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Discussion Starter · #1 ·
I now have over 35 tuning forks which either will not hum or hum drawing excess current and hence vibrate too slowly. I have not yet devised a way to measure the magnetic field strength accurately, but using an empirical method employing the deflection of a compass needle, have shown that there are wide differences in field strength. This is particularly so between the magnets on individual forks. One magnet even had reversed polarity.
What this leads to is the importance of finding how to remagnetize tuning forks. Bulova in its heyday offered a service to do this. I would welcome any suggestions from members on how this was done or whether anyone is currently doing remagnetizing. I intend to do some experiments to see if I can do it myself but at the moment have little idea of what parameters will be necessary. About one in four Accutrons I have bought cannot be adjusted up to speed with the regulators and the ratio is much worse among old movements.
I wonder what professional Accutron service people are doing about getting good tuning forks.
 

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I know how it is done because I use to do it with the same type of magnet material, Aircraft engines use magnetos for ignition and magnetos require no DC power to make that ignition, instead they use a rotating magnet which is made of the same magnet material which can be remagnetized, all it takes (for one magnet) is two large coils of copper wire wrapped around a u shaped iron core (one coil on either side of the "U") and at the opening of the "U" iron blocks are slid from both tips of the "U" into contact with the "pos" and "neg" of the magnet and then DC current is pasted through the coils with the "POS" of the DC current going to one coil and "Neg" DC current going to the other coil with both coils terminating at the end with each other, the size of the coils and the amount of DC current is dependent on the size and strength of the magnet in question, very basic electromagnetic stuff.......

The same thing could be done to the magnets in our tuning forks with a "W" shaped iron core and three coils of wire......

magnetic field strength is measured in "gauss" with a gauss meter pasted by the magnet......
 

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That why I said "the size of the coils and the amount of DC current is dependent on the size and strength of the magnet in question" lol :thumbup:

I would think it would be something hand held or close to it and not something that took two people to lift like what I used with magneto magnets......

It VERY basically would be something like this.....

 

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I actually work in high magnetic field research. Pretty easy to map the field of a magnet. Maybe I should give it a go. NSF wont mint me wasting time on accutron magnets ;)
 

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Update: I made an inquiry of Samantha concerning her experience with remagnetizing tuning forks at Bulova. This was her reply,
" I have never seen it done and we never did it in the service center. I've also never heard of anyone doing it."

I will be checking with one other source concerning remagnetizing TFs.

Regards, AT
 

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I would imagine that remagnetizing would be a factory provided service only, with the right equipment it only takes a very short time (like 10 seconds at the most) with the fork in hand, when fork magnets are manufactured they don't start life with the field strength they have when they go into a watch, they have to be magnetized before use.......

 

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Discussion Starter · #9 ·
Thanks everyone for the replies. Since posting the thread I have done a lot of research on electro magnetizing. Solving the design parameters for a device sufficiently small is a daunting challenge for me as my stage one university physics of over 55 years ago is creaking at the seams. It has to generate the same field strength as a large device so has to be able to conduct sufficient current through sufficient turns of wire of a diameter thick enough to carry the current. I have therefore put this on the back burner and am going to try a different strategy. I have ordered some Neodynium magnets which I hope may be strong enough to to re magnetize the Alnico tuning fork magnets. The re magnetizing will have to done in a jig to ensure the proper axial alignment of the poles. Watch this space for further instalments.
 

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Update: I followed up with a second source, who for a good part of his 78 years worked for Bulova on Accutron. While Accutron offered "refurbished" coils and TFs, his observation (at least with respect to TFs) was the source was returned TFs that were not defective. He, too, was not involved in re-magnetization nor was there any such service in his considerable years with Accutron.

As an aside he further shared this: at one time the state of Indiana required certification of watchmakers. With the advent of "electronic" watches this component was added to the certification requirement...an engineer with ties to Indiana University and Purdue was recruited for this task. He had a particular interest in Accutrons and developed a system for re-magnetizing tuning forks. He found that he was able to restore TFs to function using the process...but abandoned the project after determining the duration of the restoration was not reliable beyond 3 months.

Don't shoot me...I'm just the messenger. I have no reason to doubt the veracity of this information.
It will be interesting to see what is further learned through the efforts of magnetchief and/or vim.
Regards, AT
 

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Did the engineer with ties to Indiana University and Purdue say when he developed that system for re-magnetizing tuning forks and what his system entailed ? if it was back in the 60s or 70s a lot has been learned since then like the advent of Neodymium magnets and hard pulse magnetizing of rare earth magnets, Since 1990 Magnetizer technology has advanced considerably.

Unless there has been physical deterioration of the magnetic materials used in the TF and provided that the material has not been damaged by extreme heat, the magnets can be re-magnetized back to their original strength, whatever his system was it sounds like he wasn't fully saturating the magnets.

To fully saturate a magnet, it must be exposed to a magnetizing field of sufficient amplitude for a time long enough to orient all of the mass of magnet, Alnico requires 3000+ Oersteds. If that engineer was unable to orient all of the mass of magnets the un-oriented parts of the magnet will essentially try to demag the parts that are, it would seem that his magnetizing field was insufficient in amplitude to fully saturate the magnets. Essentially it's a all or nothing process.

The effect of time on modern permanent magnets is minimal. Studies have shown that permanent magnets will undergo changes immediately after magnetization. These changes, known as "magnetic creep", occur as less stable domains are affected by fluctuations in thermal or magnetic energy. These changes decrease as the instabilities decrease. Rare Earth magnets are not as likely to experience such changes because of their extremely high coercivity. Long-term time versus flux studies have shown that a newly magnetized magnet will lose a fraction of its flux as time goes by. Over 100,000 hours, these losses are in the range of essentially zero for Samarium Cobalt materials to less than 3% for Alnico 5 materials at low permeance coefficients.

The ability of a permanent magnet to support an external magnetic field results from small magnetic domains "locked" in position by crystal anisotropy within the magnet material. Once established by initial magnetization, these positions are held until acted upon by forces exceeding those that lock the domains. The energy required to disturb the magnetic field produced by a magnet varies for each type of material. Permanent magnets can be produced with extremely high coercive forces (Hc) that will maintain domain alignment in the presence of high external magnetic fields. Stability can be described as the repeated magnetic performance of a material under specific conditions over the life of the magnet.
 

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I could be way off base but it seems to me that I had read somewhere that the tuning fork arrangement Accutrons used got back some of the power that it takes to keep the fork vibrating and in that way makes the movement a very low power drain on the battery, And again I could be off base but it seems to me that the weaker the fork magnets are the higher the power drain on the battery is which is due to what seems to be the lower amount of power the weakened fork magnets give back because of the lower power the magnets produce moving back and forth inside of the coil or coils........
 

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Accutronitis:

No details were provided as to the means of remagnetization of the Accutron TFs. The time-frame would have been 60s-70s. The information was offered by a long-time Accutron watchmaker who personally knew the the individual who undertook the remag process.

This speaks to some of the parameters in the circuit design and is worth a read: http://www.elektron.demon.co.uk/works.html

Regards, AT
 

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The time-frame would have been 60s-70s
That's what I had thought, Sooooo much been learned since then, Since 1990 Magnetizer technology has advanced considerably.

Thanks for the link. I think this is what I had read and I was kind of right.....

The magnets of course also induce a voltage in the drive coils
This has the advantage of prolonging the life of the cell considerably
That's what I thought so with weaker magnets the induced voltage will be less which will lead to higher microamperage draw than normal which will shorten battery life, So in short "Weaker Fork Magnets Will Shorten Battery Life"......

Facts about nickel......

Until the invention of rare-earth magnets, such as neodymium-iron-boron, the strongest permanent magnets – Alnico magnets – were made from a nickel alloy: mainly aluminum, nickel, cobalt and iron. Unusually, Alnico magnets retain their magnetism even when heated until they glow red hot.

Supernova 2007bi was observed in 2007. One of the products of this supernova was nickel-56, synthesized during the explosion. Nickel of mass three times greater than our entire sun was made. Nickel-56 is radioactive, decaying to cobalt-56, which itself decays to stable iron-56.
 

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Discussion Starter · #15 ·
I have now made two attempts to post an update on where I have got with re magnetizing. Both times the website has timed me out and then lost my text when I tried to log in again. This has also happened in the past. I am not going through this again and henceforth will only post trivia. I have very useful information to pass on so if anyone is interested PM me with your email address and I will send it to you.
 

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I have now made two attempts to post an update on where I have got with re magnetizing. Both times the website has timed me out and then lost my text when I tried to log in again. This has also happened in the past. I am not going through this again and henceforth will only post trivia. I have very useful information to pass on so if anyone is interested PM me with your email address and I will send it to you.
What browser are you using? I've never had that happen on this site.
 

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I have now made two attempts to post an update on where I have got with re magnetizing. Both times the website has timed me out and then lost my text when I tried to log in again. This has also happened in the past. I am not going through this again and henceforth will only post trivia. I have very useful information to pass on so if anyone is interested PM me with your email address and I will send it to you.
Hello - I am interested in your info on re-magnetizing tuning forks. Please PM me and let me know who to obtain it. Thanks!
 

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Do you realize you're replying to something he posted OVER 6 YEARS AGO??? Don't get frustrated if vim203 doesn't give you an answer.
 
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