MTFCA Forum

I have successfully recharged the magneto in a number of Model T's according to the procedure detailed in MTFCA Electrical System Book.

Looking at a tourer for a friend, with the compass located on the correct position of the hogs head it constantly points north even turning the flywheel there is never a south, there may be a "very" slight deflection east or west as the flywheel is slowly turned but its always predominantly north! I have tried another compass with same results. Even moved the orientation of the T!

I am puzzled by this, its as if the entire flywheel is magnetised, is that possible? If so how do I proceed, any thoughts appreciated. Thanks in advance. John (UK)

Your car is pointed east or west? Not north? If you read the last posts on the subject, It does not matter anyway, as long as the magnet ends are centered over a coil. Seeing brass screw ends thru the transmission cover etc.

The car must be parked with the front facing either east or west. If the car faces north, the compass will pick up on the north pole of the earth. If the magneto is not fully charged, the north pole might be overpowering the compass. Try turning the car and then see if the compass points to the magneto poles of the magnets.
Norm

Norm, Have you read and tried Tom's method? It works perfect and So Simple with no need for compass or parking direction!

I don't really understand why so many guys still feel the need to try and get the car pointed in the correct direction, figure where the compass is supposed to be and which way it points when a super simple method exists that is nearly fool proof?

John, if you scan back just a few posts you can read a very easy method to recharge your mag that has been researched and proven most effective by one of the most technical guys in the Model T world.

YMMV

Everyone is working so hard to make sure that they get the correct polarity when zapping the coils to magnetize the magnets. The question that I haven't found the answer to is how are the magnets arranged around the flywheel. Assume that you are putting magnets on a new flywheel where do you start with either North or South poles?

In some ways it doesn't matter, and others it does. Yes the magneto is an alternator as such it puts out A.C. Voltage. The output is a sign-wave of alternating voltage. You get a positive peak and then a negative peak and so on ...... Either peak should excite the coils and produce the required spark with a properly adjusted spark coil. Due to the fact that it is the voltage peaks that determine when the coil will fire, the position of the timer will determine which voltage peak is the one firing the coil. The timer determines the spark advance, but in increments of coil / magnet rotation, the first should be 4 degrees retarded and then 22.5 degrees to the next peak (18.5 degrees past Top Dead Center).

Thermionic Emission is a fancy way of saying the the electrons will jump more readily from the hot center conductor of the spark plug to ground than visa versa. It takes about 20% less voltage if the voltage is negative going to the spark plug. Hence I would hope that Ford arranged the magnets to provide negative to the plugs at normal operating speeds when the center conductor of the plug is hot, and the other peak (positive) when the plug is cold and Thermionic Emission doesn't make any difference.

Anyone out there have any answers???

Gene

I always wondered why the PO went to peel/stick stamps when for 100+ years previously, a simple dampening of the back of the stamp seemed to work so well.

I used to think it was for convenience.

Now I know better.

"Anyone out there have any answers???"

I don't have any answers, but i will offer a few observations:

There are two ways to align the magnets onto the flywheel in regard to polarity.
With one way the N poles are more or less in line with the dowel pins, the other, the S poles are so.
In regard to thermionic emission, one way would theoretically be better than the other. That is, assuming everything is consistent. (see below)
I took a survey of several dozen flywheels out of my pile, and they seemed to be random, i.e. roughly as many N configurations as S.
This doesn't mean that Henry didn't put the magnets on a certain way, but it seems to me that he did not.
As a practical matter, it would likely only be a consideration on a magneto that was just on the verge of being strong enough.
Now for a wrinkle in the situation. Some coils are wound with the polarity between the primary and secondary reversed.
So, it would be possible to have any number of coils producing a spark with the opposite polarity of the other coils.

The output is a sign-wave of alternating voltage.

No, the unloaded Model T Magneto output voltage more closely resembles a Triangular waveform with respect to time not a Sinusoidal waveform.
The Magneto output waveform is determined by the geometry of the fixed coils with respect to rotating rectangular pole pieces. The voltage output is minimum (0V) when the rotating pole pieces are centered over coil centers; Where the magnetic lines of flux are concentrated at the iron core and none cut the coil coil windings.
The Magneto output voltage is Maximum when the rotating pole pieces are evenly positioned between adjoining coils; Where the maximum magnetic lines of flux cut the maximum number of coil turns
The voltage polarity reverses as the pole piece magnetic polarity changes. The Magneto output voltage frequency is directly proportional to the flywheel rotational frequency with a factor of 8 (1 flywheel rotation produces 8 complete positive/negative cycles of Magneto voltage output; 8 positive and 8 negative). 16 voltage pulses per flywheel revolution in total.

I wonder if adapting modern, high-strength, lightweight magnets to the Ford flywheel magneto would be worthwhile... modern magnets and magneto coils that could provide more current at low speeds... with an electronic regulator that could provide constant, filtered, (nominal) 6 , 12, and 25 volts DC at up to 35 A and fully regulated 6V output for battery charging? That would allow use of an original 6 volt starter and starting battery, use of original 6 volt lighting equipment as well as 12 volt lighting and acessories. An 18-25 volt output would allow use of magneto type lights and horn. Modern magnets and windings could easily survive the flywheel housing environment in a Model T. It would also allow removing the original generator to save weight and reduce engine noise.

Pat: There was a forum post with pics some time ago that showed such a set-up. Cylindrical permanent magnets pressed into cavities in the face of (presumably aluminum) 'flywheel'. I haven't tried to find the article but I recall seeing it.

Sorry to hijack the recharging magmets subject. jb