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

[John Hartman]

David C. Stanwood wrote:

> 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
> 

Good point, well said David and I see your 
reasoning. Nice j-peg as well.

> 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


David,

I am sure you know that the center of your rods 
(or the center of any lead pattern) would not be 
the proper measuring point for measuring the 
moment of inertia. While you can use the center of 
gravity in static measurements it is not so simple 
for dynamic measurements. I concede that the way 
you have addressed the inertia problem is probable 
accurate enough it is not as rigorous as you 
method for static balancing. I am not one to do 
much hair splitting (that's how I keep a full head 
of hair) I have to say that your balance system 
does split hairs relatively speaking. So why not 
get just as .. err.. precise when working on the 
inertia of the action?

You have made some good points but still there 
remains the question: How can we measure directly 
the inertia of the action or the inertia of any 
action part? Just as you have come up with 
solutions to measuring the static balance of an 
action I would like to see some way to measure the 
dynamic properties of the action. Until we have a 
way to do this we will not know if there is a 
benefit to calibrating the inertia of the action. 
Or how important calibrating the inertia of the 
action is compared to calibrating its static balance.

BTU I really like your round slide rule for 
calculating balance components. It is smart as 
well as beautifully designed. Good work!

John Hartman RPT

John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
Rebuilding Steinway and Mason & Hamlin
Grand Pianos Since 1979

Piano Technicians Journal
Journal Illustrator/Contributing Editor
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