Machanical Wrist Joint

pittbull · Post by **pittbull** » Tue May 02, 2017 5:57 pm

I would like to build a doll with a wrist joint that works the same way as the human wrist does. A servo would control the movement. The same twist or rotation is in the leg too. I'm having a hard time visualizing how it work, hoping someone here has an idea.

Cnyb · Post by **Cnyb** » Tue May 02, 2017 6:19 pm

The radius moves relative to the ulna to rotate the wrist. At the metacarpals muscles contract along the pinky and thumb sides to move the hand to either side, and muscles along the top and bottom of the arm contract to lift up or pull down the hand.

So there is transverse (i think thats the correct term) rotation, lateral side to side contraction, and also dorsal/frontal hinge movement.

So hand hinge to go thumbside or pinky side, hand hinge to wave up or down, and rotation around axis of arm at wrist.

Same idea with the foot. Imagine rubber bands pulling tighter to move two bones closer together, as bprubber bands connected to bones on the opposite side rewlax and expand.