Friday, May 21, 2010

More Shawms - staples and tuning

The staple is the thing what holds the reed, and launches its sound down the bore.  In these shawms, I made the staples quite separate from the body, so that I could tinker with construction details and make mistakes without writing off a lot of work.

I have not seen this arrangement in any old images or modern reconstructions of shawms, but there is no modern construction technique required, so it could have been used in period.

Remember the kumihimo bobbins from earlier?  Never mind.  Here they are again, with one end turned down to shawm size (about 30mm diameter), and the unwanted end removed and a rebate turned in the body which is now about 15mm diameter.  There's also a 3mm hole through the middle down the drill press using the flat end as a reference (which still managed to emerge slightly off-centre, grumble). 

The guts of the staple is a metal tube.  I made this one by wrapping thin copper sheet around a 4mm file. One end needs to have a taper in it to match that of the reeds being used.  I am using bassoon reeds, in the absence of anything better (more on this later), and I made a mandrel to match the reeds' taper by filing down a steel bolt in the drill press.

The other end of the tube needs to match the bore of the body reasonably well, so that there not too much discontinuity between the staple and the bore.

These are conflicting requirements, and are not easily met in a single piece of tube - well, not one that I can readily make, anyway.  I made these staples in two parts, each with the requisite taper, or lack of it.

The two pieces of rolled copper are sprung together, heated in a soft gas flame and a small amount of solder flowed in to hold them.  The trick is to keep the amount of solder "small", i.e., put on what looks like an inadequate amount and trust that it will flow all the way to the end of the seam.

With a 16mm spade bit, it was the work of only a minute or two to form the socket in the top end of the body of the shawm.

With a serving of linen, generously dosed with archers' wax (mixture of beeswax and rosin - sticky stuff), the staple is ready to fit, as seen here.  The shawm and staple seem to have acquired a coat of shellac since the last photo, as well.

The straight part of the staple tube is a snuggish fit inside the bore of the shawm.  I "glued" the tube into the body of the staple with some thick shellac, which took rather longer to set than I had expected.  If I use this staple design again, I would use straight rosin or pitch or even hot-melt glue to fasten the tube.

The next step is tuning the shawms, to be told in the next post.

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