Here is a simple snap together train model. The train prints as a single piece with no support required (there are two support blocks for the rear wheels within the design that easily snap off after printing). Then the wheels (4 small and 2 big) can be printed. Finally the wheels snap onto the train. We found if the front 4 small wheels are a little tight then gently squeeze the mounting pegs (axels) with a pair of needle nose pliers to loosen them up. SketchUp model is included for tweaking the design (or putting your kid's name on the train).