What is Inertia

[Ed Sutton]

Richard-

My dictionary agrees with Don.

But what we are trying to do here (I think?), is try to make piano actions better
for the pianists.
Since there are so many kinds of pianists, there might be many ways to make pianos
better, of more adapted to various players and ways of playing.

And in particular, we were concerned with the placement of key leads.  For a long
time many of us have followed the rule of thumb that it was better to produce a
given front weight by placing a large quantity of lead close to the balance rail
than by placing a smaller quantity close to the front, that this makes the action
"feel better" and repeat faster, at least in the bass octaves.

If this is true, then it is worth going to a lot of trouble to do it, if not, it
is a waste of time.

Jim's experiment to measure jack reset time should answer the question on
repetition.

I can imagine some simple experiments to determine if performers can feel the
difference between keys with the two different configurations.  It will require
building an action model with about ten keys, so I'm not willing to commit just
yet to do it.  Anybody got some grant money?  I first thought of using an old
action I have, but realized the keys are too short.

If we could answer yes or no to either of these questions, it would be valuable
information.

Notice I've written all this without using the "I." word!

Just for fun, take a look at the pictures facing page 298 in Ortmann's
_Physiological Mechanics of Piano Technique_ (comparison photos of 5 different
arms).  He found that adult pianists' forearms weighed between 6 and 14 pounds.
And we wonder why, no matter how hard we work, we can't get the universal perfect
action.....

Happy holidays to everyone.  I'm very grateful for this list.

Ed Sutton

----- Original Message -----
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: "College and University Technicians" <caut@ptg.org>; "Newtonburg"
<pianotech@ptg.org>
Sent: Wednesday, December 24, 2003 6:22 AM
Subject: Re: What is Inertia


>
>
> "Don A. Gilmore" wrote:
> >
> > There are no units of "inertia"; one  object cannot have more "inertia" than
another.  It can have more kinetic
> > energy, or momentum, or mass, or velocity, or indeed "moment" of inertia
> > than another object since those are measurable, quantifiable properties.
>
>
> I understand exactly what you are saying, as I understand exactly what
> the others are saying. But I have to point out (without taking a
> position on the matter myself) that there are three declared definitions
> for inertia on pianotech by various folks with some degree of physicis
> knowledge. Let me list them.
>
>
> 1. Don Gilmore... inertia is a concept, not a quantity, has nothing to
> do with size, mass, velocity or anything else. Is simply the fact that
> objects with mass tend to resist any change in velocity. No object
> regardless of mass has any more inertia then any other mass.
>
> 2. Sarah and Mark.... inertia is very much like Don describes, yet
> inertia is mass related... a larger mass will definatly have more
> inertia then a smaller mass.
>
> 3. Jim Ellis.  inertia is clearly mass related its very hard to read his
> definition without concluding he means that inertia is related to
> acceleration and /or velocity... That  relation to acceleration seems a
> bit unclear... but as I read through his posts I get that he first
> said... Inertia = mass x velocity-squared, then after some debate
> changed this to Inertia = mass x acceleration-squared. His last post
> seemed to draw this up a bit differently
>
> "Inertia is a minifestation, a property, an effect, of acceleration and
> deceleration.  It's proportional to the square of the change in speed,
> or velocity."
>
> What I'd like to see at this point is that since Don, Sarah, Mark, and
> Jim all are people we all rely on for physics insights, and because they
> all present clearly different definitions of this concept,,, that these
> four all bang this one through until they arrive at a common definiton
> for us.
>
>
> grin.... NOW I will state my own position... tentatively...ok ?? :)
> Seems to me that Don is correct... except I have a hard time
> understanding or accepting that "one  object cannot have more "inertia"
> than another". If this is true then either inertia is a constant, or
> inertia is just plain undefined... as in divideing by zero more or less.
> So I lean towards Sarah and Mark. But I want to see you 4 hashing this
> out so we can past the problem.... as clearly any discussion about
> action mechanics on this list is going to be rather meaningless unless
> we can agree on what terms like inertia mean.
>
> Cheers
> RicB
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