Will's Pinewood Derby Car

So, I live above Joel - a guy I've known and worked with for years. His son, Will, is a Cub Scout and this year was his first "Pinewood Derby". In a nut shell, a pine block is carved to look like a car. Wheels are stuck on and the car is shoved down a long, sloped track where gravity decides the winner. For more information, see the Wikipedia article.

Will is eight, so it's understood there is going to be a lot of parental involvement. The rules state the child must understand each step in the building of the car, but the kids aren't expected to wield power saws. The race is really a competition amongst fathers. The obvious political analogy here is that the children are like puppet states assisted by the "super powers" of their parents. Instead of being supplied with weapons and advisers, the children are supplied with race cars and helpful cues when to put it on the track. Most parents use regular wood working tools and sandpaper to make the block of wood car-like. For Will's car, Joel and I decided to take a more precise approach and used my CNC mill. I had some fear that this would spark an arms race among the parents the likes of which has never been seen, but that only lasted for a few seconds. "I thought it would be fun" is how most wars start and this one is no different. This was my first job involving surface milling and 3D design. Everything up to this point has been simple extrusions and 2D contour milling paths. We started working on this one week before the race.

Will wanted the car to look like his favorite Pokémon toy.

Pokemon Toy

Conveniently, the head of this toy tore right off and reattached with ease. Despite what you might assume, the Pokémon in question is actually red, not silver. This is what we're actually going for -

A lofty goal indeed

We decided to make the car a head with wheels and Joel wanted fire coming out of the front. I constructed the model using the Pokémon head as a visual guide. I think I made a fantastic looking alligator - it was necessary for the toy shape to be elongated. The milling was done in two parts - half on one side, then the block was flipped over the other half was milled out. I built the model for one side, then mirrored it for the other. We ran out of time for detailed fire, so Joel decided to carve it in later. That's the long tab you see in the front of the car. It is not in fact a massive tongue. Sorry to disappoint all the Kiss fans. Maybe for next year's car.

3D model

Once the model was complete the tool paths were created and then it was off to the mill, which is conveniently located in a large cardboard box in my living room. Will and Joel's other children came up to see the mill in action and I think Will had a good understanding of what steps were involved. Lauren, Joel's nine year old daughter, understood every step very well and had even done some 3D modeling of her own in the past.

Milling in action

My living room or "one good reason why girls never come over"

The end result was workable, but less than fantastic. There's an obvious seam which is likely a result of not having the proper tools to get a common starting point (an edge finder) and instead using what was on hand (an aspirin I found on the floor). The error here was purely cosmetic and was easily sanded out.

Finished milling job

The milling job took four and a half hours for each side, so nine hours total. The amount of time required is a combination of my not knowing what I was doing and being stuck with the tools I happened to have. The largest end mill I had was a 3/16" and job would have gone much faster if I had a larger diameter mill on hand. I finished the milling operation at 7 am on Saturday morning. The race was on Sunday at noon. Joel, Julie, and I started working on the finishing touches Saturday night at 6 pm. The finished product turned out very well, I think.

Majesty.

Joel formed the horns out of sanded dowels. Will and Lauren helped paint the car and picked out the color. Julie, Joel's wife, did a fantastic job of paining the eyes and adding shading. Joel dremeled out indentations in the bottom of the car so we could hot glue lead weights I sawed in half in order to get the car up to the maximum weight. Thankfully we have a business partner, Eddie, who has mastered the ordeal of Pinewood car races. He advised us the two most important things were to make the car as heavy as possible (5 oz. limit by the rules) and to use a solid lubricant like graphite to make the wheels spin as easily as possible. Joel used a dremel tool with a polishing attachment as a gear to rapidly spin the wheels in order to polish the axles.

The end result? Will won 1st place in his age group and 5th place over all.

Beginning a proud tradition of ruthless Pokémon victory and rule.

The car could be improved in several ways. It should have won first, but was beaten out by several others. I'm not sure how the other cars were able to go so fast but I distinctly heard a sonic boom at one point. There is clearly some pinewood derby warp drive technology that we have yet to master. Joel did a great job carving fire into the front of the car, but it would have been neat to have approached the milling operation from three sides and created the fire surface with the mill.

Working on the car was a lot of fun. I learned a lot about surface creation and milling. Having a deadline always speeds up learning. I'm glad Joel invited me to be involved.