I meant to say a high leverage, low strike weight system may work best with higher friction, not lower (last paragraph). David Love www.davidlovepianos.com -----Original Message----- From: "David Love" <davidlovepianos at comcast.net> Sender: caut-bounces at ptg.org Date: Thu, 2 Dec 2010 16:35:40 To: <caut at ptg.org> Reply-To: caut at ptg.org Subject: Re: [CAUT] F..riction Fred et al: Lots of different points you've made, each one a subject unto itself. Damper resistance is certainly an issue and I have wrestled with the optimum setting and timing in order that there is the least amount of difference between playing with the pedal down and not. Clearly you can make the action very uncomfortable to play by having early damper pick up, too much damper weight (or spring tension) or both. It really bothers me as a player to encounter an action that plays beautifully with the pedal down and like a truck with it up. The trade off is finding a level of shut-off that you can live with. I generally opt to live with a slower shut-off. It's a better deal in my view. I've asked this before and not really gotten a definitive answer but I'm curious as to what criteria people use for setting damper spring tension (or damper resistance), where in the stroke you determine the resistance and how much is too much. What happens at the bottom of the stroke does matter, I agree, and there the repetition spring tension (or wire gauge) along with an accurate drop setting (timed with jack tender to let-off button contact) jack alignment and proper lubrication (let's not forget key dip and aftertouch) all are critical in being able to play pianissimo through the entire key stroke without running into a false floor at the bottom of the stroke or getting a double bump from let-off drop being out of sync. Repetition spring tension can vary a lot depending on the friction in the hammer flange, the friction in the rep lever center pin, the weight of the hammer, the accompanying leverage. This again will contribute differences in feel at the bottom of the stroke. Higher levels of friction in the rep lever combined with higher levels of friction in the shank flange combined with high strike weights will force a higher rep spring tension and one might take that into consideration. One might derive a formula of some type for optimum rep lever tension such as: high strike weight, low rep lever friction, medium shank flange friction is ok whereas, high strike weight, high rep level friction, high shank flange friction is not. Or on the other side, low strike weight may combine better with higher flange friction since a combination of low strike weights and low friction will create difficulty in setting the rep spring tension high enough to ensure jack return but not so high that double hitting might likely occur with proper drop settings. Checking at pianissimo is not an issue for me as long as the rep spring tension doesn't allow for bobbling or double hitting. Moreover, there may be an argument that can be made for combinations of strike weight/leverage/friction that are optimum within a given system, which I'm inclined to believe. For example, a high leverage, low strike weight system may work best with low levels of friction whereas a low leverage high strike weight combination may work better with lower levels of friction. It would make sense. Somewhat apropos to this was a situation I ran into recently. I was called upon to assess a piano because the customer was very unhappy with the feel (good pianist). The set up (very well executed Stanwood action) was set up with a very low leverage, highish strike weights (I don't recall the zone now but can look it up) and very low friction levels. The customer felt very disconnected to the action, unable to control it especially at low levels. The first thing I tried was to raise the dip which was around 11mm. I did this by compromising the blow somewhat. That was somewhat helpful but didn't really do what he wanted. So the next thing was to repin the hammer shank flanges to return some friction--it was very near 0. Repinned from 10-12 swings to about 5-6 swings. Bingo, that helped a lot. The issue was still not completely resolved but it was noticeably better. The remaining problem, I believe is related to the action leverage simply being too low. The relationship between key travel and hammer travel had been altered so much from what this pianist is used to that it simply felt weird. While the action was very facile and I'm sure would have been quite satisfactory for many pianists or at least not something they could not get used to, this was a case in which this customer found it objectionable. This was a situation in which a direct comparison of more versus less friction was possible and yielded positive results. While anecdotal and not necessarily something that one can draw definitive conclusions about, it is worth noting. Please forgive typos as I'm sending this off without a careful proofing. David Love www.davidlovepianos.com -----Original Message----- From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of Fred Sturm Sent: Wednesday, December 01, 2010 4:59 PM To: caut at ptg.org Subject: Re: [CAUT] F..riction On Nov 30, 2010, at 9:58 PM, David Love wrote: > But even though > flange friction is essentially a moving target (just like tuning and > voicing) I still believe it's worth addressing along with the > necessary > compensations that those choices entail. Hi David, Good post. I agree with what you have to say, essentially. I would concur that a reasonable level of consistency in friction is important and desirable. I'd like to expand on the question of the impact of centerpin friction on touch. (Let me say that from here on, I am not addressing David specifically, but the list in general). Let's start with the hammer, 4 gm vs. 0 gm + a bit. 4 gm measured at one inch translates to less than one gram at the hammer's center of gravity, which is somewhere around five inches out from the center (simple ever, so 4 divided by 5). So pinning a flange that has 0 or so gm friction to increase it to 4 gm would have an impact on the hammer's throw somewhere in the vicinity of impeding its movement by one gram resistance. Intuitively, that doesn't seem like much, doesn't seem like it would have a significant tonal impact by itself: hammer of X mass at Y-Z range of velocity being braked by one gram's resistance, maybe someone on the list has the math and engineering background to do a reasonable modeling. But let's go back to the key and touch. The friction resistance at the hammer gets multiplied back by 5-ish because of the key/hammer ratio (nominally 5:1 in the opposite direction), so 4 grams friction measured at one inch from the centerpin translates to 4 grams at the key, at least nominally. Or so my calculating brain would say, and maybe someone has measured to confirm: does pinning a flange from 0 to 4 grams increase DW by 4 grams or so? This time of year, I have no time to do other than tuning and the necessary, and I've forgotten what I came up with years ago when I fooled with that. Let's assume it is correct. Hence, the initial impact on touch is simply addition of resistance to the finger, maybe 4 grams. As we depress, we hit a couple obstacles, the first being the damper. An aside, but an important one: amongst all the talk of evening hammer weights and strike weights and friction, I don't recall any discussion of damper lift resistance as a component of touch. Does anybody actually measure this? Seems like something that ought to be included, since pianists do play without the pedal and with "half pedal" (usually just lifted enough to bleed but not be entirely open). But let's do what "everyone does" and ignore it, press down the pedal and proceed to the next obstacle. That would be the drop screw pressing down on the key through the rep lever and the spring. Maybe the jack tail touches simultaneously, or maybe just a little later (I think that either is acceptable as long as they are quite close, and the jack tail shouldn't touch first). Let's take the jack rubbing against the knuckle out of the picture for the moment (raise all the hammers in the air), and isolate the springs pressing down on the back of the key. The pressure is dependent on the strength of the spring, and increases as the key is depressed and the spring is compressed. The lower the drop is set, and the more aftertouch you have, the more pressure builds up at the bottom of the keystroke. I think this concept is one that can't be emphasized enough when it comes to concert and high end work - OK, and other work as well. Rep spring strength is dependent on friction of the hammer center and the rep center, so if those have been jacked up pretty high, the spring resistance will be way high. WIth those hammers in the air, press down on five keys lightly with five fingers to feel the resistance, as a way of isolating that aspect of touch. (Pressing on five at once is a good way to feel more precisely, as it is when estimating DW by feel). I think (judging by pianos I run across) that there are a lot of techs out there worried about getting checking at pianississimo, and pinning tight, checkering tails, increasing drop to accomplish this, and it is not a good thing IMO. Let the hammer not check at pianissimo, no harm done. Far more harm done to the touch by increase of spring tension and amount by which the spring is compressed (drop adjustment), again IMO. My point in raising this issue is to counter the notion that more hammer and rep center friction is a good thing because it makes regulation go better. Maybe it does make it easier to make specs (nice even hammer rise from check, easy to get the jack under the knuckle), but going overboard has what I believe to be a negative impact. Back to the touch scenario, putting the hammer back down, the feel of the action from the moment of impact of the rep lever with the drop screw through aftertouch is arguably the very most important element. German instructors (as I remember from classes by Bechstein, Seiler, and Schimmel reps, as well as at the Sauter factory) emphasize the additional DW required to take the action through letoff. They say it should be in the 10 gram or less vicinity if memory serves. Much of that is friction of the jack against the knuckle. If there is too much friction in flanges and too much spring tension, that will also come into play here. I've gone on long enough for now. Regards, Fred Sturm fssturm at unm.edu "Travel is fatal to prejudice, bigotry, and narrow-mindedness." Twain
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