Hi Chris,

Thanks for all the notes, I'am planning on trying most if not all in time.

I did whip up 3 strapping steel units of a thickness of 0.022" and put them
on the magnets, with plastic spacers, but without any beveled inside edges.
I am seeing a levitation height of ~ 0.020"; which appears to be ~ 0.005"
of a inch less than without any steel whatsoever on top.

Out of curiosity, I removed the center iron strip.  Now, the levitation
height
is about 0.025" above the 2 outside steel strips.  This also means (for what
its
worth); that its levitation height above the center magnet to the bottom of
the PG
is a interesting ~.047"....which is almost twice the average levitation
height with
no steel at all.  In a terminology way; its kind of a "U" channel setup in
this
configuration.  Of course, adding weight to the PG, is still limited to less
than 0.025".
Totally unexpected but a interesting and possibly useful result...which
opens up
yet more thought/s of additional changes.

The harmonic oscillation motion does appears to be much more symetrical;
than I think I've seen it before....so, it appears the iron is doing some
good.

I'd think that some "weight load" tests might be appropriate for both
variations.

Take care, Meredith


On Dec 7, 2007 5:07 PM,  wrote:

>  In a message dated 07/12/2007, paleoartifact@......... writes:
>
> The "sticky" terminology in particular is that yes; it is normally a very
> real problem.  It "seems", to be most visually prevalent when only a single
> piece of pyrolytic graphite is used.  By "sticky" I mean it seems to
> sometimes be anchored in one or more spots and even with some light induced
> tilt where one would surely expect a movement response; they occasionally do
> not get any.  Of course, I'am not referring to debris (small hair, etc.)
> that may actually be the cause sometimes.  With PG, its possible to impart
> small magnetic particles thereon which will react in the magnetic fields of
> course.
>
> Hi Meredith,
>
>     I suspect that this is due to slightly differing field strengths along
> the magnets. It is very troublesome when you are using several magnets
> joined in line.
>
> Actually the ONLY reason, I'am trying again is that with two separated but
> interconnected pieces of
> PG, I know I'am seeing quite a improvement in overall response.  I can't
> really presently describe the "why"; except perhaps the joint sum of the two
> pieces are kind of like a differential diamagnetic
> response....
>
>     The sum of two pieces should help smooth out local magnetic
> fluctuations.
>
>  I've also looked at totally switching out the PG, with other different
> pieces, and the results
> look the same; so its obviously not just specific to acouple PG pieces.
> Also, the PG pieces have
> been on and off the magnets numerious time for various test trials; so the
> results are real.  The PG
> pieces are also fairly close to each other in dimensions; which might be
> necessary (?).  The PG
> pieces I have are not precision machined so they vary in flatness and in
> other dimensions by around
> ~ 0.010".
>
>     You might try using emery paper on a flat surface to give a flat under
> surface to the PG pieces?
>
> Another feature I like is the variable period with the variable PG
> spacing.  How I'am going to do that
> with flimsy aluminum is yet to be attempted.  One may have to settle for
> whatever period they select before any "glueing" down of the aluminum.  Even
> being able to do so, is unique.
>
>     Can you buy some copper foil from K&S Metals and use that? They stock
> 3 and 5 thou sheet. The Aluminum usually supplied is a Si alloy, not
> pure and it is paramagnetic. Copper is diamagnetic but far weaker. I ran up
> against these differences / problems when using NdFeB quad magnets for
> damping the Lehman.
>
> I've even put a large optical magnifying lens next to the model; to check
> for minute lockups, and
> of course whether it physically oscillates around a reference "zero" mark
> I put on the magnet.  I can't say I've definitely seen any sticking yet on
> this model; but if it happens, I will.
>
>     If you use a small lens to give a ~parallel light beam from a small
> bulb at rignt angles to the slip direction, small side movements probably
> won't be too obvious.
>
> One good indication that it works better is that I do see increased wider
> span tilt oscillation motion
> effects with the 2 PG pieces than I've ever seen with one piece of PG.  It
> seems to be ~ 3X over
> that of just using 1 piece of PG.
>
> I don't yet really know the result of adding on steel/iron atop the
> magnets; as I've not yet done so.
> I think I'll try 1/2" width X 1/8" thick iron initially.  The iron is
> commercially common size stuff, but
> it does have dual rounded outer width edges; which might not be totally
> ideal.  The size is common;
> but its different, as it was used as a desk drawer guide and was coated
> with a thin layer of copper
> and then chrome plated.  Its probably (?) bright steel and not the black
> structural variety.
>
> I've seen thin ~ 1/16" thick iron/steel work very well on kind of a "U"
> channel type setup...where the
> (then) spectrographite rod levitated lower down on the deliberately lower
> middle channel magnet.
> That was Chris's recommendation and it did dramatically improve its
> levitation height.
>
>     I bought some 1/32" galvanised steel sheet, which seemed to work quite
> well. I suspect that 1/8" will be much too thick and it will allow the field
> to be linked sideways, instead of looped over the top of the magnets and
> going through the graphite. Iron will carry about twice the field that the
> magnet can supply. You might consider filing the edges of the strips at 45
> degrees, rather than leaving it at a right angle?
>
> Yes; the aluminum paramagnetism has been seen in the past also; and
> its going to show up here
> also.  The aluminum could be responsible for some of the sticking, with
> their various impurities.
> I am using K&S Engineering aluminum; which seems to be purer stuff.  With
> the severe weight
> limitations; its hard to consider using other metal/s.  I suppose I can
> hang up a piece of the stuff
> on a long thread, and bring a magnet near it; to just see a rough
> indication of its general paramagnetism.
>
>     K&S supply mostly 6061 Al alloy
>     See www.ksmetals.com and http://en.wikipedia.org/wiki/6061_aluminum
>
> I am also presently using 2 plastic spacers in between the magnets; which
> are 0.035" thick X ~0.475" in width.  The spacer is a idea from John Lahr;
> and it does help a little for some slightly increased levitation.  I may try
> to find some thin plastic or non-ferrious metal that is 5/8" in width and
> somewhere around 0.020 to 0.0315" thick, that could aid in setting up the
> iron on the magnet tops.  The iron will be magnetically normally forced
> against the joints for alignment.
>
>     Regards,
>
>     Chris Chapman
>
Hi Chris,
 
Thanks for all the notes, I'am planning on trying most if not all in time.
 
I did whip up 3 strapping steel units of a thickness of 0.022" and put them
on the magnets, with plastic spacers, but without any beveled inside edges.
I am seeing a levitation height of ~ 0.020"; which appears to be ~ 0.005"
of a inch less than without any steel whatsoever on top.
 
Out of curiosity, I removed the center iron strip.  Now, the levitation height
is about 0.025" above the 2 outside steel strips.  This also means (for what its
worth); that its levitation height above the center magnet to the bottom of the PG
is a interesting ~.047"....which is almost twice the average levitation height with
no steel at all.  In a terminology way; its kind of a "U" channel setup in this
configuration.  Of course, adding weight to the PG, is still limited to less than 0.025".  
Totally unexpected but a interesting and possibly useful result...which opens up
yet more thought/s of additional changes.  
 
The harmonic oscillation motion does appears to be much more symetrical;
than I think I've seen it before....so, it appears the iron is doing some good.
 
I'd think that some "weight load" tests might be appropriate for both variations.
 
Take care, Meredith

 
On Dec 7, 2007 5:07 PM, <ChrisAtUpw@.......> wrote:




In a message dated 07/12/2007, paleoartifact@......... writes:

The "sticky" terminology in particular is that yes; it is normally a very real problem.  It "seems", to be most visually prevalent when only a single piece of pyrolytic graphite is used.  By "sticky" I mean it seems to sometimes be anchored in one or more spots and even with some light induced tilt where one would surely expect a movement response; they occasionally do not get any.  Of course, I'am not referring to debris (small hair, etc.) that may actually be the cause sometimes.  With PG, its possible to impart small magnetic particles thereon which will react in the magnetic fields of course.

Hi Meredith,
 
    I suspect that this is due to slightly differing field strengths along the magnets. It is very troublesome when you are using several magnets joined in line.


Actually the ONLY reason, I'am trying again is that with two separated but interconnected pieces of
PG, I know I'am seeing quite a improvement in overall response.  I can't really presently describe the "why"; except perhaps the joint sum of the two pieces are kind of like a differential diamagnetic

response....
    The sum of two pieces should help smooth out local magnetic fluctuations. 


 I've also looked at totally switching out the PG, with other different pieces, and the results
look the same; so its obviously not just specific to acouple PG pieces.  Also, the PG pieces have
been on and off the magnets numerious time for various test trials; so the results are real.  The PG
pieces are also fairly close to each other in dimensions; which might be necessary (?).  The PG
pieces I have are not precision machined so they vary in flatness and in other dimensions by around
~ 0.010".
    You might try using emery paper on a flat surface to give a flat under surface to the PG pieces? 


Another feature I like is the variable period with the variable PG spacing.  How I'am going to do that
with flimsy aluminum is yet to be attempted.  One may have to settle for whatever period they select before any "glueing" down of the aluminum.  Even being able to do so, is unique.

    Can you buy some copper foil from K&S Metals and use that? They stock 3 and 5 thou sheet. The Aluminum usually supplied is a Si alloy, not pure and it is paramagnetic. Copper is diamagnetic but far weaker. I ran up against these differences / problems when using NdFeB quad magnets for damping the Lehman.   



I've even put a large optical magnifying lens next to the model; to check for minute lockups, and
of course whether it physically oscillates around a reference "zero" mark I put on the magnet.  I can't say I've definitely seen any sticking yet on this model; but if it happens, I will.

    If you use a small lens to give a ~parallel light beam from a small bulb at rignt angles to the slip direction, small side movements probably won't be too obvious. 


One good indication that it works better is that I do see increased wider span tilt oscillation motion
effects with the 2 PG pieces than I've ever seen with one piece of PG.  It seems to be ~ 3X over
that of just using 1 piece of PG.
 
I don't yet really know the result of adding on steel/iron atop the magnets; as I've not yet done so.
I think I'll try 1/2" width X 1/8" thick iron initially.  The iron is commercially common size stuff, but
it does have dual rounded outer width edges; which might not be totally ideal.  The size is common;
but its different, as it was used as a desk drawer guide and was coated with a thin layer of copper
and then chrome plated.  Its probably (?) bright steel and not the black structural variety.
 
I've seen thin ~ 1/16" thick iron/steel work very well on kind of a "U" channel type setup...where the
(then) spectrographite rod levitated lower down on the deliberately lower middle channel magnet.
That was Chris's recommendation and it did dramatically improve its levitation height. 
    I bought some 1/32" galvanised steel sheet, which seemed to work quite well. I suspect that 1/8" will be much too thick and it will allow the field to be linked sideways, instead of looped over the top of the magnets and going through the graphite. Iron will carry about twice the field that the magnet can supply. You might consider filing the edges of the strips at 45 degrees, rather than leaving it at a right angle?



Yes; the aluminum paramagnetism has been seen in the past also; and its going to show up here
also.  The aluminum could be responsible for some of the sticking, with their various impurities.
I am using K&S Engineering aluminum; which seems to be purer stuff.  With the severe weight
limitations; its hard to consider using other metal/s.  I suppose I can hang up a piece of the stuff
on a long thread, and bring a magnet near it; to just see a rough indication of its general paramagnetism.
    K&S supply mostly 6061 Al alloy
    See www.ksmetals.com and http://en.wikipedia.org/wiki/6061_aluminum 
    
I am also presently using 2 plastic spacers in between the magnets; which are 0.035" thick X ~0.475" in width.  The spacer is a idea from John Lahr; and it does help a little for some slightly increased levitation.  I may try to find some thin plastic or non-ferrious metal that is 5/8" in width and somewhere around 
0.020 to 0.0315" thick, that could aid in setting up the iron on the magnet tops.  The iron will be magnetically normally forced against the joints for alignment.
 
    Regards,
    
    Chris Chapman