measuring ratios/ popsicle puzzle

[Alan McCoy]

Hey Ed,

For one thing I think I'd use heavier hammers and a flatter (than Stanwood)
SW curve. Your low ratio will certainly support a higher SW. A flatter curve
will even out the sloping BWs. Heavier hammers will give you more power. As
David Love pointed out if raising the stack will get you closer to
convergence while not causing more problems, then it would help with
potential capsizing. How well does it check? Maybe the backchecks need to be
higher anyway? Moving the capstan back would increase the ratio, decrease
dip and increase DW and BW, all in the  direction you want to go especially
for the higher treble.  Is the capstan line straight?

Alan

-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of A440A at aol.com
Sent: Monday, November 27, 2006 5:23 PM
To: pianotech at ptg.org
Subject: Re: measuring ratios/ popsicle puzzle


I wrote: 
      "I am currently preparing to rehammer and reshank a 10 year old D
which has  a very high string height and a very low ratio (4.9). "
 
  >>Dale asks: 
  Before I comment further what's the dip at the pin or  wherever you
measure it. This is very interesting and  peculiar.<< 

     The dip is not consistant,( I ain't gonna regulate it before I do all
the other work),  but averages around .400" with .30" aftertouch.  
 
David writes: 
<< It would be helpful to know the current bore specs, but I would consider

replacing the shanks with either 16 or 16.5mm whichever gives you the proper

ratio for the given SW you intend to use and gets the action to regulate

properly at 10 mm dip and 43 - 45 mm blow.  Then I would check the magic

line to see where the capstan falls with the action regulated with the new

parts.  If raising the stack puts the magic line more on target, I would

raise the stack which will take up some of the gap at the rest cushion.  The

remainder of the gap I would fill by adding felt or installing a thicker

rest cushion.  >>

    Raising the stack leaves the backchecks behind, so I try not to do that
any more than necessary.  Current bore specs?  These are stock Steinway
factory original hammers, I didn't measure them, but did check to see what
was necessary for a 90 degree meeting of hammer to string.  I will need to
bore the bass at 58 mm,  middle sectionat 49, and then 48 mm for notes 54 on
up.  There is just enough room on new Steinway hammers to do this and still
have 26 mm of tail lenght.  
     The 16 mm shanks do not leave enough room for the jack between the
knuckle and backstop felt. I didn't check action spread, but I suspect it is
either correct or slightly wide.  The rest cushions have already had an
additional spacer put in them through the middle section to prevent
repetition failure.  

Alan writes: 
       >>How's the convergence between key and wippen<< 

     didn't measure it

>>What's the key ratio? <<
    didn't measure it,(there will be no time or budget to change it, and I
don't see that I will need to )

>>Are the bore specs (string height minus hammer center height) in the 
>>normal
range?<< 

     Yes

>>What is the knuckle diameter?<<
10 mm

>>On a well-regulated note, how does the jack relate to the knuckle at 
>>full
dip? << 

     It is acceptable, 

>>What is the dip?<<

   see above
 
>>What are the friction numbers?<<

   I don't use them for my action analysis, anymore (unless something is
just too weird).  
 
Regards,
Ed Foote RPT
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html