Moment of Inertia of grand action parts.

[Richard Brekne]

John

Another nice post from one who probably will be amoung those who will
lead us beyond where Stanwood left us er.. balanced as it were. A couple
comments below.

John Hartman wrote:
> 
> 
> Several people have complained that this material has just brought more
> confusion to our understanding of the grand action. That's
> understandable since the study of the dynamic action is at least ten
> time more involved that studying the static action. It took many years
> for the simple static principles Stanwood has developed to be accepted
> and understood. I would expect these dynamic principles to take a lot
> longer. The task is especially daunting since getting a mental grasp of
> how it works requires familiarity with math and physics. I expect that
> most piano technician's would need to bone up on high school level
> algebra and physics to gain access to this knowledge.

One of the things we are going to end up needing is a very clear and
simple way of measuring action MOI, comparing to a reference base ala
Stanwoods Smart Chart... or something in the same spirit, and choose
what hammer weights, ratio, and key leading will give us the particular
performance characteristics we are after at any given time. This is one
of the huge plusses with Stanwoods system, as far as that goes. It is
very easy to understand, very easy to implement, and accomplishes
exactly what it sets out to do, and not really a lot more. And, as with
his system, you can sit down as I and a few others have, and figure out
exactly what his formula is and how he arrived at it, or you can simply
follow Stanwoods  <<yellow brick road>> as it were and pay for
consultant services.  Either way, any system for balancing the action
will have to be just as easy to implement. 


> One of the things learned from studying MOI is just what Balance weight
> does. It determines (along with friction and let off resistants) the
> minimum force to move the action. The total force after that is
> determined by the force required to accelerated the action minus the
> force of the BW. At very soft levels of playing the BW will be a
> significant part of the total force while at forceful levels the balance
> weight is insignificant. Through the dynamic range of playing the force
> needed to accelerate the action increases while force to overcome the BW
> stays the same.

An interesting comment and perspective on Balance Weight, and what
follows. I havent had time to really look at your last diagrams, and
posts which address a few of the questions I had about how leverage
works into this equation, but I will get to it. Thanks again for your
many thoughts and perspectives John.
> 
> 
> John Hartman RPT
> 
Cheers
RicB