Pianotech

  • 1.  Backcheck Setting

    Registered Piano Technician
    Posted 11-01-2022 10:44
    Can you summarize the correct arcs of the hammer tail and the backcheck  in the grand action.  I read in the Journal years ago that getting these arcs right was key to checking.  Can't find the article now.
    (Yes, I can't get it to check: 1 up high,  2 on soft blow)

    Jonathan Langham, Registered Piano Technician


  • 2.  RE: Backcheck Setting

    Registered Piano Technician
    Posted 11-01-2022 11:27

    Jonathan,

    These may seem like odd questions, but I must ask. First: are they new hammers that may have been arced incorrectly? Second: What size grand piano is this problem persisting in? The length of the keystick has a lot to do with checking quality.

    Roger



    ------------------------------
    Roger Gable RPT
    Gable Piano
    Everett WA
    (425) 252-5000
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  • 3.  RE: Backcheck Setting

    Registered Piano Technician
    Posted 11-01-2022 13:26
    The piano is 68" long.  the keys are 496 mm = 19 1/2" long.  454 mm = 17 7/8" from keytop end to backcheck wire.
    It is an old piano with new hammers.

    Sincerely

    Jonathan Langham, Registered Piano Technician





  • 4.  RE: Backcheck Setting

    Member
    Posted 11-01-2022 13:49
    A general rule I start with is with a ~3" tail arc. Tail length ~27 mm. The b/c should be level with or 2 mm lower than the hammer tail with the hammer held in the 'drop' position. The b/c angle should be between 68 and 72 degrees (b/c covering/face to the key).  There are varying conditions which cause variations from this. There are also preferred aspects (mentioned above) as there are piano techs.  Mostly you have to go with what makes it work. Key dip, blow distance and repetition spring strength are important too.

    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 5.  RE: Backcheck Setting

    Registered Piano Technician
    Posted 11-01-2022 14:22
    Thanks, Jon Page.  I will play with those specs. I know one thing affects other things and I will have to get everything aligned optimally.  This piano was free and I want to learn all I can from it.

    Jonathan Langham, Registered Piano Technician






  • 6.  RE: Backcheck Setting

    Member
    Posted 11-01-2022 15:25
    String Height (SH) minus Hammer Center Height (HCH) = Hammer Bore (HB)

    HCH minus 64 mm should equal Wippen Center Height (WCH).

    Many times, I've had to elevate the rear bracket feet 1~2 mm. If you have to elevate the front bracket feet to aid HB=SH-HCH, be aware that the screws (flange and drop) on the hammer rail may not clear under the pin block. Pop cycle sticks available from a hobby/craft store fills the bill most times.

    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
    ------------------------------



  • 7.  RE: Backcheck Setting

    Registered Piano Technician
    Posted 11-01-2022 16:21
    Jonathan,

    Rote learning is defined as the memorization of information based upon repetition. If you only have data as a tool to solve problems, you may find yourself caught in a feedback loop. All the numbers presented to you may not solve your problem if you are dealing with unusual circumstances, and I suspect your problem falls into that category, i.e., new hammers installed on a short piano.

    Understanding the physics and geometry of the action is necessary to solve your problem. Watch the action of the backcheck in relation to the arcing of the hammer tail. If you find that the backcheck "checks" on the upswing while giving you proper checking on the downswing, this suggests the arc of the tail is improper (too great) for a short keystick piano. Remember, backchecks mounted on short keysticks travel at a faster rate toward the arc of the hammer and they will "bump" into each other on the way up.  If you have a large arc on the hammer tail, they will again, "bump" into each other on the way up. You may find yourself trapped into a corner where it would not be so evident on a larger piano with a longer keystick with a larger hammer arc. All the adjustment up or down or bent forward or back may not solve your problem. You must carefully examine the travel of the two action parts while visualizing what a "proper" arc may result.



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    Roger Gable RPT
    Gable Piano
    Everett WA
    (425) 252-5000
    ------------------------------



  • 8.  RE: Backcheck Setting

    Registered Piano Technician
    Posted 11-01-2022 18:53
    Yes I can follow your instruction here.  I need a little time to work through the different scenarios. I feel confident that with so much information I will understand what the piano needs and will get a good result.

    Jonathan Langham, Registered Piano Technician