When I printed this nice Jeep https://www.thingiverse.com/thing:1826496
I was missing the base for it.
I designed the base in two version: all printed and version with a 3 mm rod for the axle.
Both work fine, I'm actually surprised how well the all printed version does, wheels spin as crazy.
31.7.2017 Added version with bottom connectors. Use wheels from allprinted version.
Printed in PLA. Print with 4 perimeters for nozzle 0.4 and 4 top/bottom solid layers
The "all printed" version maybe will need to retouch the hole with a 8 mm drill if it prints too small. Sand a little all four axles and snap the wheels on. Add some silicone lubricant it really helps.
The "version with metal rod" you will need a 3 mm diameter rod and 51 mm length
If required retouch the holes in the wheels with 3 mm drill and the holes in the body with a drill little bigger than 3 mm 3.2 - 3.5 mm snap the wheels on the rods and apply some super glue.