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deuce4
Social climber
Pagosa Springs CO
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Topic Author's Original Post - May 6, 2005 - 12:52pm PT
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Finally found a good use for an old proto ledge design. It was a design I worked on as a consultant (post A5 days) where the ledge was trapezoidal and enabled the inhabitants to lie with their back to the wall (rather than along it). It folded up like this link shows: http://bigwalls.net/johnm/UNSW/foldingledge.mpg
and the idea was to have both person's head closer to the wall in case of rockfall. Here's a picture from when it was used at a student camp-out protest in Harvard Yard.
It worked great on a tree or on flat rock, but on low angle the back side of the edge would slide up the wall.
But it had these nice hinged sections of beefly 1.375" 6061 T-6 Aluminum tubing. So I converted it to a nice backyard tightrope. Here's the pictures:
improvised anchor using river sand stakes (the tree stump is just for extra weight on the anchor.)
Used to be part of a portaledge
I used the Slackline Brother's nice tightening system--makes set up superfast and easy.
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Trashman
Trad climber
SLC
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that's funny, i remember that project. i remember a group of us trying to use one of the proto's in the backyard before a trip to zion and discovering the low angle issue while trying to use it on a tree. too bad it didn't work out, the concept was great(especially the double w/ the "gear hammock" in the middle
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deuce4
Social climber
Pagosa Springs CO
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Topic Author's Reply - May 6, 2005 - 05:39pm PT
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I think the design is viable, it just needs better placement of the suspension system--that's what caused it to creep up. Never made a fly for it. Have a better idea in mind anyway, if I ever got back into the portaledge design business... :)
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Landgolier
climber
Arlington, VA
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Was that harvard thing during the '02 living wage protests? I camped out a night or two (more because I thought the idea of camping in the yard was cool than because I was that into the cause), but don't remember the ledge.
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deuce4
Social climber
Pagosa Springs CO
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Topic Author's Reply - May 6, 2005 - 06:53pm PT
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Actually, it was the living wage protest, but it was either in fall or 2000 or spring of 2001 when I was in grad school there. I didn't really know much about the protests either, but it sure was fun to camp out in the Yaard (in the middle of the big city of Cambridge! a short walk to great coffee and chess hangs).
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funkness
climber
So,Ca.
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I like the bolt in the slab.
Hey, btw...looks like you're getting low on firewood.
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Ammon
Big Wall climber
Lake Arrowhead
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That's awesome John!!
You should start making kits.... maybe with slightly longer poles.
Ok, I have a question for you.
Going straight across from point to point is obviously going to require more holding strength than bending it over something, so.....
How much does it reduce the force when going over an a-frame, say if you're at a 45... vs. going strait across to a tree. I have a good idea but want to hear your opinion.
I would love to see these setups in places like Camp4 where slacklining is popular. I think the park officials might even like the idea.
Cheers, Ammon
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Ammon
Big Wall climber
Lake Arrowhead
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Well, OK...... they might not like it...
..... but, if it's less impact on the trees?
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Landgolier
climber
Arlington, VA
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Right, that was spring of '01, not '02
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deuce4
Social climber
Pagosa Springs CO
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Topic Author's Reply - May 7, 2005 - 11:55am PT
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well, I got the idea from Scott Balcom's nice book on Slacklining. The portaledge tubes are only 42" long, you's really want at least 55" tubes for nicer slackline lengths.
Forces using a tripod... I once did an analysis of the forces involved with highlines, determining that what you really need is a dynamic leash. I'll have to uncover those notes sometime, as it is difficult to correctly determine the overall forces, especially in the case of a whipper.
But in this case, as far as the anchor goes, off the top of my head, I think the forces using a tripod with an anchor to the gound will be reduced by a factor of the square root of 2 (at the anchor), but don't quote me, I haven't done any engineering analysis on it as of now.
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