At 8:55 AM 2/20/96 -0700, stanwood wrote: >BALANCE WEIGHT factors out the friction!! > >It's the >BALANCE WEIGHT!! _______________________ This may be a good opportunity to beg a little more elaboration as to the nature of balance weight measurements. Previous discussion has been great, but I still have questions. It is clear that the amount of balance weight added to the rear tells us specifically how much heavier the front half of the key is. However, I have also noticed that the value for friction taken from balance weight measurements may slightly increase over what that value was from normal touchweight measurements. I found that friction values as taken from balance weight measurements increased with low leverage shanks, but slightly decreased with high leverage shanks. This would seem to indicate that friction is increased by reduction in shank leverage more than it is reduced by reduction in strike weight. Is the mass that is zeroed out, as opposed to friction? I can easily picture that the process of taking balance weight is really an effort to reduce key and wip ratios to the front half of a simple lever with its fulcrum at the hammer center pin. But specifically, "how does this factor out friction"? Why doesn't the value for friction taken from Balance weight measurement decrease more than it does with high leverage shanks and why does it increase with low leverage shanks (about .5 grams)? __________ I have also had some thoughts on the differences between strike and motion ratios. It would seem that the differences observed between these two ratios lie in whatever friction wasn't factored out and/or minor discrepencies in measurments. I believe that if we could also take balance weight measurments to the nearest .1 gram these ratios would come out closer than they do. An even greater reduction in the differences betweeen SWR and SMR however, can be achieved by measuring the back half of key ratio from point W to P (see Pheiffer, this is value h). This is a line from the balance hole straight up to the capstan contact point as opposed to the protion of a straight line taken from the center of touchweights at the key front. If this method were adopted though, our key ratio standard would change from .5 to about .53. For those who like loose metaphors, I see that SWR is to SMR as fine tuning is to theoretically correct calculations without regard to inharmonicity (a blank page on the SAT). There is no motion involved in measuring SMR. In Pheiffer's book it is called Transmission ratio. Or, to state it in terms of Downweight, this is what I get: SWR/SMR = DW/(SW)(SMR) This equation in this form actually says more, I think, than its reduced form: (SW)(SWR) = DW which says not much at all. Thank you for any comments. Dennis Johnson johnsond@stolaf.edu P.S. When you measure SW from original old parts with worn, overcentering hammers, do you still set the shank level for weighing?
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