On 9/22/07 1:17 AM, "Richard Brekne" <ricb at pianostemmer.no> wrote: > It should be mentioned tho > that the ratio measured is not the same ratio as the Stanwood ratio... > nearly every instrument will end up yeilding two reasonbly significant > different results when both ratio measurements are the same. And tho I > have yet to check it... I dont think either of them are the same ratio > as the Overs method.. which is more akin to what designers operate with. Yes, I have noticed marked discrepancies when I have done these three ways of determining key ratio, plus another rather simple one that I think may have originated with Bill Spurlock: add a known weight (I like 2 gm) to a hammer (binder clip or the like) and see what that does to DW and UW. Why do these four methods yield such different results? Anyone know? I figured that the friction component could muddy the waters with weight based tests, but figured the Erwin style would at least come close to mirroring the Overs style ("Overs style" meaning measuring the 6 levers: key front and back, the two wipp levers (capstan/center and center/jack top), and the shank levers(center/knuckle jack contact and center/strike point), and doing the simple calculation). But they don't seem to come nearly as close as I would suspect, even with the most precise measurements I can come up with for Overs style. [BTW, in a slight variant on Erwin's, developed independently, I set dip on a sample to exactly 10 mm, lower the capstan to just above cushion, raise letoff so that it doesn't start during that 10 mm, then measure hammer rise for full dip. I like dividing by 10 <G>, it's easy, having more or less full dip makes me feel better than a sample portion, and the larger distance seems like it might yield more accuracy. Maybe, anyway.] At any rate, I tend to agree with Keith Roberts and, I guess, Dale Erwin (I wasn't directly aware of what he was doing) that "input/output" or "distance down/distance up" (key/hammer) is the one I would be most likely to take to the bank. Though I admit I am intrigued by Ed Foote's comments about ratio changing in relation to the convergence pattern of capstan to wipp heel. I just don't get why the down/up ratio should vary so much from a simple, lever measurement based calculation. Regards, Fred Sturm University of New Mexico
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