JIM writes: Unless I'm completely missing something, the reason the right side of the equation can't make proper sense with the left is that the action actually has a variable ratio. NICK writes: I see that the right and left sides do balance if understood properly. But, yes, what we call the Action Ratio is variable from beginning to end of key stroke; still it is a useful average. J: As I see the equation, it is assuming the ratio @ 1/2 stroke is constant throughout the entire key stroke = not true. N: Correct in that the ratio figured at half-stroke is not constant. I have worked out derivatives to show the ratio at any partial key stroke and hammer blow; a nice exercise but doesn't yield anything useful. The average is useful, assuming we all agree on the meaning of a 5.5 as it differs from a 6.1. J: Action ratios seem to me to be confusing designations... N: Yes they can be confusing. But, again, assuming we measure the same way and understand the average thing, we should have (and mostly do have in my view) a useful relative standard. J: since you really are talking either about an average (I don't see that factored into the left side), or a fictitious static number. No? N: if referring to the EQ (keyout/key in) x (wippen out/wippen in) x (shank out/shank in) = (blow distance - letoff)/(key dip-aftertouch) the average is factored into the left side in that the "shank in" lever is measured when the key is at half stroke. As to a static number, we are not considering statics or dynamics, only ratios and measurements. Hope this helps. Nick Gravagne, RPT Piano Technicians Guild Member Society Manufacturing Engineers Voice Mail 928-476-4143
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