The string scale on this little piano actually wasn’t too bad. The downbearing was plotted and then calculated at 686 lbs.
To hold up that 686 lbs, the original rib scale of 10 ribs had the appropriate size of 7.06 square inches.
There was one problem found however that needed to be fixed. The rib scale distribution was not in sync with the load distribution. This of course leads to the situation that some ribs are working harder than others. Creating uneven stresses throughout the soundboard.
The graphs.
(Note: The dark area at the bottom is the load distribution. The vertical bars are the rib sizes. The line marks the stress levels.)
Before:
After:
Load, rib sizes and stresses all synchronized.
One surprise came in the deflection values. Although I made the ribs shorter in height (from 96% down to 73%), the deflection was less, not more. Increasing the soundboards efficiency.
Data:
Original:
Modified:
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ChrisChernobieff
Chernobieff Piano and Harpsichord Mfg.
Lenoir City TN
865-986-7720
chrisppff@gmail.comwww.facebook.com/ChernobieffPianoandHarpsichordMFG------------------------------