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<DIV>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.</DIV>
<DIV> </DIV>
<DIV>dave<BR><FONT face=Arial size=2>*********** REPLY SEPARATOR
***********<BR><BR>On 8/15/2003 at 3:57 PM Bob Hull wrote:</FONT></DIV>
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<DIV>List, </DIV>
<DIV>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): </DIV>
<DIV>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.</DIV>
<DIV>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).</DIV>
<DIV>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?</DIV>
<DIV>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".)</DIV>
<DIV>The old hammers repeated very easily and as fast as you could want.
(The old blow distance is about 1 3/4". </DIV>
<DIV> </DIV>
<DIV>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. </DIV>
<DIV>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?</DIV>
<DIV> </DIV>
<DIV>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.</DIV>
<DIV> </DIV>
<DIV>I realize some of this may be a rehash of an old subject, but any good
guidelines would be appreciated. </DIV>
<DIV>Thanks,</DIV>
<DIV> </DIV>
<DIV>Bob Hull</DIV>
<DIV> </DIV>
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<PRE>
_____________________________
David M. Porritt
dporritt@mail.smu.edu
Meadows School of the Arts
Southern Methodist University
Dallas, TX 75275
_____________________________</PRE>