Hurdy Gurdy

A hurdy gurdy build diary

This page will endeavor to show the building of a Bosch model hurdy gurdy, from the Marcello Bono drawings.
I am already indebted to Marcello and many others for their help and support in this project, much of it offered via the Hurdy Gurdy mailing list run by Alden and Cali Hackmann (see the links page).
I will attempt to refer to parts by name and by their part number as shown on the Bono drawings as I go.

May, Whitsun Bank Holiday (and Chippenham Folk Festival):

Mould and blocks

Mould and blocks 2
1. Mold complete, made of jelutong.

2. Bottom/tail block (Part 2b) of maple, and top/head block (Part 2a) of spruce.
3. First rib/side piece fitted and glued, (Part 9).

The construction on the bottom/tail block means that no clamping is necessary to hold the rib in place, only at the top/head block. The small piece of paper visible in this photo is to prevent the instrument body being glued to the mold.

The sides are bent using a cello bending iron, an oval block of aluminum, 6" tall, with two 175W elements inside controlled by a rheostat.

I am using animal (or bone) glue throughout, unless otherwise stated.
Gluing side piece
Sides complete

Sides complete 2
4 & 5. Both ribs completed.

I have not used the rib/side template provided on sheet 2 of the drawings as I prefer to build the instrument body 'square' to itself, and then take shape and measurements from centre lines and parallel edges. Hopefully this will work out satisfactorily.
6. The instrument is now upside down, and this photograph helps show the curvature of the back, achieved by careful measurement and the use of a block plane. Tail block curve
Gluing linings 7. Fitting the back linings, (Part 10).
I made the linings of spruce, and bent them to shape in the same way as the sides/ribs. The clamps being used here are cello lining clamps, and clothes pegs.

I found I needed to add a fillet of lining up to the tail block as the linings otherwise are attempting to follow a compound curve. This might be possible to introduce if the linings are made of willow, but not spruce.
8. All three back support struts (Part 11), made of quarter-sawn spruce; actually cut from old piano soundboard struts.

9. The back support struts rebated into the linings. This isn't specifically shown on the drawings, but seems the strongest method of fitting this part.

10. The body is now ready to receive the back plate; in this state the instrument now has a fair degree of rigidity, but I have left the mold inside the body to ensure the shape is properly maintained.
11. The back plate during gluing - I found I could only glue a comparatively small section at a time.
Again, I am using violin makers materials, this time, cello side clamps.
12. This may seem obvious, but cut the back to shape several millimetres oversize for gluing, then trim back when it is finally fitted.
13 & 14. Back and sides complete - back plate trimmed to size.
Note the pins (3mm dowel) for holding the back plate in position while gluing - this isn't really necessary on the back, but it does stop any sideways movement when applying clamps.

All three upper support struts, with a pilot hole drilled into Part 15A for the shaft bush (Part 3).
Strut 15C has a clear hole drilled for the shaft too.
  The soundbox complete except for the front. The upper linings (Part 14) are fitted exactly as the lower ones, in spruce again - note the three soundposts (Part 12), also in spruce.
Part 16 is just visible to the right of the top block, fitted as extra pinning strength for the peg box supports (Part 19).

Metal parts, separated and together.
  Wheel, with metal carrier, secured with 4 wood screws. The outside edges still require finishing on a lathe, and the final outer band added.
  All holes drilled, the inner bush (Part 3) glued in its support strut, the end bearing (Part 4) threaded into the tail block, and the axle and wheel set up.
  The front cut, oversize, again, from 3.5mm spruce (guitar timber). To achieve the required curvature in the front, 'paint' with clean water on the outside face and wait about 15 minutes. Glue up while still wet, as the front will dry out flat again.

The keybox under construction and complete.
All parts are 6mm maple - the two sides are taped together to mark out the key slots, which were then cut by first drilling through, then opening out with chisels and knifes.
  The peg box, complete. All parts again from maple; the heavy marks in the drum are water staining from air drying the timber.
The box was made by first turning a 120mm diameter block, then taking out the centre to leave a 6mm walled drum. Removed from the lathe, the face of the drum was then cut to the required angle, and the 15mm top face glued on oversize. The whole assembly is then put back on the lathe and the top turned down to the same diameter as the drum, which is then cut off the lathe at the appropriate length.
Note: PVA waterproof glue was used to join these two pieces of wood, as (1) it won't melt when a cutting back on the lathe, and (2) this glue doesn't 'grab' on the lathe like some other harder glues.

Pegbox, keybox (with lid and fastening toggle), and keybox supports (Part 19) glued up. Note the small (3mm dia.) dowel through the end of the keybox support into the side and Part 12 [inside the instrument].
Underside of the pegbox and keybox, showing (only just) how the keybox supports are let into the pegbox side.
The underside of the Keybox lid, of birdseye maple, showing the routed-out space and brass hinge.
This photograph attempts to show the main stages of cutting the tangents, right to left:

1. A strip of 9x4mm maple, with a square 'peg' of 4x4mm cut in its end.

2. The 'peg' rounded, by use of a draw plate - a steel plate with a series of holes drilled through in 0.2mm increments. The square peg is tapped into each successive hole until the required diameter is achieved.

3. The tangent head is shaped by knife and filing.
The first key, with tangents fitted in its place.
This also clearly shows the bridge support and separator.
Please excuse the lack of true continuity in the photographs at this point - progress was seemingly rapid and productive, at the expense of getting the camera ready.  
The wheel and its banding.
The wheel is made of 12mm birch ply as its core, due to the evenness and stability of this particular plywood, plus a 0.5mm sycamore veneer on either face.
The wheel is then trued up round on a lathe (infact on the shaft, in the lathe), and the banding added.
This [the banding] is a 14x3mm strip of holly, bent with lots of heat and water, then held in place with a 'jubilee clip' or hose clamp, (actually two clips together). The upper photo here clearly shows the scarf joint where the two ends meet.
When dry, the wheel is put back on the lathe and the holly band cut back to fit the wheel and correct diameter.

Main bridge(Part 30), from sycamore.
This needs to be fitted like a violin bridge, that is, cleanly to the contours of the front or soundboard, where it is glued (unlike on a violin).
Gluing will mean scraping the finish from the instrument where the bridge feet fit the front.

Rather a lot has happened by the time this photo was taken:

tailpiece (Part 32), of birdseye maple, fitted and doweled through the font

tenor bridge fitted (Part 38), simply glued

trompette bridge (Part 35), fixed part, glued

bridge fitted

wheel cover brackets (Parts 39) fitted, glued

and it's finished, mainly in shellac.

Fitting up the chanter strings.
The two top nut bridges, Parts 26 A and B, are made a tight fit inside the keybox sides, but left unglued so as they can be moved later while tuning the strings.
I was unable to agree with the drawings showing the alto drone (mouche, Part 20C), running the entire length of the keybox without using the top nut. I calculated that it would foul either the bridge, or the first few keys, therefore my alto drone uses the the inner top nut (Part 26B) just as the second chanterelle does.

The wheel cover and its mold, from jelutong.

The cover is made up of three laminates of 0.5mm veneer, plain sycamore for these layers, and finished with a final 0.5mm veneer of birdseye maple.

... apart from the following modifications.
The revised handle shape, turned down and made smaller..
The original shape, as drawn, was too round and it was difficult to apply the 'coups'.

Peg to lift the trompette string off the wheel; 6mm in diameter, and glued into the front (soundboard) and the support strut underneath.
Brass rod hooks to take out the chaterelles and the alto drone strings, as above, for tuning.
All parts need to be highly polished so as not to abrade the strings when being used.

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