Relay Race





Name of Activity Relay Race
Author STOMP
Keywords vehicles, steep ramp, relay, team, course, cars, gears, weight, weight distribution, friction, power, accuracy, wheel, axle, speed
Subject NXTs
Grade Level 4, 5, 6, 7, 8, 9+
Time 2 Hours Total
Brief Description Students will build two types of vehicles, one that is good for going fast on a flat surface and one that is good for climbing a steep ramp. Students will work together to create a relay team of 2 cars that must complete a course with a flat area and a steep ramp.
Lesson Objectives: To learn about gearing and how it can help with climbing ramps.
To learn complex programming that includes Bluetooth for communication between NXTs.
Materials Needed: Poster board, cardboard, wood or foam core for a ramp sloped about approx. 30 degrees from the horizontal.
NXTs or RCXs
Assorted building materials.
Computer running ROBOLAB or MINDSTORMS
Preparation and Set Up: Setup the relay course.
Set up a flat track that is five feet long with a start and finish and set up the ramp.
Collect necessary materials.
Arrange students into groups of 4.
Distribute the necessary materials.
Necessary Background One of the important things about robots is their ability to communicate to each other. Robots are often limited in their capabilities because it is too difficult to construct multi-tasking robots. For this reason, many different specialized robots are constructed, and then these robots are programmed to communicate to each other. For example, a certain Mars rover may specialize in searching for rock, while another may specialize in drilling rock. These two rovers can work together by sending signals to each other, in the same way we communicate, yet simpler. The following activity incorporates specialized robots that can communicate to each other to complete different sections of a single task: a relay race with different terrain.


Mechanical advantage of gears
- Small gear on motor, larger gear on wheel and axle for more torque to drive up the ramp
- Large gear on motor, small gear on wheel and axle for more speed to drive across the floor

Weight distribution of vehicle
- More weight on the front of the ramp vehicle
- Less weight for the entire floor vehicle

- Wide wheels for more contact surface area on the ramp vehicle
- Narrow wheels for less contact surface area on the floor vehicle
- Spacing between wheels and sides of vehicle so that the wheels rotate without rubbing

- Large diameter wheels in the front of the ramp vehicle
- Ramp vehicle should be short in length

- Long floor vehicles with four wheels to ensure that the vehicle travels as straight as possible towards the stationary ramp vehicle

  1. Introduce the activity and tell students that two people in their group will build and program a car to travel as fast as possible on a flat surface, and the other two people will be building a programming a car to drive up a ramp.
  2. Allow students to build their cars. Remind students that gears might help them build a car that can climb a ramp.
  3. Have students program their vehicles.
    1. The first vehicle must travel 5 feet to the base of a ramp and then stop. The students should use time to stop their robot, or use a light sensor if the course is marked with tape.
    2. When the first vehicle stops, it must send a message to the second vehicle (a number). This will trigger the second vehicle to start climbing the ramp.
    3. The second vehicle should start climbing the ramp when it receives the message from the first vehicle.
    4. Communication between RCXs/NXTs may be tricky.
      1. Use the ‘send mail’ and ‘wait for mail’ icons on the floor and ramp vehicle, respectively.
      2. Each group should send a different number so as to avoid confusion between RCXs and NXTs.
      3. Zero the receiving mailbox at the beginning of the program.
      4. Press run on both robots before starting the relay.
  4. Allow students to test their cars and rebuild/reprogram accordingly.
  5. At the end of class gather the students together. Have each team run their cars and time how long the relay takes from start to finish.
  6. Talk about what designs and programs worked the best and how you could improve upon each teams work.
Reference 1

Digital Measuring Wheel





Name of Activity Digital Measuring Wheel
Author STOMP
Keywords NXT, rotation, sensor, measurement, accuracy, diameter, circumference, pi, distance, conversion
Subject NXTs
Grade Level 4, 5, 6, 7, 8, 9+
Time 1 Hour Total
Brief Description Use an NXT and a rotation sensor to buld a digital measuring wheel. The device can be
pushed by hand on the ground or at a distance using a handle. Check the device’s
accuracy with a measuring tape.
Lesson Objectives: - To learn about programming in NXT MINDSTORMS.
- To use measurements and math in programming to collect data.
Materials Needed: NXT brick
NXT motor w/built in rotation sensor
LEGO wheel and axle
Computers running NXT-G MINSTORMS software.
USB cords to connect NXT bricks to computers
Data collection sheet
Preparation and Set Up:
- Arrange students in groups of two.

- Distribute necessary materials.
- Distribute a data collection sheet.

Necessary Background Measuring wheels are used in many places to find the distance of a line. The number of
rotations can be translated to distance if the circumference of the wheel is known.
The circumference can be found by measuring around a wheel or by multiplying the
diameter by pi.


  1. Have students build a measuring wheel device. Attach a wheel with an axle to a motor. Wire the motor to the NXT brick, but do not attach the motor to the NXT brick.
  2. Have students measure the wheel’s circumference to use when calculating distance.
    1. Option: You may also have the students find the circumference by measuring the diameter and multiplying the diameter by pi.
    2. Option: You may also discuss radius by having students multiply the radius by 2 x pi to get teh circumference
    3. Option: Have students find the circumference all three ways and compare answers.
  3. Have students program the NXT brick to display the distance traveled by doing the following:
    1. Divide the rotation degrees value by 360 to get the number of rotations traveled (or have the rotation sensor count in rotations) using the “Math” Block.
    2. Multiply that value by the circumference to get a distance value by using the “Math” block.
    3. Convert this distance value to a text value using a “Number to Text” block.
    4. Display the text value on the NXT screen using a “Display” block.
    5. You will need to enclose the program in a loop so that it is continuously displaying measurement data
  4. Check the accuracy of the device with a tape measure by having students measure the length of different lines.
  5. Discuss, as a class, reasons that the measurement may not be accurate. Does this always matter? How could you make the measurement more accurate?
  6. Discuss the different variables in this experiment.
    1. The independent variable is the number of rotations.
    2. The dependent variable is the measurement shown on the screen.
    3. Discuss as a class the relationship between these two variables.
    4. Option: draw a line graph of rotations v. acutal measurement (inches, cm, meters, etc.) that the NXT brick displays.
  7. Discuss where a measuring wheel might be useful and where it is not useful. What other tools can be used to measure distance?
Extensions or Modifications: Add a touch sensor to clear data to take a new measurement.
Use a touch sensor to trigger when measurements are displayed.
Add sound feedback when certain distances are reached.
Convert the device to a wench that measures the length of a string wrapped
around it
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