---------------------- multipart/alternative attachment David Love - Thanks for responding. I haven't forgotten that you started all this with= =20 your Negative Bearing question a few years ago. Let's see if I can keep=20 this on track long enough for me to understand. To simplify things a bit,= =20 can we agree to acknowledge, then ignore the fact that we cannot determine= =20 the original bearing set up from measuring the strung piano? Why does there= =20 appear to be this growing consensus that these "after stringing"=20 measurements are deceptive, confusing, and of no value? Whether or not the= =20 board is being compressed (i.e. stiffened) by one area of the string=20 scale, if I get readings showing zero or negative downbearing in a section= =20 of the piano, is it to be dismissed because there is downbearing SOMEWHERE= =20 on the board? With regard to transfer of vibrations, can you, David, or anyone else,=20 direct me to recent discussion that supports this view of the irrelevance=20 of downbearing in this process? (I will scan the past years posts if you=20 cannot.) If such is, in fact, the case, and if you could create the=20 hypothetical soundboard with sufficient stiffness WITHOUT employing=20 downbearing's compressive function, is there, in your opinion, ANY aspect=20 of the mechanical transfer of energy from string to bridge ( & board) via=20 bridge pin, that would suffer in the absence of such downbearing? For=20 example, if the string were to traverse the bridge, captured by the pins=20 (horizontally) , but at 1/16th or 1/32' above the bridge surface? And what is the nature of the coupling you speak of? (Bridge translating=20 string impulse) What is the implication regarding the way the string=20 energy transfers from string to bridge to board? Did I miss the resolution= =20 to that question? Sorry for all the questions. David Skolnik At 07:25 AM 1/30/2004 -0800, you wrote: >The transfer of vibrations happens due to the coupling of the string to=20 >the bridge, not due to any downward pressure of the strings onto the=20 >bridge. That coupling is achieved by the interlocking of the string=20 >through the bridge pins . Whether or not you have downbearing will not=20 >influence this coupling. The downbearing effects the amount of downward=20 >pressure on the soundboard. When the board is compressed it gets=20 >stiffer. The more stiff it is, the greater the impedance (the panel's=20 >tendency to resist the transfer of vibrational energy). The treble end of= =20 >the board needs to be stiffer than the bass area. The relative narrowness= =20 >of the board in the treble region combined with more downbearing at that=20 >end produces more stiffness. The measured bearing can be confusing=20 >because you set the bearing with the board only minimally compressed (or=20 >not compressed at all depending on your technique). The amount of=20 >measurable beari! ng after the board is strung and loaded will be=20 >different than before it is strung. You can't really tell after the board= =20 >is strung and loaded what the bearing was at the outset. The tone of the= =20 >board will be influenced by the board's response to this downward pressure= =20 >and whether it achieves through design and execution the proper impedance= =20 >characteristics throughout the scale. > >David Love ><mailto:davidlovepianos@earthlink.net>davidlovepianos@earthlink.net > > >----- Original Message ----- >From: <mailto:davidskolnik@optonline.net>David Skolnik >To: <mailto:pianotech@ptg.org>Pianotech >Sent: 1/30/2004 3:10:21 AM >Subject: Re: No downbearing ? REVISITED > >Almost one month ago, this a question regarding downbearing was raised: > >At 04:09 PM 12/31/2003 +0100, Jean-Jacques Granas wrote: > >>I have come across a puzzling suggestion a few weeks ago: Namely, that=20 >>downbearing is not really necessary in order to transfer the vibration of= =20 >>the string to the soundboard panel, the mere "grip" that the string has=20 >>on the bridge being sufficient to assure this transfer. Would anyone of=20 >>you with experience in such issues care to comment? > > >Then, At 10:48 AM 12/31/2003 -0500, John Hartman wrote: > >>Yes I believe this is correct. Bearing does not directly influence the=20 >>transfer of vibrations. What it does is alter the apparent stiffness of=20 >>the Soundboard and thereby help to control the rate at which the=20 >>vibrations move from the strings into soundboard. Check the archives for= =20 >>soundbaord impedance. > >Then, At 05:25 PM 12/31/2003 +0100, Isaac sur Noos wrote: >>I should say that indeed downbearing is not indispensable, but on most=20 >>pianos, front bearing particularly produce a more pleasing (fuller) tone. >> >>Bearing being not discernable after the strings have been installed, it=20 >>is often confused with "distance bearing" which indeed is the proof that= =20 >>some pressure exist when it is seen, but on some pianos the soundboard=20 >>look flat after the strings have been tense (while down bearing exist=20 >>absorbed by the soundboard) . >> >>All depend of the kind of ribbing and construction used (flat ribbing vs.= =20 >>crowned ribbing). Most German made pianos are using flat ribs and are=20 >>very sensitive to humidity changes when the soundboard is in good=20 >>condition, so the go out of tune easily in that case. these instruments=20 >>need less down bearing than the ones which are u! sing crowned ribbing=20 >>(B=F6sendorfer for instance). >>The flat ribbing method "is said" to produce stiffer soundboard assembly,= =20 >>while curved ribs need to be pressured more to obtain the necessary=20 >>stiffness. That is what I have understood, very crudely I confess, from= =20 >>the different conversations on those matters. > > >By the second (Isaac sur Noos's) response, what was a potentially=20 >illuminating or controversial discussion, was re-routed to yet another=20 >review of crown and the crowning process. None of the subsequent=20 >contributions sought to address the original question (in fact or in=20 >spirit), or to clarify John's response. Here is some of what I felt was=20 >missing: > >Jean-Jacques, what was the original source of your 'puzzling=20 >suggestion'? (previous posting?) The mere "grip" , as you described=20 >would, presumably, refer to the side bearing of t! he bridge pins. This=20 >would seem to promote the theoretical conclusion that the energy is=20 >channeled from string to bridge exclusively by the bridge pins; that the=20 >function of the front edge of the bridge top may simply be to limit the=20 >downward excursion of the string. Does it have any role in creating a=20 >reflective terminus of the string? And if so, how much force is required=20 >to prevent (or control?) energy leakage to rear string segment? Is it=20 >presumed that the transfer of energy would be unaffected by the presence= =20 >of either positive bearing, no bearing, or, for that matter, negative=20 >bearing, as long as the bridge pins held onto that string,? > >John's response is, I think, unintentionally misleading. He first suggests= =20 >that Jean-Jacques's statement is correct, but then immediately attributes= =20 >to downbearing the [important?]ability of controlling "the rate at which=20 >the vibrations move from the strings into s! oundboard". If there is a=20 >point of differentiation to be made here, it seems inordinately subtle,=20 >compared to the resulting impression conveyed that downbearing is not an=20 >essential component in piano design and engineering. Unless that is the=20 >meaning that is intended!? > >Finally, before Isaac Sur Noos directed the discussion towards crown, he=20 >made some comments which, if I understand them correctly, are additionally= =20 >confused: >>I should say that indeed downbearing is not indispensable but on most=20 >>pianos, front bearing particularly produce a more pleasing (fuller) tone. > >To summarize then, downbearing isn't essential, unless you want the piano= =20 >to sound good.?? > >With regard to downbearing being discernable, or measurable (see quote=20 >above)... what IS measurable is, as he puts it, distance, or string=20 >deflection, I may not be able to tell how much the board has flattened in= =20 >response to X amount of original downbearing, but if there is no=20 >measurable deflection, there is no downbearing. Is this not true? > >Thoughts? > > >David Skolnik > > ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/9b/d4/74/87/attachment.htm ---------------------- multipart/alternative attachment--
This PTG archive page provided courtesy of Moy Piano Service, LLC