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dbrayack
Jan 28, 2005, 12:24 PM
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Good Ole Statics; equilibrium, and of course trig, juts gets us climber engineers wet
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socialclimber
Jan 28, 2005, 12:55 PM
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Damnd if I know why those URL things won't work for me :lol:
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troutboy
Jan 28, 2005, 2:26 PM
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In reply to: I presume this guy isn't a climber, otherwise he would just be out doing it.
Your presumption is incorrect.
TS
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wjca
Jan 28, 2005, 2:40 PM
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Huh? So you put the cam where and F equals what? Seriously, I had discovered this a long time ago, but I couldn't figure out how to insert some of the symbols he used in the equations, nor did my computer allow me to use that pretty pink color in my graphs. My chance at climbing fame is waning fast.
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adamwvt
Jan 28, 2005, 2:56 PM
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I must be a climber, that link really made my brain hurt.
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sed
Jan 28, 2005, 3:41 PM
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sweet, this may be the first time i've seen facts on this site (within the constraints of math theories and assumptions of course).
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sed
Jan 28, 2005, 3:41 PM
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sweet, this may be the first time i've seen facts on this site (within the constraints of math theories and assumptions of course).
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bighigaz
Jan 28, 2005, 4:18 PM
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And the best part is, we all have this math in our subconcious!
We must! Because as climbers, we somehow make cams work... the proof is shown when we FALL on them... and they stay in the crack!
Well then, we are all much smarter than we give ourselves credit for!!!
"Here's to understanding the physics of climbing without having to do the math!"
:D
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berkly
Jan 28, 2005, 4:22 PM
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So if I am reading and comprehending this correctly, and if Im not please correct me, a cam placed in a flaring crack will hold at its maximum kN if the flare is 14 degrees (28 cumulative) or less, otherwise the cam springs would basically push the cam out of the placement.
In other words, if I place a cam in a flaring crack and it dosent spring back out at me, its going to hold? Basically saying a perfect placement in a flare is just as good as a perfect placement in a parallel crack.
If this is correct, it inpires a little more confidece in those flaring placements
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hanginaround
Jan 28, 2005, 4:25 PM
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Okay, I'm not an engineer so I need help interpreting the geek speak. Did he say that the wider the cam is open the greater the holding forces are? But, with cam wide-open, the forces of a fall could destroy the axle of the cam?
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chriss
Jan 28, 2005, 5:16 PM
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Remember that what you see, in this paper, is the ideal case.
Notice, tension T is centered and vertical. The "crack" walls are symetrical and linear, meaning angle a is equal for every lobe.
But they do work. And experience is the best tool you can have.
chris
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dingus
Jan 28, 2005, 5:19 PM
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Vain Kodas not a climber?
Hah!
Hah hah!
Thats a good one!
DMT
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curt
Jan 28, 2005, 5:20 PM
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In reply to: So if I am reading and comprehending this correctly, and if Im not please correct me, a cam placed in a flaring crack will hold at its maximum kN if the flare is 14 degrees (28 cumulative) or less, otherwise the cam springs would basically push the cam out of the placement. In other words, if I place a cam in a flaring crack and it dosent spring back out at me, its going to hold? Basically saying a perfect placement in a flare is just as good as a perfect placement in a parallel crack. If this is correct, it inpires a little more confidece in those flaring placements
As Vaino points out, increasing the flare angle of the crack has exactly the same effect as decreasing the cam angle of the unit--in terms of the forces involved. So, outward forces on the crack, forces on the cam, and forces on the axle all increase--theoretically becoming infinitely large, as the flare angle increases. Nearing this limit, something has to give and (as Vaino also said) the math breaks down because the rock will eventually break, or the cams will deform, etc.
Above 28 degrees of flare (for a cam with a 14 degree cam angle) the unit will not get any "purchase" on the rock at all, because the crack is expanding faster than the cam can.
As an aside, Vaino Kodas is a mechanical engineer with Profesional Engineer (P.E) certification. He also leads 5.13 and makes it look easy and has established hundreds of new routes both in Southern California and Colorado.
Curt
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nicklikesfire
Jan 28, 2005, 5:43 PM
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interesting page, thanks for pointing it out.
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bobd1953
Jan 28, 2005, 5:50 PM
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In reply to: As an aside, Vaino Kodas is a mechanical engineer with Profesional Engineer (P.E) certification. He also leads 5.13 and makes it look easy and has established hundreds of new routes both in Southern California and Colorado.
Vaino cranks and he has been cranking hard for a long time. I would think that his new route count is over five hundred.
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berkly
Jan 28, 2005, 5:53 PM
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Ah, ok makes sense. So in theory, a fall generating 4kN in a parallel side crack will generate 6kN just a guess (as the angle of the flare increases, the more outward force must be applied to counter) in a flaring crack?
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tradklime
Jan 28, 2005, 6:01 PM
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In reply to: So if I am reading and comprehending this correctly, and if Im not please correct me, a cam placed in a flaring crack will hold at its maximum kN if the flare is 14 degrees (28 cumulative) or less, otherwise the cam springs would basically push the cam out of the placement.
It relates to cam angle, the angle at which force is transferred to the rock. As you increase the cam angle you increase the range of the cam, but decrease the outward force. Most manufactures use a cam angle close to 14 degrees because it's considered the best compromised between expansion force and range, although not all manufacturers agree exactly.
Anyway, to your question, a flared crack will affect the cam angle between the rock and the cam. If the flare angle exceeds the cumulative cam angle than the result is 0 cam angle or less. Effectively, if you have less than 0 degrees reulting cam angle, the expansion of the cam will actually work to push the cam out of the crack.
The following link may add some information to help.
http://www.bigwalls.net/climb/camf/
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rgold
Jan 28, 2005, 7:20 PM
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As with most theoretical calculations, there is also a practical conclusion to take from this: beware of local flaring. By "local flaring" I mean that the crack has the flared configuration in a possibly small region of the point of contact of the cams. For such a placement, the very high compression forces apply, even though the shape of the rest of the crack will keep the cam from just popping out. What will happen instead is that the cam will break.
In areas with uniform-sided cracks, there is no local flaring and a flared crack is obvious. But in areas in which the interior of the cracks is highly featured, it is quite possible to stuff in a cam and not notice that the placement is locally flared. The result would be a mysterious failure that might be blamed on flaws, construction, metallurgy, or some factor other than the fact that the placement itself generated catastrophic forces.
There are threads here and on gunks.com about just such a mysterious failure of a cam on a relatively short but ultimately fatal fall on Boston, and there is a picture on gunks.com of the destroyed cam. Although we do not know what happened in that case, a locally flared placement is a candidate for an explanation.
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socialclimber
Jan 29, 2005, 1:17 AM
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In reply to: In reply to: As an aside, Vaino Kodas is a mechanical engineer with Profesional Engineer (P.E) certification. He also leads 5.13 and makes it look easy and has established hundreds of new routes both in Southern California and Colorado. Vaino cranks and he has been cranking hard for a long time. I would think that his new route count is over five hundred.
Thanks for the bio guys. I had no clue who this guy is. We tend to become a little insular living on an island in the Pacific and overseas climbing magazines cost NZ$25 each. I'm kind of glad hes a climber actually. This has turned out to be a vey nice thread and bloody interesting.
Cheers,
Gary.
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enjoimx
Jan 29, 2005, 1:47 AM
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i love this discussion. Very interesting. The author of that web page is very smart.
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jt512
Jan 29, 2005, 3:29 AM
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In reply to: Vain Kodas not a climber? Hah! Hah hah! Thats a good one! DMT
Dammit, Dingus. This is the second time you've scooped me in as many days.
-Jay
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norushnomore
Feb 3, 2005, 9:37 AM
Post #25 of 28
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Quote from the link above:
"a camming unit placement in a downward flare effectively decreases the camming angle and thus decreases the holding power"
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