Bob Davis rote, 1/17/96: <<Does this mean adding a gram weight to the hammer and seeing how much you have to add to the front of the key? If so, it seems to me that measuring the strike ratio in this way would include some friction, and that a more direct measurement would be to measure the ratio between key movement and hammer movement.>> Yessiree, Bob. As you suggest, there are two ways to measure the action's leverage ratio: distance and mass. I would be interested in the leverage ratio as read by distance when linear (actually, angular) relationships were the problem. IOW, if a standard 45mm blow was requiring a dip shallower than 9mm, say 7mm, I'd know it was because the overall action leverage ratio was more like 6.4285714:1 instead of 5:1. But if you've noticed anything about this discussion, it's that the germinal problem is not one of unexpected keydips and blows, but rather that action resistence gets blown around the bend anytime we change parts (hammers, shanks, knuckles, reps, you name it). This is where the ability to read action leverage by mass is so important. <<........it seems to me that measuring the strike ratio in this way would include some friction>> The key to all of this is that as soon as you move from down and up weights to balance weights, you've answered the first big issue in touch resistence, namely, is your problem one of friction or of mass. So many people describe touch resistence in terms of down weight (and if we're lucky, up weight as well), but this is meaningless to me without the differentiation between the two kinds of resistence. They actually feel different. Friction is pushing against you in both directions. Your fingers know very quickly that "the parking brake is on" and that were it not for the finger's pressure the parts would slog to a stop. In the business world this would be called an operating expense--you have to be paying out on it continually. Mass however is more like a capital investment. Depeding on the extent of mass resistence, there is a certain up-front expenditure of energy as the speed of the parts accelerates to meet the speed of the finger coming at them. Once this initial inertial lag has been ovecome, the parts have a momentum which can very often carry them all the way to the string. (Once again in the business analogy, after you've invested the energy to get things in motion, this motion is itself a form of equity which can sustain the the system throughout the continuing operating expense of friction.) I liken mass (or gravitational resistence) to the springiness of a membrane. Let it slack and it moves with little pressure and has very little pressure with which to return. Stretch it taut, and you know you're pressing on a spring which presses back at you with equal firmness. Notice that I qualified this mass resistence as gravitational. That's because I was refering to Balance Weight. BW of course is the median of the down and up weights on a note, and BW strips the gram resistence figures measured at the key's head of friction. But BW really only tells you how much heavier the back half ofthe key is than the front half, which is in essence the net gravitational force on the key. Inertia is yet something else: (did you guess it, not the difference of both sides of the key but their sum.) Currently David Stanwood has us keeping track of the latter by making sure that the hammers' strike weight is compatible with the action's overall leverage. It couldn't be more obvious: a higher leverage ratio will make a given hammer feel heavier at the key head, and make a heavier hammer unbearable (nolo pun contendere). It comes down to tuning up mass and leverage. So that's why I like BWs. Mass and frictional resistence should be distinguished because each has separate remedies. You wouldn't want me to "fix" tight key bushings with Jiffy leads, or to alleviate an overweight hammer by bringing the hammer shank pinning down to 0.5g friction? If all I have is a downweight, the measurement tells me nothing, and if I know enough to look at the upweight also but not enough to strip friction from mass in derive a balance weight, then my gram weights haven't told me anything about mass and friction and which of those two is giving me the undesireable resistence. That's why I like Balance Weights. Bill Ballard RPT NH Chapter PTG "If we see you SMOKING we will assume that you are on fire and will take appropriate measures".......Sign in a Music Dept. Hallway
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