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How they steer › 03 OF 04

Mecanum wheelsWheels that slide

Four wheels, four motors, rollers at 45°. Mix the four right and the car drives, spins on the spot, or slides sideways without turning.

  • 4 motors
  • Ports S0–S3
  • gm0 mix
  • 7 test steps

No. 01 · Wukong mecanum racer

How it steers

A mecanum wheel turning forward pushes at 45°, across the rollers you see from above. With all four wheels forward the sideways parts cancel and the car drives straight; turn the diagonal pairs against each other and the forward parts cancel instead: it slides.

FIG. 1 · Slide right: each wheel pushes at 45°, and the four pushes add up sideways.

Three moves

Seen from above, front up. Bright wheels drive forward, dark ones back; the numbers are each wheel's power.

TEST MOVE 5+100+100+100+100
ForwardAll four wheels forward.
TEST MOVE 6+100−100−100+100
Slide rightLeft front and right rear forward, right front and left rear back.
TEST MOVE 7+100−100+100−100
Turn rightBoth left wheels forward, both right wheels back.

Telemetry: the mix

LF = forward + slide + turn
RF = forward − slide − turn
LR = forward − slide + turn
RR = forward + slide − turn
  • Forward, slide and turn come from the phone's two sticks; right is plus.
  • The same mix as gm0.org's mecanum drive.
  • Slide gets 10 % more: the rollers lose a little of every slide.
  • Over full power, all four slow down together, so the car keeps its line.

The machines

01Wukong · S0 to S3

Wukong mecanum racer

ElecFreaks Wonder Rugged Kit: four 360° servos.

3D model and steps →

Pit board: boards and programs

BoardMotorsProgram for the phoneWiring
ElecFreaks Wukong4 servos: S0 left front, S1 left rear, S2 right front, S3 right rearElecfreak Wukong Mecanum Car (Bluetooth)drawing
LEGO Technic Hub, SPIKE Prime hub, BuWizz 3.0 Pronext four motors, on four portsAll the boards

Pit check before the race

Lift the car off the table and tap Test motors on the phone. The car shows each step's number.

  1. 1–4Each wheel forward, then back
  2. 5Forward
  3. 6Slide right
  4. 7Turn right

A wheel turns the wrong way in 6 but the right way in 5? Two motors are in each other's ports: swap the plugs. Which motor is which?

Drive and test

  • Phone joystick: stick 1 drives and turns, stick 2 slides sideways. The picture under the sticks shows each wheel's power as you drive.

Other ways to steer

01Tracks02Steered wheels04Legs

All the boards