More David's stuff

[Newton Hunt]

I am so gland this topic has raised so much interest.  Obviously
there remains more to be done and new discoveries made on the
road to THE perfect action.

CAUT = _C_ollege _A_nd _U_niversity _T_echnicians.  My file
folder name.

Vince asked "What exactly is 'actions over and under weight'"?

By weighing and charting;
     the strike weights of many hammers,
     the front weight of the keys, and
     the action leverage
a set of practical standards *will* emerge.  There has never been
a set of standards for hammer weights for pianos.  As has been
noted the early 20th century pianos had very light weight and
very efficient hammers.  We no longer have those hammers avail-
able.  What we have are grossly over weight hammers.  But what is
and what isn't over weight?  What is acceptable and what is
practical for hammer weight.  The hammer shank must be incorpo-
rated in these measurements as well as the amount of weights in
the keys.  David has accumulated sufficient data so that an image
emerges.

In the past most factories and technicians weighed keys for up
and down weights with a very nebulous idea that if the key has a
too small up weight there is some friction involved somewhere
(maybe).  The very simple and well know formula (high-weight
minus low-weight)/2 will tell you EXACTLY how much friction is
involved and this can be remedied and MUST be allowed for when
properly weighing out an action.  Balance weighing an action is
the process of adjusting the key weight by removing friction as a
factor.

Friction, with seven major sources, can vary from season to
season and even from day to day.  Normally this is an uncontrol-
lable variance in action performance but with the introduction of
friction control screws at the hammer shank pin then it becomes a
controllable factor.  I can adjust an action friction factor in
about ten minutes.

Strike weight is the weight of the hammer and shank from a
frictionless point directly under the center pin to the strike
point (or heel) of the hammer.

By removing or increasing the weight of each hammer to fit along
a specified line or curve then the mass of the action above the
capstan is controlled.

The point of weighing out the fronts of the keys to match the
weight of the hammers is to control the mass, hence the inertia
of the entire action to a much greater degree.

None of this information is new, what is new is that David has
applied known physics and formulae to common problems of piano
actions.

David has discovered that the mislocation of capstans by a mere
.06" can profoundly effect the mass needed to derive a "common
weighout" of an action.  He has further discovered that the
German actions are almost always right on the mark and American
action capstans can be off by as much as .25".  Some actions have
to have the sharp capstans located on a different line than the
naturals because of improperly derived leverages.

So, by having precise control of;
     Friction, adjustable to the gram at key front,
     Hammer mass, adjusted to .1 gram,
     Key front weight, adjustable to .1 gram,
     Wippen springs to adjust key balance weight, compensate,
           for hammer filing and key back variances in weight,
     Capstan location by a few thou,
     and adherence to designer specs for other action part
          parameters,
a piano action of uncommon refinement is possible.  This is not
to say that this is the all to end all solutions for actions, nor
is it likely to be the ultimate action, nor is it practicable in
all cases.

I find myself becoming more and more uncomfortable in not doing
what I can do to every action, but I am also not willing to
perform all this tedious work on every action.

Now it is a matter of what is possible and what is practical.  I
will do whatever someone is willing to pay me for doing, but in
our positions of being over worked, under appreciated, under paid
and having enough work for double the staff, a limit has to be
drawn somewhere.

My experience has been that when I apply David's knowledge to a
grand piano action everyone likes the results and eventually
begin to demand more piano actions of a similar touch.

David Stanwood has a new e-mail account and will likely be on
line soon to answer questions directly.  I will post his address
as soon as I get it.

Have a nice weekend and then tune, tune, tune, tune for the new
semester.

          Newton
          nhunt@gandalf.rutger.edu