PSN-L Email List Message

Subject: RE: Digest from 11/11/2006 00:01:37
From: "Jack Ivey" ivey@..........
Date: Tue, 14 Nov 2006 10:20:47 -0500


1/4"x1"x12" for $15.  Still not a bargain but about 1/10th the cost by =
weight of McMaster.

Why worry about the diagmanetism?  A symmetrical arrangement should =
balanced forces.

Warning: bad ascii art follows:

Cross section

   Cu tube                =20
_____________________________________         =20

            ------------                    <- | ->=20
      S   |  Cylindrical   |__N_______________ |
          |     Magnet     |                   |
            ------------                       |
______________________________________         |

Or better yet, put the tube on the boom and the magnet on the ground
(too lazy to fix artwork).

The rotation of the boom might provide a small amount
of unbalanced force, but I wouldn't think it would be too bad.


From: psn-l-request@.............. [mailto:psn-l-request@............... =
On Behalf Of ChrisAtUpw@.......
Sent: Tuesday, November 14, 2006 12:04 AM
To: psn-l@..............
Subject: Re: Digest from 11/11/2006 00:01:37

In a message dated 2006/11/14, JohnJan@........ writes:

At 11:36 PM 11/12/2006, you wrote:
>I have heard quarters are mostly copper ?

The dime, quarter, and half dollar are all 91.6% copper and the rest =
nickel.=A0 See:

Hi John,

=A0=A0=A0=A0=A0=A0 It is the much higher electrical resistivity which =
kills this application - apart from the susceptability and any =
implications of defacing the coinage. The damping effect on our 2p coins =
is far less that on pure Cu sheet.

Although Cu is slightly repelled by a magnet, the Cu Ni alloy will be =
slightly attracted. However, this attraction might be small enough to =

=A0=A0=A0=A0=A0=A0 Not with UK 'copper' Coins. US coins are 8.3% Nickel
The magnetic susceptibility of alloys of copper=20
and nickel in proportions ranging from 0.1 to 70=20
percent nickel have been studied. X-ray=20
photographs of the alloys show that they are a=20
homogeneous mixture of the copper and nickel=20
crystals. Although copper is only weakly=20
diamagnetic it requires 0.8 or 0.9 percent nickel=20
to neutralize this diamagnetic effect and 56=20
percent nickel is required before the alloy shows=20
ferromagnetic properties at ordinary=20

McMaster Carr  charges=20
$20.84 for a 1/16" strip of Cu, 1 inch wide by 6 inches long.

=A0=A0=A0=A0=A0=A0 This is an idiotic price. It is even more expensive =

Maybe flattening a piece of Cu pipe is still the best way to go. Have to =
be sure it's copper and not brass pipe.=A0 See:=20

=A0=A0=A0=A0=A0=A0 I suspect that you may not be approaching the right =
sales outlets. Go to a plumbing firm and ask if they have any odd =
lengths of large diameter tube? How about looking up metal suppliers / =
stockists / non ferrous? Scrap dealers may have Cu water cylinders.

=A0=A0=A0=A0=A0=A0 If Cu is so difficult to get, you can use soft AlSi =
sheet, but it is a bit paramagnetic. Pure Al may be difficult to find.
=A0=A0=A0=A0=A0=A0 Regards,

=A0=A0=A0=A0=A0=A0 Chris Chapman

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