Bridges: Chew on this

[McNeilTom@aol.com]

To Jim Harvey -

I understand you are describing and questioning the direction the string jogs
when crossing the bridge.  And, of course the direction of the jog must be in
the same direction as the downward slant of the bridge pins.

I think I was not clear enough in my earlier post where I recommended
slanting the bridge pins downward toward the middle of the bridge.  Let me
try again.

Assume we're dealing with a three-string unison in the mid-range of a
medium-sized grand, and we're inventing the bridge from scratch.  In
conventional practice, we would drill for the front row of bridge pins by
drilling down and to the right (leaning the top of the drill to the left); in
this case, the strings would deflect to the right as they cross to the rear
row of bridge pins, then turn left as they continue on to the hitch pins.
 (The rear row of bridge pins would lean in the opposite direction of the
front row, per usual.)  In the ideal scenario, all three front bridge pins
would be parallel and in a vertical plane; they would also be in the same
plane as the line of the bridge notch for this note; this plane would be
perpendicular to the speaking lengths of the strings as well.  The question
would be, should the front row of bridge pins lean left or right, not fore
'n' aft.  The answer is, I believe, that the front row of pins should slant
down to the right (leaning the drill to the left); in this way, the bottoms
of the pins will be somewhat closer to the center of the bridge's width than
the tops of the pins are; this is a stronger construction than leaning the
pins the other way, with the bottoms pointing somewhat outward, toward the
edges of the bridge.  The difference would be most dramatic in the tenor
region of a long piano, where the bridge is running more nearly fore 'n' aft.
 And the difference would be least dramatic in the high treble where the
bridge runs more nearly left 'n' right; even here you might as well angle the
same way, for the same reason, and for uniformity with the rest of the piano.

I don't think I've ever seen a grand bridge organized otherwise, although I
suppose it could be.  An upright, when lying on its back, will usually
(always?) have its pins leaning in the direction opposite the grand's pins.
 The same considerations prevail, but the bridge curve is in the opposite
direction compared to the grand.

Hope I haven't confused the issue more in trying to describe this principal.

- Tom McNeil -
Vermont Piano Restorations

P.S.  I agree with Don Mannino's comments, too.