Motorized Trash Bin Dolly
As the semester project for our introductory engineering class, we were tasked with developing a device that would carry trash bins up steep driveways. Our client represented the needs of elderly individuals in a neighborhood in Chapel Hill.
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Our team's work, along with the work of several other teams, was featured in this Pratt School of Engineering article.
Brainstorming and Ideation
We began our design with an intensive brainstorming process. We totaled nearly 300 ideas, which were then filtered based on how financially realistic and mechanically practical each idea was. The remaining ideas were scored based on ease of use, durability, size, price, and environmental modification. Our final five ideas were synthesized to come up with our final idea: a motorized dolly that would run along tracks on the driveway.
Low and Medium Fidelity Prototypes
To gain a visual understanding of our design, we used paper and foam to create a very low-fidelity prototype (seen on the left). Moving towards higher fidelity, we decided to build a smaller-scale version of our actual design. Using two smaller wheels on the back and a larger wheel at the front, the device makes an angle with the driveway so the trash bins would sit parallel. We 3D printed bevels gears and used a 12V battery and a small motor to power the device. We saw there was an enormous amount of friction within the bevel gears, so we switched to a design where two separate motors would be directly attached to the back wheels. We also chose to have two front wheels rather than just one.
Final Prototype and Testing
Taking these changes into account, we began construction on the final prototype. We constructed a wooden base and kept a vertical difference between wheels to account for a 15-degree incline. We salvaged two 24V motors from a dysfunctional motorized wheelchair and attached these to our prototype using custom-designed motor mounts. We then circuited two switches, one to adjust polarity (direction) and one to adjust speed. We finally added two tension beams between the motor mounts to allow for a load of up to 200 lbs.
After our design was completed, we ran testing on ease of use (by a user-defined scale), ability to withstand elements, durability, driveway modification, size, and price.
