Every year a car show of a different sort takes place in Cub Scout packs all across the nation. The Pinewood Derby offers scouts and parents alike the opportunity to work together and build not only a car, but a lasting memory.
The spirit of the Pinewood Derby is that of friendly, but sometimes fierce, competition. Almost everyone would love to have a car that takes home the first place trophy, so here are some design tips to help you build a car that will fly down the track.
Suggested Tools and Supplies
While you can carve a car with a pocket knife, some more specialized tools will increase your design options. Some of the tools you may find helpful include: a Dremel with accessories, wood files, sandpaper, drill, graphite, paint, a coping saw, variable speed drill, a wheel turning chock (available at hobby shops), and clean up supplies.
Designing the Car
While aerodynamics play a big part in designing a car for speed, with a surface area as small as that on a Pinewood Derby car, the aerodynamics are a minimal factor. The biggest key here is to minimize turbulence by designing a car that has a smooth underside and a lower profile in front. While the classic wedge shape earns points for aerodynamic simplicity, it’s also one of the most overused designs as well. Be original! As your son designs his car, encourage his creativity. Use Hot Wheels cars for inspiration. Let your son design as much as possible and use the design phase of building the car as a teaching tool.
While there are car templates and such on the web, a simple template design can be easily made at home. Just take your block of wood and set it on a sheet of paper. Then trace around the block to get your starting dimensions. Once you have drawn out your design on your template, cut out the template and flip it over. Then trace the design onto another template. This will be used to draw the design on the other side of your wooden block.
You can trace your design through the paper onto the wood using a pencil. Bear down hard and it will make an impression in the wood. Pine is a very soft wood so this s easier than it sounds.
Placing the weights
Simple physics dictate that the further back the weights are located on the car, the greater the potential energy available to speed the car toward the finish line. Be careful not to back load the weights too much or the car’s front may actually raise up off the track and cause your Pinewood Derby racer to crash.
If you’re unsure about the weights, try a balance test. Set your car on a pencil or other small fulcrum to test the center of balance. It should be within an inch of the rear axle.
Make sure you secure the weights onto the car. Any loose pieces may disqualify your car. An easy way to ensure that your weights are secure is to bore a hole in the car and inset the weights within the body of the car. You can then use wood putty or Spackle to cover up the weights and create a seamless finish.
Reducing friction is the key to generating speed. More than any other factor, friction is the single most important aspect to consider in creating a fast car. Try placing your wheels on their nails and giving them a spin. You should notice that some wheels spin longer than others. Try different combinations of tires and nails to maximize spin times.
You will also notice a small notch just below the nail head. Try sanding this off and buff to a smooth finish. You can also sand or file out a small groove in the nail to minimize its contact with the wheel. Once again, the idea is to limit the surface area between the wheel and nail to minimize friction. Please check the rules in your district to make sure this is permissible and also make sure that you don’t grind too much off.
Friction also occurs between the wheel and track. Smooth out your wheels by slowly turning them with a variable speed drill equipped with a wheel lock. Wet some super fine sandpaper and deplane the wheels ever so slightly. You cannot carve grooves in the wheels, but you can smooth them out to reduce friction.
Check your district rules for this, but most districts only permit dry lubricants like graphite. Graphite is an excellent lubricant, but it must be worked into the surfaces to be effective. Just squirting the powder into the wheels is ineffective. Once you have coated the inner wheel and nail spin the wheel on the nail to smooth out and compress the graphite.
General Tips and Tricks
Rate your wheel/nail combinations. Place the best wheels in back, where friction is greatest due to weight placement.
Don’t make the car too thin. I have seen cars shatter after crossing the finish line on their first run because the car’s design removed too much wood.
Always use safety equipment when working with power tools.
Wheel alignment is just as important on a Pinewood Derby car as it is on your own. Try rolling your car across a smooth, level surface and look for drift. Adjust the nails to eliminate it.
When painting the car, use spray paint in thin layers. Then finish it with a glossy clear coat to give it that ultimate shine. Be sure to account for over spray, and paint the car before placing the wheels on.
Try to remember this is your son’s car!