Students create the ultimate rubber band race car
When you were a kid, did you ever have one of those toy race cars that was powered by a wound-up rubber band? If you did, chances are it wasn't quite as striking as Cirin. Modeled after mid-1950s Formula 1 cars, the one-off mini racer features state-of-the-art construction, and 16 ft (5 m) of looped elastic that allows it to travel 500 ft (152 m) at speeds of up to 30 mph (48 km/h).
Cirin was designed by students Max Greenberg, Sameer Yeleswarapu and Ian Cullimore at the Art Center College of Design in Pasadena, California. They created it to compete in the school's Formula E Race, an annual event in which teams from around the world pit their custom-made rubber band-powered miniature cars against one another.
The car's mechanical layout was arranged using SolidWorks software, after which several physical prototypes were built and tested. Construction of the final version's one-piece main body was sponsored by 3D printing company SolidConcepts, and involved using laser sintering to selectively melt successive layers of nylon powder.
Its "bio-truss" structure was inspired by the internal structure of birds' wing bones. Offering a high strength-to-weight ratio, this design not only allows the unibody to withstand the high torsional stress delivered by the tightly-wound elastic, but it also meant that the car could be assembled using hardly any fasteners.
The single elastic band that powers Cirin is wound into 8-inch (203-mm) loops, and runs within a carbon fiber tube between two eye bolts – one located at the car's nose, and the other in the geared drive mechanism at the rear axle. That band is manually wound by removing the nose cone, and then held tight until go-time via a servo motor.
A second servo is used for the steering system, which (along with braking) is controlled by radio remote control.
Cirin reportedly cost over US$500 to build, and that doesn't include the 3D printing donated by SolidConcepts. It also didn't win the race, incidentally, although the team did pick up the design, build, and approach award.