Hello!
We are Zoe and Cali! When we first approached this midterm project, we wanted to create a gumball machine inspired by the Leaning Tower of Pisa. However, as we iterated, we realized that a design with a flat base would be more practical given the class time constraints.
Our final design consists of five main components that we developed throughout the process: the gear mechanism, cylindrical body, chute, container, and base. Each midterm checkpoint allowed us to refine these elements further, and our documentation follows this progression.
System Evolution
Gear Mechanism
While researching gumball machine models, we realized our design required a 90-degree gear system, where a side-mounted handle would turn a horizontally positioned gear on the cylindrical surface. This setup allows a gumball to pass through when it aligns with the hole in the wooden container and the large gear.
For increased complexity, we decided to use three gears of different sizes. Using a gear generator, we experimented with gear sizes and tooth shapes to optimize performance. We ultimately used gear 1 (N=20, D=5, P = 4, and PA = 12), gear 2 (n=18, P = 4.5, P = 4, and PA = 12), and gear 3 (N =36 , D = 6, PA = 4, and PA = 12). Additionally, we flattened the tooth shape to prevent the gears from jamming.
One challenge we encountered was gear sagging, since the side-mounted gears were positioned outside the chute. Even after using a sphere stopper inside the cylinder, the same issue occurred. To help with this problem, we added bearings on the wooden rod supporting the gears. This made sure the gears were straight and would stay in relatively the same position after turning and in contact with each other .
A lot of testing and realignment were done so the two side gear meshes smoothly with each other, and then with the third, 90-degree gear. The third gear was placed directly beneath the container in a flush position to keep it level. Two bearings were added underneath for stability, and finally, we included a circular ramp piece to complete the mechanism.
Cylindrical Developments
Choosing a cylindrical shape turned out to be one of our biggest challenges, as it impacted nearly every other component of our design. After consulting with the teaching team, we decided to construct the cylinder using a stacked donut shape with triangular cutouts on the edges. These cutouts were designed to complement the outer ring, which served as the chute (see image).
To build the structure, we stacked multiple donut-shaped pieces on top of each other. The base was a solid circle to add stability and weight, but as the structure went upward, it became hollow, allowing us to securely integrate our gears into the system.
Chute & Base
The gumball chute was created by using an outer ring of the same donut shape we used for the cylinder. This design allowed us to insert the chute into the cylindrical structure at an angle, spanning multiple stacked discs to ensure the gumball would slide down smoothly. However, one of our biggest challenges was sagging—when gluing the chute, it occasionally flattened more than expected, which affected performance during assembly and testing.
For the base, we used the same dimensions to create the chute, but allowed it to be laid flat (instead at an angle). A rim was also created such that it would hold the gumball. The pieces were attached using wood glue and clips to hold them in place while they dried.
Video: medium fideality prototype
Video: Gears – low fidelity
Vinyl Cut and Staining
For decoration, we vinyl-cut two different shell shapes and placed them on the horizontal gears positioned on the side of the system. We then applied a dark wood stain, creating a negative outline of the vinyl stickers. We also stained the rest of the gumball machine for an aesthetic finish. We ran into an issue where excess wood glue had spread unevenly, causing the stain to absorb inconsistently. To fix this, we re-stained multiple times, but some areas remained patchy despite our efforts. Furthermore, due to the narrow cutouts in the base of the tower, a paint brush was used to stain those openings. If we were to construct another iteration of this project, we would stain the parts before assembly.
Container
To hold the gumballs, we built a small container positioned at the top of the gumball system. The container was made by gluing multiple tin rings together, with the top ring having a slightly larger lip to prevent overflow.
The top of the container was a closed circle, engraved with our names, while the bottom circle featured a precisely cut hole. This design ensured that when the hole in the container aligned perfectly with the hole in the top gear, a gumball would be released into the chute.
After testing, we realized that the gumball needed initial momentum and guidance to start rolling. To address this, we added a circular wooden piece and sanded down one side to create a gentle ramp. Additionally, we repurposed extra pieces from the chute’s barrier to provide additional railing at the top, guiding the gumball smoothly into the starting point of the chute.
Final Product
After sanding everything down and conducting multiple test runs with lemon drops, we arrived at our final product.
If we were to do this again, we would focus on finding a more precise way to drill the holes for the side gears. Since we assembled the chute around the cylinder before adding the gears, we had to ensure that the gears were flush against the structure for the gumball to slide down correctly. However, some of our drilled holes were slightly too large, which led to unintended movement in the gears which we mitigated with some bevels. Overall, we are happy with our final product and excited to share it with others.
Cost Analysis
| 4 sheets of ¼’’ thick plywood | $21.92 |
| Wood Glue | $7.16 |
| Wood Stain | $12.98 |
| 7, 2 mm bearings | 12.99 |
| Wooden Balls (2) | $5.59 |
| Labor ($20/hr) for 24 hours | $480 |
Clean up
