🌀 Propeller Push Car: step-by-step build

Push the car and the propellers on its back spin three times faster than the wheels!

Brrrrm! This little car has two propellers on its back, but no batteries at all. When you push it, the back wheels turn a big 24-tooth gear. The big gear turns a tiny 8-tooth gear on the propeller axle. Every time the big gear goes round once, the tiny gear has to spin round three times. So the faster you push, the more the propellers whizz!

• Level 1 of 5 (super easy)
• About 12 minutes
• 8 steps, 25 parts
• Powered by: Push
• Series: Gearbox & Drivetrain Cars

What you will learn

• Gears: Gears are wheels with teeth that push each other round.
• 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.

Build these first

• ⚙️ Gear Friends: Three gears holding hands — spin one and they all dance. (level 1 of 5, about 8 minutes, 6 steps)

Parts you need

• 2 × Beam 11
• 4 × Black pin (grippy)
• 2 × L-beam 3×5
• 2 × Axle 10
• 6 × Half bush
• 1 × Medium gear (24 teeth)
• 1 × Axle 6
• 1 × Tiny gear (8 teeth)
• 1 × Knob wheel
• 1 × Tan knob wheel
• 4 × Yellow-hub wheel

Steps

1. Stand an 11-hole beam on its edge. This is the left side of the car.
2. Push two black pins into the inside of the beam, in holes 6 and 8. Snap a red L-beam onto them: its corner hole lines up with hole 10 and its short leg points up.
3. Push a 10-long axle through the 2nd hole (front) and another through the 10th hole and the red corner hole (back). Put a yellow half bush on each axle outside the beam. Leave room outside the bushes for the wheels.
4. Slide the big 24-tooth gear onto the back axle, right in the middle. Then slide the second red L-beam on behind it (short leg up, long leg forward) and push two black pins into its outside face.
5. Slide the second 11-hole beam onto both axles and the two pins, then lock the axle ends with two more half bushes. Now both red towers are locked, and the big gear is trapped between them.
6. Hold the tiny 8-tooth gear between the tops of the towers, resting on the big gear, and push a 6-long axle through the towers and the gear.
7. Push a knob wheel onto each end of the top axle — these are the propellers. Lock each one with a yellow half bush on the very end.
8. Push on the four wheels with their hubs centered 4.75 modules from the chassis center. Keep the rear tyres clear of the upper propeller axle and its bushes.

Play time

Push the car across the floor and watch the propellers blur. Turn a back wheel exactly once by hand and count how many times a propeller spins (it should be 3!).

Real-world inspiration

Classic push-along gear toys and propeller pull-toys; LEGO Education Simple Machines gear lessons — https://education.lego.com/en-us/lessons/sm/gears/