Critical Elements of Pinewood Derby Car Design

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This step may seem pretty obvious, but you just can't believe the number of cars that are built with the wrong end facing forward.  An excellent example is the car on the box containing your car kit.  Yes, it is backwards!! This is no insignificant mistake as using the wrong end for the front will result in a significant difference in the center of gravity and how much weight you can move to the rear of the car and therefore rob your pinewood derby car of precious speed.  If you use the basic block as it comes with the kit, then the rear is the end with the wheels closest to the end of the block as shown in the figure below and on my son's very first pinewood derby car (set track record his first race). 

To avoid any possible mistake, mark the bottom of the car to distinguish the front and rear.  Also, be sure that when the car is finished that the front and the rear are obvious to anyone unfamiliar with the car.  Having the starter place the car on the track with the wrong end facing forward is a not so rare occurrence that will certainly kill any ideas of winning.  Again, seemingly obvious, but important nonetheless.

Making Sure Which Side is the Front

Before we can begin any modifications on the axle, we need to first make sure that the axle will fit in the drill properly.  We do that by filing the bulges at the tip of the axle as shown in the figure below.  In addition, these bulges will enlarge your axle slots or holes and cause a sloppy fit for your axles.  It’s a minor step but useful and simple.  Just hold the axle in one hand and take 2-3 glancing strokes with a small file along each of the bulge areas making sure not to scratch the axle shaft.  Feel for the bumps and file some more if necessary.  Then perform a light sanding with 400 grit sandpaper and your axles are ready for the drill.

Small Bulges on Axle Need to be Filed Down

The first step is to prepare the sandpaper strips. You will need each of the following sandpaper grits and a pair of scissors.

400, 600, 1000, 1200, 1500, 2000, 2500, 4000, 6000 and 8000.

One may not even be aware of the fact that sandpaper can come in grits this high.  They are specialty sandpapers used for fine polishing of metals.  In this case, the highest grits, 2000 thru 8000 will create a smoother finish on the axle than using polishing compound.  The 4000, 6000 and 8000 grits are actually referred to as polishing paper by its manufacturer.  With the scissors, cut  pieces approximately ½" in width.  You will need 2-2 ½” in length for each axle, in other words, for 4 axles, you would need 8-10” of each grit sandpaper total.  See our Axle Polishing Super Kit.

(Safety Point: Make sure that you do not get your fingers too close to the drill and do not have any loose clothing near the drill as well.) 

Before sanding, take a close look at the axle with a magnifying glass to see the scratches and small ribs on the stem of the axle.  Use the magnifying glass between each grit level sanding to view your progress.

Insert the axle into a drill with a little more than ½” of the axle showing.  The first step uses the sandpaper to sand the axle stem.  (With each grit of 400 or above, make sure to keep the sandpaper wet while sanding.  Just dip the strip into a cup of water and shake off the excess water then sand.  The polishing papers 4000 and above can be used wet or dry) Run the drill on medium to high speed.  Fold the paper over the axle and hold the ends with each hand as shown below and continuously move the sandpaper over the length of the stem, making sure to sand the entire area evenly.  Sand the axle stem for approximately 20-30 seconds.  Move the sandpaper back and forth lengthwise over a 1-1 1/2” length of the sandpaper in order to use the entire grit side of the sandpaper.

Sanding Axle Stem

The second step is to sand the axle head as shown below.  With an approximately 1” length of the sandpaper, use one edge of the sandpaper to sand the axle head for about 15 seconds then use the opposite edge of the sandpaper and repeat.  Sand the axle head with each sandpaper grit level.  Lastly, sand the outer edge of each axle head with the sandpaper up thru 1000 grit to get rid of any rough edges.  Do this for approximately 15 seconds.  

Sanding Tapered Axle Head

And the final product

Before working on the wood block, you must first determine if the axle slots are perpendicular to the car body.  Use a straight edge ruler or a triangle if available as shown in figure 44.   Simply line up one side even with the car body and the other with the axle slot.  If both slots are not straight, then start with another block. 

Testing to Make Sure the Axle Slot is Straight

I have checked in more pinewood derby cars that I could ever count and the one glaring issue on weight is that most car builders either do not care about the weight of their pinewood derby car, do not know the advantage of maximizing the weight of the car or simply do not know how to maximize the weight of their car.  Pinewood derby rules allow for a car to be 5.0 ounces.  Once you decide on the design of the car, take into account the types of weight you will use and where you will be placing your weights and cut the weight holes prior to cutting the car body.  Then, once you have cut your car, weigh the car body with wheels and axles and that will determine the amount of weight to allow for weights, weight removal (sanding) and paint.  We generally count on .1-.2 ounces for paint and putty so we get our cars to around 4.8 ounces prior to painting and then add supplemental weights to get the car to the maximum allowable weight.  A heavier car will go faster.  Getting the weight to a maximum 5.0 ounces is not as important as the placement of the weight but important nonetheless.  Take advantage of all your options to make your car faster. 

I know this sounds simple enough but it isn't simple at all.  Most races state their rules to be the rules that are in the box.  Really?  You would not believe the car you could build if you just went by the rules in the box.  Get a specified set of rules from your race administrator or determine in advance if specific modification methods are legal for your race.  Too many times a car has been disqualified for things like lightened wheels or extended wheel bases or wheels not flat on the track when the "rules in the box" do not say anything about these car design tips.  Get our speed tips book, identify which speed tip methods you want to incorporate and determine if those speed tips are legal for your race.  Don't assume that just because the rules don't state that a certain tip is illegal that it is fine for your race.  A race administrator may have a totally different idea in their head as to what is legal for the race. 

The Pro Axle Guide is designed specifically to insert the axles into the slots consistently in the same location and to insert them straight.

With an axle partially inserted into the axle slot, place the tool on the bottom of the car with the ridge in the axle slot as shown below.  The gap gauge is positioned between the car body and the wheel hub to provide the perfect gap between the car body and the wheel.

Press the axle and wheel onto a hard surface while firmly holding the tool to the block as shown below.  Apply downward pressure on the axle and continue until the wheel is against the axle guide and will go no further.  Then press the axle in the remaining portion with your finger or other instrument.  The best option we have seen is to place a hard disc on the table that is small enough to fit inside the outer wheel diameter similar to the smaller 3/8” dia. tungsten discs although any flat hard item with a smaller diameter should suffice. 

 Repeat for the other axles and you are done!!!

No matter how good your equipment or technique is, the wheels and axles are going to be different when fully modified.  And, just like any marriage, the two must fit perfectly with each other to make things work their best.  We suggest you modify more than the normal set of wheels and axles and test not only the best individual wheels and axles but which pair up the best with each other.  How to decide that?  Well, that is the next speed tip...

The tips we have posted for free here and the various other tips you will see as you venture through our website should get you started on a fast pinewood derby car.  Just think though, that if we are willing to post all of these items for free, what else could you be missing?  Our Speed Tips Book, Dominant by Design, is not only the most extensive pinewood derby speed tips guide available on the market, it is the only speed tips book written by someone who has risen to the highest level in the national racing leagues where all the competitors have dominated their local races.  To win a national championship at the highest level for the most technically advanced division takes a tremendous amount of experience, knowledge and creativity about this fun sport. Take advantage of our experience and tips and you can dominate your pinewood derby race as well.