The physical design is now roughed in

I got things more-or-less put together tonight. I need longer axles; 20 cm was about 8 cm too short. But anyways, I now know how everything fits, and how the top will have to interact with the furnishings. Designing that will be simple.

The top will only have bridges pressing on it. The Keybox will not touch it. The top will have a perforation for the wheel, and another one under the keybox that will be accessible for when the axle or wheel need servicing or replacement. There will be minimal bracing– just enough to support the bridges, and something to prevent dry cracking in wintertime (something I have found is needed here in Minnesota — I’ve lost some mighty fine guitars to the dessicated air from December to February).

The top will vibrate freely. I am happy with how it looks in my mind’s eye.

 

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Keybox, third try

I recieved some feedback about the layout and spacing of the keybox vis-a-vis the wheel, and realized one more iteration would have a positive effect. I built a third keybox, and incorporated the criticisms; I also lengthened the outboard extent of the keybox so I could dress it up a little.  Instruments that look good sound better. I don’t know why, but it is so.

This week, time permitting, I will try to mount the wheel. Once that is done, I can figure out the top layout and bracing design.

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Layout coming along. I know how I’m going to support the wheel and keybox.

So I roughed in the keybox so it can be dry-fitted to the body; and also began installing bracework to support the wheel.

Tomorrow (time permitting) I will create the vertical brace the wheel bearing will sit in, and perhaps dry-fit the wheel. Once those items are all laid out, I can plan the top, its perforations, and its bracing.

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So the easy fun phase is ending, here’s where it gets tough.

Until now most of the stuff I’ve been doing has been very similar to building an acoustic guitar, which I have experience with. Now I’m getting to a new phase.

Today I slapped the first keybox together and realized:

  • the square holes are too small; the square rods would not have enough meat for the job they have ahead.
  • The 2 rows of holes are not far enough apart form each other, and the top row is too close to the top of the box.
  • I sill haven’t figured out how I’m going to make the ‘Talents’, the little fingers that press against (and fret) the strings when the keys are pressed. They have to be strong and solid, and also adjustable in the fore-and-aft and side-to-side dimensions, so the instrument can be intonated correctly.

So I made a second Key box, with bigger square holes, correctly placed. I’m going to need to brood about the talents for awhile. The ‘keeper’ is the one laying down. I’m still going to keep working the discard, so I can make fabrication mistakes on that one and then do things right on number 2.

That’s the way Design-Build goes. You have a good idea, you execute it, then you figure out it needs someting more. Fortunately this instrument is modular — more modular, say, than an acoustic guitar. I can make subassemblies and perfect them and if they don’t work, figure out what’s wrong and make something better.

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More progress: key box started

Today I drilled the square keyway holes for the keys to fit in, roughed in a wheel or 2 some more, and I have a nice pair of cedar blanks gluing up for the top. Progress!

With the loose parts all to hand, I can play around with how things have got to fit together, and from there I can figure out how the top bracing needs to be designed to support everything and still allow the top to resonate.

I’ll try and figure out the ultimate siz of the key box and begin assembling it. That will really drive a lot of other design decisions.

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The Back goes on the Hurdy Gurdy Prototype.

Not much more to say… so far the process has been straightforward because I’ve followed the same method as when I build acoustic guitars.
 
What comes next is going to require a lot of thought, because the placement of the wheel, scale length, keybox design, etc., are all intertwined and interdependant and I’ve never built one of these before. And the top bracing is going to be critical. There’s stresses that need to be dealt with that aren’t present in an acoustic guitar, and the elements on the soundboard that transfer the string energy (aka the bridges) are less like those of a guitar and more like those of a cello (for the chanterelles, or melody strings) and unlike either a guitar or a cello for the bourdons and trompettes (the high and low drone strings).
 
Once I have the box I can start laying pieces of wood here and there and laying it out in my mind. I suppose I’ll make some kindling along the way.

 

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Linings going in.

So in the end, I heated up the bows again and let them cook awhile, so unrelieved stresses would be resolved.

Using bent linings, as is my wont. One side done:

The other side is now set up and drying:

Because I may be experimenting with unusual tunings on this instrument, including some that are higher tension than the more common C/G that most players use, the additional longitudinal rigidity lent by the bent (as opposed to kerfed) linings may be of benefit.

 

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The ribs are in place. What next? I have to mull that over.

The beginnings of the body came out of clamps today and got trimmed down. I like the shape and size. It feels right.

I decided to add some additional reinofrcing blocks in the corners. The head end is going to be under a lot of stress when the key box is added, with the string tension. There’s a lot going on there, and I don’t want anything buckling.

Part of the problem, but also the fun, of design-build is that after each step you have to take stock and think about what you need to do next.

I’m thinking the obvious next step is to install linings. But that may not be optimal. I feel like there’s a lot of unrelieved stress in the bows. Maybe I’ll throw a steam jacket on them for awhile tomorrow just to let the wood relax a little. The linings can wait a day, maybe.

So I’ll let you know what I decide, after I sleep on it.

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I had to get going, I couldn’t wait

I bent the sides, and glued them to the end block.

The first prototype has begun. Design/Build is fraught with peril, but I have a good feeling about this. Tomorrow I’ll attach the for’ard part to another block.

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Hurdy Gurdy, man.

I’ve decided to build a Hurdy Gurdy. It will be quite a technical challenge but, I believe, do-able. Heironymous Bosch clearly regarded it as the devil’s instrument. That’s the only kind I build.

I bought a used Delta mortiser this week: it will let me make perfectly square holes for the key box. 24 keys, 2 holes each, that’s a lotta holes and they have to line up in pairs. So that’s good.

I got oak for the sides and key box. I have cherry for the back. I have cedar for the top.

.

The sound box, I’ll draw on my experience with making guitars. I need to make it resonant. I want it loud and with good tone.

Stay tuned.

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