🚀 Launch-Lock Racer: step-by-step build

Wind it up, and a little catch holds the spring tight until YOU press the launch button!

Three… two… one… LAUNCH! Pull this racer backwards and you hear click-click-click: a little catch, called a pawl, drops into the teeth of a gear. The catch lets the gear turn backwards while you wind the spring, but blocks it going forwards — so the car waits, full of energy. Set the steering with the knob, press the launch button, and the pawl lifts: ZOOM! You will build the front axle as a module first, bolt it on the front, and then add the steering.

  • Level 3 of 5 (medium)
  • About 40 minutes
  • 21 steps, 64 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.
  • Ratchet & Pawl: Lets something turn one way but not the other.
  • Steering: Turning the front wheels makes a car follow a curve.
  • Rack & Pinion Steering: A gear rolling on a straight rack slides it sideways.
  • Levers: A bar on a pivot multiplies your push.

Build these first

  • Pull-back Racer🏁 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)
  • 🏎️ Steering Go-Kart: Turn the steering wheel and the front wheels really turn — just like a real car. (level 3 of 5, about 30 minutes, 25 steps)

Parts you need

  • 1 × Pull-back motor
  • 1 × Axle 12
  • 22 × Black pin (grippy)
  • 2 × Open frame 5×7
  • 2 × Beam 15
  • 1 × Medium gear (24 teeth)
  • 4 × Yellow-hub wheel
  • 5 × Grey pin (smooth)
  • 1 × Thin beam 4
  • 5 × Red axle-pin
  • 2 × L-beam 3×5
  • 4 × Long pin-axle block
  • 1 × Beam 7
  • 2 × Beam 9
  • 2 × Steering arm
  • 2 × Axle 3
  • 1 × Gear rack
  • 1 × Axle 5
  • 3 × Half bush
  • 1 × Tiny gear (8 teeth)
  • 1 × Knob wheel

Steps

  1. Take the pull-back motor, long body pointing forwards, and push a 12-long axle through the cross hole at the bottom — one hole more sticking out on the left.
  2. Push a black pin half-way into the front one of the motor's two top holes, and into the first and last hole of its bottom row, on this side. Press a black 5×7 frame onto the three pins.
  3. Same on the other side: three black pins half-way in, then the second frame.
  4. Push black pins into the outside of both frames, the 2nd hole up at the back and at the front.
  5. Press a red 15-hole beam onto each pair of pins. The motor axle goes through their last holes.
  6. Put the 24-tooth ratchet gear on the left end of the motor axle, then push on the two back wheels.
  7. Push a smooth grey pin into the 11th hole of the left rail, from the outside, and hang the black pawl on it by its 2nd hole, so its tip rests on the ratchet gear’s teeth.
  8. Push a red axle-pin into the pawl’s back hole: the LAUNCH button.
  9. Push black pins into the 6th and 8th holes of the left rail, on the outside, and press an L-beam post onto them: foot along the rail, long leg standing up at the front.
  10. Same on the right rail: two pins and the second post.
  11. Push two black pins into each post, on the inside: the 3rd hole and the top hole.
  12. Press a long pin-axle block, standing up, onto each pair of pins.
  13. Push a red axle-pin into the middle hole of each block, pointing forwards, and press the red 7-hole dashboard beam onto both.
  14. Front axle module: lay a 9-hole beam flat and push a smooth grey pin up through each end hole.
  15. Push a red axle-pin up into the 3rd and 7th holes (axle end up) and put a long pin-axle block on each, lying along the car.
  16. Slide the module in under the front of the racer, blocks between the rails. Push black pins through the 1st and 3rd holes of both rails into the blocks.
  17. Put a steering arm on each grey pin (smooth, so the arms can swing), and slide a short axle into each arm.
  18. Push on the two front wheels.
  19. Grey pins in the arm tips, and the red tie rod on them. Push the tie rod sideways: both wheels steer together!
  20. Lay the gear rack on the tie rod, teeth up. Hold the pinion on the rack with a half bush behind it, and slide the 5-long steering column in from the back through the dashboard, the half bush and the pinion.
  21. Lock the pinion with a half bush on the front end of the column. Push a red knob wheel onto the back, right against the dashboard, and a half bush behind it.

Play time

Wind the racer up (click-click-click) and let go — it waits! Set the steering, then press the red button. Can you launch it through a doorway from 2 metres away?

Real-world inspiration

Rebrickable "Release mechanism for single pull-back motor" MOC-172692 — https://rebrickable.com/mocs/MOC-172692/sieclaprzemyslaw/release-mechanism-for-single-pull-back-motor/ ; ratchets — https://en.wikipedia.org/wiki/Ratchet_(device)