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My friend told me C4s "slip" because of the double axle
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By Sam Stephens
Mar 31, 2010
Top half of Melifluous

I'm so confused.

My history: Been plugging gear for a couple years now, comfortable climbing all levels of 5.10 and low to mid 5.11. No problem falling on my gear, no worries.

He's wanting to buy some gear and get into trad so he emailed me and asked me this. Here's our conversation. Can someone shed some light on this? I think he may be talking about walking, but I never know with Jim.

Sam,

Have you ever used any of metioluisís power cams? And what do you think of them? I know that BD has a larger rangeÖ but I am going for more bomb proof.


-Jim

Jim,

I've never used them but Metolious makes good stuff. Why do you say more bomb proof? I've never heard of failures with the BD cams pulling out unless it was a shitty placement. The greater range is a huge deal when finding the right placement. In all truth, I really don't like Metolious' camming angle. I've used their TCU's and I've never found them as easy to place as the C4's or Aliens

-Sam



Sam,

Yes bd has a larger cam-ing angle, but due to the dual axel design they are more prone to slipping. And I donít like that. I will show you some time what I am talking about.

See attached for my proposed trad rack. There is some extra stuff on there to.



-Jim



Jim,

I'd like to hear about this slipping phenomenon that I've never seen, experienced, or heard of with the C4s. In the meanwhile, look at these charts comparing cam sizes. Maybe you'll understand why I can't stand the Metolius camming angles.

img8.imageshack.us/img8/5029/camsizessmall.jpg
img36.imageshack.us/img36/5128/camsizeslarge.jpg

I carry C4s because I can carry less and cover more. They're basically the gold standard by which anyone compares cams. Do what works for you and what makes you comfortable, but when you have to start rifling through several different cams to get the right piece because the range is so limited, you're gonna wish you had some C4s.

-Sam


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By Greg DeMatteo
From W. Lebanon, NH
Mar 31, 2010

Sounds like he's doing too much math and not enough climbing.


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By Abram Herman
From Golden, CO
Mar 31, 2010
Viking helmet cover, yep.

Seems to me like he's talking about the cam angle, and the double-axles don't really have anything to do with it. With the BD's angle you have more range but less holding power (outward force), with Metolius' you have less range but more holding power.


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By Sam Stephens
Mar 31, 2010
Top half of Melifluous

I understand the difference in holding power with the different angles, I'm just trying to figure out what he meant when he said he'd show me how because they have double axles.

Like I said, no C4 has let go on me yet, or anyone I know unless it was a totally shit-tastic placement.


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By Brian Scoggins
From Eugene, OR
Mar 31, 2010

Well, to get a single axle cam to have the same range as a double axle cam would entail a larger cam angle, and thus a lower pull-out strength in the same placement. However, BD's cam range is due to the double axles, rather than its cam angle (which is still larger than Metolius'). It should not be the case that the dual-axle design has any measurable impact on pull-out strength, especially when I've never heard of a case of a cam pulling that wasn't due to rock failure or pilot error.


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By Brian Scoggins
From Eugene, OR
Mar 31, 2010

It should be easy to work out the equivalent cam angle and therefore make a comparison of the expected pull-out strength (the ratio of pull-out strengths is the inverse of the ratios of the tangents of the cam angles), but I just can't get the numbers to make sense. Its quite maddening.


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By brenta
From Boulder, CO
Mar 31, 2010
Cima Margherita and Cima Tosa in the Dolomiti di Brenta.  October 1977.

Brian Scoggins wrote:
It should be easy to work out the equivalent cam angle and therefore make a comparison of the expected pull-out strength (the ratio of pull-out strengths is the inverse of the ratios of the tangents of the cam angles), but I just can't get the numbers to make sense. Its quite maddening.

The tangents are related to the minimum friction coefficient required for the SLCDs to hold. The ideal, infinitely strong SLDC placed in ideal, infinitely strong rock never pulls out as long as the spiral angle is less than arctan of the friction coefficient. Conversely, if the angle is too large for the available friction, the cam comes out no matter how little force is applied.

Regarding the pull-out strengths, they depend on how strong is the construction of the SLCD. They also depend on the strength of the rock and the pressure applied to it. The pressure, in turn, depends on the contact area and on the spiral angle. Large angle means less normal force; hence, less chance of pulling out by pulverizing the rock. Larger angle also means improved ability to work in downward-flared cracks.


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By Brian Scoggins
From Eugene, OR
Mar 31, 2010

brenta wrote:
The tangents are related to the minimum friction coefficient required for the SLCDs to hold. The ideal, infinitely strong SLDC placed in ideal, infinitely strong rock never pulls out as long as the spiral angle is less than arctan of the friction coefficient. Conversely, if the angle is too large for the available friction, the cam comes out no matter how little force is applied. Regarding the pull-out strengths, they depend on how strong is the construction of the SLCD. They also depend on the strength of the rock and the pressure applied to it. The pressure, in turn, depends on the contact area and on the spiral angle. Large angle means less normal force; hence, less chance of pulling out by pulverizing the rock. Larger angle also means improved ability to work in downward-flared cracks.


I was just looking for a meaningful way to compare pullout strengths despite the fact that the coefficient of friction is not constant from one placement to the next, let alone from one rock type to the next. For this discussion though, its a meaningful relationship.

For instance, if you compare BD's cam angle (14.9 degrees according to a refined study of the #3 camalot you find that a Wild Country cam, with Jardine's 13.75 degrees, will have a pullout strength about 10% higher. Again though, nuances of the placement will always dominate ideal pull-out strength differences, and should be weighed against other concerns, namely stability, weight, and ease of use.

I see what you're saying though. Since the normal force on the side of the crack is directly proportional to the force pulling the cam outward, the more you pull, the harder the cam will bite. So I think it needlessly confuses things to call it "pull-out strength" but I can think of no better term. It is literally the force applied to the walls of the crack, expressed in a unitless ratio.


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By brenta
From Boulder, CO
Mar 31, 2010
Cima Margherita and Cima Tosa in the Dolomiti di Brenta.  October 1977.

Brian, if I understand, you called "pull-out strength" the outward force applied by the cam to the rock.


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By Alec
Mar 31, 2010
Stairway to Heaven, pitch three, Provo Canyon, UT

Any modern cam in a good placement will hold falls. Buy some cams, climb a lot, figure out how to place them well, and go from there. Skill in gear placement trumps the rest. Go climbing.


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By Greg DeMatteo
From W. Lebanon, NH
Apr 1, 2010

Sam Stephens wrote:
I understand the difference in holding power with the different angles, I'm just trying to figure out what he meant when he said he'd show me how because they have double axles. Like I said, no C4 has let go on me yet, or anyone I know unless it was a totally shit-tastic placement.




He thinks the cam angle is lower because the double axle makes them wider but the cam angle is lower because of the way the lobe is shaped.


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By Sam Stephens
Apr 1, 2010
Top half of Melifluous

I got to talk to him and this is what he told me:

If you place them in a horizontal and load them, the teeth slip. While I see what he's getting at, it's not technically correct. They don't slip, they just walk a little bit as the cam rotates downward. He said this worried him and he wanted single axle cams because they wouldn't do that.

What he fails to realize is that any cam is prone to walking, especially ones with center lobes that are close together, if your rope management sucks.


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By Stich
From Colorado Springs, Colorado
Apr 1, 2010
Coffee after freezing our asses off near James Peak.

I hardly think that your friend discovered a hidden flaw in Black Diamond's cam design that DMM is now using since the patent has run out. This sort of predisposition to sewing doubt without merit is more of a rc.nOOb thing.


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By coryred797
From Yonkers, NY
Apr 4, 2010

you need to stop giving him advice on this subject and tell him to TR and stick to second before he gets himself and his partner dead... Now I know new leaders need some advice and look for input, but cmon...

I have only climbed on 4 types of cams ever and thats BD C4's and C'3s, aliens, and tried out some metolius master cams. I have only had 1 problem ever with my BD cams and it was due to user error. I placed a .5 or .75 blind because I was getting pumped and my last placement was like 15 feet down so I threw it in and weighted it. I climbed up past it and it walked a slight bit and I heard the lobes click. My second said it was floating around in the crack fully expanded. Now I know the double axle design allows them to be used as passive pro, But I rather not ever have to test that out. Has anyone here ever used BD cams as passive pro?


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By MJMobes
From The land of steady habits
Apr 4, 2010
modern man

Stich wrote:
I hardly think that your friend discovered a hidden flaw in Black Diamond's cam design that DMM is now using since the patent has run out. This sort of predisposition to sewing doubt without merit is more of a rc.nOOb thing.


I've noticed a bit of RC.nOOb here at mtn proj this winter, more and more. Like the fact that we both replied to say so...

I have a friend who says cams are dangerous and to only place stoppers and hexes. That settles it, he said so...


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By Geir
From Tucson, AZ
Apr 4, 2010
Toofast

Sam,

BD cams are bomber.


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By Tyrel Fuller
From Denver, CO
May 10, 2010
Big Bend

Sam Stephens wrote:
I'm so confused. My history: Been plugging gear for a couple years now, comfortable climbing all levels of 5.10 and low to mid 5.11. No problem falling on my gear, no worries. He's wanting to buy some gear and get into trad so he emailed me and asked me this. Here's our conversation. Can someone shed some light on this? I think he may be talking about walking, but I never know with Jim. Sam, Have you ever used any of metioluisís power cams? And what do you think of them? I know that BD has a larger rangeÖ but I am going for more bomb proof. -Jim Jim, I've never used them but Metolious makes good stuff. Why do you say more bomb proof? I've never heard of failures with the BD cams pulling out unless it was a shitty placement. The greater range is a huge deal when finding the right placement. In all truth, I really don't like Metolious' camming angle. I've used their TCU's and I've never found them as easy to place as the C4's or Aliens -Sam Sam, Yes bd has a larger cam-ing angle, but due to the dual axel design they are more prone to slipping. And I donít like that. I will show you some time what I am talking about. See attached for my proposed trad rack. There is some extra stuff on there to. -Jim Jim, I'd like to hear about this slipping phenomenon that I've never seen, experienced, or heard of with the C4s. In the meanwhile, look at these charts comparing cam sizes. Maybe you'll understand why I can't stand the Metolius camming angles. img8.imageshack.us/img8/5029/camsizessmall.jpg img36.imageshack.us/img36/5128/camsizeslarge.jpg I carry C4s because I can carry less and cover more. They're basically the gold standard by which anyone compares cams. Do what works for you and what makes you comfortable, but when you have to start rifling through several different cams to get the right piece because the range is so limited, you're gonna wish you had some C4s. -Sam


sounds like this dude needs to get out and climb more


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