🎡 Crank Cruiser: step-by-step build

Turn the handle and the car rolls — every turn of your hand spins the wheels three times!

Long ago, railway workers zoomed along the tracks on hand-cars they powered by pumping a handle. This cruiser works the same way: you turn the red crank, the crank turns a big 24-tooth gear, and the big gear spins a tiny gear on the back axle. One turn of your hand = three turns of the wheels, so the car goes fast. But fast costs force: try pulling something heavy and feel the handle get harder to turn!

Level 2 of 5 (easy)
About 18 minutes
9 steps, 24 parts
Powered by: Hand-crank
Series: Gearbox & Drivetrain Cars

What you will learn

Gear Ratio: Fast or Slow: A big gear turning a small gear makes it spin faster.
Torque vs Speed: Slower gears are stronger gears.
Levers: A bar on a pivot multiplies your push.

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)

Parts you need

2 × Beam 11
4 × Black pin (grippy)
2 × L-beam 3×5
3 × Axle 8
6 × Half bush
1 × Tiny gear (8 teeth)
1 × Medium gear (24 teeth)
4 × Small white wheel
1 × Hand crank

Steps

Stand an 11-hole beam on its edge — the left side.
Push two black pins into the inside of the beam, holes 6 and 8, and snap a yellow L-beam onto them — short leg pointing up at the back.
Push 8-long axles through the 2nd hole and the 10th hole (and the yellow corner hole). Put a yellow half bush on each axle end outside the beam.
Slide the tiny 8-tooth gear onto the back axle, in the middle. Then slide the second yellow L-beam on behind it, short leg up, and push two black pins into its outside face.
Slide on the second 11-hole beam — over both axles and the two pins — and lock the axle ends with two more half bushes.
Hold the 24-tooth gear between the tops of the towers, resting on the tiny gear, and push an 8-long axle through the towers and the gear.
Lock the crank axle with a half bush beside each tower.
Push on the four wheels.
Push the red crank onto the long end of the crank axle, outside the wheel.

Play time

Put the car on the floor and wind the crank — off it goes! Now tie a small toy (or the battery box) behind it: is the crank harder to turn? That is torque.

Real-world inspiration

Hand-cranked toy cars and railway hand-cars (draisines) — https://en.wikipedia.org/wiki/Handcar

Build next

🕹️ Sliding-Gear 2-Speed Cart: Your first real gearbox: slide the crank axle to switch between strong gear and fast gear! (level 2 of 5, about 22 minutes, 8 steps)