> I see. By larger piano do you mean a D? Or are you going up to 900 lbs > for, say, a B as well? Thereabouts, possibly a bit less. I don't have hard rules, because the methods are evolving. >You mentioned previously that you are building the > ribs for higher load than you started originally and you found that there > was some relationship to hammer tolerance. The boards that you are now > building that are set up for, say, 650 lbs, what would those have been > previously? Probably not much different, but I can't say for sure. This isn't a very thoroughly documented research attempt, and I tend to pay closer attention to proportional cause and effect relationships than to specific numbers. I don't start out with a specific design load target anyway, and it ends up where it ends up when I'm reasonably satisfied with the design as to how it looks in the spreadsheet, how it is expected to perform and what it will teach me through the project. I'm making the ribs (therefor the assembly) generally stiffer, and adjusting the remaining crown up. The postmortem has indicated that the result is a greater tolerance, but not a requirement of harder hammers. This connects, to me, with the very high spring rate of a new CC or RCPS board and it's need, not tolerance, for harder hammers. > Just as an aside, you said that you plan for 40% deflection and end up > somewhere between 40 and 50%. I assume you are calculating your deflection > from beam formulas and basing it on the rib properties only and ignoring the > panel in the calculations, for the most part. Right. >It's interesting that when > you calculate for deflection based on the ribs only that the panel itself > contributes very little if anything to the stiffness of the assembly in > terms of the overall deflection. Do I understand that correctly? > > David Love Apparently so. The panel does contribute to overall stiffness, just not much in terms of deflection. Like that photo I posted a couple of weeks back of a nearly 3mm residual crown in the killer octave of a board with the strings on and up to pitch, with close to 1.5° of bearing at that spot, and the panel MC slightly below that at which I ribbed it. Ron N
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