What is a flywheel?
A heavy spinning wheel stores energy. Once a heavy wheel is spinning it wants to keep spinning. A flywheel stores that energy and gives it back, so friction cars keep rolling and engines run smoothly between pushes.
Try Coasting Wheel Bench for freeComplete MightyCog booklet collection: 82 PDF booklets for $12.99. Instructions only; individual booklets remain free.
Explore the printable packTry it yourself
Spin the car's wheels fast on the table and let go. How far does it roll?
Build it: 5 builds that teach flywheel
- 🌀 Coasting Wheel Bench: Spin a retained tabletop wheel gently, then measure how it slows down. (level 2 of 5, about 15 minutes, 8 steps)
- 🌪️ Ripcord Top Launcher: Pull a toothed rack and watch two gear stages turn the top. (level 2 of 5, about 20 minutes, 18 steps)
- 🌀 Flywheel Friction Car: Vroom it on the floor, let go — and it keeps on rolling! (level 2 of 5, about 25 minutes, 5 steps)
- 🔥 Twin-Piston Engine: See inside a car engine: two pistons race up and down in turns! (level 3 of 5, about 40 minutes, 22 steps)
- 🚂 Sun-and-Planet Beam Engine: James Watt's steam-engine trick: a gear that never spins makes the flywheel turn four times per pump! (level 4 of 5, about 50 minutes, 17 steps)
In the classroom
- E7 Wind It Up! (Explorers, Foundation)
- I2 Energy on the Move (Inventors, Intermediate)
- M2 Energy Transfer (Engineers, Advanced)
Common engineering questions
How can I try flywheel at home?
Spin the car's wheels fast on the table and let go. How far does it roll?
Which builds teach flywheel?
5 MightyCog builds teach it: Coasting Wheel Bench, Ripcord Top Launcher, Flywheel Friction Car, Twin-Piston Engine and Sun-and-Planet Beam Engine. Start with Coasting Wheel Bench: 8 steps, about 15 minutes.