Lay rub­ber, lit­er­ally

Looped elas­tic al­lows mini racer to travel 152 me­tres at speeds of 48 km/ h

The Witness - Wheels - - MOTORING - BEN COX­WORTH — Giz­mag.com.

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. Mod­elled af­ter mid1950s For­mula 1 cars, the one- off mini racer fea­tures state- of- the- art con­struc­tion, and five me­tres of looped elas­tic that al­lows it to travel 152 me­tres at speeds of up to 48 km/ h.

Cirin was de­signed by stu­dents Max Green­berg, Sameer Ye­leswarapu and Ian Cul­limore at the Art Cen­tre 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 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 $ 500 ( R5 800) 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.

PHOTO: SUP­PLIED

Cham­pion rub­ber band car: printed in 3D and able to reach 48 km/ h over the length of one- and- a- half soc­cer fields.

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