We tested people doing pull-ups on a pebbly wall outside our building. With two Jacobi patches on one "ice axe" and two Nitinol patches on another, a ~145 pound person could be supported. With the setup we were unable to make heavier (~170 lbs) people hang off the wall, but we think we know why. The Jacobi toes were working extremely well, and supporting ~2/3 of the weight of the person, but the Nitinol toes weren't working as well. We think the Nitinol toes were running into their overload protection too early--we are currently making new sideplates which should fix the problem (they will be ready by tomorrow morning). If two Jacobi patches held 2/3 of 140 pounds, each patch was supporting ~47 pounds, which is still shy of the 64 pounds we expect we'll need, but is decent. We didn't test it on other walls because we wanted to limit the potential damage to the toes. A number of them got slightly duller, but that would have happened anyway.

Each person was able to hang for about 30 seconds and probably could have stayed there indefinitely. We were wearing safety goggles because a shower of little pieces of rock was coming down the wall--I'm not sure if it was just during engagement or if rocks continued to fall as people hung there.

On the negative side, when heavier people tried to climb but could not, the sound of the hooks all disengaging from the wall apparently made a lot of noise which the people inside the building could hear. One person came out and wondered what was going on. But, this only occurred when it failed and scraped down the wall, which we wouldn't expect to happen with a production system.

Finally, note that the patches and ice-axes we were using were much larger than they needed to be.. there was a lot of empty space in the patches, and they are also much taller than is necessary. So a production system could be a lot smaller. Everything was pretty heavy though!

See below for pictures and a short Quicktime video.

-- AlanAsbeck - 02 Oct 2007

• Mark #1:
  chris_short.mov: Video of Chris

• Prof. Cutkosky demonstrates the proposed new M.E. Ph.D. qualifying exam format.
  

• The ice axes on the wall: