Performance Tips

This page identifies four thresholds (and therefore 5 tiers) of Pinewood Derby car performance. Every car begins its life below the first threshold, as four nails, four wheels, and a block of wood.
As a Pinewood Derby Organizer, I make it one of my primary goals to make sure that everyone gets past the second threshold.
The statements which follow combine personal experience with information found on the Web. They represent sound advice to the best of my knowledge, but I have no doubt that you can find differing opinions elsewhere.

Threshold 1 - Do or Die
Your first goal is to make sure your car can make it all the way down the track.

Build your car within the rules. If you can't pass inspection, you can't race.

Assure ground clearance. If you add weight to the underside of your car, you should chisel or drill out areas in which to put the weight, so that the weight is "inlaid". Failure to do this usually results in the car underside scraping the center guide rail.

Assure vertical clearance. Our current lane judge provides plenty of clearance for most any car. However, the lane judge/timer used at the District might be different. Some lane judges/timers have only about 3" of clearance, so be sure that your car will fit under that. Crashing your car into the finish line at 120 scale miles per hour is exciting, but is not your objective.

Threshold 2 - Avoiding "Slow Car Disease"
It's sad. You often see a few cars that are at least a foot or two slower than all of the other cars. These are the cars with the dreaded slow car disease.
And what's even sadder is that slow car disease is easy to prevent, if you just take the time to do a few simple things:

Lubricate your car. Even if you put up huge signs that say "LUBE HERE NOW!!", someone will neglect to lubricate. We make it a point at registration to ask each participant if he has lubed.
Make your car weigh close to 5 ounces. There is often a Dad (or two) who believes that, according to the underlying physics, weight doesn't matter.
Take it from me. Weight matters! If you don't believe this, I strongly urge you to perform your own test, or at least check out the experimental data found here and here.
Install axles and wheels reasonably well. Axles must be in kinda straight. Axles must be secure. Axles must not bind against the wheels, that is, there should be enough room so that the wheels turn freely. Axles and wheels should be free of glue, peanut butter and jelly, chocolate, molasses, syrup, apple sauce, yogurt, and any other foreign debris.
Don't play with your car. Treat your car with care, at least until after Race Day. The more you play with it, the more likely you are to cause it to run more slowly.

Threshold 3 - Keen Competitor
Oh, so not being slow isn't enough? You want to be fast? Fast enough to maybe even win a ribbon?

Put the weight in the back of the car. On a concave track such as ours, this means that the center of gravity of the car falls a greater distance. In other words, there is more potential energy to convert into kinetic energy.
The tradeoff is that your car will be less stable, but if do everything else correctly, it's a favorable tradeoff.

Put the rear wheels near the back of the car. Even if you have to use the pre-cut grooves, you can do this. This makes a car whose weight is in the back more stable. "Popping a wheelie" during a race does add excitement, but it won't make your car run faster.

Car as long as rules allow. The longer your car, the farther back you can put the center of gravity.

Prepare your wheels. Sand away the mold projections left behind from the wheel casting process. Do this on the wheel tread and on the wheel hub. Be careful not to fundamentally alter the shape of the wheel.
Failing to sand away the molding on the wheel tread can cause your car not to roll straight, which means you'll spend the entire race rubbing the center guide rail.

Prepare your axles. Put each axle in a drill chuck so you can spin it at high RPMs. Use a small file to remove the burrs on the underside of the "nail head".
Then use a strip of moistened fine grit sandpaper on the cylindrical part of the nail, where it will contact the wheel. Finally, put some toothpaste, chrome polish, or jeweler's rouge on a small strip of cloth and polish the axle to a high gloss.

Align your axles carefully. Your axles should be square to the car body. If they are not, the wheels will spend too much time rubbing against the axle heads and the car body. Additionally, your car may not roll straight and will therefore spend too much time rubbing against the center guide.
Don't trust the pre-cut grooves in the block. Sometimes they aren't square. Drill out the grooves so your axles go in straight, or if your rules allow, don't use the grooves at all. Do this drilling before you cut out the car body. It's easier to drill a good hole into a square block of wood than into a car-shaped block of wood.

Make your car aerodynamic. This may make only a small difference, but every little bit helps.

Threshold 4 - Top Gun
Oh, so it's not enough to just be fast? You want to be really fast? Well, basically you have to do everything above, and more, and you have to do it exceedingly well.
However, knowing what to do and knowing how to do it or even why you should do it are not the same things.
So if you're game, set aside some time and visit Stan Pope's definitive treatise on car design and construction.

Last updated August 24, 1998, 3:00 PM
Copyright 1998 © by Cory Young. All rights reserved.