C02 Powered Pinewood Derby Motor.

thingiverse

This Pinewood Derby car was featured in the September 2011 issue of Popular Mechanics. It's a 3D printable motor for an 'outlaw' class Pinewood derby car, designed by the creator's son for his cub scout pack's outlaw class. The car is fully printable and its trigger mechanism was inspired by a medieval crossbow. However, it's advised to take extra safety precautions when using this car as it's potentially dangerous and may scare some people. The motor uses various printed parts including the tankblock, trigger block, pawl, sear, and hammer. The instructions involve cleaning up the plastic parts, cutting brass rods, connecting springs, and filling the hammer with weight for added mass. To use the car, the pinewood derby block needs to be cut into a thin slab, and the trigger and tankblock need to be mounted. The springs are loaded before inserting cylinders, which should pierce squarely in the center of the seals. The car is launched by gently removing the thumb after holding the hammer back with it. A safety note advises adding eye screws for extra security.