Lacquer fight! Lacquer fight!

[Bernhard Stopper]

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Dale,
from mechanical view hammer stiffness does not simply follow hooks law. =
Hammer reaction force is increasing nonlinear with felt compression.=20
Hammer stiffness can be described as a complex value by its nonlinear =
elastic modulus. The real part is the reaction force on the string and =
the imaginary part is the damping loss.This phenomen is called =
"hysteretic damping".
Measurements on hammers parameters has been done by Anatoli Stulov, =
where he measured felt stiffness and rebound time.He found differences =
of a factor of about 100 % in the rebound time between different new =
hammer sets made by diverse makers. (Abel, Renner, Imadegawa)=20
The rebound time is in correlation with the felts inner friction losses =
(or imaginary part of elastic modulus) , not to stiffness.
A high quality felt has a low rebound time. Laquering, heat and =
overpressing of the felt increases not only stiffness, but also the =
rebound time (and therefore losses), since the fibres become glued =
togehter.=20

regards,

Bernhard
  ----- Original Message -----=20
  From: Erwinspiano@aol.com=20
  To: pianotech@ptg.org=20
  Sent: Tuesday, May 11, 2004 3:00 AM
  Subject: Re: Lacquer fight! Lacquer fight!


  In a message dated 5/10/2004 1:03:52 PM Pacific Standard Time, =
Richard.Brekne@grieg.uib.no writes:
    Hi Bernhard.

    An interesting point that I see no one has really answered too.

    Cheers
    RicB


    Hi Bernard
    Bernhard Stopper wrote:

    >Hammers parameters are not only stiffness/springieness.
    >A big influence on sound quality is the amount of the energy that =
is lost
    >due to the hammers inner friction of the fibers.
  >>> Which no doubt is in direct correlation with it's inate stiffness =
/sprininess or lack of it.
    A good felt quality has a
    >high ability of rebounding a big amount of the input energy.=20
    Providing it got adequate & appropriate pressing resulting in =
tension & compression.
    It seems logic
    >that this rebounding ability on a high quality hammer is reduced by
    >lacquering.=20
    To me This certainly seems to me to be the misinformation of this =
thread but if you wish.... If so then  a hammer made with a good felt =
but is not stiff enough or to springy for the tone desired then a 5-1 =
lacquer acetone solution ,or whatever, will stiffen the felt & improve =
its rebound rate.
    On the other hand, it might be possible that on a hammer with a
    >bad felt quality with excessive inner friction may be stabilized to =
a better
    >level by lacquering.
  >> May I submit that the  Inner friction of felt  has always been a =
fairly esoteric & small consideration to the discussion of hammers even =
though it is a know factor & frankly to me personally not very useful.
    Rgeards--Dale

    >
    >regards,
    >
    >Bernhard


  Erwins Pianos Restorations=20
  4721 Parker Rd.
  Modesto, Ca 95357
  209-577-8397
  Rebuilt Steinway , Mason &Hamlin Sales
  www.Erwinspiano.com
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