💨 Gear-Up Speeder: step-by-step build

The spring engine sits up high and turns a BIG gear, which spins the wheels faster!

Can we make a spring car go even faster? Let’s use gears! This time the spring engine does not sit on the wheels. It rides high up and turns a giant 40-tooth gear. The giant gear spins a 24-tooth gear on the back axle, so the wheels turn 1⅔ times for every turn of the spring. Faster wheels — but less push. Will it win the race, or run out of power? Test it!

• Level 2 of 5 (easy)
• About 25 minutes
• 11 steps, 26 parts
• Powered by: Pull-back
• Series: Gearbox & Drivetrain Cars

What you will learn

• Stored Energy: Energy can be saved up in a spring and let out later.
• Mounting a Motor: A motor must be pinned tight, or it spins itself instead of your wheels.
• Gear Ratio: Fast or Slow: A big gear turning a small gear makes it spin faster.
• Torque vs Speed: Slower gears are stronger gears.

Build these first

• 🏁 Pull-back Racer: Pull it back, let it go — ZOOM! A racer with a spring for an engine. (level 2 of 5, about 12 minutes, 10 steps)
• 🧪 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

• 1 × Pull-back motor
• 10 × Black pin (grippy)
• 2 × Open frame 5×7
• 2 × Open frame 5×11
• 2 × Axle 10
• 1 × Giant gear (40 teeth)
• 2 × Half bush
• 1 × Axle 12
• 1 × Medium gear (24 teeth)
• 4 × Yellow-hub wheel

Steps

1. Engine first! Take the pull-back motor, long body pointing forward. Push a black pin half-way into the front one of its two top holes and into the first and last hole of its bottom row, on this side.
2. Press a black 5×7 frame onto the three pins. Turn the motor over and push three black pins half-way into the same holes on the other side.
3. Press the second black frame on, then push two black pins into the outside of the first frame: the 2nd hole up at the back, and the same hole at the front.
4. Two more black pins in the same holes of the second frame.
5. Stand a white 5×11 frame up on its long side — the left wall.
6. Slide the engine cradle sideways onto the wall: its two pins go straight into the 2nd and 8th holes of the wall's top bar.
7. Press the second white wall onto the pins on the other side.
8. Push a 10-long axle through the top back corners and the motor, with the giant 40-tooth gear outside the left wall, a half bush on the end next to it, and a half bush on the right.
9. Push a 12-long back axle through the bottom back corners, with a 24-tooth gear under the giant one. Let it stick out one hole more on the gear side.
10. Push the two back wheels onto the back axle.
11. Push a 10-long front axle through the front corners and put the two front wheels on it.

Play time

Race the speeder against the Pull-back Racer on a smooth floor, then on carpet. Which wins where? Gearing up gives speed but costs pushing force.

Real-world inspiration

Rebrickable 42106 pull-back racer alternate — https://rebrickable.com/mocs/MOC-41395/Tomik/42106-pullback-racer/