---------------------- multipart/alternative attachment 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: > 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: > > 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 > ------------------------------------------------------------- > Do you Yahoo!? > Yahoo! SiteBuilder - Free, easy-to-use web site design > software > > _____________________________ > David M. Porritt > dporritt@mail.smu.edu > Meadows School of the Arts > Southern Methodist University > Dallas, TX 75275 > _____________________________ > -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway mailto:rbrekne@broadpark.no http://home.broadpark.no/~rbrekne/ricmain.html http://www.hf.uib.no/grieg/personer/cv_RB.html ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/08/5e/c8/30/attachment.htm ---------------------- multipart/alternative attachment--
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