Building a toy car is a good way to pass the time, and once you're done, the next step is getting your creation to move. There are a wide variety of ways to power the car, and many of them involve ordinary household objects. Ideally, you will install these various motors and engines on a simple base with four wheels. Any cosmetic additions you want to make to the car can be done after you've literally got its wheels in motion.
Bend the short part of the bendy straw upward and insert it into the balloon.
Wrap the elastic band around the mouth of the balloon. It should be tight enough to seal the balloon against the straw, but not so tight as to crush the straw. Test the seal by inflating the balloon.
Tape or glue the straw rig to your car so the end of the straw hangs off the back of the car by about an inch.
Power the car, inflate the balloon and hold the end of the straw. Place the car on the floor and release. The car will roll as the balloon deflates.
Flip one arm of the binder clip to the open position and squeeze that arm to remove it.
Slip the elastic band around the arm, and reattach the arm to the clip.
Clip the binder clip to the front-center of your car and flip the arms to the closed position.
Cut a 1-inch square notch in the back of the car, exposing part of the rear axle.
Connect the elastic band to the rear axle by taping and stapling them together, or attach a gear to the center of the rear axle.
Power the car by rolling it backward, then releasing it. If you are using a gear, the elastic will slip off the gear between uses. Reconnect it before rolling the car forward again.
Attach a pulley or gear to the drive axle. You can use the front or rear, but most toy vehicles are powered on the rear axle.
Attach another gear or pulley to the electric motor.
Install the motor on the car base. If you're using a pulley system, connect it near enough to the pulleys to attach them both by an elastic band. If you're using gears, install the motor so the teeth mesh.
Wire the batteries or solar cell to the motor to create a closed circuit loop. The contacts must touch exposed wire. Both contacts of the motor should be wired to the power source. If you are installing a switch, connect it now by connecting two wires to the switch, and then to the motor and power source.
Test the motor. The wheels should turn as soon as the power is connected to the motor--unless you have installed a switch and it's off. If the car rolls backward when the power is on, switch the wires on the motor.