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Nefarius
Big Wall climber
somewhere without avatars.........
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Oct 17, 2008 - 06:47pm PT
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There's that saying about "if it aint broke..." I wasn't aware that there is any issue with cams "holding" in cracks.
Stronger? Sure, bring it on. Something new and ingenious? Right on, bring it! I guess I'm saying why not work on the things that are more prevalent and could be really revolutionary. But, then again, if I were a gear manufacturer thinking about "tires" for my cams, I guess that would mean $$$...
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Chris2
Trad climber
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Oct 17, 2008 - 06:52pm PT
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Damn, go easy Moof.
"Attacking a 30 year old fortified hill?!"
it's a college kid doing some research...
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Tom
Big Wall climber
San Luis Obispo CA
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Oct 17, 2008 - 10:49pm PT
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...mystery of Friend chatter and walking that parallel cracks produce
Been there, done that.
If you rotate the stem/cable out of the crack, the inner lobes hold, and the outer ones slide up; when the stem rotates back down into the crack, the outer lobes hold, and the inner ones slide up. Do this repeatedly, and the cam will walk upwards as far as it can - or until the lobes lock up at a constriction and one final tug fixes the cam pretty good.
This sort of oscillitory walking mechanism using exponential cams could be quite useful for a robot that, say, examines strange shafts in the Great Pyramid.
Or to place a cam just higher than you can reach, perhaps into a better spot, by wiggling the sling.
I've gone through about ten iterations of spring designs for the Valley Giants, and figure that they're just about where I want them. The spring tension of the WC and BD big cams is just too dang soft, as I see it.
WARNING - A cam with a small camming angle (high mechanical advantage) would have tremendous holding power (lots of friction) but could also pull expando flakes loose. I've seen enough Yosemite flakes open a bit under body-weight loaded cams that I wouldn't want any more mechanical advantage in a cam. The lateral force exerted by existing cams is high enough that I have placed one below a fixed piece, stood on it and expanded the flake enough to booty the gear.
I think that the existing camming angles (I use arctan of 0.25000000000000000000000000000, ~14 degrees, for the Valley Giants) are so close to being the same, it's splitting hairs to argue what company's angle is the best. The original Jardine design is quite close to what is universally sold today, and all of them represent a good compromise between holding power and a good range of usefulness.
Getting a cam to be more secure might entail using a second spring system, that allows the lobes to be retracted and placed, and then a set of supplementary springs engaged to increase the set-point load to the lobes. There is no question (in my mind, based on my experience) that higher spring tension on the lobes increases cam security, in terms of it's staying put and not wanting to wander off. This concept could involve cocking the cam at the start of the pitch, retracting the lobes to place it, and then pulling a second trigger to engage the stronger springs to increase the pre-load. Since weight is a big issue, this sort of complex mechanism would require some very good design skills to successfully implement. But, having stronger springs would, at the least, minimize the tendency of a cam to walk.
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