<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:st1="urn:schemas-microsoft-com:office:smarttags" xmlns="http://www.w3.org/TR/REC-html40"> <head> <meta http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <meta name=Generator content="Microsoft Word 11 (filtered medium)"> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="PostalCode"/> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="State"/> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="City"/> <o:SmartTagType namespaceuri="urn:schemas-microsoft-com:office:smarttags" name="place"/>  <style>  </style>  </head> <body bgcolor=white lang=EN-US link=blue vlink=purple> <div class=Section1> >>... I obviously stumbled on a rather large hole in what I thought I had already clear in my mind<o:p></o:p> <o:p> </o:p> Precisely why we don’t have harmonic convergence and world peace. :-)<o:p></o:p> <o:p> </o:p> I really don’t mean to presume to answer the questions you two were raising, only to comment on the transfer of the rotational energy. <o:p></o:p> <div> Dean<o:p></o:p> <u1:PERSONNAME u2:st="on">Dean May</u1:PERSONNAME>             cell 812.239.3359 <o:p></o:p> PianoRebuilders.com   812.235.5272 <o:p></o:p> <u1:PLACE u2:st="on"><u1:CITY u2:st="on"><st1:place w:st="on"><st1:City w:st="on"><u3:place u4:st="on"><u3:City u4:st="on">Terre Haute</st1:City></u3:place></u1:CITY></u3:City> <u1:STATE u2:st="on"><st1:State u5:st="on"><st1:State w:st="on">IN</st1:State></u1:STATE></st1:State>  <u1:POSTALCODE u2:st="on"><st1:PostalCode u6:st="on"><st1:PostalCode w:st="on">47802</st1:PostalCode></u1:POSTALCODE></st1:PostalCode></st1:place></u1:PLACE><o:p></o:p> </div> <o:p> </o:p> <div> <div class=MsoNormal align=center style='text-align:center'> <hr size=2 width="100%" align=center tabindex=-1> </div> From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of Richard Brekne Sent: Saturday, June 21, 2008 12:03 PM To: pianotech@ptg.org Subject: Bechstein B hammer rake / more thoughts<o:p></o:p> </div> <o:p> </o:p> Hi Stéphane / Dean I'm going to drop the horizontal shank bit for a while, because any justification there is for this takes the discussion off in a direction all its own, which for the moment hasnt my attention. Lets just start with this basic formula for bore length thats been tossed around here forever namely String height - Hammershank center pin height. If that formula is valid, then any hammer bored to the resulatant length is going to leave the shank fairly close to horizontal unless the rake of the hammer is quite large.  Do we agree on that much ? Yet the Bechstein I'm doing now has its shanks at the hammer molding about 6 mm higher then horizontal at impact. Ok they are old... but no way can they have lost 6 mm of total length or anything close to it. Lowest bass hammer maybe has lost 1 mm and the highest treble perhaps 2 mm. This ends up just conflicting too much with the bore length formula given. Indeed.. if you stop to think about it for a second,  any requirement for the hammer to be perpendicular to both hammer shank AND string at impact puts the hammershank on the string plane, i.e. significantly higher then String height - Hammershank center pin would yeild. So where does that formula come from and why hasnt this been tossed out before and replaced with something more close to whats needed ? We are using the term rake in the same way so thats not a problem Stéphane. And yes I understand a hammer that is glued perpendicular to the shank and is of appropriate length so that when it touches the string the shank is parallel to the string means the hammer is also perpendicular to the string. Its just that doing this conflicts with the string height formula I've been working with for like ages... and thats whats got me scratching my head. On this Bechstein.. the difference between the two protocols yeilds around a 4 mm difference in bore length as far as I can tell.  Thats a lot I'm sure you'll agree.  Yes ? Keep bouncing thoughts here you two... I obviously stumbled on a rather large hole in what I thought I had already clear in my mind. Cheers RicB <o:p></o:p> <blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'> RicB  wrote : I'm not quite sure how you could use that trick to get an accurate shank parallel to string plane at impact measurement.  At least not one that is any more accurate then the measurement above.  One way or another some small degree of error seems inevitable I suppose. My main querrie is really this shank at horizontal bit. If I drop that requirement, then I'd be able to get the hammer perpendicular to both the string and shank at impact if the action cavity allows for it I susppose... or at least pretty close to it. And that would account for a backwards rake yes?<o:p></o:p> </blockquote> Here I don't understand.  If the hammer core is perpendicular to the string plane and perpendicular to the shank, then the shank is obviously parallel to the string plane, not ?  and per definition, the hammer perpendicular to the shank means that the rake is 90°, not ?  Or do we use different meanings for the word rake ?  I don't call this a backwards rake, but rather improperly no rake.  If the string plane angles up a little, then the shank will be overcentering a little bit, if we agree that overcentering means that the shank will be positively angled with the horizontal plane.  Did I mix up things ? Best regards. Stéphane Collin.<o:p></o:p> </div> </body> </html>