🛵 Front-Drive Servo Trike: step-by-step build

One front wheel does everything: its own motor drives it and the Servo swings it round.

Forklifts and some delivery trikes steer with a single wheel that has its own motor. This trike does the same! Under the nose hangs a fork with the front wheel. The M motor rides on the fork and drives the wheel with two giant 40 gears. On top of the fork is a turntable, and right on top of that stands the Servo, pointing its output straight down into the turntable. When the Servo turns, the whole fork — wheel, motor and all — swings left or right. It can almost turn on the spot!

  • Level 4 of 5 (tricky)
  • About 50 minutes
  • 21 steps, 46 parts
  • Powered by: Motor
  • Series: Gearbox & Drivetrain Cars

What you will learn

  • Servo Motor: A motor that turns to an angle and holds it.
  • Turntables: A turntable lets a whole model spin round.
  • Remote Control: Invisible light carries your commands to the model.
  • Steering: Turning the front wheels makes a car follow a curve.
  • Drive Train: The chain of parts that carries power from the motor to the wheels.
  • Mounting a Motor: A motor must be pinned tight, or it spins itself instead of your wheels.
  • Plugging In: Power Functions: Battery box → (switch or receiver) → motor. Plugs stack like bricks.

Build these first

  • 🎮 First RC Car (Servo): Your first remote-control car: one dial drives, the other dial steers. (level 4 of 5, about 50 minutes, 27 steps)
  • 📡 Spinning Radar: A motor-driven radar dish that sweeps round and round on a turntable — with a blinking light. (level 3 of 5, about 25 minutes, 15 steps)

Parts you need

  • 2 × Beam 15
  • 10 × Blue long pin
  • 3 × Beam 7
  • 10 × Black pin (grippy)
  • 1 × Servo motor
  • 2 × Axle 3
  • 2 × Beam 9
  • 1 × L-beam 3×5
  • 1 × Axle 11
  • 3 × Yellow-hub wheel
  • 1 × Axle 6
  • 2 × Giant gear (40 teeth)
  • 2 × Half bush
  • 1 × M motor
  • 1 × Turntable
  • 1 × AA battery box
  • 1 × IR receiver
  • 1 × LED lights
  • 1 × Speed remote

Steps

  1. Stand a 15-hole beam on its edge — the right top rail.
  2. Push a blue long pin into its first hole so it sticks out 2 on the inside, and stand a 7-hole Servo post on it.
  3. Black pins in the 5th and 7th holes of the post and a blue long pin in the 3rd hole of the rail, all pointing inwards. Slide the Servo onto all four pins from the left side, orange output pointing straight DOWN.
  4. Push the same four pins into the Servo's left side: blue long pins in the two holes level with the rail, black pins in the two higher holes.
  5. Press the left Servo post onto the three pins in a column, then a 3-long axle up into the Servo's output.
  6. Press the left top rail onto the two long pins, level with the right rail.
  7. Left back leg: hold a 9-hole beam upright outside the left rail at hole 13 and push a blue long pin through it into the rail. Another blue long pin into hole 10 of the rail from the outside.
  8. A black pin in the leg's 2nd hole from the top, and press an L-beam 3×5 onto the three pins, short arm pointing down along the leg. Now the leg is braced and can't swing.
  9. Right back leg: a black pin in hole 13 of the right rail (outside) and a 9-hole leg hanging down from it.
  10. Push an 11-long axle through the bottom holes of both legs. It ties the right leg to the braced left leg.
  11. Push on the back wheels.
  12. Fork: stand a 7-hole beam up, push a 6-long axle through its bottom hole and slide the front wheel onto the inside.
  13. A giant 40 gear and a half bush on the outside end of the axle. Push black pins into the 5th and 7th holes of the fork leg, pointing inwards.
  14. Press the M motor onto the pins, above the wheel, output in the 6th hole. A 3-long axle into the output, another 40 gear on it and a half bush to hold the gear on.
  15. Put the turntable on top of the fork.
  16. Push the fork straight up under the Servo: the Servo's axle goes into the middle of the turntable.
  17. Take the AA battery box.
  18. Lower the box between the top rails and push a blue long pin through the rail into each of its 4 ear holes.
  19. Push black pins into holes 9 and 11 of the right rail from the outside, and press the IR receiver onto them, dome up.
  20. Push the LED lights into holes 2 and 4 of the right rail — side lights.
  21. Wiring: receiver cable onto the battery box. Fork motor → RED (A), Servo → BLUE (B). Grab the remote.

Play time

Turn the blue dial all the way and drive forwards with red: the trike spins round almost on the spot. Can you park it in a box just a little longer than itself?

Real-world inspiration

Front-wheel-drive delta tricycles and forklift drive-and-steer units. https://en.wikipedia.org/wiki/Forklift