I have followed the procedures as per forum posts in the past for recharging the magneto without removing the engine in my '23 T Roadster. I placed the car East West and facing North, placed a compass adjacent to the mag terminal where indicated by diagrams from forum users.
The compass will only point South toward the front of the car at all six quadrants, in between the needle wanders around West, then returns to south when the motor is rotated slightly. Suggestions?? Thanks!
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 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.
Tom, does it matter which way the current moves (+ or - to the MAG)?
Steve, nope. One way the magnets will be charged with "north" poles in line with the dowel pins, the other with "south" aligned. It don't make a lick of difference on how the car runs whether you have a "north" or a "south" flywheel. I did a survey of my flywheels (perhaps 25 examples) and the polarity seems to be random.
Tom - I never understood that "compass thing" either! Seems like perfect placement of the compass on the hogshead is the critical thing there. Sure seems like your method is a lot more reliable.
You should consider writing that up and submitting for the magazine!
I successfully recharged my magnets in my '26 coupe in 2010 and they are still as strong as ever. Here is the post documenting the success. www.mtfca.com/discus/messages/118802/159978.html. When the magnets are dead or weak, the compass will not register through the hogshead, so in this case, it is best to remove the hogshead in order to find the N & S magnets. Good luck. Jim Patrick
I was using a 40 Amp/40 Volt golf cart battery charger to charge the magnets.
Things were looking positive, until the clamp slipped off the Mag terminal and put all the power in the transmission cover.
Then, wherever the compass was placed on pedal and all, the compass pointed north straight at the metal.
When the transmission cover was removed, there was just one small corner in front and outside the starter mounting that the compass would point South when near.
The common illustration that shows the compass position is in error. The arrow should point to the compass needle shaft and not the compass edge.
The larger the compass case, the larger the error will be when trying to charge the Magnets.
The purpose of the "compass thing" is to ensure you are recharging the magnets in the same magnetic orientation as they were originally charged.
Certainly the in car recharge will work, but recharging the magnets in the opposite direction from original with a less than optimum ampere turn source/distance is not a wise thing to do.
Ron the Coilman
Recharging the magnets with less than sufficient current in either polarity is a less than wise thing to do. With proper current it works just fine. I and others have done tests and changing the polarity of the magnets has no effect on either resulting magnet strength nor longevity of charge. See this thread by Robert Anderson where he reached the same conclusion.
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.
I started a thread on bad experiences with in car mag charging. So far I have yet to hear of one.
I used the compass method posted on the forum. My mag would put out 3 volts at high rpm. I used a military compass which easily indicated magnet position. I used 3 12v batteries in series, 36v. I also placed the make/break contact outside the car because of the gas tank location. Mag still works good after several years. PK
can you post a picture on how the brass screws should be, regarding line #2?
If the compass method don't work very well on the hog head, someone showed us an alternative last year by using the compass in the starter hole.
Here are the photos I saved. I think it was Toon Boer from the Netherlands who showed us.
Good luck and keep it safe.
John, I can't find a picture to explain what I mean. Here is a couple of drawings that I made that I hope explain it better. The dots represent the brass screws that you see with the band lid removed.
thank you tom!!
A new or properly rebuilt (individually saturation charged or recharged magnets) Model T magneto has the capability to produce over 200 Watts of power. But, the coils only requires a fraction of that power to work properly.
That is obtained by applying a saturation charging the magnets with many thousands (5-10K) of Ampere turns. That is not possible with the in car recharge unless you want to start a fire.
It is a known scientific fact that recharging magnets in the opposite magnetic orientation (especially with the lower power in car recharge) will result in a scrambled magnetic orientation that will have the long term tendency to crawl back on the hysteresis curve to its original orientation. Anyone telling you otherwise is peddling junk science.
The in car recharge method works if properly done, but it a marginal recharge method because of the lower Ampere turns used and attendant magneto gap.
You can find the original magnet orientation with a compass and get the best possible in car recharge results OR you can use the "trust me" method and attempt defying the basic laws of physics.
Your car and your choice, but I like doing things the best possible way.
Ron the Coilman
Where in the scientific literature did you find that it will result in a "scrambled magnetic orientation"? I went back and checked the magnet that I reversed charged, and after 100 days, with no keeper, it lost 3% of its charge, which is no different then any of the other magnets that I recharged.
By recharging the magnets in the car, is it necessary to turn the flywheel four times 90 degrees.
Thanks for your answer.
I have successfully used Tom's method (no compass) with 3, 12V batteries in series, and with a welder.
It sure beats pulling the trans and charging the magnets individually. It also beats fiddling with the compass.
I hold one terminal on the mag solder post and flash the other to the hogshead.
Tom, do you flash the mag with the brake lever forward or in neutral?
Assuming there is some magnetism left and the flywheel is free to rotate, what would happen if you didn't line up the magnets. Would the flywheel rotate to the proper position with the first flash?
Robb, I throw the lever forward.
I don't know, but I doubt that the flywheel would center itself if misaligned, I suppose that if your motor were loose enough and not in gear, it might.
Good question Robb, you always think things through just a little further than most people.
Seven years ago when I overhauled the engine in my 24 and before I had built a magnet charger I reassembled the magnets onto my flywheel and recharged by laying an old mag coil ring on them and zapping about three or four times with 36 volts from three batteries. It still runs and starts well on magneto. As Gary Tillstrom says about building a HCCT, (it ain't rocket science)KGB
I set up a real world in car recharging scenario and explained what can happen.
You changed the entire scenario with your bench magnet recharging conclusions and imply I am wrong.
I am talking about apples and your talking about oranges.
Ron the Coilman
Actually if you read the thread it was Tom who first challenged the notion of charging with respect to polarity. I don't believe it makes a difference if the magnets are free or installed on the flywheel. Tom thought my studies were pertinent to this discussion, and I continued it. No offense intended.
Perhaps the key here is that if the charging method brings the magnets to saturation or beyond, it dosent matter what polarity you recharge them to. But if you don't saturate the magnets during the recharge, which can easily happen with an in car recharge, the polarity may very well matter.
I see these posting on the forum and read them with interest. I'm not an engineer nor a metallurgist, however I've been known to have wound a few field coils. I have sent many cast iron cores to the scraper and currently have a pile that is in excess of three feet that are cracked. Most of the cracks are located at or in the area below number one and four bolt holds. I believe that in car charging causes that field coil to flex and possibly cracking the cast iron core. For those of you that have done this procedure you heard a bang, I believe that is the field coil drawing against the magnets. If that theory occurs you are driving a vehicle that has potential for a major disaster. 100 year old parts have probably exceeded the life span that Ford probably intended them to be. This may also apply to broken crankshafts (lugging) or broken drums (overheating by holding that pedal down). A job worth doing once is worth doing correctly.
When doing an in car recharge using 36 volts, have any of you ever checked what amperage was going into the field coil?
Talk slow, think fast.
Walter, I think you make a good point. Lot of difference in in car charging and laying an old coil right on top of the magnets. Those coils really heat up fast too at 36 volts. KGB
WAlly,You are 100% right.Bob Prouse and I always
had the engine apart when we charged the magnets.
WE used a compass and three 12 volt batteries in
series to do the job.
What Wally said intrigued me. I have never seen an engine fail as a result of a broken mag support. I've seen plenty fail because the copper came off of the ring, but never as a direct result of a broken mag ring. In fact, I don't believe that I have ever seen a cracked mag ring. But, they must exist because Wally has three feet of them. Estimating an inch a piece that would be around 36 cracked mag rings.
I decided to conduct an experiment. I went out into the shed and grabbed ten mag rings, all of the 1927 and older single stack kind, at random and magnafluxed them for cracks. None were cracked. I don't know how many rings Wally went through to find his 36 or so cracked ones, but I would guess thousands rather than hundreds. It would make sense that out of the ten I grabbed none would be cracked if Wally has handled thousands of rings. The percentage would be way lower than 10%. More like one tenth of one percent.
So, a cracked ring is very rare, but it happens. Why? If it is likely that in car charging is the culprit, I would surely stop advocating doing so.
OK, phase two of my experiment. I got a block and mounted a crank into it and bolted a mag ring onto the block and bolted a flywheel onto the crank and set the gap to .040" and locked the crank into that position with the main cap. I then took my welder and ascertained how much amperage was required to saturate the magnets. This I did by repeatedly applying current while checking a gauss meter. As the current is increased, the magnetic flux increases, to a point. At the point that the increase in current no longer increases the flux, you have reached saturation. On my welder this was about 200 amps. The mag ring I was using had 25 turns of copper, so the amp-turns were 5000.
I probably zapped the coil a dozen or so times determining the saturation point, so I magnafluxed the coil to check for cracks: none.
I then put a dial indicator onto the field coil to see how much it would flex. I needn't have bothered. It flexed the entire .040" gap. So, every time you apply a saturating current to a mag ring, you can expect that it will flex however much the gap is set to.
I then proceeded to zap the ring 100 times. After I had zapped it 100 times, I checked the temperature of the windings. They were not hot. In fact they weren't even warm to the touch. I magnafluxed the ring. No cracks. I then zapped it 100 more times. No cracks. I then zapped it 800 more times. At the end of each 100 zaps, I would check the temperature and check for cracks. After about 500 zaps, I could tell that the copper windings were above the room ambient temperature. They never got above what I would call "warm to the touch" even after 1000 zaps in a 15 or so minute period. No cracks developed. At that point I was satisfied that in car charging wasn't the cause of cracked mag rings.
What is the cause? I have no proof, but my gut reaction is that vibration from the magnets while the engine is running is the cause. I put a dial indicator onto the mag ring of my hand cranked coil tester. At hand crank speeds it flexes up to .003". My guess is that there are certain speeds where the mag ring hits a harmonic and flexes a good deal more than .003". I struck a few mag rings and they all produced a tone near Eb. Eb is around 200 cps. A T mag produces eight cycles per revolution. 1500 rpm is 25 rps. 25 times eight (cycles per revolution) is 200 cps at 1500 rpm. 1500 rpm in an average T is around 35 mph. My guess is that when driving your T at around 35 mph your mag ring is vibrating significantly. It is also doing it nearly a million times in every hour of driving.
I think the hundreds of millions of little flexes that a T mag ring is naturally subjected to in its lifetime is the cause of cracked mag rings, not dozens (or less) zaps with a 200 amp current source.
Very good exercise and report. There is nothing like the real world to confirm your already posted long term experience. That is 1000 zaps ahead of some unproven theory's on the issue.
I wonder since the the gap completely closes on the bottom when zapped if there would be any advantage in rotating the flywheel about 1/4 turn and repeating four times to take advantage of that direct contact.
It took years for Ford to succumb to in car charging, but when he finally did in the mid 20's the service bulletins give full details, 1/4 turns, 80amps and best results in their original polarity.
Isn't there a possible problem with in car charging and a spark in an oil chamber that may have gas fumes? I hate loud noises.
What do you mean by "...any two off the brass screws are in a line that is parallel to the ground. In other words the two screws are evenly spacedů."
Could you please post a photo?
Branden, Tom posted sketches and Robb Wolff posted a picture above showing correct positioning.
Tom, great test report. Tested practice trumps theoretical speculations
Roger, I second that! I especially liked Ton's vibration analysis. Sweet!
This brings up the question why some magnetos loose their factory charge and have to be recharged. I and others have shown that the magnets don't loose their charge over a relatively short period of time. So I suspect what might happen is that the magneto is momentary connected to 6 volts for some reason. If the charge polarity is reversed because the flywheel just happens to be in that position, could the factory charge be significantly degraded? If the flywheel is lined up for a same polarity charge, would this affect the charge? Perhaps an experiment would answer this theory (Tom?).
Robert, to my mind T magnets degrade one of two ways. Either by natural degradation, as Ron explained above (down the hysteresis curve) or they are impelled to degrade faster by a reverse charge (or some other external force). How fast a magnet degrades is a function of its charge and a quality of permanent magnets called "remanence" Remanence is exactly what it sounds like, it is how well a magnet "remembers" the charge it has received. The other part of the hysteresis curve is "coercivity". Coercivity is how easily a magnet can be recharged (or discharged from an opposite external flux). The remanence and coercivity are functions of the material the magnets are made of. An opposite charge such as a DC source applied to the field coil when the flywheel is in the "wrong" position, will tend to discharge the magnets. Eventually, depending on how much flux is getting to the magnets, it could charge them the other way. If the flywheel is in the "right" position, it would tend to charge the magnets.
Back in the olden days we had tape recorders. To maintain the quality of the recorders we had to periodically "de-gauss" the recording heads. What that involved was an AC electromagnet that you brought in proximity to the tape head and then slowly drew it away. The AC would sort of pound the magnetism back and forth hopefully hammering it back to zero. This is essentially what happens when you apply DC to the field coil when then engine is running. The magnets, because they are revolving see an AC magnetic field and in short order will lose most of their magnetism.
Jim, if you are saturating the magnets, there is no need to turn the flywheel 1/4 turns. Saturation is saturation. If you're not saturating the magnets, it likely would help.
"when *the* engine is running"
Not to put words in Jim's mouth, but what I was thinking as I read his post was that the mag ring might only be flexing and closing up that .040" gap at the bottom where it may tend to flex more and maybe that it doesn't flex enough at the top and sides to completely close the gap and therefore the magnets at the top and sides don't receive the same amount of charge as those at the bottom. Perhaps it does close the gap all the way around. I'm just not sure where you were measuring.
Hal, I was measuring at the top where the gap did not close.
I'm still confused. I thought you were saying that the gap DID close due to flexing of the mag ring when you shot the current to it. I, and I think Jim as well, were wondering whether the gap closed up all the way around. If so, then it is probably a good assumption that all magnets would receive the same charge. If it does NOT close up all the way around, then one could wonder if the magnets where there is still a gap would receive as much charge as those where the gap DID close all the way. Hence the 90 degree thing. Sorry if I'm just not understanding correctly.
I was assuming that the gap only closed on the bottom where there is less support. It would take a lot of force and flexing to close then gap on the top.
Sorry Hal, the gap only closes at the bottom. Where I checked the flux was at the top where the gap didn't close.
OK. So if I understand correctly, you are getting full saturation on all magnets, even though their was still a gap. That's good to know.
Excellent work on the topic backed up with actual test data. I am sure it required considerable time and effort to do. Thank you for sharing your findings with the forum.
It is frustrating when popular lore is frequently recited as reality without substantiating data.
Above I said this: "At the point that the increase in current no longer increases the flux, you have reached saturation." Then I said: "On my welder this was about 200 amps. The mag ring I was using had 25 turns of copper, so the amp-turns were 5000."
After thinking this through I don't think that is correct. I am pretty sure that my welder is a constant voltage type that increases the current by adjusting the width of a square wave pulse. So the amp values on the panel scale wouldn't correspond to a load that the welder was not calibrated for. So, when I get time I will try to ascertain the saturating current of a mag ring and flywheel with a straight DC power source (batteries). My guess is that it will be less than 80 amps.
My thanks too for your test data. Nice to know it will be a part of the forum and a good reference forever.