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Re: [johnwesely] mooselette??:
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patto
Apr 6, 2010, 12:14 AM
Views: 3639
Registered: Nov 15, 2005
Posts: 1453
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johnwesely wrote: Citation please?
The discussion has been done to death. Simply put John Long only considered anchors that had negligable mass attached to the anchor. Testing wasn't necessary, basic high school physics tells you that such anchors wont experience significant increased load.
In contrast any anchor that has a load mass directly to it will experience 'shock loading' at a large multiple of the attached mass. Again this is high school physics.
In practice the belayer will often be the mass attached to the anchor and significant 'shock loading' on extension is likely.
For emperical results:
http://www.shariconglobal.com/...g_Anchor_Systems.pdf
In this testing shock loading increased the load 7.5x and resulted in 15-20kN total on the anchor. This testing isn't exactly representive either because it used a 260kg mass attached to the anchor which clearly is on the high side.
Neither John Longs testing procedure nor this one at all models are real scenario. In a real scenario with a belayer attached to the anchor extension lets assume a shock load multiple of around 5x, this is not unrealistic (though is completely dependent of anchor stretch). If the falling climber loads the anchor at peak 7kN, and the (heavy) belayer is loading it at 1kN, then the extension and resulting peak will be 7kN+1kN*5=13kN as opposed to 7kN+1kN=8kN.
(This post was edited by patto on Apr 6, 2010, 1:00 AM)
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Edit Log:
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Post edited by patto
() on Apr 6, 2010, 12:20 AM
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Post edited by patto
() on Apr 6, 2010, 1:00 AM
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