[pianotech] Capstan Line

[Noah Frere]

     First, forgive me if this query is too long and arduous. I should
perhaps just hire an experienced Tech for a couple hours to come and help me
with this, but I'm trying to wade through it alone:

     In checking the Geometry of this 1906 Spector & Sons Baby Grand, my
"magic" line seems to be much "mundane." The line runs maybe 1/8" above the
center of the capstan, rather than through the middle of it; it doesn't even
run through the *center* of the capstan top - but slightly above. It's a
little hard taking this reading however since there's a small wood
stabilizing foot (also the square wippen rail) that gets in the way of my
string, so that I have to hold the string about 7/8" away from the key and
carefully follow the line of the string with my whole head so as to not
distort the view. Does that make sense?

     When I push the keys down 5 mm, the hammer rises average 35 mm. This
gives me an MAR (Mechanical Action Ratio) of 6.75. That is way too high no?
Is 5:1 ratio ideal? Perhaps this high MAR would explain why this piano
"plays like a truck." According to my calculations using John Dorr's Article
in the November 2008 Journal, I would need a 48.4 mm Hammer Blow to make my
8 mm key dip work (I didn't even know anyone made actions with such low
keydips.) However, my hammer blow if I remember is (was, before i messed
around with the Wippen Rail) only 47 mm - and that's with the hammers
resting on the the hammer rest rail flet. (There is room to lower that
Hammer Rest Rail however if I choose to later).

    I have no idea when this was last regulated - maybe decades ago.
    I moved the Wippen Rail forward about 3 mm. From looking at the magic
line again, it looks like if I moved the capstans forward the same amount it
would become less mundane and more magical.

    Now for *My Question*: Should I unscrew all the Capstans, plug the holes
and move them forward?

    Or, is there another way to change the magic line that significantly?

    Also, I'd like to get more into the Stanwood Touchweight, and was about
to start taking measurements but saw that it was a waste of time with the
magic line so out. The only measurements I've taken thus far then are Down
and Up weight, which averaged 61 DW and 23 UP.  I mention this so as to give
more information, but also I guess I have *one more question*: I need new
hammers. These shanks have the sloping knuckle that's built into the shank.
Does it matter much which Centerpin-to-Knuckle Spread I get? In drawing a
line up from the back of the jack, i got an 18 mm and 19 mm spread on the
two I measured. But that's the back of the jack, so that's not the correct
measurement anyway I think. Plus of course that assumes that the piano was
regulated correctly, which it probably isn't. I was thinking of ordering the
17 mm Spread.

    Thanks to anyone willing to help!
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