Hi David, Thanks for the reply. Thanks for the explainations! The importhant thing is to keep records. So however the data is interpreted it is always there for other analysis. ---ric ---------- > From: David C. Stanwood <Stanwood@tiac.net> > To: pianotech@ptg.org > Subject: Friction Weight=(D-U)/2 > Date: Monday, December 13, 1999 10:45 AM > > Fri, 10 Dec 1999 "Richard Moody" <remoody@easnet.net> Wrote: > > >Also I wonder why a simple differnce between DW and UW can't be used. At > >least for friction reducing attempts. I think it (the difference) is > >divided by two because levers are involved, but at the keyboard the first > >"reading" is the actual difference. Why have to mentally divide that by > >two and remember that also? So would it be wrong to say? "since FW of 10 > >is acceptible, then a diff of DW and UW of 20 is acceptable but getting up > >there." > > Dear Richard, > > I'll start a new subject on this because your focusing on a point that is > important to understand in itself. > > Why not make an action that has no friction! Ball bearing knuckles, ball > bearings in the hammer and wip centers, ball bearing heel cushion, and ball > bearing key pivots and guides. (Of course these would have to be dry ball > bearings so as not to cause any extra drag) > > Now we measure down weight and it turns out to be 35.001 grams and the up > weight is 34.999 grams. But since we normally measure up weight and down > weight to the nearest gram these figures both round out to 35 grams. So > with no friction, Up Weight and Down Weight are the same. > > Now let's spray mist the ball bearings with a mixture of 80% water and 20% > alcohol. > get that water right into those bearing with a liberal soaking! Let stand > for one full day do allow for full rust development. > > Now remeasure Down Weight and we find it has increased by 13 grams. It was > 35 grams, now it's 48 grams. 13 grams is the additional weight needed to > overcome the friction in the rusty bearings. That's why it's called > Friction Weight. Now we measure Up Weight and we find that it has > decreased by 13 grams as a result of the friction in the rusty bearings and > now measures 22 grams. > > So this 13 grams is called "Friction Weight" and in the real world we find > it as: > (D-U)/2. > > As you can see in this case, referring to friction as 26 grams doesn't > really tell you the effect of friction on either Up or Down Weight until > you divide by two. > > Also, the 35 grams in this case, is referred to as "Balance Weight" and is > found as: (D-U)/2 > > In defense of these terms I have to take exception with the comments by > Mark Abbott Stern in his December 1999 Journal Article "Touchweight & > Friction" > > He his introduction he states: > > "The hardest part will be giving up the belief in a widely accepted > statement: "One half the difference between down weight and up weight is > the friction of that note." Not entirely true. Repeat --- not true. > Friction is certainly a part of that value, but there's more to it; there > is a portion that cannot be reduced by all the lubricants in the world." > > He seems to imply that, by using all the lubricants in the world, we have > eliminated friction and since there is still a difference between up and > down weight, it must be from some other cause. He goes on to make the case > that force vectors are the cause of it. > > My take on this is that if we reduce friction as much as we can (and this > is not necessarily desirable) there is still plenty enough friction > leftover to cause a difference between up weight and down weight. > > If we TRULY eliminated friction (Ball bearings) there would be one weight > placed on the front of the key that would cause it to become balanced. The > slightest amount added or subtracted to that weight would cause the key to > move down or up irregardless of the force vectors within the action. > > David Stanwood >
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