I am studying a 1977 Yamaha C3 in our university collection which I believe has its original parts, and shows no evidence of modification, other than routine hammer reshaping. The hammers appear to have lots of life left in them -- the piano has apparently seen light use.
I am trying to get my head around the design intent in terms of how this action was originally set up. Let me start with some observations. My frame of reference is, for the most part, the manual from the Stanwood Touch Designer's Tool Kit. I mention this so that it will be clear what I mean when I speak of strike ratio. For any who are not familiar with this protocol, Strike Ratio is defined as (Balance Weight + Front Weight - Wippen Balance Weight) divided by Strike Weight. I am not dealing with radial arms ratio, mass action ratio, or the amount of hammer rise for 6 mm of key dip.
There is a significant amount of lead in the keys. Compared to what Stanwood identifies as a Front Weight Ceiling, values in the action are high. Of the 18 samples measured , the trend line of the naturals starts at 1 gram below the ceiling at note 1, and rises to 5 grams above at note 88. The trend line of the sharps starts at 5 grams above the ceiling, heads up a gram or two through the tenor section and then returns to 5 grams above the ceiling in the high treble.
Strike ratio for the sharps is significantly higher than strike ratio for the naturals. Naturals come in at an average of 5.8, and the sharps at 6.4.
Strike weight trends at Stanwood 1/2 medium, rising to 3/4 medium in the high treble. Hammers have been reshaped, but do not appear to be anywhere near end-of-life. For what it's worth, I consider this a low weight range.
Balance weight of the samples averages 34 grams. The high is 38 and the low is 28. Downweight averages 43 grams.
Projecting out from this data, I observe that in order to have balance weight in the 38 gram range, the original strike weight zone would have needed to be something like Stanwood 3/4 high, which would have hammer #1 weighing in at around 14.2 grams. Does this make sense? Did the 1977 C3's come with really heavy hammers? Have these hammers been sanded down way more than I realize?
What might have been the rationale for the big difference in strike ratio between the naturals and the sharps? If you were doing a touchweight regulation on this piano, would you change this? How else might you handle it?
If I proceed to rework the touch weight on this piano, I am inclined to adjust strike weight upward to at least Stanwood 3/4 medium. If I did this, left the action ratio alone, and shot for an average balance weight of 36 grams, my front weight for the sharps would sneak in at just under the Stanwood front weight ceiling, and my naturals would run at 7 or 8 grams below the ceiling. That would produce a pretty low downweight in the naturals.
On the other hand, if I changed the action ratio for the sharps, either by moving capstans or by cutting balance rail punchings, I could raise the balance weight for the naturals to what I would consider a more natural range.
How would you approach this?
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Floyd Gadd
Regina SK
306-502-9103
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