knuckle size

[Vince Mrykalo]

I'd like to be a little more cognitive on the subject of the more
diminutive knuckle.  Most knuckles I've measured on Asian pianos
average .400" in diameter.  Of course some older Baldwins, Knabes, M&Hs,
and Steinways are substantially smaller than this, anywhere from .350"
to .375". I understand that this is in part a function of the distance
between the center of the hammer shank flange pin and the knuckle
center.  The larger that distance, the larger the knuckle should
probably be.  Also, as Michael Wathen says, different sizes of
knuckles affect the length of the lever arm going from the point
where the jack touches the knuckle to the centerpin of the hammer
flange.

However, at least two other considerations pop up.  First and
foremost is the straight line connecting the wip flange centerpin and
the hammer flange centerpin.  At let-off the bottom of the knuckle
should almost be resting above that line, although, for some reason,
the knuckle almost never comes close in real actions, so diminishing
knuckle size would help that situation, but will it make other
relationships go out of whack, or go more out, or get better?

It could bring other relationships more into compliance as well.
For instance, it could bring into compliance(with the other line)the
capstan,wip heel contact point.  One could use, as a measuring stick,
upweight and downweight numbers to see what effects any change would make.

I have found a hypothetical knuckle size change from .400" to .360" to
affect that lever arm length, shortening it by about .030".  But that
change happened to bring more into compliance the wip heel capstan,
and the knuckle closer to the line at let-off. I've always wondered
what other changes occurred besides the ones mentioned, though. Any
further thoughts?

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Vince Mrykalo