Dave Johnson has done it again with this fascinating mechanical dog head. Check out the action of the on-demand attention button. It's like hand-cranked animatronics!
The dog's head is capable of movement in four directions including side-to-side, up and down, the jaw, and the ears. Each movement is conveyed via pushrod. The pushrods sit on contoured cams, which are driven by a set of gears.
From the video description:
This machine is yet another attempt to get random(ish) movement from a decidedly non-random hand crank. The 4 gear pairs that drive the cams have slightly different gear ratios, so it takes something like 100 turns of the crank before the whole sequence repeats. The ear and jaw movements are also dependent on the current yaw and pitch position, so the result is a semi-random mishmash of movement. When the Big Red Button (BRB) is pushed, it lowers the cams out of the way, and the head falls into Squirrel! position.Johnson has very cleverly integrated a bellows on the front of the machine. The moving air serves to soften the motion of the head after the red button is released. That's a very nice subtlety that most people wouldn't notice. But watch again and imagine if that wasn't there.
Here is where you can see still photos of Dave Johnson's Squirrel!