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<DIV>Well, he said the bore would have to be 2-inches (50.8mm). If the
stack were raised 2.8mm, that would allow a 48mm bore. As I mentioned, it
could screw up everything else too, but I thought it worth looking at as a
possibility (I have seen actions screwed up in all kinds of ways). I know
one factory that used to keep several different sized blocks for mounting the
stack depending on the string height. </DIV>
<DIV> </DIV>
<DIV>dave<BR><FONT face=Arial size=2>*********** REPLY SEPARATOR
***********<BR><BR>On 8/20/2003 at 5:31 PM Richard Brekne wrote:</FONT></DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid">Grin...
Ok David P... you got me scratching my head here... How do you come up with a
stack raise of 2.8 mm to achieve 0 rake, 48 mm bore and no overcentering based
on the info Bob sent in ?...
<P>Cheers <BR>RicB
<P>"David M. Porritt" wrote:
<BLOCKQUOTE TYPE="CITE"> What would happen to the "magic line" etc. if
you raised the stack a little? 2.8mm higher stack would get you 0
rake, 48mm bore with no over centering. You'd have to check out all
the other parameters -- let off, etc. but I'd check that. dave
<BR><FONT face=Arial><FONT size=-1>*********** REPLY SEPARATOR
***********</FONT></FONT>
<P><FONT face=Arial><FONT size=-1>On 8/15/2003 at 3:57 PM Bob Hull
wrote:</FONT></FONT>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid">List,I
have a question about appropriate bore distance to see if
overcentering is justified, even designed into the action from the
first. Here's the background for the question(s):In determining the
bore distance for a new set of hammers on a Hamburg D, I have done the
usual math to determine a perfectly level shank when the hammer meets the
string.According to this the new hammers should be bored at 2" for the
treble hammers which is a considerably longer distance than the old
hammers are bored at and also longer than the specs I have from Steinway (
48mm).The old hammers overcenter due to their bore and even more so of
course due to their wear. Was this intended by Hamburg in their
design?After boring at the longer distance I thought would be better than
their old short bore distance, I see that of course I have to lower
the capstan to have a blow distance like the old and of course the let
off. The result is that 1. The shank is only 1/8 or less of the
cushion and 2. The repetition speed is very mediocre. (I can improve
the repetition speed on the long bore distance hammer by decreasing
blow distance to about 1 5/8".)The old hammers repeated very easily and as
fast as you could want. (The old blow distance is about 1
3/4". I searched the archives and read Ron Overs, Richard Davenport,
Newton Hunt and Dave Love about the benefits of a higher shank.
Also, Sam Powell's article in the Sept. '93 Journal about the reduced
friction that comes from the knuckle not being too far below the line.
(Effects of Hammer Bore on Escapement Friction) These seem to give
some approval to overcentering.But, will there be an unacceptable loss of
power? Won't the hammer be sliding into the string rather than
striking it at 90 degrees? If I resort to overcentering like the old
hammers on this piano, would it be advisable to hang them with a positive
rake angle to compensate? Hamburg Steinway specs call for 0
rake. I realize some of this may be a rehash of an old subject, but
any good guidelines would be appreciated.Thanks, Bob Hull
<HR SIZE=1>
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David M. Porritt
dporritt@mail.smu.edu
Meadows School of the Arts
Southern Methodist University
Dallas, TX 75275
_____________________________</PRE></BLOCKQUOTE>
<P>-- <BR>Richard Brekne <BR>RPT, N.P.T.F. <BR>UiB, Bergen, Norway <BR><A
href="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> <BR><A
href="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broadpark.no/~rbrekne/ricmain.html</A>
<BR><A
href="http://www.hf.uib.no/grieg/personer/cv_RB.html">http://www.hf.uib.no/grieg/personer/cv_RB.html</A>
<BR> <FONT size=2 Arial></P></BLOCKQUOTE>**************** END MESSAGE FROM
Richard Brekne *********************</FONT> </BODY></HTML>
<PRE>
_____________________________
David M. Porritt
dporritt@mail.smu.edu
Meadows School of the Arts
Southern Methodist University
Dallas, TX 75275
_____________________________</PRE>