This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment With a .55 key ratio you definitely need a 17 mm knuckle, probably an 18 = mm but they don't make them. Ideal situation would be if the action would accommodate a capstan move to .52 with a knuckle at 17 mm. Variations = in the leading and balance weight with a non conforming SW curve accounts = for the range of BWs through the action. Friction range is too great. = Check the key easing on the high ones and remeasure balance weights to see if that's the problem. Remeasure the bore distance (string height to = flange center) and see if the hammers are bored correctly. Improper checking = might be due to improper tailing or incorrect backcheck angle. =20 =20 Best fix: =20 =20 1. Remeasure hammer bore dimension and either replace the hammers or, after removing from original shanks, plug and redrill if they are wrong = (a little tricky when they are already tailed, but can be done. (4 hours) 2. Dry fit onto new 17 mm shanks and smooth strike weights using a table saw for clean tapering. Retail to correct radius. With .55 key = ratio you will need SWs on the lighter side. Do some samples and determine if your curve will allow you to move the FWs back down below maximums. If = you are unable to get the hammers light enough to bring the BWs down with reasonable FWs, experiment with a capstan move to .52 or as far as you = can without going off the cushion. Double check your new BW/FW relationship with some samples. (4-8 hours) 3. Install new hammers. (3 hours) 4. Bench regulate and address friction areas checking keys and pinning. Include check of backcheck angle and/or new leather. (4-6 hours). 5. Reweigh action by charting BW for each note and then remove lead at 1:1 ratio (1 gram off FW reduces BW by 1 gram) to achieve desired BW. = (4 hours) 6. Take to customer and do final reglation, tuning and voicing in piano. (4 hours) 7. Give bill (estimate 22 - 28 hours plus pick up and delivery, plus shanks, plus new capstans if needed-add 3 hours and a new set of hammers = if new hammers are in order) collect money go home and drink beer. Your mileage may vary. =20 David Love davidlovepianos@comcast.net=20 -----Original Message----- From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On = Behalf Of Farrell Sent: Thursday, August 04, 2005 4:52 PM To: pianotech@ptg.org Subject: Action Balancing/Leverage Quagmire =20 Hello Action Balancing Aficionados, =20 Today I spent a good part of the day with Phil Bondi (who is currently dodging thunderstorms along southbound I-75) diagnosing an 1880s S&S = model A 85-note action that plays like a Mack truck. =20 Because two heads are better than one, and as we found out, they are = likely better by an exponential function, we have at least four times as many unanswered questions as either one of us could have come up with working alone! =20 We actually did improve one thing right off. The drop screws were turned = WAY down to make the pathetically hung crap hammers check - sort of. They = were so far down that the rep levers were being depressed at less than half = blow. We turned them up and that made quite a difference right away. But = still, the action was sluggish. =20 We measured upweight (UW), downweight (DW), key ratio (KR), strike = weight (SW), wippen weight (WW), knuckle-to-center distance (KC) and front = weight (FW) on all the Cs and C#s. Our objective is to characterize what = changes can be made to this action to make for a normal to light touchweight. = All results discussed herein are in grams and millimeters. =20 We also examined magic lines and did the measurements to calculate = overall action ration as specified by Ron Overs. =20 The action had shanks with knuckles 15.7 mm away from the flange center = pin (is that the right distance Phil?). And it had five leads in the bass = keys and two in the trebles. =20 The capstan/wip-heel actually intersected the magic line just after key travel started (not too horribly bad). The knuckle/rep-lever interface started at a full knuckle below the line and ended with the line about half-way across the knuckle at full key depression (pretty bad). =20 For anyone interested in a painful experience, I will send you my spreadsheet with all the data upon request. For those others more = sensible, but still reading this, I will summarize below: =20 DW ranged from 49 to 63. UW ranged from 18 to 28, friction (F) ranged = from 12 to 19.5 balance weight (BW) ranged from 34 to 45.5,=20 =20 What would make the BW so inconsistent? =20 FWs are from at Stanwood's Front Weight Ceilings to about 4g over, KR is = .55 for naturals and .53 for sharps, average WW is 16.5, SW ranged from heavy-medium in the treble to just into the light zone in the bass, = action ratio (R) ranged from 6.7 to 7.5 and averaged 7.1. =20 Clearly, the leverage of this action is horrible - too high. We = experimented with a 17mm and 16.5mm knuckle-to-centerpin distance knuckles/shanks. = They seemed to function very well - you could regulate the notes quite well = (we tried the 17mm on one note and the 16.5 on four notes). However, the improved leverage dropped all the DWs to around 41 and all the UW to = about 16 or 18g.=20 =20 Looking for a bit of input here - this is too light, yes? Too light DW = and the low UW will produce poor repetition, yes?=20 =20 Friction on the high friction notes dropped to 12 or so and BW dropped = to 28 to 30. Calculated R goes from and average of 7.1 to 6.2 with the 16.5mm knuckles - likely down to about 6.0 with the 17mm knuckles. =20 Using the Overs action ratio method (we did not do actual measurements = with the 16.5mm knuckles) I estimate that the knuckle change would drop the action ratio down from the original average of 6.4 to 5.9 =20 BUT, these keys have a whole bunch of lead in them. We are thinking = that, at a minimum, this action needs the knuckles placed out at 17mm from the = flange center pins to improve leverage. Then, that will allow one or two leads = to be removed from each key - remove enough lead to make the DWs in the 50 = gram range and the upweights will gain a similar amount - around 10 grams or = so and end up with about 27g UW. =20 Ultimately, I think, this piano needs a complete releading (setting gradational FWs) new hammers, shanks, knuckles and flanges and = gradational SWs (on some nice SW curve). =20 Don't know exactly what the piano owner will be willing to do - = apparently it is a not-so-well-to-do church. Phil has the action at this point to evaluate it. =20 Anyone care to comment on our thinking here? Neither one of us are experienced with this balancing methodology enough to decide exactly = what to do on our own. And we recognize that maybe we need to do a bunch more measuring also. But we have a start.=20 =20 We'll be very interested in input. Thanks. =20 Terry Farrell (I wonder if Phil managed to drive the 135 miles home in the time I took = me to write this email?) :-( ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/16/e5/22/01/attachment.htm ---------------------- multipart/alternative attachment--
This PTG archive page provided courtesy of Moy Piano Service, LLC