This is really interesting. Could you back up a couple of steps and help me understand what the reasoning for increasing the angle from 45deg in rc&s boards is? I'm thinking out loud here... On a sample old compression board I have (non-radial rib pattern), there is a 42 deg grain orientation relative to the belly rail. This grain orientation puts the cross grain consistently 12 deg off of perpendicular to the ribs through the entire scale. Since cross grain dead perpendicular to the ribs would be the weakest structural orientation of the grain, I assume they were looking for some consistent degree of stiffening from the grain orientation, but not much. Read...entire assembly somewhat flexible...stiffness mainly defined by compression.. On an rc&s board, the fact that the panel itself is not trying to be a significant structural member demands that the ribs be oriented in a fashion which allows them (the ribs) to create the assembly's structure. This dictates the need for the cutoffs/fish and radial rib pattern. Given the radial rib pattern, if you were to leave the grain orientation at 45 deg, the panel's grain orientation would be well off perpendicular to the tenor/low tenor/bass ribs, and pretty close to perpendicular in the high treble. Read; @ 45 deg the panel would add too much stiffness in the tenor/low tenor/bass, and hardly any in the high treble. Seems backwards of what you would like to happen, ie you'd want the bottom end appropriately stiff (from the ribs) but not constrained by a too stiff a panel, and in the high treble you'd want whatever stiffness you could muster, rib and panel (to a point). So shifting of the grain angle up adjusts this, putting tenor/low tenor/bass ribs closer to perpendicular to the grain, and high treble closer to parallel to long grain. I think I answered my own question...does this make sense? (...Let me down easy boys...) Jim Ialeggio grandpianosolutions.com 978- 425-9026 Shirley, MA David Love wrote: > One interesting thing that I'm beginning to notice is that there is an > interaction between grain angle, assembly stiffness and hammer tolerance. > For example, I've built boards of varying stiffness in terms of rib scales > altering the grain angle (from 50 to 60 degrees--bass cutoffs are standard) > and have noticed that the boards with higher grain angles seem to be less > hammer tolerant no matter what the stiffness factor in the ribs. That's > interesting to me, if true. I have noticed that a change in the grain angle > seems to change the balance of partials, the timbre as it were. A higher > grain angle does make the panel stiffer (clearly) even to the degree that > higher grain angles tend to increase the need for bass floats (or more > aggressive panel thinning), especially in smaller pianos. But more than > that it appears to me that the upper partials, especially through the tenor, > take on a much more dominant role the higher the grain angle. In that > situation it seems that a soft hammer doesn't prevent the board from > producing a strong set of upper partials as it will in a board that is > somewhat less stiff. That means that when you go to a hard hammer the upper > partials become too dominant, the fundamental relatively weak and it sounds > unpleasant, even clangy. Why this seems to happen with grain angle shifts > and not with increasing the rib stiffness I can't really say, I've simply > made note of it. My current formulas have backed off on the grain angle > changes somewhat (though they are still increased from an often seen 45 > degrees but not as much as 60 degrees on anything under 7') and kept the rib > scales still in the light-mid to midrange for low tension scales like > Steinway. While that hasn't put me in the realm of Premium Blue or stock > Abel hammers it has allowed me to prepare hammers with a somewhat more > aggressive attack without any problems. > > Of course, all of these variables are really difficult to isolate but this > is a trend I'm beginning to take note of and it does have implications for > building concert venue instruments where a sharper attack is more the > requirement. > > > David Love > www.davidlovepianos.com > > -----Original Message----- > From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf > Of Ron Nossaman > Sent: Wednesday, February 10, 2010 5:06 PM > To: pianotech at ptg.org > Subject: Re: [pianotech] Hammer strike line. Was-----whatever > > erwinspiano at aol.com wrote: > >> but I'd call it definitely at the light end of RC&S, which I think is >> why the hammer line deviation made a tonal difference. You have 16 ribs >> here, on a 7-1/2' piano. >> > > That, I can't explain, unless it's weight. Those are wide > ribs. I stiffened my boards up considerably from the first > attempts to make them more hard hammer tolerant, and it > worked. Some folks want more bite than Bacon felt Ronsens > provided. The lighter builds sounded nasty with harder hammers > than that. > > > >> * * *Adding two more ribs to the set with the all the ribs spaced >> differently would be adequate to support the treble. Why that >> would prefer a less stiff hammer is a bit of a question. Nick and I have >> often asked each other how stiff is too stiff?* >> > > As long as the assembly's light, and can bend at the > perimeter, I'm not altogether sure it can be built too stiff. > > > >> * Experience to me says, the stiffer the board the stiffer/denser the >> hammers need to be. The more flaccid the board the less dense hammers. >> > > Mine too, and still does. > > > >> SO your experience* _is_* that adding two more ribs to a S&S C set >> somehow defeats the need for a level of hammer stiffness I am >> uncomfortable with. >> > > Nope. I'm saying I found I could still use a soft hammer, but > gained the potential to use a slightly harder hammer. I'd > still call Renner Blues and Abels way out of the ballpark for > my builds. > > > >> *Meaning ribs less tall or not as long because of a fish??* >> > > Not as long. Length, as apposed to depth or thickness. > Shorter=stiffer and lighter, automatically. > > > >> Beats fighting the original though, don't it? >> *Yes and the the attractive sound that Steinways are know for is >> enhanced focus and clear and folks just love it. Makes my Day to be sure >> and certain.* >> > > My day's a long way from made then. I've still got plenty to > learn. > Ron N > > >
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