The dish and the spoon

• kal15

What a challenging and fun process this has been! This past month we worked on our midterm project! This included three check-ins, once a week, from the beginning of October. Since the beginning of the semester, I had already decided what I wanted my project to be: a cow jumping over the moon, an ode to the children’s nursery rhyme. I told Kaira about it and she was really interested (she was actually thinking of something animal themed too!) so we decided to work together. With our idea in hand, we had to figure out exactly how to build this thing.

Weekly Check-in #1:

For the first check-in, we needed to have concept sketches of the mechanism for our device. Since the concept was pretty self-explanatory (or so we thought) we both made some sketches of what we thought would make sense for the mechanism. I initially used mechanism #39 for our design, but when Kaira and I met up later, we found that Mechanical Movement #55 was a better fit so that the cow would actually circle the moon rather than just peep around the top edge.

With the mechanism now finalized, I started looking at how to make the gears. We started with gears I created in Adobe Illustrator (before we had access to the gear generator) and quickly discovered problem #1 with our design. It was essential to know the fixed distance of the two non-internal gears in relation to the internal gear to avoid binding. Thankfully we figured this out in our lowest fidelity prototype (scaled down cardboard). Once we generated the gears with the Gear Generator, we added holes in our backplate (moon) to help keep this fixed. It also helped to switch from testing with the thin cardboard to more robust stacks to increase contact between the teeth. Gear Generator was really helpful in doing most of the hard work for us, so we really only needed to input how big we wanted the gears to be. I also drew some sketches on Illustrator showing how the gears, cow, and moon wou

ld interface. Initially we considered doing a two-sided approach, with the light side of the moon on one side with the basic cow, and the ‘dark side’ of the moon with a ‘dark cow’ on the other, with both sides moving in opposite directions. We quickly scrapped that idea after talking about it more because of the complexity, and because we liked the idea of having exposed gears.

Kaira also ended up designing the cow! While I was working on the gear files, Kaira experimented with Illustrator to figure out the best way to draw it, and it ended up being the pride and joy of our finished product. Very mootiful indeed!

Check-in #2:

For check in #2, we needed to have a proof-of-concept out of cardboard showing that our mechanism worked. 

In this part, we iterated quite a lot. First, we used the laser to cut out the gears that I made with gear generator out of a thin cardboard. They weren’t really functional since we had an internal gear, so it is technically supposed to work while suspended in air. We troubleshooted by making a back piece behind the internal gear, and then checked if the gears worked. It still didn’t work that well because of how thin the cardboard (almost cardstock material) was.

At this point, we decided to recut the pieces all over again with thicker cardboard. We also ended up redesigning our gears. I had downloaded all the gear files separately and altered the size to our design (Gear Generator does not download files with a formatted size). I had also converted the files to AI, since for some reason the DXF/SVG files from the website didn’t upload to my Illustrator properly. When putting the gears together, the teeth didn’t match up properly (too few teeth, too many teeth). Kaira figured out a way to download all the files at once, and so we were able to change the size of the gears with respect to each other. We also thought it would be fun to add a little alien that pops out every rotation or so, as we could easily integrate that with our smaller gear.

To test out the final gears, we cut cardboard one last time. This time, the image sizes weren’t formatted to the right size (though the ratios were correct) so we had a miniature low-fidelity prototype. To ensure that the teeth of the gears were interfacing correctly, we cut multiples of each part and hot glued them together for thickness.here, we started testing post processing

At this point in the project, we were actually trying to figure out how to make the cow and moon rotate in opposite directions, which would have a super cool effect. This stumped us for a couple days, because we needed an additional secure plane but we didn’t know how to make it work with our project. With our original idea there were no issues but there was interference when rotating after we decided to add the surprise ET to the smallest gear, problem #2. As seen in the whiteboard sketches, we started with a very complex stack and after speaking with Dr. Wettergreen and Rachel decided to go for a paired down version. This meant that the cow would be attached to the moon but it reduced the layers required and the weight on the central dowel. At this point, we also determined what parts of our project would be wood versus acrylic,  as I will talk about later.

Check-in #3:

With our idea given the greenlight in check-in two, we immediately started cutting wood pieces for our final design with the laser. Kaira made some connection bars, the moon, and added holes for our dowels, and I cut the pieces out with the laser.

Both of us loved the idea of using acrylic, so we decided to cut the cow and a large disc on the same piece of acrylic. We actually rastered the cow’s spots to get some texture, which came in handy later when painting. Behind the acrylic disk would be a wooden disc (the moon), which we would paint and add some texture too. When placing the wooden moon behind the acrylic moon, we hoped to get a really cool effect. 

The handle, we decided, was going to be the part that was metal. To integrate our ‘dark side of the moon’ idea, we decided to cut a half moon shape the size of our full moon. When you turn the handle, the half moon moves around the full moon and gives a shadow effect. Plasma cutting, with all of the post-processing, was a pain in the last assignment. Therefore we decided to waterjet aluminum (which would also be lighted for our overall model). I had some trouble opening the document on the waterjet software. The AI file also didn’t want to create a single line in the software, so I had Danny come and help me figure it out. We had to redownload it in a DXF file for it to work. But the cutting process was simple, and we had our handle! We both really wanted to try out powder coating (which would also help smooth out the sharp edges of our handle without having to sand). With the help of a lab tech, we set-up the powder coating outside and started coating our moon. We wanted the moon to be black, but once we started spraying, we realized that the color was silver! We baked the moon anyways to see how it would turn out, and it ended up looking like we hadn’t coated it at all. Despite having put all the equipment away, we went for take 2, this time making sure the powder was the correct metallic black we wanted. This time, it worked and turned out great! We didn’t realize until halfway through that the powder wouldn’t stick unless the voltage grounder was being pressed, so there are a few patches here and there but overall the crescent looks great (probably my favorite part after the moon).

As you can see in the picture, the handle would attach to the dowel in the middle of the full moon. We didn’t love how that looked, so we considered adding a laser cut girl sitting on the ‘ledge’ fishing for stars. This proved to be too time consuming, and the fishing rod kept breaking so we scrapped that idea.

The dowel for the handle that drives the entire mechanism was another point of discussion for us. We had bearings that were a good size, but no dowel that fit those perfectly. There were smaller bearings with a correctly sized dowel available, but we were worried that the dowel wouldn’t be able to hold the weight of the entire system. For a minute, we considered sanding down the length of the dowel to fit the larger bearing. However, that meant ensuring that it was uniformly sanded so that it could thread through the 3-4 layers of wood (the wooden moon, the main gear, the stabilizer bar), so we ended up going the easier route with the smaller dowel. Hopefully this will hold up in the future!

Now, to hold everything in suspension, we needed a base. Kaira made some beautiful clouds on AI which could serve as a holder for the driving dowel. She had covered the wood with tape before lasering to prevent any burns, but we loved the contrast of the blue with the gray of the moon (which I will discuss later), that we ended up painting the clouds that same color. To hold the clouds in place, I suggested routing a plank of wood and sliding the clouds into it. We were able to get access to the woodshop and, using the table saw, cut and routed the base to size. Later on, we added a bit of glue before sliding the clouds in so that they would remain snug.

 

Now comes the fun part – painting!

As mentioned earlier, the clouds were painted a bright shade of blue. The moon was spray painted using various shades of gray, white, and silver. We used different techniques to get texture, including spraying really close to the surface to get pooling and bubbles, spattering, and using a dry brush to stipple the paint. Since we had a space-ish theme with the alien and cow, we decided to paint the gears in the back with a galaxy theme, again using different spray-paints to get the effect we wanted.

For the cow, first we sprayed black paint, then wiped it off. Because the spots and detailing were rastered, the spray paint got trapped in the texture and produced a clean canvas for painting on top. We then used nail polish to paint the white and pink parts of the cow. We had to use multiple coats to get the correct opaqueness, which meant that the back of the cow had weird texture. To correct for that, we cut another cow, painted the spots black, then epoxied it to the back of the first cow. We didn’t realize that the Gorilla Glue epoxy turned yellow when it dried, so on the cow facing the back, its fur is slightly discolored 🙁 We learned our lesson about trying too hard, and should have just left the texture or used a filling primer and white paint to get rid of it.

The alien also got a coat of bright green nail polish. Because we are in Texas, we decided to give the alien a little cowboy hat (though it looks slightly like a pirate hat). We designed and lasered it with wood, then glued it on the alien’s head. To fulfill the vinyl cutting part of the project, we vinyl cut a hat shaped sticker with some fun shiny purple vinyl to give the hat some drama.

Now that all the components were ready, we went forward with assembly! Earlier during phase 2, we had tested out the gears to see if they worked, and realized we needed some spacers on the gears to ensure the alien (attached to the small gear) wouldn’t hit the main dowel going through the large gear. We had some washers to help, but ended up needing more spacers at that point and at the interface between the crescent moon handle and the acrylic moon, as well as on the back of the system to keep the driving dowel in place. We cut some washers in acrylic of different thicknesses to allow for this.

With the system completely assembled, we decided to try it out before gluing it all together. It didn’t work! The cow was not moving past the bottom half of the moon. Some playing around with the mechanism revealed that the connection bar between the two gears needed to be fixed for this to work, so we quickly drilled some holes and placed some screws to ensure it stayed. Some stars we added to the handle for aesthetic purposes was also hitting our name plate, so we dremeled off the edges to prevent any interaction.

With the mechanism working great, we were ready to glue everything together. We used a combination of wood glue or epoxy depending on the material interface (wood glue for wood-wood, and epoxy for metal-metal and metal-wood). Once dry, we tested out the mechanism again to see if it worked (it did!), then cut the dowels, sanded the edges/extra paint, and repainted where needed.

And we are done! This took way longer than expected, but we are both super proud of the results. Here’s a video showing how it moves!

Front of Mechanism

Back of Mechanism

Overall, I think this project really emphasized the importance of planning and working early. With the milestones, it was easier to segment our project and plan all of our parts better. 

Powerpoint Part Breakdown

Our cost breakdown:

Total = $692.3

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