Rubber Band Racer

thingiverse

In search for a summer school course material we are offering for beginners to design and printing I came up with this: Students can explore the world of potential and kinetic energy in a rubber band racer! They will design and build a racer, experiment with wheel and drum diameters to balance torque and rotations under power. Print Settings Printer Brand: MakerBot Printer: MakerBot Replicator 2 Rafts: Yes Supports: No Resolution: .02mm Infill: 10% Notes: I used the standard settings Post-Printing I used CO2 car axles steel rods (0.125” X 2 1/4 “) to assemble my car but students could just as easily designed their own axles. The hole in the drum was reamed with a 1/8” drill while the holes in the chassis were reamed with a 9/64th” bit to allow them to spin freely. How I Designed This I used Solidworks to design the simple chassis and drum. There is a fixed point on the car that holds one end of the rubber band stationary while the other is wrapped around the drum. In class I have the students design their own wheels as well. Designs this simple could easily be done by any other 3d modeling program. Custom Section Project: Rubber Band Racer. Objectives: Upon completion of this unit, students should be able to: Understand the steps of the design process Understand the concepts potential and kinetic energy Understand Geometry concepts (radius, diameter, circumference), their relationships with torque and how they are applied Understand friction (between drive tires and road) and how it applies Understand the basic functions of Solidworks or any other 3d modeling program Understand the basics of 3d printing Audiences: This project's projected audience was 6,7,8th grade Technology education students but would work with science or math students as well. Preparation: Purchase CO2 dragster axles, and rubber bands. Print the chassis and drum. Steps! Lecture on The Design Process Present the challenge and rules Material supplied (in my case axles) Constraints (My students' cars had to be 1 7/8” wide X 5” long) Criteria (Determine length of track and set a day to race) Lecture on diameter(radius) to circumference and the relationship with torque on drive tires. Talk about traction between the drive tires and race surface (we haven’t tried it but though friction tape used to tape the bottom of hockey sticks may be a good idea to wrap on the tires) Show prototype. The design I have here isn’t a winning car (Every student miraculously will think of the same exact design the teacher shows as an example) wrap a rubber band around it and allow the students to see it in action. Ask what could be changed. Demonstrate how to draw simple shapes in Solidworks or whatever 3d modeling program your school is using. Give them time to design, print, test and redesign. (this is the most rewarding and sometimes most frustrating part of the process) On race day “let em rip!” Results: At the end of this unit each student (or group of student if you choose) should have a printed chassis and a good idea of the design process. As an assessment I would have the students write a reflection paper on what steps they did to make a successful car.