Teachers TryScience

Cars are intrinsically exciting to many students. Solar powered cars are even more so. Very little is required to motivate students to engage in this project. Before trying this lesson with students, you should build your own solar car so that you are comfortable with the activity. The video below provides a practical how-to, but be sure to read the instructions thoroughly.

• Solar Car How-to video

Introductory and Brainstorming Activities

This type of open-ended design process may be new to you and your students. As a way to prepare your class to design and construct a solar car, you may want to introduce the lesson by discussing solar car competitions in which college students participate and provide some statistics about those solar cars and the challenges the students faced in building them. (See Further Information section below.)

Then it's helpful to engage students in a brainstorming activity. Before beginning, divide students into groups of 4-6. You may find the video below helpful:

• Value of Group Work Video

Using a worksheet or recording in a notebook, ask students to list the parts of a solar car. What are the basic things you need to make a car run? After they have created a list of parts, ask them to work together to look at each component individually and decide how they will create it using the materials available to them. How will the pieces fit together? It is important to give them time to think on their own, but you can facilitate this process as you see fit.

Building the Solar Car

Once they have really thought about the design of their car, they are ready to begin building. Students could construct their cars in the order below, but remember, this is just one way to create a car. You should not give this procedure to the students, but instead, use your version of the car to guide and encourage students to create their own feasible design.

1. If the wheels do not already have a hole in them, use a knife or nail to poke a hole in the center of all four wheels. The holes should be small enough that the wooden skewer axles fit snugly.
2. Take the juice carton that you will use for your chassis (car body) and cut it in half the long way. You will only use one half of the carton so discard the second half.
3. Cut a rectangular hole in the chassis that is large enough to fit the rubber bead and allow the bead to rotate. It should be no larger than 3.25 cm long and 2.5 cm wide.
4. Attach the axles onto your chassis. For the back axle, tape or glue a straw to the underside of the chassis and put the wooden skewer through the straw. For the front axle, cut a straw in half. Place the halves so that they are lined up with the rectangular hole you cut in step 3 and tape one half to either side of the hole. Put the wooden skewer through one straw and then place the foam bead on the skewer so that it fits snugly into the rectangular hole. Put a rubber band around the bead and then put the skewer through the other straw.
5. You will now place a wooden block, piece of folded carboard, or something similar along the long side of the rectangular hole to prop the motor up.The motor should be far enough from the axle that the rubber band is just taut when attached to the motor. After you have placed the block and confirmed that the band will be taut, glue the block in place. Once the glue has dried, position the motor on top of the block. The tip of the motor should be facing the hole. Once you have positioned the motor, glue it in place.
6. Attach the rubber band to the tip motor and place a piece of clay, glue, or eraser to keep the rubber band from slipping off. The band should still be able to move freely.
7. Place the wheels on the axles you have created. If the holes are too large, you can use glue to seal the holes. Wind rubber bands around the front wheels to act as tires.
8. Attach the solar panel to the motor using the wires attached to the panel. If you wish, you can place tape on the wires to secure the connection between panel and motor. You can prop the panel up to change the angle using another block or folded cardboard.
9. Once you have created your car, you can begin testing. Place the car outside in the sun or under a bright light. Make changes to your design as needed.
10. The activity culminates in a race!

Consider the Following

• Using the materials that you provide them, students should be given the freedom to choose their own designs.
• Photovoltaic cells do not deliver nearly as much power to a motor as a battery does. Keep your solar cars light.
• You may wish to test that the solar panel and motor work before adding them to your car.
• You should judge where your motor should go BEFORE you actually add it to the body.
• Make sure your panels point towards the sun and that they are steady. In order to maximize the amount of sunlight hitting the panel, the sunlight should be striking the surface of the solar panel at about 90 degrees.

Troubleshooting Tips

• If engineering problems arise, remember to allow students to troubleshoot for themselves. Once they have had some time to discuss and problem-solve, you should then offer advice.
• If the car does not immediately move in the presence of the sun or a light, try lifting up the front half of the car for a few seconds. This allows the car to build momentum.
• If the rubber band slips off the motor you may have to reposition the motor so that it is farther from the band. Remember, the band should be taut. You could also try placing something like glue or clay on the tip of the motor, but it should not interfere with the movement of the band.
• The car will not move very fast, but if you are using an artificial light, you may have to follow the car with the light to keep it moving. Keep this in mind if you are using a light that is plugged into a power source.
• If the car has difficulty moving, try putting it on a smoother surface.
• If the car wobbles, be sure that the wheels are as centered and secure as possible.

Safety Notes

• A utility knife may be needed to bore out the holes for the wheels. Only instructors should do this. A nail just smaller than the axle may also be used to bore out the holes if necessary.
• Use of the hot glue gun should be supervised. You could create a station in which students bring their car to you or another adult when they are ready for hot glue.
• Glue should not be ingested.
• Use of utility knives should be supervised.