Randall and all,

I'm delighted you find no problems with the cleaved PG you used,
and I'm hopeful for your continued success.

As long as the variation from one ~ side thickness to the other
isn't too extreme, one won't notice much tilt from the mean horizontal
to where it could physically interfere with the parts used above.

Suspect you already know that very thin PG could be used, and
in a range from say from .02" up to a near maximum of roughly
..04" thickness, but, that may depend on the grade of the
neodymium magnets you use.  Historically, I mainly used N40
grade or above.

Meredith

On Tue, Jul 10, 2012 at 11:49 AM, Randall Peters wrot=
e:

> Thanks for your comments, Bob.  It does my heart good to hear folks
> finally talk about low level latching of mechanical oscillators.  I spent
> the last twenty years****
>
> of my career (finally retiring fully this past spring from Mercer
> University) trying to understand subtleties of friction, especially the
> internal friction type****
>
> that derives from defects in solids.  ****
>
>            One of the first occasions for me to study magnetic levitation
> was about fifty years ago as a freshman physics major at the****
>
> Univ. of Tennessee (in Prof. Oliver Thomson=92s laboratory).  Aware of th=
e
> pioneering work by Prof. Jesse Beams at the Univ. of Virginia, I built an
> electromagnet system with feedback involving output from an optical senso=
r
> --to levitate a steel ball bearing.  I was amazed at the seeming absence =
of
> friction influence on the ball for that system; even though my ball was
> suspended in air.****
>
>           Professor Beams used to spin such a ball in a high vacuum by
> means of an ever increasing frequency of an externally applied, rotating
> magnetic field.   By this means he actually demonstrated a method to tear
> the ball apart.  At some critical point, as the angular frequency was
> increased toward phenomenally high values, the centripetal forces of
> rotation became so large that the steel ruptured.  His method was also us=
ed
> to study diffusion of atoms in a metal, since a very large gradient could
> thus be established.  His experiments were widely acclaimed, and the lab
> named in his honor is worth a visit at****
>
> http://www.virginia.edu/webmap/popPages/76-PhysicsBldg_Jesse.html****
>
> Suffice it to say, Beams could never have become famous for his pioneerin=
g
> solid state physics contributions (ultracentrifuge work) if his magnetic
> fields were exhibiting some kind of friction derived from magnetic
> hysteresis.  Although his permanent magnets were probably an alloy of
> aluminum, nickel and cobalt (called alnico), there is little reason to
> believe that the rare earth types that****
>
> have come along after his work=97should show some bizarre physical proper=
ty
> not possible with alnico. ****
>
>     Now about the matter of the other extreme=97=91low and slow=92 motion=
s.  My
> career has been devoted to the intense study of internal friction in this
> regime.   I=92ve done****
>
> more than most, when it comes to  =91gravitational pendulums=92 outfitted=
 with
> a sensor that allows reasonable quantitative study of low level, long
> period mechanical oscillators.  I jokingly tell folks, it=92s because =93=
when
> one has only a hammer for a tool, everything looks like a nail=94.  ****
>
>      I became interested in the magnetic levitation case for the very
> reason that you claim to be impossible; i.e., that the materials (whether
> PG plate or rare earth****
>
> magnets, or both) must be afflicted with some presently unknown structura=
l
> property that gives rise to latching at low levels of small inertial mass
> oscillators.   ****
>
> I find no evidence from my system to support your claim, based on my
> investigations of the prototype that is described in the article that I
> mentioned to this list serve.  ****
>
> That paper does not show andy figures relevant to the regime being
> discussed, but just today I analyzed a record corresponding to noise in t=
he
> output from the covered instrument while it was =91undisturbed=92.  It is=
 also
> worthy of note that I had made a change to the instrument; i.e., decrease=
d
> the gap spacing between the PG plates and the upper electrode array=97whi=
ch
> increased  the sensitivity by about ten fold.  Whatever the nature of the
> ambient noise during this time, I have good reason (from other studies wi=
th
> my VolksMeter under similar conditions) to believe that those noises are
> extremely small and derive from low level surface motions of the Earth th=
at
> are of common type, for places other than the truly =91quiet=92 places of=
 our
> planet, as  sometimes noted by folks like Dr.  Jon Berger at Scripps Inst=
..,
> UCSD.  ****
>
>      So what was seen?  At times, infinitesimal noise driven motion
> (visible as a fairly sharp spectral line in the FFT ) at the characterist=
ic
> period of the instrument, about 0.6 s.  The quality factor of the
> instrument appears thus to be virtually unaffected by the amplitude of th=
e
> motion; which means there cannot be any latching of the type you
> indicated.  My expectation is that Chris Chapman=92s comment may be
> responsible for what you observed=97i.e., the presence of lint, hairs, or
> dust, interacting as a =91show stopper=92 with your low mass oscillating
> member.  I have seen this also to be true if I wasn=92t careful to elimin=
ate
> such intruders.  The mass of my plates is only about 2 g, and so anything
> of the type Chris mentioned will =91lock it up=92.    ****
>
>        I was also very interested, Meredith, in your comments about the
> importance of shape irregularities in the PG plates.  Indeed, you can see
> from the photographs of my paper that my plates are (as you found) anythi=
ng
> but a smooth planar surface after the cleaving that I did.  But one of th=
e
> greatest features of my capacitive sensors is their relative immunity
> (compared to optical detectors) to such imperfections of construction.
> When I first began years ago to work with crudely built components I was
> astonished at this their property.   So the possibility of this instrumen=
t
> serving as the basis for a useful, new type of seismograph=97looks ever m=
ore
> promising to me. ****
>
>      Randall****
>
> ****
>
Randall and all,

I'm delighted you find no problems =
with the cleaved PG you used,
and I'm hopeful for your contin=
ued success.

As long as the variation from one ~ s=
ide thickness to the other
isn't too=A0extreme, one won't notice much tilt from the mean =
horizontal
to where it could physically interfere with the parts used above. =A0<=
/div>

Suspect you already know that very thin PG could b=
e used, and
in a range from say from .02" up to a near maxim=
um of roughly

.04" thickness, but, that may depend on the grade of the=A0
=
neodymium magnets you use. =A0Historically, I mainly used N40
grade or above.

Meredith=A0


On Tue, Jul 10, 2012 at 11:49 AM, Randall Peters <PETERS_RD@..........<=
/a>> wrote:

Thanks for your comments, Bob.=A0 It doe=
s my heart good to hear folks finally talk about low level latching of mech=
anical oscillators.=A0 I spent the last twenty years

of my career (finally retiring fully this past sprin=
g from Mercer University) trying to understand subtleties of friction, espe=
cially the internal friction type

that derives from defects in solids.=A0 
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0One of the first oc=
casions for me to study magnetic levitation was about fifty years ago as a =
freshman physics major at the
Univ.=
 of Tennessee (in Prof. Oliver Thomson=92s laboratory).=A0 Aware of the pio=
neering work by Prof. Jesse Beams at the Univ. of Virginia, I built an elec=
tromagnet system with feedback involving output from an optical sensor --to=
 levitate a steel ball bearing.=A0 I was amazed at the seeming absence of f=
riction influence on the ball for that system; even though my ball was susp=
ended in air.

=A0=A0=A0=A0=A0=A0=A0=A0=A0 Professor Beams used to =
spin such a ball in a high vacuum by means of an ever increasing frequency =
of an externally applied, rotating magnetic field.=A0 =A0By this means he a=
ctually demonstrated a method to tear the ball apart.=A0 At some critical p=
oint, as the angular frequency was increased toward phenomenally high value=
s, the centripetal forces of rotation became so large that the steel ruptur=
ed.=A0 His method was also used to study diffusion of atoms in a metal, sin=
ce a very large gradient could thus be established.=A0 His experiments were=
 widely acclaimed, and the lab named in his honor is worth a visit at


http://www.virginia.edu/webmap/=
popPages/76-PhysicsBldg_Jesse.html


Suffice it to say, Beams could never have become famous for his pioneering =
solid state physics contributions (ultracentrifuge work) if his magnetic fi=
elds were exhibiting some kind of friction derived from magnetic hysteresis=
..=A0 Although his permanent magnets were probably an alloy of aluminum, nic=
kel and cobalt (called alnico), there is little reason to believe that the =
rare earth types that

have come along after his work=97should show some bi=
zarre physical property not possible with alnico. 
=A0=A0=A0=A0Now about the matter of the other extreme=97=91=
low and slow=92 motions.=A0 My career has been devoted to the intense study=
 of internal friction in this regime.=A0 =A0I=92ve done

more than most, when it comes to =A0=91gravitational=
 pendulums=92 outfitted with a sensor that allows reasonable quantitative s=
tudy of low level, long period mechanical oscillators.=A0 I jokingly tell f=
olks, it=92s because =93when one has only a hammer for a tool, everything l=
ooks like a nail=94.=A0 

=A0=A0=A0=A0=A0I became interested in the magnetic l=
evitation case for the very reason that you claim to be impossible; i.e., t=
hat the materials (whether PG plate or rare earth


magnets, or both) must be afflicted with some presently unknown structural =
property that gives rise to latching at low levels of small inertial mass o=
scillators.=A0 =A0
I find no eviden=
ce from my system to support your claim, based on my investigations of the =
prototype that is described in the article that I mentioned to this list se=
rve.=A0 

That paper does not show andy figures relevant to th=
e regime being discussed, but just today I analyzed a record corresponding =
to noise in the output from the covered instrument while it was =91undistur=
bed=92.=A0 It is also worthy of note that I had made a change to the instru=
ment; i.e., decreased the gap spacing between the PG plates and the upper e=
lectrode array=97which increased=A0 the sensitivity by about ten fold.=A0 W=
hatever the nature of the ambient noise during this time, I have good reaso=
n (from other studies with my VolksMeter under similar conditions) to belie=
ve that those noises are extremely small and derive from low level surface =
motions of the Earth that are of common type, for places other than the tru=
ly =91quiet=92 places of our planet, as =A0sometimes noted by folks like Dr=
.. =A0Jon Berger at Scripps Inst., UCSD.=A0 

=A0=A0=A0=A0=A0So what was seen? =A0At times, infini=
tesimal noise driven motion (visible as a fairly sharp spectral line in the=
 FFT ) at the characteristic period of the instrument, about 0.6 s.=A0 The =
quality factor of the instrument appears thus to be virtually unaffected by=
 the amplitude of the motion; which means there cannot be any latching of t=
he type you indicated.=A0 My expectation is that Chris Chapman=92s comment =
may be responsible for what you observed=97i.e., the presence of lint, hair=
s, or dust, interacting as a =91show stopper=92 with your low mass oscillat=
ing member.=A0 I have seen this also to be true if I wasn=92t careful to el=
iminate such intruders.=A0 The mass of my plates is only about 2 g, and so =
anything of the type Chris mentioned will =91lock it up=92.=A0 =A0=A0


=A0=A0=A0=A0=A0=A0=A0I was also very interested, Mer=
edith, in your comments about the importance of shape irregularities in the=
 PG plates.=A0 Indeed, you can see from the photographs of my paper that my=
 plates are (as you found) anything but a smooth planar surface after the c=
leaving that I did.=A0 But one of the greatest features of my capacitive se=
nsors is their relative immunity (compared to optical detectors) to such im=
perfections of construction.=A0 When I first began years ago to work with c=
rudely built components I was astonished at this their property.=A0=A0 So t=
he possibility of this instrument serving as the basis for a useful, new ty=
pe of seismograph=97looks ever more promising to me. 

=A0=A0=A0=A0=A0Randall=
 <=
/div>