A gathering of 115,000 spectators lined the streets along Fifth Street and Grand Avenue in Downtown Los Angeles to witness 40 teams and their gravity-powered soapboxes compete in the Red Bull Soapbox Derby. Outrageous soapboxes, ranging from a Mexican Paletas (ice cream) cart to a more sophisticated Jurassic Park mobile, competed against the clock in a downhill race through a challenging course filled with jumps, tight chicanes, and a monstrous 90-degree bank that was responsible for causing several spectacular crashes throughout the day. Team scores were based on three criteria: speed, showmanship, and creativity, with a maximum combined score of 50 points. Team Import Tuner Magazine’s soapbox was a collaborative effort between Five Axis and Design Craft. It was inspired by the Japanese anime series called “Initial D,” which centers on touge (mountain pass) racing and drifting, and was driven by Formula D competitor Daijiro Yoshihara. The team worked around the clock for four weeks straight to construct what we consider the most intricate and over-engineered soapbox in the history of Red Bull competition. The soapbox’s body, designed by Five Axis of Huntington Beach, CA, was based on the original Scion FR-S sports coupe concept, which debuted at this year’s N.Y. Auto Show. All of the styling cues of the original concept car were retained—but re-proportioned to a toylike scale. Chassis fabrication duties were under the direction of Gary Castillo of Design Craft Fabrication, of Westminster, CA. Follow along as we detail the final stages of our build, as we prepared for competition at this year’s Red Bull Soapbox Derby.
“ The conceptual design behind the chassis was something I came up with in my head as we were building,” Gary says. “The only guidelines I had to follow were the dimensions of the body that Five Axis supplied and how big of a chassis I could build. The original plan was to make the chassis rigid with no suspension, but lo and behold, the crazy guy in me wanted to get all custom on the suspension and chassis dynamics.”
Philip Chase of Tein and Scott aided Gary in fabricating and machining parts for the chassis.
Mild steel tubing was used to construct the chassis, while Summit Racing provided the rod and tube ends for the suspension.
The mountain bike suspension and spring rates weren’t exactly what we wanted, but were closest to what we were looking for to make the soapbox rotate through the turns.
Multiple spacers were added between the rod ends to allow for caster adjustment, while the upper and lower control arms were fully adjustable to allow for camber changes. Gary claimed the adjustable suspension components, including adjustable roll center, would allow for navigating through a tight course and improving handling.
“ We knew the chassis and body combined were going to be heavy, so we installed a custom e-brake setup, Wilwood dual-piston calipers, and a set of cross-drilled disc brakes,” Gary says. The Wilwood brake calipers were not designed to bolt onto the moped wheels, forcing us to fabricate custom brackets to adapt to them.
The look of enlightenment as the team spent late hours at the shop.
One advantage of the pushrod suspension was its ability to adjust ride height. Since we were stuck with the provided spring rates, designing our custom suspension gave us the ability to adjust the motion ratio to compensate for the weight and suspension travel of the soapbox. Mike Kojima, of MotoIQ.com, graciously donated a go-cart seat for the cause.