nameboard and stops design

Well, now it's official, I have to finish this instrument by the end of this year!

As you can see, I have started fabricating the front panel (nameboard) and other elements related to the stops mechanism.  In order to do the lettering, I had to finally decide on the order of the stops:

8va sitar bsoon buff mod mute1 mute2 sust

...which is somewhat determined by the mechanical constraints, but turns out to be a good ordering from a functional point of view as well.  This gives something of a tonal continuum, left to right, from "buzzy" to "muffled".   Also, all of the stops which modify the tone after initial excitation, i.e., the "mutation" stops, are to the left.  On the right side are the controls which do other things than tone mutation: the moderator affects the initial production of tone, the mutes bring on silence.  Originally I had planned to make these mute stops "pull for sound", but now they will instead be "pull for silence".  This is mainly to make them work in a more-useful manner with the machine pedal (the left pedal): as the pedal is pushed down, adding sonic effects (which, generally-speaking, tend to reduce the total volume of sound), it is more likely that one will want to remove an active string from the pair, rather than add one.  Especially given that some of the effects (sitar, 8va) only affect one of the two strings in a pair: the first pedal position (part-way down) can introduce the effect while leaving both strings active, and then the second pedal position (all the way down) can mute the other string which doesn't have the effect, thus causing the effect to become much more prominent.

The stops mechanism will be attached to the back of the nameboard, fitting into the 4 inch space between the nameboard and the front of the wrestplank (usually nameboards are mounted right up against the wrestplank).  The entire assembly will be held in place with two screws, not glue, so that it can be easily removed, analogous to the keyboard and action.

Pulling the knobs will activate organ-type rollers which transfer the motion to the sides (four to the left, four to the right), where attached actuator arms will pull control wires forward through a distance of about 1/2" (3:1 leverage from the knobs).  Each stop mechanism will have a low-force spring return (low enough force as to not override the stronger spring-induced "click" which seats the stop knob into either the fully-pushed-in or the fully-pulled-out position.

The stop knobs can be rotated as well as pulled.  When the knob is pointing straight up, in the vertical position, the stop is in manual mode, and it can be pushed or pulled freely.  Turning the knob to the left engages the stop with pedal position 1, and to the right engages with position 2.  When stops are engaged to the pedal, they can no longer be moved by hand; instead, as the pedal is pushed down, first all the stops engaged to position 1 are moved outwards; as the pedal is pushed further, the stops engaged to position 2 also move outwards.  Releasing the pedal retracts the stop knobs, in the corresponding reverse order.  (Stops can be disengaged from the pedal, by rotating the knobs back to vertical, at any time, whether the pedal is down or up; the stops stay in whichever state they were in at the time they were disengaged.)

One issue yet to be figured out, is how to manage the spring force inevitably associated with the sustain mechanism (damper-lift).  Unlike all the other stops, which don't have an intrinsic spring force and which will have specific return springs added, the sustain stop has a relatively large amount of spring force to act against: it has to push all the damper springs down simultaneously, thus lowering the dampers away from the strings (in my unusual, dampers-from-underneath design).  This force is no problem to handle with the leverage of the dedicated sustain pedal (the right pedal).  However, in keeping with my gadget-centric design sensibility, I want to also treat the sustain function as "just another stop", susceptible to the handstop and machine-pedal mechanism like all the rest.  (Initially I avoided this conclusion, but at the very least I wanted to have a handstop which allows the dampers to be permanently disabled without having to hold the pedal down: this, after all, is the primary mode associated with historical pandalons (more often spelled "pantalons"), as well as with the hammered dulcimer itself, the underlying inspiration for this type of instrument.)

Having the sustain stop susceptible to the machine pedal, would seem to imply that the "click" force of the sustain handstop will have to be strong enough to hold the stop in the out position, against all the damper spring force.  I don't yet have a clear vision of how this will work.  I suspect the "click" will have to be too strong.  Using a mechanism involving an inclined plane which "plateaus" can eliminate the back-pull of the springs when the stop is fully out, but still something will have to provide all the force to move the knob in the first place.  Anyway, no clever solution here yet, but I'm seeking one...

keylevers...

I have started fabricating the keylevers and associated parts, which involves much repetition at rates of 49 or multiples thereof.

Unlike in my three-key prototype, on the real keys, I have decided to use little blocks to hold the striker spring wires.  On the prototype, these wires made a 90-degree bend and were seated into shallow holes in the keylever itself, but this has proven unsatisfactory: a firmer seating is needed, and I don't like drilling deeply into the already precariously thin and light keylevers.

The blocks have a horizontal hole drilled through, end to end.  The spring wire will seat into the back end of this hole, facing the striker.  The hole on the front face may be used for an optional "secondary touch" mechanism which I have designed; I won't be sure whether the mechanism is needed until I play the instrument for a while.

I made this little jig to hold the blocks in position for drilling.

I have gradually developed a technique for obtaining reasonably-accurate hole positions, despite the remarkable tendency of small drill bits to wander, and despite what seems like a large amount of play in my drill press bearings (are they all like that, or only the dirt-cheap ones from China?).  The key is to have a well-placed starter mark, which I make with an awl; and then I position the drill (with the power off) with its tip centered in the starter mark, and *then* turn on the power.  Because I often need one hand to help hold the piece, and the other hand to hold the drill press lever, I installed a wire-tie hanging off the end of the power switch, so that I can pull it with my teeth and thus turn on the power when my hands are occupied.  Potentially dangerous, but effective!  (Given how much easier it now is for something sweeping past to snag the wire tie and turn on the drill, I'm now much more careful about pulling out the little plastic "ignition key" which disables the switch, when I'm not using it.)

I thought I'd have to rig a complicated and tedious clamping system to glue the blocks onto the keylevers.  However, the Titebond II sets up so fast on these dry, porous, absorbent basswood joints,  that I found I could just hold the joint firmly by hand for less than a minute, and the parts would already be firmly stuck together.  Then I'd just let them sit for an hour or so, and good to go.  Indeed, one block I noticed I wanted to move, after only about two minutes of drying, and I just *barely* got the pieces apart in time; it took quite some force to break the bond.  Very much longer, and it would have been the wood that was breaking.

Here are the 49 keylevers in the frame.  I will next attach the plywood keys (but not their ceramic and glass coverings, yet).  Then I will do the painting and finishing I have planned for the levers: black paint on the keys, clearcoat on the rest of the levers.  Then I will finally attach the guide-wires, spring-wires, and felt pads for the strikers (thus these items will not be exposed to the clearcoat).

I have found rectangular glass tiles with a white background, which are the perfect shape and surface quality for the sharp keys.  However, I'm still searching for the right solution for the natural key coverings.  I am convinced that ceramics *may* be a good key covering; but I've been unable to find pre-made tiles which fit the bill, despite many "almosts".  So I am now planning to try making my natural keys out of clay, myself -- for the second time.  I already tried making the naturals from "Della Robbia" oven-bake clay, but this type of clay will clearly not be durable enough for this application.  So now I will try "real" clay, fired in an actual kiln at 2000-something degrees F, with glossy black glaze.