Hi folks Here's a cute little fact perhaps not all you touchweight enthusiasts are aware of. In anycase I just stumbled upon it yesterday evening dinking around with spreadsheets. The key ratio can change without changing the top action ratio if you execute the change at the fulcrum instead of the capstan. An old trick for doing this is too glue a tiny peice of veneer to the underside of the key just behind the balance rail pin... or something simliar... but what effect does this actually have on BW ? As it turns out it affects note 1 about twice as much as note 88. With fairly standard values a 0.01 change in key ratio will change BW by 1.5 gram roughly in the lowest bass, 1.1 grams in the middle of the piano, and 0.75 grams in the highest treble. Heres a little spread sheet that shows what happens. You can change the input values for the top action ratio, the key ratio, the whippen weight, and the desired BW. You can also change the range of SW's and the range of Specified FW's. The SW collum uses the ratio, whippen, and desired BW data to calculate the corresponding Stanwood FW values for reference. The Spec FWs collum uses the ratio and whippen weight along with the SW range to calculate the resulting BW. Just change for different combinations of SW, top action ratio, and key ratio and watch what happens to the BW for the sample values in the sheet. http://www.pianostemmer.no/files/kr-to-bw-effect.xls Sort of implies a neat way of getting away with heavier hammer curves in the bass... a 0.01- 0.02 KR change in the bass isnt going to cause allllll that much differnce in needed key dip / blow / letoff conditions. But it will allow from 1.5 - 3 grams of decreased BW.... which can be turned around in terms of either heavier SW values (1-2 curve up) or lower FW values (1-2 corresponding curves down). Cute eh ? Cheers RicB
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