Shifting Gears

1. Prepare

• Read through the pupil material in the EV3 Classroom App.
• Collect information about gear transmissions that you can use to help your pupils to understand concepts such as gearing up and gearing down.

2. Engage (5 Min.)

• Use the ideas in the ‘Ignite a Discussion’ section below to engage your pupils in a discussion relating to this lesson.
• Divide your class into teams of two pupils.

3. Explore (20 Min.)

• Have each team build the Geared Vehicle.
• Allow them time to do a test run to ensure that the model is built correctly and works as it’s expected to.

4. Explain (10 Min.)

• Have each team perform the experiment at least three times for each of the suggested gear trains, and record their results.
• Make sure that they can create their own testing tables.

5. Elaborate (10 Min.)

• Have your pupils analyse how the gear ratio relates to the distance travelled and velocity of the vehicle.
• Ask each team to briefly summarise the results of their experiments.
• Don’t forget to leave some time for tidying up.

6. Evaluate

• Give feedback on each pupil’s performance.
• To simplify the process, you can use the assessment rubrics that have been provided.

It’s difficult to travel uphill or against the wind on a bicycle. A good gear system is useful in adjusting the power that’s needed to keep moving. When travelling across level ground, you start off in a low gear and then shift into higher gears at higher speeds.

Start a discussion about shifting gears by asking relevant questions, like:

• What do the terms transmission and gear reduction refer to?
• Why are gear units often encased?
• What’s the relationship between the gear ratio and the distance travelled?
• In which situations is gear reduction desirable? In which situations is it not?

Building Instructions

• Geared Vehicle

Using the Model
Place the vehicle at least 10 cm from a wall with the Ultrasonic Sensor positioned perpendicular to the wall. Run the program and wait until the EV3 icon is shown on the Display. Press the Centre Button on the EV3 Brick to start the test run. The initial distance to the wall is measured using the Ultrasonic Sensor, and the timer is reset. The vehicle will move away from the wall by running the Large Motor for one rotation. The distance to the wall is measured again, and the elapsed time is measured to calculate the distance travelled, velocity and rotational speed. The calculated values are shown on the Display until the Centre Button is pressed again to prepare for another test run.

Using the Ultrasonic Sensor
The Ultrasonic Sensor generates sound pulses, which form a sound cone in which objects can be detected. When starting the experiment, do not stand next to the vehicle or within the Ultrasonic Sensor's sensing cone; it’s best to stand behind the Ultrasonic Sensor.

Running the Experiment
As they’re running their experiments, remind your pupils of the following:

• The distance travelled (in cm), velocity (in m/s) and rotational speed (in revolutions per second) will be shown on the Display.
• Record the experiment number, gear ratio, your prediction of what will happen, the distance travelled and velocity in a testing table. Make sure to leave space for recording other observations.
• Perform the experiment at least three times for each gear train option. Use the average value to ensure the most reliable results.
• Refer to the images in the ‘Hint’ to see how to change the gear trains.

Program

Simplify this lesson by:

• Helping your pupils to analyse how the gear ratio relates to the vehicle’s velocity and the distance it has travelled
• Reducing the number of gear trains that the pupils must investigate

Take this lesson to the next level by:

• Explaining the significance of average values (e.g. arithmetic mean versus the median, susceptibility to outliers) that can be used to equalise the measurement errors across a series of experiments
• Encouraging the pupils to define a function that can predict the distance travelled based on the gear ratio
• Challenging your pupils to come up with ways of improving the accuracy of their experiments

Teacher Observation Checklist
Establish a scale that suits your needs, for example:

1. Partially accomplished
2. Fully accomplished
3. Overachieved

Use the following success criteria to evaluate your pupils’ progress:

• The pupils have described the role of the gear ratio in predicting the outcome of their experiments.
• The pupils have applied mathematical concepts and/or processes to determine the relation between the gear ratios and the distances travelled.
• The pupils have evaluated the experiments’ procedures and identified independent, dependent and control variables.

Self-Assessment
Have each pupil choose the level that they feel best represents their performance.

• Bronze: I’ve performed the experiments but haven’t described the role of the gear ratio in predicting the outcomes of the experiment.
• Silver: With some help, I’ve described the role of the gear ratio in predicting the outcomes of the experiment.
• Gold: I’ve used my understanding of the role of the gear ratio in the experiments to predict which gear ratio should be used in a vehicle that would be suitable for moving heavy loads.
• Platinum: I’ve used my understanding of the role of the gear ratio in the experiments to predict which gear ratio should be used in a vehicle that would be suitable for moving heavy loads.

To incorporate the development of language arts skills, have your pupils:

• Create a brief report focusing on the results of their experiments and real-world examples of when gearing up and gearing down can be useful
• Create a presentation explaining the results of their experiments and what they’ve learned

Note: This will require additional time.

The pupils who enjoyed this lesson might be interested in exploring these career pathways:

• Manufacturing and Engineering (Pre-Engineering)
• Science, Technology, Engineering & Mathematics (Science and Maths)
• Transportation (Automotive Technology)