Designing a Ramp Car for Maximum Penny Load: Jayden's Racer 2/10/25

I set out to build a small ramp car in my engineering class with one clear mission: carry as many pennies as possible down a 1.5 m wooden ramp set at a 25° incline. Using Fusion 360, I modeled a low-profile chassis with a wide footprint to keep the center of gravity low. From the initial sketch-extrude steps to refining every fillet, I focused on creating a strong yet lightweight structure that could withstand the weight of dozens or even hundreds of pennies without flexing or twisting.

For traction and stability, I chose 60 mm diameter wheels spaced at the chassis’s extremes, pairing them with slim rubber O-ring tires to balance grip and rolling resistance. In the center, I carved out a shallow rectangular penny tray and reinforced its walls with 1.5 mm fillets to prevent deformation under load. After 3D printing the chassis in PLA, I assembled the car and ran preliminary tests, noting how small changes in wall thickness or tray depth impacted the overall strength and penny capacity.

During ramp trials, the car reliably carried up to 180 pennies about 50 g before the wheels began to slip. Pushing the load past 200 coins raised the center of gravity enough to cause tipping at the ramp’s transition points. I also discovered that heavier loads increased traction but slowed descent, while lighter loads sped down the incline but risked wheel spin. Around 150 pennies proved to be the sweet spot: stable, fast runs without slippage or tipping.

This project taught me the critical importance of weight distribution, as shifting the penny tray just 5 mm forward reduced rear-end lifts and improved straight-line stability. I learned to balance roll resistance and traction by experimenting with different tire materials and widths. Iterative prototyping revealed hidden weak points like tray walls flexing under heavy loads that I addressed in subsequent prints. Logging run times and tilt angles for each test allowed me to plot performance curves and pinpoint the maximum safe penny count.

Looking ahead, I plan to install low-friction bearings in the wheel hubs to cut drag, design adjustable tray inserts for fine-tuning the center of mass, and even add a lightweight spoiler for aero-stability on steeper ramps. Have you ever designed a load-carrying ramp car? What strategies did you use to balance weight, speed, and stability? Share your insights I’m eager to refine this design even further!