Forums: Climbing Disciplines: Trad Climbing: Re: [bearbreeder] Building anchors with the rope: Edit Log

Partner rgold

Jul 29, 2012, 10:22 AM

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Registered: Dec 3, 2002
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Re: [bearbreeder] Building anchors with the rope
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The picture in Long's book gives the hypothetical load distribution obtained by assuming the sling material obeys Hooke's Law. Tests subsequently showed that the estimates given by basic theory were on target.

Even materials that don't obey Hooke's Law in general have it as their first-order approximation, which means that they "nearly" obey it for small displacements. This is the basis for engineering calculations on deformation of steel beams, for example, which are not exactly what you'd call "stretchy."

The tricky part comes in understanding, for a given material, what constitutes a "small displacement." Whether climbing load displacements are "small" for the webbing in the Metolius Equalizer is something I don't know, but the point is that we don't have to postulate some high level of "stretchiness" to see the kinds of load inequalities predicted by Hooke's Law.

If the Hooke's Law approximation is appropriate, which I suspect it is without knowing for sure, then the Metolius "Equalizer," rigged as in their illustration, will have the same substantial loading inequality Gabe mentioned for rope configurations, in which case an equalizer it ain't.

Edit: Hooke's Law says that the tension in a loaded material is proportional to its percentage deformation.

(This post was edited by rgold on Jul 29, 2012, 10:27 AM)

Edit Log:
Post edited by rgold () on Jul 29, 2012, 10:27 AM

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