Hi Fred I have to admit that my motivation for measuring the ratio as I do is motivated from the same sense of uncertainty connected to the need for taking UW and DW measurements, which can IMHO be quite iffy. Further... getting a ball park figure measuring one key is a much quicker affair. Those who are comfortable with Stanwoods way no doubt find it comfortable enough and that is of course just dandy for whomever. But as Keith pointed out in is opener on this, if you know what you are doing can indeed start with just about any reasonable way of measuring the actions ratio and achieve a fine result. If you are after a certain BW, then you will have to find a way of compensating for what ever built in discrepancy there is between the Strike Weight Ratio, and the actual ratio you have measured, but that is easy enough. One thing that hasnt been mentioned about doing it the EAR way, or like you do it, or as I do it is that whatever discrepancy there is is absolutely uniform for the whole action, and thus any compensator in a formula for figuring key radius weights can be just as uniform. I generally install a Strike Weight curve I know I can counter weight with moderate key leading amounts... then temporarily lead 4-5 C's to see how close I am to my target BW. My spreadsheet for this takes input values for Ratio, Hammer Radius Weight, Whippen Radius Weight and Target BW and outputs Hammer Radius Weight's. You can actually adjust any of the inputs to compensate for whatever discrepancy in the Target BW from the actual resultant one that emerges from my 4-5 samples and then recalculate all FW's to get dead on your BW target. Eds point about the ratio changing through the key is valid regardless of how you measure the ratio when it comes down to it. I believe on Overs site he mentions something about the need to take into compensation the angles at which the parts are designed to be in their rest positions to get the correct reading... because it will be different if you measure same in another position. That is to say it will be different if you first figure in the angles to begin with. Again tho... as long as you compensate appropriately somewhere along the line... you can achieve exactly the BW you set out to. Cheers RicB 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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