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Climbing Physics Puzzler

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DLottmann:
This one is right up your alley Champ!

You have a 3 piece anchor in a bomber vertical crack with the classic “pre-equalized” 7mm 6m cordelette (looped with a double fisherman though that is not too relevant).

Your lowest piece is a solid #1 BD Cam. 6 inches above that you have a .75 BD Cam, and your top piece is a bomber looking #7 nut.

You tied off the cordelette to form a master point with a figure eight on a bight. The “leg” to the #1 is 6 inches long, the “leg" to the .75 is 12 inches long, and the “leg" to the nut is 18 inches long. The angles between the arms are very minimal, less than 10 degrees from the outer arms.

The leader clips the master point before leaving the station, climbs up 5 feet, and falls. Let’s assume the fall is clean, the belay sucessfully arrests (though it is violent), and all the gear holds.

Which piece of protection withstood the most force, or did they all receive 1/3ish.

Pete Jackson:

--- Quote from: DMan on November 05, 2013, 07:37:44 PM ---This one is right up your alley Champ!

You have a 3 piece anchor in a bomber vertical crack with the classic “pre-equalized” 7mm 6m cordelette (looped with a double fisherman though that is not too relevant).

Your lowest piece is a solid #1 BD Cam. 6 inches above that you have a .75 BD Cam, and your top piece is a bomber looking #7 nut.

You tied off the cordelette to form a master point with a figure eight on a bight. The “leg” to the #1 is 6 inches long, the “leg" to the .75 is 12 inches long, and the “leg" to the nut is 18 inches long. The angles between the arms are very minimal, less than 10 degrees from the outer arms.

The leader clips the master point before leaving the station, climbs up 5 feet, and falls. Let’s assume the fall is clean, the belay sucessfully arrests (though it is violent), and all the gear holds.

Which piece of protection withstood the most force, or did they all receive 1/3ish.

--- End quote ---

The #1 cam takes 55% of the impact force, the ..75 takes 27%, and the nut takes 18% of the force. 

And I cannot wait to hear the arguments over this one.

hobbsj:

--- Quote from: Pete Jackson on November 05, 2013, 08:06:38 PM ---
--- Quote from: DMan on November 05, 2013, 07:37:44 PM ---This one is right up your alley Champ!

You have a 3 piece anchor in a bomber vertical crack with the classic “pre-equalized” 7mm 6m cordelette (looped with a double fisherman though that is not too relevant).

Your lowest piece is a solid #1 BD Cam. 6 inches above that you have a .75 BD Cam, and your top piece is a bomber looking #7 nut.

You tied off the cordelette to form a master point with a figure eight on a bight. The “leg” to the #1 is 6 inches long, the “leg" to the .75 is 12 inches long, and the “leg" to the nut is 18 inches long. The angles between the arms are very minimal, less than 10 degrees from the outer arms.

The leader clips the master point before leaving the station, climbs up 5 feet, and falls. Let’s assume the fall is clean, the belay sucessfully arrests (though it is violent), and all the gear holds.

Which piece of protection withstood the most force, or did they all receive 1/3ish.

--- End quote ---

The #1 cam takes 55% of the impact force, the ..75 takes 27%, and the nut takes 18% of the force. 

And I cannot wait to hear the arguments over this one.

--- End quote ---

Care to explain?  Is it the the length of each leg?  Not seeing how you came up with those percentages.....May be the beer making my math skills fuzzy along with my vision.

danf:

--- Quote from: Pete Jackson on November 05, 2013, 08:06:38 PM ---The #1 cam takes 55% of the impact force, the ..75 takes 27%, and the nut takes 18% of the force. 

And I cannot wait to hear the arguments over this one.

--- End quote ---
I'm not sure how to compute that, but based on my understanding, that sounds right.  It's all pretty well explained in the second edition of John Long's anchor book.  Which is part of the reason why I keep a cordellette tied and ready for a sliding X anchor system, rather than the typical one described above.  One of these days, hopefully, my wife will be ready to swap leads with me and I can (to quote Strand) "just use the F'n rope". :)

DLottmann:
Pete got the gist of it. Let's let lucky like explain the why.

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