Bearing difference on different soundboards

[Isaac OLEG]

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Hello, Dale,

Yes I agree it is not easy to write about these, without sketches.
Sure that I measure how much the board move after un stringing with the same
method as you. That mean I can have things back in place at last.

But I did not thought of using the pre stressing method yet. I just think
about the error made by most while "reading" with a string, and having for
instance 10 mm apparent height below the bridge, when the bridge is slanted
a lot in fact as on Bösendorfers. The first time I've seen that I believed
there was something wrong, and I worked to have the rests higher.

In fact (I believe) the slant on the bridge mean that the thread method is
useless (unless we apply some fixed parameters as on new pianos) because the
back of the bridge is lower, the amount of defluxion should be computed in
regard of the apex of the 2 angles, and it is not possible with a thread, if
you see what I mean.

Talking about Nick articles, I understand that the 0.29 method is useless as
things move under the pressure, but he explain an approach based on the
evaluated crown in regard with rib length , that can with some computation
give the maximum amount of defluxion of a thread without oil canning the
board.
I was just talking about numbers there, a 1/4 " on a thread, when pushed
flat, will lower the bridge a little less, say if the ratio between speaking
length and rear length is 4 for 1, when lowering the string 5 units, only 4
are produced on the bridge, that was the only idea I wanted to express.

I totally agree with the remaining you wrote and I am very interested in the
john Hartmann articles. I will check if by chance I have these issues, but I
doubt of having them all.


Best Regards.



PianoTech
17 rue de Choisy
94400 VITRY sur SEINE
FRANCE
tel : 033 01 47 18 06 98
fax : 033 01 47 18 06 90
cell: 06 60 42 58 77
  -----Message d'origine-----
  De : Erwinspiano@aol.com [mailto:Erwinspiano@aol.com]
  Envoyé : lundi 3 février 2003 05:49
  À : oleg-i@wanadoo.fr
  Objet : Re: Bearing difference on different soundboards


  In a message dated 2/2/2003 3:36:25 PM Pacific Standard Time,
oleg-i@wanadoo.fr writes:


    Subj: RE: Bearing difference on different soundboards
    Date: 2/2/2003 3:36:25 PM Pacific Standard Time
    From: oleg-i@wanadoo.fr
    To: Erwinspiano@aol.com
    Sent from the Internet



    Dale, I remember I've seen one issue of the journal, with this article
on pre stressing the board but I am not sure that I have the whole numbers.

    Can you please tell me what months if you recall ?


    August 1995



    Don't look too far, I have an index on an Excel file, and should find it
there, but remember me the title of the article if you please.


  >>>The effects of Downbearing on tone  by John Hartman



    Do you use dial gauge with magnetic base to see how much distance the
board goes down ? I just bought one of these bases and the simple ones are
cheap, very useful to follow moves against the iron plate for instance.
    But I guess 4 or 5 of them may be necessary (I've heard of a tech that
pre stresses while looking at such a large amount of gauges)


     No dial gauge. A simply way to measure is lay a straight edge across
the top of the rim Use tape to mark it's location and use a measuring device
to measure down to a spot on the bridge before and after stringing. My new
boards usually deflect/go down about 3 to 3.5 mm in the central Part of the
board , about 2 in the first capo and about 1mm in the top. They deflect
about 2mm in the bottom tenor and about 1 in the bass. This is a hard
subject to write about on the computer don't you agree?
      These are concepts so complex and involved  that it took  me some
years  to actually  absorb them to the point that I really understood them.
But NOw I know how to make the practical application in reality.
     Good night--Dale



    Good night , time to go for me ....

    Friendly wishes and for sure I should like to come some day and make you
a visit, thanks for your offer.

    Isaac


    Isaac OLEG

    Entretien et réparation de pianos.

    PianoTech
    17 rue de Choisy
    94400 VITRY sur SEINE
    FRANCE
    tel : 033 01 47 18 06 98
    fax : 033 01 47 18 06 90
    cell: 06 60 42 58 77



      -----Message






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