As many of you will know, rail vehicles have to be all a single skeletal mesh. (At least that's my understanding.) For those using Blender and who find it easier to model each moving part seperately (understandable,) here (courtesy of the Blender exchange) is a great way to automatically create seperate vertex groups for your seperate meshes when you join them, great for bone weighting, as I think it's called. Also useful if you want to seprate a piece and work on it some more, or anything like that: https://blender.stackexchange.com/q...ake-a-vertex-group-which-contains-the-vertice
