An mechanical automaton is a machine built to perform a sequence of actions automatically, using only mechanical parts such as cams and levers. The sequence of movements is encoded physically in the shapes of the parts. For example, the profile of a rotating cam determines how a lever moves.
Historically, automata were often built to imitate living things or to perform tasks like striking the hours on a clock. Advanced automata could be powered by wound springs or falling weights, but many simple automata also used hand-crank mechanisms.
In the animation below, a cam inside the box turns on an axle. The axle is off-center, so that as it rotates, the cam lifts and lowers the lever on the top of the box, causing the crane to move up and down.
Here, the inside of the box (green) shows both the axle (blue) and the cam (red).
The box is made from five pieces of paper, the top and four sides. Additional layers are added to the lever to provide strength. The pillars in the four corners were created by extending the long sides and adding perforations so that they could be folded back in for support.
The cam consists of a central square shaft and five disks that have been slid onto it and then glued together.
The axle consists of a rolled piece of cardstock inserted through both the box and the cam.
The crane is a double layer of cardstock to add rigidity. Fold out tabs have also been added to either side of the base to add stability and a gluable surface.
All seams are held together with thin layers of PVA glue.