Make a cardboard car
Build a small car you can push, then change the wheels, body, or steering to suit your own idea.
About this project
Two rods run through straws taped under the car. Each rod is an axle: it holds a pair of wheels. The axles and wheels turn together while the straws stay still. Once this base rolls, you can give it a body of your own.
Supplies
Materials & tools
- A piece of light cardboard, roughly 10 × 15 cm, for the body
- Two straight drinking-straw pieces, each about 8 cm long
- Two blunt wooden axle rods, about 16 cm long, that turn freely inside the straws
- Four cardboard circles, about 5 cm across, for wheels. Each needs a small hole in its middle that grips a rod. Bottle caps with safely prepared holes are another option.
- Tape and suitable scissors; a pencil and ruler can help with marking
Before you start
- Clear a flat floor or table. Use smooth wooden rods with blunt ends. Ask someone who knows the tools to prepare the small holes in your wheels. Do not push a sharp tool toward a hand holding a wheel.
- Keep small wheels, cut rod ends, and tape scraps away from children who put things in their mouths. Use card thin enough to cut comfortably with your scissors.
Instructions
Put the straws under the body
Lay the cardboard flat with its 15 cm length pointing away from you. This face will be the underside. Lay a straw across its 10 cm width, about 3 cm from the near end. Put the second straw across the far end in the same way. Keep both straws pointing the same way, like the rungs of a ladder.
Tape the straws and fit the axles
Put two small pieces of tape across each straw to hold it to the card. Leave the straw ends open and do not squash the tubes. Slide a wooden rod through each straw. These are the axles. Turn them with your fingers. They should turn without moving the straws. Free any tight or flattened spot before adding wheels.
Attach the wheels
Push one wheel onto each end of each axle. Leave a small gap between every wheel and the end of its straw. Hold an axle and turn a wheel: the wheel should grip the axle, so both turn together. If a card wheel slips, use small tape pieces from the rod onto the wheel’s face. Keep that tape away from the straw. A hole near the middle helps the wheel roll without a big wobble.
Underneath the car: tape holds the straw sleeves to the cardboard. The axles turn inside the sleeves; the wheels turn with the axles. Try rolling it
Turn the car right side up and give it a gentle push on a flat surface. If it stops quickly, lift it and turn one wheel slowly. The axle and wheel at the other end should turn too. Look for a wheel rubbing against the cardboard, straw, or tape. Move it a little farther out if needed.
Make it your vehicle
Add a cab, a creature, a cargo bed, or another shape if you want. Roll it again as you build. A new piece might touch a wheel or make one end too heavy. You can keep a plain rolling base or see what else it becomes.
Troubleshooting
- The wheels turn in your hand but not on the floor.
- Look underneath for a wheel touching the body, tape caught in a straw, or a bent axle. Leave a gap beside each wheel. Try taking off a heavy piece of the body.
- A wheel falls off or spins without its axle.
- The hole may be too loose. Use small tape pieces from the axle onto the wheel’s face. If the hole has torn wide, make another wheel. Do not put tape where the axle needs to turn inside the straw.
- It turns when you wanted it to go straight.
- Look down at both axles. Are they pointing the same way? Check whether one wheel is larger or has its hole away from the middle. You can fix the turn or make it part of your vehicle.
Where to take it next
- Try a different body shape, or make a body from folded card instead of a flat sheet.
- Compare your own wheel designs. Large, small, round, and uneven wheels produce different journeys.
- Try a short rolled-paper tube in place of one straw. Check that it holds its shape and leaves enough room for the axle to turn.
A closer look
The straws hold the axles in place but leave them free to turn. If a wheel, axle, or bit of tape rubs against another part, the car slows down. Watching one wheel turn can show you where the motion stops. Pushing harder will not free a wheel that is stuck.
What happens if…
- What is rubbing when a wheel stops?
- What would make this into the vehicle you imagined?
- Can you make it turn deliberately?
What it needs to do
A function can have more than one solution. These options belong to this example; try alternatives thoughtfully.
structure
A lightweight body with room for two axle supports. A folded shape may be stiffer than a flat scrap.
bearing
For a small hand-pushed model only. A sleeve must fit the axle loosely enough to turn; paper may crush or add friction. Compare your actual results.
axle
Use blunt, smooth rods. A rolled paper rod is a proposed experiment for very light loads; check stiffness and fit.
wheel
Use cardboard circles or caps with holes already prepared by an experienced helper. Centering and attachment affect rolling.
cutting
For paper and thin card only. Choose prepared shapes if the card is too thick to cut comfortably.