[CAUT] CAF

[David Ilvedson]

I have just been repinning the balancier centers on our Hamburg D.   Pinned at 8 grams...hard get exact on these things...I haven't noticed a need to make a significant increase in the rep spring tension.   

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