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MMD > Archives > November 2020 > 2020.11.11 > 05Prev  Next


Force Versus Distance of a Pneumatic
By Jim Miller

Of course, this is with reference to John A. Tuttle's interesting and
timely article 20.11.03. At its end, our ever-dutiful knife-sharp
Editor provided there a handy link leading to all subjects regarding
"Force:"  https://www.mmdigest.com/Archives/KWIC/F/force.html 

From this I read over the ten articles found, and of those determined
that the last proffered by Jeffrey Borinsky (Ref. 1) was the most
actually informative and succinct, and therefor compelling this same
to my non-physicist simple mind.  He writes as a physicist would, as
Jim Welty certainly does too. (Ref. 2)

Also, further, I was pleased that the matter of energy transfer by
means of momentum was left out of his short but sweet offering, just
as it should have, as the mover part has practically nothing to offer
mass-wise, it being of mere second-order effect or less, whereas the
moved contrarily a very large varying amount, as leverage-multiplied
always by a factor of five precisely.

Let's take a look. With a hammer displacement as set to 1.75 inches =
1.875 arc-inches total / (0.4375 inches key touch depth - 0.625 inches
for lost motion = 0.375 inches total displacement) = 5 !

If, say, the lowest 0-A hammer and it's shank weigh one ounce (? worst
case; the highest of 8-c being best), we then find _five ounces_
(nearly one-third of a pound!) of mass swinging on it's lever, this to
be felt at the key or point of input, needing very close, precise
controlling by force-only equipped pneumatics.

"Houston, we have a problem!"

And so it has always been, with precisely zero relief ever to have been
spied in sight.

Now, when things get to moving as single strikes, complexity adds as
energy storage and frictions become additive equation factors.

Then, factor into that at our note 0-A, the "no-touchee" subject of
reflected/stored energy come of previous strikes, which must be
neutralized and/or reflected back before any succeeding strike may
occur, and too with all losses as to precious time involved to be
obviated, this so as to retain the vital fabrics of time and intensity
intact and plus, remembering that the greater the masses involved,
the more time wasted with all that doing, well then ... we're right in
outer space complexity-wise, regarding the assemblage of the actual
real world physics involved.

Aren't we? (Even thinking about it for this writing here, gives me
a headache!)

I well remember that Wayne Stahnke (of Live Performance and much else
presently) was to make one of this prime objectives during the time
of the Second AMICA Convention (1978?), held again at San Francisco,
the interviewing of Dr. Clarence Hickman, then head of research at
Ampico back in the days of the ones later, who was to be attending.
Wayne was successful in this mission, I do believe. (In any of such
as he chooses, he always is and without fail.)

This meant nothing to me then, but certainly would now, as in turn
I myself would discuss with Dr. Hickman, whether or not he had
considered practically back then, what I've just outlined above. Would
he too have held his head as if enduring a pounding headache, when
reconsidering it in toto? Of course, for certain we'll never know,
though, about it we can make good guesses.

Yes, way back then, in those later days of Ampico, resonance and
impedance matching theory were only beginning to make it into science.
Now, both have matured practically, if not fully. This applied mostly
as well back in recent year '78 per se so, by that time, Dr. Hickman
would have become well aware of these surely, and thus doubtless so
would have had things to say, as relating them to my subject of
interest.

There exist no mysteries as to the causes and effects of pneumatics'
behaviors, and how to achieve in-practice different ones. Well, at
least not for myself, do any. The real difficulty lays in knowing what
you want to do ... and why! (In order of drudge quality, that last
coming first and the first last.)

Just what is it that any in-interest desire to achieve or attain here?

Is it perfect equations -- "knowledge certain-and-true" -- so that
pneumatics' characteristics might become then predictable on paper,
and prove so perfectly in practice?

Presuming this as so, then why? As an exercise in discovery solely,
or something more substantive, as in practical application?

Well, for that kind of knowing, for either, better hire a real research
physicist (perhaps Mr. Borinsky or Jim Welty?) to consider the matter
seriously, as apart from anecdotally.

It is my understanding that, in physics classes what are called
"dash pots" are used. These are supposed frictionless pistons for
demonstrations of all sorts of interesting things. I possess a number
of them. These consist of precision made glass tubes about two inches
in length and three-quarters same inside, featuring a piston placed
therein formed of carbon. Their actions' are remarkably smooth, and
promise and do deliver very low leakage.

Yes, a pneumatic could be nominally considered a dash-pot but,
with having a very great difference: it will act in a dependably
non-constant way, regarding it's internal volumetric displacement as
a function over it's possible movement. (Well, we all knew that last
already, didn't we?)

Mightn't dash-pots be used so as to actuate piano actions?

Of course, just as the Pistonola did so long ago for wind-motors, but
here the big problem would devolve to cost. They are expensive, say at
least forty-plus dollars per note for larger useful ones. 88 of them?
Ha! Sell your Violanos!

(The impressive "Metanola" -- a most amusing favorite to famed
rebuilder L. G. Broadmoore of San Fernando -- was certainly a
conceptual as well as executional brilliant stroke, but, alas no cigar
here as I think it was only a container for it's valve, and support for
an ordinary pneumatic. Dang!)

So, if actually finding that magic constant-displacement pneumatic,
to what purpose might it be intended?

As has been written before elsewhere, it might prove as some benefit to
pause at some point and posit the question: 'What is it all about?' --
this search for pneumatic knowledge and, to what larger purpose is it
intended? (If any at all.)

All the foregoing was as according with and to what I've learned over
half a century of observing, considering and building, and thus on that
total account, much of it featuring that quality of "knowledge, certain
and true" with little actual guesswork upon it in-factoring. What
follows now is speculative admittedly, but also as well is rather based
upon those three.

This entire complex subject, of the pneumatic actuation of still
objects having much mass (in the comparison), has yet to be properly
addressed, much less idealized to the point of the perfectly known.

When finally if we do ever address and hit things square on, sans fear
and prejudice and silly want -- resonance theory for pre-established
resonant systems, their frequencies, amplitudes and "Q" factors
(magnifications of resonance 0.7 - 1.0 ideally rather than 0.1 or
worse) -- will as according with and to the sovereign command of
Necessitas, have to become factors in comprehension and design, and
then building but, we're quite a long way away from that Fiat, with our
present discussion here, of simple and basic pneumatic design behavior.

Also as vexingly remaining, is that huge 800-pound gorilla in the room
still. This being the fact that no useful mass (effective) is there
found in any mecha-actuator presently known to man. (Exception: for
that one I built long ago, which an MIT professor came to Tarzana to
examine at lunch once. It was an interesting moment, as well as was the
device.)

Half an ounce total moving cuts no mustard whatever. Actuators are just
not to move that fast so as to. (No mass = no instant movement due to
ideal momentum transfer -- force only, which takes time to "get things
going." The more the mass the more so. Here, the human hand as actuator
and marvelous real-time feedback device, has everything going for it.)

So. What to do here with having arrived at the final Pneumatical Brick
Wall? Very simple: follow the course as set by the successful
electronic reproducers. They know. (Or, do sort of.)

Questions?

(This discussion has the exciting potential to grow very hairy,
very fast -- unlike my lovelier but so-far publicly ignored esoteric
subjects, regarding reproducer pedaling delicacies. To myself, these
are far more interesting ones, and for all the right reasons, so
I believe.)

Jim Miller
Las Vegas, Nevada

Ref. 1: https://www.mmdigest.com/Archives/Digests/199805/1998.05.05.28.html 
Ref. 2: https://www.mmdigest.com/Archives/Digests/200402/2004.02.24.04.html 


(Message sent Tue 10 Nov 2020, 19:28:26 GMT, from time zone GMT-0800.)

Key Words in Subject:  Distance, Force, Pneumatic, Versus

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