This project was much more complicated, and took much more time than we initially thought it would. We followed the project timeline, but still had a time crunch at the end due to trouble shooting and difficulties with our gears. Our end product, developed from lots of sweat and tears, was a zoetrope that creates a miniature robot animation.
Process
For this project, we took inspiration from a previous year’s machine. When the machine spun, the metal frame would create a fascinating pattern. That got us thinking; what if we did something similar and instead of a permanent metal frame, we had short, cyclic animation that would play? And thus we came upon the idea of a zoetrope, which is basically a rudimentary form of animation that quickly rotates a few frames around a center point to make the illusion of smooth movement. We found an example laser-cut zoetrope that used more complex mechanics to achieve rotary motion. We decided to use that model as a guide, but to ultimately simplify the design so that we could complete the project in a reasonable time. Our original design (Figure 1) is shown below.
Figure 1: Original Design Sketch
The first thing we did was a ton of research on the specifications that a zoetrope required, such as the minimum speed the drum had to rotate, the optimal spacing between the frames, etc. We found out that the ideal zoetrope rotates at 24 frames per second, so we decided that if we spin the dowel 0.5 times a second, and made the gear with the handle 1.5 times larger than the gear with the zoetrope, we would reach the frames/second necessary.
Our low-fidelity prototype (Figures 2 & 3) modeled the gear train we chose and some test fits of the wood panels into the top ring and bottom plate of the drum. This part caused some trouble, as our panel width calculations weren’t very accurate sometimes. Finally, we settled on a panel width of 5.2 inches and an insertion piece width of 2.6 inches. We laser cut the final product, press fit it together, and spray painted it black (Figure 4).
Figures 2 & 3: Low-Fidelity Prototypes
Figure 4: Final Zoetrope Drum
Next, we modeled the bottom of the machine. Originally, we wanted the gear train to be in a straight line and have a layer above and below to cover the gears. This was quickly reconsidered, once we saw that that idea would make the final machine extremely long. So, we shifted to an angled gear positioning and printed it out of cardboard to get the right size (Figure 5).
Figure 5: Further Low-Fidelity Prototyping
With all the details of the machine clearly defined, we moved on to our medium and high-fidelity prototyping. We laser cut the base out of wood and glued it together (Figure 6). We added spacers on the top to mitigate some of the surface area of the base hitting the zoetrope drum.
Figure 6: Medium-Fidelity Prototyping
There we faced another challenge: the gears would spin perfectly fine when the top of the base was not attached, but would jam as soon as the base was fully assembled. After consulting Danny and many minutes of utter devastation, we discovered that the likely cause of this was the gears being far too close together, which didn’t allow much room for error. After decreasing the size of the intermediate gear, the device started to run more smoothly. We added a few more bearings to stabilize the dowels holding the gears and started gluing everything together. Our end product is shown below (Figure 7), along with a slide show that details our final product.
Figure 7: Final Product!
Successes & Failures
Our project worked fairly well, and we added in the images with velcro so that they could be changed. Our main failures include the gears getting stuck sometimes, and this resulting in a fragile handle for turning. If done again in the future, we’d possibly make the middle gear even smaller of use square dowels for the handle.
Cost
- 3 sheets of ⅛ inch plywood: $10
- 6 assorted bearings: $3
- Paint, stain, and assorted finishes: $10
- 30 hours of labor x $12/hour x 2 people: $720
- Total cost: $743
