final project

Wants

I’ve built a lot of little parts for quite practical things, so I wanted to make something more “useless” and whimsical. My main requirement:

• bring me joy

Some secondary requirements:

• I wanted it to be possible to store, it has to be disassemblable, small, or physically robust.
• I wanted moving mechanical parts, to push me a little - I have much experience in coding, less experience in mechanisms

Ideation process

My thought chain for landing on the peashooter went something like this:

• what if I did something geeky
• i saw someone make a snitch once that was kind of cool
• harry potter? (we can separate the art from the artist, right?)
• i could make Ravenclaw’s bird riddle knocker?
• it could slap you with a wing if you got something wrong
• i could use that for flashcard studying, not just for riddles
• slapping seems bulky, what if it shot you?
• then a bird shape doesn’t make sense
• what shoots?
• !!
• peashooter?

That seemed like kind of a perfect project idea, and so I started thinking of a design.

Design

The design process can then be seen from my week 1 documentation.

It’s not small, it’s barely disassemblable, but I hope it will pass physically robust - everything delicate is encased, and the shell seems easy to make sturdy.

It definitely has moving parts. I’m scared of those. We will see.

This might have to largely be 3D printed. I’m thinking I could CNC-mill the base out of wood, though, which would make it more organic (suitable for a plant) and sturdy. Ping pong balls I will purchase.

Design Focus: Shooting Mechanism

A gear chain might have been my first idea, but it likely wasn’t going to be the best one. I also sketched out the following mechanisms:

Where the summary is that:

• Two motors on flywheels would be the simplest if I just wanted something to shoot, but least satisfying to build
• A full geartrain was daunting, and I was worried about force transfer,
• Bands seemed… physically difficult, and inelegant when my rotations needed to be in opposing directions
• A spring-loaded mechanism would shoot pretty well! But given how the ball would have to be loaded and the space constraints within the head, the packaging seemed troublesome. This was the reason I wanted a flywheel mechanism in the first place.

Turns out I still couldn’t decide. I’ve always had trouble thinking of things in the abstract, so the next step was to prototype something.

Cue 3D printing week.

The gears were stiffer and louder than I expected, but worked fairly well. The stiffness could be mitigated by using bearings instead of having a plastic-on-plastic axel, but I was still worried about force transfer and the general loudness/impreciseness of plastic meshing, especially at speeds. With this in mind, I designed the sketched out the following mechanism next:

One motor, two gears, two bands.

Next steps

• Test and refine each mechanism
• Complete my CAD so it is no longer floating
• Design an activation mechanism (button press? voice? motion detection?)