Pianotech

  • 1.  Center Pin to Knuckle Center

    Registered Piano Technician
    Posted 08-04-2023 13:27

    1980 S&S M with teflon is getting new HS&F.  What will be the ratio effect, positive or negative, if I use 16.2mm pin to knuckle shanks when the originals are 15.5mm?  I could figure it out but it's hot today.



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    Gary Bruce, RPT
    Bruce Piano Service
    Edmond, OK
    405-413-TUNE
    www.brucepiano.com
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  • 2.  RE: Center Pin to Knuckle Center

    Registered Piano Technician
    Posted 08-04-2023 14:49

    The net effect will be to lower the action ratio somewhat.  that kind of change from 15.5 to 16.2 probably lowers the balance weight by 2 to 3 g if you're using the same hammers. If you're changing hammers, then you'll want to consider whether 16.2 is adequate given the weight of the new hammers. So the answer is a little bit more involved than you've given data for.

    I have another thread going in which I'm doing some beta testing on spreadsheet calculations for exactly this purpose so if you'd like to participate in that contact me privately I can give you some information on how this will pan out if you're able to take certain measurements. 



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    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
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  • 3.  RE: Center Pin to Knuckle Center

    Registered Piano Technician
    Posted 08-04-2023 19:07

    You might want to get a read on the physical weight of several hammers throughout the set for comparison purposes. What hammers will you be installing?

    Peter Grey Piano Doctor 



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    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
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  • 4.  RE: Center Pin to Knuckle Center

    Registered Piano Technician
    Posted 08-05-2023 00:53

    Gary, You could fool around with this: http://www.goptools.com/action_ratio.htm

    It's basically a knock-off of Nick Gravagne's original action geometry program. As there are several ways to measure Action Ratio it will probably only give you a general idea of the effect of center pin to knuckle center distance changes.



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    Tremaine Parsons RPT
    Georgetown CA
    (530) 333-9299
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  • 5.  RE: Center Pin to Knuckle Center

    Registered Piano Technician
    Posted 08-05-2023 09:28

    Assuming same hammerweight,  result will be higher downweight and lower upweight



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    Parker Leigh
    Winchester VA
    (540) 722-3865
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  • 6.  RE: Center Pin to Knuckle Center

    Registered Piano Technician
    Posted 08-05-2023 16:24

    Correction,  moving knuckle away will result in lower down weight  assuming hammer weight is same as originals



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    Parker Leigh
    Winchester VA
    (540) 722-3865
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    Original Message