----- Original Message ----- From: "Sarah Fox" <sarah@gendernet.org> To: "Pianotech" <pianotech@ptg.org> Sent: July 28, 2003 12:10 AM Subject: Re: Rib overkill > Hi all, > > Dumb question: > > In a rib-crowned soundboard, the spring action is in the rib. However, ribs > are made of wood, and wood eventually loses shape under constant pressure. > There have been experiments with steel soundboards, which don't quite sound > right in the treble end. But what about spring steel ribs of some sort? > Perhaps thin wooden ribs with steel leaf springs screwed to them, affixed > with a flexible adhesive to prevent buzzing. They wouldn't lose their > shape, for the most part, and could be engineered to whatever spring > constant is desired. Lot's more things to go wrong. Besides, in a rib-crowned soundboard system the ribs are quite long-lived. The stresses are moderate compression along the top of the rib and moderate tension along the bottom. This is what the wood fibers were created for and they handle the stresses quite well and for quite a long time. > > A related dumb question: > > When the treble needs stiffening (higher acoustic impedance and lower > compliance), that would be achieved by raising the spring constant. Why not > do that with coil assist springs between a frame element and the underside > of the SB beneath the bridge? An added benefit would be the offloading of > downbearing pressure that otherwise distorts the crown over time. (The same > downbearing is preserved between the string and bridge, insuring the same > efficacy of vibrational coupling.) > > Has anyone tried anything like this? Yes. There are several exchanges in the archives on this subject. There is not a large base of information as yet but it has been done with at least mixed results. That is to say, sometimes positive results, sometimes none. But at least none negative. (To the best of my knowledge.) Del Delwin D Fandrich Piano Designer & Builder Hoquiam, Washington USA E.mail: pianobuilders@olynet.com Web Site: www.pianobuilders.com
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