Unit 4 - Rotary-Linear
How do we get linear motion from rotational motion, and vice versa?
What Am I Learning and Why Learn This Now?
In unit two, you learned how gears can be used to change torque/RPM, as well as rotational direction. Not everything goes in circles though, so now it's time to add linear motion!
When you have completed this unit, you will have "met" competency 5 - rotary-linear. You will get additional practice and feedback on your journal for competency 1 - engineering process, but it will not be a summative grade.
Am I Ready to Learn This?
Before attempting this unit, you should have demonstrated mastery of Competency 3 - Gearing. This unit assumes you already know how to work with the Legos and basic gears. However, you can do this unit without any programming background.
Example Robotics Learning Project: Walker Bot
Construct a physical bot that "walks" a distance of at least two feet. This bot should not have any powered tires/wheels/tracks that touch the ground. It must be powered by a motor.
Minimum Expectations for this project to be assessed:
Journal includes brainstorm of at least two different approaches, with evaluation of pros/cons of each
Journal shows evidence of at least two deliberate tests (and results, changes) of the initial design
Mechanism meets all the requirements of the task
How to Navigate this Unit:
1. KNOW YOUR GOAL: READ the competency 5 rubric and minimum expectations. Ask clarifying questions as needed. Some of the terms may be unfamiliar to you at the start of the unit.
Work on the "Learn" parts in any way that meets your needs -- either order, or cycle between them.
2. LEARN: Investigate ways to create linear motion from rotary motion (or vice versa), including cams, rack gears, and pulleys. What are they, how are they used, how are they assembled with LEGOs? What is a "camshaft" in a car? What is "rack and pinion steering?" How does a compound pulley work?
Cam
Follower / Piston / tappet
Rack Gear
Conveyor Belt (or chain)
Pulley
3. LEARN: Try these tasks, or similar ones. Don't forget to document in your journal - include your task, shots of structures/mechanisms you tried (and programs, if applicable), your observations, and your thoughts about why you saw those results and how to improve the mechanism. (When constructing, remember that there is a huge difference between a wildly flailing LEGO that no longer travels in a real circle, and "controlled" linear motion. Consider where braces and guides must be used...)
Construct a mechanism that extends a platform/bridge across a 1 foot span, powered by a motor.
Construct an assembly line that "hammers" pairs of LEGO pieces together - make the assembly line conveyor and the "hammer" powered by two different motors. You can just make the "hammer" work when you push a touch sensor, or get fancy and use another sensor to trigger the hammer automatically...
Construct a "scale" -- a platform that automatically turns a "dial" wheel as weight is added to the platform/as the platform goes straight down.
Construct a pulley system to lift a "heavy" LEGO box up two feet
COLLABORATE: Post a photo and brief description of your setups to the class discussion group. Construct the mechanism in someone else's post, and make one adjustment or change. Post a photo and description of your change as a reply.
4. FORMAL PROGRESS CHECK: When you are ready, schedule a formal check in with your teacher. Demonstrate and discuss the mechanisms you've built. Show examples of using cams, offset gear axles, rack gears, and belts. Your teacher will help you check your understanding against the competency 5 rubric. Your teacher may suggest/assign other learning tasks and additional formal check-ins to help you. If you are aiming for a '4,' be sure your teacher knows.
5. ROBOTICS LEARNING PROJECT: When your teacher indicates that you are ready to begin, start your robotics learning project for this unit to deepen your understanding. Strongly consider working with your teacher to tailor the project to your specific interests and programming environment. Check-in with your teacher (and classmates) for feedback as you work.
6. SUMMATIVE EVALUATION: Your completed walker bot, combined with evidence of your learning from your journal, notebook & formal check-in, IS your summative for competency 5. You will also get a formative assessment on your engineering journal.