RobotArmIt was fun building the arm with my seven year old daughter. The manual was great. Simply following it through step by step lead to a functioning device
this might be a replacement for the broken crane...
Not very easy to control tough - 5 DC motors, no detectors for position of jamming
I have some ideas how it could be implemented without adding too much electronics - by simply measuring the current that is drawn by the motors. This would have to be tested, possibly a 'arm up' move does not draw detectably less current that the 'arm blocked' move
If you'd like to see this arm online, post to the Forum