Electric Car

Introduction

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 made 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 wood themselves and design their own car; however, most students and teachers prefer to get all the parts in a kit and make changes as needed.

With this project students can explore:

• A simple propulsion method
• Basic gluing techniques and design concepts
• Concept of stored chemical 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 below shows materials usually found in an Electric Car Kit from MiniScience.

Materials Checklist

Before using the kit, 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, and making a simple electric circuit. Teachers should ensure this background information is provided in some manner.

Background

Before invention of gas engines, cars were pulled by horses or other animals. Today, gas burning engines are still the most common in many vehicles, but concerns about air pollution have accelerated electric car development.

Electric cars rely on electrical energy stored in batteries and can reduce direct emissions during operation. Because battery capacity is limited, electric vehicles should be designed as light as possible to travel farther with the same stored energy.

Assembly Procedure

1. Cut the 30 cm basswood piece into two pieces, each 7 cm long.
   (You may have this already cut to size in your kit)
2. Cut the 30 cm piece of 4 mm dowel into two pieces, each 10 cm long.
   (You may have this already cut to size in your kit)
3. Lay out the kit components and cut the plastic tubing into 4 equal pieces.
4. Connect the two wooden blocks to the plastic base using four screw eyes.

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

6. Fit the small pulley onto one axle and then fit a large pulley onto each axle as a wheel. Add tubing spacers and O-rings.

7. Use the paper clip as a guide, insert brass fasteners through the base, and place the paper clip under one fastener.

8. Prepare wires, connect battery holder, brass fasteners, and motor as shown.

9. Position the motor clip and connect pulleys with an elastic band.

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

Science Project Idea

Research question: Which battery brand provides the most power to your car?

Procedure

Make a slight slope (about 10%) and use your car to carry load up the slope. Find out the maximum weight your car can carry. You may use pennies as weight (about 3 grams each).

Repeat your test with different batteries and record your results.