At 08:55 AM 11/5/98 -0500, you wrote: >Plate brace compression? Really? When I'm tuning with the RCT using the >same tuning file as last time, where the piano has gone slightly flat, >I'm finding that the pitch is most flat next to the braces, and changed >little in the areas between. This runs counter to the test results given >below! (unless pitch raising/lowering arouses a different reaction than >normal tuning change over time and weather change does.) This leads me >to suspect it's the empty spot on the bridge causing the change. Typical >change from six weeks ago-- Dead on in the middle of sections 2-3 cents >flat next to braces, and ofcourse drasticly off at bass break.) >Bridgemakers!, What is the proper term for that empty spot at section >breaks? > >-Mike Jorgensen RPT --who tunes all CMU pianos every six to eight weeks. > Hi Mike, Is that with braces corresponding to - low tenor, and the killer octave? I'm told it's the bridge length changing somewhat that accounts for most of the low tenor movement, and I'm still convinced it's the soundboard moving in the killer octave. Interesting thought on the bridge ... gully, dado??? Loss of stiffness there would allow more movement. That's tuning stability though, and not pitch drop during pitch raise, which is what the original discussion was about. Raising pitch, I still think soundboard deflection accounts for a big part of the necessary overpull, even though plate flex is contributory. That more flexible area of a dado'd bridge should drop more too. I never thought of it before. I'll try to remember to keep track. Ron
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