Ok Dave,
Thanks!
Jim
________________________________
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Porritt, David
Sent: Tuesday, September 04, 2007 11:12 AM
To: College and University Technicians
Subject: Re: [CAUT] FW: Scientific study - Stainless wire (Help!)
Jim:
Please don't take this entirely off-list. There are some of us who have
nothing to contribute in that we have no experience with this wire, but
our interest is high and curiosity even higher. The last I knew the PTG
server is capable of quite a bit more traffic before it gets "clogged".
While some seem to have an irritation gene that gets activated by
certain threads, most of us have pretty nimble delete-key-fingers
capable of deftly deleting posts that don't interest us.
dave
_______________________
David M. Porritt, RPT
dporritt at smu.edu
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Jim Busby
Sent: Tuesday, September 04, 2007 11:35 AM
To: College and University Technicians
Subject: [CAUT] FW: Scientific study - Stainless wire (Help!)
List,
No offense is meant to anyone by naming several below as "thinkers".
What I meant to say is that those listed have actively written lengthy
posts of their thoughts on this study. I will move this thread off CAUT
to private posts mostly to them rather than clog the list. Sounds really
bad, the way I worded that. Sorry. (Put foot firmly in mouth...)
Regards,
Jim
________________________________
From: Jim Busby
Sent: Tuesday, September 04, 2007 10:26 AM
To: 'College and University Technicians'
Subject: RE: [CAUT] Scientific study - Stainless wire (Help!)
Thanks, yet again Fred,
Very detailed observations! About thumpers, it seems to me that the real
issue in this study would be;
1. Ability to reproduce the exact stroke w/o variation
2. Elimination of "the human element"
In this regard the Disklavier would be ideal because according to Yamaha
it can reproduce what the human plays to a 100 point scale. IOW if you
hit the velocity at 69 (out of 100 possible), the "machine" will
reproduce it at volume 69 time and time again, as long as the machine
has been calibrated and not changed during the test time. Of course this
precludes human error upon reproduction on that piano.
All the mechanical devices seem moot as to the validity of the testing
as long as it meets the criteria above. Correct?? At least as far as the
testing of wire, sound, and acoustic considerations are concerned. But
hey, you're the braniac here! I'm the farmer who uses bailing wire and
duct tape...
Whatever method these guys use will, of course, be posted so it can be
critiqued. I will pass this along to them. It is still open as to what
they want to test. Hopefully we will have that narrowed down this week
and the testing process can proceed. I'll definitely keep you posted.
You, Jim Ellis, Ric B and Juan seem to be the most active "thinkers" in
our pool of technicians (ON THIS TOPIC!!) and I'm posting privately to
you more than CAUT. Jim is especially active in this study. Ric may
bring a different side to the table with his European influence, and he
seems to like to crunch numbers, and Juan, of course, has already done
a battery of tests.
Regards,
Jim
________________________________
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Fred Sturm
Sent: Tuesday, September 04, 2007 8:16 AM
To: College and University Technicians
Subject: Re: [CAUT] Scientific study - Stainless wire (Help!)
On Aug 28, 2007, at 8:29 PM, Jim Busby wrote:
We did devise a thumper, but I'm wondering is a Disklavier would be the
way to go. Consistency was definitely an issue with our meager spectrum
studies. I'm really hoping that these "science professors" will take the
ball and run with it. That is what they do.
Hi Jim,
Let me give just a few quick thoughts about "thumpers" and
other devises for activating a key, to give your physicists an idea of
some of the problems involved. The tuning test thumper drops a weight
from above the key. There is a free fall of 6 inches or so before the
weight hits the keytop. It has now achieved a certain velocity, and is
still accelerating with gravity (a simple calculation can give the
specifics). So far so good.
Now comes the moment of impact. The key is in a state of
inertia, as is the whole key/action assembly. During impact, there is a
period where the colliding bodies "bounce against each other." The
weight slows suddenly, or possibly stops falling altogether or bounces
upward (we'd need some high speed videography to know for sure what
happens). The keytop absorbs this enormous force, which has impacted it
suddenly.
This scenario is far different in many ways from the way a
pianist plays a key. If he/she plays the key with a great deal of force,
slamming down from above the key (more or less like the falling weight),
the difference is that the mass of the body behind the finger will push
all the way through the keystroke with only a minimal "rebound" effect.
And, as we have seen in various high speed films, the front of the key
will hit bottom before the hammer begins to move (flex and compression
allows this). But this is an unusual piano technique.
Far more common is simple pressing of the key, starting with
the finger contacting the keytop, and accelerating the key. This
technique can be used to create a full range of the available volume of
the piano (not counting percussive sounds from the key crashing into the
keyframe/keybed, in that slamming action described above). And I think
that any study involving tonal output of a piano ought to be based as
nearly as possible on normal key activation. The problem with using a
real live pianist is that you can't be sure of exact repeatability, and
being exact is tremendously important in this area. Joggle a mike, play
a little louder or softer, and the spectrum and even measured pitch will
change.
Askenfeld (did I get that right? the guy in Sweden who put
together the 5 Lectures in PIano Acoustics) said in his lecture that he
used a pendulum to activate a key. This makes some sense, as its
velocity at impact can be controlled by how far it is allowed to swing
(position before letting it go), and bounce is minimized because of the
oblique angle with which it strikes the key. But it is still a rather
artificial setup: a body in motion suddenly impacts the key, and the arc
of movement means that the downward movement of the pendulum weight is
probably decelerating (a pendulum weight moves downward most when it is
at the same level as the pivot point, and it moves downward less and
less as it approaches the bottom. Even though the weight is accelerating
to that point, the geometry is such that its downward motion is becoming
less and less). So I'm not convinced a pendulum is a good substitute for
a finger.
I guess the disklavier/pianodisc/pianomation systems with
their controlled solenoids do a reasonable job. I haven't really fooled
with them enough to have an opinion. It's going to be a sudden
electromagnetic charge of a controlled amplitude creating a an
electromagnetic attraction of a corresponding force. Does this replicate
what a finger does? I think a finger has more possibilities, in terms of
how much acceleration it imparts to the key in any given portion of the
key travel. (I have puzzled a good deal about how it is possible to make
one finger's note stand out when playing a chord. Somehow that hammer
had to be given more velocity. But it all happens so fast, and is so
hidden in psychology, that it is hard to get a handle on it).
Anyway, I will again say that I think a mechanical devise,
with a system of accelerating levers activated by a weight, and with the
mass and placement (leverage advantage) of the weight being variable,
would be a great contribution to study of any number of things to do
with pianos.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu
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