Turning a Simple Car Into a Speed Machine

Pinewood derby cars usually race down a ramp using gravity. I wanted to see if I could make one go much faster by using a CO₂ cartridge like a rocket. For this project I built a pinewood derby car that launches using a 16-gram CO₂ cartridge. I designed and built the car myself. Because the launching mechanism is powerful, my dad handled the actual launches for safety while I stood back and filmed the tests. The car did not work perfectly the first time. It took three tests and design changes before it worked well.

Materials

1. Pinewood derby block
2. Pinewood derby wheels
3. Pinewood derby nail axles
4. 16-gram CO₂ cartridge
5. Pour paint
6. Resin
7. Two small metal eyelets
8. Heavy String (for testing)
9. Fishing line (for testing)
10. Scrap metal for weight

Tools

1. Hand saw
2. Drill
3. Flathead screw driver
4. Rotary Sander with sand paper
5. Safety glasses and safety glove
6. Cups and stir sticks fox mixing pour paint
7. Cardboard box
8. UV resin light
9. Hot Glue Gun and glue

First I shaped the pinewood derby block so the car would be more aerodynamic.

I used a handsaw to cut the wood into the shape I wanted. Then I sanded the entire car until it was smooth. The smooth surfaces helped reduce air friction so that the car will move faster.

Next I drilled a hole in the back of the car to hold the 16-gram CO₂ cartridge. For safety my dad placed it in a vice and drilled the hole. The CO₂ cartridge is the engine that pushes the car forward.

I used pour paint to make the car more aerodynamic and for decoration. Pour paint spreads across the surface and makes colorful patterns. It leaves a smooth and shiny finish on the car.

I attached the wheels using the pinewood derby nails as axles that came in the kit. I pushed the nails into the wood with a flathead screw driver and sealed the axle nails with resin. I used the UV resin light for 60 seconds on each axel. This helps keep the axles from moving when the car rolls.

I attached a piece of scrap metal with hot glue for weight to keep it from rising.

On the first test I launched the car on asphalt. Because the launch is powerful, my dad handled the launch while I stood back and recorded the test for safety. When the CO₂ cartridge released, the car did not go straight. Instead it spun around like a helicopter.

What went wrong? The car had a lot of power from the CO₂ cartridge, and it was not strong enough to go straight. I also noticed that the front left wheel was not touching the ground.

See Attached Video

I tried to fix it by removing the scrap metal weight and adding two eyelets on the bottom of the car to guide the car with a heavy string.

For the second test I ran a heavy string between two points on the same asphalt area. The string ran through the eyelets under the car to guide it straight. Again, my dad handled the launch while I filmed the test for safety. The car moved forward, but it still did not work very well.

What went wrong? The string and the asphalt surface seemed to cause too much friction and slowed the car down. See Attached Video

For the final test I made two improvements. I replaced the heavy string with nylon fishing line for less friction. I moved the test to smoother concrete instead of asphalt. When my dad launched the car this time, it took off extremely fast. The car took off so fast that it hit the pole at the end of the fishing line and damaged the front of the car as well as the wheels broke off. See Attached Video

The CO₂ cartridge releases the gas very quickly. When the gas shoots out the back, it pushes the car forward like a rocket. The shape and the smooth paint finish reduces the air friction. Friction from rough asphalt and thick string caused the car to slow down. The switch to using a fishing line and smooth concrete gave the car less friction and was able to speed up much faster.

1. I learned about friction and aerodynamics.
2. A smoother surface is better for moving faster.
3. The Fishing line helped the car go straight.
4. That failing is a part of the process when you are engineering something.

Building a CO₂ powered pinewood derby car was a fun way to explore science and engineering. Even though the first tests failed, each test helped improve the design until it worked.

If I build another version in the future, I would try:

1. Make Stronger Axels
2. Find a smoother and longer runway
3. Keep the line for guiding the car
4. Change the design with more rounded edges

I am a 16-year-old student who enjoys creating and building things. I like experimenting with ideas and learning how things work. This project was fun because I built something I have not built before. I did all the design work myself, and my dad helped by the drilling a hole and launching the car each time for safely during the tests.