<HTML> <HEAD> <TITLE>Re: [CAUT] Re: Moving Capstans</TITLE> </HEAD> <BODY> > From: Jon Page <jonpage@comcast.net> > Date: Tue, 26 Oct 2004 12:24:58 -0400 > To: <amccoy@mail.ewu.edu> > Subject: [CAUT] Re: Moving Capstans > > Alan, > With the capstan in its present location, where does the jack end up a= t the > bottom of the keystroke? Good question. The jack is in good position – midway between t= he knuckle and window felt. > > If it is buried into the stop felt there is latitude to move the capst= an > forwards while keeping the dip at > 10mm (hopefully where it is now).   Dip is at about 11mm. Blow about 1 7/8”, and some aftertouch.<= BR> You want the jack to be just in front of > the knuckle at full dip. > Hammer bore is important too, so don't go moving capstans with worn ha= mmers. Brand new hammers. > > With the hammer/key set at half blow *, draw a line perpendicular to t= he > heel through the contact point > (hopefully it's on the Magic Line) and extend onto the key. This is an= > optimal capstan angle.  If the heel is > straight 'perpendicular' is a line which is parallel to the rep suppor= t > post.  Many a time, just by reducing the > acute angle gets the action to regulate properly. > > Prop up a tri-square with a spring clamp, set the half-blow height on = the > square, put a weight on the key. This I can’t quite visua= lize. > > Regards, > > Jon Page > > PS  4.38" is perfect for action spread. > > If this is a B, I'd bet that the balance rail is too far forwards (or = an > M).   It is a 7’ Chickering. Your best bet may be to install a balance rail shim.<= BR> > I did it last month on a B, it was the only thing that would work. It = > changed the KR from .56 to .52, reducing friction and > touchweight. I was called in to evaluate this piano, and noticed as I was tuning = that it played like a Peterbilt. Week later brought my Stanwood stuff. Took = measurements. Began doing “what ifs” in my spreadsheet. All the = numbers pointed to moving the knuckle (kind of a no-brainer to move from 16m= m to 17mm, right?) and also to moving the capstan closer to the balance rail= . Moving the capstan this way brings the action closer to convergence, impro= ves key ratio & WBW, brings down BW and R all of which this action needs= , right? Hence my original “what if” question about how to predi= ct the effect on BW that moving a capstan or knuckle has. The analysis is ve= ry circular. So here is the scenario: What if I move the capstan to achieve a KR of .50? Plug that into the sheet= and I have the new WBW. I know that BW will go down and so will R. But how much?? If I could plug i= n an estimate for how much DW and UW would change , then voila, the sheet ca= lculates R . Then I can play around with SW and FW and plug those back in to= figure out the parameters that this action will allow. Very circular. Thanks a lot for your thoughts. Alan > > </BODY> </HTML>