Here's a little toy for y'all. Action Ratio/Regulation Calculator. Green boxes are inputs yellow is output. You can input the action ratio, blow, let-off and after touch and by the formula given it will yield the dip specs. The question at hand has to do with what exactly is the after touch spec that's used to make the formula ratio by product of the levers equal to the blow/dip ratio as given. As Nick mentions the blow and let-off are predictable and consistent. The point at which after touch begins to be measured and thus its value in this equation is a question mark. Depending on where you measure it from that number can change and even a small change impacts the overall dip requirements as you can see. Yet, if the product of levers, in fact, is equal to this particular relationship then after touch (at least for the sake of this formula) must have some constant value. I'd be curious to know what that is. Typically, when I set after touch I use the following method: insert a dummy .040" (1.016 mm) punching under the key at the front rail and adjust the dip until I just barely get let off with that punching inserted. That leaves me with .040" after touch once it is removed. But when I input those numbers in this calculator, as you can see, then by that formula a 5.75 AR with 45 mm of blow distance should regulate with 8.6 mm of dip. From my experience that seems a bit shallow. Now I suppose that since we actually do get let off with the .040" punching inserted you could argue that we actually have a bit more after touch than that so then I increase it to .060" or 1.5 mm and that should yield a dip of 9 mm (.354" for those of you who prefer that method of thinking) which also seems somewhat shallow. I'm more used to that action ratio producing a dip of something in the neighborhood of 10mm. So my question, to reiterate, is if the formula given is correct and true, what is the value of the after touch, at least for the sake of the formula? I suppose by trial and error we could come up with a number but since this formula was derived by someone, I'm assuming they had something in mind. Naturally, there is a compounding issue, as Nick points out, that the method of measuring the levers themselves varies depending on who you ask and the product can vary considerably as well. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Nicholas Gravagne Sent: Saturday, August 25, 2012 10:49 AM To: joegarrett at earthlink.net; pianotech at ptg.org Subject: Re: [pianotech] action ratio Joe, You actually DO know this. "Key in", etc. is that portion of an action component that represents the effort or activation arm of the lever in question. The "outs" are the resistance arms. So in broad terms, "key in" is the front half of the key and the key out is the back "half" from balance to capstan. Ditto on the whip and shanks. Multiplying the ratios of the key, whip and shank (each component having its own effort and resistance arms), as they exist on the left hand side of the equation yields the action ratio (AR), also referred to as the transmission ratio by Pfieffer in his books. I don't know if it shows up in all email clients, but the entire equation as posted, both left and right hand sides should be shown as as division, which is to say these also represent ratios. Given that, then the left side ratio (even though it derives as a product of three ratios) is equivalent to the right side ratio (even though the right side indicates --- or should depending on how you see in in the post --- as blow-distance-minus-let-off (divided by) key-dip-minus-aftertouch). Since there are so many variables here, there can be no one standard for aftertouch. So without running a bunch of example numbers right now, let's say we multiply the three component ratios and the AR works out as 5.8 to 1. Another action might yield 5.58 and so on. However, blow distances and let-offs do not generally vary much, so these can almost be stated as fixed constants (say 46mm blow and 2mm let off). Key dips can vary more so, but again, about 10mm plus or minus. Thus, given the equation it is clear that the left side must equal the right side, say 5.8 on the left side must somehow equal 5.8 on the right. If blow distance is locked in at 46 and let off at 2, then this equals (46 - 2) or 44 . Now if key dip is locked in at 10, then all that is left unknown is after touch. Some simple algebra yields the unknown after touch as 2.41mm (0.095"). The formula will now balance since: (Let side Action ratio) of 5.8 is to1 as the: (Right side Regulation Parameters) of (46 - 2) to (10 - 2.41) or 44 to 7.58. Thus the right hand and left hand ratios are satisfied at 5.8 Now having said this, note two things at least: 1) given the action ratio (AR) as fixed, which it is, once established one way or another, the only "fudge-ables" are action regulation parameters. But regardless of what you do with the regulations, these will always balance the AR value. 2) the reason there can be no one aftertouch value to fit all situations is that the ARs from one action to another are not all the same; and so "as goes the AR, so goes the regulation" (which includes the aftertouch portion). And so, Joe, you old curmudgeon and Captain of the Tool Police, I really DO think you get this <G> NG Key out x wippen out x shank out = blow distance - let off Key in wippen in shank in key dip - after touch On Sat, Aug 25, 2012 at 8:34 AM, Joseph Garrett <joegarrett at earthlink.net> wrote: And they mean what?! I'll need something a bit stronger, like a good single malt!"Key in"??? What does that refer to? Just because some brainiac thunk that up, doesn' mean squat unless an explanation is with it imo.<G> Joe ----- Original Message ----- From: Dale Erwin <mailto:erwinspiano at aol.com> To: joegarrett at earthlink.net;pianotech at ptg.org Sent: 8/25/2012 8:18:25 AM Subject: Re: [pianotech] action ratio These are formulas used by Nick Gravagne , David Stanwood and others to determine the overall action ratio. Which is a very useful thing to know. Need some Excedrin now Joe? Dale Erwin R.P.T. Erwin's Piano Restoration Inc. Mason & Hamlin/Steinway/U.S. pianos www.Erwinspiano.com Phone: 209-577-8397 -----Original Message----- From: Joseph Garrett <joegarrett at earthlink.net> To: pianotech <pianotech at ptg.org> Sent: Sat, Aug 25, 2012 8:03 am Subject: Re: [pianotech] action ratio David said: "One formula for the action ratio has been given as: Key out x wippen out x shank out = blow distance - let off Key in wippen in shank in key dip - after touch Does anyone happen to know what the standard (or minimum) aftertouch is in this formula or how it was derived? " David, First of all, I need to know what the hell "key out...." and "key in..." means. Have never heard the terms. I suspect if I knew, I'd get a headache Joe Joe Garrett, R.P.T. Captain of the Tool Police Squares R I -- Nick Gravagne, RPT AST Mechanical Engineering -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20120825/7e32960b/attachment-0001.htm> -------------- next part -------------- A non-text attachment was scrubbed... Name: Action Ratio Calculator for Pianotech.xlsx Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet Size: 11760 bytes Desc: not available URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20120825/7e32960b/attachment-0001.bin>
This PTG archive page provided courtesy of Moy Piano Service, LLC