At 11:12 -0700 15/1/10, Nick Gravagne wrote: >..."Methinks, Horatio, when truth be false, the consequence worse! >Whence ratio, Horatio, to me 'tis but lever; to others still I am found >but too clever." You had me fooled - brilliant! Thank you, Nick, for your considered and witty response. >Perhaps the reason that "nobody has even commented on" your Jan 10th >post is because, as I see it, it is not complete, except for the >rationale and mathematics of capstan rise to that of key dip. Quite so -- it wasn't meant to be complete but merely to present in detail the calculation of the first ratio in the chain, to show the method that is applied to all the subsequent calculations, which get rather more involved. A full presentation would have overtaxed the brain of the writer and the eyes of the departing readers. >...Your palpable criticism of Pfeiffer's work and, presumably, any modern >technician's work who borrows from him has, I am guessing, not gone >unnoticed. I've had Pfeiffer's books for over 30 years and they have been an invaluable source of information and inspiration to me. I recommend them to anybody. That does not mean that I accept all his conclusions... but enough of that. >You are entitled, don't get me wrong. I have not ignored your post, but >there is much to consider. Your argument that the most exacting ratio of >key dip to hammer rise, as these relate to x and y positions of >components gliding along arcs, is, of course, completely valid. What >remains to be seen is what we gain from such exactitude. As I've said before, I see no point in approximations when by using simple school geometry/trigonometry one can achieve precise results. That doesn't mean that every technician needs to polish up, or more likely learn from scratch, the necessary mathematics, but by feeding a number of measurements into a computer programme it is would be possible for him/her to get all the information he needs about the behaviour of the action and see the results of any planned modifications. This includes the production of precise scale drawings and even movies. >I have long thought that we yet lack a consistent and unified approach >to the subject. I recently evaluated a Young Chang action by physically >measuring the lever arms using three different methods, resulting in >three different ARs of 5.9, 5.7 and 4.6. The AR that mostly agrees to >the actual measurement (a bit tricky to do) of dip and subsequent hammer >rise is the 5.7 AR. As you say, certain measurements are frustratingly difficult to get exact. I'd guess that the proper ratio would be 1:5 (and here Pfeiffer would agree!) and that anything much different would be due to poor set-up by Young Chang, the wrong roller size, the wrong roller position or the wrong key ratio -- but that goes without saying. My experience of these problems stems from the piano I bought just after I was married, and still have, the piano that was soon to lead me into the piano trade. This is a 1905 Lipp upright, one of the finest uprights ever made. When I tried to regulate it according to the few rules I had by then learned, I discovered that if I did the blow according to the book and the touch depth and set-off ditto, the hammers would burble and eventually settled on a touch-depth of nearly 11mm, which did feel deep. One fine day another Lipp turned up with the case turned to dust by woodworm and I salvaged the keyboard, which had good ivory, unlike my old wreck. Not only that but the key ratio was quite different, for the same action. Problem solved. One day I'll actually get round to fitting it! >...Very well, then, let's get to the truth. > >I will follow up soon with some ideas on how we might handle this issue >with a degree of organization, clarity, consistency and professionalism. >Handled as such, we all might learn something. I'd be very happy to cooperate, especially as I have a lot of work-in-progress on several aspects of the matter and need some stimulus to keep things moving forward. As regards the programmed drawings and movies, the delay is due (apart from my innate tendency to let things drop) on the one hand to the sheer amount of programming work involved and on the other to the fact that the software tools to do the work are still evolving and not perfect, so there are frequent frustrations -- for example the tool that converts my SVG drawings to the vector PDF files that are needed to build the QuickTime movies won't deal with text, so the text has to be drawn from scratch as SVG elements. I will post some more basic stuff as time allows. All the best, JD -- ______________________________________________________________________ Delacour Pianos * Silo * Deverel Farm * Milborne St. Andrew Dorset DT11 0HX * England Phone: +44 1202 731 031 Mobile: +44 7801 310 689 ______________________________________________________________________
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