Upright Action Geometry

[Farrell]

Has there been any good treatment of upright action geometry in the Journal
or elsewhere? Anyone have a reference? (I don't seem to have much luck with
my 20-year Journal search engine.) I have so clearly seen what a difference
it can make in grands, but did not think it was such a big deal in
verticals - until yesterday. I tuned a 1908 Shaw upright (monster - 56" -
someone restrung the bass and put all oversized pins in - many are way over
200 inch-pounds torque - I spent two hours tuning that %$#&ing thing -
likely the crappiest tuning I have ever done - my arm is still in ice!).
Someone put new hammers on it recently and replaced about 20 hammer butts.
Obviously the new butts have a different geometry than the original butts.
The old butts provide a strong key response, feel good, and drive the hammer
up to an appropriate let-off point. The replacement butts (with the same
keystroke) only propel the hammer about half-way to the string and then
let-off occurs near the end of the keystroke. The way-too-efficient notes
with the new parts feel like there are little marshmallow on the back end of
the key rather than action parts. WOW! The wrong action geometry affects a
vertical also! I have a couple uprights in my shop that will be getting new
actions, so I need to educate myself. Thanks for any input.

Terry Farrell