My First Application of Design Thinking - Hovercraft for The Tech Challenge

Claire Xu
2 days ago
4 min read

Updated: 1 day ago

In 2019, I assembled an all-girl team and participated in The Tech Challenge, No Roads, No Problem! This journey was the first time I truly applied design thinking to a real project.

The Challenge required building a hovercraft that could navigate various tracks with different terrains, including completely smooth sections, sections with a combination of smooth and sandpaper surfaces, and sections with a combination of smooth and pegboard surfaces. The rules of this Challenge are summarized in the picture below.

Raw idea

We began the project by learning about the mechanism of a hovercraft and conducting brainstorming sessions.

The raw idea of a hovercraft that came out of the brainstorming sessions was quite simple: we would build one fan that blows down, another fan that blows horizontally, and make a lot of holes on the bottom to let the air out 😅.

Prototype v1

Prototype v1 did not work, obviously, as it did not have a propeller yet, LOL. However, we tested a few things that determined the future improvements.

First, we decided to use a foam-board tray for the main body of the hovercraft due to its balance of sturdiness and weight compared to other materials, such as 3D prints, thin wood boards, and insulation foam boards.

Additionally, we evaluated different battery types, including AA Alkaline, AAA Alkaline, AAA Li-ion, and AAA 3.7V Li-ion batteries, as well as various propeller fan types, such as 2-blade and 3-blade options.

Prototype v2

For v2, we added two propeller fans that can make the hovercraft move forward.

We added a paper skirt around the hovercraft to capture air between the foam plates, but we eventually decided to remove it due to its friction, which made the movement slower and more unpredictable.

We also learned that we needed a more stable frame to hold the propeller motors, as the fans were getting too close and starting to hit each other 😭.

Prototype v3

In this version, we added an additional downdraft motor, aiming to increase the blow power to support the skirt. However, the additional downdraft motor did not provide much benefit due to air leaking from its opening. We tried different skirt materials, including plastic film, plastic film with internal foam support, and plastic film with airbag support. However, these modifications cannot enable the prototype to pass over the terrain with sandpaper sections due to the friction.

We eventually decided not to use an additional skirt; instead, we utilized the built-in skirt that came with the foam tray itself.

Prototype v4

The early version of this prototype could reliably pass the smooth terrain track, but only had a 50-50 chance to pass the sandpaper track and pegboard track. Especially the flat head of the early version always caused the vehicle to get stuck on the side of the track.

In the later version, we made a few modifications to improve the performance reliability on the special tracks.

First, we designed the stands of the propeller motors as two rudders to reduce spin without adding new structural components.

Additionally, we added a cursive bumper to resolve the sticking issue caused by the flat head. Furthermore, we added a stick between the propeller motor stands to prevent them from falling apart and getting caught in the wires.

When everything seemed to go in the right direction, we had a major setback! Our battery exploded when we tried to recharge it. We have to rethink our circuit design. Is that a battery issue or a design flaw?

Prototype v5 (candidate for the final build)

We continued to improve the performance reliability on the special tracks in this version.

We replaced the temporary bumper with a triangular-shaped body. We tried different propeller mount designs to finalize a solution that would provide the most reliable straight-line propulsion.

Although we believed that a faulty rechargeable battery likely caused the battery explosion, we separated the circuits for the downdraft motor and two propeller motors to use their own battery packs, thereby avoiding possible overloading that could cause overheating of the batteries.

Final Build

The final build incorporated all our optimizations.

We 3D printed a new tunnel-shaped propeller mount. This design had several advantages: first, it concentrated the blowing power by the tunnel and provided stronger propulsion than all our previous two propeller designs; second, the circuit for the propeller motor was simplified, which further eased our anxiety for battery issues; more importantly, it provided protection to the blades of the propeller and fingers (😭) when flipping the switches.

We carefully routed our circuits so you would barely see a single line on the surface. The battery packs helped balance the weight distribution, especially when we took on the requirements for high schoolers to carry 5 quarters with our hovercraft.

Although we had two circuits for the downdraft motor and propeller motor separately, we placed the switches for these two circuits next to each other, allowing us to turn on or off both motors simultaneously.

Of course, we added a flag with the icon of our team - the UNICORN.

Our final build performed very well in the challenge. We finished all 5 track passes on different terrain tracks in 21 seconds. The judges were blown away by our performance. They commented, "That's the fastest completion I've ever seen!" Ultimately, we won the highest award, the Best Overall Performance, in the Tech Challenge.

The project was the first time that I applied design thinking to accomplish a meaningful result. In each iteration, we learned from our mistakes, identified areas for improvement, and continued refining our designs. With this methodology, we turned a raw, oversimplified idea into five prototypes and a final product that fulfills all the required functionalities. My tech challenge experience inspires me to apply these principles in my future projects.

P.S. Although our final build is quite simple even from my today's point of view, it performed very well in the competition. We did play a few tricks to ensure its performance reliability. Stay tuned ...