2017 Rawlinson Mini-Soapbox Derby Fun Fair Challenge


School Challenge Sponsored by
Frank’s Pizza House



Building The Mini-Soapbox Derby Car

Build & paint a Mini-Soapbox Derby car from the provided material. All cars have a common wooden block chassis, 4 axles with the same 4 wheels. The axles will be loose fitting when inserted into the wood chassis to allow for easy removal.

The Mini-Soapbox Derby “Show & Shine”

The body of the car is assembled together by the class team. Teams can use anything they want that can be glued on and then painted to make the car look good. If teams want a harder challenge, they can carve the shape of the car but avoid carving into the axle holes.

Completed cars will then compete in the Mini-Soapbox Derby “Show & Shine” where they will be judged on artistic design. There will only be one “Best in Show” winner.

The Mini-Soapbox Derby Race

Class teams will race their models on a straight 4 lane, 32 ft. gravity racetrack. Points are scored based on car finishing position from each race. Each car will have a chance to race on one of the 4 lanes to acquire their points. The top 4 cars with the highest points will advance to the finals to decide the winner. The final 4 will do a random draw for their lane of choice. In the event of a tie, with points, those cars will have one extra race to decide the winner.

Race Rules:

  1. All 4 wheels must be touching the track
  2. Car body width does not exceed past the wheels
  3. The weight of car should not exceed 5 ounces (142 Grams)


  • Build the body of the car first before inserting the wheels
  • Add a tiny bit of glue to the tip of the axles to hold them in place to the wood chassis
  • The car body parts should not extend outside the width of the wheels (This may interfere with other cars on the track)
  • Make your class room number as the race car number • Avoid any glue contact with the wheels
  • Add a small race car driver (optional)
  • When adding some weight, position it in way that will help with downward acceleration
  • Try to make the car body aerodynamic
  • Try not to make the car any longer then what it is already
  • Make sure the wheels spin freely on the axles
  • Use Graphite to help the wheels spin faster (pencil lead)
  •  Carve the shape of the wood body to make it more streamline

Some Mini-Soapbox Derby Science

Gravity is the effect of pulling together of 2 objects and its strength depends on their mass (weight). Example: the car moving down a slope.

Gradient is another word for the slope. The steeper the slope, the greater the relative force of gravity and the less the relative impact of friction.

Friction is a force that slows moving objects. It is greater on rough surfaces and less on smooth surfaces, therefore a rough surface will slow down the movement more than a smooth surface.

The downward motion of the car is the kinetic energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes.

When the car has reached the bottom of it’s downward motion, Inertia now comes into play as car continues the forward motion in a straight line. Friction is the resistance of the car as it changes the forward momentum.

Having an aerodynamic car body will help to reduce some of that friction.