Aaron Widmar
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Tips for Building a Better Soap Box Derby Car—and Racing It

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Tips for building better soap box derby car

If you’re building a soapbox derby car to race, you want it to win
Photo: Victoria Pickering via Flickr/CC

Soap Box Derby racing has long been a cherished way for families to put their collaborative, creative, and competitive juices to work. And while participants in this downhill racing sport claim to be enjoying the hobby for the fun of it, everyone (especially the parents) would secretly admit…they’re really in it to win.

Because victory is everything these days, here are a number of aspects to consider when making your winning soap box derby car.

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Tips for Making the Best Soap Box Derby Car

After you buy your kit with regulation wheels/bearings, you’ll begin looking for ways to tweak your kit to improve its design. To have a winning car, you have to reduce friction as much as you can. You can do this in a number of ways:

Alignment: Because wheels are standard-issue across the board, make sure you take care of yours. Treat them well and don’t get them banged up. Keep your vehicle’s alignment perfectly straight to reduce the deceleration caused by turning the wheels. They should be able to spin smoothly and freely.

Aerodynamics: Make sure your soap box car is smooth, sleek, and doesn’t have angles that would increase wind resistance. While driving the cart, keep yourself as low inside it as possible.

Lubrication: Keep your wheel bearings and axle spindles slick. You’ll need a quality lube that will stay moist throughout the day, as most competitions limit the amount of times you can grease your wheels to once or twice. Racers often use lighter fluid, metal conditioner, or Teflon to clean and lube the bearings.

Braking: While everyone’s obviously focused on going fast, being able to stop is important also. The most effective brake design for a soap box derby car is a lever in the center of the car that the driver pulls, lowering a shoe or other rubber stopper underneath the car. Make sure the brake is centered instead of on the side of the car.

Weight: Numerous formula-based calculations and real-life experiments have been done to determine if a heavier or slower soap box derby car will go faster. Consensus is that adding weight gives the car more momentum (acceleration/top speed) and cuts down on air resistance/drag. However, this also makes the car more dangerous during collisions and make it harder to steer, so consider carefully and experiment with weights well before race day. If you do add extra weight, keep it separated from the driver.

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News Sources: Physics Forms, Hoohoohoblin via YouTube, DuBois Area Soap Box Derby

  • Aaron WidmarSenior Editor

    Aaron is unashamed to be a native Clevelander and the proud driver of a 1995 Saturn SC-2 (knock on wood). He gleefully utilizes his background in theater, literature, and communication to dramatically recite his own articles to nearby youth. Mr. Widmar happily resides in Dayton, Ohio with his magnificent wife, Vicki, but is often on the road with her exploring new destinations. Aaron has high aspirations for his writing career but often gets distracted pondering the profound nature of the human condition and forgets what he was writing... See more articles by Aaron.