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.