Pinewood Derby Stories and Photos from Maximum Velocity
Grading On The Curve
Does that phrase bring back memories of elementary and high school? For most people, the grading curve brings back bad memories.As you recall, the grading curve was used to assign letter grades. Those on the right side of the curve received A’s and B’s, those on the left side received D’s and F’s, while those in the middle received C’s. In most classes, there were a few "brains" that distorted the curve for everyone else, leaving us with a lower GPA than we would have liked.
But the Bell Curve itself is not inherently bad. In many data sets, the numbers tend to arrange themselves in a bell-shaped curve. There are always the low and high oddball numbers, and the much larger group of average numbers. In pinewood derby racing, this is often seen. There are a few cars that are very fast, a few cars that are very slow, and the rest are arranged in the middle.
If we apply the Bell Curve to pinewood derby racing, we might arrive at something like this:
Pinewood Derby Grade A - Trophy winner B - Competitive C - Middle of the pack D - Crossed the finish line, but generally last F - Didn't cross the finish line
Just like in school, the challenge is how to move up one or more letter grades. Not surprisingly, the methods available to move up a grade level are the same in both school and in pinewood derby racing: study, tutoring, and practice.
To help with the tutoring aspect of this, I'd like to share some ways that you can improve your pinewood derby letter grade. The tips are cumulative, so if you want to move from an F to a B, you will need to implement all of the F to D, D to C and C to B steps. I have not provided the implementation details; most of them are available in past newsletters, or in our speed tip booklet "Speed to the Finish".
FROM F TO D Cars that don't cross the finish line generally suffer from one of the following problems:
1. The car is not lubricated, or is lubricated with a substance that is detrimental (Powdered Teflon, grease, soap, etc).
Resolution: Lubricate with graphite
2. The wheels are restricted from spinning due to paint or glue.
Resolution: Paint before mounting the wheels, and make sure the paint is dry. Be careful with glue; I recommend against using Super Glue to attach the axles, as this type of glue commonly locks up wheels.
3. A wheel gap is too small, resulting in a wheel that doesn't spin freely.
Resolution: Set the wheel to car body gap with a gap gauge (or a credit card).
4. The car is much too light weight.
Resolution: Make sure to add weight to your car.
FROM D TO C Once your car crosses the finish line, there are several more steps that will move your car up to the middle of the pack:
1. The car is shy of five ounces (or the maximum weight for your race).
Resolution: Design the car so that you can readily add weight so that the car weighs five ounces.
2. The axles have flaws that prevent smooth spinning.
Resolution: Remove axle flaws with a small file, and then polish the axles.
3. The tread and inside edge of the wheels are not smooth.
Resolution: Lightly sanding the running surfaces with a fine grit, wet sandpaper.
4. The wheels are not mounted accurately.
Resolution: Verify that the axle slots are square before building the car, and then mount the axles squarely in to the slots.
FROM C TO B Now that your car is starting to perform, let’s step it up a notch. Here are some tips to help you run with the big boys:
1. The wheels are lubricated, but not thoroughly, and not with a high- quality lube.
Resolution: Before mounting the wheels and axles on the car, thoroughly lubricate the wheels with a top-quality (99 percent pure) graphite, such as Max-V-Lube.
2. The car weighs five ounces, but the weight is not properly located.
Resolution: Locate the weight towards the rear of the car. The final balance point should be between 1 and 1-1/4 inches in front of the rear axle. Make sure to use the axle slot that is closest to the end of the block as the rear axle.
3. The car does not roll straight.
Resolution: Adjust the alignment until the car rolls fairly straight over eight feet.
4. The wheels are smooth, but not "trued" (i.e., they are not perfectly round).
Resolution: If allowed by your local rules, use wheels that have been trued on a lathe, or true a set with the Pro-Wheel Shaver XT.
5. All four wheels are (more or less) touching the track.
Resolution: If allowed by the local rules, lift a front wheel off of the track.
6. The inside wheels hubs are making full contact with the car body.
Resolution: If allowed by the local rules, cone the inside wheel hubs, then make sure they are coated with graphite. Note that the hubs are already coned on the new BSA wheels.
FROM B TO A Okay, you have a competitive car, but are just shy of winning a trophy. Here are some techniques to gain some milliseconds:
1. The car has too much wood mass, leading to poor aerodynamics.
Resolution: Remove wood mass, leaving a low-profile car.
2. The car has weight spread over a large area, increasing the moment of inertia of the car.
Resolution: Remove wood mass, leaving a low-profile car. Then use tungsten to focus the added weight in a small area.
3. The alignment is not optimal for top performance.
Resolution: Use the rail riding technique.
4. The wheels have full weight.
Resolution: If allowed by the local rules, use weight-reduced wheels.
CONCLUSION Now you are armed with some tips to improve your pinewood derby letter grade. So, get to studying and practicing, and you will be ready for that next pinewood derby test!