Magneto failure

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Model T Ford Forum: Forum 2017: Magneto failure
Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Friday, September 22, 2017 - 06:33 am:

I am working on a 1917 engine to put an electric starter on it and looking after the not working magneto.

Here is what I found. It shows what kevlar can do when it has oil and metal residue.

Andre
Belgium







Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Friday, September 22, 2017 - 07:14 am:

I'm pretty sure cotton would do the same. As a matter of fact, the metal particles will stick together and chain up on the magnets to some extent with no fiber in there to help it, but probably not that bad. I like wood bands. Part of the reason is that they do not make fiber to clog the oil tube. What wears off of wooden bands is just tiny particles that go out when you change oil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Osterman on Friday, September 22, 2017 - 07:19 am:

Interesting. So, here's the thing .. normal engine wear also produces regular deposits of fine iron; not as bad as this, but it's there. Should the hogs head be removed after the initial breaking in of a newly rebuilt engine to clean off the magnets?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Rogers - South of the Adirondacks on Friday, September 22, 2017 - 07:44 am:

Wait a minute- are we talking about kevlar again? Five times stronger than steel so I don't think cotton would have nearly the same effect.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Friday, September 22, 2017 - 08:48 am:

It is the second time I see this on a nearly fresh rebuild engine.
The first time there was a magneto failure about a year after the rebuild. I took the coil ring out the engine and tested it for polarity with a 12V battery.
Here is what happened.

Andre
Belgium



Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Friday, September 22, 2017 - 09:35 am:

I'm no fan of Kevlar bands, but I do NOT believe they 'grind' away material from the drums like emery cloth. Just because something has a higher tensile strength than steel doesn't mean it is abrasive to steel. It just means that it takes more force to pull a piece of it in two than it does to pull an equal size piece of steel in two.

Metal filings are normal inside an engine, especially after a fresh rebuild, although that does look like a lot of them. When you hone that crosshatch pattern in the bore, you're making thousands of tiny little ridges that get worn off by the rings and the rings get worn as well, as the rings and bore seat against each other. It's all part of the "Breaking in". On a new car, all that goes in the oil filter. Since a T has magnets, that's where it shows up. Any fibers (Cotton or Kevlar) that are also in the mix get trapped in that goo as well.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger - Wyoming on Friday, September 22, 2017 - 10:03 am:

"Five times stronger than steel"

Yes... by WEIGHT...so while we're throwing around frightening and official sounding partial truths, I'll add one: Human hair is also stronger than steel (in tensile strength)

Whatever shredded those bands would have done the same to cotton, ten-fold. As for the metal impregnation of the lint, Kevlar is abrasive resistant, but in and of itself, not an abrasive.

If this has happened twice on fresh engines, there is a process or procedure that is being done improperly. There are plenty of professional engine builders providing the hobby with rebuilds bearing Kevlar with no ill effect, and certainly not experiencing infant mortality like this engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Friday, September 22, 2017 - 10:15 am:

Applying a 12V car battery directly to the mag ring with jumper cables is passing about 48 amps through the coils and can in fact cause the pictured effect on even a good ring but it does let you see which coil is the weakest. Not a good idea although lots of folks are rather cavalier in doing that. The entire coil ring is typically .25 ohms total resistance. Why not put a 12V bulb in series (#1156) and check each coil for voltage drop across it to see if it is then the same as the others before you hit it with a higher current in order to burn it up.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Friday, September 22, 2017 - 11:01 am:

John,
I normal use a 12V 21A bulb in series with the coil loop to test the loop on polarity and voltage drop. On the burning coil the test was not clear so I was thinking " it is broken I can't brake it harder" so I put 12 over the coil loop and it showed me direct the short. I replaced the broken coil (double oval)and the loop is working again.

This time I didn't need to test it after cleaning the short was visible. Need to build a new coil and replace the broken one.

Andre
Belgium







Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Friday, September 22, 2017 - 09:49 pm:

What bulb has 12V at 21 Amps. That is one heavy duty bulb and offers not much current limiting. Or did you mean 2.1 Amps.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Saturday, September 23, 2017 - 01:32 am:


I've had fuzz like that too. It wasn't caused by the band lining.


It was caused by a bad drum that chewed it up.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Saturday, September 23, 2017 - 02:40 am:

No John it should be 12V 21W. It takes 1.7A

Thanks for seeing the mistake.

Andre
Belgium


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Osterman on Saturday, September 23, 2017 - 06:41 am:

The '23 after a week of driving with a new rebuild. This was the second time I opened the cover for inspection.

Fuzz


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