Hi , everyone, Even if the theory is saying that the action will flex a lot, it is under very heavy play. The amelioration with the optimum backchecks height is (to me felt as a difference in synchronization, if one drive the backchecks even lower, the tone get more power (that is not absolutely good for the tone but it is) it is also producing a tactile change, that lend to a better tone at the same time . As the effect is audible even at mezzo forte, or lower, then the backchecks is certainly not rubbing on the tail. The lower the backchek, the firmer the backchecks wire , also , all that goes the same direction to me, with some optimum placement that I recognize because of the touch feel, the noise of the checking when regulating, and the tone. I consider the method we use to check the clearance and security of the tail/backchecks relation to be relatively secure, we can really bend strong the shank of the hammer, restraining its motion while pushing on the key, if we want to. I stay on the concept of the synchronism or a sequence that works better for energy reasons. The noise indeed is "masked" in the attack tone, that is what we do when tuning. I have seen experiments where the action noise and attack noise was separed from the tone, and if the tone of the piano was heard without it it was barely recognized by an audience. I believe also that the punching may be firm and resilient, not so hard. The action when played with speed is braking a lot and the thump noise is not that large unless the pianist have a bad touch or is too violent (or the action is out of regulation, without enough aftertouch). When I feel too soft punching I have the impression of walking on a bed. Firmer punching gives an impression of more tonal power, while this is may be good to some point because the pianist is mostly concerned, when the audience begin to hear too much key noise, then the punching is really too hard , this the pianist is not always prone to remark because of the mix tone/touch he appreciate. See you soon. Isaac -----Message d'origine----- De : pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]De la part de Sarah Fox Envoyé : vendredi 20 août 2004 21:46 À : Pianotech Objet : Re: back check, a magical mystery tour. Hi Stephen, > I'm thinking something is causing this that > occurs before the string impact. The obvious candidate is interaction > between the backcheck and the hammer tail as the hammer heads toward > the string. Backcheck clearance is supposed to be pretty tight, and > I've seen enough examples of slight catching on the check as the > tail goes up, enough that power is lost without it being obvious. What a compelling theory! I think you just may have something there. We are to understand that with forceful play, it's possible to bottom a key before the hammer even budges (er... *much*). However, with the bottoming of the key, the backcheck would be elevated and could obviously catch the hammer before it can accelerate out of the way -- if the clearances aren't adequate. I would presume that the only thing that would prevent this is the flexure of the various action parts. The keystick would be flexed concave-downwards, such that the backcheck would be bowed out and downwards (away from the hammer). At the same time, the jack would be punched up into the knuckle, and the hammer shank would be bowed concave-downwards, causing the tail of the hammer to flex away from the backcheck. I'm wondering if all this can't be measured with a "pseudo-dynamic" model. Could the hammer be restrained while the keystick is bottomed out? It seems like that would be kinda stressful to me, but I guess forceful playing is rather stressful. (As a kid, I remember watching Van Cliburn snap a hammer shank in concert, which a technician plucked from below the strings between movements.) Honestly, I'd be a bit afraid to try it on my own piano, without someone I trust reassuring me it's really OK! ;-) If this can be done, then flexure and clearance can be measured in a reasonably controlled manner. This "pseudodynamic" model would of course not take into account the flexure of the keystick between the capstan and the tip or the flexure of the backcheck wire/post (term??), due to acceleration, nor would it account for acceleration in other parts. It would simply account for what are surely the most prominent variables -- hammer flange and keystick flexure (or at least most of it), felt compression, etc. While I realize you probably have the high-speed video equipment and electronic instrumentation to take true dynamic measurements, I'm thinking some sort of pseudodynamic measurement system would be extremely useful to the technician in the field -- since not all hammer/shank assemblies and (especially) keysticks are created equal. I was also thinking about the suggestion of steepening the backcheck angle to create a more positive touch. If indeed the hammer and backcheck are meeting, due to action part flexure, then the problem would certainly be aggrivated by having too steep a backcheck angle. There is probably some angle that is "just right," yielding just enough clearance on a hard power stroke, while preserving a tight check on the rebound. It's interesting that centuries of piano building have resulted in the trial-and-error optimization of action geometry and regulation standards, and it's only recently that we're trying to figure out why these arrangements work. Fascinating stuff! I look forward to hearing what you folks figure out! Peace, Sarah PS Thanks, Robin! I enjoy your insights too. :-) _______________________________________________ pianotech list info: https://www.moypiano.com/resources/#archives
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