EMD GP38/39-inspired freight locomotive for OS-Railway

This is a working fully 3D-printed freight locomotive for the OS-Railway project.
Read more about the project here:
http://depronized.com/2018/02/13/presenting-the-os-railway-system-fully-3d-printed-model-train-system/

This locomotive has an upgraded motor bogie capable of handling much bigger motors than the previous designs. Instead of relying on an external gearbox, this design has a 10:1 gear-ratio built in meaning you can operate it with a standard 380-size brushed or brushless motor. This means a diameter up to 28mm and the pinion has 2,3mm bore but can be drilled up to 3mm without problem.

Print without support, but make sure detect bridging is enabled. The grab rails are designed to be bent after printing. I think you'll see how it is supposed to be bent when you have the parts in front of you. Use drops of CA-glue to make sure the grab rail stay firmly attacked.

For electronics see the Hectorrail 141 page:
https://www.thingiverse.com/thing:2575667

This project requires the following hardware:

Motor: 28mm DC-motor. Search ebay, there are lots of cheap 28mm DC-motors for RC-cars/boats. They usually have 2,3mm shaft suitable for this gearbox. You can also use a brushless 28mm motor but then you need to adapt the electronics accordingly. In that case you can use a digital output on the NodeMCU to send a servo signal to a standard RC ESC.

4pcs 3mm thick 44mm long weel shafts (carbon fiber works well)
1pcs 3mm thick 42mm connection shaft to make the motor bogie 4wd.
2pcs 2mm or 3mm thick 16mm long shats for the gearbox, either carbon fiber or steel.

Ball bearings 6mm OD 3mm ID 2,5mm thickness.
SMR63ZZ ballbearings work well. You need at least 10pcs for the bogies and an additional 4pcs if you want to use ballbearings in the gearbox. This is not required as the gearbox can be built with only 2mm shafts and no bearings. There are two versions of the gearbox included, one for use with ball bearings and one without.

Apart from the screws shown in the explode view, the following is needed:

8pcs M2x16 - 25 (for fastening the body on the chassis, or you can glue.

For the forward bogie:
2pcs M3x12
1pcs M3x14

Use O-rings or small rubber bands on the driving wheels to ensure you get enough traction.

If you want lights, there are 3mm holes for two lights in the front and two in the back.
See schematic on the Hectorrail 141-page linked above.

For further questions and discussions, please visit my forum: http://depronized.com/board/

Update 2020-08-11 - added a missing gear to the pre-assembled STL's of the motorized boogie. One of the two "Gear 11t wheel shaft gear" was missing, however present in the zip-file with individual parts so you don't need to re-print the whole boogie.