Ok folks, David has come out with better and important information. Heed it well. Newton "David C. Stanwood" wrote: > > Newton, > > Some comments on your recent post: > > >Would measuring the weights at three or for velocities give an idea of > >inertia? Inertia is a major consideration of drive head arms so you > >may have some information or ideas in this area already. > > An increasing number of technicians find that they can control inertia > by choosing hammer weights that are compatable with given leverage ratios. > > This means looking at Hammer weights and Shank Strike Weights before the > hammers are hung, or Strike Weights if measuring after the hammers are > hung. The trick is to know what leverage components work with what hammer > weights. This is basic engineering 101. If the rock is too heavy get a > lighter rock or a stronger arm or both! High ratio actions like 1:7 are > totally intolerent of hammer heaviness. 1:5 actions can handle the heaviest > hammers made. Then there is all the stuff in between. > > The most common mistake that techs make is to use a knuckle that is 15.5mm > out on the shank as the original parts were, then using a heavier modern > weight hammer. For Today's hammers the most succesful part is the Hamburg > style shank with the knuckle mounted 17mm out from the hammer center. > > Leverage is made more complicated by the fact that key ratios vary from one > Steinway to another. I strongly recommend that any tech who is replacing > parts, learn how to use a standardized method of measuring key weight ratios > or key distance ratios and keeping notes on what key ratio works best with > which > part and hammer weight level. > > Lack of attention to these details lends an aspect of "rolling the Dice" > to our work. Take measurements and keep a notebook!!!!! > > >The current practice is to remove the front most key weight then place > >a 20 gram weight on the key then set the down weight by moving weights > >back and forth on the key then using differing weights determining how > >much weight the key will lift, this gives the friction of the key. > >Then use a set of up and down weights predetermined by friction and > >desired balance weight and cut a weight down until it will achieve the > >goal by placing it into the vacated hole. > > Don't forget to always cross check the down weight. As a rule of thumb, > if it's above 50 grams check friction. > > David Stanwood
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