David's Stuff

[Newton Hunt]

Hi, All,
    I was asked if I had any of David Stanwood's recent hammer
weight data.  Unfortunately I do not but he has developed some
reliable figures empirically, by measuring many piano's hammers
and deriving standards by determining the actions over or under
weight.
    In David's scheme he will weigh and adjust the weight of each
individual hammer.  By weighing the weight from the center pin to
the strike point he gets the strike weight.  I have some .250"
solder I use for letting into the moldings.  Sanding for going
the other way.  Taking more than a gram of weight off a hammer is
a real challenge.
    I lift the flange so it is 90 degrees to the shank and rest
the flange pin end on a half round hammer shank taped to the
damper height gauge found on the string height gauge located on
page 14 of APSCo's new catalog.  The height adjusts so the shank
is horizontal.
    I then rest the hammer heel on an Auhous model C-305 digital
scale from Metric People 800-426-8356 $125 (use David's name for
the discount).  The scale's range is 0.0 to 300.0 grams or about
10.8 ounces.
    By graphing these "Strike Weights" you can see the useful-
ness of knowing what the weights are.
    The keys are weighed from the center of the balance pin hole
to 1 cm from the front end of the keys.  I have made little
fixtures the keys rest  upon to make this chore go faster.
    By measuring the up weight and the down weight you can
calculate the "Balance Weight" of the action.  A 50 gram down and
a 25 gm up will have a balance weight of 37 grams.  A nice
slightly over weight.
    Additionally (50 gm minus 25 gm)/2 will partially reflect
efficiency and/or friction of the action of 12 grams which is
nice and average.
    These numbers help you find over and under friction points of
the action.  More about this later.
    The Europeans have, for over a century, used wippen helper
springs mounted at the wippen flange.  These springs serve to
lower balance weight significantly and to reduce the amount of
lead needed at the fronts of the keys.  Most American technicians
have little understanding of these springs and what they can do
for the pianists.  David has developed techniques for adding
springs to any current action so that the touch weight of the
action can be controlled by adjusting the tension of the spring.
    David has introduced friction control screws into the hammer
shanks so that a sliver of wood at the bottom of the hole bears
on the felt bushings.  Introducing one point of friction control
makes it possible to control the friction of the entire action.
This friction can be adjusted in about five minutes when the need
arises.
    If you send the balance weight, front weight and strike
weight of all C notes and C# notes to David he will return a set
of weight specs for the strike weights and the front weights
specific to that action based on your requested balance weights.
    This will control the inertia of each hammer and each key so
that the action feels incredibly smooth.
    This leaves one other uncontrolled factor, geometry.
    By putting weights on a key with the hammer off the wippen so
that the key is absolutely perfectly balanced then lowering the
hammer and taking the up and down weights one can measure the
leverage of the entire key unit at that note. David may relocate
the capstans to bring an action into compliance.
    David has just promised to send me a text file to be posted
here in the near future providing much more specific information.
He can also be reached at 508-693-1583 if you need more informa-
tion now.
    David uses a set of gram weights that range from 15 to 65
grams.  These come in a box with trays to arrange them for what
different balance weight setups.
    I do need to point out that David sells information and
provides the services of friction screws, spring installation if
you send him the action parts.  He will initially adjust the
spring tension so you will have little of that to do at comple-
tion.
    Well, I think I have covered most inquiries in too much
detail.  If there are further questions just post them along.
    My experience has been that the more extensively detailed
actions become the favorite of the students and faculty to the
point that they are now demanding better pianos to practice,
teach and perform upon.  It takes an ungodly amount of time to do
all this work.  David has workstations for each operation that
makes it go FAST whereas I am using a Crapsman drill press which
has to be jigged up every time.  A royal pain.
    I did a complete modification (except capstan relocation) on
an out of the way practice room Kawai KG-2C and without advising
anyone (except one professor and Robert Toub) I have found that
it is ALWAYS in use.  The kids know nothing about it except that
they like it.
    If I have the time I would like to do every piano and sit
back and bask in the glory and accolades.  As it is I get too
many complaints that the pianos are not good enough.  You can
never win :*(.
    I think the idea of using the CAUT meeting in Alburquerque on
this extremely timely and useful information a good idea. Thanks
for suggesting it!!!  There is more and other information out
there than just Davids and I am most interested in learning how
to make actions as good as I can.

         Newton J. Hunt
         nhunt@gandalf.rutgers.edu