Robotic Hand
slide 1
  I bought mine at a thrift store for $1.00; the one shown above is selling on eBay for about $10. 
slide 2
  I kept the handle but cut off the finger-pulls. I added the pulleys to allow for easy placement of the servo motors ( one shown at far left) 
slide 3
  Three different types of wire was used.First was very tough spring wire but I found this to unwieldly. Next I used copper wire but it wasn't strong enough and broke. The 3rd wire is steel wire, same diameter (0.040") as the copper but twice as strong. I never changed out the first two.  
slide 4
  Three wires: spring, steel, copper, top to bottom.  It's a prototype, one must test out all possibilities. 
slide 5
  Three servos installed, two on top, one on back of frame.                           
slide 6
  Cover off hand so I could install springs for each finger.The plastic "tendons" were not strong enough to pull the wires back.  
 
I had a toy robot hand around for about 15 years, wondering what I could do with it. I knew it would join a robot someday. This was the type of toy where the user would squeeze the handle so the fingers would contract.   See photos.
Future Development: I hope to make another hand using aluminum parts for the fingers and force sensors so the hand doesn't crush things. It will eventually be part of a larger humanoid robot
Update 3Feb16: Found a good article in Servo Magazine with ideas on how to build a hand like this from scratch, using notched nylon tubing for the fingers. Video of the hand with moving fingers is here: Computer Controlled Robotic Hand
(Sequencing done with Lynxmotion Visual Sequencer and SSC32U servo controller)
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