At 08:01 PM 7/26/2006 +0100, you wrote:
Hi
To guess at a single cause of all the problems mentioned, I'd be inclined
to blame heat and low humidity. I've just got back from the oven they call
SaintChartier and noticed the geometry of my gurdies changing almost by
the hour. As you say, shimming works fine on chanterelles - you need
thicker shims for bourdons because of the different approach to the wheel.
The trompette can't be shimmed effectively so the best thing is to make a
taller one for use whenever the problem arises. Hot weather also makes
rosin more sticky and could be affecting the drone pitch. Try a harder rosin.
Neil
Hi Neil!
You suggested "heat and low humidity"; we don't get that combination much
in this part of the US. Did you mean *high* humidity? It's not too
terribly hot or humid right now here where I live on the coast. I use a
very hard, light colored violin rosin, and I don't know if I can get a
harder one.
But I'm interested in your idea about using a taller chien. Are you
suggesting a taller chien in order to reduce the pressure of the string
against the wheel? I ask because a taller chien could be made to
accomplish this, but it would also increase the downward force of the chien
against the soundboard. Why not a chien the same height as the current
one, but with the slot cut a little further from the plane of the edge of
the wheel? This may be splitting hairs, but I'm asking because in the
discussion about this problem a couple of years ago, there was confusion
about string angle in relation to the wheel edge and in relation to the
soundboard.
As I recall, Marcello suggested that the location of the string anchor
point would have an effect: the further away the anchor point is from the
centerline of the instrument, the more the tirant has to pull the string to
adjust the "buzzing" point of the chien. This angle of the string at the
chien relative to the instrument's vertical plane (perpendicular to the
soundboard) could affect the pitch. This is interesting because in theory
it doesn't effect the angle of the string relative to the wheel edge, and
therefore it doesn't effect the pressure of the string against the wheel.
Theo found that if he pushed a piece of cut-off pencil eraser under the
string near the anchor point, the pitch change could be varied; he changed
the angle of the string at the chien relative to the instrument's
horizontal plane (parallel to the soundboard).
But both Theo and I noticed that the pitch of the string only changed when
the chien was actually in motion, buzzing. While maintaining a steady
wheel turning speed, I found that if I held down the chien to prevent the
tapping movement, the pitch did not drop. Releasing the chien and allowing
it to buzz caused the pitch to drop again. This led to the possibility
that the string's effective vibrating length is actually increasing while
the chien is buzzing, which makes sense to me: when the chien is at rest,
the string's vibrating length is clearly between the ear and the
chien. But when the chien is moving *with* the string (buzzing), then it's
not so clear: the ear is still one end of the vibrating length, but the
other end may end up effectively being not the chien, but the anchor point
at the end of the instrument, or more likely, due to the damping effect of
the tirant's "sideways" tension, some point between the chien and the
anchor point. Which leads me to wonder about whether changing the mass of
the chien could effect the pitch change. Maybe, but the current chien
worked perfectly well before; its mass hasn't changed. This makes a strong
argument for a string pressure/tension issue. My brain hurts.
Has anyone given any further thought or study to this issue of the
vibrating length when one end of the string isn't always firmly anchored?
~ Matt
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Matthew Szostak - Hurdy-Gurdies
7 Grove Street
Camden, Maine 04843
phone: 207-236-9576
email: [EMAIL PROTECTED]
website: http://www.midcoast.com/~beechhil/vielle
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