(I did not base my design off of the cover image, I found it online afterwards and I think it’s pretty cool that it’s similar).
Introductiron
For my design I decided to make an alien brushing its teeth. I modified movement 114 from 507 mechanical movements in order to make it move smoothly and fit my desired aesthetics. Because it is an alien, I thought it would be fun if his head moved back and forth off his body and the toothbrush remained stationary.
Drawing Time (and pain)
I began by refining the sketch of movement 114. I first traced it by eyesight on Adobe Illustrator and cut a cardboard model.
This model didn’t work, so after a few attempts at scaling, I imported the drawing to SolidWorks and more accurately traced the drawing from 507 mechanical movements.
Another cardboard model cut, a few more attempts at scaling, and I decide to scrap the drawing on 507. (Around this time I also noticed that the animation on 507 mechanical movements might skip a few frames to make it work).
Fine, I’ll Do It Myself
I use a rack and pinion generator recommended by a classmate, but I have trouble getting the angles to work correctly, and at this point I lack confidence in my basic design ideas. I decide to download the newest version of SolidWorks Premium in order to gain access to the toolbox (which has modifiable gears) and simulation capabilities. I spend an entire day downloading my new SolidWorks, fixing my new SolidWorks, and figuring out how to use my new SolidWorks. This was not a good use of my time, but I managed to make a cool animation of the racks and pinion interacting.
(I made a working animation with a rack on top and one on bottom to show that the gears would align correctly, but it broke at some point due to significant edits to the parts involved.) The animation did give me confidence that my basic design principles should work, so that’s something.
To the Real World
New cardboard model, success! Kind of, it’s still pretty janky. I think the problem might be that I’m not moving the racks linearly or holding the pinion sufficiently still, so I upgrade to wood for my next cut. I hot glue some little dowels to a piece of cardboard to make sure everything moves how it should, and now it works a lot better!
I spend a lot of time iterating in 2 Dimensions, trying to get everything to move as smoothly as possible. My final design gives the alien some jagged teeth and smushes down the back of the pinion.
I assume that if I can get everything to work in 2 dimensions, standing it up shouldn’t be too difficult. (This was very wrong.)
Dragon Imposter
Time to make my alien’s body. I have a lot of fun with the aesthetics, trying to strike a nice balance between scary and cute.
I end up with a mix of an Among Us character and a dragon, which I’m happy with. I also add eye stalks to the mouth and engrave the eyes onto them (I’m very happy with the ‘half-lidded’ look I ended up with).
(The tail was changed when I realized how pointy it was.)
I design feet on SolidWorks (so I can see them in three dimensions for the scaling), then reproduce them on Illustrator and cut them out.
Alien’s got some big feet, hopefully they balance out the weight of his big head (if they don’t I’ll have to nail him to a board).
Vinyl Cutter
Time for polka dots from the vinyl cutter. This was very simple, each color gets two dots of radius 0.5”. Find some pretty colors, good to go.
(This happens last chronologically.)
Waterjet Cutter
I originally planned on making the pinion out of metal, but I’m worried the differing thicknesses between the racks and pinion would cause problems. I look at some of the old projects for inspiration, and I really like a little lotus someone made as a rotational handle. I make two little flowers and stack them as a handle. The metal has a hole on each end, sized so that the threaded part of my chosen wood screw can fit through but the screw head does not. I plan on drilling the handle onto the toothbrush handle through the pinion.
Assembly (Tragedy)
Time for assembly. Nothing works. My plan was to make everything work in 2 dimensions, then use the magic of drilling to bring it to our 3 dimensional world. Unfortunately drills are not magical, and it is impossible to drill an 8 mm self-made dowel to a board, and more importantly, to drill into the end grain of composite wood. I kill my first alien by trying.
I realize that I have to back to the drawing board and rethink my overall design with integration in mind. My biggest concerns are making sure everything lines up perfectly, not ending up with any dangerous exposed screws, and getting my alien on his feet.
Recompense
My first thought is that I’m not confident in just making his feet snap fit. That would be a lot of asymmetrical forces acting over a small contact area. Instead I screw his feet into a separate, thicker wooden board. I then screw that board into my alien.
The finished product is incredibly stable. I had originally planned on splitting my aliens hand in half, drilling those halves together with the toothbrush in between, and drilling the whole thing to my alien. I thought it would be cool to give the authentic aesthetic that he was holding something.
Assembling this was impossible on two fronts, drilling into the thin side of the laser cut wood shatters it, and I couldn’t get the head of the toothbrush lined up perfectly with the holes on the body. I realize I’m going to need to redo my laser cut files, combining everything that is meant to exist in the same plane into one cut.
I’m still not sure how to attach everything, until I’m walking through the OEDK and it hits me on sight. Bolts! I calculate out all of my dimensions again, deciding exactly where the bearings and pinion need to connect to the body. Then I find two bolts that fit through my bearings and a third that snuggly fits through my metal parts. I do some kerf tests, then make holes in my aliens body that snuggly fit my bolts.
At this point I had planned on simply attaching my pinion directly onto the bolt for simplicity, but I soon realize that I’m better off putting a bearing in my pinion and a both through the bearing. (I should have also used a washer, an embarrassing oversight considering how long I spent thinking through how the toothbrush would connect with the handle.)
I assemble everything but the feet, and it works great in 2 dimensions! I scavenge the feet and wood from my previous alien and attach them to the new body. I stand him up and …
it doesn’t really work. I had been so focused on figuring out how to stand him up, I never thought to think about whether I should. Or, more accurately, I had not sufficiently thought through how to keep the rack from sliding off the back of my frame. On my previous design I had threaded a hair tie through the body like Dr. Wettergreen advised, but for the new body I was hoping that everything being dimensioned perfectly would offset that need, as the hair ties did add a lot of friction. This was silly on my part, and I’m hoping to drill some holes into my alien this weekend and see how much of a difference it makes.
I instead used a less committal fastener, tying a hair net around my alien’s neck and hand to giver him a little scarf.
Reflections
I am very unsatisfied with my final result. I truly did put a lot of hours into this project, I just didn’t spend those hours doing the right things. Because I planned on drilling things together, I didn’t fully integrate until reached high fidelity materials. Very sad, because I made the same mistake in ENGI 120. Hopefully this is the last time it happens. I also should have attached the handle off center, spinning doesn’t really work with the bolts, the friction will inevitably tighten them (although the washer did help). I’m hoping to make some small fixes over the rest of the semester, because I really want this to be a cool display piece.
Budget
Labor ~40 hours x $15/hr = $600
Laser Cutter time ~ $80
Lots of wood and screws ~ $50
Adobe Illustrator = $29.99 for one month
One Sheet of Adhesive Vinyl ~ $10
One Hour of Waterjet Cutting Time (consumables cost only)~ $20
Bearings = $9.73
Total = $799.72
