Final product

Key parts

• Single stage planetary gearbox, 4:1 gear ratio
• 28-BYJ48 5V stepper
• ULN2003 stepper driver board
• Arduino board

Project motivation

Seeing my senior friends getting stressed about life after graduation, I thought it was important for them to remind themselves of everything they’ve overcome to get this far, and that things will be more than okay. Everyone can always use a little extra silliness!

Challenges

1. Gearbox prototyping

Issue #1: Improper meshing between planets and ring gear due to tight tolerances from small tooth size (base width <2mm for sun & planet gears)

• 1st prototype: after changing from the Ultimater3 to PrusaCore printers, the planet gears were visibly more defined and were actually able to mesh with each other. However, the gears’ teeth were almost fully fitted into the ring gear therefore could hardly spin, so a solution was needed.
• Final solution: I scaled the ring gear in the x & y directions by 1.02 to offset tolerance issues. If I had more time, I would resize my gearbox and use a higher module value.

Issue #2: Improper spin in planetary gears due to contact friction with carrier.

• 1st prototype: since there were no small bearings immediately available, my first attempt was to use spacers + screws as a first prototype. However, the screws had too much contact friction with the planet gears, which made them stuck.
• Final solution: I printed small carrier rods that had loose sliding spinning contact with the planet gears. Despite the inefficiencies this worked well enough to turn the gears and drums.

2. Electronics organization

Issue #1: hiding visible components

• Solution: I assembled and arranged everything in CAD so that no components were visible from the window. This required careful dimension offsetting between the enclosures and exterior of the goose.

3. Aesthetics

Issue #1: Lack of definition in 3D printed letters on affirmation drums

• 1st prototype: in CAD, I cut out the letters from the outer shell and had the inner wheel painted black. However because the letters were so small, some supports were connecting the letters together which made them hard to read. On top of that, the white spray paint was also clogging the letters.
• Final solution: I laser cut and painted blocks that were fitted into the slots on a new version of the inner wheels. Then I colored the letters black which turned out much nicer.

Issue #2: Trouble hiding gaps between 3D printed goose body parts

• 1st prototype: As I had hot-glued the goose’s body parts onto the electronics housing, there were small gaps created between parts.
• Final solution: I combined wood filler and elmer’s glue to get a mixture that resembled the goose body’s texture.

Project highlight

My favorite part is the goose’s eyes. You can’t tell but they are actually single-use earplugs painted black (they have the perfect shine and shape)!

If I had more time…

1. Dowel joints between parts for more seamless joining
2. Larger gear module to minimize tolerance issues in planetary gears meshing