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The attached STL files can be used to build a reference model rubberband car that goes along with the rubberband-car-building project. The project is designed for students 8-12 years old. Students will learn the basics of 3D design over six one-hour sessions by taking a rubber band propelled car and converting it into a 3D model. Students will then modify and print out necessary parts (wheels, axles, and frame) for their vehicles. After assembling their 3D models students will race their vehicles to test and measure the travel distance of their car. They will also have the option to customize their vehicles to test on different terrains.
Students will learn the basics of 3D design by taking a rubber band propelled car and converting it into a 3D model. Students will then modify and print out necessary parts (wheels, axles, and frame) for there vehicles. After assembling their 3D models students will race their vehicles to test and measure the travel distance of their car. They will also have the option to customize their vehicles to test on different terrains.
3-PS2 Motion and Stability: Forces and Interactions
3-PS2-1 Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object. [Clarification Statement: Examples could include an unbalanced force on one side of a ball can make it start moving; and, balanced forces pushing on a box from both sides will not produce any motion at all.] [Assessment Boundary: Assessment is limited to one variable at a time: number, size, or direction of forces. Assessment does not include quantitative force size, only qualitative and relative. Assessment is limited to gravity being addressed as a force that pulls objects down.]
This project: students will be asked how the car is moving -- where is the force and how does that cause the car to move?
3-PS-2 Make observations and/or measurements of an object’s motion to provide evidence that a pattern can be used to predict future motion. [Clarification Statement: Examples of motion with a predictable pattern could include a child swinging in a swing, a ball rolling back and forth in a bowl, and two children on a see-saw.] [Assessment Boundary: Assessment does not include technical terms such as period and frequency.]
This project: students can be asked to try to replicate the object's motion, for example by turning the rubber band the same number of times. Does it result in the same motion on the same floor?
4-PS3-1 Use evidence to construct an explanation relating the speed of an object to the energy of that object. [Assessment Boundary: Assessment does not include quantitative measures of changes in the speed of an object or on any precise or quantitative definition of energy.]
This project: students will be asked to relate energy via rubber band turns to the speed of the car. They will also be asked why that speed changes depending on terrain.
4-PS3-4 Apply scientific ideas to design, test, and refine a device that converts energy from one form to another.
This project: students will design, test and refine a rubber band powered car.
3-5 ETS1 p. 46 Engineering Design
3-5-ETS1-1. Define a simple design problem reflecting a need or a want that includes specified criteria for success and constraints on materials, time, or cost.
This project: students will describe their criteria and constraints based on the materials they have available (e.g. can we build an engine? no...)
3-5-ETS1-2. Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem.
This project: students will complete weekly prototypes as they attend the weekly sessions.
3-5-ETS1-3. Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.
This project: students will help define the tests and criteria for winning the final race at the end of the sessions
Lesson Plan and Activity
Day 1: Introduction to the car and to Tinkercad
Show the students the video motivating the project
(15 minutes, but you may want to find ways to make this a bit faster),
have students assemble the non-3D-printed version of the rubber band car (15 minutes),
Introduce Tinkercad design basics by demonstrating the wheel (20 minutes). The wheel will need to have an hole that fits the toothpick.
(10 minutes) Show students how to download their object for printing.
Day 2: Wheel test, axle construction
assemble (or fail at assembling) the wheels from last time (and test); (15 minutes). We expect failure, this is great.
wheel fixes (20 minutes);
discuss design of the axle pieces (basically cylinders, but one has a catch in it for the rubberband) and start design (25 minutes). Note, our reference design has a wider axle and wheels of size appropriate for that axle These can be used as reference for the instructor and/or for students who miss a session.
Day 3: Axle Test, Body Design
dealing with failure and object fit -- we are likely to see failures and need to re-design to make wheels and axles fit (20 minutes)
discussion of design of the body: what are the issues? (axles need to fit, rubberband catch needs to fit, do you want it hollow?) (10 minutes);
Final work and race across various terrains (60 minutes)
3D Printing Basics
Duration of Lesson
The project is designed for 1 hour per week sessions over at least 6 weeks.
The day 1 video is at https://www.youtube.com/watch?v=hjXYVpAyYG0. The teacher will also need to acquire toothpicks, straws, bottlecaps and rubberbands for the first day. You should be familiar with basic shapes and design in Tinkercad (tinkercad.com)
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