Lego-Compatible Boxcar

23 Sept 2023 - Realized that the wrong wheel truck frame was originally uploaded. My apologies! This has been corrected in the files.

This boxcar is compatible with Lego train systems. It features a magnetic coupler that allows the interior magnet to rotate to attract vs. oppose the adjacent car's coupler.

M3 screws are used to attach the wheels to the wheel truck frame. They are also used to connect the wheel trucks (aka bogeys) to the car frame. You'll want to have a variety pack of M3 screws handy. Also, be sure the screws used for the couplers are not magnetic. XDOL Stainless Steel M3 screws from Amazon worked fine. I did not use stainless steel on the wheels/truck assembly to provide a more realistic look... those screws are magnetic.

The door is designed to slide open and closed. It is very important to ensure that you clean the tracks prior to assembly. Keep in mind that the first layer of your print typically will have "squish" causing the track to be narrower than intended... at least in the first layer. I actually found that using a 2mm allen wrench worked well to achieve the desired track width. Just run it up and down the track a few times.

There are two different options for the mount frame: One has a skirt between the bogeys, the other does not.

The two roof caps are sacrificial and cover holes in the roof to allow for passage of a 2.5 mm allen wrench. Should you need to remove/tighten the bogeys after assembly, simply remove these caps and print new ones when you are done.

Order of assembly:

1. Secure the wheels (4 per wheel truck) to two wheel truck frames using M3 screws. Tighten until the wheels do not turnout then back the screw out just enough until they turn freely.
2. Insert one magnet into the slot of each of the two couplers. They are designed for a 10x2mm size button magnet. I ordered mine from Amazon "DIYMAG 120 Pcs 10x2 Premium Brushed Nickel Small Round Cylinder..." You may need to use a tool to push the magnet through the slot. It's intentionally designed to be tight to prevent the magnet from working its way back out. You can widen the slot, post-print, of course.
3. Secure couplers to frame using M3 screws.
4. Secure the two wheel trucks to the car's frame
5. Glue two of the Boxcar end walls into the Boxcar's main body. Testor's plastic cement works great!
6. Install the doors into the tracks of the Boxcar's main body.
7. Dry fit-check the roof on the Boxcar's main body with doors. Slide the doors in the track to ensure they open and close without snags or excess reistance.
8. Once you are happy with the slide doors' function, glue the roof on (recommend you install the caps on the roof prior to this. No glue required for the roof caps). Again, recommend Testor's plastic cement.
9. Glue the assembled Boxcar main body onto the frame, using the thru-holes (counter bore) for the M3 screw heads that hold the wheel trucks to the frame. Secure the hopper to the frame using plastic cement or other adhesive that is compatible with whatever plastic you used for your print.