I've mentioned my experiments with arcade-cutters, fashioned as you see below by cutting away pieces from these low-grade steel thumbscrews, and filing-in some interesting notches and steps; the resulting doo-hickey then fits into the drill press to make a rotating cutter. I make a row of such circular cuts on a strip of wood, then slice the strip in two right through the centers of the circles, producing a strip of half-circular arch patterns, which I then dice into the individual blocks.
Here, I am gluing two of the arcade-blocks onto my prototype's two natural keys. Also I'm gluing the glass tile and stacked wooden block onto the sharp key in the middle.
Ultimately, all the wooden parts of the keyboard will be painted black; the naturals will be topped with black ceramic tiles (not the ones I'm using here in the prototype, though); the glass sharp tiles have a white background already, handily enough; and then the arcades (just the curved part) will be hand-painted with metallic gold.
As I have added the mass of the arcades and tiles to the fronts of the keylevers, it has put my key-action all out of whack. With no keys on the fronts, the bare keylevers were working pretty well with a 5:1 fulcrum position. Once the keys were added, the length extension dropped the ratio to as low as 2.5:1, which felt too low. And the mass made the levers too close to balanced: not enough return force. (None of this was a surprise: I was already worried when I found how well the levers worked without the keys; I had hoped they'd be too "hard" and too much leverage, so that adding the keys would "fix" the problem.)
So I've gone from being afraid of too much leverage, to wondering how I can get enough! Basically, the fulcrum wants to be just about right up at the back end of the visible key surfaces, i.e., right underneath the name-board of the instrument. This means that there will be a large differential in "touch" between the front and the back of the keys -- indeed, the backs of the sharps will likely be pretty much unusable. And the keys will have a noticeable curved trajectory, there won't be any illusion of pushing straight down on something. Essentially, the playing position will tend to be right out on the front edges of the naturals and sharps. And the dimensions of these keys are much shorter than modern piano keys, which will facilitate this type of playing. Short strokes, with curved fingers: I believe the style will be more similar to what is called Baroque fingering style, though I am no expert on any kind of fingering style.
So I will have to re-juggle the elements of the front guide, to put the fulcrum far forward and the first set of guide nails behind. Also, I think I will have to change the position of the damper-cords, i.e., the position of the hole which determines where their pulling force is taken from the lever. In the prototype I started out with a very short distance from the fulcrum, even less than 1:1 motion ratio. I like having the dampers move slowly and only a small amount, but it needs to be a little more because I find I want to adjust the travel of the keys down to a narrow, high-leverage stroke. The dampers were working well with the original, longer key-dip, but I think once I have both lower and upper touch rails adjustable (lower is fixed on the prototype) I will want to dial the stroke down and this will make the damper motion too slight.
I hope that once the fulcrum is moved forward, there will be enough or close-to-enough returning force. But I suspect more will be needed. So the question is, how to obtain it? A second set of springs would work, as I plan to use on the clavicytherium, and then the action would be fully adjustable in every important respect. But I don't like the idea of making things intentionally "more difficult", for no gain. Another possibility is to increase the mass of the strikers, either by adding metal (small washers and screws perhaps), or by using larger/heavier pieces of wood. Mass added to that end has a 5x amplification. And there does not seem to be any problem yet with the strikers being too massive (e.g., second-bounce). Greater mass will presumably increase the maximum forte loudness available (though I still don't think I understand even the basics of percussive sound production very well). More interestingly, I believe greater mass will enable a lighter touch for piano: a slower minimum velocity will still cause the mass to move far enough to touch the string. So it seems like, perhaps I should increase striker mass until either mass-related problems start to appear, or until I obtain enough return-force; and springs or weights on the lever which are not part of the striker, should only be used to fill in if a limit is hit in striker mass.
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