David Love wrote: > The interesting thing about downbearing is that in a CC assembly it is a > requirement for achieving the desired stiffness. Yes, because the stiffness comes from compressing the panel to the crush point. >But since the stiffness is > present in an RC&S assembly by the design itself and downbearing play no > real role there then I think it's interesting to ask oneself what the > purpose, then, is of downbearing. If freedom of movement of the assembly is > a goal, and if the assembly already has the requisite stiffness, then why do > we need any downbearing at all? You may very well not, but then you wouldn't need crown either. >Why can't the bearing be set neutral? > Doesn't that give the assembly the greatest freedom of movement? In the > pianos where I've had all the design changes made I've found very little > change in tone with increases or decreases in downbearing. That's contrary to the impression you tried to give saying you preferred the sound with less bearing. >Where the > designs have been more conventional (except for the RC&S part--meaning with > original ribs, original backscale lengths, etc.) then I've found that more > downbearing can actually be detrimental. Which is why I tried to point out the difference in back scale length. >The bottom line is that with an > RC&S design I think one should rethink downbearing as well. It doesn't > serve the same purpose and therefore may work at cross purposes. Depending on the configuration. >I don't > think that's inconsistent with Ron's findings and I think it is consistent > with Del's findings. Since I don't know exactly what Dale's belly structure > is with respect to where it falls on the continuum of RC&S and compression > (i.e., are they hybrids and to what degree does compression play a role plus > how are the rib dimensions calculated etc., etc.) I can't really comment > there. I fully respect everyone's right to comment or not to as suits them > with respect to their own designs, btw. Likewise, as always, as pertains to rational technically oriented observation. > As far as hammer density my thoughts go something like this. These designs > are more hammer sensitive, at least in my experience. As I've also said so very many times. >Why is that, I wonder? One thought is that with full bass cut off, lighter and stiffer > assemblies, increased grain angles, the board's ability to produce higher > partials through the scale is enhanced. That can be a problem with a harder > hammer. How, why? That doesn't explain anything. The RC&S assembly isn't demonstrably stiffer than CC, that I can ascertain. It just gets it from a different mechanism. One thing that has occurred to me is that where CC is vibrating from rigid down, to loose up, the RC&S has a similar stiffness in both directions, with a broader and much less progressive vibrational stroke. I can't supply details of what that means, but it certainly strikes me as a more efficient counter spring to the string. > So what I've done is not make the bass cutoff too extreme and I've steered away > from grain angles that are too acute. So far it seems to improve hammer > tolerance without having to change the weighting of the assembly itself. I'm giving a lower grain angle a try on the current project to try this out. The bass cutoff is where it centers the bridge on the rib, as usual. Since the hammer hardness tolerance is across the compass, I can't see the bass cutoff position being a factor in general hammer hardness tolerance. Ron N
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