3DPrintedRailRoad Pocket Cars

While designing parts for a “Thomas” size model railroad I found that “Matchbox Cars” had the wrong scale. A “Matchbox Car” was almost the size of a “Thomas” engine, so I needed cars built to a smaller scale.  Also, they shouldn’t look like modern automobiles since steam engines became obsolete about the middle of the 20th century.  The result was “Pocket Cars” because they fit neatly in your pocket.  This is the complete personal vehicle fleet.

For printing “Pocket Cars” I use a 0.15mm layer height and a 200% bottom layer thickness.  I put about 1mm of plastic on the outside surfaces as a shell.  Since my printer has a 0.5mm nozzle I use 2 vertical shells, 6 horizontal top and 6 bottom layers.  I set a honeycomb fill pattern with a 35% fill density.  You will need support turned on for the fenders when printing the “Pocket Cars”.  I do use the “Skirt” option when printing.  This gets plastic flowing to avoid a skip as the print starts.  If the slicing software allows: set 2 loops, 2mm from the object, with a skirt height of 2 layers.  Use the same slicing parameters for the wheels without support.  The wheels were output in a separate STL file so they may be printed in a different color (I use Black for the wheels). 

There are not enough wheels in the Trucks_and_Cars_Wheels.stl file for the whole fleet.  I found that in using “print-run” to drive my printer, it would pause the print while it updated the computer display when I had multiple copies of the “Wheels” compiled into single G-Code file.  Then the printed wheels had “lumps” from plastic ooze.  You may need to print multiple copies of the wheels to fully equip your fleet.  

Note: a complete motor fleet is contained in the STL file instead of individual files/vehicles.  This prevents sagging when printing a single small object.  You will probably want to print multiple copies, each printing with a different color.  You can never have too many pocket cars.

After printing the car bodies remove the support material and run a 9/64” (3.5mm) drill through the axel holes.  The edges of the fenders may be squared up by a couple of passes against some fine sandpaper. Cut the axels 24mm long from 1/8” (3mm) poplar dowel.  Press an axel end into a wheel with a drop of superglue.  Then slide it into the car body and press another wheel onto the other end (Note: the smooth side of the wheels go toward the car body).  If the wheels are loose on the dowel, a drop of super glue on the end of the axel before assembly should hold things in place. Make sure that the wheels are well secured/glued so that a “young engineer” cannot remove and swallow them. Be careful not to get any glue on the axle inside the car.