>At 12:18 PM -0700 4/4/2009, Kyle Hansen wrote: >>On 4/4/09 9:21 AM, "Bruce Johnson" <[email protected]> Broadcast >>into the ether: >> >>> A large magnet will not affect them, at least not a large magnet >>> you're likely to have access to, unless you also have a large steel >>> recycling yard or cyclotron in your backyard... >> >>I think I am gonna have a heart attack....Bruce is wrong about something. >>Someone make sure an asteroid isn't about to plummet into the earth. > >Re-read what Bruce wrote. A magnet that you're likely to have access... > >Ok... Just for kicks... I've got a drive here and a honking big >magnet. The magnet is so strong that once it grabs the drive, it >won't let go unless I pin the drive down with my feet and wiggle the >magnet off with both hands. After an hour of that exposure... I >hooked the drive up and ..... it works fine. Most of the data seems >intact; very little seems scrambled. And Disk Utility found no >errors in the file system. > >I'd say one needs a lot more powerful mechanism - like a real a/c degausser. > > >Of more concern to me is that whole cyclotron bit. Bruce, is there >something you're not telling us? > >- Dan. >-- >- Psychoceramic Emeritus; South Jersey, USA, Earth
I am assuming all HD cases are made of Ferrous material. With the both poles of the Magnet attached to one side if the HD case, the case in contact with poles provides a low reluctance path for the magnets Flux. This effectively short circuits the Flux and very little Flux penetrates the HD Case. A strong Magnet may saturate the Case material and allow some leakage into the platters. The entire HD case must be between the Poles of the Magnet for the Magnetic Flux to disturb the Magnetic condition of the HD. This would still require a Large Magnet since the HD Case provides a Shunt path for the Flux. The thin sheet metal of the case, if of Ferrous material, will saturate easily The Seams of the case provide air gaps that increase the reluctance of the Shunting affect and force more Flux to the inside . A large Cyclotron Magnet might have adequate separation at the Air Gap to accommodate the height of a HD. The pole pieces are Circular A Degausser is designed to accomplish all of the above with the added feature of cycling the Magnetic Flux from High to low to ensure minimum Flux Remanance. I once ruined a Credit Card by putting it in a shirt pocket where I had forgotten I was carrying a small magnet. I was going to tape the magnet to a wooden dowel to retrieve some hardware dropped in the nooks and crannies of my 62 Chevy 3/4 Ton engine compartment. HTH ErnieG --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed Low End Mac's G3-5 List, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
