Lego DUPLO train small car, wagon

use 4 mm rod
one screw

How I print it:
Base: 100% infill, support
Bottom: 100% infill, support
Coupling: 15% infill, support
Wheel: 15% infill
Washer: 100% infill, raft

Update 14.7.2017: Nipples adjusted again

Update 4.7.2017: Added support structures to bottom part

Update: 2.7.2017 After many testprints, new wheel STL uploaded. It is the most tricky part for me to desing for good fit print. Hole should be about OK to accomodate 4 mm rod. There is a big radius on bottom edge bl