Blender Start Model
This model contains just a cube which has my recommended vertex groups applied to it, plus various standard PBR materials and also a bounding box object and a glass object with a *.onetex material. It also demonstrates how I recommend structuring the collections within a Blender file to organise it in such a way that makes exporting and working on the file easier.
Partially Completed 0-4-0ST 'Invincible'
This file demonstrates one way to animate a locomotive with coupling and connecting rods and inclined cylinders. Also the material setup and vertex groups.
The wheels, coupling rods and the left hand side connecting rod and crosshead are animated, the right side is not, so that you can practice...