Variable overpull percentage (was: Finishing where you started)

[Farrell]

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The SAT III has two overpull settings to choose from. 25% for tenor and =
33% for treble. For the bass, if it is say 30 cents flat, I measure =
until it reads 20 cents flat and then calculate the 25% overpull based =
on 20 cents flat. This 2/3 value works real good for me for the bass and =
is easy to do. I'll cut the overpull down a little at about F7 or so, =
and use the 25% overpull so the high treble doesn't get too sharp. On a =
piano that is evenly below pitch, the SAT III gets me easily within a =
cent or two of my target. There are often center strings and unisons =
that I will not even change during the fine tuning.

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com
  ----- Original Message -----=20
  From: DGPEAKE@AOL.COM=20
  To: pianotech@ptg.org=20
  Sent: Friday, December 01, 2000 9:48 PM
  Subject: Re: Variable overpull percentage (was: Finishing where you =
started)


  In a message dated 12/1/00 6:50:36 AM Pacific Standard Time,=20
  michel_lachance@hotmail.com writes:=20




    No offense meant Dave and I thank you for straighten things up. I =
have owed=20
    a SAT II and I know that the overpull percentage is fixed for that =
machine=20
    (20% throughout or so).  If it is different for the SAT III, I beg =
you to=20
    update my knowledtge on that respect.=20

    For example, if both strings each side of the tenor break are 10 =
cents=20
    flat,=20
    RCT will raise the wound string by 12% over target pitch, and the =
lowest=20
    plain wire string by 32% over target pitch, because practice tells =
us that=20
    you need different overpull on those strings for an optimal pitch=20
    correction.  That's why you have to tell RCT where the lowest plain =
wire=20
    note is before you start tuning.  The overpull percentage varies =
throuhout=20
    the keyboard (as well as the pitch offsets...) depending of the =
section of=20
    the piano, according to statistics made on actual experiments on =
pitch=20
    raises.  And you even have the option to change the overpull =
percentage=20
    chart if you find that a particular piano reacts differently to an =
overpull.=20

    So, for the sake of my own education, I would be grateful you tell =
me what=20
    the variable overpull percentages are on a SAT III and how you tell =
the=20
    machine where the lowest plain wire note is.=20

    Regards,=20

    Michel Lachance, RPT=20






  I believe the overpull is 25% of the 2nd partial. Someone please =
correct me=20
  if I am wrong. (Jim, please pitch in). The SAT 3 is the same. I =
usually=20
  measure the lowest note of the plain wire, offset for pitch raise, and =

  re-measure every octave or so.  I have no problems with doing a pitch =
raise=20
  using this method.  =20

  Dave Peake, RPT=20
  Portland Chapter=20
  Oregon City, OR=20
  www.davespianoworks.locality.com=20

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