This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Roger/Newton: In this case it is new parts. Renner wippens, Abel shanks. Center pins = are fine everything is lubricated properly and adequately. I am aware = of the static friction element but it seems more than that. I do = notice that the leather on the Abel shanks is much different than the = leather on Renner shanks, which I have generally used in the past. The = Abel knuckles seem not as smooth and soft as Renner's. Any comments on = that? =20 David Love ----- Original Message -----=20 From: jolly roger=20 To: pianotech@ptg.org=20 Sent: August 24, 2001 10:13 AM Subject: Re: hammer acceleration Hi David, Are you noticing this on new parts? Once static = friction is broken, I have noted that this happens more frequently with = worn or loose keybushings. e.g. Changing a prehung set of Yamaha = shanks, with out rebushing keys. At one time I used to change just the = hammer sets at the University. Now I insist on rebushing keys along = with hammer replacement. It makes a big difference. If the friction is high on the knuckle and centre pinning friction is = very low it can give similar results. To trouble shoot. Remove a hammer = and wippen assembly, and measure the friction of the flange C/P's, = Holding the flange horizontal, if it drops under it's own weight, will = give you a quick check, but start measuring and repinning if there seems = to be problems. This eliminates these as the cause. Next examine the = capstan, and wippen cloth, polish the capstan, and if it's old capstans = steam out the cup, dry iron smooth, and burnish in some teflon powder. FWIW. I have repinned more than one set of flanges on new parts. =20 With friction happening with the right amounts in the right places, = the key should go down nice and and steady. Many new Korean pianos have = way too much friction on the knuckles, shrinking the C/P bushings has = been a common practice to over come friction. It will mask the problem, = and give acceptable DW readings. Change the knuckles, and WOW, watch = the the friction figures change. To to look at geometry issues you have to start with the magic line, = key ratio, etc. The old adage, "divide and conquer", applies here. Just eliminate one = thing at a time.=20 Regards Roger At 09:00 AM 8/24/01 -0700, you wrote:=20 I notice, when I am doing a weigh-off on a key board, that on some = actions as the hammer rises the acceleration is relatively slow and = steady. Other times, once the hammer starts to rise, the acceleration = is quite rapid. What is responsible for that difference? Friction = would seem to be the logical answer, but friction where? I heavily = lubricate actions before I do a weigh-off. There seems to be something = else at work in the geometry/leverage. Among other things, with the = rapidly accelerating hammer, it is more difficult to determine the = measured downweight. I there any way around that problem? =20 David Love ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/44/eb/0d/e3/attachment.htm ---------------------- multipart/alternative attachment--
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