Cheers Ric and all, I'd like to reiterate my take on the "happy marriage" between distance ratio and weight ratio which is this: Distance ratio divided by Weight Ratio represents what I call the "Efficiency Ratio" it's a ratio of ratios. What I'm finding is that if the efficiency ratio is 1.0 or higher then your going to have success with low ratio/high leverage actions. If it's below 1.0 then your going to have to cram the blow too much and settle for a too much dip... I'm talking actions with Strike Weight Ratios in the mid to low 5's. The most efficient action I've measured had an average strike weight ratio of 4.8 and regulated with a .390" dip and a 1 3/4" blow. It was an older Bosendorfer. Someday I'd like to revisit that action and look at the geometry to try and figure why it's set up so well as well as determine it's E-ratio. I imagine too that with higher ratio actions that the E-ratio is important too.. but it's less of an issue with regulation... There was a time when 1/4 inch dip was normal.... the older Erards... I've only studied one in Holland... it had a 6.6 weight ratio and a 1/2 to 3/4 low strike weight level. But alas! a sample of one piano has the least meaning.... I'd like to do nothing but pure research but vocation calls! Frank is right about measuring ratios...it can be dicey... that's the real world.... One has to act like a scientist (not a rocket scientist!). Techniques have to be standardized and repeatable with statistical methods followed. I like to take a minimum of 6 ratio samples... middle c,c# and double octaves below and above middle C.... that would be notes 16,17,40,41,64, & 65. Dale Erwins little jig by Spurlock is a very nice quick survey method... gets you right in the ballpark. But I would not consider it a highly accurate scientific method. Little variations in the key level, reading the scale, or regulation can skew the result... The method I use measures the hammer movement to the nearest tenth of a millimeter. I use a digital caliper to control the downward movement of the key. I block up the rep lever height button so that the knuckle is sitting only on the jack without support of the rep lever which might skew it.... I'm awed by technical CAD and computer tech skills that folks like Frank Emerson, Scott Jones, Bruce Clark and others are putting to use... it's all relevant and it all goes into the mix of shared knowledge thanks to the Internet..... we've come so far in the last decade... it just get's more and more interesting, relevant, and useful! Gotta run! Ciao, David S >Hi Frank. > >I would have thought the same until the example given by Gene. Seems >to provide a contradiction whereby clearly the weight ratio was the >more dependable. Of course we have to await more info from Gene on >this... but I'd actually like to get to the bottom of what causes >the apparent discrepancy between the two protocols. > >Stanwood will be the first to acknowledge that ratio taken his way >versus a distance ratio will yield different results at least as >often as not, if not more so, and he has done some comparative work >to find a happy marriage between the two. But I dont think he's seen >such an extreme example as Gene's seem to be at the moment. > >Cheers >RicB > > .....Dale Erwin's practice of measuring hammer movement for a > predetermined key movement is much superior for determining the > ratios. This automatically makes allowance for the vertical and > horizontal components of movement of every action part. Similarly, > calculating the ratio from weights rather than distances returns > more accurate values for action ratios. The problem with physical > measurements is that it is often difficult to accurately measure, > visualize alignment, avoid being deceived by parallax influences, > etc..... > > Frank Emerson
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