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majid_sabet
Jan 28, 2008, 9:26 AM
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Registered: Dec 13, 2002
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After examining the images I took of this TR anchor where a group of climbers were using a pulley instead of running the rope directly via TR biner ( see http://www.rockclimbing.com/...3;page=unread#unread)
and based on what most manufactures specifications are shown, the strength of the biner is rated in several different area however, the strongest part is along the major axis line and the weakest part is around the gate +-.
Based on this image and what I have seen in the past especially when you run multiple cords,ropes and equipments in the same biner, you are obviously not getting the maximum strength out the axis line in event of a shock load but somewhere in between min and max.
So how much strength do we loose as we get farther away from the axis line? 10% , 30%, 50% ?
What do you think ?
[URL=http://imageshack.us]
(This post was edited by majid_sabet on Jan 30, 2008, 12:24 AM)
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penoyar
Jan 28, 2008, 12:33 PM
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Registered: Aug 31, 2007
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Wish I still had access to super-computers, this would be simple enough to plug into an FEA program. Any mechanical engineering undergrads/grad students willing to do this? Intuitively, seems like you'd be shifting from full strength to whatever the axial strength of the gate is. But manufacturers don't report axial gate strength. Worst case, axial gate strength is the same as lateral gate (shear of hinge pin), say 1/3 of full strength. And that pulley has moved us about 1/3 off-axis. Gross approximation, you lose 22%.
Please send me 10 of these biners and pulleys to run experiments on.
(This post was edited by penoyar on Jan 28, 2008, 3:20 PM)
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marde
Jan 28, 2008, 6:04 PM
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these hms biners usually have a shape that puts the load
more in the middle than to the spine.
So i guess these biners are made for such a loading.
So it shouldn't be a really big loss in strenth.
At least for toproping i see no problem here.
But why would you use a pulley for toproping?
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qwert
Jan 28, 2008, 8:31 PM
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form the looks of it i would say this is a HMS or pear shaped biner, and as such it is designed to be loaded in the middle, rather than next to the spine.
however there could be a problem with those new ultralight and ultrasmall biners (camp nano, bd oz, mammut moses, ...) when combined with big slings, and for these things a normal "old school" nylon sling could be considered big.
qwert
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