My name is Noah and I am a sixth grade student in Massachusetts. My school assignment was to build and test an electric car. My electric car could only be 18 cm long and 6 and 1/2 cm wide. I was given a 3V motor, power wire, and my power source could not exceed 3V.
Before beginning I learned about electricity. A circuit is a path that starts and stops at the same place. Voltage is the difference in charge between two points. Current is the rate at which the charge is flowing. Resistance is a material's tendency to resist the flow of charge. This is a DC current car and the current flows in only one direction.
Step 1: Gathering Materials
You will need the following materials to build your car: Batteries, a Bottle Cap, Power Wire, a 3V DC Motor, 2 AA Batteries, 2 Paper Clips, at least a 4 cm by 18 cm of Balsa Wood, 2 Wheels, an axle and something to boost the axle (I used legos for this). *Modifications were later made to this design and the new components are listed toward the end of this instructable.
Cut a 4 cm by 18 cm piece of balsa wood and drill two holes. This is where your wires will go up to the top of your car.
Now secure your rear wheels either with legos, a straw; it is 100% preference. You could do whatever you want. They should be able to spin freely.
Your motor should have a pin on it. Find a drill bit that is slightly smaller so the cap is tightly fit on the motor pin. You might want to super glue it on the pin.
Step 5: On to the Top!
Tape the batteries together as shown in the picture. Make sure the wires are connected to the battery before you tape it. A secure connection is important. (This is where I ran into trouble and modified this later)
Twist the wire from the battery around the bronze contacts on the motor
Secure the motor and attached a rubber band for traction
Add a switch with a paper clip and a thumbtack. Wrap the wire around the metal part of the tack. When the tack is pushed in to the other side of the paperclip the motor will go!
Step 9: Testing
I was able to have the wheel spinning while held in the air. When I tried to put it on the ground the wheel would not spin. In the end the battery connections were inconsistent, which made the car inconsistent both in the air and on the ground. Modifications were necessary.
Step 10: Modifications
My first modification was a flashlight as a battery holder instead of batteries taped to the chassis. I took apart the flashlight so that I could get to the two points where the flashlight bulb is connected to the batteries. The positive (red) wire was connected where the bulb base was by pushing the wire through the back of the socket. The black wire was wedged against the metal collar that the bulb sits against. I then carefully screwed the head of the flashlight back onto the socket without the lens installed so that the wires can leave and go to the motor. Finally, I screwed the body of the flashlight back onto its head. Now, turning on the switch of the flashlight, turns on the power to the motor. I used electrical tape to attach the body of the flashlight to the base of the car.
My second modification was to make the wheels smaller to reduce friction.
Step 11: Testing
After modifications the rubber band that was on the wheel for traction slowed the car down. I removed it and testing went much smoother with the fastest time being 10 ft in 4.24 seconds.