Intro: Movement 429 and 2D Drawings

For this project I set out to make a working mechanical model of movement 429 (figure 1) from 507 mechanical movements. This was the same design I made a 2D drawing of for a previous homework assignment; however, my original drawing was imperfect, so the gears did not mesh. I started this project by first recreating the gear design using image trace, which I found to be tedious and imperfect. Many gear teeth were traced with different curvatures, making it unlikely that they would mesh. Finally, I started from scratch and used a gear generator to create my drawing. Because of the irregular shape of these gears, I generated a regular circular gear, then added the indents and larger teeth where necessary. This provided much better results (figure 2), and I was able to test these new gears on my first prototype.

Low Fidelity Prototype: Cardboard Box
My first prototype was a simple recreation of mechanism 429 out of cardboard, housed in a finger-jointed box frame (figure 3). Here, the gears did not mesh completely because the larger teeth would sometimes get caught on the edge of the indented area, causing the gears to get stuck. In addition, the multilayer cardboard was not very useful for testing functionality, since the inner layers of the cardboard often got caught on each other. This low fidelity prototype allowed me to reconsider the overall design of my frame, as well as what improvements needed to be made to the gears to achieve a better mesh.

 

Medium Fidelity Prototype: Pneumatic Gear System

On the second iteration of my device, I decided to ditch the box frame, as there seemed to be no real reason to house the gear system in a box rather than simply mounting it on a backboard. So I redesigned the frame to something more simple and clean looking. Another major change in this model was in the mechanism. Movement 429 was designed as a gear system to be operated on by steam, so I wanted to cause the gears to move using air flow. Thus, my second prototype incorporated a simple channel through the frame to allow a straw to be placed inside (figure 4). The only other change made in this prototype was in the size of the gear teeth and the overall spacing of the gears. I shrunk the large teeth slightly in an attempt to avoid the knocking I saw in the previous iteration. When I tried this model I found that the gears still got stuck occasionally, except when I spun them quickly. In addition, the wooden gears proved way too heavy to be turned by a pneumatic flow — at least not by mouth using a straw, or not with wooden gears. In the interest of time, I decided to abandon this idea and go for a simple crank mechanism in my final design.

Final Design Proof of Concept: Rice Engineering Owl
My partner Brian thought of a great idea for my project. He noticed a similarity between the shape of the frame from my earlier design and the shape of the Rice owl’s eyes, so he suggested that I make the gears the eyes of the owl. To test this concept, I needed to create or modify many drawings on Illustrator. This included obtaining a live trace of the Rice Engineering owl and saving it for etching, as well as tracing the shape of the owl for use as the backboard and frame (figure 6). After I did this, I practiced laser cutting and etching a small scale version of the Rice Engineering owl (figure 5). I found that the best etching settings were: P20, S35, with Jarvis style etching (settings used for final design). This model was also useful to visualize and confirm the design’s aesthetics. I decided to overlay the gears on an etching of the owl’s eyes, giving the appearance (to some extent) that the eyes were rotating.

Final Working Design: Rice Engineering Owl
Finally, I created a full scale version of the Rice Engineering owl, including a hand crank/knob on the back of the right eye. This crank mechanism is a simple knob connected to a dowel to which the right eye gear is attached (figure 7). I filed the hole in the owl backpiece to allow the dowel to spin freely. In addition, a small wooden washer is attached on the backside to prevent the shaft from moving out of the plane of the gear’s rotation. The left eye gear rotates on a fixed pin. For this model I also adjusted the gears again by making the big teeth much shorter and narrower to avoid catching on the other gear. This design finally worked nicely. In addition, I had to decide how to finish the parts. I sampled several stains on scrap pieces of etched wood (see below, top row) and ultimately decided to use danish oil to give the wood a medium level stain. This resulted in some loss of contrast between the original etched wood and the finished stain (see below, bottom row), but I think the overall look and color of the stain is still nice.

                                        

Final Thoughts
The greatest challenge in this project was perfecting the irregular shape of the gear teeth. I learned that these gears were not really intended to be turned by a crank mechanism or simply by meshing, since both are moved by steam in the original design. This made it challenging to get them to mesh nicely, since they would often get misaligned when only one was being cranked. If I had another iteration, I would have replaced the knob design with a true handle-style crank, which would make the gears easier to turn. Overall, the final design features a pretty simple mechanism with a greater emphasis on the aesthetics, and I wish that I had been able to increase the contrast more between the etched and unetched areas of the owl to really make it pop. In a future iteration I would consider using black paint over the etched regions and a wood stain over the rest. Lastly, I was unable to cut a metal piece using the plasma cutter, but planned to cut the pieces shown below (Figure 9). The washer shaped pieces were to be used as the knob in the crank mechanism, and the OEDK logo was to be included on the base. I planned to sand these parts and spray paint them black.

Click image for animation!