Class 43: the upper cabin, refined

The upper cabin is re-extruded, using the newly made lower valance top profile.


The shape is fine up to the real top dome: the diagonal ridge must be removed.
I decided to keep only the lower bulk of the cabin, cutting out the really curved top and the back straight part. This allowed me to focus on the top curved shape.

I realized it intersecting two parts of ellipsoids. The ridge at their intersection can be easily smoothed with the “fillet” tool of FreeCAD.

cap_pyramThis cap extends below the top of the cabin bulk, only the upper part is kept: a solid, shaped as a pyramid, with the faces sloping tangentially to the uppermost section of the bulk, is used to cut out the top cap.

The top and the bulk are properly matching at the sides. Extending the back face of both, the cabin shape is complete: only the spiky edge at the front of the bulk must be smoothed. This is easily done, cutting out the edge with a huge cone.

In the resulting shape there is no more mismatch between the top cap and the bulk. A fillet with a big radius on the cone-cutout right edge (in green in the picture), gives then the final shape. The back of the upper cabin is backwards extended horizontally to the required full length of the cabin.

Class 43 lower valance with FreeCAD

The basic lower valance is too prominent in the upper curved profile and too spiky in the lower part: a round cutout of the shape is needed. The right curve is created with an eight of an ellipsoid, placed and shaped with a fine tuning to match exactly the needed curve as well as the remaining parts of the basic shape.

The front part of the valance is then created extruding the side face of the ellipsoid, while the back side part of the basic valance is kept. With a little work of extrusion and boolean operations, the final lower valance full shape is there.

For the final cabin, an empty shape is needed, with a given thickness. It’s enough to clone (in green in the picture) the full shape, place it backwards and inwards of a distance equal to the needed thickness and cut it out from the original full shape.

Now the new top face of the lower valance must be extracted and used to make the upper cabin profile match the lower valance.

Class 43: once more

Time came to add the details to the class43 plain model. When trying to intersect one of the details with the lower valance, imported as stl object, the troubles came: FreeCAD doesn’t support stl proper handling and it was not really possible to do boolean operations between FreeCAD objects and and stl import. Perfectionist as I am, as well as my modelling partner is 😉 , I took the chance to re-think the cabin as a complete FreeCAD project. The basic shape is still created intersecting the extrusions of the three orthogonal profiles, this time created with Inkscape from the blueprint and imported directly into FreeCAD in  svg format.

The cabin is again split into two parts: the upper part and the lower valance.


Twisted gear easy made

Some time ago I struggled to build a twisted gear with the “loft” tool inside FreeCAD for the logo of our company.

There’s a much easier way: still inside FreeCAD the “sweep” tool used along a helix. It’s enough to draw a helix and sweep the face of the gear along it. gear_helixThe face (in grey) lays on the x-y plane and is centred around the z axis; the helix (in green) is also centered around the z axis. The helix is used as “sweep path” and the face is the object to be swept.

The only tgear_cubericky part to pay attention to is that the upper surface of the sweep solid will not be parallel to the base: it’s enough to have the helix’s height bigger than the height needed for the twisted gear and intersect the resulting twisted solid with a cuboid with the base larger than the gear face and the exact needed height.

The twisted gear is ready:




Swiss buffers: the design

Without any blueprint or measures, but only a collection of pictures, I used Inkscape to do some guesstimations of shapes and dimensions: I imported the digital photos and overlayed on the hand created rectangles and ellipses, adjusting my shapes until they met the original picture. I then extracted the dimensions of the shape objects and used them to design the buffer with FreeCAD. With the supervision my modeling partner expert’s eye, I did the final tuning.

Now it’s time to add the supports for the 3D print and replicate them in a matrix, ready to be printed.