1. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Does Wheel Size Matter? Starter Kit Investigation Introduction: An Investigation into the effect changing wheel size has on the speed reached in a set distance.

2. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. The Investigation Hypothesis: A larger size wheel will reach a higher speed in a given distance. Variables: –Independent: Wheel size (3 diameters) –Dependent: Distance traveled

3. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Practical Applications Prepares the student to understand gears and ratios Helps in design of robots, especially where speed is an important factor

4. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Prepare Test Bed Prepare the test bed by taping a start line near the edge. Add a finish line 72 inches away.

5. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Modify the Squarebot Please note: if you have a programming kit and have downloaded any programs to your controller, you will need to download the default code before beginning this investigation. Select Build & Download/Download Default Code on the Easy C interface. (If you have not downloaded any programs, the default code is still on your Vex controller.) Modify the Squarebot as shown in Resources/Wheel Size Starter Kit Slide Show.

6. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 1 Position the Squarebot Position the Squarebot behind the start line.

7. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 2 Run the Trial Run the vehicle by activating both paddles on the remote control simultaneously.

8. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 3 Measure Time Begin the timer as the front wheels cross the start line. Stop the timer when the front wheels cross the finish line.

9. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 4 Record Time Record this distance on a data table of Wheel Size vs. Time and Speed CONDITION (Wheel Size) TIME (seconds) Average Speed (in./sec.) 12345Avg. Time 1 (Small) Diameter= ______ in. 2.872.943.032.912.97 2 (Medium) Diameter= ______ in. 3 (Large) Diameter= ______ in.

10. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 5 Gather More Data Repeat the procedure at least two more times to insure that your measurements are accurate

11. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 6 Average Speed Find the average of the trials for the condition and record it on the table. Calculate the average speed of the Condition Example:

12. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 7 Medium Wheels Switch to medium sized wheels and repeat the steps #1-6 with the new wheels.

13. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 8 Large Wheels Switch to the large wheels and repeat in the same manner as the other sized wheels.

14. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Step 9 Measure Wheel Diameter Find the diameter of each of the wheels in inches. Record the value on the data table.

15. Copyright Carnegie Mellon Robotics Academy all rights reserved Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc. Plot Diameter vs. Distance The plot is a powerful visual demonstration leading to a clear conclusion As wheel size increases, speed increases proportionally.