<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html> 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 ?... Cheers RicB "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 *********** REPLY SEPARATOR *********** On 8/15/2003 at 3:57 PM Bob Hull wrote: <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>Do you Yahoo!? <a href="http://us.rd.yahoo.com/evt=10469/*http://sitebuilder.yahoo.com">Yahoo! SiteBuilder</a> - Free, easy-to-use web site design software</blockquote> <pre>_____________________________ David M. Porritt dporritt@mail.smu.edu Meadows School of the Arts Southern Methodist University Dallas, TX 75275 _____________________________</pre> </blockquote> -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway <A HREF="mailto:rbrekne@broadpark.no">mailto:rbrekne@broadpark.no</A> <A HREF="http://home.broadpark.no/~rbrekne/ricmain.html">http://home.broadpark.no/~rbrekne/ricmain.html</A> <A HREF="http://www.hf.uib.no/grieg/personer/cv_RB.html">http://www.hf.uib.no/grieg/personer/cv_RB.html</A>  </html>