In order to start the assignment of making a mechanical model, my partner Ayaka and I started by making 2D drawings to represent the mechanical movement we wanted to use, and to start thinking about how pieces were going to fit together. We decided on mechanical movement 138. We planned on having a series of gears with cams that would push sticks up and down in oscillating motion. At the end of the sticks would be fish, so it would look like they are swimming.

Once we finished the drawings, we moved on to making medium fidelity prototypes. We first wanted to figure out how the gears would fit together, so we laser cut some out of corrugated plastic. For our medium fidelity prototype, we put the gears in a cardboard box with wooden dowels to visualize how our casing would hold the gears.

After this, we started high fidelity prototyping. We started by laser cutting the gears and cams from wood, and the sticks for the fish to go on from acrylic. We glued the cams to the gears, and glued a bearing into the hole in the middle of the gear + cam. We sanded down dowels so that the would fit into the center of the bearing, and the gears would spin around them.

Once we had the gears and inner mechanism of our device assembled, we laser cut the outer box. We had some issues getting the kerf right, but after a lot of test cuts, we figured it out. We also cut and rastered the name plate.

We also then plasma cut and post-processed the fish. We got AI files from thenounproject, plasma cut, angle grinded, and sanded them.

Then we began assembling the machine. We cut the dowels down to the width of the box, which caused some issues because any tool powerful enough to cut through the dowel was too large to cut the dowel that was glued into the gear to 1 inch in length. We had to pull the dowel out of the bearings, then re-glue them once they had been cut, which took some precision. Once we had done this, we glued one end of the dowel to the back of the inside of the box. One dowel was particularly wobbly and didn’t want to stay glued, so we used a washer around the base to get it flat.

Then we glued the other side of the box on top, and shut the box around the inner mechanisms, including inserting the acrylic sticks into the box. We glued the fish on top of the sticks, and the rounded bottom kept the stick from falling out of the box and ensured a smooth glide over the gears.

Instead of a bearing, the first out of the four gears had no hole in the middle and a dowel glued to either end so that the dowel could extend through the wall of the box and be turned in order to crank the machine. The dowel extends through two bearings, one on the inside, and one on the front outer face.

Once we glued the box together around the mechanism, we ran into some issues. The acrylic sticks did not seem to fully sit on the cams and would slide off sometimes when the machine was used. When we turned the crank, we believe that the cams sliding into the middle of the gears caused a lot of stress in the system, causing the crank to come unglued somewhere. However, the box had already been glued shut, so we could not properly repair the issue.

Here is a video we did get of our working gear mechanism:

In the final hour our machine failed, but we were still able to learn a lot about iterative prototyping and the precision that goes into creating parts of a moving mechanism. We also got a lot more experience using the different tools in the OEDK, which was really cool. Overall it was a fun experience and we are proud of the work we did!

Cost Analysis

• 1x 1/4″ thickness 4’x8′ plywood sheet = $5.97
• 1x 0.02″ thickness 6″ x 12″ steel sheet = $14.60
• 1x 1/4″ thickness 4’x8′ acrylic sheet = $15.45
• 6x bearings = $3.50
• Plasma cutter: $15/hour x 1 hour = $15.00
• Labor: 14 hours x $15/hour x 2 people = $420.00

(Cost of using laser cutter omitted because Harris County public libraries provide free use of laser cutters)

Total = $474.52

Link to slide deck: https://docs.google.com/presentation/d/1BTv2GAf755rMTQZCd6hrRa3-L8e-hPIoKag8dKNZnxw/edit#slide=id.g106632444b7_0_5