<html> <body> Ron - Seriously, thank you for taking the time to respond and for taking my questions seriously, mostly. It's so easy to get lost in semantics while just trying to put a few words together in a sentence.  Some of what follows might reiterate some of what Richard Brekne discussed in an earlier post, but I thought it would keep it simpler if I made my own comments here.  Please note that I don't expect you, Ron, to take on the responsibility of answering all the questions I raise.  In some cases the answers may be available from original sources, with a little more work on my part.  In others, the real hard data may simply not yet be available. At 07:22 AM 2/24/2004 -0600, you wrote: <blockquote type=cite class=cite cite><blockquote type=cite class=cite cite>How would you define "coupling", in this case?  </blockquote> The pin angle combined with the string tension and offset angle forces the string against the bridge top. It's a clamp system.</blockquote> This is a static definition.  What I was trying to ask  about was "dynamic" coupling, that is, the interaction of the parts (string, pin, bridge) in motion.  In fact, I probably DON'T want to ask about this right now, as it would likely bring us around to that discussion about how energy gets from string to soundboard.  I'm not ready to take that on. <blockquote type=cite class=cite cite><blockquote type=cite class=cite cite>Does the front edge of the bridge play any role in defining the string termination?  </blockquote> Yes. It's what the pin angle, string tension, and offset angle clamp the string TO, ideally.</blockquote> I meant, does the front edge of the bridge have any effect on the way in which the various modes of string vibration evolve & decay that might be measurably altered by its absence? <blockquote type=cite class=cite cite><blockquote type=cite class=cite cite>If so, how is that function affected by  no contact (string climbing pin)</blockquote> Strings don't climb pins unless something is severely wrong, </blockquote> You say "unless something is severely wrong".  What condition would qualify for that description?  What amount of negative force would be needed to overcome the design parameters you have quoted..."10 degrees side, 20 degrees pin slant"?  What if those parameters have been ignored, intentionally or otherwise?  The initial impact wave might have enough force to move an inadequately "clamped" string. <blockquote type=cite class=cite cite>but the termination edge is crushed by cyclic wood dimensional changes with humidity swings pushing the string up and down the pin. It's very possible for a string to be resting on the bridge top and not be touching the notch edge, but it hasn't climbed the pin. It's crushed the cap. </blockquote> This could be the case if the original downbearing was properly set and the pitch/tension was allowed to elevate with the increased humidity. Here are some sub-questions: <x-tab>        </x-tab>- What amount of pressure is required to crush maple cap material? <x-tab>        </x-tab>- In the normal stringing process, how much force is initially applied to the front edge as the tension is applied? I recall some discussion about the bridge surface itself expanding upward (apart from the soundboard's upward excursion) and, in the process, pushing the string up the pins.  If this occurred, and then, in the dry season, the bridge contracted, if the ratio of friction to force was high enough, the string could remain elevated from the bridge surface, even without attributing the cause to wood crushing or vibrational prodding.   <blockquote type=cite class=cite cite>At that point, the loose pin flexes and flagpoles and the false beat happens.</blockquote> I wonder at your conclusion, that he pin becomes loose and flagpoles, causing false beats.  I can't see that the pin necessarily becomes loose or that false beats are the resulting symptom.  My guess would be that the lack of bridge edge support allows a degree of movement between string and pin that would otherwise not occur.  At some point, in an instrument that has had a fair amount of use, that movement is taking place against an abraded pin surface, which could contribute to both the unwanted string noise and the string's ability to remain elevated. <blockquote type=cite class=cite cite><blockquote type=cite class=cite cite> In any case, it's hard for me to believe that you have not encountered innumerable examples of strings which visibly settle downward when tapped (gently). </blockquote> Of course. But it's because you're inducing a curve into the string to force it down to the crushed bridge edge by tapping, not because the string has climbed the pin.  </blockquote> Sorry, no.  I have, with a magnifier and strong lighting, watched the bridge-segment string set to the bridge surface from almost all the way back to the rear pin. It can't be all about wood fiber crushing.  Of course, as I get older, and my eyes get worse, I can reasonably suppose that I'll be seeing less of this. That's one solution! <blockquote type=cite class=cite cite><blockquote type=cite class=cite cite>It's the "clamping" concept I'm having trouble with.  If there is positive downbearing, the need for further clamping would seem somewhat redundant.  </blockquote> Except that's backward. That clamp provides considerably more coupling of string to bridge than does downbearing. Try to pull a string up off a bridge. Now pull the bridge pins, tune it back up to pitch and try again. Without the pins, there's not much keeping the string on the bridge. </blockquote> Maybe.  Again, it's the confusing of clamping and coupling that bothers me.  The example of trying to pull the string off the bridge would seem to suggest that the string in vibratory motion is trying to do something similar...that the clamping action is causing the bridge to follow the motion of the string.  Clamping TO THE BRIDGE SURFACE would appear to have a very useful purpose in the case of zero or negative downbearing. <blockquote type=cite class=cite cite><blockquote type=cite class=cite cite> So, what are your concerns with negative downbearing?</blockquote> Overall downbearing in a conventional design: The soundboard isn't compressed, so there will be an impedance mismatch between the board and string scale (killer octave). The coupling between the bridge is compromised. Not eliminated, but less positive. The piano typically sounds lousy there.  Ron N </blockquote> From the rebuilder's perspective, and not just Ron N, : Are you striving for positive downbearing  (with positive front bearing) across the scale? If so, do you know (by measuring) how often you do or do not achieve this goal?  If you are willing to accept some areas of negative downbearing, are there locations on the board where its presence would be more likely to have a deleterious effect? It's been fun - truly! David Skolnik RPT, DBH </body> </html>