Lego Exercise 1

Team J3T2

Tori Amundson

Krestina Aziz

Justin Berman

Jake Guentert

Jenny Ross

Given a Lego NXT kit and 30 minutes, we were challenged to design and construct a rubber-band powered Lego car that would travel further under its own power than our competitors, with bonus points awarded for first vehicle "to market" and the winner determined by overall distance traveled. We struggled to familiarize ourselves with the various components and their uses in the time allotted, but were able to construct a car that did move under its own power--just not very far! Given the two follow-on attempts at revised designs and further competition, our group worked well together to try to better our designs, and although our revisions didn't actually help the car perform better (it performed worse!), we learned a lot about how it might work, and feel strongly that one more revision would have resulted in a strongly competitive design. Our first attempt and the revised designs were simple constructions consisting of two axles with wheels, connected by two frame members. We attempted to fix the rubber band at one axle and wind it around the other using a lever or hook to hold the rubber band, and we wound it by rotating the axle and wheels manually. We learned during the first trial that the rubber band caught on protruding edges of the hook, which inhibited the unwinding action and stopped the car. Our next revision attempted to solve this problem by using a different, wider hook design, and at the next trial, our rubber-band unwound as expected, but the drive wheels spun freely in place, while the free-wheeling wheels didn't spin at all. We determined that the free wheels didn't spin as they needed spacers to avoid contact with the frame, so our next revision included spacers to keep the wheels away from the frame. During the last trial, our "engine" began to unwind and power the car, but after only a couple of inches, the car stopped. We eventually concluded that the band was wound too tightly around itself, and the pressure it exerted on itself was enough to prevent it from unwinding further. A future revision would require more experimentation with the actual mechanics of the rubber band unwinding, but we did successfully demonstrate that the car could be propelled by a rubber band.