Magnet Destruction

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Model T Ford Forum: Forum 2017: Magnet Destruction
Top of pagePrevious messageNext messageBottom of page Link to this message  By Lenney Glenn on Sunday, February 12, 2017 - 05:04 pm:

Has anyone accidently applied battery current to a model t magneto and destroyed the magnetic field of the enclosed permanent magnets???


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Kossor - Kenilworth, NJ on Sunday, February 12, 2017 - 05:38 pm:

Yes, it will do that. Fortunately, you can do an in car recharge. You can find instructions for in car recharge here on the forum. Good Luck with it and please report your results.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Lenney Glenn on Sunday, February 12, 2017 - 06:40 pm:

Mike have you or do you know first hand of someone accidently doing this. I have done several in car recharges,sometimes without a compass by removing the spark plugs and jacking up a rear wheel then applying a dc current. I have yet to demagnetize the magnets. I work with many types of dc permanent magnet motors in industrial applications and routinely reverse the armature polarity and never damaged the magnets. some of these motors are reversed under high current , high torque conditions. Some even go into stall mode. Yes
, I know a PM can be weakened by applying an opposing field. I am sure Henrys magnets were not of the quality we use today. Maybe that is why they are so easily demagnetized?
.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Lenney Glenn on Sunday, February 12, 2017 - 06:52 pm:

I failed to mention that I understand that a high field of opposing polarity produced by high current with the flywheel locked down would certainly weaken the ford magnets.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Kossor - Kenilworth, NJ on Sunday, February 12, 2017 - 07:25 pm:

Lenney, I have not done the in car recharge procedure but Tom Carnegie has along with considerable experimentation including reversing the magnet charge which may interest you. Check out this post for more information: http://www.mtfca.com/discus/messages/506218/528397.html


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Sunday, February 12, 2017 - 07:37 pm:

Wow, Lenney G! It sounds like you may be the one that needs to be answering these questions here!
I have never accidentally discharged a magnet, or a field of them. But I have heard of several people doing so in model Ts.
I have quite a lot of background in electricity, and electronics, especially systems work. I have worked with electromagnetic fields more than a little, and figure I know enough about them to think I know something and get myself in trouble.
Several years ago, I recharged a model T magneto that I figured had been discharged (either accidentally or deliberately) as a running engine. It was the most dead magneto I have seen (so far?). I tried to determine what the original polarity was, but was unable to do so. I finally chose one, and tried to recharge the magnets with a 50/50 chance of being wrong. After several attempts, it clearly did not want to take charge that direction. I finally set it back up in the reverse direction, and pushed it back that other way. The polarity reversed, and the strength quickly went up to model T normal (by barn-test standards).
Past discussions of magneto recharging on this forum, and what I thought I knew before, said it should not have happened that way. But it did. The magnets all seemed to have a resistance to taking the charge one way, but took it the other way easily.
All that may be nothing more than a minor curiosity. At most, a curious anomaly.

I have not yet done a magneto recharge "in the car". I have recharged a few flywheels out of the engine (using a T field coil), and individual magnets a few times using special coils made for that purpose.

Of course, real magneto/magnet destruction is when the magnets begin coming off of the flywheel with the engine running. Now, THAT makes a mess!
Drive carefully, and enjoy, W2


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