[pianotech] regulation problem

[David Weiss]

List, 

I am regulating a 1885 Steinway A.  At some point in its recent history the
hammers and shanks were replaced, but it was before the client purchased the
piano. 

As I got into the regulation I found I had to move the let off buttons to
their highest position in order to get the right amount of let off.  The top
of the buttons were almost touching the let off rail.  However, on ten
adjacent notes in the treble this was not true, and I achieved good let off
with the let off button in the middle of its adjustment range.  It took me a
while to figure this out, but I finally realized that although all 88 shanks
were new, those ten that regulated normally had different  shanks with
knuckles 1mm closer to the flange pin.  

Additionally the 10 different shanks give those notes a different action
ratio and a higher downweight.  The action ration on the keys with the 78
matching shanks is 5.4.  On the 10 notes with the closer knuckle, the action
ration is 6.0, and the downweights are about 8 grams higher.

There are two problems I'd like to solve.  First, it bothers me that the let
off buttons are sitting so high on 78 of the notes.  It's not an issue right
now, but could be later on  if anyone ever wants to replace the left-off
buttons with new ones.  Thicker let-off buttons would not regulate.   

The second problem is that on the 10 different shanks I need to reduce the
action ration and downweight to match the other 78.

If I change the 10 odd shanks to match the other 78, I would have consistent
action ratio and downweight, but all let-off buttons would be at the extreme
of their adjustment range.  If I change the 78 shanks to match the odd 10,
the let-off button position would be solved, but the downweight would be too
high.

I would greatly appreciate any solutions, thoughts or advice.

David Weiss