This operation of reducing the size of the knuckle is guaranteed to increase the touchweight and it should do so rather dramatically. If I understand the procedure correctly it will reduce the "action arm" of the hammershank. The "action arm" is a term is physics that defines the distance from a center to a point where a force is applied along with a consideration of the angle where that force is applied. Mathematically Torque = (D * Sin (A)) * F In terms of our action D is the distance from the center to where the force F is applied. A is the angle that that force makes with the line along which D is measured. F is the force. In the piano D is from the center pin to where the jack contacts the knuckle. "A" is generally 90 degrees. The "action arm" is (D * Sin (A)) which in our case is(D * Sin (90 degrees)) . Since Sin ( 90) = 1 then our "action arm" is just D. So if you reduce the size of the knuckle you will reduce the "action arm" length which in turn will require the Force that the Jack applies to the knuckle to be greater which can only occur with more Force at the key. Here is another thought I would like to add to Ken Sloane's comments about this problem. He has it exactly right. His test will work. When the top of the capstan does not line up with this line then it is forced to slide somewhat. This is "kinetic friction" which almost always is lost energy from the system being given away in heat. When the capstan is in the correct place there is no kinetic friction but there should be some friction otherwise the parts will not move. This friction is generally referred to as "rolling friction". If you think of a car wheel you want some friction especially on an icy day. Friction can be our friend or our enemy. In terms of our action the place where the capstan meets the whippen can be looked at as like cog wheels transferring their motion. Although there are no "cogs" you can imagine by such thinking the interaction of the two surfaces having friction as producing the same result. It is for this reason that I'm willing to bet that polishing capstans is a waste of time. The only time that it would produce any effect at all is when there is "sliding friction"; that is, the capstan meets the whippen off of our ideal line. Michael Wathen
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