Summary

Full 3D View

This is an original design, not a replica of any existing car. I wanted to come up with a design with fenders that I could still print in one piece (diagonally) on my 150 x 150 build surface.

What is a "pinewood derby car shell"?

A pinewood derby is an event created by the Boy Scouts many years ago. Each scout is given a pinewood derby kit typically consisting of a block of wood with slots for axles, 4 wheels, and 4 nails to be used as axles. The scout (and his dad, usually) will then carve the block of wood into the shape of a car, paint it and apply stickers, install the wheels on the axles, and then race it at the "derby", which involves a sloped track with a timekeeping apparatus.

An official scout derby will usually require that the parts in the kit be used for cars entered in the derby. Other organizations (including workplaces) often hold derbies, too, and some of them require the use of the parts in the box, including the block of wood.

These "pinewood derby car shells" are intended to be used with an official derby wood block, cut down to size, along with the axles and wheels included in the kit. A printable model of the shaped wood block is provided. You can either use the printed model or use it to accurately cut an official wood block down to size.

Notes:

Car body: Supports are required. You can choose to print "Body.stl" and add your own raft, or you can print "Body with Minirafts" for a minimal raft-like surface that will aid in keeping the supports adhered to the build surface.

Windshield: I printed this using clear PLA in vase mode, with 4 layers on top.

Exhaust pipes: Plain versions are provided as well as some with "minirafts", to provide something for the supports to stick to.

Everything else is pretty simple and straightforward to print, with minimal or no supports/rafts/brims.

Post-Printing

Smoothing

This car was smoothed with 3d printing resin and baby powder. You can find videos and guides online that describe the process, but here it is in a nutshell:

• Mix 1 part resin and 2-3 parts baby powder in an opaque container (so that it can be stored without hardening due to UV exposure).
• Using a paintbrush or cotton swab, spread a thin layer of the resin/baby powder mix over the body, wherever you want to smooth print lines and gaps.
• Use a UV flashlight (a cheap one--like the kind used to harden resin finger nail polish, which you can order from Amazon or buy in the pharmacy department of Walmart) to harden the resin.
• Sand the body smooth until there are no thick layers left.
• Repeat over any areas that are still rough.

Depending on the infill you use, you should be able to add tungsten weights to the holes in the rear of the body. If you plan well, you can maximize the weights and still end up right at 5 oz. I haven't raced this design, but it seems like it could be pretty fast if you put some effort into it.