[Boatanchors] Need magnetic shield for shaded pole motor

[J. Forster]

> John,
>
> Yes, copper in layers DOES work.  It is a matter of cost.

Never said it didn't...

http://en.wikipedia.org/wiki/Skin_effect

The lower the skin depth, the less material thickness is needed to achieve
a given level of attenuation. If you look at the graph in the link, you
can see that thin steel will attenuate far more than copper. Aluminum is
about the same as copper, BTW.

> Most don't understand the use of aluminum in shielding.  They have to
> begin understanding eddy currents.

Yes.

> I wonder how many have run across an electromagnetic system that has
> been in use for decades to separate aluminum?

Similat systems are use to distinguish genuine coins from metal slugs in
vending machines. They depend on the ratios of electrical conductivity to
magnetic properties and mass.

-John

================

>
> No, I am not smoking shrubbery!  Part of welding Inspection Training at
> Hobart.
>
> Bob - N0DGN
>
> On 1/2/2014 2:50 PM, J. Forster wrote:
>> The problem with mu-metal is that machining (cutting & bending) destroys
>> its magnetic shielding properties. There is another shielding material,
>> called Netic-Conetic that is more forgiving.
>>
>> Copper is OK, provided it's several skin depths thick.
>>
>> I do agree that coffee cans are a bit on the thin side. If you can find
>> a
>> tin-plated-steel can of heavier guage, go for it. A source might be the
>> larger 'family size' soup cans or the dumpster behind a resteraunt.
>>
>> The tin plating is mostly a rust preventative. A light coat of clear
>> Krylon will do fine.
>>
>> -John
>>
>> ===============
>
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