We still have to fine a way to determine what a "firm" bushing/center pin is? David Ilvedson, RPT Pacifica, CA 94044 ----- Original message ---------------------------------------- From: "Fred Sturm" <fssturm at unm.edu> To: caut at ptg.org Received: 8/14/2009 5:40:16 PM Subject: Re: [CAUT] CAF >On Aug 14, 2009, at 5:02 PM, Chris Solliday wrote: >> Jeff T. is right when he says sluggish pinning of rep lever and >> jacks or weak springs are problems, well yes, that is obvious, but >> it's when the balancier is too loose that the real trouble begins. >> No matter how tightly you adjust that spring it can be pushed down >> by a heavy hammer returning on a heavy blow. Disaster. Pin balancier >> centers 4-9 grams (depending on how high your humidity gets in the >> summer) for best results. > I know that a number of people have been advocating for tight pinning >of balanciers, on grounds that it makes for better rep spring >regulation and function. I am going to express a bit of skepticism >about this. Granted, it will make it easier to do a bench regulation. >Will it, in fact, make for better function? > In real life piano playing, things are quite different from the >artificially created bench regulation procedure of watching the hammer >rise from check. One element of tighter centers is an obvious beefed >up spring (to overcome the added friction). In playing the key, the >way you feel that increase in spring tension as touch is in increased >resistance at the bottom of the keystroke, so if drop and/or >aftertouch are even somewhat excessive, this means a significantly >more heavy/resistant feeling action. Less so if drop and aftertouch >are minimal, but still noticeable. So there is a potential negative >effect on touch, on the feel of the action. > What actually happens during real life action function? The spring >acts at the drop screw and the wipp cushion, pushing them apart, thus >pushing the key back up (well, the back of the key down, hence the >front of the key up). And then (after a microsecond) it also acts at >the knuckle and wipp cushion, doing the same. Result is the key being >returned faster, and the wipp also being accelerated. But the hammer/ >knuckle are, especially on hard blows, rebounding faster than all this >other stuff is happening. Does the extra spring tension cause the >knuckle/shank/hammer to slow down relative to the wipp/key? On a hard >blow, I doubt it does so significantly, but I don't know. It probably >speeds up the key/wipp return. But the hammer/shank/knuckle probably >have enough mass and impetus to cut through, if the check is out of >the way. > And here is where I think (but don't know) CAF happens: if the key is >activated in such a way that it is released before check happens, the >check may actually get out of the way. And, yes, I think this does >happen sometimes. Here we are in the realm of high speed playing where >the key bottoms before the hammer starts rising, as many of us have >seen in films by Birkett or read about in the Five Lectures book. The >key has been activated, and the finger has moved on to other things. >The whole action assembly continues its function autonomously. Or >maybe the finger re-enters the picture, re-playing that key at some >unpredictable moment in the flurry of activity. > The fact is, we don't really know what is going on, because we can't >see it. We see a few high speed films that tell us a little, about >things like the jack bouncing back and forth against the knuckle >(especially if there is too much play between it and the rep window >cushion), about flex in keys and shanks, lots of different elements. >But do we really have a good take on how the whole action resets >itself in every circumstance (different types of blow, different >follow through actions like either rapid repetition or lazy finger >letting up the key, all kinds of variables)? > Bottom line, I think it is an oversimplification to theorize that >heavy rep pinning is a magic formula that cures all ills. Yes, that is >an exaggeration of what people are saying, and I certainly mean no >offense. I just think we need to look at all this with a humble and >skeptical eye. We don't really know. At least _I_ don't really know. >In my own work, I haven't found heavy rep pinning to be nearly as >beneficial as people say - except in making bench regulation a little >easier to do to spec. For me, the jury is still out on whether or not >heavy pinning of reps is positive, or positive enough to be worth the >trouble. > I was pretty skeptical about the notion that hammerflanges at under 4 >grams (in most new Steinways at 0-2 grams) would meet my theoretical >notions of how actions ought to work. A few years of fooling with >actions at those specs has made me re-think my theories. I am no >longer convinced that a 4 gram hammer center functions better than a 1 >gram one, assuming both are firm. And since I really don't find it >that hard to adjust rep springs with looser pinning (years of >practice, like tuning unisons), the improvement from heavier pinning >needs to be pretty positive for function to make me want to do it as a >matter of course. I have done it experimentally, and haven't noticed a >difference - that is, a positive difference in function. I have >noticed a difference in feel, that I haven't liked. > Just a different perspective on this whole rep center pinning thing, >in hopes of stimulating some thought. >Regards, >Fred Sturm >University of New Mexico >fssturm at unm.edu
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