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mcfoley
Sep 15, 2005, 4:27 PM
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OK we all have had cams "WALK" on us.
But do cams really "SKATE" in Granite?
Anyone seen/had this happen?
Assuming a parallel crack, with proper camming agle...
What other forces could contribute to this???
crystals breaking? Axle bending?
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landgolier
Sep 15, 2005, 4:38 PM
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Weak springs, sticky cams that need lube
Why are we talking about this?
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roy_hinkley_jr
Sep 15, 2005, 5:02 PM
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Part of the reason first generation Camalots are dangerous, narrow cams of hard alloy.
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poedoe
Sep 15, 2005, 6:17 PM
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Simple, its either one of two things:
1: the coefficient of static friction is not great enough
2: the normal force is not great enough
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double
Sep 15, 2005, 6:50 PM
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You're right to consider this. Try using a cam in a painted concrete crack like you'd find on a bridge abutment, or between steel. It's amazing how easily it will pull out. Cams work by friction. Very slippery rock may not provide enough friction.
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adeptus
Sep 15, 2005, 6:53 PM
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One of my friends recently did a climb where he got too pumped on a perfect granite crack. He just sat down onto a friend that he had inspected and it poped. So did the next friend and he ended up 2 meters above the deck.
So cams do skate out once in a while even when you believe they are bomber.
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nowinowski
Sep 15, 2005, 7:03 PM
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seat yours cams with a tug.
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thegreytradster
Sep 16, 2005, 1:20 AM
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In reply to: One of my friends recently did a climb where he got too pumped on a perfect granite crack. He just sat down onto a friend that he had inspected and it poped. So did the next friend and he ended up 2 meters above the deck. So cams do skate out once in a while even when you believe they are bomber.
A little refresher on the physics is in order. A cam develops about 1.5 times the outward force on the rock as the pull on the sling.
I once took a relitively short leader fall on a perfectly placed cam stuck verticaly under a roof.
The cam held the fall perfectly.
Then as I hung there with it at eye level, watching helplessly, it slid out, droping me onto the next piece, fortunately only three or so feet lower.
The force of the fall was plenty to make the cam hold, but body weight did not produce enough outward force on the cam to prevent it from sliding out. It was J Tree Quartz monzonite too. Even in areas with coarse textured rock, the inner surfaces of the cracks can occasionaly have a suprisingly slick, hard varnish.
It is an incredibly rare occurance. It is also however not out of the realm of possibility. set your cams like "adjustable" nuts when ever possible.
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marshall84
Sep 18, 2005, 4:59 AM
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In reply to: seat yours cams with a tug.
Please tell me this response is a joke. They aren't nuts. Tugging a cam is not going to seat it any better than it was when you placed it. The camming action is what gives it the friction to stay put. Tugging it just makes the cams open and only gives you a false sense of security that your placement will hold.
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goober
Sep 18, 2005, 5:38 AM
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Sure it will help... sometimes. In rough textured rock or fresh cracks found on newer routes it helps the cams bite through crystals, dirt, lichen, moss, or whatever else may be lining the placement. On the other hand these characteristics can be helpfull. With an extremely stuck cam (and on a low traffic route for obvious reasons) it is possible to very lightly lubricate (water soluble so that it easily washes away) the crack around the cam lobes to facilitate removal of an otherwise "welded" unit.
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alpnclmbr1
Sep 18, 2005, 7:14 AM
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In reply to: In reply to: One of my friends recently did a climb where he got too pumped on a perfect granite crack. He just sat down onto a friend that he had inspected and it poped. So did the next friend and he ended up 2 meters above the deck. So cams do skate out once in a while even when you believe they are bomber. A little refresher on the physics is in order. A cam develops about 1.5 times the outward force on the rock as the pull on the sling. I once took a relitively short leader fall on a perfectly placed cam stuck verticaly under a roof. The cam held the fall perfectly. Then as I hung there with it at eye level, watching helplessly, it slid out, droping me onto the next piece, fortunately only three or so feet lower. The force of the fall was plenty to make the cam hold, but body weight did not produce enough outward force on the cam to prevent it from sliding out. It was J Tree Quartz monzonite too. Even in areas with coarse textured rock, the inner surfaces of the cracks can occasionaly have a suprisingly slick, hard varnish.
I don't believe either of these stories. Oh, and the physics is wrong as well. (it's ~ 2x)
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atropine
Sep 18, 2005, 10:47 AM
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Try cams in some UK limestone, Wye valley etc - place cams into perfect placements & pull them straight out with one finger WC / DMM no difference - same thing with a sharp tug: straight out. The rock here is so hard & polished that even nuts & hexes will not seat - perfect placement, give it a monster yank to try to seat it & they will still lift straight out with barely a breath of upward force (easy for the second I suppose)
The best thing is you see people relying completely on cams for these routes - haven't they noticed?? I'm no big fan of hexes, but sometimes they feel pretty good on the rack
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ctardi
Sep 18, 2005, 4:54 PM
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In reply to: In reply to: In reply to: One of my friends recently did a climb where he got too pumped on a perfect granite crack. He just sat down onto a friend that he had inspected and it poped. So did the next friend and he ended up 2 meters above the deck. So cams do skate out once in a while even when you believe they are bomber. A little refresher on the physics is in order. A cam develops about 1.5 times the outward force on the rock as the pull on the sling. I once took a relitively short leader fall on a perfectly placed cam stuck verticaly under a roof. The cam held the fall perfectly. Then as I hung there with it at eye level, watching helplessly, it slid out, droping me onto the next piece, fortunately only three or so feet lower. The force of the fall was plenty to make the cam hold, but body weight did not produce enough outward force on the cam to prevent it from sliding out. It was J Tree Quartz monzonite too. Even in areas with coarse textured rock, the inner surfaces of the cracks can occasionaly have a suprisingly slick, hard varnish. I don't believe either of these stories. Oh, and the physics is wrong as well. (it's ~ 2x)
I could see them being real. Oh, and not all cams put out equal force. (They're made different)
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crackrn
Sep 18, 2005, 6:03 PM
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In reply to: Why are we talking about this?
Um...probably cuz the OP wants to. :angel:
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thegreytradster
Sep 21, 2005, 2:21 AM
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In reply to: don't believe either of these stories. Oh, and the physics is wrong as well. (it's ~ 2x)
I'm glad you have such an abiding faith in the technology.
I didn't beleve it was happening either, but an additional few feet of air time convinced me.
I've been doing this long enough to have experienced or seen even the simplest of it fail in completely unexpected ways.
I'll go for a well place nut any day and still adhere to this premise.
In reply to: "You know, all this gear is mostly for show anyhow. Real security comes from not falling off." --Jeff Lowe
Someone else's sig shamelessly appropriated.
When that's not an option? Never trust life or limb to one piece!
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