Even balance weight or even something else, that's the question.

[David C. Stanwood]

>David Love wrote:
>> 
>> Why do we assume that even balance weight should be the standard which
>> translates to a lighter feel at the upper end of the piano than at the
>> lower end.  Anybody experimenting or setting up pianos with a graduated and
>> increasing balance weight or, better yet, with uniform inertia?
>> 
>> David Love
>> davidlovepianos@earthlink.net

>John Hartman Wrote:

>David,

>As far as I know no one has created the tools or methods to calibrate an 
>even gradation of inertia in an action. I think it would be difficult to 
>use key leads to balance the action statically and dynamically at the 
>same time.
>
>Please refer to the illustration I have posted on my web site. If you go 
>to the information page there is now a link to a page I have created for 
>materials of interest to technicians. I have posted a drawing of how to 
>measure the moment of force and the moment of inertia.
>
>The greatest variation in inertia is found in the keys due to variations 
>in the leading pattern. I suppose keeping the leading pattern as even as 
>possible would provide a rough calibration of key inertia.
>
>BTW both of these keys could have the same moment of force but the lower 
>key would have a lower moment of inertia.
>
>John Hartman RPT
>
>John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]

Dear David and John,

I'll pitch in my boiled down take on this subject:

For years my study group used smooth Balance Weights instead off smooth
Down Weights when weighing off and we noticed that it made the pianos feel
more dynamically uniform.  Using the BW method eliminates friction errors
in the lead pattern.  This is the  major drawback to the Down Weight system
without a friction check.  

When I started tipping keys onto digital scales and studying the results we
found that front weight patterns turned out to be smoother by using BW
instead of Down weight but they were still irregular.  The Front Weight
smoothness was made even smoother when hammer weights were adjusted prior
to weight off by to make Strike Weight to a smooth curve.  I mean a major
improvement.  

We found that even when Strike Weights are smoothed and the keys balanced
to a smooth Balance Weight, there are still significant note to note
variations in the front weights.   These inconsistencies were eliminated
with Equation Balancing using calculated Front Weight curves (US Pat
7877872).  This results in Front Weights that fit a smooth curve and
pianists report that the pianos feel even better.  

I'm aware that the Pattern itself is important.  Consider a case when two
keys have the same front weight, one with one lead out to the front and
another with say four leads in close to the balance rail.  The key with one
lead way out takes more force to accelerate to the same velocity as the one
with four leads in close to the rail.  At Reno I showed the pendulum rates
of two balsa wood beams, both with the same front weight and lead pattern
as above mentioned.  The pendulum rate of the beam with four leads was
twice as fast as the beam with the single lead.  So it does make a
difference how the leads are patterned in the keys.  

John says:

>I think it would be difficult to use key leads to balance the action
statically and dynamically at the 
>same time.

The solution that we use with Precision TouchDesign installations is to use
smooth front weights and center symmetrical key lead patterns around a
point half way in between the front of the key and the balance rail.  We
keep the patterns as tightly spaced as possible. The patterns are always
close to center line of the front half of the key.  We find that this
addresses the dynamic quality sufficiently enough using practical static
weight methods...  

Here is a picture of a "Tower Pattern" as we call it:

http://www.stanwoodpiano.com/Pa100088web.jpg

I can hear some saying to themselves "that looks like a lot of lead".  The
example given is a Kawaii with a 5.3 strike weight ratio and 1/4 high zone
hammer weights with 44.5mm blow and 10mm dip.  The Front Weights are under
my published "ceiling".  We know from experience that such setups play,
feel, and sound great...

Theoretically I can imagine that the most ideal and dynamically smooth
displacement of weight added to the key for weighing off would be to use
bars of metal, attached to the bottom of the keys, of varied lengths as
needed to balance the key with their center point on the center point of
the key but what's the point of hair splitting?  It's a good and necessary
mental exercise that's what... but impractical and unnecessary in the real
world.

Thanks for the formula's John.

David Stanwood


P.S.- David... I don't understand the part of your question: "Why do we
assume that even balance weight should be the standard which translates to
a lighter feel at the upper end of the piano than at the lower end?"