🔥 Big-Wheel Dragster: step-by-step build

Giant back wheels, tiny front wheels — the same spring pushes this car much further!

Drag racers have huge back wheels and a long, low nose. Yours does too! The spring engine sits right on the big back axle. A big wheel rolls much further in one turn than a small one — so the same spring pushes this dragster almost twice as far as the little Pull-back Racer. Wheel size works just like a gear!

Level 2 of 5 (easy)
About 22 minutes
10 steps, 30 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.
Axles & Wheels: A wheel on an axle turns dragging into rolling.

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)

Parts you need

1 × Pull-back motor
1 × Axle 12
14 × Black pin (grippy)
2 × Open frame 5×7
2 × Beam 15
2 × Big tyre wheel
1 × Axle 10
2 × Small white wheel
2 × L-beam 3×5
1 × Axle 9
2 × Half bush

Steps

Take the pull-back motor, long body pointing forward and tipped a little nose-down. Push a 12-long axle through the cross hole at the bottom.
Push a black pin half-way into the front one of the two top holes of the motor, and one into the first and the last hole of the bottom row, on this side. Press a black 5×7 frame onto the three pins.
Same on the other side: three black pins half-way into the motor, then the second frame.
Push two black pins into the outside of each frame's bottom bar: the 3rd hole and the last hole.
Press a red 15-hole beam onto each pair of pins, sticking out far in front — they slope down to the nose like a real dragster.
Push the two giant wheels onto the motor axle.
Push a 10-long axle through the last holes of the red beams and add the two small front wheels.
Push two black pins into the outside of each frame's top bar, in the last two holes.
Press an L-beam onto each pair, long leg standing straight up.
Slide a 9-long axle through the tops — the wing — and lock it with half bushes.

Play time

Pull the dragster back exactly one hand-length and let go. Mark where it stops. Do the same with the Pull-back Racer — which one wins? Why?

Real-world inspiration

Top-fuel dragsters; Rebrickable "Top Fuel Pull Back Tractor" MOC-13855 — https://rebrickable.com/mocs/MOC-13855/Anto/top-fuel-pull-back-tractor/