---------------------- multipart/alternative attachment >How would you define "coupling", in this case? The pin angle combined with the string tension and offset angle forces the= =20 string against the bridge top. It's a clamp system. >Does the front edge of the bridge play any role in defining the string=20 >termination? Yes. It's what the pin angle, string tension, and offset angle clamp the=20 string TO, ideally. >If so, how is that function affected by 1) no contact (string climbing=20 >pin- see next quote Strings don't climb pins unless something is severely wrong, but the=20 termination edge is crushed by cyclic wood dimensional changes with=20 humidity swings pushing the string up and down the pin. It's very possible= =20 for a string to be resting on the bridge top and not be touching the notch= =20 edge, but it hasn't climbed the pin. It's crushed the cap. At that point,=20 the loose pin flexes and flagpoles and the false beat happens. >2) glancing contact with no force Same as above. >3) some downward pressure? At a certain point, enough pressure will be generated at the edge to=20 prevent the pin flagpoling. > If it does not, does it have any function other than supporting the=20 > bridge pin? The cap supplies the other half of the clamp, as well as supporting the pin. >Are you saying that a string riding up a bridge pin would require BOTH=20 >negative downbearing AND near-straight bridge pins? Probably, in a typical situation. It would take a whole lot of negative=20 bearing to pull a string at a 10=B0 side bearing up a pin that's slanted= 20=B0. > In any case, it's hard for me to believe that you have not encountered=20 > innumerable examples of strings which visibly settle downward when tapped= =20 > (gently). Of course. But it's because you're inducing a curve into the string to=20 force it down to the crushed bridge edge by tapping, not because the string= =20 has climbed the pin. >It's the "clamping" concept I'm having trouble with. If there is positive= =20 >downbearing, the need for further clamping would seem somewhat redundant. Except that's backward. That clamp provides considerably more coupling of=20 string to bridge than does downbearing. Try to pull a string up off a=20 bridge. Now pull the bridge pins, tune it back up to pitch and try again.=20 Without the pins, there's not much keeping the string on the bridge. >If there is negative downbearing, and thus, no bridge loading, what is=20 >the purpose of clamping the string to the bridge surface? Because the bridge surface is there and handy for such a use, and the=20 traditional pinning method is relatively effective, cheap, and easy to=20 build. And since negative bearing in a conventional system isn't a=20 desirable condition, it isn't useful to use it as a standard by which to=20 justify the rest of the configuration. >Wouldn't the vibrational energy be conducted to the bridge by the pins,=20 >even without the bridge surface contact? Yes. If they supplied a positive and rigid enough clamp, they would then=20 become an agraffe. In a conventional system that isn't in structural=20 failure, the string is contacting the bridge top. >My problem with the concept and terminology of "clamping" is that it=20 >encourages an image of the string exerting a vertical pulling and pushing= =20 >force upon the bridge, which I believe is inaccurate. How can you reconcile this belief with the belief that strings climb bridge= =20 pins? What supposedly gets them up there? Believe what you like, but the=20 string does exert a vertical pushing and pulling (or lesser pushing) force= =20 on the bridge. >Good. So, what are your concerns with negative downbearing? Overall downbearing in a conventional design: The soundboard isn't=20 compressed, so there will be an impedance mismatch between the board and=20 string scale (killer octave). The coupling between the bridge is=20 compromised. Not eliminated, but less positive. The piano typically sounds= =20 lousy there. Ron N=20 ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/a9/ae/1d/6d/attachment.htm ---------------------- multipart/alternative attachment--
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