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What I did on my Sunday...
So after the successful electronics milestone yesterday, the though was today to work on the non-electronics hardware -- the case that will look (somewhat) like a concertina.

For those who don't know, here's what a 1920's Wheatstone concertina looks like (image ganked from Wikipedia):

While that concertina is octagonal in shape, hexagonal is also a common shape (Wheatstone's 1844 patent shows a hexagonal concertina). Oh, for those electronic buffs who are thinking the name Wheatstone sounds familiar, it's the same Sir Charles Wheatstone as popularized Wheatstone's Bridge for measuring voltages and resistances.

So my plan was to use CAD software to layout the hexagonal end-caps, complete with hole markings and other details, print the layout out at full-scale, glue (via glue-stick) the layouts to the 1/8" craft plywood I have, use our (old, poorly maintained) scroll-saw to cut out the hexagons and our (old, poorly maintained) drill-press to drill the indicated holes.

The scroll-saw did the job, but not as well as it could have. I need to get a new blade and install it correctly before I do the next bit of cutting. The drill press is unusable and should be thrown out. I do have a 9.6v hand drill that I can use for this, though.

Here are the two end-caps cut out:

From ConcertinaProject

From ConcertinaProject

The end-caps are designed to have 6 sticks, 1/2" square by 2.5", bolted to them to allow the attachment of the side panels. One stick is installed, to test how well that will work. It seems like it'll work well.

The holes for the switches are not drilled here. I have them specced on the layout as 1/4" holes. Before I drilled 48 holes, I made 1/4" hole in a piece of waste to verify my switches would actually fit:

From ConcertinaProject

The result was yes-and-no. I need a 17/64 hole in order to get the screw threads through so I can bolt it down, but 1/4 is perfect for just letting the button heads through. I was thinking of adding a second hexagonal end-cap to cover the mounting hardware for the switches, and given how nice the resulting exposed button head looks, I think it's a good idea -- more in keeping with the image of a "real" concertina.

There's not much more I can do on the wood tonight: I need to get a larger drill bit and a new blade for the scroll-saw. I might do some more work on the PCB layout.

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This all looks pretty good! Make sure that the buttons can be that close to each other on both sides (the inside part of a button switch may be bigger than the outside).

I'm curious how you're going to implement the bellows and use it to send MIDI commands ... I believe sound requires both a button push and bellows, is that right?

Nice looking vintage concertina too.

Bellows? I'll admit, one reason for going with the all-electric model is so that I *don't* have to tackle making bellows. This will be a fixed-sized box. A future model might have movable bits, but I doubt I'll try to tackle making it air-tight.

I have a test (using corrogated cardboard instead of wood) of a 2x2 array of switches spaced as appropriate (0.4x0.5in). They are not touching on the backside.

It's a nice concertina picture, but it's not mine, I got the image from Wikipedia.

I see -- so it won't play exactly like a concertina. I guess it'll just send note-on at button push, and note-off at button release?

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