My practical question may have been unclear to you but when I put this question (If you are constructing an action and want one that regulates with 10 mm total dip and 46 mm blow where should you target the action ratio?) to the individual who manufactures replacement keysets for me he was able to give me a fairly precise answer with some slight variations depending on the particular action model. Your description of after touch below is, of course, de rigueur. David Love www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of John Delacour Sent: Thursday, January 14, 2010 6:13 PM To: pianotech at ptg.org Subject: Re: [pianotech] Action Ratios Recap At 16:08 -0800 14/1/10, Jason Kanter wrote: >John, the same day of your detailed and interesting message, David >Love asked you: > >OK. So then from a practical standpoint, when converting action ratios as >calculated by a product of levers to the relationship between dip and the >requisite hammer rise to achieve a targeted blow distance with adequate >aftertouch, what would you use? Well the reason I didn't answer this is because it made little sense to me no matter which way I turned it. There is one way and one way only to perform these calculations accurately and that is to use trigonometry. What a "product of levers" means is not clear, but there is no way (and no point) to convert something based on a falsehood into a correct result. As to the after-touch, the key must go down far enough after escapement commences to allow the roller (knuckle) to clear the face of the jack as the hammer falls into check, as is common knowledge. At that point the back of the jack is touching but not compressing the cushion. Any further after-touch is unnecessary and detrimental. The tail of the jack rolls and slides on the set-off button -- as with the roller/jack contact there is inavoidable friction, but the exact distance the key must travel to accomplish this optimal escapement can be accurately calculated trigonometrically just like all the other relationships. >and I asked you: > >John, could you please add a definition of PROFILE? Though the answer was included in the message that asked the question, I have made it clear in a separate message. JD
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