Building yet another hurdy-gurdy

[Yuri Terenyi]

Well, looks like it's hurdy-gurdy time.
I got an order for a really minimalistic one. The idea of course is to make it for as little as possible. On the other hand, the customer is a music student (hence not much money to throw around), and a musician. Emerging from this last attribute is the need for a real instrument, not one of those kits that end up at the back of a garage.
Now, having built some three or four, I cannot be called exactly an old hand at this sort of instrument, but on the other hand, they work rather nicely, even if I say so. So the idea for this one is to make an instrument that is really truly minimalistic, but as dependable and smooth running as I can possibly make for the most expensive one I would undertake.
So as a result of all this musing, there will be a lot of unusual solutions and "innovative" things thrown in. (I rather dislike the word, hence the inverted brackets.)
The instrument will be made in bursts of activity, interspersed by periods of no activity of various lengths, when I'm doing some other things. So don't expect a continuous flow.
To begin with, all the body parts and some of the keybox will be made from Macrocarpa. There is a thread in the wood section on it. In the US known as Monterrey cypress, it has been planted around New Zealand as a windbreak tree, so there are oodles around. Very cheap, too.

[Yuri Terenyi]

First photo is the endblock sitting on the back plate. The endblock already bored out for the shaft, the inner hole to take the bearing, the outer one just a mm or so wider than the shaft itself.

[Yuri Terenyi]

The angle of the endblock v. back plate is obvious.
Here is the first thing I changed. The norm for flatback gurdies is to build the instrument perpendicular to the bottom plate. The result being that all the shaft hole boring has to be calculated very carefully, as all the bearings sit at an angle to the perpendicular. My way all I have to do is angle the bottom plate, and everything else needs boring is bored at 90 degrees.

[Yuri Terenyi]

The mock-up of the endblock, two sides and a connecting element that will define the width in the front. No gluing has been done yet. The sides are another not-quite normal thing. They are rather thicker than what would be considered normal. More of a clavichord or harpsichord sort of solution. However, this way the structure will be as strong as can be without much strengthening from any other source.

The endblock is drying now; to be continued.

[Yuri Terenyi]

The endblock, front, er, block (you'll see what it is soon), and the back braces glued in place. The two rear braces drilled half-way through to take the soundposts, though these play a different role from the usual bowed instruments' ones. The one going to be under the main (chanter) bridge is offset, which is another unusual feature. Normally they are in the center, with an oversize hole letting the shaft pass through.

[Yuri Terenyi]

The same, with the sides recessed to take the ends of the three braces. (I could have done the front one, the one that is glued to the front block, as well, but didn't. Don't really know why.) I'm not sure it really is necessary, but, hey, I want a really sturdy instrument!

[Yuri Terenyi]

This is the view inside when the box is put together dry.

[Yuri Terenyi]

The final shape is starting to emerge... Still totally dry, the whole thing.

[Yuri Terenyi]

The flowerbox is taking shape...
Bottom, sides and pegbox (without the top, obviously) trimmed. The top of the sides (the part to take the top braces and the soundboard itself) is still about 1mm higher than when finished.

[Yuri Terenyi]

The bearings. (Only one shown step-by-step.)
Now, here's another thingy that would set normal makers scratching their head.
To start with, there is a timber called lignum vitae. Now, among other things it is used for bearings of boat propellers. So I figured, if it's strong enough for that, surely it will be good enough for a pitiful gurdy shaft. The way to do it is to have the end grain facing the shaft hole. In a small bearing like this, four pieces are the maximum you can use. In boat bearings they use more.
So it's the rough state, with bits of what the wood came from, then a trued-up shot, drilled out, and finally turned down. The turning has to be done really carefully, as the grain is all wrong. Only sraping cuts used, and some pointy chisel. In fact, it's more like metal turning than wood. I turned it squeezed between two cones, the driving cone being just a turned wooden one gripped in the jaws of the lathe.

[Yuri Terenyi]

Finally (for today) the back bearing in place. Just pushed in with reasonable finger pressure. And a 10mm shaft passed through it, to check that it has not deviated from the centreline.
By the way, why lignum is used is partly because it is self-lubricating.

[Jon Whitney]

I'm starting to think about building a hurdy-gurdy or two after I finish my current banjo projects. Are you working from a published plan, or is it your original idea? I'll be watching this thread with interest.

[Yuri Terenyi]

It is my own.
I mean, once you get the idea of the mechanics right, the rest is just decoration... You need the string length, key work and suchlike right, but things like the shape of the body and what not are optional, really.

[Steve Senseney]

Your pictures do make it look seductively easy.

[Yuri Terenyi]

The upper braces in place. I had to slightly shift the one with the bearing to the left, about 1 mm, because I stuffed up the centrepoint of the hole housing it. I suspect the end block is very slightly off 90 degrees, by perhaps half a degree or so. So the brace had to be cut shorter on the left, and shimmed up on the right.
Well, Steve, this is a very much easier way to make it than the usual. No bending, and only two angles to consider, the sides/centreline and the back's own. In reality I could eliminate the last one, too, and have the back parallel with the soundboard, but you have to have some style, you know. For that matter, it's perfectly possible to have the sides parallel, too, but then you end up with really just a flowerbox...
The last photo (Or perhaps the first, I didn't get the hang of it, they tend to appear in reverse of the sequence of uploading them) is the incredible nanotechnology tool that makes the top being flat possible. It's a flat piece of plank with double-sided tape holding (on this side) rather coarse sandpaper, and on the other side fine grade. When you use it on the braces, put earmuffs on, as they tend to SCREAM.

[Yuri Terenyi]

Later in the day...
I decided that the gluing area is not really big enough on the pegbox, so added a couple of liners.

[Yuri Terenyi]

Now, the wheel.
4 Layers of some unidentified marine grade plywood. Feels much like Philippine mahogany, or similar. Quite porous, and has a rather distinctive smell when worked. Altogether some 17mm thick (should be 16 in theory, but there you are.) Now, I still haven't decided that that is the right thickness. Thing is, wheels can vary from some 9-10mm thick to whatever. I really would have to go through museum data to figure this all out. But the basic idea is- the thicker the wheel, the stronger the sound. It is sort of logical, as the larger surface is in touch with the string at a given time, the stronger the string is excited. Still, 17mm could be a bit of an overkill, even though the gurdy is destined to be used for busking a lot of the time. With no amplification.
The unit in the centre of the wheel is turned from rata, a native NZ wood. Extremely hard. It's going to be screwed to the wheel on the flat side, and to the shaft on the protruding bit. A bit bulkier than the same in brass, but I don't work with brass, and don't have any, in any case.

[Yuri Terenyi]

Oh, everything is held together by pressure only, nothing secured yet. The wheel is yet to receive a rim. That will be made from pear.

[Jon Whitney]

I wonder, how practical it would be to adjust the practical thickness of the wheel by crowning or beveling the rim?

[Nicholas Blanton]

I like the idea of using lignum vitae for a very, very small propeller bearing in a hurdy gurdy. I have seen the very,very big ones- or, a few salvaged pieces of one- and it always seemed like a great idea.

How will you put on the pear? Will it be a veneer wrapped around the plywood, with a long-tapering joint, so you don't get a "bump" every revolution ?