This is one of the carriages I'm preparing for my "Euroreprap Railroad System" collection, so it's compatible with other vehicles marked as "ERS".
This model is a complete set of parts - even a wheels' axles are 3D printed (1.75mm filament pieces are used to strengthen the construction).
To learn about the assembly please take a look at this PDF instruction:
>>The carriage is compatible with LEGO tracks (adequate distance between gauge lines) and its native tracks standard: "Euroreprap Railroad System" (free inter-connector track model is available).
>>No support is needed during printing
>>Printers with small bed sizes will do fine (bed size 13x13 cm is OK )
>>No special tools are needed during assembly (I use metal nail file for finishing places where excessive material remained)
>>The model's dimensions after assembly are: 328x88x69 mm (12.72x3.5x2.7 in)
>>If you like to experiment with this model on other track scales, the factors to match them are:
x0,847 for 32 mm track (scale "0")
x1.19 for 45 mm track (scale "G") - please note that after this scaling the minimal bed size will be 15.5x15.5 cm
(scaling factors may slightly differ depending on each printer accuracy level)