Robot Hand Model Revision 5_11





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Uploaded on May 2, 2011

A simpler way to make the back of the Robot Hand. More information at sciencetoymaker.org
Sciencetoymaker projects tend to evolve from complicated to simpler—simpler usually being better. The robot hand project is no exception. So here's a little bit better way to make the back of the robot hand project.

The back doesn't get much attention, but that's where the other ends of the strings, or tendons, are glued. The layer of silicone that they are embedded in is also important. In a real hand, opposing tendons would straighten the fingers. But in this simplified model, the silicone springs the fingers back to the straight position.

Most of the original video instructions are still good. However, the original video instructions say to squeeze out beads of silicone on the back of the hand, push the strings in with a stick, then lay on a piece of cardboard that was smeared with soap as a release agent, to push the silicone flat. What a mess.

Here's a simpler way. After you cut out the hand pattern and cut the strings, flip the hand over and put it on a full piece of scrap paper.

Temporarily tape the pattern to the scrap paper with two tiny pieces of tape. I'm using red tape so it shows up on camera.

Tape the strings straight down middle of the fingers, but do not tape string on the pattern itself. The string ends are taped down just below the wrist. It doesn't have to look good. The string below the wrist will be cut off later. The strings radiate out the finger tips. The strings are taped just above the finger tips, and keep going. The string for the thumb is similar to the fingers.

I call the next step weaving the silicone bead. It's similar to what you'll be doing on the front side, so this is good practice. My students are now doing a much better job on the front because they have practiced the weave on the back. It also looks better.

You hold the silicone dispenser at a pretty steep angle and keep it close to the finger so that you push the silicone into the paper fibers. You linger on the sides of the finger. The silicone should go all the way to the sides. Each zig zag blends in with the previous one. Don't try to fix mistakes that go over the edge—you'll just make a mess. It's easy to cut off a blob of silicone once it has cured.

The next day, cut off the strings below the wrist and precede the original video instructions.

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