Mouse Trap Car
A mousetrap-powered car designed to travel 5 meters. It hit 15 meters after a full redesign.
// Challenges
The fast-car design we started with had poor traction and weak structural parts. We had to redesign for distance. Longer car, bigger lever for more mechanical advantage. Even after the redesign, some parts kept breaking.
// Skills Used
// Outcome
A redesigned car that hit 15 meters, 3x the requirement. We missed the final test day, but I was proud of how it looked. Next time I would use stronger parts and better wheels.
Brief
Build a car powered by a single mousetrap. Make it travel at least 5 meters on a flat surface. The challenge is converting the short, fast snap of the mousetrap spring into sustained rotation of the wheels.
Process
Our first design optimized for speed. Short wheelbase, short lever arm, light wheels. It looked fast and it was. For about a meter. Then traction problems showed up. The wheels spun freely instead of pushing the car forward, and a couple of structural pieces cracked during testing because we had cut weight in places we should not have.
We sat down and rethought the strategy. The brief asked for distance, not speed, so we redesigned the car around mechanical advantage. We made the chassis longer, mounted the mousetrap further back, and ran a much longer lever arm that pulled string off a slower-rotating axle. The new car released its energy slowly, kept traction longer, and went a full 15 meters on a clean run. That is 3x the minimum requirement.
Some parts kept failing during testing. The string anchor pulled loose more than once. A wheel cracked at the hub. Each failure pointed at materials and structural decisions we had made too lightly.
Skills Built
- Mechanical advantage and gear ratios in practice. I had read about levers in physics class. Watching a longer lever arm turn into actual additional distance made the concept stick in a way reading never would have.
- Iterative prototyping. Our first design was wrong for the brief. Knowing when to scrap and redesign instead of trying to patch the failing version is a skill that has paid off in every multi-step project since.
- Materials selection and structural intuition. Where weight matters, where strength matters, and which trade-offs are worth it on which parts.
- Reading the brief carefully. Distance, not speed, was the actual goal. Reading what you are actually being asked to optimize for is half the work.
What I would do differently
I would build a small spreadsheet to model the relationship between lever arm length, axle radius, and predicted distance before cutting anything. That way I would walk in with a hypothesis to test instead of building, testing, and rebuilding from scratch. Also stronger wheels with grippier tires from the first build.