On Mon, 27 September 1999, "fxmurphy@............" wrote:

> 
>  
> Very nice it looks like you had alot of fun!
> 
> I too tried on sunday but did not have alot of luck finding
> any diagmagnetic material. I tried melting some non lead fishing 
> lures, but I think they were made of mostly tin.

Haven't worked with bismuth myself.  According to what I
have read busmuth reloading shot, can be melted on a
typical stove.  Was this the case?  Or, blowtorch high
temperature melting?
> 
> What happened was the neodymium magnet would jump from top 
> to bottom, very slowly but I could not stabilze it.

It could be that your adjustment thread on the upper magnet
is too coarse...if ? you actually had bismuth?  One has to
slow down and back up the magnet if the neo jumps up in
the sandwich of graphite/bismuth.  Sometimes, it a matter
of fine adjustment.
  
> So I guess I am going to have to scrounge for some carbon rod.
> 
> Would like to hear more about finding a good source of 
> diagmagnetic material.

With my 4 day experience...ha....I frankly don't know of
any commercial outlet for graphite, at least any one, 
which sells the stuff cheaply.  Maybe Mcmaster-carr has
carbon rods, but even the smallest diameter stuff is
expensive for what they give you....and....theres no
guarantee its even diagmagnetic at all.

Here in Denver, the only place I found some, was a local
surplus outlet (general, but mostly mechanical, not
electronics), and they had roughly 50-60 variety shapes,
all jumbled together.  I picked up a variety and took
them home, for testing, using a simple string to a 
beam balance about 8" long, with a magnet on each end.
Bringing the carbon/graphite, close to the magnet on
one end, it will either be repelled slightly, or it
will be attracted to the magnet, or nothing will happen.

Another less sensitive method is using 1/2" scotch tape,
about 4-5" long, or longer, and hanging it from like a
overhead cabinet in the kitchen.  Attach the test carbon,
bring the magnet close (this works better with a larger
neo magnet than the small neos like at Radio Shack). 
One could also just hang it on string also...

Either method, theres a very limited range of motion on
either the magnet or test carbon, probably less than 
1/8" for the scotch tape method, and higher for the
torsion/beam approach.

The real message with finding carbon is that its a 
search, find, test approach.  Old motor carbon brushs,
seem to be the most common to me.  I wouldn't want to
get into old batterys for the electrodes.  Perhaps 
motor repair shops (probably scarce anymore).  Junkyards
may have old DC motors, but if you have to buy the motor,
I'd look elsewhere.

Look for the blackest carbon brushs.  Forget the 
grayish black, copper colored, or even the silvery
appearance stuff...too much impurities I would think.
Again its a shotgun approach, and will cost money to
acquire even test pieces, that may or may not work.
The size of the 2 carbons that work, will have to
fit the neo you are trying to float, and you will
have to find something to use as spacers.

I'd also hit up electronic surplus stores, most have
a variety of older equipment, and I'd guess that
perhaps a minority would have "some" old carbon rods
or carbon brushs.

I'd probably have a better idea of source, but 4 
days of acquantance with the subject, doesn't yield
any known (guaranteed)commercial source yet.  I've
checked on the net mind you, but nothing found.

Failing that search for graphite...there is net
sources/references for bismuth gun reloading shot,
but the purity is in question?  Some people like it
better, some don't...  I hear alot of sporting gun
shots could have loaded shotgun shells with the
stuff; but I really wouldn't want to mess with that.

http://www.bismuth-notox.com

The above site gives a local search function for 
your area.

http://www.precisionreloading.com/index.html

The above site sells direct; credit card, but the
quanity (7 pounds) at some $78.00; is a wee bit
too high priced for what you would use. 

Stable/static levitation devices can be bought
ready made, at probably a variety of sources.  I
only web address I have handy is this:

http://www.physics.ucla.edu/marty/diamag/lev4sale.html

Two models, one for $49, and the other is $69, unless
the price went up.  It might be cheaper in the long
run to buy...rather than homebrew.  Of course, theres
the challenge in making your own...ha....  

Maybe in time, I'll have more data....

Meredith Lamb



Signup for your free USWEST.mail Email account http://www.uswestmail.net

_____________________________________________________________________

Public Seismic Network Mailing List (PSN-L)