This is my version of the Flintstone's Flintmobile or Cavemobile. It won't win many races, but it will probably be the only one at your derby.
3/3/2024 Update: I've added new versions of the side panels, dashboard, and seats that are easier to assemble. You can attach the side panels to the stone wheels first, then slide the seats and dashboard in after the glue has dried.
The 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:
Just super glue all the parts together.
You can add tungsten weights to the holes in the rear stone wheel to end up right at 5 oz. Playing with different infills and weights can get you close to the ideal front/rear balance.