<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=Content-Type content="text/html; =
charset=iso-8859-1">
<META content="MSHTML 5.50.4522.1800" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT size=2>Roger/Newton:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>In this case it is new parts. Renner wippens, =
Abel
shanks. Center pins are fine everything is lubricated properly and =
adequately. I am aware of the static friction element but it seems =
more
than that. I do notice that the leather on the Abel shanks =
is much
different than the leather on Renner shanks, which I have generally used =
in the
past. The Abel knuckles seem not as smooth and soft as =
Renner's. Any
comments on that? </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>David Love</FONT></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=baldyam@sk.sympatico.ca =
href="mailto:baldyam@sk.sympatico.ca">jolly
roger</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> August 24, 2001 10:13 =
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: hammer =
acceleration</DIV>
<DIV><BR></DIV>Hi
=
David,<BR> &nb=
sp;
Are you noticing this on new parts? Once static friction is =
broken, I
have noted that this happens more frequently with worn or loose =
keybushings.
e.g. Changing a prehung set of Yamaha shanks, with out rebushing =
keys.
At one time I used to change just the hammer sets at the =
University. Now
I insist on rebushing keys along with hammer replacement. It =
makes a big
difference.<BR>If the friction is high on the knuckle and centre =
pinning
friction is very low it can give similar results. To trouble =
shoot.
Remove a hammer and wippen assembly, and measure the friction of =
the
flange C/P's, Holding the flange horizontal, if it drops under it's =
own
weight, will give you a quick check, but start measuring and repinning =
if
there seems to be problems. This eliminates these as the cause. Next =
examine
the capstan, and wippen cloth, polish the capstan, and if it's =
old
capstans steam out the cup, dry iron smooth, and burnish in some =
teflon
powder.<BR>FWIW. I have repinned more than one set of flanges on new
parts. <BR>With friction happening with the right amounts in the =
right
places, the key should go down nice and and steady. Many new Korean =
pianos
have way too much friction on the knuckles, shrinking the C/P bushings =
has
been a common practice to over come friction. It will mask the
problem, and give acceptable DW readings. Change the knuckles, =
and WOW,
watch the the friction figures change.<BR>To to look at geometry =
issues you
have to start with the magic line, key ratio, etc.<BR>The old adage, =
"divide
and conquer", applies here. Just eliminate one thing at a time.
<BR>Regards Roger<BR><BR><BR><BR><BR>At 09:00 AM 8/24/01 -0700, you =
wrote:
<BR><FONT size=2>
<BLOCKQUOTE cite type="cite">I notice, when I am doing a weigh-off =
on a key
board, that on some actions as the hammer rises the acceleration is
relatively slow and steady. Other times, once the hammer =
starts to
rise, the acceleration is quite rapid. What is =
responsible for
that difference? Friction would seem to be the logical answer, =
but
friction where? I heavily lubricate actions before I do a
weigh-off. There seems to be something else at work in the
geometry/leverage. Among other things, with the rapidly =
accelerating
hammer, it is more difficult to determine the measured =
downweight. I
there any way around that problem? </FONT><BR><FONT
size=3><BR></FONT><FONT size=2>David
Love</FONT><BR></BLOCKQUOTE><BR><BR></BLOCKQUOTE></BODY></HTML>