After exploiting all the available features of FreeCAD, facing its limits for my project and getting the first prototype, time has come for the redesign. There are a few changes in the concept (basically how to split the locomotive into parts and which details to provide) and a new workflow, including openSCAD to design 3D solid shapes which are not simple extrusions of 2D faces, while keeping FreeCAD for some easy geometrical sketches, to extrude simple shapes and to put the basic blocks together at the end. Blender is also of great help to work with the mesh format both for some fine adjusting and handling of curved surfaces to be exchanged among different software tools.
As first step we (my model partner Lorenzo and I) decided to split the design of the cabin with a horizontal plane cutting at the level of the spiky edge on the front, just below the lights housing: he wanted to redesign the lower valance with OpenSCAD.
We started again from the drawings with Inkscape, traced over the blueprint and shrunk to the 1:87 scale dimension.
The valance (the lower part of the cabin) required (and openSCAD allowed it 😉 ) more work: Lorenzo recreated the basic solid inside OpenSCAD , then he could create the valance as intersection of ellipsoids, shaped as he needed, matching the section of the upper part: this hand definition of the shapes would not have been possible in FreeCAD.