---------------------- multipart/alternative attachment Dear List- During our discussion of inertia in piano actions a few months ago, Jim Ellis presented some of his thoughts on the problem, including the suggestion that weighing off should be done relative to a target balance weight. I liked his thoughts, and intended to try them as soon as I could. Opportunity came in the form of a small Knabe action in which just about every design decision was wrong. To interpret Jim's idea, I made three pairs of weights, representing varying amounts of friction with a 37.5 gram balance weight, thus: 25u+25=50d; 22.5u+30=52.5d; 20u+35=55d. In each weight pair, the first weight is the upweight, the second added to it produces the associated downweight. I found these weights delightful to work with, as they enable you to assess the action in terms of relative speeds. The goal is to produce equal speeds of and down movement for each pair, but faster as you compare the 25/50 weights with the 22.5/52.5 weights and then the 20/55 weights. On this action I made several geometry changes (increased the hammer weight, shortened the wippen heels, changed the capstan angle and finally moved the natural capstans forward to equalize the key ratios with the accidentals). Observation with the weight pairs made the improvements of each change very obvious. Finally they led me on a fine chase for tiny friction devils. Seeing the action move this way makes tiny moments of friction easy to spot. For instance, things may move smoothly with the 55 and 52.5 gram pairs, but there will be a slight delay with the 50 gram downweight. This could be just a fuzz between wippens or a rough place on a keypin. Although it may seem complex in description, in practice it was a fast and easy way to work through the weigh off. Comparing the speed of hammer movement with two pairs of weights gives very clear information. The amount of time spent wondering, subtracting and second-guessing was minimal. My hat's off to Jim for this idea. Ed Sutton ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/caut.php/attachments/e7/0b/68/4c/attachment.htm ---------------------- multipart/alternative attachment--
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