The outline of the chassis must match the open bottom line of the model. Being the model symmetrical with respect to the longitudinal axis, it’s enough to draw half of the outline, which is easily done by intersecting a plane with half of the locomotive model. For the cabin, only the lower valance is needed.
Once the section is available, some hand working with the “Draft” workbench is needed, basically to downgrade the intersection object into lower level objects: first from a surface to a wire, then a wire into single edges. Once the edges are available, a wire closing the internal profile must be drawn, to be selected together with the the edges making the internal profile to be joined together again into a new “wire”object which will then be upgraded to a surface.
This is the outer surface to be then extruded and cut through for housing the engine and letting the bogies to be connected (the whole object being mirrored to have it complete).
The class 43 redesign is finished and ready for the 3D printer.
It’s the right time to test the brand new printer at home, let’s print the cabin in white resin, with the highest precision available. Just started… it will take three hours, it will be ready after lunch 😉 .
The lower valance Lorenzo designed with OpenSCAD shows a significant improvement compared to the original basic model I created with FreeCAD.
Nevertheless it remains too spiky and irregular in the inside profile. Here comes into play my skills as a new Blender user: I had a lot of fun learning the basics of meshes manipulation to adjust, recreate and smoothen it.
Now it’s time to adjust the other profiles to this new refined lower valance and re-create the upper part of the cabin.
As a break during the Class 43 IC125 remake, I’ve been asked by Lorenzo to design some buffers, as an easy 3D exercise, which I was glad to do.
Within one afternoon I came up with the design of the Metropolitan Electric Locomotive BT-H 1907 buffer in 1:87 HO scale.
First I drew the section of the buffer, as a FreeCAD sketch, using lines and circles.
I generated the revolution solid from the section to create the body of the buffer, to which I added the plate with the bolts to attach it to the carriage.
The front part still needs to be cut on top and bottom, to reach the final shape: it’s enough to intersect the complete structure with a cuboid, as long as the buffer section and with the height exactly dimensioned to cut the round part of the buffer, wide enough to include all the buffer body.
Once the buffer is complete, it’s time to create an array of as many as wished (in my case 10). In order to have all them printed there must be a sprue added to the matrix of buffers: then let’s add a support to the single element before creating the bidimensional array.
I already uploaded this model in 1:87 scale on shapeways and am waiting for the prototype in Frosted Extreme Detail. After checking it, I will make it available for sale, also in other scales and materials.
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.
Finally I received the first 3D printed prototype: the white one. In the pictures it is next to a 1:76 class 43 shell from Lima (the turquoise one) for comparison. Here below you can see the side details I added: the inset for the grid, the window cuts.
The longitudinal cutouts where the roof starts are meant to host the roof grids: either created with photo-etched metal, or the grid blocks to plug in I will print in the next version.
All the roof details are still to be done, while on the back I made the proper shape and the window cuts are done.
I’m already back to work on the “to do” list for the next version. I’ll keep you posted.