---------------------- multipart/alternative attachment Hi Keith I read your post & any one reading this will have a better understanding of the dynamic relationship of action parts in an upright. Nice job. Yes even your mentor learned a few things. I have often weigh upright hammers in the big old uprights we restore & I find the original hammer weight is always light as are the grand from the time period . On the Ludwig upright currently in process & used the AA Wurzen felt with the Maple moldings & I found that even tapering the whole set in my tablesaw jig I was still a fair bit heavier but close enough. I juiced only the bass lightly. The rest of the set got nothing except the usual filing that you & I are accustomed to.I find uprights do not need or benefit from a heavy hammer & that extra weight really tend to kill the sound especiall in the top 3 octaves. Thank you grasshopper Regards Dale 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... 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. 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/95/4b/67/e8/attachment.htm ---------------------- multipart/alternative attachment--
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