When we were first assigned the midterm project, one of Milene and I’s brainstormed ideas was a teacup ride that is commonly found at amusement parks. As we were looking through the mechanisms on 507 Mechanical Movements, we saw that Mechanism #24 would help us achieve this movement.
First Checkpoint: Sketches
For our first checkpoint, we drew out how we wanted our mechanism to work. We were inspired by a YouTube video that we found online, which helped a lot with how to visualize the project:
We modeled our design similar to this video. In how we first pictured it, we wanted 6 cups total on the top plate with a centerpiece in the middle. We also wanted both the individual cups and the entire top plate to spin. Upon later iterations, we realized we drew this sketch out inaccurately because it wouldn’t make sense to have both the handle plate be connected to the top plate if the top plate needed to spin and the handle plate needed to stay stationary.
We also originally wanted each cup to have a smaller base and then grow wider at the top, so that it looked more cup-like. We also wanted to make sure that the cups hovered above the top plate so that when they spun it would reduce the amount of wood-on-wood friction.
The hardest part was figuring out how this would all work together. Since we wanted each individual cup to spin, we planned to have a dowel sticking through the center of each cup with a gear attached at the bottom. This gear would then interlock with a stationary inner gear sitting below the top plate. To get the actual top plate to spin, we envisioned a central dowel attached to the top plate and connected to a gear at the bottom. This bottom gear would then interlock with a separate gear attached to the handle; this is where mechanism #24 comes into play.
We then made some preliminary drawings in Illustrator, where we designed what the bottom plate would look like, the centerpiece, and each individual cup. We ended up just using maker case to design an open 2 in x 2 in x 2 box for each cup. For the teapot, I looked up icons on the noun project and made appropriate adjustments, like adding text and deleting extra lines. Lastly, for the bottom plate, I overlapped two circles because that is where the two bottom gears would be interlocking. The smaller circles represent the dowels for support.
Second Checkpoint: Low-Fidelity Prototype out of Cardboard
For our next steps, we finished designing the rest of our parts and started laser-cutting them with cardboard. For this prototype, we decided to just test the movement of one cup rather than multiple. We also decided that we would make all of the gears using wood, because we didn’t think that cardboard material would be strong enough. Everything else was made out of cardboard, and we attached everything using hot glue and wood glue.
We made sure to use a caliper to measure the thickness of the dowels we were using so that they fit snugly into the cardboard. In this design, the top plate was 14 inches in diameter. For the bottom plate, I overlapped the two circles using the Shape Builder tool in Illustrator. When designing the bottom gears, we adjusted their size to ensure they would fit within our bottom plate while still being able to interlock.
Left: cardboard designs in Illustrator, right: wood gear designs in Illustrator
When putting everything together, we used wood glue to attach the gears to the dowels. After assembling everything together, we adjusted the lengths of the dowels to cut them down. Below are a few images of our cardboard prototype.
Videos of it working:
Our prototype was pretty functional; when turning the handle, the cup and top plate began to spin. One main issue we saw was that the top plate sometimes began to tilt, which affected the way both the cup and plate spun by occasionally causing everything to get stuck. You can see the tilt of the plate in the middle image shown above. When presenting this to the TAs, they suggested that we use wooden washers in between the plates to ensure that everything remained perpendicular. Additionally, Milene and I decided to use a thicker dowel to hold the top plate up; that way, there would be more support. Other main takeaways from this prototype included scaling down the project and reducing the number of cups to 3. The more cups we had, the more opportunities there were for friction, so we wanted to reduce that possibility. We also knew that our next prototype would include the use of bearings for each cup and for any position where a dowel would go through a plate that remained stationary. Lastly, we wanted to make our gears and bottom plate each two layers thick in wood.
Third Checkpoint: Mid-Fidelity Prototype out of Wood
The next week, we started making adjustments by first editing our Illustrator files. We scaled everything down so that our top plate was 11 inches in diameter instead. We also designed a few different wooden washers that we planned on using to “sandwich” between plates or gears for additional stability. Additionally, we adjusted the size of the holes on the top plate to be the size of the smaller bearings. We also ordered larger bearing sizes for the thicker dowel to fit into. Because we had to wait for them to deliver, we had to estimate the size of the hole we had to cut in the wood. Online, it said that the bearings had an outer diameter of 1.25 inches so that is the size of the hole we drew out in Illustrator. The circles outlined in red below indicate that we were uncertain if the larger bearing were to actually fit into this hole and that we may have to make adjustments in the future.
One thing that took up a lot of time with this prototype was sanding down the dowels to fit into the bearings. When we designed our cups, we put a hole on the bottom side that was the width of the thinner dowel; however, to get it to fit into the bearing on the top plate, we had to sand it down. We used the drill press to make this process faster. We inserted the dowel into the drill press, turned it on, and held the sandpaper against the dowel so that it consistently sanded down a certain portion of the dowel. We made sure to use sandpaper of the same thickness for each dowel so that 0.5 inches of the dowel remained unsanded – this allowed space for the cup to be inserted into the dowel while still “floating” above the top plate.
Left: example of each individual cup; right: dowel being sanded down to fit into bearing
Some other minor issues we ran into while creating this prototype was gluing the bottom layer together to be two layers thick. The wood was somewhat warped, so when we glued the two layers together and tried to clamp it, the layers would often shift and the holes for the dowel supports wouldn’t line up. We had to spend extra time sanding down the holes so that the dowel supports could actually fit.
When we presented our prototype at our third checkpoint, it wasn’t entirely functional since the large bearings had still not come in. We at least knew that the gears at the bottom were interlocking smoothly when we spun the handle. To model the movement of the cups, we hand-spun the top plate and saw that each of the cups’ gears were interlocking smoothly. The TAs suggested that we placed a washer on the bottom of one of the gears so that there would be less wood-to-wood surface area contact for friction; additionally, we saw that if we put a washer beneath one gear, they would line up perfectly.
Creating the Final Product!
In creating our final product, we decided to create vinyl stickers to decorate each of our teacups. We decided on hearts, flowers, and butterflies. We stuck them on each side of the cup and then sprayed them each a different color. After drying, we removed the stickers which revealed the pattern on each cup.
While I was working on the vinyl stickers, Milene worked on creating our metal piece for the project: the handle. She used the water jet to cut it out, but we noticed that the circle in the center to hold the dowel was not even; we think it was because the metal used was so thick. We then used the drill press with a 5/16″ diameter to make it smoother and more circular. We were then able to fit the thinner dowel through the handle.
When the larger bearings finally came in, we realized the plates we had cut out originally to accommodate their size were not large enough. We ended up recutting all the plates in which the larger bearings were needed so that they fit snugly. Next, I applied a layer of oil to all the pieces. We originally wanted to use stain, but we didn’t like any of the colors available. The oil created a nice finish on all the pieces, and we let them dry overnight.
Over the next few days, Milene and I started assembling. We started supergluing dowels into place and wood gluing gears to dowels. However, we noticed halfway through that our central dowel holding up the top plate was warped; it caused our inner gear to shift when we started to spin the handle. Since we had already superglued the dowel into the bearing, we were worried that we’d have to restart the entire bottom plate. But, Milene and I did everything we could to get the dowel out: drilling it, sanding it, cutting it shorter, and then finally hammering it out (super glue is very very strong). We made sure to find a dowel that was actually straight and started reassembling.
The order in which we glued everything was very strategic – we made sure to secure the gears on the bottom, then make our way up. When we were nearing the end of the assembly, the most important part was the height at which the top plate rested on the central dowel. It needed to be low enough so that the gears of each cup interlocked with the inner gear, but not too low to the point where it would make too much wood-to-wood contact with the plate below. We measured this out carefully and placed washers in between the top plate to add extra support. We also decided to apply some WD-40 to the inner gear and each of the gears of the cups so that they would travel more smoothly and reduce friction.
In reaching our final steps, we noticed that the dowel for the handle was very long – this made it more difficult to turn the handle because more force would be required to cause the gears to turn. We ended up cutting this dowel shorter and also securing the metal handle into the dowel using super glue. Afterward, the mechanism was able to turn a lot better. Our final step was to attach the centerpiece. We made sure to position it so that none of the teacups would hit it when they spun. Finally, after probably over 30 hours of work, we finished! Photos and videos are shown below.
Reflections
This project definitely took up a lot of my time, but it was very worth it in the end. I’m very proud that we were able to get everything to work! I had a few doubts throughout the project, but seeing it move smoothly now is very rewarding. I’m definitely more confident in my design and prototyping skills after this project.
In terms of improvement, there were multiple times when we had to recut things because we measured incorrectly. For example, I had to recut the top plate multiple times because I had to ensure that the positioning of the bearings lined up with the inner gear on the bottom; that way, when a dowel and small gear were stuck through the middle, the gears would line up. Many readjustments were made with that.
Second, the handle plate on the right isn’t really aligned with the top plate on the left. The way I designed it in Illustrator, the handle plate is supposed to be in line with the top plate, but have an even spacing around it so that the top plate never touches the handle plate while spinning, shown below.
However, as you can see in the image below, our handle plate isn’t exactly aligned the way we planned it. We think it’s because when we glued the two bottom plates together, they weren’t lined up exactly. As a result, when we inserted dowels into the holes, the dowels were somewhat slanted and caused the handle plate to rotate or shift. To avoid this problem, we ended up just placing the handle plate slightly above the top plate to avoid contact.
Lastly, while our gears for each cup spin relatively smoothly, they do sometimes get stuck. This is because one or two of the cups’ gears were attached a bit slanted; thus, when it moved along the inner gear below, it can cause some issues. If we were to redo this part again, we would pay extra attention to ensure that the gears were glued on straight.
Cost
- ~ 5 plywood sheets = $10 (Amazon)
- Bundle of cardboard sheets = $12.40 (Packaging Price)
- 3 spraypaint colors, each $3 = $9 (Amazon)
- Adhesive vinyl sheet = $6 (Amazon)
- Superglue gel pack = $9 (Amazon)
- Woodglue = $2 (Amazon)
- 30 hours of work x $12 per hour = $360
- TOTAL PRICE: $408.40
