measuring ratios/ popsicle puzzle

[David Love]

If you are committed to the 17 mm knuckle because of spacing and the ratio
is too low, you will have to move the capstan back to achieve the overall
ratio you want.  

(You can, btw, raise the backchecks fairly easily.  Just pry them up a bit.
I have done it frequently on Steinways even when the stack is not raised
when a too low setting makes it difficult to get the hammers to check high
enough.)

David Love
davidlovepianos at comcast.net 
www.davidlovepianos.com

-----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