Doug Richards wrote: > Del, > > I don't know if I buy that. Is the plate in or out? Regardless, my gut > says it would take a very large force from the pipe clamp to measure a > difference in crown. I think the sound board is constrained all the way > around, but a force outward will not necessarily "suck" the crown out unless > the force is HUGE (my gut feel only). That is my point. The rim does not support crown except -- and then only maybe -- in a very minor way. Loss of crown does not mean that the rim has moved. And moving the rim will not 'restore' it. Ok. I suppose that if it were possible to pull the rim in or out quite a lot -- 3 or 4 mm or so all the way around the soundboard -- you could significantly alter crown, but you would also introduce a lot of distortion. It wouldn't exactly be beneficial to the health and well being of the piano. > I have an idea. Since you do soundboard replacement, I'd propose an > experiment: > > 1. Take a soundboard has been crowned before installation, lay it on a flat > surface and "somehow" measure the force/deflection rate. > > > 2. Repeat the force/deflection measurement after the board is glued in > (with the plate installed). > > 3. And since I have an outline of a soundboard for a FEA prediction for > simply supported Vs constrained, I have no excuse. We can compare notes. > > What do ya think? > > Regards, > doug richards ---------------------------------------------------- With which type of soundboard? We use only rib-crowned boards. I haven't tried this as any kind of controlled experiment, but I have a general sense of how stiff our boards are before they go into the rim. They are about the same. A little stiffer glued to the rim because the glue joint acts somewhat like an end clamp and the natural stiffness of the panel and ribs reduces the size of the assembly somewhat. Other than that I don't think that there is much change. If we ever get our work load caught up enough to devote some time to your idea, I'll try it out. Regards, Del
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