CALCULATING GEARING RATIOS: Investigation 6-1

Complete the following investigation. Apply your notes and what you learn to the design of your car. Experiment with ideas on your car.

6-1	Effect of Wheel Size Investigation
Materials Needed: Prototype car Chassis Wheels Motor Temporary power source (3V battery) Lightweight foam tape Procedure: (see Figure 3) Experiment with the varying of wheel diameter by building up the diameter of the drive wheel(s) on your prototype car using various materials. How much larger would the wheels need to be to make the car's top speed twice as fast? Three times as fast? How can large wheels hurt the performance of your car? How does the size of the wheels affect acceleration? Try using materials like weather-stripping foam tape to increase the diameter of the wheels. Figure 3: Investigation setup - add to size of the drive wheels Observations: Wheel size is as important a factor in the car's design as the transmission ratio; in fact, they are closely related. Try to calculate what distance your car travels per one revolution of the motor. The transmission ratio will tell you how many revolutions the wheel axles will turn per motor revolution, and the size of the wheels will tell what linear distance the car will travel per wheel revolution.

6-1

Effect of Wheel Size Investigation

Materials Needed:

Prototype car
- Chassis
- Wheels
- Motor
- Temporary power source (3V battery)
Lightweight foam tape

Procedure: (see Figure 3)

Experiment with the varying of wheel diameter by building up the diameter of the drive wheel(s) on your prototype car using various materials.
How much larger would the wheels need to be to make the car's top speed twice as fast?
Three times as fast?
How can large wheels hurt the performance of your car?
How does the size of the wheels affect acceleration?

Try using materials like weather-stripping foam tape to increase the diameter of the wheels.

Figure 3: Investigation setup - add to size of the drive wheels

Observations:

Wheel size is as important a factor in the car's design as the transmission ratio; in fact, they are closely related. Try to calculate what distance your car travels per one revolution of the motor. The transmission ratio will tell you how many revolutions the wheel axles will turn per motor revolution, and the size of the wheels will tell what linear distance the car will travel per wheel revolution.