Ric wrote: >As far as how often checks need adjusting. Hmm... you'd be suprised >how varied back check height is off the factory line... even in >pianos like Yamaha where <<precision machines>> are specially made >to do the job. Then there is the hammer change job done by the tech >down the street...... grin.. In short... it happens often enough >that they need addressing. What I meant actually was: when some change is determined advantageous how often do they have to be raised vs lowered. In other words, is it mostly a case of lowering? or raising? checks to achieve the 2mm space? The chalk thing would, of course, need a little cleverness, so the hammer is caught somehow before it reaches the check position. Otherwise, you couldn't interpret the presence of chalk transfer as having occurred before the impact. Maybe not feasible, but, even if it affected the impact (e.g. remove the string and have the hammer fly upward and over), the experiment would achieve the desired result, since the proposal is to see if the hammer tail catches the check *before impact, under certain circumstances and configurations. High speed imaging would work for sure, but may not be necessary to answer the question. For curiosity, is the dud problem more often associated with actions that have softer whippen cushions? Stephen -- Dr Stephen Birkett Associate Professor Department of Systems Design Engineering University of Waterloo Waterloo, Ontario Canada N2L 3G1 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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