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<DIV>Hi all,</DIV>
<DIV> </DIV>
<DIV>Interesting question: What happens to hammer felt when it is
doped?</DIV>
<DIV> </DIV>
<DIV>The same question can be asked about open-cell foam =
rubber.
Normally it's nice and squishy (resilient), and although it can impede =
sound
reflection somewhat, it isn't that effective an acoustic material. =
However, the stuff is commercially treated (doped with something, I =
believe) to
make it a bit stiffer and very slightly "crunchy," and that stuff, when =
cut into
wedges or egg crate, has great antireflective properties and can be seen =
lining
the walls of the world's finest recording studios. That's because =
it
absorbs sound energy, rather than reflecting it.</DIV>
<DIV> </DIV>
<DIV>Of course we want to do the opposite with a hammer. We don't =
want the
hammer felt to absorb the mechanical energy, but rather to transfer it =
to the
string. In a perfectly elastic collision, no energy is =
wasted.
Either it goes into the string, or it ends up in the kinetic energy of =
the
hammer as it flies into the rep lever and backcheck. Either =
application of
energy is good. To the extent that the collision is inelastic =
(e.g. when
the hammers are doped and crusty, at least at a microscopic level), some =
of the
energy will go into friction. The remaining energy will be split =
between
the string and the hammer's return. Of course if the hammer were =
doped to
the point of being a wool-reinforced mass of plastic (similar to =
fiberglass), I
suppose it might be pretty elastic, but it would take a LOT of dope to =
start
increasing elasticity, rather than decreasing it.</DIV>
<DIV> </DIV>
<DIV>Here's an interesting experiment, though. I have no idea how =
it would
come out. Most dopes "crust up" the felt, as evidenced by the =
"sugar
coating" y'all talk about. Thus, you have a plastic grit that rubs =
against
the hairs of the wool, increasing friction and decreasing energy =
transfer.
However, if you could find something that sticks to the fibers, doesn't =
flake
off, and doesn't crust up, that could increase the stiffness of the =
felt
without diminishing the resilience. This has been an ongoing =
technical
issue with regard to hairspray products. I don't really know the =
state of
the art in this industry, as I don't use the stuff, but hairspray is a =
lot less
"crusty" than it used to be. In fact I think some of it is =
supposed
to have elastic properties, perhaps providing elastic ties between =
hairs to
stick the hair together, while preserving "bounce." I wonder if =
some brand
of modern hairspray, dissolved in a solvent vehicle and applied in the =
same
manner as your traditional hammer dopes, would improve the performance =
of mooshy
hammers without sacrificing power. Hmmmm..... You guys could =
probably hit the local beauty salon for tech support. LOL!</DIV>
<DIV> </DIV>
<DIV>Peace,</DIV>
<DIV>Sarah</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=spalding48@earthlink.net
href="mailto:spalding48@earthlink.net">Michael Spalding</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
title=pianotech@ptg.org
href="mailto:oleg-i@noos.fr, Pianotech">oleg-i@noos.fr, =
Pianotech</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, April 23, 2004 =
7:56
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: Resilience and =
energy
transfer, was Acetone</DIV>
<DIV><BR></DIV>
<DIV><FONT face="MS Sans Serif">Isaac,</FONT></DIV>
<DIV><FONT face="MS Sans Serif"></FONT> </DIV>
<DIV><FONT face="MS Sans Serif">I'm relying on decades-old memories =
of college
physics for this, so the details may not be exactly right, but I think =
I have
the general principals correct. Resilience is a measure of how =
little
energy is absorbed, and lost to conversion to heat, by a material =
when
compressed: the more resilient the hammer, the less energy it =
absorbs
during collision with the string. As to the other question, how =
much
energy is transferred to the string vs how much is used to propel the =
hammer
into the backcheck, that is influenced by several factors more =
important than
resilience, including the mass and compliance (inverse of stiffness) =
of both
the hammer and the spring. The example of the ball rebounding =
from the
pavement illustrates an extreme, where the ball is light and =
compliant, the
pavement is massive and stiff. Heavy hammers transfer more =
energy to
strings than light hammers.</FONT></DIV>
<DIV><FONT face="MS Sans Serif"></FONT> </DIV>
<DIV><FONT face="MS Sans Serif">hope that helps</FONT></DIV>
<DIV><FONT face="MS Sans Serif"></FONT> </DIV>
<DIV><FONT face="MS Sans Serif">Mike</FONT></DIV>
<DIV> </DIV>
<DIV></DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid">
<DIV style="FONT: 10pt Arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=oleg-i@noos.fr href="mailto:oleg-i@noos.fr">Isaac =
OLEG</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To: </B><A =
title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">Pianotech</A></DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> 4/23/2004 2:46:01 AM =
</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> RE: Acetone</DIV>
<DIV><BR></DIV><FONT size=2>
<DIV><SPAN class=074594208-23042004>So the resilience may be =
adapted in
regards of the hardness, the weight and also the resilience of =
the
object that is contacted , Indeed if the ball rebound, that mean the =
energy
get reflected to the ball. In the hammer we want some to be given to =
the
strings as well is not it ?</SPAN></DIV>
<DIV><SPAN class=074594208-23042004></SPAN> </DIV>
<DIV><SPAN class=074594208-23042004>Best</SPAN></DIV>
<DIV><SPAN class=074594208-23042004></SPAN> </DIV>
<DIV><SPAN class=074594208-23042004>Isaac OLEG</SPAN></DIV>
<DIV><SPAN class=074594208-23042004></SPAN> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT
face=Tahoma>-----Message d'origine-----<BR><B>De :</B>
pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]<B>De la =
part
de</B> Erwinspiano@aol.com<BR><B>Envoyé :</B> vendredi 23 =
avril 2004
00:30<BR><B>À :</B> pianotech@ptg.org<BR><B>Objet :</B> =
Re:
Acetone<BR><BR></FONT></DIV>
<DIV>
<DIV>In a message dated 4/21/2004 10:58:19 PM Pacific Standard Time, =
Richard.Brekne@grieg.uib.no writes:</DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px =
solid"><FONT
face=Arial>btw... Whats Delwins take on hammers and laquer =
? Seem to
remember he <BR>went further then we do over here for the =
natural
hammer resiliancy <BR>side. No... this is one of those =
typical
<<opinions vary>> <BR>questions....and so it should be =
:)<BR><BR>Cheers Dale !<BR><BR>RicB</FONT></BLOCKQUOTE></DIV>
<DIV> Ric</DIV>
<DIV> Right you are.! It all depends on whos defining =
resieliency Know
what I mean. A steel ball is the most reslient when bounced off
cement. It probaly expends the least amount of energy per =
bounce than
the super ball or a felt hammer.</DIV>
<DIV> Cheers back at ya</DIV>
<DIV> =
Dale</DIV></FONT></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>