Lego builder Barman makes an amazing stab at creating a fully functional Lego hand. My favorite detail is the motor that makes the fingers spread apart, which is a humanlike feature that most robot builders neglect.
The hand holds 4 NXT motors to control the fingers and thumb. The 4 fingers are controlled by the 2 outside motors, that are attached to the index finger and pinky. All fingers are connected to a sliding beam, so that the middle and ring finger can also move. This system makes the hand compact, because you don’t need 4 motor for each finger. The drawback is that the fingers can’t be move separately. Anyone who has seen this always asks if it can give ‘the finger’, the answer is NO The middle motor has 2 functions. It moves the thumb from and towards the hand. When the motor rotates further it touches the construction that make the fingers spread. So the thumb first moves a bit and the last past of that movement the fingers spread as well. The last motor moves the thumb in and out. It give a nice impression as a palm of the hand.
[via The NXT Step]