Electric Car

Making an electric car is a mechanical engineering challenge often used as a competition for students from 5th grade to 8th grade.

An electric car is driven by a DC electric motor, powered by one or two batteries.  Transmission of force from the motor to the car axle is accomplished using two pulleys and one rubber band acting as a belt. A simple switch made of a paper clip is used to connect or disconnect the circuit. Wheels are made of larger pulleys with rubber rings as tires. The car chassis is mad of a plastic board, reinforced by wood blocks and eye screws that will also support the axles of the wheels.

Some students may prefer to buy all the parts separately and cut all the woods themselves and design their own car; however, most students and teachers prefer to get all the parts in a kit and make changes as they need.

With this project students can explore:

• A simple propulsion method
• Basic gluing techniques and design concepts
• Concept of stored chemical energy energy and converting it to mechanical energy
• A simple electric circuit

Items Needed:

Electric Car Kits usually come with parts, cut to size and ready to use. The picture bellow shows the materials you usually find in an Electric Car Kit from MiniScience. Kit includes at least 4 wooden parts and one plastic board, cut to size in addition to the 4 pulley wheels, 4 tire rings, battery holder, one transmission pulley, electric motor, rubber bands, motor mount, screws, brass paper clips  and eyelets.

Materials Checklist: Before using the kit please verify the content with the parts in this picture. In addition to the kit parts you will need: White glue or wood glue Grip Pins Sand Paper (Medium Grit) Tape Latex Paint

 Teacher Preparation:

During construction of the electric vehicle, students can experiment and comprehend methods of power transfer, using glue, measurement, making a simple electric circuit . It is up to the teacher to make sure this background information is provided to students in some manner.

Background

Before invention of gas engines, cars were pulled by horses or other animals. Now gas burning engines are the most popular drive in cars. There are concerns about the air pollutions caused by gas engines and electric cars are entering the market in a fast pace. Electric cars rely the electrical energy stored in batteries, so they will not cause any air pollution.

Because of the limited amount of electricity stored in batteries, electric cars must be made very light so they can transfer a longer distance with a limited amount of energy.

Assembly Procedure

1. Cut the 30cm basswood piece to make two lengths each 7cm long.
    (You may have this already cut to size in your kit)
2. Cut the 30cm piece of 4mm dowel to make two lengths each 10cm long.
    (You may have this already cut to size in your kit)
3. Lay out the components of the kit and cut the plastic tubing into 4 equal pieces.
4. Connect the two wooden blocks to the plastic base using four screw eyes. The screw eyes are placed at an equal distance from the smaller end of the base and at a distance from the edge to accommodate the plastic tubing. A sharp object may be required to start the process of screwing the eye through the plastic and into the wood.



5. Place the axle dowels through the screw eye axle holders:



6. Fit the small pulley onto one of the axles and then fit a large pulley onto each axle as a wheel. Put a piece of plastic tubing between the screw eye and the wheel and ensure that the tubing is not too tight against the eye. Finish off the wheel by fitting an O-ring around each pulley.



7. Using the paper clip as a guide poke the brass fasteners through the plastic base and secure them so that the heads of the paper clips are on the side that has the wooden blocks, not the screw eyes. Place the paper clip under one of the brass fasteners.


8. Cut the red wire into two and strip 1cm from each end. Also strip 1cm from each end of the black wire. Connect one end of a red wire to the positive end of the battery holder and the other end of the wire to the brass fastener that is connected to the paper clip. Connect the second red wire to the second brass fastener. Connect the black wire to the negative end of the battery holder. Notice the location of the small pulley.



9. Position the gray motor clip onto the base as shown in the diagram:



Push the small black motor pulley onto the shaft of the motor and connect its two terminals to the red and black wire. Position the motor into the motor clip and using an elastic band connect the small motor pulley to the small red pulley as shown above.

When the paper clip switch is closed the electrical circuit is made and the electric car will move. Crossing the elastic band will cause the car to move in the opposite direction.

Electric Car project:

Construction of an electric car is an engineering/ technology project. When you try your car in a race, the one that is built with more precision and more considerations, will be the fastest. To build and use this car as a science project, you may find a research subject that is closely related to that. For example you may try to find out:

Which battery brand provides the most power to your car?

Procedure:

Make a slight slope (about 10%) and use your car to carry some load up the slope. Find out what is the maximum weight that can be carried by your car. You may use pennies as weight. Each penny is about 3 grams.

Repeat your test with different batteries and record your results in a table like this:

Make  Bar Graph: You can also use the results to make a bar graph. Bar graph can be used to present your results visually. Make one vertical bar for each battery brand you test. The height of each bar will be the amount of load (weight) the car could carry with that brand of battery. For example you may make a bar 75mm tall indicating to show that the car was able to carry 75 grams with that specific battery.

If you don't have this kit, you can order it now! It is available both as a single pack and class pack. Secure Online Store