Lim, This is caused by multiple factors as others have mentioned, but fortunately they can be resolved with tuning technique and a little time. The first is that the strings are not equalized in tension over the bridge. Especially with new pianos with everything going flat from the new wire, the tendency is to pull it up into tune and then settle the pin a little. Unfortunately this can leave the back scale tension low. By pulling it quite sharp and pounding it down you will pull the strings across the bridge. In addition, this technique will settle the tuning pin in a position that is not twisted in the sharp direction inside the pinblock. These undersized pins tend to twist a lot during tuning, so by pulling it up 15c or more you are making sure the bottom of the pin has spun into position, then you settle it down again into a stable location. So in the technique you saw Otake-san use, the pounding wasn't doing all of the pitch lowering. You pound to get the string to move over the bridge, but at the same time you settle the pin back into a stable position. Once this hard tuning job is done and the strings and pins are settled, you don't have to pound it like this every tuning. In my experience you do this once or twice on a piano, and it will be stable after that unless humidity changes are large. In that case you might need to do a pin-wrestle job once a year or so. Finally, these large Kawai models have pretty substantial friction under the capo bar. This is done intentionally for tonal reasons, but it means that the tuning technique is different compared to a low friction piano, or compared to a piano with springy pins that have no plate bushing. So the technique for these pianos is different - but once you get used to it, it becomes automatic like any tuning technique you do regularly. The trick for the final stability is to do the last small unison adjustment UP to the final pitch instead of down. With these pins that don't spring much and the friction in the strings, this will tug the string through the capo and leave the tension in the front duplex high, leaving the string very stable. If you settle down to final pitch for unison tuning, the front duplex will be quite low in tension compared to the speaking length, and on the first loud passage the unisons will be out. If you settle up to the final pitch, the unisons should stay. Don Mannino RPT -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of limhseng at gmail.com Sent: Tuesday, September 21, 2010 6:34 PM To: pianotech at ptg.org Subject: [pianotech] Tuning stability problem Hi When a grand piano sits on a Y type trolly, will there be tuning stability problems? I tuned a SK7 which sits on a Y trolly and I have a hard time on the octaves and unisons from key 55 onwards. Regards Lim Sent from my BlackBerry Wireless Handheld Powered by Gee! from StarHub
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