Hi all,

This might be an ideal value magnet for those seeking a strong
magnet/s and very cheap unit/s for their seismos.  The size
alone makes for alot of mounting convenience in using
non magnetic spacers to adjust the width you want between 2
of these magnets.  In this case, a relay coil between would make
the easiest approach.   The length alone presents possible
multiple coil or damping coil possiblities.  They also present
eddy current damping ideas.  I would think they will do relatively
very well for coils 3/4" thick or less (The thinner the more gauss).
The poles are right; 1/2 the thickness, or each side is a separate
pole.  See:

http://www.alltronics.com/          and use the contents index
on the left side and go to magnetic devices.

See the "2000 gauss super magnet  Black rectangular magnet,
2.5" long x 1.125" wide by 0.375" deep.  These will definitely
hold your calendar up!", near the bottom of the scrolled screen.
Its # 98N013, at $5.95 each.  They show acceptance of Visa
or Mastercard credit cards.

I got 2 of these.  At first I thought they were alnico, what with
the iron rust stains (a artifact).  One was painted black (peeling),
and the other white (peeling).  But, they are neodymium.  The
thickness measured more, some 0.4" thick.  I have to presume
they were once mounted in iron/steel and exposed to the great
outdoors for some time before being salvaged and presented for
sale.  I just used elbow grease and sandpaper to remove the old
paint.  One could repaint or even use a Sanford felt tip pen and
lightly coat them with that plastic like ink.  These have to be
handled carefully, they are that strong....they will crush skin,
or, break/chip if allowed to slam together, or, onto other steel
or iron.  The 2 units I got, only had slight small spots/depth of
oxidation where they were exposed to the weather.  There
were small edge chips here and there, but it doesn't affect
much for its use.

I paid per check, but you have to use the comments section, and
also ask for shipping and total charges on the web form they have.
Its about 2-3 weeks for delivery.  Also, I would not recommend
purchase of any of the other displayed magnets...these are a
much better value (one other size I got was unfortunately
badly oxidized).  Right off I have no idea of non-USA shipping.

As mentioned before, one can use non-magnetic spacers to fit
the coils you have between them.  My main sample test, I used
a relay coil with a resistance of 151 ohms; .45" thick X .8" in
diameter.  On the magnet "sandwich" with 1/2" spacers it maxed
out with .6v.  With a adjustable gap vise (literally), it maxed out
at .9v with the same spacing adjustment.  Of course with more
resistance, it would more voltage.  My only other test was with
a 9.88K coil using the same adjustabe vise, and it delivered a
max of ~9 volts. If you use a normal amplifier it should deliver
quite well in a less than precision seismo setup; which seems to
be the norm for most of us.  For these, you might have to reduce
the gain, or resort to using input resistors on the amplifier you
now use?

Don't ask the "why's?", they could have been misled too....,
but this unit is a really big bargain for the size.  I have no idea
of the quanity on hand, or whether any run will expose what
they really are and have the price go up.  Uhhh....Order your
calendar magnet today....its the time of year, and it will likely
be better than the "old" one/s...ha.  

Meredith Lamb


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