🌀 Flywheel Friction Car: step-by-step build

Vroom it on the floor, let go — and it keeps on rolling!

Have you ever had a toy car that you push "vroom vroom" and it zooms off by itself? Inside is a secret: a heavy spinning wheel called a flywheel. When you push the car, a giant gear on the back wheels spins a tiny gear five times faster, and that whizzes the flywheel round. Once a heavy wheel is spinning it does not want to stop, so it keeps pushing the car along. Some real buses and race cars store energy in flywheels too!

• Level 2 of 5 (easy)
• About 25 minutes
• 5 steps, 15 parts
• Powered by: Push
• Series: Mechanical Wonders

What you will learn

• Flywheel: A heavy spinning wheel stores energy.
• Stored Energy: Energy can be saved up in a spring and let out later.
• Gear Ratio: Fast or Slow: A big gear turning a small gear makes it spin faster.
• Axles & Wheels: A wheel on an axle turns dragging into rolling.
• Frames: A frame is a ready-made strong rectangle.

Build these first

• 🧪 Gear Speed Lab: Two cranks, two gear pairs: one makes things FAST, one makes things STRONG. (level 2 of 5, about 20 minutes, 13 steps)
• 🛒 Push Buggy: A sturdy buggy with a push bar held up by super-strong triangles. (level 2 of 5, about 15 minutes, 12 steps)

Parts you need

• 2 × Open frame 5×11
• 2 × Axle 12
• 2 × Bush
• 1 × Axle 9
• 2 × Yellow-hub wheel
• 1 × Giant gear (40 teeth)
• 1 × Tiny gear (8 teeth)
• 4 × Big tyre wheel

Steps

1. Stand a 5×11 frame up on its long side. Push a 12-long axle through the bottom corner hole at each end, and slide a bush onto the front axle right against the frame.
2. Push a 9-long axle into the 4th hole up at the back of the frame and slide a yellow wheel onto it, right against the frame.
3. Slide the 40-tooth gear onto the middle of the back axle and the tiny 8-tooth gear and the other yellow wheel onto the 9-long axle. Add a second bush on the front axle, 6 holes from the first.
4. Push the second 5×11 frame onto all three axles, up against the bush, and push the big wheels onto both ends of the back axle.
5. Push the last two big wheels onto the front axle.

Play time

Rev it up on a smooth floor and let go. How far does it roll? Take the yellow flywheel wheels off and try again — does it roll as far? Which car in the house rolls the furthest?

Real-world inspiration

Friction-powered toy cars and flywheel energy storage — https://en.wikipedia.org/wiki/Flywheel_energy_storage