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Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Many years ago I worked in a major loud-speaker manufacturing plant. In the Engineering portion of the plant was an hand-made device that made permanent magnets for the speakers .....and they were quite powerful!
I do not remember the specifics of the device as this was perhaps 30 years back but I do believe it had a large coil that appeared to be connected to a back of capacitors. The raw ferric material was placed within and a discharge (via a momentary switch) of the cap-bank imparted magnetism into the toroid. {I believe this is what happened: I am remembering from many decades back}. This was not an electro-magnet, it was a device that made a magnet from the toroid shaped material for surrounding the voice-coil emplacement. As I remember, the caps were charged and a substantial discharge resulted in the magnetism being implanted within the material. I have not seen any production device of this sort. It was a bench-made unit that worked quite well and was the work of a gifted employee.
As I searched for anything resembling this device I never came across anything that would be described as a "permanent-magnet-maker". Would anyone steer me to a general concept, schematic, or helpful theory so that I could start to design my own?
Thank you very much for any information. I have exhausted my common searches.
Registered Member #1667
Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 374
"Exactly what the magnetizing pulse, at many thousands of gauss, might do to the person directly is unknown"
In the course of ultrafast and functional MRI scanner development, several problems did arise and there are several papers that discuss the limitations of the human body. Medical devices use strong static and pulsed fields that cause heating and eddy currents in the patient. Regulatory laws have been passed to define the exposure limits within 0Hz ... 300GHz.
This reminds me of the reports of guys shaking their head while near or inside superconducting NMR magnets that experience strange effects.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
seem to recall somewhere that NIB magnets aere made in a similar way, induction heated to just above their Curie point then a very intense field applied as they are cooled to "set" the poles.
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Thank you all for the tips. I have a great interest in putting something like this together. Indeed, if it is successful, I am definitely going to scale it up as best I can. The whole issue is intriguing to me.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
Depending on what you're trying to magnetise it might be possible to use halbach arrays to generate the magnetising field. The record field strength with them is over 5T now.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
Quicksilver said "Many years ago I worked in a major loud-speaker manufacturing plant"
In the early 70's I was with a manufacturer of speaker systems getting raw speaker samples made up by manufacturers. Two were CTS of Paducah Ky and RSC. The sales people told me that the charged the magnets after the speakers were manufactured otherwise they could never get the pole pieces aligned or keep the gap from getting polluted with iron dust.
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Permanent Magnet Making Device
