Pinewood Derby Stories and Photos from Maximum Velocity
Advice to the Beginner - Keep it Simple
(Originally published in Volume 5, Issue 8 - January 11, 2006)
INTRODUCTION Countless times I have had the following phone conversation: "Hi, my son just got a pinewood derby kit, but when we opened it all we found was a block of wood, four wheels, and some nails. What the heck are we supposed to do with it? I expected it to have a car that looked like the photo on the box!"
It can be very daunting to participate in your first pinewood derby race. The event demands some woodworking skill, some understanding of physics, and access to basic tools and supplies. For many people one, two, or three of these requirements are missing.
So, let me share some advice for those of you that are participating in your first race.
CAR BODY Unless you have some experience with woodworking and the tools of the trade, then I suggest going with a basic wedge-type design. Not only is it a simple shape to cut, it also simplifies sanding and finishing. All that is needed to build a wedge is a saw and a hand drill. If you are missing these items, then you can purchase wedges already cut and drilled from several sources.(1)
I recommend recessing weight into the car body. With a wedge, the easiest way to do this is to glue lead wire (2), in holes drilled into the car (see the next section). Holes drilled into the side or back of the car can be covered with wood plugs or with wood filler before finishing.
Note that on many kits - including BSA kits - one axle slot is closest to the end of the block. I recommend using that closest slot as the rear slot (the opposite of the car pictured on the BSA kit box).
WEIGHT AND PLACEMENT To ensure that the car performs well, you will need to add weight to bring the completed car to the maximum weight (usually 5 ounces). An easy weight to use is lead wire. This product is 3/8 inch in diameter and can be easily cut into pieces and reshaped. Note that this product is not typically available in hobby shops, but is available from some on-line stores. Generally, you will need between 2.5 and 3 ounces of weight for a wedge-shaped car.
On most tracks, best performance is attained by locating the added weight towards the rear of the car. For a wedge-shaped car, a good rule of thumb is to place 1/3 of the added weight behind the rear axle, 1/3 just in front of the rear axle, and the final 1/3 about 1-1/2 inches in front of the rear axle.
CAR FINISH If you are unfamiliar with painting models, and you are making a simple shape (like a wedge), then consider using a Body Skin.(3) These full body decals work well on simple cars.
If you decide to paint, then consider using Acrylic hobby paints. They generally work well and clean up with water. Avoid getting paint in the axle slots - use masking tape to cover the slots.
WHEELS Although the wheels can be used directly from the box, some preparation is recommended. This includes sanding the tread surface and inside edge (with the wheel mounted on a wheel mandrel and spinning on a drill), squaring or coning the inside wheel hub, and polishing the bore. Tools are available from on-line stores to assist in these preparation steps.(4) As an alternative, prepped wheels are available from many on-line stores.(5) Just make sure to check your local rules to find out what is allowed/disallowed in your race.
AXLES If your kit uses nail-type axles, then you certainly want to remove the flaws by placing the nail in the chuck of a drill, point first, and then applying a small file to the spinning axle. Next, polish the axles with fine grit, wet sandpaper, and/or other polishing materials.(6) As in the case of wheels, prepped axles are also available from many sites.(7)
LUBRICANT The wheels and axles must be lubricated. Unless restricted by your local rules, go with graphite. It is the number one lube used, and is readily available.(8) Be sure to work the graphite into the wheel hub by spinning a wheel on an axle multiple times. To keep your car clean, and to ensure a thorough lube job, I recommend lubricating the wheels and axles before attaching them to the car.
FINAL ASSEMBLY Mount the wheels and axles onto the car by inserting the axles into the axle slots or axle holes. The Pro-Axle Guide (9) is available to greatly simplify this step.
The wheel hub to car body gap should be about 30 thousandths of an inch. The Pro-Axle Guide has a built in gap gauge, and other gap gauges are available. But in a pinch, you can use a standard credit card as a gap gauge. Just place the credit card against the side of the car, and insert the axle until the inside wheel hub is snug against the credit card. Then remove the card.
With axle slots, the axles will need to be glued in place (a dab of white glue spread over the exposed axles works well - just keep the glue away from the wheels). However, before gluing the axles in place, check and adjust the alignment of the car (see Volume 5, Issue 6 - Wheel Alignment: Make It Straight!).
CONCLUSION I hope that this break-down of the car building steps will ease your mind as you build your first car. Just remember, take your time, make sure your child is fully involved, and enjoy the process. Good luck!