Build yours at home
Two-motor cardboard car
What we're doing
Build a cardboard car with a motor on each side. Each motor has its own battery and switch. Both on: it drives straight. One on: it turns, like a tank.
About 45 minutes.
Goes with these lessons
Get these parts
- Two yellow TT gear motors with wheels (often sold together) (electronics shop)
- Two 2×AA battery holders with switches (electronics shop or online)
- A shoebox lid or stiff cardboard, and tape (household)
- A paper clip, for a front skid (household)
- Short insulated wires (electronics shop), only if the motors have no wires
Fill each holder with the matching number of AA batteries (household).
Keep it safe
Battery power only, never household power. Use AA packs matched to the parts, not a 9V battery. A grown-up connects and disconnects the pack. Stop immediately if any part warms. Never join the pack's two metal ends: the wires can get hot. Coin cells stay with grown-ups, locked away. CPSC warns a swallowed button or coin cell can burn through a child's throat in about two hours; suspected swallowing needs emergency medical care immediately.
Keep fingers and hair away from the wheels. Don't hold a wheel still while its motor is on.
Steps
- 1
Tape one motor under each side of the cardboard, at the back, with the shafts pointing out. Push a wheel onto each shaft.
- 2
Bend the paper clip into a small skid and tape it under the front, so the car rests on it. Tape over its sharp ends.
- 3
Tape a battery holder on top above each motor, switches off. A grown-up twists each motor's two wires onto its own holder's two wires and tapes over the joins. If the motors have no wires, a grown-up twists short wires through their metal tabs first.
- 4
Lift the car and switch both holders on. Both wheels should spin forward. If one spins backward, switch it off and swap that motor's two wires.
- 5
Put the car on the floor and switch both on. It drives straight. Switch both off.
- 6
Switch on only the left motor. The car turns right. Now only the right motor: it turns left.
- 7
Switch off and take the batteries out.
Talk while you build
- Which way does the car go when both wheels push?
- Which way does it turn when only one wheel pushes?
Spot it at home
- Wheelchairs, robot vacuums, a shopping trolley pushed harder on one side, rowing with one oar.
How does a wheelchair turn without a steering wheel?