PSN-L Email List Message

Subject: Re: further magnet ideas
From: Charles Patton charles.r.patton@........
Date: Fri, 09 Nov 2007 10:32:48 -0800

One thought that occurs to me is to start with a rail of steel angle 
iron (for a flux return) then add the two "pills" that Meredith mentions 
below separated by some distance (the length of your pivot) and 
installed with one N and one S down to the rail.  On top of the magnets 
get some of the flat carbide blades that are replacement parts for some 
paint scrapers.  These are triangular (I seem to remember -- I'm 
traveling so I can't go look at them at the moment) about 1" on a side 
and about 0.020" thick.  I bought some from ACE hardware, but they're 
probably also available from Home Depot style stores.  The key here is 
that the angle iron rail gives a flat common reference surface from a 
geometry viewpoint and has enough bulk for a good flux return.  The 
carbide scraper blades give you the hard, low rolling friction surface 
-- better than the gold or the composition of the magnet.  As a side 
point, one of the reasons the high strength magnets are plated with 
nickel or gold is that their alloys are particularly subject to 
corrosion, hence require plating to protect them.  I strongly recommend 
not removing the "gold" coating as it would make the magnets subject to 
atmospheric deterioration.
Charles Patton

meredith lamb wrote:
> Hi Randall and all,
> As far as utilizing a "crossed rod" pivot/axis (crossed/rolling 
> cylinders) of neo magnets, the standard
> neo magnet has its poles on the ends of these rods/cylinders...making it 
> somewhat difficult to do much
> with them.  Forcefield magnets ( 
> ) does have a 1/4" diameter x 1"
> length (gold plating...of course..ha) magnet were the magnets poles are 
> through the diameter. 
> It is item #0056, and sells for $3.  This would make perhaps right angle 
> positioning one magnet
> across 2 other magnets of the same polarization alot easier....(who 
> knows they might center pretty
> good?).  Of course the gold plating isn't a hard surface; but it might 
> make for a interesting axis/pivot
> as the "mass" weights will be fairly limited anyway.   Generally....the 
> gold plate "could" peel off
> after time or from impact abuse more easily than the standard chrome 
> plating.
> I "think" this could be what Chris Chapman has in mind?  These were most 
> useful for diamagnetically
> levitating select pencil leads afew years back.  Unlike some magnets; 
> these have been around
> for a number of years and I doubt Forcefield will drop selling them 
> anytime soon.   
> I'd think the axis/pivot application could be used for both a hanging 
> horizontal...and perhaps a vertical
> axis/pivot also.
> Meredith Lamb 
> On Nov 9, 2007 5:53 AM, Randall Peters  > wrote:
>     Hey,
>        Don't know whether we qualify as 'great minds', but at least
>     we're 'on the same sheet of music'.  The first thing I thought about
>     following the 'obvious standard pendulum' was whether the idea could
>     be extended to verticals--just as Meredith suggested.  Also, Chris
>     alluded to another element of the
>     idea--rolling cylinders.
>        Before the 'dangling pen' I had noticed that two cylindrical rare
>     earth magnets roll together nicely.  If you make one stationary and
>     'ping' the other it oscillates nicely.  What's the primary source of
>     damping?   Some is the rolling friction, and some derive from
>     induced eddy current in earch.  If
>     we reduce the rolling part, who cares about the eddy current parts?
>      After all, they are part of the desired Q-reduction that has become
>     standard to eliminate transient response of the instrument.  Thus an
>     arrangement I think could have promise is the following.
>        A few years ago, now retired Georgia Tech seismologist Tim Long
>     (very highly honored in our state) sent me a picture of a vertical
>     he designed.  Unlike with most instruments that use Lucien LaCoste's
>     famous zero-length spring, Tim put the 'approximate' zero-length
>     spring (probably a screen door
>     type) below the boom.  This is accomplished by flex-pivot elastic
>     strips at the short end (top) of the U-shaped steel iron strip that
>     serves as the 'backbone' of the instrument.
>        I believe that Tim's flex-pivot strips could be replaced with two
>     rare-earth magnets, one 'stuck' to the top of the frame and the
>     other glued to the non-sensor end of the required non-ferrous boom.
>      The boom magnet would roll on the frame magnet, with the contact
>     force being made small (the two
>     trying to pull apart) by 'proper' placement of each of the magnets.
>       You amateurs are 'like a fresh cool wind' on a 'hot-as-hell
>     Georgia August afternoon' and I love your enthusiam toward what
>     might to the 'pro's' look like hare-brained ideas.  I look forward
>     to additional brainstorming on these thoughts.
>        Randall

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