A model of a classic roadster, loosely based upon the Snowberger-Offy 1949 Indy 500 race car. This roadster makes a great toy or model, with working wheels and real rack-and-pinion steering! Parts are designed to be printable, with easy snap-together assembly (and a little super glue).

STL files of the individual parts are included in the downloads, as well as the source wings3d file. An additional wings3d file shows all the parts as assembled. You have the source: Take this model and improve it!

This roadster is an extension of the body shape I designed as a shell for a pinewood derby racer (Thing 282791). Lifted from the restrictions of the derby, I was able to make the wheels properly proportioned and positioned to the body. The wood block chassis got replaced by a plastic chassis accomodating a steering column and real rack-and-pinion steering for the front wheels. Details like exhaust pipes and a front grille that can be printed in a separate color complete the model.

Print the body top and bottom and hubcaps in your favorite race car color. Print the driver in white or natural, and paint the details. Print the wheels, seat, grille, and steering wheel and column in black. The remainder of the parts look good in black, gray, or silver.

The fine-detail parts are the pinion gear, steering wheel, rack, axles, hinges, grille, and exhaust pipes. These should be printed in as fine detail as you can manage (I printed them with 0.1mm layer heights).

Most parts can print without support material, but the notable exceptions are the body top, the exhaust pipes, the driver, and the hinges. Most pieces should print reliably without a raft. Be careful with the hinges, however, as they probably require a raft to prevent them from detaching from the base during printing. But the raft will likely stick to the parts, giving the pins a larger effective diameter. Sand down as necessary to fit, and drill out holes to make sure they're clean. All holes are in one of two sizes, the smaller of which matches a 1/8" drill bit, and the larger of which matches an 11/64" drill bit. To get good hinges, rack, and pinion gear, you will need a good printer and a good slicer!

Assemble the front and rear axle halves, the steering column, and hinges with super glue. All of these pieces will be held in place, so that the glue is just a precaution. Attach wheels to the axles (should work with a press-fit). For extra strength, two collars (rings) are included with the STL file for the steering column, and can be slid down the steering column to better secure the two pieces.

Assemble all the pieces together as shown in the exploded diagram.
Start with the axles, hinges and wheels. Push the wheels onto the axles. Then push the front axles into the hinges (see the exploded diagram for reference---make sure the orientation of the hinges is correct!). Place the rack, hinges, and wheel assemblies on the chassis, and secure the body bottom over the chassis to hold all the wheels in place. The back wheels should rotate freely, and the front wheels should turn together.

Snap the seat into the body top, and run the steering column through the hole. Do not attach the steering wheel until the end.
Holding the body top and bottom close together, insert the end of the steering column into the hole at the front of the chassis, then slide the body top into place and press-fit it onto the body bottom.

Push the steering wheel onto the steering column. Leave the exhaust pipes and grille for last; these will need to be glued on. The driver can be put in and taken out of the completed vehicle.