MTFCA Forum

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A long time Model T-er and I are going to attempt to re-magnetize my 1915 magneto without removing the engine by using a compass and three 12 volt batteries, ...or maybe the voltage from his welder. Has anyone done this before? Are there any pitfalls to watch out for? Thank you in advance for any advice you may be able to give us.
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There are pitfalls. Seek advice from someone who has experience at this before trying it. (I have curiosity, but no experience)

If using a welder, use the DC cycle.

Point the car East/West, take the plugs out and follow the directions. East/West so you know you are reading the magnets not earths magnetic field, the plugs out makes it easier for the engine to self align if off a little. KR Wilson would not have sold a magnet/battery charger for this if it was not Ok to do. Welder should work as long as it's on DC and lowest setting. AC will not work. I have done several in car recharges, both with battery and KR Wilson unit. One time I could not get a proper magnet reading, should have pulled the cover, I had to redo a couple of times. In the end it worked fine. When doing it with batteries; Keep them away from where you are working if you can. Last time I did battery recharge, I covered the batteries with a piece of plywood for just in case.

That method will work if done properly and if the coil insulation is in good condition. If the insulation is not good, you might get an arc weld of the windings which would cause the magneto to not work at all. A better way would be to remove the hogs head and charge the magnets individually while you rotate the flywheel. Just remember to check the polarity of the magnets and charge each one according to the correct polarity.
Norm

I successfully recharged my magnets in-car a few years ago. Some things I learned:

1. You can remove the spark plugs to make turn in the engine over easier. (You’re not fighting engine compression when lining up the magnets.) Also, disconnect the mag pickup wire from the post.
2. Getting a compass reading can be difficult on really weak magnets. You’ll need a decent compass (toy ones will just make you pull your hair out). Since you’re trying to get a N/S reading, parking the car E/W takes the Earth’s magnetic field out of the equation. I was able to get a better reading on the left side of the mag post. If you read N on the left, hook the + to the mag post. If you read N on the right, hook the - to the mag post.
3. Use the heaviest jumper cables you can find if using batteries. You’ll be pushing a lot of current through them.
4. Getting the magnets to line up perfectly was a challenge with just looking through the inspection cover and trying to get the brass bolts to be parallel to the ground. Get them as close as you can. Then, with the clutch in neutral, take a magnet reading to determine which pole you’re flashing on the mag post. Do one quick flash and this will pull the magnet directly in front of the coil. Set your brake lever forward to push the flywheel close to the coil ring and then make 4-5 more quick flashes.
5. DO NOT hold current to the ring, like some of the period instructions say. (They recommended doing this to burn out any shorts). You’re very likely to burn through your coil or weld the windings together. Just a succession of quick touches is all it takes.
6. As there is likely more of a gap between the lower half of the coil ring and the magnets than at the top, rotate your engine by quarter turns and repeat the charging procedure to get all of the magnets.
7. Most of the drawings you’ll see have you attach your lead to the mag post and flash to the hogshead. The jaws on my cables were too big to do that without also grounding to the block. I attached to the hogshead and flashed the mag post.
8. The hardest part is getting over your fear that you’re going to mess something up. I looked at it like my mag was already putting out lower voltage than my 6v battery. I had nothing to lose. If you accidentally flash the wrong polarity, just start over.
9. I did this job by myself, but it would have been significantly easier with at least one helper.

I hope that helps, and good luck.

I've done this several times on different Ts, all successful.
I would add to the above:

bolt something onto the mag post - a small ring spanner will do - so you can attach the croc clip. Then you can flash to the hog's head.

Take off the trans inspection cover. Then you can see the ends of the brass screws and ensure that they are symmetrically located each side of the centre line.

High gear, brake off, allows you to move the engine in either direction.

Yes. I did it in 2010 with tremendous success. Of course it is easier with the engine out and the hogshead off, which is the way I would advise it to be done. You can see my procedures at: www.mtfca.com/discus/messages/118802/159978.html. Jim Patrick

Recharging the magnets in the car works well, but if your magnets have not been removed, crack checked, new brass screws, field coil, etc the engine should be pulled and the magneto rebuilt. Brass screws fatigue and often break. The magnets like to break in two in the v. A magneto that has not been rebuilt is like having a bomb under your feet waiting to go off.

There is excellent directions in the back of the Dyke's Manual on how to charge the magnets in the car. Have done it many times. John

Steve, PLEASE PLEASE read the couple of posts by Tom Carnegie here on the Forum. Just search MTFCA on Google. The compass or the direction of your car is not important. You do have to have the flywheel in proper position! He gives some great advice on how to avoid disaster when striking the arc..
Tom has done a lot of research and testing on Model T magnetos. That's why he is a multi winner of the Montana 500! Take his advice and you'll have great success.
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Gene offers very solid advice. Following it will save time, labor, and angst. Nothing succeeds like success, and if you want a T that runs well, you could do far worse than take Tom Carnegie's advice on anything related to making a T run well. For those uninclined or unable to do the search:

http://www.mtfca.com/discus/messages/506218/528397.html

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Thanks Gene
Is this what you were referring to?

MTFCA Forum, By Tom Carnegie Spokane, WA on Thursday, March 26, 2015 - 01:48 am:

I don't understand all of that east-west compass stuff. The mag is dead. What little magnetism that is left is immaterial. Here is how I have been charging mags in the car for years with pretty much a 100% success rate.

1. Pull the transmission band door off so you can see the flywheel.

2. Turn the motor over until any two off the brass screws are in a line that is parallel to the ground. In other words the two screws are evenly spaced.

3. Remove the mag plug.

4. Procure a strong DC voltage source of 36 or more volts. Several batteries or a DC arc welder work well.

5. Put some tape around a punch or bolt or some such thing and hold it onto the mag terminal through the mag plug hole. The tape is to keep the bolt from shorting to the hogshead hole.

6. Make a connection to the bolt from the terminal of the power source.

7. With the other terminal of the power source, flash the chassis several times. I do eight flashes, just out of habit.

8. Reassemble and test.

If it doesn't take on the first try for some reason (usually operator error) retry.

Be very careful, especially on 26-7 T's to not short the terminal to anything, especially the gas tank. It is quite possible for an errant terminal to short onto the gas tank and pierce it and cause a fire. Also take any other precautions that one would need to take with sparks flying about.

I have even as an experiment flopped the polarity of my own T from a fully charged state. It worked just fine and has continued to work for many years since.

Folks, trust me on this, you don't need a compass at all. You never need to pull your hogshead to recharge the mag in the car.

This subject is covered in the MTFCA booklets.
I tried it without removing the hogshead and my results were not satisfactory. So I removed the hogshead and it worked much better for me.
Looking back with 20/20 hindsight I used the magneto connection. I notice that others suggest removing the connection and touching the solder on the magneto ring directly. I suspect that was my problem.
On the 1909 I restored each magnet when it was out of the car.

TonyB wrote: ↑

Tue Jun 29, 2021 12:06 pm

This subject is covered in the MTFCA booklets.
I tried it without removing the hogshead and my results were not satisfactory. So I removed the hogshead and it worked much better for me.
Looking back with 20/20 hindsight I used the magneto connection. I notice that others suggest removing the connection and touching the solder on the magneto ring directly. I suspect that was my problem.
On the 1909 I restored each magnet when it was out of the car.

The magnet alignment to each coil is CRITICAL. Visually positioning the magnet screw ends thru the inspection cover is key.
Best result I have seen was with a high output DC arc welder. 1 strike. 30 v output @ speed.

Yes Steve, Thanks for posting! Interestingly Tom has discovered that the N / S poles can be reversed and the magnet doesn't care which it was before charging! There were some that didn't believe this though.

One caution he warns is not to short out at the mag hole and kame your contact point away from the cover.

I have never seen anyone say what amp setting is used on a DC welder. If anyone has experience or know what setting they've used please post, I have a Miller 250A HF welder which seems like way to much if set too high?

OK I had a friend respond to me with some more info.

Make sure to remove the mag post... The spring and the small point of contact will suffer with the amount of current passing thru it! Second, use a bolt instead and carefully wrap insulating tape around it to prevent shorting out.

Use the max DC amp setting that you have but only strike or scratch to complete the circuit. Do Not hold in contact!!

One strike is good enough. Good Luck it works and so simple

Thanks Garrett

Gene, thank you. I’m going to try Tom’s method on my ‘14.
My pea brain just has one question. I’ve done the compass recharge method on other cars with great success (which doesn’t involve removing the mag plug). Isn’t Tom’s method just an easier and better way of locating the proper position? The 36 V flashing is still the same. If it worked on the compass method with the mag plug in, do you really need to remove the mag plug for Tom’s method?
No offense intended. I’m just not very mechanically inclined and trying to keep it as easy as possible.
Thanks Gene.

Do you really want to run that amperage through the mag contact? If it even survives, what do you suppose the voltage will be on the other side?

In Wyoming, we call those things "fuses"

Thanks Scott. That’s why people like me refer to people like you and Gene.
Appreciate the help!

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