Building a robot chassis

Learn

What you’ll learn

• Which materials suit a first chassis
• Where to put motors, batteries, boards and sensors
• How to make a robot easy to debug and repair

Materials

Material	Pros	Cons
Cardboard	Free, cut with scissors, perfect for prototypes	Weak when wet, wears out
Kit acrylic plates	Pre-drilled, neat	Brittle: cracks if over-tightened
Plywood / MDF	Strong, easy to drill	Heavier
LEGO / Meccano	Fast to change	Can flex; limited motor options
3D-printed	Exactly the shape you want	Needs a printer and design time

Prototype in cardboard first, then build the final version.

Layout

       front
  ┌──────────────┐
  │  sensors →   │  line sensors low at the front, distance sensor facing forward
  │  [Arduino]   │  board on top, USB port reachable
  │  [battery]   │  battery low, between the wheels
  O  motors      O  wheels at the sides
  │      ◦       │  caster at the back
  └──────────────┘

• Wheels at the sides and level with each other; caster at the other end.
• Battery low and central (see structures and stability).
• Line sensors 3–10 mm above the floor (check your module’s datasheet).
• Distance sensor at the front with a clear view.
• Switch and USB port easy to reach.

Fixings and wiring

• Use M3 screws, nuts and spacers (standoffs): the standard size for kits.
• Don’t over-tighten into acrylic.
• Use cable ties and keep wires short; label them with tape if needed.
• Use connectors (Dupont or screw terminals) so parts can be swapped without soldering.

Examples

Example: a 2WD kit build order

1. Attach the two TT gear motors under the bottom plate with their brackets.
2. Fit the wheels; spin them by hand to check they don’t rub.
3. Screw the caster at the back.
4. Mount the battery holder between the motors.
5. Add standoffs and the top plate; mount the Arduino and motor driver on top.
6. Mount the line sensors under the front and the ultrasonic sensor at the front edge.
7. Wire, tie cables, then test each part on its own before writing the full program.

Example: a debugging-friendly robot

The power switch is on top, the Arduino’s USB port faces the back edge, every sensor plugs into a labelled header, and the motor driver’s screw terminals face outwards. When something fails, you can measure or swap any part in under a minute.

Practice

Sketch a layoutEasy

Draw a top view of a two-wheeled robot showing where the wheels, caster, battery, Arduino and sensors go.

Cardboard prototypeMedium

Build a cardboard chassis that holds two motors (or two bottle caps as stand-ins), a 4×AA battery pack and an Arduino-sized card. Push it across the table: does it stay straight and level?

Fix the wobbleHard

Your robot drifts left and the caster keeps catching on the carpet. List three likely causes and fixes. Wheels not parallel (re-align the motor brackets); one motor weaker or wired with less voltage (swap motors to test, or trim speeds in code); caster too small or too low (use a bigger ball caster or raise it so the chassis sits level).

Quick check

1. What’s the best material for a quick first prototype?

AluminiumCardboardCarbon fibreGlass

2. Which screw size is standard in most robot kits?

M3M10M1M8

3. Why mount the battery low and between the wheels?

It charges fasterIt keeps the centre of gravity low and stableIt’s closer to the sensorsIt makes the robot faster

Check my answers