🏆 RC Racer: step-by-step build

A real remote-control car: motor drive, differential, servo steering and headlights.

This is it — the big one! Everything you learned comes together in one car. The L motor drives the back wheels through a corner gear and a differential, so the car corners smoothly. The Servo motor turns the pinion on the steering rack, just like the steering wheel did on the Go-Kart — but now the remote does it. Build the steering module, the drivetrain and the chassis separately like a real car factory, then put them together.

• Level 5 of 5 (a big challenge)
• About 75 minutes
• 38 steps, 108 parts
• Powered by: Multi-motor
• Series: Starter Builds

What you will learn

• Mounting a Motor: A motor must be pinned tight, or it spins itself instead of your wheels.
• Remote Control: Invisible light carries your commands to the model.
• Plugging In: Power Functions: Battery box → (switch or receiver) → motor. Plugs stack like bricks.
• The Differential: Lets the two driven wheels spin at different speeds in a turn.
• Rack & Pinion Steering: A gear rolling on a straight rack slides it sideways.
• Steering: Turning the front wheels makes a car follow a curve.
• Bevel Gears: Around the Corner: Slanted gears send spinning power around a corner.
• Drive Train: The chain of parts that carries power from the motor to the wheels.
• Electric Circuits: Electricity flows from the battery, through the motor, and back.
• Triangles Are Strong: A triangle cannot be squished — a square can.

Build these first

• 🏎️ 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)
• 🔋 Motor Buggy: Your first car that drives by itself — with a forwards/backwards switch and headlights! (level 3 of 5, about 30 minutes, 20 steps)
• 🪖 RC Tank: Two motors, two tracks, one remote. Spin on the spot and climb over anything! (level 4 of 5, about 60 minutes, 27 steps)

Parts you need

• 2 × Beam 15
• 36 × Black pin (grippy)
• 2 × L-beam 3×5
• 3 × Double cross block
• 6 × Bush
• 3 × Axle 7
• 2 × Axle 5
• 1 × Differential
• 1 × L motor
• 6 × Beam 7
• 4 × Beam 3
• 1 × Axle 2
• 7 × Half bush
• 1 × Corner gear (12 teeth)
• 4 × Big tyre wheel
• 2 × Beam 9
• 4 × Grey pin (smooth)
• 2 × Steering arm
• 4 × Axle 3
• 1 × Gear rack
• 2 × Cross block
• 1 × LED lights
• 1 × Servo motor
• 1 × Tiny gear (8 teeth)
• 1 × AA battery box
• 4 × Blue long pin
• 1 × IR receiver
• 2 × Beam 5
• 2 × Axle 6
• 1 × Speed remote

Steps

1. Stand a 15-hole beam on its edge — the left side of the chassis.
2. Push black pins into its 6th and 8th holes and press an L-beam post onto them, on the outside: the short leg along the beam, the long leg standing up at the 8th hole.
3. Hold a double cross block on the inside at holes 1–3, with a bush between it and the beam at hole 3. Push a 7-long axle through the 1st hole and a 5-long axle through the 3rd hole (and the bush), into the block — the long one sticks out a bit.
4. Slide a bush onto the 5-long axle against the block, then slide the right 15-hole beam onto the two axles. Front sockets: slide a double cross block onto each end of the long front axle, so its middle hole points up and down.
5. Give the right beam the same L-beam post with two black pins.
6. Put the differential between the back ends of the beams and push a 7-long axle through the last hole of each beam into it.
7. L motor cradle: take the L motor, its output pointing to the back.
8. Push 4 black pins into the motor's upper side holes — front and back, on both sides.
9. Press a 7-hole beam onto the pins on each side. Now the motor has a cradle.
10. Left battery post: push a black pin into the 10th hole of the left chassis beam and stand a 7-hole beam up on it. Lay a 3-hole brace beam on the outside from the L-beam post to the battery post, and push a black pin through its first hole into the 3rd hole of the L-beam post.
11. Pin the brace's last hole to the battery post's 3rd hole. Then the right battery post: a black pin in the 10th hole of the right chassis beam and a 7-hole beam standing on it.
12. The same brace on the right side: a 3-hole beam and two black pins.
13. Push a short red axle into the motor's output, slide a half bush on and then the corner gear. The half bush stops the gear sliding back against the motor.
14. Lower the motor cradle between the posts so the corner gear meshes with the differential. From the outside, push a black pin through the 2nd hole of each L-beam post and of each battery post into the cradle beams.
15. Two bushes on each back axle…
16. …and the big back wheels.
17. Steering module: lay a 9-hole beam flat and push a grey pin up through each end.
18. Put a steering arm on each pin.
19. Short axles and the big front wheels.
20. Grey pins in the arm ends, then the red tie rod on top.
21. Lay the rack on the tie rod, teeth up.
22. Slide the steering module in under the front until the 2nd hole from each end of the flat beam sits under the middle hole of a double cross block. From below, push a black pin up through each of those holes into the block.
23. Headlight holders: hold a cross block in front of the flat beam, its free hole on top and pointing forwards. From the middle, push a 3-long axle through it into the front hole of the double cross block. The same on the other side.
24. Push the two LED headlights into the front holes of the cross blocks.
25. Servo cradle: take the Servo motor, its output pointing forwards.
26. Push 4 black pins into its side holes: the front and the back hole on each side, level with the output.
27. Press a 7-hole beam onto the pins on each side.
28. Push a 5-long axle right through the servo's output. On its front end slide a half bush, the tiny pinion gear and another half bush, so the pinion can't slide along.
29. Braces: stand a 3-hole beam up just in front of each L-beam post, on the outside, and pin its bottom hole to the motor cradle beam with a black pin.
30. Lower the servo cradle between the posts and braces so the pinion sits right on the rack. From the outside, push a black pin through the 4th hole of each L-beam post and the top hole of each brace into the servo beams.
31. Lower the AA battery box between the tops of the battery posts, its front ear against them. From the outside, push blue long pins through the 6th hole of each post and the 7th hole of the left post into the front ear.
32. One more blue long pin through the 7th hole of the right post.
33. Push two black pins into the top holes on the front of the battery box and press the IR receiver's back holes onto them, dome facing the box. Plug the L motor into the red side and the servo into the blue side.
34. Rear wing: push two black pins into the lowest two holes of the back ear on the left, and press a 5-hole beam onto them, standing up.
35. The same on the right side of the back ear.
36. Push a 6-long axle through the 3rd holes: beam, ear, beam. Slide a half bush on each end so it can't fall out.
37. Push a second 6-long axle through the top holes and lock it with half bushes too.
38. Take the remote: red dial drives, blue dial steers!

Play time

Set up a race track with cups as cones. Drive a figure-eight! Watch the back wheels in the turns — the differential lets them spin at different speeds.

Build next

• 🤖 Robot Arm with Servo Claw: Swing, lift and grab! Three motors and a remote turn you into a factory robot operator. (level 4 of 5, about 60 minutes, 30 steps)
• 🧭 South-Pointing Chariot: Push it anywhere — the pointer keeps pointing the same way. No magnets, just gears! (level 5 of 5, about 75 minutes, 34 steps)