Less bad is always better... David Ilvedson, RPT Pacifica, CA 94044 ----- Original message ---------------------------------------- From: "Greg Newell" <gnewell at ameritech.net> To: "Pianotech List" <pianotech at ptg.org> Received: 11/25/2007 6:19:14 PM Subject: RE: Steinway action noise >Ric, > First, thank you for your interest in my customers dilemma. I at >least recognize that it's their problem and not mine. That's a good thing. >Secondly you have on a few occasions mentioned the desire to obtain the old >parts. Oh that that were possible. They and the technician who did the >previous work are gone I'm told. It will take me a while to digest what >you've written but the short version is that I'm aware that there will be >some complications however, 1) it will be a good learning experience 2) I'm >not likely to proceeed further than what they are willing to pay for and 3) >I have no choice but to proceed in some fashion to make this .... less bad. >Thanks again for the efforts. >-----Original Message----- >From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf >Of Richard Brekne >Sent: Sunday, November 25, 2007 4:12 PM >To: pianotech at ptg.org >Subject: Steinway action noise >Hi Greg >I was curious as to what is happening with your troubled action. I got >asked to defend my skepticism to moving the whippen flange out in the >case your original hammer flanges had their center pin holes 1 mm >closer in to the flange mounting screw. I havent had time until now to >put out some rough numbers but here goes.. and perhaps you will see why >I opt for trying to just keep the old flanges in this situation. >To begin with, if you have hammer flange centers 1 mm distal from >originals and paper your whippen flange 1 mm out to match then all you >have done is basically to move the stack distal 1 mm and the hammers >inwards 1 mm to keep the same strike line. Thats where a large portion >of whatever change in ratio will occur. >I'll give a simplified example. Start with a say 5.25 ratio comprised of >a 7.0 shank ratio, 1.5 whippen ratio and 0.5 key ratio. >Assume also the following parameters. >Hammer center moulding to center pin 136 mm >Bore length 48 mm >Knuckle core to center pin 16 mm >Whippen center to cushion/capstan contact 62 mm >Whippen center straight up to the contact point of the jacktop /knuckle >93 mm >This is all basically following Overs way of measuring the ratio. >Yeilds an hammer shank long moment arm of about 144.34 and a short >moment arm of 20.62 >Now if you just move out the whippen and shank flanges distal 1 mm and >the hammers in 1 mm to keep the strike line...then the shank ratio drops >to about 6.954 from 7.0 In addition the whippens ratio changes >slightly. The long arm is typically about around 30 degrees out from >the horizontal line from the whippen center and the lower arm about >18-20 degrees. This means a horizontal move of the whippen flange center >will lengthen the upper arm slightly more then the move will add to the >lower arm. Using 18 and 30 degrees the moment ratio drops to 1.4933 >The new total action ratio is then 5.19. (6.954*1.4933*.5) >Using the same calcs if you've installed 17 mm knuckle length and move >the whippen flange out 1 mm more to keep the jack on the parallel with >the knuckle core the whippen ratio drops to around 1.487 and the hammer >shank ratio changes to 6.72 which gives 6.72*1.487*0.5 = 5.0 for the new >total ratio. Thats beginning to be a significant drop. >In itself not necessarily a bad thing... but there is another situation >going on here I am less comfortable with. A distal horizontal move of >the whippen flange center also changes the effective travel of the jack >tip fairly significantly. In the above example you are roughly 58 mm >straight out from the whippen flange center to the point on the lower >arm directly above the whippen cushion / capstan point. If the key moves >that say 5 mm upwards, then a jack tip that is 120 mm away from the >flange center will move about 10.3 mm. (of course the jack tender will >get in the way but I'll get to that.) With a 2 mm distal move of the >whippen flange center jack tip rise is reduced to 10 mm. The jack itself >is a roughly 2:1 ratio lever so the jack top will move twice as much as >the tip. Since it comes into play about 80 mm into key dip you are >looking roughly at a 0.5 mm reduction in jack top travel. >None of this even gets into the fact that with a move of the flange >center by itself (as in the case of compensating for the 16 to 17 mm >knuckle distance difference) requires you to lower the capstan so as to >get the same blow distance... which again changes the jack angle >slightly outwards. In reality, going from 16 to 17 mm knuckle difference >requires a bit more of a 1 mm distal move of the whippen flange center >to maintain both the same blow distance and the jack being on line with >the knuckle core. At the same time it reduces jack travel slightly... >enough to have an impact on letoff and drop timing. To maintain >simultaneous contact you will have to lower the let off button. But the >jack wont come out from under the knuckle quite as far (key dip staying >the same). >There is more one could get into here if one wanted to...such as jack >stop cushions (both for and aft)...etc, but I think this all sort of >explains why I prefer to stick with the original hammer shank flanges >instead of papering the whippens out. >On the other hand... if the whippens were too close in to begin with... >well thats another matter. >Hope this clarifies somewhat... sorry about the length but even general >numbers force a bit of explanation >Cheers >RicB
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