MTFCA Forum

Some years ago (probably 7-8) I remagnetized my flywheel magnets in my pick-up T. It was done in-situ following the instructions given in the club's leaflet about the electrical system.

It has worked like a charm - until last summer where it quit working on magneto. The strength has weakend to an extent so a broken tooth from my gearbox break down some years ago which apparently have been sitting in the magnet hidden, came off and went out when I changed oil.

I'm overhauling the engine in my touring as well, and the flywheel magnets on that was remagnetized by Donald Lang before it was shipped over. It has also worked just fine, but now when I took the flywheel off for balancing, I noticed that virtually all magnetism was gone.

I'm perfectly aware of the if you do it reverse to the original orientation of the magnetism, it will tend to reverse the poles back. Can it be that I (and Don Lang) have done it reverse? Or is it just how it goes?

They tend to lose magnetism over time due to heat cycling and vibration, but they should give service for years. Any sudden loss of magnetism is probably due to an electrical problem applying DC power to the magneto coils. Doing arc welding on or near the car might cause some loss of magnetism, especially with an aluminum hogshead. I'm not familiar with the possible reverse polarity issue, but I'd think it would be best to re-magnetize each magnet to the original polarity. Annealing weak magnets, then recharging them while at 200F or so might give a more permanent job.

My T magnets held their magnetism for the 45 years our car was in our family, enough to not only pop the coils but run the headlights AND a bulb eaach in the taillight and side markers in the oil lamps (28 volts, have them a nice "flicker" and could take being run up.)

IDK if the previous owner recharged them before 1970, but until I had to let the car go to move here, she ran on mag like a champion AND gave me enough headlights to be legal...

So if the magnets lose their magnetism to the point your mag no longer works, save someone putting battery voltage to the mag post or some other "don't do this" scenario, I'm honestly lost as to why they died. Overheating? Who knows.

I have a huge old stationary gas engine that I know for certain has never had the magneto serviced since well before WWII. It still starts and runs well on its WICO magneto.

Well if it worked after recharging the magnets, then I'd say it wasn't done wrong some magnets are just weak and don't take a full charge, you may just have to recharge them from time to time.

There are several things which will affect the operation of the magneto.
1. Magneto coil winding cut by something which was caught in the magnets and cut the winding.
2. Wear on the rear main bearing of the block which pushes the magnets farther from the coils. This happens with a well worn engine.
3. Battery accidently connected to the magneto which discharges the magnets.
You will need to pull off the hogs head to check the magnets to see if they are really discharged or if one of the other things could have caused the problem.
Norm

You can hook a 6 Volt battery to the Mag Post and remove all the magnetism from your magnet set.

You need about 40 DC Volts and a 30 to 40 Amp supply to put it back.

I have 3 T’s and on rebuild I magnetized the magnets 1 at a time as I put the flywheel together. All 3 engines were redone at least 12 years ago and run OK on mag.
I don’t know how Ford did it at the factory but when he did it the flywheel was put together and ALL THE PARTS WERE NEW.
These days we’re dealing with 100 year old magnets and in my mind on a rebuild it’s best to do recheck and magnetize the magnets one at a time.

BUT that’s my opinion and others will surely have differing opinions.

Thank you all for your remarks. In both instances it is the actual strength of the magnets I know is weak, not just the output. The 1914 touring the engine is pulled and disassembled and I just noticed that the magnets where weak. When Just (re)magnetized they can hold a cast iron piston.
I am pretty sure it is not a matter of accidently putting 6V on the coilring.

Anyway - I take it as just another T-experiense, gater 3 12V batteries and 2 sets of jumpstartcables and a compas and recharge them again. No big deal but I just wondered if this was what to expect.

As Norman mentioned, excess thrust face wear will reduce mag output regardless of magnet strength. Anything else that increases the gap between the magnets and coils beyond specifcation will do the same.

dykker5502 wrote: ↑

Sat Apr 20, 2024 5:50 pm

I'm perfectly aware of the if you do it reverse to the original orientation of the magnetism, it will tend to reverse the poles back. Can it be that I (and Don Lang) have done it reverse? Or is it just how it goes?

dykker5502 wrote: ↑

Sat Apr 20, 2024 5:50 pm

I'm perfectly aware of the if you do it reverse to the original orientation of the magnetism, it will tend to reverse the poles back. Can it be that I (and Don Lang) have done it reverse? Or is it just how it goes?

You can try to google this, and spend hours reading technical and scientific articles on the subject, like I did a few years ago. Or I can tell you what I found at that time. I found numerous articles claiming with certainty that the iron material will magnetize or re-magnetize into either polarity without regard to any previous polarity! Writer after writer was absolutely certain of that.
However.
My personal experience says otherwise.
About ten to fifteen years ago, I was putting together a nice T engine, and wanting a working magneto, I had a nice looking flywheel with all magnets and keepers intact in good condition. I went to recharge it as an assembly out of the engine, as I had done before. However, when I tried to determine its original polarity, I couldn't. That thing was the deadest flywheel magneto I ever saw! Magnetic compass, both my good one and an el-cheapo could not pick up a trace of magnetism anywhere on the thing! NOTHING! So I said okay, and flipped a coin. Set up my recharger (a checked out good working but bad insulation field coil that I had used successfully several times before!), did the three 12 volt battery zap it a few times, and got a weak recharge. Preferring to not try to flip it, I tried to hit it even harder a few more times. Still, very weak charge.
That was when I spent a couple hours one evening googling the subject to confirm what I remembered but didn't quite believe. Article after article claimed magnetism can and will easily be flipped, but I somehow didn't believe them.
So, the next day, I reversed my randomly chosen polarity, and hit it again with the batteries and field coil. One hit and the magnets were strong!
Of course I have no way of knowing for certain? However, the magnets refused to take a charge in one direction, and quickly accepted a charge in the other direction. And that from a point where they had almost completely demagnetized. Something in the molecular structuring must have been resisting one polarity while accepting the other.

No wonder I am so very cynical? All too often the experts have been wrong.

I charge my magnets individually and find that the polarity can be reversed without adverse affects. However, I often put the magnets through a demagnetizer first, but I don't know if it is necessary.

Art Mirtes