This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Roger: It is a Steinway from the 1980's and its a bit of a mess. Sharps and = naturals have different key ratios (oops). The Renner wippens I put on = have a higher profile which forces the capstans a bit lower, but it = actually put the cap/heel contact more on the convergence line than it = was. I wonder if a longer knuckle radius would result in a faster rate = of acceleration through the swing arc. And if it does, would that = contribute to a feeling of less control because once the static friction = is broken the key would accelerate more easily, i.e., it might feel like = the key is flying away from you too fast? Just a thought. David Love =20 ----- Original Message -----=20 From: jolly roger=20 To: pianotech@ptg.org=20 Sent: August 25, 2001 3:19 AM Subject: Re: hammer acceleration Hi David, The Abel shanks are lighter than the Renner, this can = add to you observations. Also no graphite depending on the humidity in = your area, this can be a significant difference re friction. These are = the two reasons I prefer the Abel shanks. It's been a while since I used Renner shanks, so things may have = changed. I have not noticed any thing amiss with any of Wally's knuckles with = regards to friction, and I know he is very vigilant with regards to = dimensions, alignment and friction. He gets a lot of feed back, so = talk to him, he may have some extra ideas. Is this a Steinway? If so the capstan and heel geometry is critical. = 1mm change can mean a whole lot, so check carefully. Just some random thoughts. Roger At 11:48 AM 8/24/01 -0700, you wrote:=20 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=20 Subject: Re: hammer acceleration Hi David,=20 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.=20 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.=20 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.=20 To to look at geometry issues you have to start with the magic = line, key ratio, etc.=20 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/00/5b/50/eb/attachment.htm ---------------------- multipart/alternative attachment--
This PTG archive page provided courtesy of Moy Piano Service, LLC