framed for posterity

Done with the basic keyboard frame, which gives a good chance to view it and contemplate its basic design, before I add a whole lot of other parts and mechanisms (such as the dampers) which will tend to obscure the basic simplicity of the striking mechanism.

As you can see here, there are three crucial rails, plus the decorative/protective black front rail.  The fulcrum rail has little blocks of wood which support the keylever axle wire, and also it has a "comb" of steel nails, which guide the keylevers (these unusual details, instead of the usual center "balance" pins underneath the keylevers).  The lower touch rail, farther back, has the other "comb" of nails, completing the side-to-side guide system for the keylevers.  The upper touch rail has no nails, but it has holes drilled through which will guide the damper wires (as seen on my 3-key prototype).

Here the frame is attached to the instrument (which is resting sideways, on its spine edge).

Next up, a whole lotta keylever fabrication, using the lessons I've learned from the prototype...

starting on the keyboard frame

I've started constructing the frame for the keyboard and action.  It's mainly composed of poplar 1x2s.  Everything will be spray-coated with clearcoat, as I'm putting it together.

I added attachment blocks to the instrument, to allow precise positioning: I don't necessarily trust my 2x4 frame to be perfectly straight and square!  Also, the blocks enable (I hope) three transposition positions, for 440Hz, 415Hz, and 392Hz.  This is simply a matter of attaching the action in three different positions with a set of correctly-spaced holes.  But there has to be clearance.  415 will definitely fit, 392 I'm still not sure about...

Whole bunch of hole-drilling, and quite a bit of jigsaw-carving, to make the parts for this.  Much more yet to be done, e.g., the keys themselves!

Here I have it assembled.  Nothing is glued yet, I'll drill some more holes, and finish and paint several parts, before finally gluing it up.

Here you can see my adjustment mechanism for the upper and lower touch rails: a critical aspect of this action design.  This scheme is one of my "inventions", which I have assumed to be viable for years in my notebooks and on-paper designs, but only now am I finally trying it out in real life.  Seems to work as I wanted, thankfully.

Yet to be fabricated, are the two rails which go on the bottom, and which I call the pulley rails -- even though the "pulleys" are just shiny metal surfaces with, hopefully, low friction.  These rails guide the monofilament control cords which move the dampers when the keys are pressed.

more work on key design

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.

dampers added to prototype

Here is the complete 3-key prototype, showing the articulation dampers.

The keyboard would be on the left side in this picture.  As a key is pressed down and the long end of the keylever lifts up, the nylon monofilament cords controlling the damper are pulled upward, but only a short distance because the cord attachment point is close to the fulcrum (just behind the adjustment screws).  This upward tug on the pair of cords is transferred via the two "pulleys", to a downward pull near the end of the damper spring.  The springs are straight horizontal wires, #18 steel, which pass through felt-insulated holes in the thicker (#16) vertical damper wires.  The damper wires are guided by holes running through the upper touch rail; so when the spring is pulled down, the felted top of the damper moves down, allowing the strings to vibrate freely as long as the key is held down.  When the key is released, the damper felt is pushed up against the strings, with the force of the damper spring (which is adjustable).  In the real action, there will also be a sustain mechanism, operated by pedal or handstop, which presses all the damper springs down at once, thus eliminating articulation and producing that harplike, reverberant open sustain sound -- a sound which is unavailable with harpsichords and many other early keyboard instruments.

In the prototype, I have used plain finish nails as the "pulleys"; in the real action, there will be wooden rails with holes drilled which the monofilament will pass through, before making a right-angle turn around a length of round-section brass rod (there still won't be any moving wheels in these "pulleys").  The guide-holes in the wooden rails are needed, because when the sustain pedal is activated, all the cords go slack and they tend to wander sideways out of their proper lines of operation, even crossing over their neighbors on the prototype where there is nothing to prevent that.  Slots cut from the edge of the rails into each guide-hole will allow the loop of

I am glad I took the time to build this prototype, I have found several things that I need to change or alter before building the real action.  There is no problem with the "5:1" ratio, it is not too high; indeed, when the keys are glued to the ends of the levers, the actual ratio at the playing point is significantly reduced, down to as low as 2.5:1.  So, I am planning to shift the fulcrum even closer to the keyboard end of the keylevers, so that a ratio closer to a real 5:1 can be obtained, from a reachable place on the keys.

The dampers do add noticeable friction and drag, more than I'd hoped.  The adjustable force is always a tease!  You can adjust it only so far down: just about the time that it starts feeling pleasingly light in touch, there is no longer quite enough force to reliably seat the dampers, and they start to lag and stick in their guides.  To get clean, fast operation, you have to accept a firmer spring force.  Hopefully the brass rail in the real action will have lower friction...

A different approach would be to make the dampers come-from-above in the more conventional way.  Then they could just use gravity, no springs.  However, the obvious way to drive them would be to let the keylever itself lift the damper directly; but this would mean the dampers were flung upwards at the 5:1 amplified velocity of the strikers; and the weight of the dampers would similarly be multiplied by 5, in terms of additional weight to the keyboard feel.  So, without actually trying it, I have judged that this approach would probably not work so well in this design.  But if the current way turns out to bother me too much, I may try alternatives like this.  Another, hybrid approach would be to use come-from-above gravity dampers, but still use the pulleys and cords to give closer to 1:1 motion (lifting the dampers up instead of pulling them down).  This almost becomes a thought-experiment to demonstrate that there couldn't be that much benefit over the springs, however: enough weight would have to be added to make the dampers work reliably, and basically all the same sources of friction would still be present.

Oh well, I am pretty happy with the initial results, given that this was all invented on paper over months and years, with no guarantee of success.  Even without the changes I now plan to make, the action as it stands works quickly and reliably, it has a wide piano-forte dynamic range, and it already feels faster and lighter than any of the pianos *I* ever get to play.  I'd say, results are promising so far, and a lot more research and experimentation is called for, in this long-neglected field of alternative percussive keyboard action designs.