HO Scale Well Car In Two Main Parts.

HO generic double stack well car uses truck: http://www.thingiverse.com/thing:426812

Two main parts held together by clips and then glued or welded. Glue or weld detail parts. Holes for trucks and couplers sized to take 6-32 tap. Use washer or coupler pocket/truck washer between truck and body. Runs on standard HO track. Remove extra material from ends. It is there only to enable printing.

Seems a little undersized for some containers. You may wish to increase size by 1% or so.