This "snap together" rubber band powered car was printed using a MakerBot Replicator. I've never used 3D software before, so TinkerCad was my choice for first time work. Using TinkerCad (Tinkercad.com), I designed a car similar to the one in chapter one of my book, Amazing Rubber Band Cars.
To make a wheel, you just drag a cylinder onto the workspace. Set the diameter and the thickness and you're almost done. Drag a hole onto the workspace, adjust the diameter and place it in the center of the wheel. Group the hole and the wheel. That's it.
If you want to play with my design, go to TinkerCad.com and search for "Michael Rigsby" Under my things, you will find the wheels, base and sides. Adjust them to suit your fancy, then "Print 3d" which gives you a choice of commercial printing services or downloading a file for your 3d printer.