And so it begins… the feared midterm project. For this project, I (Linda Delgado) worked alongside Feyi Bankole to erect this model. We learned how to use 2D models to create a 3D movable design that can be interacted with and has parts that move independently.
Part I: The Idea
Our project was inspired by the recent solar and lunar eclipses, and a fun way to explain these phenomena is a geocentric orrery! Going back to some Ptolemaic astronomy helped us explain how the Sun, the Moon, and -of course- the Earth perfectly align to give us our unique eclipses; this model also explains why we always see the same face of the moon (the near side). We used mechanism #24 to make these pieces move and took inspiration from a midterm project from Spring 24, which we thought would work well with our project.
Part II: The Design and Prototype
I made a couple of designs for the box and the gears in Adobe Illustrator and see which ones aligned with our model the best. The gears were designed on geargenerator.com, and used Adobe Illustrator to put everything together. The first iteration used a box with finger joints, but we later moved to a stronger design that allowed for more room for error.
We later moved on to printing these to create a low-fidelity prototype. Unfortunately we weren’t able to finish this prototype due to both laser cutters catching fire. We were, however, able to cut out our two gears and see how/if they fit well together!
Part III: High-Fidelity Prototype
To produce a high-fidelity prototype of our model, I re-designed the top and bottom of our box, cut two identical pieces for each side, and a third with holes that allowed for anchoring of the stabilizing dowels. Then I glued them together. To ensure the correct placement of the holes, I measured everything on Adobe before cutting.
I also cut and glued together all of our support dowels for each gear. I repeated this process three times due to measurement and calculation errors. So, I had to adjust my methods to properly put everything together. Before gluing anything, I put everything together and marked all appropriate spots, took everything apart, and glued it; this was the longest process of the project for me. And after several contraptions, I was able to glue every moving part!
Part IV: Post-Processing
For the final touches, Feyi used the vinyl cutter to cut out star-shaped stickers that she later used as stencils. We sanded all the pieces down, and then Feyi coated the top piece of our project with white spray paint, strategically placed the stickers, and then coated everything with black spray paint. She also gave the
Feyi also used the water-jet cutter to cut out a star for our handle. She designed it in Adobe Illustrator, then cut and sandblasted it to give it a matte finish.
For the final touches, there was still some back-and-forth with gluing and post-processing because of the dowels sticking out to make the planets rotate.
Finally, I glued the planets onto the dowels and attached our nameplate to the top of the model!
Presentation and Video
Cost Analysis
| Cost Type | Cost | Price | Source | Quantity | Total |
| Materials | 4×4 1/4” birch plywood sheet | $29.88 | HomeDepot.com | 4 pieces | $119.52 |
| Materials | 5”x5”x3/10” 6061-T6 aluminum plate | $32.09 | Metaldepot.com | 1 piece | $32.09 |
| Materials | 4”x2”x 3/16” A36 steel plate | $23.78 | Metaldepot.com | 2 pieces | $47.56 |
| Materials | 12”x24”x1/8” Acrylic clear sheet | $15.23 | AcmePlastics.com | 1 piece | $15.24 |
| Materials | Sand Paper (180 grit) | $6.68 | HomeDepot.com | 2 sheets | $13.36 |
| Materials | Sand Paper (220 grit) | $5.98 | HomeDepot.com | 1 sheet | $5.98 |
| Materials | Wooden dowels | $12.99 | Amazon.com | 100 pieces | $12.99 |
| Labor | Laser cutting Operator | $10/hr | Self | 2.5 hours | $25 |
| Prototyping Engineer | $15/hr | Self | 15 hours | $225 | |
| Overhead | Facility Cost | $10/hr | Epilog M2 laser | 2.5 hours | $25 |
| Facility Cost | $10/hr | Plasma cutter | 1 hour | $10 | |
| Facility Cost | $10/hr | Sand blaster | 10 minutes | $1 | |
| Facility Cost | $10/hr | Waterjet cutter | 1 hour | $10 | |
| Quality Control | $2.50 | $2.50 | |||
| Design | Engineering and Development | $50 | Self | $50 | |
| Iterations | 2 previous versions included a press fitted box, a steel handle, and solid gears | $50 | |||
| Misc. | Waste and Scrap | Pieces of wood that amount to two 4×4 sheets were left unused and steel pieces for a previous iteration of the handle | $76.55 | ||
| Total | $585.23 |
For future iterations, the cost of the materials would go down because we would not need to use cardboard for prototypes. The cost of wood and design would decrease because we would not need to re-do all the gears in Adobe Illustrator, and we already have all the measurements.
