To your questions and Ron's observations: I already raised the rest rail as close as is reasonable to the shanks - about 1/16" gap +/- It was lower before, and was worse then, but still exists. It's a solid (adjustable) aluminum rail and the felt is relatively firm and relatively thin. Blow was also even more prior to regulation (close to your 47mm), and the prolem was diminished by decreasing blow to 1 3/4" (roughly 44.5mm). Things are really pointing towards a too firm and too thin rest rail felt, and possibly some hammer flange pinning issues. Thanks for the insight, one and all. JD, "lever-heel," "backtouch", can you clarify this nomenclature for me? I'm unfamiliar with it. Thank you. William R. Monroe On Fri, Jul 30, 2010 at 11:50 AM, John Delacour <JD at pianomaker.co.uk> wrote: > At 20:19 -0500 29/7/10, William Monroe wrote: > > ... hammer double striking on a quick/firm staccato blow? I've got one >> that does... The piano is finely regulated otherwise (just today, in fact). >> 1 3/4" blow, about .400" Key Travel, Checking about 1/2", Rep springs are >> definitely NOT jumpy. >> > > How far off the cushions do the shanks rest? and how firm are the cushions? > With a firm staccato blow and a quick key release the jack can return to > the rest position before the hammer rebounds off the string, and if there is > too much light between the shank and the cushion then the roller (knuckle) > lands bang on the top of the jack compressing the backtouch which, together > with the spring in the compressed roller, sends the hammer flying back up. > If the shank rests only 2 or 3 mm above the cushion then the cushion > absorbs a good deal of the momentum of the falling hammer and the other > effects are largely negated, provided it is the right quality of cushion. > > Your 44.5mm blow sounds high. Try 47mm, but you must also get good > escapement by setting the touch depth to bring the jack back just clear of > the roller, and the clearance between hammer-"rest" cushion is important. > > All that said, the way the piano behaves will also depend on the quality of > the relevant cloths and baizes (lever-heel cloth, backtouch baize, > hammer-rest baize or felt, roller under-cloth). The wrong combination of > these can lead to the problem you have raised even if the piano is optimally > regulated. > > JD > > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100730/f78b85cd/attachment.htm>
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