I wonder if it is at all possible to discuss one's homebrewing pursuits
in this NG but without the Mongolian Hordes of infantile technical
ignoramuses venting their spleens at every turn, for it seems to me
that such behaviour can only injure the reputation of amateur radio?

Anyway, first target for the 3D printer is for some shrouds in which
to mount the linear bearings for the HRO-type Catacomb bandswitch
arrangement, assuming sufficient familiarity with the FREECAD design
package.

Then looking at ways of reproducing the external appearance of the HRO
PW dial (although there won't be a worm gear employed) by having the
10:9 gear set up linked by an external idler, as opposed to the off-centre
axis used by the HRO.