Build a Gear Model to master the basics of gears.
- Read through the pupil material in the EV3 Classroom App.
- Collect information about gears that you can use to help your pupils understand concepts such as gear ratio, input and output gear and idler gears.
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 Gear Model.
- Allow them time to do a test run to ensure that their model is built correctly and works as it’s expected to.
4. Explain (10 Min.)
- Have each team perform the experiment using each of the suggested gear combinations, and record their results.
- Make sure that they can create their own testing tables.
5. Elaborate (10 Min.)
- Have your pupils analyse how the different gear combinations relate to the number of rotations and the turning direction.
- Ask each team to briefly summarise the results of their experiments.
- Don’t forget to leave some time for tidying up.
- Give feedback on each pupil’s performance.
- To simplify the process, you can use the assessment rubrics that have been provided.
Gears are all around us! Simply explained, gears are toothed wheels. Two or more gears in a train can be used to transfer force, vary speed and change the direction of rotary motion.
Start a discussion about gears by asking relevant questions, like:
- What’s a gear wheel?
- Are you familiar with any machines that use gears?
- What happens to the turning direction when two gears have meshed together?
- How is the gear ratio related to the number of teeth that are on the gears?
Using the Model
Place the model on a solid and level surface. Make sure that both the gear pointer and the reference motor pointer are pointing upwards. Run the program and count the number of rotations by keeping track of the gear pointer. Both of the motors should turn precisely one rotation. The pupils will change the gearing of the right motor and use the left motor as a reference.
Running the Experiment
As they’re running their experiments, remind your pupils of the following:
- In a testing table, record the experiment number, whether it’s geared up or down, the gear ratio, your prediction of what will happen, the number of rotations observed and turning direction. Make sure to leave space for recording other observations.
- Perform the experiment using each gear combination.
Simplify this lesson by:
- Helping your pupils to analyse how the different gear combinations relate to the number of rotations and turning direction of the gear pointer
- Reducing the number of gear combinations that the pupils must investigate
Take this lesson to the next level by:
- Encouraging the pupils to define a function that will predict the number of rotations based on the gear ratio
- Challenging your pupils to modify the program for each gearing option so that the gear pointer turns exactly one rotation
Teacher Observation Checklist
Establish a scale that suits your needs, for example:
- Partially accomplished
- Fully accomplished
Use the following success criteria to evaluate your pupils’ progress:
- The pupils have understood how gears affect the turning direction of the driven wheel.
- The pupils have explained how the gear ratio relates to the number of rotations of the driven wheel.
- The pupils have learned how to calculate the gear ratio based on the number of teeth on the gear wheels.
Have each pupil choose the level that they feel best represents their performance.
- Bronze: I’ve performed the experiments but haven’t predicted their outcomes based on gear combinations.
- Silver: With some help, I’ve predicted the turning direction in the experiments based on the gear combination that was used.
- Gold: I’ve used my understanding of gear combinations to correctly predict the turning direction and number of rotations in the experiments.
- Platinum: I’ve used my understanding of gear combinations to correctly predict the turning direction and number of rotations in the experiments. I’ve also predicted their impact on the speed and torque of the driven wheel.
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 machines that use gears
- 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)
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