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.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
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
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Practical Applications
• Prepares the student
to understand gears
and ratios
• Helps in design of
robots, especially
where speed is an
important factor
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Prepare Test Bed
•
•
Prepare the test bed
by taping a start line
near the edge.
Add a finish line 72
inches away.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Re-Download Firmware (If Necessary)
•
•
•
•
•
•
•
•
•
•
You may have to re-download the
RobotC firmware if you have ever
downloaded any programs or other
firmware to the microcontroller. (If
nothing has been downloaded to the
microcontroller after downloading the
ROBOTC firmware, you may skip
this step.)
• Connect the programming module
to
both the PC and the microcontroller
• Make sure the microcontroller is
turned on
• Open ROBOTC.
• Select Robot/Download Firmware
• Select VEX VM 0724.hex/Open (or
later version of ROBOTC firmware).
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 1 Position the Squarebot
•
Position the
Squarebot behind
the start line.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 2 Run the Trial
•
Run the vehicle by
activating both
paddles on the
remote control
simultaneously.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
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.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 4 Record Time
•
Record this distance on a data table of Wheel Size
vs. Time and Speed
CONDITION
(Wheel
Size)
TIME
(seconds)
1
1 (Small)
Diameter=
______ in.
2.87
2
2.94
3
3.03
Average
Speed
(in./sec.)
4
2.91
5
Avg.
Time
2.97
2 (Medium)
Diameter=
______ in.
3 (Large)
Diameter=
______ in.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 5 Gather More Data
•
Repeat the procedure
at least two more
times to insure that
your measurements
are accurate
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 6 Average Speed
•
Find the average of the trials for the
condition and record it on the table.
Example:
( 2.87 s  2.94 s  3.03s  2.91s  2.97 s )
 2.94 s
5
•
Calculate the average speed of
the Condition
Example:
72.0in
 24.5in / s
2.94 s
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 7 Medium Wheels
•
Switch to medium
sized wheels and
repeat the steps #1-6
with the new wheels.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 8 Large Wheels
•
Switch to the large
wheels and repeat in
the same manner as
the other sized
wheels.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Step 9 Measure Wheel Diameter
• Find the diameter of
each of the wheels in
inches.
• Record the value on
the data table.
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved
Plot Diameter vs. Distance
Wheel Size vs. Speed
Speed (inches/second)
• The plot is a powerful
visual demonstration
leading to a clear
conclusion
• As wheel size
increases, speed
increases
proportionally.
50
40
30
20
10
0
0
2
4
6
Wheel Size (inches)
Vex 1.0 © 2005 Carnegie Mellon Robotics Academy Inc.
Copyright Carnegie Mellon Robotics Academy all rights reserved