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Partner angry


Nov 19, 2008, 3:05 PM
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Re: [adatesman] Hardness testing of cam lobes
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I have several knives whose rockwell hardness is in the 50's to very high 90's (ceramic). So I'm assuming this B scale is different entirely than the rockwell scale used to test a blade's hardness.

Google will tell me!!


Partner angry


Nov 19, 2008, 3:08 PM
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Yep, different scales.


adatesman


Nov 19, 2008, 3:11 PM
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Nov 19, 2008, 3:16 PM
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They all seem consistent within the brand.

I remember when I started that the Chouinard Camalots were reported to have softer inner lobes than outer lobes. I wonder if this is true or just a rumor.

Looking at the hardnesses, I can't say that I'd ever use a rock empire unless I could place it in a constriction.


sgreer


Nov 19, 2008, 3:19 PM
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Damn, how hard is to hard?

The harder the material the more brittle the material. I've heard stories of "off brand" lobes shearing after a big fall.

BD IS the most accepted cam so I will stick with those numbers as being a good baseline for an ideal hardness.

This is really interesting. I will do some research of my own. Good work.


adatesman


Nov 19, 2008, 3:23 PM
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hafilax


Nov 19, 2008, 3:26 PM
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I don't really know much about material science so maybe someone can answer some questions for me. I'll do a quick search to see if I can find something. What I would like to understand is: What are the compromises driving the use of different alloys?

Does using a softer alloy result in higher friction so you can get away with a smaller camming angle to yield a larger device range?

Does Metolius go with the harder alloy because of the larger forces due to the smaller camming angle?

Do Aliens get deformations like flat spots more easily?

Can deformations cause a piece to pull?

Aliens don't seem to use the standard alloy. What other properties does their alloy have?


Partner angry


Nov 19, 2008, 3:27 PM
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I understand that.

I'm reading it as a Metolii or RE is more likely to blow out the rock.

Would that be an incorrect interpretation?


adatesman


Nov 19, 2008, 3:36 PM
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atlnq9


Nov 19, 2008, 7:39 PM
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Ok, I am the guy who did the hardness testing
adatesman wrote:
Another data point to add will be coming in another write up in the next couple days, where I pulled the Green Metolius (minus the ends of the two outer lobes) and a pair of old U-stem Camalots to failure. The Metolius, with its harder lobes, failed when the lobe shattered.
Oh, and due to a Post Office screwup I ended up sending 2 of each of the samples, which each were tested in several places (I didn't sent 10 of each cam lobe....).

-a.

Is this the same green one I tested? I will be very interested in seeing some photos of the fractured pieces. I will have to think on the slip directions when in compression but I am thinking about 45 degree surfaces...

Also just thought I would note this for you guys, Metolius is 7075 up to the # 6, the 7 and 8 are 6061.

As soon as I can I will get pics.

I'll try to keep up on here, to answer the metallurgy questions.

sometime after Thanksgiving I will be finishing up looking at the alien, I haven't decided my exact plan of action yet, micrograph to start, from that I should be able to tell if they solution treat properly, after that it will either be that they over or under age the samples, SEM or additional aging to see where they are at on the curve...

College is pretty overwhelming right now so pardon my response time and the time to finish the analysis.


atlnq9


Nov 19, 2008, 7:43 PM
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Re: [angry] Hardness testing of cam lobes [In reply to]
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angry wrote:
I understand that.

I'm reading it as a Metolii or RE is more likely to blow out the rock.

Would that be an incorrect interpretation?

no, the bearing stress exerted to the rock would not be related to the lobe hardness, but related only to contact area. sorry to step in here aric


(This post was edited by atlnq9 on Nov 19, 2008, 8:12 PM)


atlnq9


Nov 19, 2008, 7:59 PM
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angry wrote:
when I started that the Chouinard Camalots were reported to have softer inner lobes than outer lobes. I wonder if this is true or just a rumor.

they are the same

sgreer wrote:
Damn, how hard is to hard?

The harder the material the more brittle the material.

not always true across different alloys, but a good general rule within one alloy; however, there are exceptions to that too.

hafilax wrote:
Aliens don't seem to use the standard alloy. What other properties does their alloy have?

They are using a fine alloy, just they don't know how to heat treat. They are claiming the T6 aged condition but their material is not actually hardened to what they claim. The alloy is softer (why you get premature cam lobe wear), it will have a low ultimate tensile strength, and high impact energy...



And I think i answered everything that wasn't answered or was in question


(This post was edited by atlnq9 on Nov 19, 2008, 8:06 PM)


Partner angry


Nov 19, 2008, 8:17 PM
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Re: [atlnq9] Hardness testing of cam lobes [In reply to]
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Are you saying that the legendary soft lobes of Aliens are by accident?

I'm not defending them but they are known to have the softest lobes, to catch when everything else rips out, and will happily replace worn lobes. I fail to see the downside. Even if they aren't what they claim.


atlnq9


Nov 19, 2008, 8:37 PM
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My concern is that again they are showing that they don't know what they are doing. This just adds to the fact that they have shown they can't get a simple solder joint right. I ain't going to get into the argument of whether aliens are bad or good. And yes they will replace worn lobes. hands down they have a good design

But does it result in better holding power? The material will shear easier, but on the other hand form to the rock better. That will require a lot of research to prove or disprove.


Partner cracklover


Nov 20, 2008, 8:42 AM
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adatesman wrote:
hafilax wrote:
Can deformations cause a piece to pull?

Absolutely, if the cam is almost tipped out and smushing of the tips uses up the rest of the cam's range....

Yes, one of the failure modes is that the tips will flatten and the cam will invert like an umbrella inverted by the wind.

And yes, it seems fair to guess that an Alien would succumb to this failure mode at a lower force than a cam with a harder alloy.

But there is also another failure mode. In fact, my understanding is that the following is the primary failure mode IRL, for a good placement, in good rock:

The cam lobes flatten to the point where the angle is no longer creating a vector that resists the outward force. Then the cam tracks out.

In this case, too, the softer the cam lobes, the lower the force will be for failure to occur.

On the plus side for CCH, since Aliens use a higher cam angle (16, rather than 13 degrees at Metolius) an Alien should be able to flatten significantly more before it reaches that point where the angle drops below the holding point.

GO


andygravity


Nov 20, 2008, 9:14 AM
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atlnq9 wrote:
angry wrote:
I understand that.

I'm reading it as a Metolii or RE is more likely to blow out the rock.

Would that be an incorrect interpretation?

no, the bearing stress exerted to the rock would not be related to the lobe hardness, but related only to contact area. sorry to step in here aric


Wouldn't the softer lobes increase the contact area, and therefore we would see a decrease in the bearing stress?


atlnq9


Nov 20, 2008, 7:41 PM
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I think it would be nominal, if the hard lobe is resting against a small particle which would get embedded into the soft lobe it will probably pulverize it and end up with the same contact area...

Or were you thinking that the soft lobe will flatten, and provide more contact area? I still think that is even nominal.

I mean compare the contact area of BD C3's to Metolius Fat Cams, huge difference, this is where you will notice it...


atlnq9


Dec 3, 2008, 10:05 AM
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Here are the images from the hardness test.



This is the Rock Empire lobe, I started with this one. Note there is twice as many test indents. This was beacuase I changed the indenter and I forgot to lower the load from testing pitons, RC. When in the higher load I was getting the right hardness for a 6061 sample... so I didn't notice it until I went to the alien and got a hardness of RB 12. Way to low...



Alien, the top one was with the wrong load



Black Diamond, this lobe was quite distorted from the pull test. I had to do a bit of grinding on it so it would sit flat and have a smooth testing area.



The Metolius lobe


I hope to be finishing this up in the next three weeks. So my question would be once I find out more should I post it? Kind of an ethics question, there is a good chance they don't know what they are doing wrong, and I don't want to just tell them...


rightarmbad


Dec 4, 2008, 6:00 AM
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I think that the tests here show that axle bending is the most important failure mode shown so far.
I didn't see any cam lobes randomly breaking before distortion due to axle bending made the whole caboose fall of the rails.
I personally like soft lobes for the extra grip, I've never had a cam come out due to lobe crushing.
I think that you would find that it is more important to worry about axle stuff and that the lobes exact composition doesn't really do too much.
If it was so important, then link cams would not be usable with steel inner links.
Probably why titanium axles have never caught on.


lemon_boy


Dec 4, 2008, 7:20 AM
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i'm pretty surprised at the relatively comparable hardness values of the BD's versus the aliens, considering how much more quickly the alien lobes deform and/or wear down. interestting.

there is a lot that goes into the interaction at the lobe/rock interface from a contact mechanics perspective. it is pretty much impossible to implicitly say that harder is always better, or softer is always better. each circumstance will have its advantages and disadvantages.

good thread and thanks for the data.


rightarmbad


Dec 5, 2008, 3:34 AM
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What about grinding off the anodizing layer to see what hardness the base metal is.
(on lobes that are anodized that is)


adatesman


Dec 5, 2008, 6:57 AM
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rschap


Feb 28, 2009, 9:49 AM
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Yeah but then thereís hard anodizing versus regular anodizing. It is my understanding that hard anodizing means that it is left in the tank longer and the anodized layer is thicker. I know that this can cause problems with items such as belay devices where when it wares through the hard into the soft it creates a sharp edge that will abrade your rope. This could also make a difference on the cams no? Anyways my question is if you grind away the anodizing arenít you changing the results on the test? What if BD hard anodized and by grinding that away you got a different result?


moof


Mar 1, 2009, 8:52 PM
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5-10 mils sounds very thick. I'd bet that even hard anodizing is under a mil thick. Just saying...


adatesman


Mar 2, 2009, 8:15 AM
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