a significant factor in explaining why the *overall population* of Aliens pull out before something else on the cams break.
I doubt it. It seems to me that the main reason that Aliens pull out, whereas other brands break, is because the Alien cam lobes are softer. Hence, they flatten out, attain the critical angle, and pull out. In contrast, other brands, having harder lobes, flatten less, do not attain the critical angle, and break before pulling out (at least that's what I suspect, since I haven't looked carefully at the non-Alien data).
In reply to: Perhaps if Aric scans in the lobes, we can get a more precise measurement of axle hole to work with. Then we could see if that gets rid of enough slop in the numbers to improve the statistical correlation.
I'll certainly rerun the analysis if he can provide that data.
Jay
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jt512
Jun 18, 2009, 6:46 PM
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adatesman wrote: So here's a question for you all... I've got Healyje's 4 Hybrids plus the possibility of a couple regular ones from the 90's headed my way in the very near future. I just ordered 2 pair of granite inserts for my fixture, which should be ready next week, so do we test the additional samples the same as the others so that we have a larger data set or test them on the granite?
I think that an important hypothesis to test is that the softer Alien cam lobes are an advantage in real rock. That's their claim isn't it: that they "bite" better? The question is would using granite inserts in your test rig be a valid test of the behavior of Aliens in a natural crack?
Testing in granite would also help to determine the importance of mislocatation of the axle, since the cam angle will be closer to the critical angle.
Also, testing them in granite does not necessarily preclude combining them with the steel data for analysis. With a sufficiently large granite sample, I should be able to statistically control for the effect of the test surface. With just four units in the granite sample, the statistical adjustment might be problematic. Six would be a lot better than four, and eight would be a lot better than six. Additionally, the granite sample should be comparable to the steel sample in terms of size and design. I'm a little concerned about using mostly hybrids in the granite sample, since there were few hybrids in the steel sample. Therefore, to the extent that "hybrid" has an effect, it will be confounded with the "granite" effect.
In reply to: EDIT- BTW, I'll be resurfacing the fixture to the UIAA max roughness either way.
Careful. If you make the roughness of the granite surface different than that of the steel surface, then the effect of roughness will be completely confounded with the effect of surface material. We won't be able to attribute differences in performance between the steel and granite samples to an effect of the surface material per se. All we will be able to say about any observed differences in performance is that they are due to a combination of the surface material and the surface roughness.
Jay
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cracklover
Jun 18, 2009, 6:50 PM
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Jay, if you accept that the Aliens slip out when the flattening of their cam lobes reaches a critical angle, then how can you discard the relevance of the starting cam angle? You may not agree with the methodology of measuring that cam angle, but at least theoretically, you must see that the greater the starting cam angle, the less metal must be displaced before the cam reaches the "Kodas point" and slips out of the fixture.
I mean, let's say that in Aric's fixture, a typical cam will pull out of when it gets to 35 degrees. Wouldn't you expect that a cam that started with an angle of 34 degrees, all other things being equal, would take much less force to pull out than one starting at 14 degrees?
GO
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adatesman
Jun 18, 2009, 8:02 PM
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jt512
Jun 18, 2009, 8:30 PM
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cracklover wrote: Wouldn't you expect that a cam that started with an angle of 34 degrees, all other things being equal, would take much less force to pull out than one starting at 14 degrees?
I would think so, but the relation between cam angle and failure load, for a given cam size, may not be linear. There may be a sort of threshold distance between the cam angle and the critical angle beyond which the effect of cam angle is negligible. Like I said in a previous post, if the tests are done in a granite jig, where the cam angles will be much closer to the critical angle, then we might be more likely observe an effect of cam angle. Regardless, I think that your hypothesis—that Aliens pull out of the test apparatus, whereas other brands of cam break, is mainly due to the actual cam angle of the Aliens being greater—is likely to be false. I suspect that the effect of cam hardness is much greater.
Another factor that could be obscuring the effect of cam angle in the current data is that the dataset does not include a good measure of cam size. The strongest predictor of failure load in the dataset is rated strength. Since, tentatively, most of the Aliens appear to fail as a result of flattening until the effective cam angle attains the critical angle, and the smaller the cam, the less flattening needs to occur for the critical angle to be attained; for any given cam angle, the smaller the cam, the lower the failure load. Therefore, in order to measure the effect of cam angle, the effect of cam size has to be well controlled. However, the best measure of cam size in the dataset is rated strength, an imprecise surrogate for cam size. Hence, the effect (if any) of cam angle is confounded with the effect of cam size in my regression analysis.
Having an accurate measure of cam size would likely be extremely valuable in teasing out the effect of angle on failure load. So, if you're willing to take on another little measurement project, measuring the cam sizes should prove very useful. I'm not sure what the best measure would be—perhaps the cam radius measured from the advertised calculated cam center to the edge of the cam at the midpoint of the cam's expansion range. Don't take measurements from the observed actual axle center, because that would confound cam size and cam angle.
Edit: I stated this wrong originally. The measurement of the radius should be from the true cam center, as determined by the software.
Jay
(This post was edited by jt512 on Jun 18, 2009, 8:45 PM)
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jt512
Jun 18, 2009, 8:35 PM
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adatesman wrote: cracklover wrote: Perhaps if Aric scans in the lobes, we can get a more precise measurement of axle hole to work with. Then we could see if that gets rid of enough slop in the numbers to improve the statistical correlation. Ok Cracklover, have at it. The scans of all the lobes are available here: Link.
See my previous post. I think getting an accurate measurement of cam size is going to be at least as important as getting a more accurate measurement of cam angle. Maybe Gabe can do both simultaneously.
Jay
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moof
Jun 18, 2009, 8:42 PM
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healyje wrote: adatesman wrote: Dammit Cracklover, you're making me want to go do more testing! I can send a half dozen older Metolius and a #1 Master cam that was stuck in a crack for a year, assaulted by various parties, and finally funked out of the slot.
Is that what finally happened to that yellow cam? Damn I worked on that thing for close to an hour and got 3/4 lobes to moves, but couldn't for the life of my see what was going on in the very back.
I think I have a few pieces I should donate too. I think I've got a wired bliss, and some other small crap.
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cracklover
Jun 18, 2009, 9:01 PM
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jt512 wrote: cracklover wrote: Wouldn't you expect that a cam that started with an angle of 34 degrees, all other things being equal, would take much less force to pull out than one starting at 14 degrees? I would think so, but the relation between cam angle and failure load, for a given cam size, may not be linear. There may be a sort of threshold distance between the cam angle and the critical angle beyond which the effect of cam angle is negligible.
Fair enough.
In reply to: Like I said in a previous post, if the tests are done in a granite jig, where the cam angles will be much closer to the critical angle, then we might be more likely observe an effect of cam angle.
Agreed.
In reply to: Regardless, I think that your hypothesis—that Aliens pull out of the test apparatus, whereas other brands of cam break, is mainly due to the actual cam angle of the Aliens being greater—is likely to be false.
I never said anything like that! I suggested three elements that could effect the amount of force required to flatten a lobe to 35 degrees. At no time did I make an estimate as to which of the three would have the largest impact.
In fact, from my first analytical post on the subject, I pretty much stated that more than anything else, "size matters"!
In reply to: However, the best measure of cam size in the dataset is rated strength, an imprecise surrogate for cam size. Hence, the effect (if any) of cam angle is confounded with the effect of cam size in my regression analysis.
No, the best measure of cam size is cam size. There were four grey Aliens and five yellow tested. So at least you have two small datasets controlled for size. but so far as I can see, even within those datasets, there is zero correlation to effective cam angle.
Still, when I have time, I'll go through Aric's latest pics of mangled cam lobes.
GO
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jt512
Jun 18, 2009, 9:56 PM
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cracklover wrote: In reply to: Regardless, I think that your hypothesis—that Aliens pull out of the test apparatus, whereas other brands of cam break, is mainly due to the actual cam angle of the Aliens being greater—is likely to be false. I never said anything like that!
You're right. I misread your statement.
In reply to: In reply to: However, the best measure of cam size in the dataset is rated strength, an imprecise surrogate for cam size. Hence, the effect (if any) of cam angle is confounded with the effect of cam size in my regression analysis. No, the best measure of cam size is cam size. There were four grey Aliens and five yellow tested. So at least you have two small datasets controlled for size.
Well, "green" and "yellow" aren't numbers. I need to know the actual size of the cam, since apparently it is the overarching effect. I think the best way to measure it would be the radius described in my earlier post, though I'm not sure.
Jay
(This post was edited by jt512 on Jun 18, 2009, 9:57 PM)
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adatesman
Jun 18, 2009, 10:03 PM
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jt512
Jun 18, 2009, 10:16 PM
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adatesman wrote: jt512 wrote: adatesman wrote: cracklover wrote: Perhaps if Aric scans in the lobes, we can get a more precise measurement of axle hole to work with. Then we could see if that gets rid of enough slop in the numbers to improve the statistical correlation. Ok Cracklover, have at it. The scans of all the lobes are available here: Link. See my previous post. I think getting an accurate measurement of cam size is going to be at least as important as getting a more accurate measurement of cam angle. Maybe Gabe can do both simultaneously. Jay Funny you should mention it, as I was just going through my pile of gear to see what's available to be sacrificed and it's easy enough to measure the spread on the fixture to calculate the radius.
Aric, if you test any hybrids, is it possible to get the spread at each lobe?
Jay
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adatesman
Jun 18, 2009, 10:40 PM
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jt512
Jun 18, 2009, 11:11 PM
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adatesman wrote: Yup, as suggested in one of these threads I'll put the pieces in the fixture horizontally for the pic so that we get good shots of exactly where the lobes are making contact. EDIT- That is, if I'm understanding what you're asking correctly...
Well, what I'm suggesting is that we get need some accurate measure of the radius of the cam. My suggestion was that it be at the midpoint of the cam's expansion range, but the actual contact point with the jig has merit too. I can see advantages and disadvantages to each way, with no clear winner. The problem with hybrids is that the lobes have different radii. I'm not sure what the best way to deal with than in the analysis would be, but the default options would be to average them. Regardless, we should know the radius of each lobe for hybrid cams, if that is possible.
Jay
(This post was edited by jt512 on Jun 18, 2009, 11:17 PM)
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jfield
Jun 19, 2009, 2:53 AM
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I would like to weigh in on the issue of cam slippage/changing cam angles/lobe deformation as I have thought about this problem over the years. (Full disclosure: I invented the Metolius Supercam and wrote the Cam Fitter, but I don't work for Metolius, and climbing is only a relatively minor pastime for me.)
It is definitely the case that misdrilled axle holes can - under the right circumstances - result in failure at predictably low loads. Metolius has seen that, and the physics is unequivocal. That said, I think it is important to keep perspective on the situation. Most aliens are good, most bad ones hold a sizable percentage of the rated strength, most falls generate less force than this - and almost all the climbing gear out there has Achille's heel type problems. I know of no major manufacturer - to a greater or lesser degree - that does not suffer from fundamental square one design weaknesses in their gear. My ire is raised in the case of the aliens however, by the combination of the several unrelated flaws, the length of time in years which this has gone unfixed, and the relative ease with which the flaws could be eliminated. Put together, I think this is a pretty disturbing picture.
To the present point, I believe the cams popping out of the fixture is a combined failure caused by the flat spotting occurring before the axle bending. If you had a force versus displacement curve on the cams, I believe you would find that there is an inflection point in the force as the force rises up past the point required to start bending the axle. At this time, the lobes have to take up a lot of slack very quickly, yet the force is not rising very quickly. As a result, the cam ceases to flat spot more and "climbs up" onto the leading edge of the flat spot. This is a very unstable situation because as people have noted the effective cam angle is much higher but also the contact patch area is greatly reduced. Now, at first, I imagine this process is in equilibrium, but as we pass the inflection point and the force starts to rise rapidly again, it becomes quite likely that the cam will pop - due to increased shear stress over the (now smaller) contact patch.
Why does the force start to rise rapidly again - e.g. why an inflection point? Because the cosine factor of the axle bend starts to become a big deal and further displacement is not working directly perpendicular to the axle any more - e.g. trying to stretch the axle.
For cam lobe materials, you would like something which has a shear strength that is on the same order as that of the working surface - perhaps a few times higher if the surface is macroscopically rough - than the material you are working against. e.g. aluminum versus rock. The reason is that this provides the most even distribution of loading across the largest contact patch. Hard on soft, or soft on hard are not as good. It turns out that aluminum is a good choice against rock - because it is kind of soft and squishy. In fact, I am very dubious that 7075 is an advantage, and I think that titanium would almost certainly be worse. Aluminum is not a good choice against a steel fixture. As a practical matter, these small cams will grind down into the rock of a placement but they cannot do so against the steel fixture. Therefore, I am not convinced that this particular "popping" failure would occur on rock.
From the standpoint of hypothesis testing on correlation, I believe that the important dependent term to study would be axle strength times cam lobe hardness divided by square root of cam radius of curvature. Tentatively, I don't think that you are going to be able to aggregate enough data to separate the magnitude of this term out from the first order terms of each of these independent variables in the presence of noisy results. So, absent some kind of analysis that suggests how many cams would be required to build up enough statistical power, I am pretty dubious.
For the geeky (and strong of will), take a look at Sec. 8 & 9 in Landau/Lifshitz Theory of Elasticity. Problem 9.2 on the line contact between cylinders can be perturbatively reformulated to include the effects of shear forces. The result is that the contact patch shift and therefore also the effective cam angle change is extremely small even for large deformations - at least in the elastic limit. So, tentatively, I conclude that flat spotting with a perfectly rigid axle and axle hole is probably not singly responsible for this failure.
People interested in building machine cams with moving/sliding axles or bearing surfaces should take note here. Ray Jardine's original invention is manifestly stable against all manner of insult and injury. There is no physical requirement that this is true for an arbitrary design in general however. Stability analysis is very important and surprisingly difficult to do properly.
cheers
John
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verticon
Jun 19, 2009, 8:10 AM
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The axle holes of the softer lobes were deformed during the test, as their edges were compressed with the same forces as for the fixture side (less deformation though, because of the even contact surface with the axle). So far, you've been looking for a correlation between the hardness of the lobes and the failure cam angle, ignoring the translation of the center point toward the fixture, but the angle is further increased by the ovalization of the axle hole.
I think this test has only an informative value, as far as it has to deal with so many variables which are masking one another. However, the test can be used to set a proper methodology for further tests.
IMHO this methodology would require (among others):
- A separate test for each size on a significant number of samples (mixed sizes = different qt. of deformed metal=errant results)
- Grouping of samples according to the axle hardness, measured before the test (to take out this variable for a given lot)
- A comparative study of each cam lobe geometry before and after testing (see the hole deformation point above)
What do you think about pull testing each individual lobe ? It could be mounted on an axle between two ball-bearings which would roll on one (smooth) side of the fixture, while the cam would press on the other side and you pull on the axle with some king of a U stem. This way, you only have to deal with the lobe properties (and I guess you already have a lot of samples by now)
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adatesman
Jun 19, 2009, 1:16 PM
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cracklover
Jun 19, 2009, 1:35 PM
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adatesman wrote: cracklover wrote: Perhaps if Aric scans in the lobes, we can get a more precise measurement of axle hole to work with. Then we could see if that gets rid of enough slop in the numbers to improve the statistical correlation. Ok Cracklover, have at it. The scans of all the lobes are available here: Link A couple notes on the scans: 1. The side scanned is the side with less apparent deformation, and in cases where the axle is bent the deformation on the other side could be significant. 2. The reason for this that I needed to clean the edge up with a dremel so that it would sit on the hardness tester properly. 3. The numbers in the pics correspond to the numbers in the hardness tests (the lobes are labeled on the other side). 4. Sample 22 has no numbers as I couldn't do a hardness test on it. 5. Buckled and cracked lobes are notated. 6. Some of the slightly bent axles may not be apparent as the bend wasn't enough to catch on the plate of the scanner and rotated all the way downward.
Just a quick followup on this.
I've been processing the images, but it takes a while, and I'm only partway done. Some interesting facts, though:
1 -The photos taken by Aric straight on and then run through the middle-analyzer software gave results that are qualitatively very similar to what I see on the scanner image. So, for example if his original image showed a theoretical center point that's 3mm up and right of the true axle, invariably that's what I see in my analysis of the images taken from the scanner.
However...
2 - There are very small changes. And those can, depending on the specific relationship between the theoretical center and the true axle center, equal quite significant changes in effective cam angle.
I'll probably post my results later today.
GO
(This post was edited by cracklover on Jun 19, 2009, 8:58 PM)
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hansundfritz
Jun 19, 2009, 2:06 PM
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Aric: I don't personally know Larry at Mtn Tools -- except from having called him up to buy stuff. He's approachable and likes a good chat.
As for measuring the size of the lobes: One approach might be to simply measure their total volume, which would yield a variable that would perform better in a regression analysis than "Green" or "Yellow" (!). It might also be useful to have a variable for the width of the cam surface that contacts the rock/fixture.
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hafilax
Jun 19, 2009, 5:35 PM
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Thanks jfield. Very interesting reading. It's great to hear a different perspective on all of this.
Another effect of the axle bending seems to be that the lobes rotate perpendicular to the axle. This further reduces the contact area increasing the likelihood of shearing.
If you don't think that this 'popping out' would happen on rock, is there a better way to pull test Aliens? Will Aric's rock test jig faces yield different results?
If the rock is able to deform along with the cam lobes I'm guessing that it would form a little pocket for the cam to work against improving the holding power beyond the simple parallel crack model.
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adatesman
Jun 19, 2009, 5:57 PM
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hafilax
Jun 19, 2009, 6:19 PM
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You don't think that crystals break or crush or that sandstone displaces or that flakes flex etc. Rock deformation is an issue IMO which is why different cam widths work differently in different rock types. Metolius' fat cams come to mind.
I was basing the question off of what jfield wrote. He stated that a steel fixture is a poor substitute for rock because their shear modulae are so different and that aluminum happens to be a good choice for rock.
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cracklover
Jun 19, 2009, 8:59 PM
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I wrote: I'll probably post my results later today. GO
Sorry, the dorrington cam software has been on the fritz all day today. I've got an email in to the guy who runs it, but even if he fixed it now, there's no way I'd be able to finish processing pics before the end of the day.
GO
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boku
Jun 19, 2009, 9:51 PM
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cracklover wrote: ...Sorry, the dorrington cam software has been on the fritz all day today...
Thanks, I was wondering about that. I shot axle-on photos of all my cams except the Camalots, and was trying to run analysis on them but got nowhere. Now I know why.
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adatesman
Jun 19, 2009, 10:02 PM
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jfield
Jun 19, 2009, 10:16 PM
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Sorry! I broke the software. It's fixed now.
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cracklover
Jun 19, 2009, 10:34 PM
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adatesman wrote: Strange thing being the one pic I ran while Gabe/Cracklover was first having problems went though just fine. A week or so ago I got an email from him saying he had moved on to other things due to lack of anyone's interest in the matter, and now that lots of people are interested in the mis-centered axle thing it wouldn't surprise me if he's finishing it off. Never met/talked with him, but he seems like a nice guy from the emails I've gotten, not to mention scary-smart.
The "him" in the second sentence appeared to refer to me. I was confused about exactly who you were referring to, in the rest of your post...
Until I read the last phrase. Then I knew you couldn't possibly be talking about me!
G
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adatesman
Jun 19, 2009, 10:38 PM
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cracklover
Jun 20, 2009, 9:35 PM
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I've spent a good bit of time analyzing the cam lobes Aric photoed by placing flat on the scanner. I wanted to use these photos to get an effective cam angle, because they're much more accurate than the numbers I was getting off his earlier photos.
It looks like now that I've gotten cam angle to be a bit more precise, within a cam size, there may be some small correlation to effective cam angle after all.
I'll be posting a separate thread in the Lab for my results, and I'll edit this post to add a link.
Edited to take back some over-the-top language that I used before looking closely at the data earlier.
GO
(This post was edited by cracklover on Jun 21, 2009, 3:58 AM)
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landongw
Jun 21, 2009, 6:24 AM
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I hate to say this, but...From what I can see the control in this study is too small (and notably not cited) to give me any confidence in the results.
For every fixture setting, there should be a control to rule out errors in the setting of the fixture. Having an adequate control group is a fundamental part of the scientific method. Without it, any results are questionable at best.
The only definitive part of this test, in my mind at least, are the photos of stem cross sections. 10% of the test samples not having a good braze ensures that I will never be climbing on aliens, ever.
Having said all that, I think that this test does introduce enough doubt about aliens to, hopefully, motivate the UIAA into doing a thorough review.
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verticon
Jun 21, 2009, 9:55 AM
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Hi Aric,
Would you care to discuss the notes I posted somewhere up this page ?
verticon wrote: The axle holes of the softer lobes were deformed during the test, as their edges were compressed with the same forces as for the fixture side (less deformation though, because of the even contact surface with the axle). So far, you've been looking for a correlation between the hardness of the lobes and the failure cam angle, ignoring the translation of the center point toward the fixture, but the angle is further increased by the ovalization of the axle hole. I think this test has only an informative value, as far as it has to deal with so many variables which are masking one another. However, the test can be used to set a proper methodology for further tests. IMHO this methodology would require (among others): - A separate test for each size on a significant number of samples (mixed sizes = different qt. of deformed metal=errant results) - Grouping of samples according to the axle hardness, measured before the test (to take out this variable for a given lot) - A comparative study of each cam lobe geometry before and after testing (see the hole deformation point above) What do you think about pull testing each individual lobe ? It could be mounted on an axle between two ball-bearings which would roll on one (smooth) side of the fixture, while the cam would press on the other side and you pull on the axle with some kind of a U stem. This way, you'd only have to deal with the lobe properties (and I guess you already have a lot of samples by now) |
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jt512
Jun 21, 2009, 11:20 PM
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verticon wrote: I think this test has only an informative value, as far as it has to deal with so many variables which are masking one another.
In principle, the effects of those variables can be sorted out using multivariable statistics.
In reply to: IMHO this methodology would require (among others): - A separate test for each size on a significant number of samples (mixed sizes = different qt. of deformed metal=errant results) - Grouping of samples according to the axle hardness, measured before the test (to take out this variable for a given lot)
Separate tests aren't needed, just a proper statistical analysis.
Jay
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verticon
Jun 22, 2009, 7:35 AM
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jt512 wrote: In principle, the effects of those variables can be sorted out using multivariable statistics. Separate tests aren't needed, just a proper statistical analysis. Jay
It depends on the purpose of the test.
Indeed, multivariable statistics can be used to answer the question "How safe are the Aliens?" The actual test's conclusion is: Aliens are not safe to use (thus it has an informative value).
But for the question "what's wrong with the Aliens?" I would do separate tests. (I guess this is what UIAA would want to know)
Aric already made a separate test for the stems, as their strength has nothing to do with the cam heads, didn't he ?
So far, for the heads we have too many rabbits to catch:
- Axle hardness,
- lobe hardness
- position of the axle hole (which gives a large array of angles)
- contact surface (which differs by cam size)
I was thinking that by taking the axle and the sizes apart, the test would be able to tell more about the relationship between the lobe geometry and the hardness of the alloy.
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jt512
Jun 22, 2009, 10:01 AM
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verticon wrote: jt512 wrote: In principle, the effects of those variables can be sorted out using multivariable statistics. Separate tests aren't needed, just a proper statistical analysis. Jay It depends on the purpose of the test. Indeed, multivariable statistics can be used to answer the question "How safe are the Aliens?" The actual test's conclusion is: Aliens are not safe to use (thus it has an informative value). But for the question "what's wrong with the Aliens?" I would do separate tests. (I guess this is what UIAA would want to know) Aric already made a separate test for the stems, as their strength has nothing to do with the cam heads, didn't he ? So far, for the heads we have too many rabbits to catch: - Axle hardness, - lobe hardness - position of the axle hole (which gives a large array of angles) - contact surface (which differs by cam size) I was thinking that by taking the axle and the sizes apart, the test would be able to tell more about the relationship between the lobe geometry and the hardness of the alloy.
I know what you were thinking and you are wrong. You can combine the data and use statistical modeling to estimate the effects of interest, and it is more efficient to do so.
Jay
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verticon
Jun 22, 2009, 1:11 PM
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jt512 wrote: I know what you were thinking and you are wrong. You can combine the data and use statistical modeling to estimate the effects of interest, and it is more efficient to do so. Jay
OK, you're the one into statistics here, I only rely on common sense, so I admit that I might be wrong.
We can identify two major failure modes, not related to one another: from 21 samples, 5 had a cable/braze problem (and only one of them - which was old and used - was under rating).
If we take those away (and the offsets too, because they are not meant to be placed between parallel plates), we are left with 14 samples, which all pulled from the fixture with flat spots on the lobes and a more or less bent axle, and some of them with buckled lobe(s).
Could you explain how do you draw statistically meaningful conclusions from such a small number of samples and that many variables involved (hardness of the lobes and axle, lobe geometry and size, axle hole) ?
If you do draw conclusions, I'd be glad to hear from you what are the causes of the failure by pulling from the jig under the rated strength and how likely is for each of the causes to happen in the real world ? Are there any sizes that are more likely to fail than the others ? Can you extrapolate the results for all the Aliens on the market or in use?
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jt512
Jun 22, 2009, 7:13 PM
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verticon wrote: jt512 wrote: I know what you were thinking and you are wrong. You can combine the data and use statistical modeling to estimate the effects of interest, and it is more efficient to do so. Jay OK, you're the one into statistics here, I only rely on common sense, so I admit that I might be wrong. We can identify two major failure modes, not related to one another: from 21 samples, 5 had a cable/braze problem (and only one of them - which was old and used - was under rating). If we take those away (and the offsets too, because they are not meant to be placed between parallel plates), we are left with 14 samples, which all pulled from the fixture with flat spots on the lobes and a more or less bent axle, and some of them with buckled lobe(s).
There are three failure modes: braze, stem, and pull-out. I have excluded the one unit whose braze failed from all analyses. Stem failure is not a "problem" in this data set. The three units whose stems failed, failed at loads greater than their rated strength. Hence stem failure indicates lack of a problem. In a crude sense, these units are a sort of control group, and as such they are essential to the analysis. I see no reason to exclude the offsets because the cam lobes are logarithmic spirals, so the units should perform properly in a parallel crack.
Thus we have usable failure data on 20 units. Of these, we have angle data on 18 units, and after throwing out one outlier, hardness data on 17 units. One unit with hardness data has missing angle data. Therefore, we currently have 16 to 20 units in the sample, depending on the specific analysis.
In reply to: Could you explain how do you draw statistically meaningful conclusions from such a small number of samples and that many variables involved (hardness of the lobes and axle, lobe geometry and size, axle hole) ?
You are correct that the small sample size limits what we can do with the data. We can probably only consider two factors simultaneously in any model. Nonetheless, combining cam sizes in the analysis is far more efficient than doing separate analyses by size, as you suggested. If we need N units in the combined analysis, and we have n cam sizes, then we would need roughly n*(N-1) units to do separate analyses by cam size, and then we wouldn't be able to explain the effect of cam size on failure load. Multivariable statistical analysis is precisely the tool needed to sort out the effects of multiple factors and failure load.
Jay
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notapplicable
Aug 15, 2010, 6:25 AM
Post #167 of 190
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adatesman wrote: As before, a couple of ground rules: - This is The Lab and this thread will be highly moderated, as is customary for The Lab.
- The purpose of this post is to keep you informed and safe, not to bash CCH. What happened with threads here on RC during the dimpled head recall did not do anyone any good and served only to bury important information under pages and pages of ugliness.
- Posts/threads of an unhelpful nature either here in The Lab or elsewhere on RC will be removed as correct information needs to be kept accessible.
- These tests were performed by me, witnessed by at least a dozen people who happened to stop in at Rock & Snow while the testing was being performed.
- And before anyone starts with accusations of bias, a summary of the test results was sent to CCH shortly after the testing was finished to allow them the opportunity to take ownership of these issues. My only concern is the possibility of faulty gear being out in circulation and feel that these results should be made public so that people can make informed decisions regarding their safety and equipment.
EDIT- There is now a PDF version of this report available that is much easier to read than what was necessary to get it into this forum thread format. I've also made the raw data available for anyone who wants it. Feel free to use any of it, but if it gets published somewhere kindly credit me...
Report: Link
Spreadsheet: Link
Unless you’ve been living in a cave for the past few weeks, you’ve probably heard about the pair of Aliens which failed below spec while I was testing gear at the New River Rendezvous (5/16/09). You have probably also heard that I took the puller up to Rock & Snow in New Paltz, NY to do some more testing (5/26/09), and what you’re reading now are the long-awaited results. There’s a lot to cover, so I’ll be doing things a bit differently this time and simply discussing the failure modes and their implications rather than getting into the details of each individual piece. All of the details and pics are available in the following posts for anyone who wants them, and I highly encourage checking them out. Simply click on any of them for a large version. I'll be making the rest of the photos available online shortly and once they're up I'll add links to the albums. Oh, and my apologies for the photo-intensiveness and resulting long load times of this thread... No real way around it without leaving out the pics, which isn't really a good option in my mind. EDIT- All of the photos are now available here: Link to index There are ~500 of them, of which only a fraction of them are included in the article below, so if you're interested feel free to take a look. First and foremost we have to define what “failure” is for the purposes of this testing. The definition I’m using is when something breaks or the device pulls from the fixture during testing at a force under its rated strength. Per the CE/UIAA spec the rated strength is the minimum strength that the manufacturer guarantees a device will hold, so by definition a device that does not meet its published rating has failed. While there is some logic behind “almost held its rating” and “10kN is plenty”, the simple fact is that if Aliens are consistently failing below their rated strength then the ratings themselves are at best overly optimistic and at worst quite misleading. I do not know what method CCH uses to determine the ratings for their cams, but most of the other manufacturers use statistical methods such as 3 Sigma to determine a rating that some obscenely high percentage of pieces will meet or exceed easily. Not surprisingly, in testing I’ve done on gear from other manufacturers using the exact same equipment and fixtures and have gotten breaking strengths in excess of 110% of the rated strength. This should be par for the course, but unfortunately was not how the results of the Alien testing came out. Basically what it boils down to is that climbing is an inherently dangerous activity and decisions regarding acceptable risk are quite frequent. Often these decisions are made partly upon the rated strength of a device, which means that there could be very unpleasant consequences resulting from a device not meeting its rating. As such, ratings should be overly conservative if anything and in my opinion having devices consistently fail considerably below rating is simply unacceptable. On a related note, there is no such thing as Safety Factor or Safe Working Load when it comes to rating climbing equipment. Unless explicitly stated otherwise by the manufacturer the rating you’re seeing is a breaking strength and you should expect it to fail at any load above it. Gear will often break well above its breaking strength, but that’s due to how conservatively the manufacturer rates the gear to make sure it will always meet spec rather than some sort of government regulation that mandates a certain amount of padding be worked into the rating. With that now out of the way, the testing at Rock & Snow comprised 22 Aliens that were loaded into the crack fixture and pulled until either something broke or it came out of the fixture. Of those 22 cams, 13 were brand new and straight off the shelf at Rock & Snow (Thanks to everyone who contributed funds to make this happen and to Rich at Rock & Snow for giving us a discount on the test samples). The other 9 were used and donated for testing by their owners. All were in good working order with no apparent problems or defects. The full breakdown is as follows: Black: 1 new (4/08, Sample 7), one used (no date stamp but believed to be from the mid-1990’s, Sample 24)
Blue: 2 used (no date stamps but believed to be from the mid-1990’s, Samples 22 and 23)
Grey: 2 new (4/09, Samples 17 and 19), 2 used (12/04, 6/05, Samples 1 and 18)
Yellow: 3 new (5/09, Samples 8, 9 and 20), 2 used (5/99, 10/03, Samples 3 and 21)
Red: 2 new (5/09, Samples 12 and 14)
Orange: 1 used (no date stamp, but believed to be from the mid-1990’s, Sample 2)
Purple: 2 new (11/08, Samples 4 and 5)
Clear: 1 new (5/08, Sample 6)
Red/Silver Hybrid: 2 new (10/08, Samples 15 and 16) Additionally two used cams (a Red Black Diamond Pre-C4 Camalot and a used Blue Metolius TCU, Samples 10 and 11) were donated by bystanders looking to have some control samples thrown into the mix. Both were in good, but well used condition and came straight off their owners’ racks. Since I would rather not draw Black Diamond or Metolius into this mess I will not be providing details about them other than to say that both of these cams failed well above their ratings, and in the case of the Camalot was still somewhat operable after the sling broke during its first test (we then tied a new sling to it and tested it again as Sample 13, but the puller ran out of stroke before it broke a second time). As for the Aliens, only 5 of the 13 new ones met their rated strength, with the percentage of the rating held ranging from 63.3% to 116.7% and an overall average of 94.3%. Of the 9 used Aliens, only 2 met their rated strength, with the percentage of the rating held ranging from 54.7% to 105.0% and an overall average of 81.9%. Unfortunately there is no single issue that was the primary cause of failure for all of the cams, but rather there were a number of issues that appear to have played a part on some or all of the cams. These issues include: braze failure, swage failure, head failure, lobe deformation, axle deformation and incorrectly centered axle holes that reduce the outward force available to keep the cam in the fixture during testing. Some quick thoughts on Stem Construction Before we get to the specific issues discovered in the testing, it’s important to spend some time discussing the wire rope cable used to make Alien stems. CCH’s website lists the stem cables as being either 7x7 or 7x19 construction and either 5/32” or 3/16” diameter, depending on which size cam and whether it’s a Regular, Super Long or Hybrid. No mention is made of whether the wire rope is Stainless or Galvanized. Wire rope is typically rated with the following breaking strengths: 5/32” 7x7: 2600# (Galvanized), 2400# (Stainless)
5/32” 7x19: 2800# (Galvanized), 2400# (Stainless)
3/16” 7x7: 3700# (Galvanized), 3700# (Stainless)
3/16” 7x19: 4200# (Galvanized), 3700# (Stainless) The important thing to keep in mind is that these breaking strengths are just that: breaking strengths. They are the loads at which the wire rope will be expected to break and does not include any sort of safety factor or padding. Since the breaking strengths of these sizes/types of wire rope are usually only slightly higher than the rated breaking strengths of Aliens it should be obvious that close to 100% efficiency on the brazed or swaged joints are necessary for the stems to meet their ratings. On a related note, I find it rather strange that the ratings for some Aliens are actually higher than the typical rating given to the wire rope used to build their stems. According to the CCH website a Gold Regular Alien uses 5/32” 7x19 cable and is rated to 3300#, yet that size cable is normally only rated to 2800#. Similarly Yellow through Red Super Longs use 5/32” 7x7 cable and are rated to 2700#, yet that cable is typically rated to 2600#. Obviously there is something goofy going on here and it is something I’d very much like to see an explanation from CCH about. Description of the Test Equipment and Process The quick version is that my tensile tester is a converted shop press with a hydraulic ram/power unit connected to a 10,000 pound S-beam load cell. The load cell is connected to a Daytronic 4077 strain gage indicator which feeds a National Instruments 6008 DAQ module which allows me to log all the data using NI’s Signal Express software. The Daytronic has a scan rate of 1000 samples/sec and is set to monitor the analog version of the signal from the load cell, which does away with a lot of the problems with ensuring measurement of the true peak when doing digital scans. The output from the Daytronic is an analog signal sent at 1000 samples/sec and well within the 250,000 samples/sec scan rate of the NI DAQ. The strain gage indicator was programmed using the mV/V rating given on the certificate of calibration that came with the load cell and all 5 sets of load cell/strain gage indicators I have agree within a fraction of a percent. Though I believe the equipment to be correct I have not had it certified by a third party lab. When performing the tests I set the width of the fixture such that the cam lobes were roughly 50% expanded (the tips of the opposing lobes touching). I then connected a carabiner to both the thumb loop and hydraulic ram, reset the tare weight and max load on the strain gage indicator, started the data logging software and then pulled until something failed. The speed of the ram was fairly slow, but I did not measure it and it may be off from the speed called out in the CE/UIAA cert (20-50 mm/min if there are no textile load bearing elements, 50-200 mm/min if there are). After testing the cams in the fixture any that still had intact stems were then disassembled and the stem tested separately with a pin through the axle hole in the head (supported on either side of the head by steel blocks) to get a failure force for the stem itself. If I were to pick one area of concern with my testing, it would be the crack fixture. While the faces on it are not at the maximum roughness spec called out in the CE12276/UIAA125 cert, I believe it to be adequate judging by the fact that some of the Aliens and all of the cams from other manufacturers I’ve tested with it held just fine. The cert states that a maximum roughness of 500µm is allowable, but that any roughness below that which will allow the cams to hold is acceptable. And finally, on to the actual problems found during the testing… Braze Failure As we probably all know, problems with brazes in the head/stem connection were the source of the problem that initiated CCH’s recall of Aliens a couple years ago. While there was only one failure in this testing that was a direct result of brazing issues (Sample 3), there were many other samples that showed issues with porosity and contamination within the braze upon cross sectioning of their heads. In a nutshell, brazing is a process by which two materials are joined together by heating them to somewhere below either of their melting points and then introducing a third material that is soluble in both of them. It’s quite similar to soldering (as done on electrical equipment or copper pipes), but is done at a much higher temperature and with a much stronger filler material. To do a properly executed brazed joint you first apply flux to the parts to be joined, begin heating the parts (which melts the flux and allows it to clean the surfaces of any contaminants) and then apply the brazing material to the joint. While feeding the brazing material into the joint it will melt and flow into the joint, pulled by capillary action, and join both the head and all of the strands of the cable together as a single unit. In cases where the joint is closed (like on the head of a cam) a weep hole is typically included at the bottom of the joint to allow the excess flux to run out (carrying with it any contaminants) and make room for the braze material. Additionally the weep hole acts as a visual confirmation that the joint has been fully filled, as it will not close up until after the joint itself has filled completely. Without a weep hole it is entirely possible to have a finished joint that looks perfect upon examination but is completely devoid of braze material, as happened with Sample 3. Current generations of Aliens do not include a weep hole, and the pictures of the cross sections of the heads show the impact leaving it out has on the brazed joints. Some are good, but others have issues with porosity and contamination. The three units from the mid-1990’s actually do have a weep hole (Samples 22, 23 and 24) and those brazes look a good bit better. I can’t say why or when CCH stopped using one, but they obviously did. Anyway, the problem with under-filled or contaminated joints should be obvious… the strength of the joint rests entirely on the quality of the connection between the brazing material and the materials being joined. If there is insufficient braze material there (under-filled) or the joint contaminated (as evidenced by porosity in the joint) then not all of the strands of the cable will share in bearing the load and failure somewhere below what would otherwise be expected will occur. And given that the strength ratings of Aliens frequently require almost 100% of the strength of the wire rope (if not more…) it should be quite clear that joints that are contaminated or not fully filled are probably not a good thing. On a related note, very close attention must be paid when brazing wire rope as is done on Aliens. It is very easy to overheat the wires and cause them to loose a good deal of their strength. While this was not an issue with any of the test samples it was the likely cause of failure in a Red I broke a year or so ago which had the stem snap at the base of the head at ~93% or rating. The stem on Sample 18 may have failed for this reason, but it occurred slightly above its rating. Incorrectly Centered Axle Holes Shortly after publishing the results from my testing at the NRR I received an email from John Fields (the inventor of the Supercam) which suggested that some of the slippage and abrasion issues may have been due to incorrect cam angles due to improperly centered axle holes in the lobes. This issue came up a couple years ago and when several Aliens with greatly reduced range were found in circulation, which prompted John to write some software that would allow him to test his cams to see if they axles on them were properly centered on the center point of the spiral. It’s a neat piece of software and is available online at www.dorringtonclimbing.com. Anyway, the issue here is that all sorts of screwy things happen to the effective cam angle if the axle is not centered on the center point of the logarithmic spiral that defines the bearing surface of the cam lobe. The nature of the effect depends on the relative direction of the divergence of the center points, but in every case it results in effective cam angles that increase or decrease significantly (and sometimes both) as the lobe travels through its rotation. The magnitude of the effect is largely dependent on the distance between the center points, but is also somewhat dependent on the direction. There doesn’t seem to be much rhyme or reason to the direction or distance of the discrepancies found in the cam lobes from the test samples, but on the handful I tested all four lobes from both the distance and direction was the same on all of them. The effective cam angles found on these samples ranged from 7 degrees all the way up to 28 degrees. The nominal cam angle on Aliens is 16 degrees, which gives a holding power (ratio of outward force on the crack to downward force on the cam) of 1.74:1. At 7 degrees the holding power jumps up to 4.07:1, which could easily be more force than the components of the cam or the rock in the placement can handle. On the other end, an effective cam angle of 28 degrees has a holding power of only 0.94:1 and there simply won't be enough force available for the friction between the aluminum and rock to hold the cam in place for the types of rock normally climbed. If you’re interested, Viano Kodas has an excellent explanation of the physics behind it on his site here: Link Head Failure This was by far the most surprising failure mode found in the testing and only occurred on the two Black Aliens that were tested (Samples 7 and 24). Quite simply the top of the head above the axle hole came off when the stem was tested separately from the rest of the cam. One was brand new (4/08) and had the top of the head come off at 80% of the cam’s rating (1493# / 6.64kN, rated to 1860# / 8.27kN) and the other was used (mid-1990’s) and had it happen at 146% of the cam’s rating (2724# / 12.12kN). Both of these cams pulled out of the fixture during the initial tests well below their ratings, at 64% rating for the new one and 55% rating for the used one. Had it not slipped from the fixture so far below rating it’s likely that the new one would have had the head fail during the initial test. One item of note is that CCH states on their website that since 2006 all of their stems from Black through Red are proof tested to 1750# prior to assembly into a cam (Gold through Clear get pulled to 2400#). This new Black was marked as Tensile Tested, yet failed at a load considerably lower than what was applied during this proof test. I personally don’t know what to make of this, but find it somewhat disturbing. Lobe Deformation Nearly all of the test samples experienced deformation of their lobes to some degree, with the most common modes being flat spots either pressed or abraded into the lobes. The degree of deformation varied wildly, with some being very minor and others being quite pronounced. Several of the lobes also buckled considerably, with one or more lobes being bent significantly away from perpendicular to the axle. The main concern with this deformation is that any change in the geometry of the cam lobe will have a direct effect on the holding power of the unit because it changes the angle at which the force is transferred from the axle to the sides of the crack. In the case of flat spots the effective cam angle between the center of the axle and the leading edge of the flat spot (where the majority of the force will be concentrated as the lobe tries to rotate) increases considerably from the original cam angle prior to deformation. In the case of buckled lobes the concern is that once they begin to buckle the forces are no longer being applied in the plane in which the lobe is strongest, which means that the strength is greatly reduced. I do not have an explanation for why some lobes experienced more deformation and abrasion than others, but suspect it is due to differences in hardness and strength of the material used to make the lobes. In general harder = stronger and the hardness of the lobes from the test samples varied wildly. CCH claims to use 6061T6 aluminum extrusions for their lobes, which should have a hardness of ~55-60 on the Rockwell B scale. The hardness of the lobes from the samples ranged from HRB1 all the way to HRB73, with clusters around HRB40, HRB46 and HRB 54. While the hardness of the samples will not tell us what material and temper they are it will tell us what they are not, which is 6061T6 in the case of the ones that vary significantly from the HRB55-60 hardness found for that material and temper. To determine the exact material and condition a full metallurgical analysis would be necessary and is beyond the scope of this testing since it doesn’t really matter what the lobes are made of so long as they allow the cam to hold its rated strength. Axle Deformation Like with the lobes, many of the axles from the Aliens experienced some degree of deformation, with some remaining dead straight while others became decidedly C-shaped. I suspect that the deformation was caused by either inconsistencies in the hardening of the axles or differences in cam lobe geometry that resulted in greater than usual forces applied to the axle. The biggest issue with axle deformation is that it results in the cam lobes being loaded sideways, which is not the direction in which they are strongest and will quickly lead to buckled lobes. Note: Unfortunately I was unable to perform hardness testing on the axles to because the V-anvil on my tester is located slightly off center, which causes the penetrator to skip off the axle as the main load was applied. I’d be quite interested in this data though and would be quite happy to send the axles along to anyone who has the capability to test them. Swage Failure This section could quite easily be left out, as every single cam tested had the swage either hold over the cam’s rated strength or hold a force that caused a failure at the head/stem joint. I’m choosing to include it though because of the number of stems that only met their rating by a very small amount. Of these stems, 8 were ones that were subject to the issue mentioned above where the cam was rated to 2700# and the wire used to make the stem typically rated to only 2600# or 2400#, depending on whether it was galvanized or stainless. A properly completed oval swage joint should be good for 100% of the strength of the wire rope, but certainly can’t add strength to it. The two most common errors in swaging are too little pressure and too much pressure. With too little pressure applied to the swaging die, the fitting will not hold the wire rope tight enough and the end can slide out. Too much pressure and the wire rope can be damaged and will snap at the swage at a force somewhere under the rating of the cable. I can’t say for certain whether the swages on these 8 were done correctly or not; only that they failed above the typical rating for the cable they were done on and all 8 failed at the top of the swage at a hair above the rating of the cam (within 75 pounds of the rating for 6 of them). Summary In summary, there were quite a few issues uncovered in the testing and all of the data and photos are included below so people can make their own informed decisions regarding their gear and safety. As I’ve said in the threads that preceded this, I have no particular agenda against CCH. My only concern is that there appears to be a high probability that there is faulty gear out in circulation and people should be aware of this and take whatever precautions they deem necessary to ensure their safety. In fact, CCH was informed of the results of my testing prior to making the results public, both this time and with the testing done at the NRR. I would have much preferred if they had been proactive about this like the other gear companies are when issues are found with their gear, but unfortunately CCH chose to ignore it instead. BTW, if you volunteered to contribute funds to cover the costs of the test samples and have not yet sent them I'd appreciate it if you would kindly do so. I'm close to having the costs of the testing covered, but not quite there yet. Thanks. |
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notapplicable
Aug 15, 2010, 6:26 AM
Post #168 of 190
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adatesman wrote: Sample 1: Grey Alien Condition: Used Date Stamp: 0605 "Tensile Tested" Stamp: No Strength Rating: 2700# / 12.01kN Failed at: 2381# / 10.59kN Percent of Rating Held: 88.2% Failure Mode: Pulled from fixture with large flat spots, buckled cam lobes and slightly bent axle. Much material abraded from the lobes. Notes: Larger than normal cable used for the stem, according to what's listed on CCH's website. Should be 5/32" 7x7 cable, not 3/16" 7x7. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample01/sample01.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample01/sample01-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample01/sample1-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample01/sample01_broken_back.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample01/sample01_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample01/sample01_axle.JPG[/image] Stem Construction: 3/16" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 3700# / 16.46kN Stainless: 3700# / 16.46kN Failure load of Stem Test: 3417# / 15.20kN Stem Failure Mode: Cable separated at base of head. Average Lobe Hardness: (converted from HRE scale due to them being too soft to test HRB. Lobe 4 was too mangled to test) Lobe 1: HRB1 Lobe 2: HRB12 Lobe 3: HRB5 Lobe 4: - Effective Cam Angle at Various Positions: Red: 16 + 6.5 = 22.5 Degrees Yellow: 16 + 0 = 16 Degrees Blue: 16 – 3.5 = 12.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample01/sample1-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:26 AM
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adatesman wrote: Sample 2: Orange Alien Condition: Used Date Stamp: none "Tensile Tested" Stamp: No Strength Rating: 3500# / 15.57kN Failed at: 2562# / 11.40kN Percent of Rating Held: 73.2% Failure Mode: Sling broke, cam looked in reasonable condition afterward so tested again clipped directly to the thumb loop. Failed at: 2502# / 11.13kN Percent of Rating Held: 71.5% Failure Mode: Pulled from fixture with bent axle, some flat spots and abrasion on lobes. Notes: [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample02.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample2a-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample2b-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample02-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample02_broken_front.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample02_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample02_axle.JPG[/image] Stem Construction: 3/16" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 3700# / 16.46kN Stainless: 3700# / 16.46kN Failure load of Stem Test: 4104# / 18.26kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: Lobe 1: HRB71 Lobe 2: HRB65 Lobe 3: HRB73 Lobe 4: HRB71 Effective Cam Angle at Various Positions: Red: 16 + 6.5 = 22.5 Degrees Yellow: 16 + 2.5 = 18.5 Degrees Blue: 16 – 0.5 = 15.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample02/sample2-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:27 AM
Post #170 of 190
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adatesman wrote: Sample 3: Yellow Alien Condition: Used Date Stamp: 1003 "Tensile Tested" Stamp: No Strength Rating: 2700# / 12.01kN Failed at: 2099# / 9.34kN Percent of Rating Held: 77.7% Failure Mode: Cable pulled from head with no braze on inner bundle of wire. Notes: Braze looked perfect prior to test, axle and lobes remain in good condition after test. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample03/sample03.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample03/sample3-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample03/sample03-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample03/sample03_broken_left.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample03/sample03_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample03/sample03_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: N/A Location of Stem Failure: N/A Average Lobe Hardness: Lobe 1: HRB41 Lobe 2: HRB36 Lobe 3: HRB42 Lobe 4: HRB50 Effective Cam Angle at Various Positions: Red: 16 + 4.0 = 20 Degrees Yellow: 16 – 2.0 = 14 Degrees Blue: 16 – 4.0 = 12 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample03/sample3-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:27 AM
Post #171 of 190
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adatesman wrote: Sample 4: Purple Alien Condition: New Date Stamp: 1108 "Tensile Tested" Stamp: Yes Strength Rating: 3500# / 15.57kN Failed at: 2829# / 12.58kN Percent of Rating Held: 80.8% Failure Mode: Pulled from fixture with bent axle and relatively minor flat spots/abrasion of lobes. Notes: "W" stamped on head. Don't have pic of cam in fixture. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample04/sample04.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample04/sample4-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample04/sample04_broken_braze1.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample04/sample04_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample04/sample04_axle.JPG[/image] Stem Construction: 3/16" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 3700# / 16.46kN Stainless: 3700# / 16.46kN Failure load of Stem Test: 4194# / 18.66kN Location of Stem Failure: Middle of cable between swage and head. Average Lobe Hardness: Lobe 1: HRB53 Lobe 2: HRB52 Lobe 3: HRB49 Lobe 4: HRB51 Effective Cam Angle at Various Positions: Red: 16 + 12.0 = 28 Degrees Yellow: 16 + 3.0 = 19 Degrees Blue: 16 – 2.5 = 13.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample04/sample4-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:27 AM
Post #172 of 190
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adatesman wrote: Sample 5: Purple Alien Condition: New Date Stamp: 1108 "Tensile Tested" Stamp: Yes Strength Rating: 3500# / 15.57kN Failed at: 3113# / 13.85kN Percent of Rating Held: 88.9% Failure Mode: Pulled from fixture with bent axle and relatively minor flat spots/abrasion on lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample05/sample05.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample05/sample5-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample05/sample05-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample05/sample05_broken_top2.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample05/sample05_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample05/sample05_axle.JPG[/image] Stem Construction: 3/16" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 3700# / 16.46kN Stainless: 3700# / 16.46kN Failure load of Stem Test: 3948# / 17.56kN Location of Stem Failure: End of cable pulled from swage. Average Lobe Hardness: Lobe 1: HRB54 Lobe 2: HRB54 Lobe 3: HRB51 Lobe 4: HRB55 Effective Cam Angle at Various Positions: Red: 16 + 12.0 = 28 Degrees Yellow: 16 + 3.0 = 19 Degrees Blue: 16 – 2.5 = 13.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample05/sample5-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:28 AM
Post #173 of 190
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adatesman wrote: Sample 6: Clear Alien Condition: New Date Stamp: 508 "Tensile Tested" Stamp: Yes Strength Rating: 3500# / 15.57kN Failed at: 3159# / 14.05kN Percent of Rating Held: 90.3% Failure Mode: Pulled from fixture with bent axle, buckled lobes and relatively minor flat spots/abrasion on lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample06/sample06.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample06/sample6-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample06/sample06-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample06/sample06_broken_top.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample06/sample06_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample06/sample06_axle.JPG[/image] Stem Construction: 3/16" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 3700# / 16.46kN Stainless: 3700# / 16.46kN Failure load of Stem Test: 3921# / 17.56kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: Lobe 1: HRB55 Lobe 2: HRB53 Lobe 3: HRB52 Lobe 4: HRB23 (not a typo) Effective Cam Angle at Various Positions: Red: 16 + 7.0 = 23 Degrees Yellow: 16 – 5.0 = 11 Degrees Blue: 16 – 9.0 = 7 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample06/sample06-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:28 AM
Post #174 of 190
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adatesman wrote: Sample 7: Black Alien Condition: New Date Stamp: 408 "Tensile Tested" Stamp: Yes Strength Rating: 1860# / 8.27kN Failed at: 1183# / 5.26kN Percent of Rating Held: 63.6% Failure Mode: Pulled from fixture with major flat spots and abrasion of lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample07.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample7-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample07-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample07_broken_right.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample07_head1.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample07_head2.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample07_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 1493# / 6.64kN Location of Stem Failure: Top of head above axle broke off. Average Lobe Hardness: (only room for 1 test on each lobe, test on Lobe 1 was too close the edge for reliable reading) Lobe 1: - Lobe 2: HRB49 Lobe 3: HRB45 Lobe 4: HRB42 Effective Cam Angle at Various Positions: Red: 16 – 3.5 = 12.5 Degrees Yellow: 16 + 7.5 = 23.5 Degrees Blue: 16 + 8.0 = 24 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample07/sample07-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:28 AM
Post #175 of 190
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adatesman wrote: Sample 8: Yellow Alien Condition: New Date Stamp: 509 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 2493# / 11.09kN Percent of Rating Held: 92.3% Failure Mode: Pulled from fixture with major flat spots and abrasion on lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample08/sample08.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample08/sample8-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample08/sample08-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample08/sample08_broken_left.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample08/sample08_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample08/sample08_axle.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2795# / 12.43kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: Lobe 1: HRB55 Lobe 2: HRB53 Lobe 3: HRB48 Lobe 4: HRB54 Effective Cam Angle at Various Positions: Red: 16 + 3.0 = 19 Degrees Yellow: 16 + 2.0 = 18 Degrees Blue: 16 + 0 = 16 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample08/sample08-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:29 AM
Post #176 of 190
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adatesman wrote: Sample 9: Yellow Alien Condition: New Date Stamp: 509 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 2538# / 11.29kN Percent of Rating Held: 94.0% Failure Mode: Pulled from fixture with major flat spots and abrasion on lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample9-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09_broken_left.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09_axle.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2705# / 12.03kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: Lobe 1: HRB55 Lobe 2: HRB57 Lobe 3: HRB57 Lobe 4: HRB54 Effective Cam Angle at Various Positions: Red: 16 + 1.0 = 17 Degrees Yellow: 16 + 0.5 = 16.5 Degrees Blue: 16 – 0.5 = 15.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample09/sample09-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:29 AM
Post #177 of 190
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adatesman wrote: Sample 12: Red Alien Condition: New Date Stamp: 509 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 2723# / 12.11kN Percent of Rating Held: 100.9% Failure Mode: Cable separated at top of swage. Notes: Relatively minor flat spots on lobes. "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample12/sample12.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample12/sample12-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample12/sample12-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample12/sample12_broken.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample12/sample12_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample12/sample12_axle.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: N/A Location of Stem Failure: N/A Average Lobe Hardness: Lobe 1: HRB38 Lobe 2: HRB37 Lobe 3: HRB48 Lobe 4: HRB37 Effective Cam Angle at Various Positions: Red: 16 + 8.0 = 24 Degrees Yellow: 16 + 2.5 = 18.5 Degrees Blue: 16 – 1.0 = 15 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample12/sample12-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:30 AM
Post #178 of 190
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adatesman wrote: Sample 14: Red Alien Condition: New Date Stamp: 509 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 2728# / 12.13kN Percent of Rating Held: 101.0% Failure Mode: Cable separated at top of swage. Notes: Relatively minor flat spots on lobes. "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample14/sample14.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample14/sample14-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample14/sample14-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample14/sample14_broken.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample14/sample14_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample14/sample14_axle.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: N/A Location of Stem Failure: N/A Average Lobe Hardness: Lobe 1: HRB45 Lobe 2: HRB39 Lobe 3: HRB43 Lobe 4: HRB49 Effective Cam Angle at Various Positions: Red: 16 + 2.5 = 18.5 Degrees Yellow: 16 + 0.5 = 16.5 Degrees Blue: 16 – 1.0 = 15 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample14/sample14-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:30 AM
Post #179 of 190
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adatesman wrote: Sample 15: Red/Silver Hybrid Alien Condition: New Date Stamp: 1008 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 3042# / 13.54kN Percent of Rating Held: 112.7% Failure Mode: Pulled from fixture with bent axle, umbrella'd small lobes, relatively major flat spots/abrasion on lobes and some lobe buckling. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15a.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15b.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15a-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15b-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15_broken_left.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15_broken_right.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2948# / 13.11kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: (Lobes 1&2 small, Lobes 3&4 large) Lobe 1: HRB48 Lobe 2: HRB48 Lobe 3: HRB55 Lobe 4: HRB55 Effective Cam Angle at Various Positions, Side 1: Red: 16 + 7.0 = 23 Degrees Yellow: 16 + 0.5 = 16.5 Degrees Blue: 16 – 2.5 = 13.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15a-error-angles.JPG[/image] Effective Cam Angle at Various Positions, Side 2: Red: 16 + 8.5 = 24.5 Degrees Yellow: 16 + 3.5 = 19.5 Degrees Blue: 16 + 0 = 16 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample15/sample15b-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:31 AM
Post #180 of 190
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adatesman wrote: Sample 16: Red/Silver Hybrid Alien Condition: New Date Stamp: 1008 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 3150# / 14.01kN Percent of Rating Held: 116.7kN Failure Mode: Outer bundles of cable separated at top of swage, but inner bundle appears to have separated at base of head. Notes: Slightly bent axle and relatively major flat spots on lobes (no abrasion). "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16a.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16b.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16a-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16b-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16_broken.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16_broken_side.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: N/A Location of Stem Failure: N/A Average Lobe Hardness: Lobe 1: HRB54 Lobe 2: HRB50 Lobe 3: HRB49 Lobe 4: HRB42 Effective Cam Angle at Various Positions, Side 1: Red: 16 + 6.5 = 22.5 Degrees Yellow: 16 + 4.0 = 20 Degrees Blue: 16 + 0 = 16 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16a-error-angles.JPG[/image] Effective Cam Angle at Various Positions, Side 2: Red: 16 + 8.5 = 24.5 Degrees Yellow: 16 + 4.0 = 20 Degrees Blue: 16 + 0.5 = 16.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample16/sample16b-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:31 AM
Post #181 of 190
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adatesman wrote: Sample 17: Grey Alien Condition: New Date Stamp: 409 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 2645# / 11.77kN Percent of Rating Held: 98.0% Failure Mode: Pulled from fixture with very slightly bent axle and flat spots/abrasion on lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample17/sample17.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample17/sample17-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample17/sample17-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample17/sample17_broken_top.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample17/sample17_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample17/sample17_axle.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2942# / 13.09kN Location of Stem Failure: 6 bundles separated at swage, 1 bundle separated 1" down from head. Average Lobe Hardness: Lobe 1: HRB41 Lobe 2: HRB45 Lobe 3: HRB46 Lobe 4: HRB49 Effective Cam Angle at Various Positions: Red: 16 + 4.5 = 20.5 Degrees Yellow: 16 + 4.0 = 20 Degrees Blue: 16 + 1.0 = 17 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample17/sample17-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:32 AM
Post #182 of 190
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adatesman wrote: Sample 18: Grey Alien Condition: Used Date Stamp: 1204 "Tensile Tested" Stamp: No Strength Rating: 2700# / 12.01kN Failed at: 2715# / 12.08kN Percent of Rating Held: 100.6% Failure Mode: Cable separated at base of head. Notes: Braze looked good, slight discoloration of wire indicating possible overheating of joint. Orange circular sticker on bottom of trigger bar with "4" written on it. Unit was not disassembled or cross sectioned because owner wants it back intact. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample18/sample18.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample18/sample18-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample18/sample18-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample18/sample18_broken1.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample18/sample18_broken_head3.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: N/A Location of Stem Failure: N/A Average Lobe Hardness: Lobe 1: Not measured Lobe 2: Not measured Lobe 3: Not measured Lobe 4: Not measured Effective Cam Angle at Various Positions: Red: 16 + 2.0 = 18 Degrees Yellow: 16 + 2.5 = 18.5 Degrees Blue: 16 + 0 = 16 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample18/sample18-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:32 AM
Post #183 of 190
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adatesman wrote: Sample 19: Grey Alien Condition: New Date Stamp: 409 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 2831# / 12.59kN Percent of Rating Held: 104.9% Failure Mode: Pulled from fixture with very slightly bent axle and flat spots/abrasion on lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample19/sample19.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample19/sample19-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample19/sample19-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample19/sample19_broken_top.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample19/sample19_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample19/sample19_axle.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2930# / 13.03kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: Lobe 1: HRB47 Lobe 2: HRB45 Lobe 3: HRB47 Lobe 4: HRB41 Effective Cam Angle at Various Positions: Red: 16 + 5.5 = 21.5 Degrees Yellow: 16 + 5.5 = 21.5 Degrees Blue: 16 + 2.5 = 18.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample19/sample19-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:32 AM
Post #184 of 190
(4698 views)
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Posts: 17771
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adatesman wrote: Sample 20: Yellow Alien Condition: New Date Stamp: 509 "Tensile Tested" Stamp: Yes Strength Rating: 2700# / 12.01kN Failed at: 2227# / 9.91kN Percent of Rating Held: 82.5% Failure Mode: Pulled from fixture with flat spots/abrasion on lobes. Notes: "W" stamped on head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample20/sample20.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample20/sample20-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample20/sample20-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample20/sample20_broken_left.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample20/sample20_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample20/sample20_axle.JPG[/image] Stem Construction: 5/32" 7x7 Typical Strength Rating for that type of Cable: Galvanized: 2600# / 11.57kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2761# / 12.28kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: Lobe 1: HRB55 Lobe 2: HRB53 Lobe 3: HRB54 Lobe 4: HRB54 Effective Cam Angle at Various Positions: Red: 16 + 4.0 = 20 Degrees Yellow: 16 + 4.0 = 20 Degrees Blue: 16 + 2.0 = 18 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample20/sample20-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:33 AM
Post #185 of 190
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Registered: Aug 31, 2006
Posts: 17771
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adatesman wrote: Sample 21: Yellow Alien Condition: Used Date Stamp: 599 "Tensile Tested" Stamp: No Strength Rating: 2700# / 12.01kN Failed at: 2836# / 12.62kN Percent of Rating Held: 105.0% Failure Mode: Pulled from fixture with flat spots/abrasion on lobes. Notes: Braze looks horribly underfilled. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21_braze5.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21_broken_right.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2775# / 12.34kN Location of Stem Failure: Cable separated at swage. Average Lobe Hardness: Lobe 1: HRB62 Lobe 2: HRB63 Lobe 3: HRB59 Lobe 4: HRB62 Effective Cam Angle at Various Positions: Red: 16 + 4.0 = 20 Degrees Yellow: 16 + 2.5 = 18.5 Degrees Blue: 16 + 1 = 17 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample21/sample21-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:33 AM
Post #186 of 190
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Registered: Aug 31, 2006
Posts: 17771
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adatesman wrote: Sample 22: Blue Alien Condition: Used Date Stamp: None "Tensile Tested" Stamp: No Strength Rating: 2200# / 9.79kN Failed at: 1828# / 8.13kN Percent of Rating Held: 83.1% Failure Mode: Pulled from fixture with bent axle and flat spots/abrasion on lobes. Notes: Nuts on both ends of axle and weep hole in head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample22/sample22.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample22/sample22-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample22/sample22-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample22/sample22_broken_back.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample22/sample22_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample22/sample22_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 3139# / 13.96kN Location of Stem Failure: 6 bundles of cable separated at swage, 1 bundle separated at head. Average Lobe Hardness: (Lobes too mangled to get any measurements) Lobe 1: - Lobe 2: - Lobe 3: - Lobe 4: - Effective Cam Angle at Various Positions: Red: 16 + 5.0 = 21 Degrees Yellow: 16 + 6.5 = 22.5 Degrees Blue: 16 + 8.5 = 24.5 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample22/sample22-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:33 AM
Post #187 of 190
(4692 views)
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Registered: Aug 31, 2006
Posts: 17771
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adatesman wrote: Sample 23: Blue Alien Condition: Used Date Stamp: None "Tensile Tested" Stamp: No Strength Rating: 2200# / 9.79kN Failed at: 1535# / 6.83kN Percent of Rating Held: 69.8% Failure Mode: Pulled from fixture with bent axle and flat spots/abrasion on lobes. Notes: Plastic lower trigger bar, nuts on both ends of axle and weep hole in head. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample23/sample23.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample23/sample23-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample23/sample23-fixture.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample23/sample23_broken_left.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample23/sample23_head.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample23/sample23_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 3092# / 13.75kN Location of Stem Failure: Cable separated at base of head. Average Lobe Hardness: (Only room for 1 test on each lobe) Lobe 1: HRB49 Lobe 2: HRB42 Lobe 3: HRB40 Lobe 4: HRB45 Effective Cam Angle at Various Positions: Red: 16 – 5.0 = 11 Degrees Yellow: 16 + 0 = 16 Degrees Blue: 16 + 2.0 = 18 Degrees [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample23/sample23-error-angles.JPG[/image] |
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notapplicable
Aug 15, 2010, 6:34 AM
Post #188 of 190
(4690 views)
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Registered: Aug 31, 2006
Posts: 17771
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adatesman wrote: Sample 24: Black Alien Condition: Used Date Stamp: None "Tensile Tested" Stamp: No Strength Rating: 1860# / 8.27kN Failed at: 1017# / 4.52kN Percent of Rating Held: 54.7% Failure Mode: Pulled from fixture with flat spots/abrasion on lobes. Notes: Nuts on both ends of axle and weep hole in head. Unfortunately I don't have photos of it in the prior to testing and in the fixture, which means I also don't have a photo to calculate the effective angles. [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample24/sample24-chart.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample24/sample24_broken_left.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample24/sample24_head1.JPG[/image] [image]www.shariconglobal.com/misc/pulltesting/RSaliens/Sample24/sample24_axle.JPG[/image] Stem Construction: 5/32" 7x19 Typical Strength Rating for that type of Cable: Galvanized: 2800# / 12.46kN Stainless: 2400# / 10.68kN Failure load of Stem Test: 2724# / 12.12kN Location of Stem Failure: Top of head above axle broke off. Average Lobe Hardness: (Only room for 1 test on each lobe, test failed on Lobe 3) Lobe 1: HRB40 Lobe 2: HRB44 Lobe 3: - Lobe 4: HRB56 Effective Cam Angle at Various Positions: Red: Not measured Yellow: Not measured Blue: Not measured |
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patto
Aug 15, 2010, 8:23 AM
Post #189 of 190
(4672 views)
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Registered: Nov 15, 2005
Posts: 1453
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Quite bizarre this activity. I hope it isn't an attempt to achive by quoting. The only reason I can see for this is some sort of civil law suit. 
Absolutely bizarre. I hope the mods get on top of this.
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kobaz
Aug 15, 2010, 4:04 PM
Post #190 of 190
(4587 views)
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Registered: Sep 19, 2004
Posts: 726
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I don't see anything wrong with restoring the deleted information. Preservation is good.
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FrictionModel.gif
