How to build a self propelled model car
A homemade toy car is a lot of fun, especially because there are any number of ways to power such a vehicle. It could be powered by wind, by an elastic band or by electricity. Many things you already have in your house could become the motor for your self-propelled toy car. All you have to do is use your imagination and start building a toy car.
Draw the car base on your cardboard, wood or foam board. You can make the base look however you want, but you should make it at least three inches by five inches in size. Note the front and back for your reference.
Draw a rectangular notch on the back of the vehicle. Make it in the centre of the back line, about 1-1/2-inches into the middle of the car, by 1/2-inch wide.
Cut out the vehicle and the notch.
Turn the vehicle over and place the straws or axle holders on top of the vehicle. You should put one set on the front and one on the back, crossing the notch. If you're using eye hooks in wood, use two per axle. Make sure the axles are parallel to each other and at right angles to the notch.
Glue and tape or screw the axle holders in place. If you're using a straw, cut the shape of the notch out of the straw.
Glue a wheel onto the end of an axle. Make two of these pieces.
Cut the bendy straw to about four inches in length, leaving the bendy part intact.
Insert the straw into the balloon, with the bendy part sticking out.
Wrap the balloon nozzle with an elastic band. Make sure the band forms an airtight seal around the straw but doesn't crush it.
Tape the straw in place, sticking the end of it through the notch in the back of the car.
Insert the axles into the holders on the base of the vehicle and glue the remaining wheels onto the exposed axle. Test that the wheels roll smoothly.
Inflate the balloon, and release the straw to send the car flying away.
Insert an axle into the front set of axle holders and glue a wheel onto the exposed axle. Test that the wheels and axles roll smoothly.
Slide the other axle about halfway through the rear axle holder. Slide a gear wheel inside the notch, on the end of that axle. Glue the remaining wheel into place.
Glue the gear in place on the axle.
Open a binder clip and squeeze one of the arms to unhinge it from the clip. Loop the elastic band around that arm, then put the binder clip back together.
Attach the binder clip to the front of the vehicle in line with the notch on the back. Flatten the arms against the base of the car.
Loop the other end of the elastic around the one of the gear's teeth, and wind the axle backwards to wind the car up. Release the axle to send the car rolling.
Slip an axle into the front set of axle holders and glue wheels into place. Spin the wheels to make sure they roll smoothly.
Slip the other axle halfway through the rear axle holder.
Place a gear inside the notch. If you're using a pulley wheel and elastic band, place both inside the notch.
Push the axle through the gear or pulley wheel and elastic band, and into the other side of the axle holder. Glue the other wheel in place and test that the wheels roll smoothly.
Glue the pulley wheel or gear onto the axle. If you have an elastic band there, don't get any glue on the rubber band 1.
Glue the other gear or pulley onto the motor's axle.
Connect one wire to each terminal on the motor, one to the positive (+) and the other to the negative (-) terminal.
Glue or tape the motor onto the car base. If you have a set of gears, make sure the teeth of the gear mesh and are in line with each other. If you're using pulley wheels, loop the elastic band around the motor wheel and place the motor on the vehicle so that the elastic band is straight and taut.
Tape the positive wire (+) from the motor to the positive terminal on the battery or solar cell. Repeat with the negative wire (-). As soon as the negative wire touches the terminal, the motor should start moving.