first sound! (in a way...)

Here, I am marking out the bridge positions on the soundboard, using a "ruler" I marked off on these steel rods taped together (material from the pedalboard project).

The string lengths are all based on the scaling (maximum tension before breaking) suggested by the string manufacturer.  I don't have a reason to doubt the value, but it would feel a little funny to start stringing up the final instrument without having any experience with this new iron wire.  It'd be a drag to have made some error of a few percent way back when, which I then propagated through all my calculations and stringing charts: I might see each string snap in turn, as I tried to tune it up to pitch.  This wire is notoriously fragile anyway; I'm used to strong steel guitar strings (and they also break!).

To check out the tension situation, and also to test several of my design ideas which have never been tested, I built a "monochord".  Actually, it's a duochord, replicating the two-strings-per-note disposition of the real instrument.  I sized the length for E4 with this iron wire, which is the high E of a guitar, and will be the middle note on this 49-note keyboard.  54-some-odd cm, i.e., only about 10 cm shorter than a guitar E4, which is strung in steel.  The iron is supposed to have a much lower breaking tension than steel, about half, and so the fact that the optimal length for E4 is so close to the guitar scale, shows how far guitars are tuned below their breaking tension.  I.e., I'm going to be operating these fragile iron strings much closer to their breaking point, than guitars...  (Actually, to estimate steel max tension relative to the "harpsichord" string materials, I use the high G4 of a 12-string guitar, which is the highest pitch I know of being strung at 65 cm.  And they sound pretty good!)

I also wanted to test out my bridge and nut design, based on quarter-round oak molding.  More and more, I see that oak is not the right wood for anything on an instrument, even though it has been used in the past.  It is strong and yet machines easily, but the grain is too coarse and uneven.  On my bridge pieces, the molding will be diced up into narrow chunks, 1/2" long each.  Thus, they will be taller than they are wide, so stability and the torque of the string tension, pulling sideways as it does, are of concern.  Also, I think, splitting is so much of a concern that drilling the pilot holes for the bridge pins may not be enough.  Maybe I should "size" the bridge pieces with glue, before finishing.  Or maybe I should give up on oak and find some other hardwood in a convenient shape, such as maple.  I don't have a definite answer, but now I can play with the monochord and ponder these matters...

Glad I tested this out!  I tried to use the same narrow-guage brass-plated nails for my hitch-pins, as I am using for the bridge and nut pins.  But the hitch-pin takes a lot more force, and as you can see, the poor thing bent right over as I tried to bring it up to pitch.  I'm glad to correct this once, rather than 49 times.  A slightly heftier nail seems to do the trick; although the ones I have in that size are not brass-plated, so I may look for some which are to keep a consistent look to everything.

You can see that I am using "double stringing", which refers to the string passing around one hitch pin and folding over to provide both strings of a pair.  The tradition with harpsichords has been to tie a loop in the end of the wire (a minor art in itself), and give each string its own hitch-pin.  But I have seen double-stringing in many other places, where it seems to work fine, including in pianos under way more tension, and in my little 15-note zither, where I can verify the somewhat-amazing fact that the two halves of the string can be tuned to entirely different pitches, without interacting or "slipping".  In the pandalon, the two halves will be at the same pitch, so I think I'm OK.  And stringing the instrument will be significantly easier.

With the monochord tuned up to E4, I can press it against the soundboard of the real instrument, and get a reasonable semblance of how its own E4 may sound.  All the signs are good.  The sound is reasonably loud, louder than I might have hoped.  It is delicate and harmonically-rich, similar to a harpsichord or a guitar, *not* similar to a piano (which is a good thing).  And when the monochord is pressed firmly against the soundboard, the sound no longer seems to emanate from the monochord itself: instead, the locus of sound seems to migrate to the larger sound hole.  So the soundboard is active, and it seems to be doing what it is designed to do -- perhaps even more effectively than my carefully-managed expectations might have expected.