This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Mistake 1; Assuming action geometry would solve an upright weight = problem. Mistake 2; Assuming leading would solve an upright weight problem. Mistake 3; Assuming a little stronger jack spring wouldn't hurt. Mistake 4; Assuming...=20 Mistake 5; Assuming.... This is theory, I'm assuming I'm right. I thought action geometry could solve a touchweight problem on an = upright. First clue; I have heard it said (must be an old wives tale), = "you can hang a heavy hammer because the weight of the hammer doesn't = matter in an upright". True. A mistake would be to not lighten the = hammer as much as possible. A too heavy of a hammer will crush the butt = leather and pressure the flange bushing and not have a clean rebound. = However, the ability to accelerate a heavy hammer is there. The key here = is knowing that the wippen in an upright is a 2nd class lever on the = lift and a 3rd class lever on return. In a grand, the opposite is true. = So an upright being a more efficient lift mechanism, mass is less = important. The upright action geometry is designed for proper = distance/movement of the wippen and touchweight becomes a factor of the = spring tensions, a variable, instead of gravity which is not a variable. = You might want to change the geometry if the blow distance was set at 1 = and 7/8" with a key dip of 3/8" and a jack that hits the letoff rail. = Damper lift also needs to be considered. Then the wippen travel might = need to be lessened. Back to touchweight. The jack spring is a significant factor in the = touchweight. I had a 57 gram DW and a 37gr UW. Both the tall Pianotech = spring and the Schaff spring were too tall. I could have determined this = by measuring the height of the jack flange. The one on this Knabe is = short in comparison to the replacement options. So I replaced the jack = spring with a spinet jack spring from Pianotech and the DW became 47 = grams and the UW was 20 grams. I would have thought this was wrong if = Michael Gamble hadn't posted the target weights from the S&S manual. = Thank you Michael. Obviously the jack spring affects the UW far more = than the DW. It functions somewhat as a wippen return spring. It will = aid in lifting more weight at the front of the key. The effort of the = jack spring is a 2nd class lever. The effort of the hammer weight is a = 3rd class lever and so the hammer spring will have more effect on the DW = than the UW. The springs control the DW and the UW. =20 Upward pressure is needed at the capstan. This would be to maintain = capstan/wippen contact during both the up and down movement of the = wippen. This upward pressure is limited by the weight of the wippen and = the low UW and the need of the wippen to drop quickly without the weight = of the hammer. Leading needs to balance the key against the wippen = regardless of hammer weight. The wippen needs to fall on it's own weight = to allow the jack to reset and have lost motion. Leading therefore = should be to balance the keys as an individual component. Any change in = feel will come from the change in hammer weight on acceleration or = messing with spring weights. Please comment, discuss, call me stupid or ignorant but substantiate and = show the way. Keith Roberts kpiano ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/c1/4c/79/af/attachment.htm ---------------------- multipart/alternative attachment--
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