I have been thinking about designing and building an autonomous driving robot for a while. But then I figured this would be enough work even without designing the gears and wheels myself. When I found these geared DC motors online for around 1.5€ per piece in a batch of 8 (or 10€ for 4 wheels and 4 geared motors), it decide to go for it right away. These parts seems to be available from a lot of different suppliers, so they should be easy to get. 

The only thing that I was missing was a reference model for doing the other robot parts. So I made this.

In the files tab you find the model as separate .stl files, as .3mf model and also the FreeCAD source code.

Happy printing!