Custom 3D Printed Hardware
We started the project by developing a collection of 3D printed hardware to use in the automata. By starting with a common vocabulary, we hoped to both simplify the engineering process as well as visually unify the six automata the students are building.
Joseph designed the hardware using Sketchup. The hardware was designed to adapt both 3D printed gears and wood cams to 1/2 inch aluminum tubing, which is used for the drive shaft. Additionally, a now obsolete piece of hardware adapted gears and cams to 1/4 inch square wooden dowels. We decided for the larger automata we would use smaller diameter aluminum tubing, with a 3D printed adapted identical to the 1/2 inch adapter.
One of the most important pieces in the catalog of 3D printed automata parts is a 19 millimeter adapter with screw/rivet holes. The interior diameter of the adapter is the proper size for the aluminum tubing, while the exterior diameter is the proper size for the 1 inch cutter drill bit we used to drill holes in the frame. This adapter could be attached with a screw or a rivet to a 3D printed gear or to a wood cam. Additionally, there are two rivet holes in the vertical part of the adapter for attaching the adapter to an aluminum tube.
Josh designed the gears in Tinkercad. He used the Pro Gear Community Shape to generate a 2 mm tall gear, then resized the gear slighty, raised it 2 mm and placed it atop the slightly smaller gear. This created a crown gear shape.
The frame for this automata and the students' larger versions are made from primed stock three and 3/4 inches wide. The demonstration automata frame measures 23 inches by 13 inches. The stock is joined with wood screws that are concealed by using a Kreg jig.
Hand Crank Design and Construction
The hand crank that powers the automata is built from 6 inch wood discs left over from a previous project, aluminum tubing, and 3D printed hardware. Additionally, it used wood screws and rivets in its construction.
Cams and Gears Working Together
One student needed to transfer the direction of motion from the vertical drive shaft to a horizontal plane and rotate it, like you are looking at the propellor from a submersible cruising away from you.
He worked on a series of sketches illustrating how to use cams to transfer the direction of motion.
I used a large wood cam mounted on the drive shaft to begin with, but ended up needing to replace it with a smaller cam. Both construction techniques were the same.
After completing the automata and demonstrating it to the workshop students, they were impressed but a bit underwhelmed. The mechanics were interesting, but ultimately the piece lacked a narrative. In order to be complete, the automata's movement needed to tell a story.
One of the best pieces of advice I learned about building automata is to watch the movement the machine creates and build your characters and narratives around these movements. Resist the temptation to shoehorn a movement you desire into the automata machinery that might not move the same way you desire.
I observed the movements this automata made. There was a spinning drive shaft on the top of the automata and on its face, near the hand crank. There was also an irregularly shaped cam that moved up and down and had the tendency to spin. After consideration, I decided to keep with the nursery rhyme theme I previously explored and use "Hickory Dickory Dock" as the automata's narrative.
Many thanks for Joseph Schott's designs, workshop, materials, tools, and guidance.
3D models were printed on a MakerBot Thing-O-Matic with an MK6+ extruder in MakerBot red and tan ABS 3 mm filament and on a Replicator 2 in MakerBot red and natural PLA 1.8 mm filament.
This work and images copyright 2015 Josh Burker