At 2:00 PM -0600 12/23/01, Ron Nossaman wrote: > >In my post with the topic "Rocking Bridges", to which at the time of >>writing you have not yet responded, > >Nor is there any reason for me to. With you maintaining that a string >deflected by a finger will move the bridge but one deflected by a hammer >strike won't, I see no point in continuing. Then you will have the leisure to watch your theories discussed in your absence. I relinquish this thread with a selection of quotations which indicate to me that my summing up of your position, which you refuse to confirm, is correct. It seems to me a fair summing up. I will now proceed to the Rocking Bridge question under a thread with that subject line. JD At 7:09 PM -0800 12/3/01, Delwin D Fandrich wrote: >As I said, it moves the bridge. Primarily in a vertical mode (assuming a >grand piano), but there is some fore-and-aft rocking as well. How much >depends on the design of the bridge and location on the scale. More in the >bass than in the treble. > >The bridge movement moves the soundboard causing it to vibrate much like the >diaphragm vibrates in the loudspeaker. At 5:42 PM +1100 12/19/01, Overs Pianos wrote: >In a situation where the down bearing angle is in the back length >only, 'bridge rocking' (yes it will be minute also JD) will be >necessary for the minute dynamic variation in speaking length >tension to result in a commensurate variation in the down bearing >vector force. >I read your well conceived response earlier today Ron soon after you >posted it. I too have described the motion of the string and its >resultant dynamic forces on the bridge in exactly the manner in >which you describe it. I understand what you're saying and agree >with you. At 1:48 PM -0600 12/22/01, Ron Nossaman wrote: >All sorts of compression waves and molecular level stress disturbances can >be immediately moving through every part of the bridge from the first >movement of the string, but they're clearly not what moves the bridge. The >strings move the bridge, the bridge moves the soundboard. At 5:42 PM -0600 12/16/01, Ron Nossaman wrote: >Then I fail utterly to see how the soundboard can move without the bridge >moving At 8:00 AM -0600 12/18/01, Ron Nossaman wrote [ridiculing JD's position]: >Meanwhile, the unchallenged fact that the bridge does move has >little or nothing to do with sound production, but it's definitely >not the string movement that is moving the bridge. At 4:47 PM -0600 12/18/01, Ron Nossaman wrote: JD: >>Under these conditions the bridge cannot be moved by the strings, >>since a body only moves in reaction to a force and in these >>circumstances there is a zero force acting on the bridge. RN: >It doesn't matter if it's possible or not. Regardless of whether the >strings are moving in the same or opposite directions, there will be cyclic >changes in string tension as the vibrating strings pass from their far >limit of excursion, through a relatively straight line neutral, to the >other far limit and back. The tension swings will necessarily pull the >bridge forward and back, and the bearing load changes will push it up and >down. The bridge will move, and the soundboard will follow. At 5:05 PM -0600 12/18/01, Ron Nossaman wrote: >I'm to judge what happens in the bridge before the soundboard moves? Isn't >that basically the problem with this discussion? This isn't even >conceptually possible, much less arguable. What you need is >instrumentation. At 8:29 PM -0600 12/18/01, Ron Nossaman wrote: >I don't know why the difference in sound. I also don't know why, if the >energy goes directly through the bridge without moving it, and into the >soundboard which then moves, why touching the fork to the exposed edge of >the soundboard won't produce the same tone as pressing it against the top >surface. At 10:35 PM -0600 12/19/01, Ron Nossaman wrote: >When these compression waves supposedly travel down through the bridge to >the soundboard, moving the board before the bridge moves, how does this >manage to happen with the board attached to the bridge at exactly the spot >that these waves are supposed to move the board? At 8:09 AM -0600 12/21/01, Ron Nossaman wrote: >I have never denied the existence of compression waves >in strings and soundboards. What I have said, and still say, is that they >are not the principal driver of the system. At 6:06 PM -0600 12/21/01, Ron Nossaman wrote: >You see, the strings moving the bridge is my own theory, dreamed up >by me, based on sound mechanical and physics principles, so it isn't >likely to be on a university web site anywhere. Oddly enough though, >two piano designers, builders, and fellow rebuilders who have >against all apparent odds actually given it some thought, seem to >hold similar views.
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