A bit of progress, even if still only on small parts. The 1930's Smiths motorbike horn used on the Spitfire as the Undercarriage Warning Horn.
This has been scratch built with the exception of Ross' fine 3D printed top plate.
The top plate was painted with a high shine chrome paint and then distressed(the position in the cockpit I suspect meant that it would have been liable to bumps, rubbing and scratches each time the seat was removed or the Pneumatic bottles were maintained).
The casing is made of 4" irrigation pipe and then the base plate from high impact plastic, machined to fit into the casing as a rimmed plug. The seam was filled with sandable glue.
The pipe, luckily, has the OD which exactly matches the interior dimensions of a Milo tin. So the top of the tin, where the lid fits on, was cut off and interference fit (with glue to support) onto the pipe, forming the rim for attachment of the face plate.
The mounting bracket and terminal block are made of aluminium sheet sandwiched together and the terminal posts of ali rod, threaded to take the screws salvaged from a broken 543 switch. They were made with a 6mm base and 4mm post to lock them into the terminal block "sandwich".
The casing was painted in a fairly thick coating of black paint and then sprinkled with aluminium dust and flakes before being given a final heavy coat of high gloss black. This gives it the appearance of having been cast like the early types rather than "stamped" out like the later models.
The plate at the top of the mounting bracket was shaped with the Jenny to make the strengthening creases. Some nice stainless bolts completed the assembly.
I'm still working on a good Smiths logo and how we will put it on. Ross may be able to build it into the 3d print or I may just get them engraved. I'd rather see the proper raised image in 3D though.