Personally, if that was my piano, I'd want the factory to give me a new piano. Wouldn't that be a warranty problem? David Ilvedson, RPT Pacifica, CA 94044 Original message From: "Bruce Dornfeld" To: pianotech Received: 12/29/2008 8:10:56 PM Subject: Re: [pianotech] Repeat Question about damping problems Will, This is the unedited version of what ran in the Journal recently about quieting a plate strut. I will send a photo too, but I'm not sure about the file size. The Weird Stuff: The Ringing Plate Strut Bruce Dornfeld, RPT A piano teacher whose pianos I have serviced for many years got a new Kawai RX-2 grand. She loves the action and the tone, but a problem became apparent after she had been playing it for a while. One of the plate struts made a ringing sound when many of the notes were played forte or louder. She did not notice it at first, but when she did, it became a real annoyance to her. It became almost impossible to ignore. Diagnosing the source of the noise was pretty fast and straight forward once I decided it might be the plate, that is. When I played a note loud enough to make the ringing, I held the offending plate strut firmly with my other hand. The ringing stopped completely. Playing the note a number of times while holding and releasing my grip on the plate strut left no doubt about the source. I called the service department at Kawai. The staff there compared notes with each other to come up with suggestions. One technique used by Japanese technicians on Kawais concert grand to remedy this problem is adding weight to the problem strut. Lead key weights have been fastened to the bottom of the strut to quiet the strut. Maybe that lowers its vibration frequency so it is low enough, it will not be perceived as ringing. Maybe the added mass would just require too much energy to vibrate enough. I dont know which. Gluing or soldering on lead weights on this teachers piano did not seam like a good option. It would be difficult to reverse if it looked too unsightly, so we wanted to come up with another solution. First we tried putting all of her refrigerator magnets on the strut along with several magnetic strips I carry to use for setting let off, but it was not enough mass to make a difference. Since the long length of the strut is part of what allows it to vibrate, I thought it would be good to make it shorter. Since the Dornfeld Piano Plate Foundry is not open for business, I came up with the solution in the picture. The wooden dowel is wedged tightly with one end in a corner with the other end in the middle of the offending plate strut. It is held in place with small pieces of Velcro, so it can be easily removed with no trace in the future. I offered to stain or paint the dowel to match better, but the piano owner said she likes the natural way it looks. The dowel has been in place now for over fifteen months with no problem and the plate strut has been quiet since then too. Bruce Dornfeld, RPT bdornfeld at earthlink.net North Shore Chapter -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech_ptg.org/attachments/20081230/914fe752/attachment-0001.html>
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