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Re: [majid_sabet] self rescue method, a complex system:
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papounet
May 2, 2007, 11:21 PM
Views: 6286
Registered: May 28, 2003
Posts: 471
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majid_sabet wrote: I had an hour to kill on Sunday so I stop at the local REI to check out the gears and saw a book on how to do self rescue. Some where in there (page 134), there was a drawing showing on how to rescue your partner incase he gets hurt and hangs like a pig on the wall similar to what you see here. In this drawing, a climber is hanging from the wall via big anchor (similar to top rope climbing) with a prussic lock in place near the anchor which acts as one way lock on his rope once the other guy pulls him up. ... They called this method “Complex Spanish …. with a (? - 1) mechanical advantage. I was wondering if you know what the mechanical advantage is on this system and why.
Why don't you give the complete reference ?
"Climbing Self Rescue: Improvising solutions for serious situations"
by Andy Tyson and Molly Loomis
Published The Mountaineers Books 2006
http://www.amazon.com/...178140877&sr=8-2
The schema is of a Spanish Burton 3:1 mechanical advantage system. it is not covered into "Mountaineering, The freedom of the hill" but is extremely close to the z-pulley or "mouflage simple" (advantage 3) The good thing about the Spanish Burton is that is is easier to stack up to create double system (advantage 5) or triple system (advantage 7) (incorrectly named "mouflage double" is in the french "manuel de la montagne" (page 527 and 559 if you wish to know). Compared to a normal block and tackle setup, a spanish Burton uses moving pulleys and requires less gear. It is somewhat superior to the classical 3/1 z-pulley system as it works with gravity on the pull side.
The triple system is often taught for crevasse rescuing, although the computations show below that even that may not be enough.
Please note/
a/ in all pulley system, the most efficient pulley (with the least friction) should be used for the "most traveled " part which is the past pulley. (but I could be mistaken)
b/a self blocking pulley such as a Petzl mini traction does wonder at the first pulley (belay side)
c/ a reverso is also quite good in replacing the top pulley and prussik
The issue of setup like this is that you have to reset two prussiks every cycle. Of course, the higher the mechanical advantage, the more rope you have to pull to lift.
for forces computation please see http://club.ffme.fr/...me.htm#slide0020.htm
Edited/ fixed spelling/ it is a Burton
(This post was edited by papounet on May 3, 2007, 5:28 AM)
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Post edited by papounet
() on May 3, 2007, 5:28 AM
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