---------------------- multipart/alternative attachment When I measured the distance from the key bed (workbench) to the hammer flange center pin and subtracted it from the string height near the hammer strike point, why did it give me a 2" (50.8 mm) difference? This is a different indication of bore distance from when I put a line level on a hammer shank and compared a 50.8mm bore distance to a level on the strings. The 50.8mm bore shows that when the hammer is raised to the string the bubble indicates a slightly undercentering. The old 48 mm bore shows a shank that has almost exactly at the same level (slight rise) as the string. Since the string ht. was measured at a distance about 130mm (length of shank to center of hammer molding) away from the center pin ht. it seems like it should have indicated the same distance as the level/bubble comparison test. ??? Why didn't it? Any ideas? "David M. Porritt" <dm.porritt@verizon.net> wrote: 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. dave *********** REPLY SEPARATOR *********** On 8/20/2003 at 5:31 PM Richard Brekne wrote: 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. Porrittdporritt@mail.smu.eduMeadows School of the ArtsSouthern Methodist UniversityDallas, 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 **************** END MESSAGE FROM Richard Brekne ********************* _____________________________David M. Porrittdporritt@mail.smu.eduMeadows School of the ArtsSouthern Methodist UniversityDallas, TX 75275_____________________________ --------------------------------- Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/5b/3a/9c/eb/attachment.htm ---------------------- multipart/alternative attachment--
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