X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 1 [X] Return-Path: Received: from vms046pub.verizon.net ([206.46.252.46] verified) by logan.com (CommuniGate Pro SMTP 5.1.6) with ESMTP id 1823129 for flyrotary@lancaironline.net; Thu, 08 Feb 2007 00:47:31 -0500 Received: from [127.0.0.1] ([71.98.163.20]) by vms046.mailsrvcs.net (Sun Java System Messaging Server 6.2-6.01 (built Apr 3 2006)) with ESMTPA id <0JD400EAJQQWQCGA@vms046.mailsrvcs.net> for flyrotary@lancaironline.net; Wed, 07 Feb 2007 23:47:22 -0600 (CST) Date: Thu, 08 Feb 2007 00:47:28 -0500 From: Finn Lassen Subject: Re: [FlyRotary] Re: wire routing In-reply-to: To: Rotary motors in aircraft Message-id: <45CAB970.1020703@verizon.net> MIME-version: 1.0 Content-type: multipart/alternative; boundary=------------070608070400070105010706 References: User-Agent: Thunderbird 1.5.0.9 (Windows/20061207) This is a multi-part message in MIME format. --------------070608070400070105010706 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Lynn, I'm afraid you'll have to eat this one. You use steel, iron or "Mu" metal to shield from magnetic fields. Alu is fine for shielding electromagnetic _waves_ (radiation), to use in waveguides, etc. But it will NOT shield pure magnetic fields as seen from a permanent magnet or generated by an electro-magnet. The Alu IF cans are not used to shield magnetic fields. Maybe the confusion comes about because it's called electro-magnetic waves. Do the test: take an oscilloscope or a TV and move a permanent magnet near the neck of the picture tube. Repeat with an Alu plate between the magnet and the tube neck. Repeat with an Iron (not stainless steel) plate between the magnet and the tube neck. See the difference? Of course I've completely forgotten what started this thread. What were we trying to shield from? Finn jwvoto@itlnet.net wrote: > ---- Original Message ---- > From: Lehanover@aol.com > To: flyrotary@lancaironline.net > Subject: [FlyRotary] Re: wire routing > Date: Sun, 4 Feb 2007 01:09:03 EST > > >> In a message dated 2/3/2007 11:56:08 P.M. Eastern Standard Time, >> jwvoto@itlnet.net writes: >> >> Am I wrong, I believe that aluminum will not shield magnetic flux, >> giving >> only electrostatic shielding; only steel will shield magnetic flux. >> >> Wendell >> >> >> >> Notice that your IF cans have aluminum all around? Never seen an IF >> can? >> >> In the olden days radios had big vacuum tubes, and open core >> capacitors to >> adjust tank circuits and control frequencies. The Inter-frequency >> transformers >> had to be shielded to control phasing and awful noise in the output. >> Thus >> the aluminum can shielding. Good for wave guides as well. >> >> Ferris metals concentrate flux fields (conduct flux lines well) and >> are used >> in the cores of transformers and solenoids. >> >> Lynn E. Hanover >> > > Why are transformers made with ferris metal? If you want to contain > all the magnetic flux, I still content that steel or mu metal is the > way to go. I have never seen an aluminum magnet. > Wendell > > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/ > > > --------------070608070400070105010706 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit 
Lynn, I'm afraid you'll have to eat this one.

You use steel, iron or "Mu" metal to shield from magnetic fields.

Alu is fine for shielding electromagnetic waves (radiation), to use in waveguides, etc.
But it will NOT shield pure magnetic fields as seen from a permanent magnet or generated by an electro-magnet.
The Alu IF cans are not used to shield magnetic fields.

Maybe the confusion comes about because it's called electro-magnetic waves.
 
Do the test: take an oscilloscope or a TV and move a permanent magnet near the neck of the picture tube.
Repeat with an Alu plate between the magnet and the tube neck.
Repeat with an Iron (not stainless steel) plate between the magnet and the tube neck.
See the difference?
 
Of course I've completely forgotten what started this thread. What were we trying to shield from?


Finn


jwvoto@itlnet.net wrote: 
---- Original Message ----
From: Lehanover@aol.com
To: flyrotary@lancaironline.net
Subject: [FlyRotary] Re: wire routing
Date: Sun, 4 Feb 2007 01:09:03 EST

  
In a message dated 2/3/2007 11:56:08 P.M. Eastern Standard Time,  
jwvoto@itlnet.net writes:

Am I wrong, I believe that aluminum will not  shield magnetic flux,
giving 
only electrostatic shielding; only steel will  shield magnetic flux.

Wendell



Notice that your IF cans have aluminum all around?  Never seen an IF 
can?

In the olden days radios had big vacuum tubes, and open core
capacitors to  
adjust tank circuits and control frequencies. The Inter-frequency 
transformers 
had to be shielded to control phasing and awful noise in the  output.
Thus 
the aluminum can shielding. Good for wave guides as well. 

Ferris metals concentrate flux fields (conduct flux lines well) and
are  used 
in the cores of transformers and solenoids.  

Lynn E. Hanover
    

Why are transformers made with ferris metal?  If you want to contain
all the magnetic flux, I still content that steel or mu metal is the
way to go. I have never seen an aluminum magnet.
Wendell


--
Homepage:  http://www.flyrotary.com/
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