Roger proposed some explanations for tonal changes with Andre's Wurzen punchings: >Moral of the above points: The pianist works with after touch to >create tone. Any and all things that we can do, to make this >accurate and reliable, the happier our clients will be. Yes. True in multiple ways Roger. Andre was kind enough to send me some sample punchings which I have done some preliminary investigation with. Some of the behaviour which has been discussed here can be seen, as well as some surprising results. Before I can make proper conclusions I'll need to do some more controlled experiments, as well as compression tests....the latter I'm waiting for a new Instron testing machine which has finally been ordered and should arrive within about 2-3 months. For now, high speed videos (forte blow) show that there is an obvious mechanism whereby the properties of the punching can influence the hammer during escapement, and consequently the touch and tone. [It's not easy to set up these videos with a single high speed camera oberving events that are not in close proximity] I've also looked at the dynamic behaviour of the punchings themselves using macro high speed imaging. Green woven felt punchings show a definite sloppiness and tendency to shear on impact, and a much less clean deceleration, with distinct wobble of the key off the vertical as the punching is compressed. These observations are not seen with the Wurzen punching, presumably because the superior interlocking of fibres prevents the shearing observed with the woven material. I intend to do more testing of these phenomena and will report back on the conclusions (probably write an article about this), but it won't be till I've got the new testing machine installed in the lab and operational. In the meantime, if anyone would like to discuss the observations or examine the videos, I'll be attending the MARC convention this week, so just introduce yourself when you spot me and I'll be pleased to meet you. Stephen -- Dr Stephen Birkett, Associate Professor Department of Systems Design Engineering University of Waterloo, Waterloo ON Canada N2L 3G1 Director, Waterloo Piano Systems Group Associate Member, Piano Technician's Guild E3 Room 3158 tel: 519-888-4567 Ext. 3792 fax: 519-746-4791 PianoTech Lab Room E3-3160 Ext. 7115 mailto: sbirkett[at]real.uwaterloo.ca http://real.uwaterloo.ca/~sbirkett
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