Derby Car Construction and Racing Tips

You’ve build your car and you are wondering what's next?  Practice, a good understanding of physics, tuning and experience.  There are many resources on the web regarding Soap Box Derby.  Here are some areas to focus on and links to help sharpen those racing techniques.   

Practice.  Find a street or parking lot with a fairly long (300 to 800 ft.) gentle slope to practice on.  Be safe and avoid a location with automobile traffic.  Let the driver get the sense of the potential to kinetic energy transfer.  Using a pair of automotive car ramps as a make-shift starting ramp (at least let the rear wheels roll off to provide some initial momentum.)   Teach the driver to minimize friction, efficiently steer and to use the shape of the course.   Practice seeing how far you can roll.           

Optional Weights.  The basic car kit and wheels will get you racing but to be competitive you’ll want the additional mass to create the momentum to win.  Take the time to learn about weights and figure out where you will get them from, where to lay them out and what is allowed before you get to inspection at the race.   Equalizing the weight on each axel (50 lbs in stock) is recommended but putting more in the rear will help your with the drop off the ramp (and also create more friction on the rear wheels) - so there is a balance to consider.   

Gravity, Momentum, Friction and More. See the Racing and Driving section at Derby Tech.  Also, see   “Physics Involved in Soap Box Derby Racing”

Cross Bind is described in section E23 of the International Soap Box Derby, Inc. Stock Car Plans.  This adjustment corrects for any inconsistencies in axel installation.  Shimming the axles will ensure that the front and rear axels are aligned in the same plane.  Otherwise one wheel can incur additional stress causing friction and alignment issues.  More information found at this link

Spindling is also described in section E23 of the International Soap Box Derby, Inc. Stock Car Plans.  This adjustment corrects for the flex in the axle.  The load of the driver and any optional weights will cause the spindles to bow.  A Toe and Camber adjustment will ensure the wheels roll perpendicular to the road and square to the floorboard.  Specialized tools are needed to perform this adjustment.  Check with your local derby official to see if the club has tools to borrow.

Remember, “You win at the top and lose at the bottom” - the first 100 ft. sets the pace for the rest of the course.