Good question, as any answer might form a good guide and general rule of thumb. This post will be short as I need to get some shop work done, and also look at some action data. But for now, there can be no absolutes as all actions and action cavities will set limits. In addition, the vast majority of techs are modifying existing actions and not designing actions and cavities from scratch. Still, a generalized sense of it all can be (I think) worked out in broad but useful strokes, after which the technician's preferences can be intelligently made and defended. These investigations might begin by taking a "standard" well-known and properly behaving action containing a key stick of a certain length, and a blow distance of a certain value, and then mixing and matching a changing set of parameters in spreadsheet. The point would be to plot data and find trendlines, whether curved or straight. Action models would be helpful. My own sense of escapement dip is 2 mm (+ or -) and, as has been shown, this relates to a 5.50 AR and a working limit of a 10 mm overall dip. As a range, and until my research indicates otherwise, I accept escapement dip from 1.6 mm to 2.6 mm. At least I find that these actions work both in terms of weight and regulations. The 5.50 AR is powered well enough to balance heavy hammers without requiring unnecessary key leads, and yet is forgiving for regulating the technician's aftertouch. The 5 AR is even stronger and works as well, but I really can't recall ever achieving such a low AR when modifying an existing action. It wasn't brought out explicitly in the pervious posts, but a longer engagement dip, especially on a soft blow, should be preferable to the fine pianist. This is why engagement dip and escapement dip must be understood somewhat differently than technician's regulating parameters, although they are related. Theoretical engagement dip is built into the AR and nothing can change it excepting changes made to the leverages, which then change the AR, which finally change the dip. Escapement dip, on the other hand, although limited by the assigned overall dip, can be made longer though regulation. All in all, technician's regulating parameters are a bit arbitrary. There is an interesting variety of issues and anecdotal history that may be brought up, but the formulas and experience exist to uncover just about any thing we wish. Well, I will be signing off for a few days as Steve Brady will be the all-day instructor for the Phoenix Chapter this Saturday. Steve is due in tomorrow and I will be quite (and happily) busy the next few days. Ciao for now. Nick Gravagne, RPT Piano Technicians Guild Member Society Manufacturing Engineers Voice Mail 928-476-4143 _____ From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of David Love Sent: Thursday, January 07, 2010 1:45 PM To: pianotech at ptg.org Subject: Re: [pianotech] Action Ratios OK I understand that. So my next question is what would you consider the minimum escapement dip that you can live with and what do you consider a reasonable ceiling for AR overall in terms of conforming hammer weight (or strike weight if you prefer). -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100107/c81a9752/attachment-0001.htm>
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