---------------------- multipart/alternative attachment At 01:38 PM 8/25/2004, you wrote: >If you have a hammer swinging 4 to 7 times and it has side play you have a >birdseye problem...not the bushing. > >David I. Well, David, there is also the quality (or lack thereof) of the bushing cloth. As many here know, I have done a bit of study into action centers, especially grand hammer centers, both on my own and through work with a company I worked for in the past. Even and 'correct' friction became an obsession when I was rebuilding pianos during the 80s. At that time a piano dealer I did work for was having me "maximize" a certain brand of American pianos, which at the time was using seriously substandard action cloth and / or cloth sizing procedures. One of the steps I took in customizing these actions was to do a very heavy shrink-fitting of the hammer shank centers. Short of rebushing the shanks, this was the best way I found to improve the fit of the centers. The centers (which came with 19.5 pins as I recall) became extremely loose, after which I burnished and fitted 20.5 pins into the now thinner bushings. The change in touch and tone from this one change to the piano was incredible. It was not subtle at all - the pianos sounded dramatically more solid in tone and more powerful. Of course, I had to re-weigh off the keyboards, as the weights had been installed with horribly uneven friction levels in the actions. Hammer flange friction varied from 2 to 10 grams in almost every set I worked on. The bushing quality is the big variable in fitting action centers, and is one reason people will disagree so strongly on what friction is correct. Their experience with different pianos causes different opinions to be developed. When repinning hammer centers, I have always pinned for even friction through the set. I strive for +- 1/2 gram within a set (a 1 gram tolerance - which I would prefer to be 0, of course), and the amount of friction is decided on according to the ambient temperature and humidity, and the relative firmness of the action center cloth. 4 - 6 grams is a guideline, but I frequently pin parts with very high quality felt at 2 grams, especially in dry conditions. If the cloth is firm, it can be pinned more loosely and still control the hammer motion well. If the cloth is soft, you must pin it tighter in order to maintain the control. I do not have a formula to decide how tight - it comes from feeling the side play after pinning, and the experience of checking this on many pianos. As for tonal change from very tight centers, the best illustration I have had was with one unfortunate piano in which the hammer centers were all gummed up. The usual problem of the owner not wanting to pay for new parts was there, so with a written disclaimer signed by the customer, I agreed to clean and lube the action to keep it working until the parts could be replaced. The tonal change was absolutely dramatic - the customer said afterwards "I didn't know you were going to make the tone better, too!" With sluggish centers the tone was dull and muffled with very, very poor sustain. After freeing up the centers the tone was moderately bright with very good sustain. I am also fond of the later version of the Teflon bushings, by the way, but this is long enough for now. Don Mannino RPT ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/ca/1d/f3/9e/attachment.htm ---------------------- multipart/alternative attachment--
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