Controlled and passive motion
There are two kinds of automata motion: controlled and passive. In our hand-crank monkey automata, cables attached to each side of the neck control the head movement by pulling the cables alternately, rocking the head from side-to-side. The legs also have controlled motion; the cables attached to the levers at the pivot point of the hip cause the legs to move up and down when pulled by the control mechanism.
The passive motion creates the illusion of more movement without having to add to the mechanism. Passive movements in the monkey automata are added through springs in the ankles that allow the feet to move independently, the arms have passive motion because the legs control their movement.
Certain factors have an effect on automata construction, in particular, weight affects balance and fabric restricts motion, so it is best to start with an armature that will move almost on its own. The cables used to create the movement are made of 49 hair fine steel threads sheathed in nylon making them very strong, this type of cable is available in jewelry supply stores for stringing beads. The crimps used to attach the cables to the crankshaft are silver tubes, which are tightened using special crimping pliers.
What we like best about this hand-crank mechanism is the interactivity. The automaton operator is the puppeteer, the showman. With a wind-up mechanism, the operator is an observer, but a hand-crank automaton allows the person to control the speed and direction. Stopping and pausing the automaton is as dramatic as moving it.
NEXT WEEK: Hand-crank automaton - Part III: Monkey Evolution