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General Climbing Discussion

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engineering students-wanna do research? 2-Dec-2008 At 1:26:31 PM Richard

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The load a piece of pro can take is probably much more dependant on the geometry of it's place ment, and the strength of the surrounding rock, than the strenght of the piece of gear itself.

But how stong is rock? how much does it vary - between rock types, and within a rock type? how much does it change when it rains? Gramps rock seems to get softer, but not araps rock. A quick internet search seems to indicate there is some info on the young's modulus - the elasticity of rock - and fracture toughness of rock, but not from a rock climing persepective.

If you assumed the geometry of a perfect nut placement - the shape of the crack matching the wedge shape of the nut, how deep in the crack does the nut placement have to be to be bomber given actual rock strengths/facture tougness? Sometimes you can place a nut into a crack well below the edge/line of the surface - you know this is bomber, but what if the nut is just in the crack, or even a portion is above the surface of the surround "wall"?

Is there a rule of thumb that could be identified, like at least 2/3rd of the nut must be in the crack to be a good placement (assuming full contact of both sides)... or that the crack must narrow by 1/10th the size of the nut to be sufficiently secure? (eg for a nut placed at 90 deg to the rock wall so the wire is horizontal).