Picture of Pinewood Derby Car on Shopbot
Where my son competes in Pinewood Derby, they have pretty strict rules on what work the boys must do on their own cars.  The boys divisions have strict rules about what can and can't be done.

But THEN there is a DAD's division!   The rules for the Dad's division are as follows:
1) Weighs less than 5 ounces
2) Fits within 1-3/4" by 6-15/16"
3) Uses the wheels in the kit
4) Bring it!

Now, I am a member at TechShop (the one in RDU) -
I decided that I would use the opportunity to learn some new skills, and I would use the Shopbot!

Follow along for an adventure to learn what to do (and what not to do....)
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Step 1: Computer Work

Picture of Computer Work
I had never done any 3D CAD before so I started with Google Sketchup.  I decided it would be interesting to learn, and it had the added benefit of being FREE and running on my mac.  (If Autodesk 123D had run on my mac that would have been a better choice.)

It turns out that Sketchup was NOT designed for this type of work.  I wasn't going to pay $495 for the pro version (which had solid tools.)   I should have just gone to Techshop and used Autodesk Inventor there.  (But I didn't know how to use that either, and I decided that I would just go ahead.)

Anyway, I browsed the Google 3D Warehouse and downloaded a model of a Camaro.   Then I scaled it from the full size down to the width I needed my wheelbase.  (1.5")  I deleted side view mirrors and other details (like the inside of the car).

I downloaded a free plugin that let me export STL from Sketchup.   Then I pulled it into Partworks3D (on the Techshop computers) which let me do the CAM work.  (That is the photo above.)

Step 2: Preparing the wood

Picture of Preparing the wood
I was going to try to do fenders that went over the wheels, so I glued 2 blocks together to get the additional width.
ldabkey2 years ago
Nice car! Any chance you would have the g-code. I have a CNC and would like to try. I use V-Carve Pro.
BluesBayou2 years ago
5 gallon paint stiring sticks are perect for fenders, and they are the same width as the stock wheels..
owlart1013 years ago
Looks good, great job! I would suggest sanding it more though, it looks a little rough
alan412 (author)  owlart1012 years ago
agree. I just was low on time.
Covo alan4122 years ago
Just say you are going for the dimple a golf ball...for speed.
I see, well good job anyways
Reiff2 years ago
Do you know how to solve wheel chatter? my dad and have made 14 cars and never solved it.
Shelby S2 years ago
Neat project, but doesn't that take all the fun out of a pinewood derby: carving the block yourself?
alan412 (author)  Shelby S2 years ago
I guess it depends. I find learning new tools to be a lot of fun.
CementTruck3 years ago
When I was a kid my brother and I had Matchbox cars called "Chevrolet Astro". The look of your derby car is very reminiscent of them and brought back some fond memories.

Keep your son in scouts as long as you can. Kudos.
You sound like a typical Cub Scout DAD, always to the last minute! Looks great! Love it!