Yes it's 5 octaves (plus one note) = 61 keys.
142 strings because 2 strings per note plus the lower range has 4' strings (an octave above) because bass length is foreshortened and the 4' reinforces the tone. That is unusual, most do not have 4'.
For these I have wood for the cases and lids, pine, that originally was large organ pipes. I have a friend who builds pipe organs and when they replace an instrument they get all the old pipes which often they do not use or reclaim so I take them apart and mill down. The advantage, apart from being free (less the work) is that it's normally really old stuff that is clear grain and straight. Bottoms are 1" thick pine (also pipes, milled) glued up usually 3 pieces or 4 (22" wide total).
The soundboard (3mm thick) is quartered red spruce. It's likely old-growth spruce (from WV mountains) that they couldn't get to when they cut it all for airplanes. It has exactly the correct wood qualities for soundboards because of its low density and high stiffness (it's stronger than oak pound for pound). You see a lot of older guitars with red spruce tops. My friend (same one) has a sawmill and he gets me that lumber and I do the resawing. Keys are also red spruce, again for stiffness and low weight. I'd say it's at least as good, if not better, than the Euro spruce.
There is some internal bracing, usually red oak (or white is ok). The bridges are beech because it's very hard (or can be hard maple but usually beech). Wrest planks (where tuning pins go) and hitch pin rails (where other end of string is anchored) are white oak because you want that very strong and hard as there is a lot of tension, not like a piano, but, a lot. Rack (the slotted piece where the backs of the keys ride) is hard maple, to resist wear. Stands are oak, legs of it can but don't have to be oak they are 2" square tapered to 1" at the bottom so plenty strong either way.
Natural key tops are boxwood which is very expensive, it's extremely hard so to resist wear from playing. Likewise the sharps, which are solid ebony (the good kind), again expensive.
There is actually some keys rounding and some gilding not done. The gilt is 23k gold (expensive). The listing (damps the non-speaking part of the string) isn't what's there, now I use a baize (like pool table cloth) which I salvaged from retired church altar coverings (natural fiber) that I tear to strips.
Lid hInges, which you can't see here, are cast brass from UK, a guy there made molds of the originals. The instrument is modeled after Hass 1767 instrument which to me is the fully-developed instrument just as pianos were replacing clavichords.
Strings come from a guy up in Canada who is a materials science prof at one of the universities. That's critical as they (along with other things) determine the sound so they need to be similar metal content to the originals and that is a single source; there are other strings made but they are not as good. All brass, but there are impurities in his closely-held recipe that make them work like the originals. Lowest 8' strings are red brass.
Paint, I use alkyd enamel, a pain, but multiple coats sanded in between with progressively finer papers give a real nice finish.
Basically, apart from the hinges, gilt, paint, and strings, I make all the parts - the tuning pins are ISO nails (they tend to be more consistent diameter) cut/shaped/hammered cold, and the hitch pins and bridge pins are half hard brass rod 1.2 and .8mm respectively. The tangents (sticking up from the keys, that strike the strings) are .6mm brass.
Pic doesn't show all of it so sometime I'll try to put a better pic. That first one sounds good, right now I'm putting together cases for 6 of them, I have the stock for almost all the parts milled as far as it can be at this point but it's still slow going, some things are just slow like you have dovetails at the case joints but a miter joint for the molding so it's do-able but picky work to get it just right.
There is a doctoral thesis on the Hass instruments so that helps tremendously, also I got a lot of help writing to people who are accomplished builders. So the first one was like, how do you.... and while I am making a few changes to these subsequent ones, mostly it's do what I did before; I have a lot of jigs and remplates and so on that speed things up as when I made the first one I was intending to follow on with more. Otherwise if you were just doing one it would not be worth it to do so. I have all the key planks and sound boards made up already so a lot of work, I have the pieces ready as far as they can be thus far.
One of the things that's hard is the tangents swing in an arc and they have to hit the right strings without hitting other ones (the 142 strings are all in the width of less than a foot so they are close together) so they have to be set in the right place in the key and at the right angle. No one seems to approach this the same way. What I did is mathematically determine the location, and it turns out, that if the front edge of the tangent is, in fact, tangent to the string in front of the pair (or the 3) you are striking, then it will never have problems, and with some safety margin. Thus, obviously, their name. Less obvious is that the word "key" comes from clavichords (the first keyboard instrument) because when you take a key in or out of the instrument, you have to rotate it just like a key in a lock to remove or replace it.
And at 70" it just fits either the B3000 or the XLT bed.
I'm trying, gradually and as time permits, to document in a forum I have, how is all this done, because even if you have a paper plan, unless you've done one, it's pretty hard to figure it all out, so I'm trying to create a manual listing all the parts and materials and describing how to put it together. I like it when I am at the point of stringing because then you are working with only metal parts and it's kind of like doing jewelry work as to the few tools used.
Yes I tune them but I hate it but you have to do it to sound good. The first one I bet took me like 6-7 yrs but, that was working intermittently a few months here a few months there because I was making wood organ pipes for money, but I'm totally out of that now. I got the plan back in like '06 but when I looked at it I was like, this is horribly complicated, I could never do this. But after I did pipes a while I was like, hey, maybe I can make the clavichord. So then I spent a bunch of time researching and talking to people before I started. Anyway, however you want to look at it, it's a bunch of work. I'm trying to estimate them at about 350-400 hours each but not sure if that's overly optimistic. I figure I'm about 1/3 done them at this point - not 1/3 assembled, but, I have all the stock and like I said a lot of parts ready to go.
I use only hide (hot) glue. It is extremely strong and has a couple redeeming qualities - you can wash excess off completely (unlike, say, Titebond), and, you can dis-assemble parts if you have to do so, although, it's not easy and not something you normally do. The downside is that you have to work fast to get it together because once the glue cools it gels and things don't go together well. It's not gap-filling so the joints have to be good. Hide glue is a subject in itself. I'll just say, many people go from modern glues to hide glue, but I've never heard of anyone switching back, who does this kind of work.
The nice thing is, when I go to work on the trucks (which has been zero lately as nothing is broken) it's totally different, I'd say there is close to zero crossover on tools, so it gives me a break because in these kind of long projects it's easy to get discouraged or hit temporary walls and sometimes all it takes is get my mind off it a while then come back to it and usually things seem clearer.
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