Magneto Question

[Tim ford]

Hello. I’ve owned a 1927 Model T for 30 years. After driving for about 5 minutes I always switch it over to magneto and it always seemed to run better on magneto than on battery. The other day I took it for a ride and when I switched it to magneto the engine started breaking up and sounding like a misfire. Once I switched it back to battery it ran fine. Does anyone have thoughts what might be the problem? Your help would be appreciated. Thanks.

[rotorwrench]

Easy things first. You might pull the pick up out of the top of the flywheel housing and see if it is clean or not. From there it would be the wiring and switch. On battery, the coils work on the DC voltage supplied to the trembler coils. On magneto, the trembler coils function off the collapsing magnetic fields as each magneto magnet rotates passed it's own coil.

There could be internal problems with magnets or magneto coils but check the easy stuff first. The trembler coils should be OK since they are functioning on battery.

[J Franklin]

Weak magnets can be recharged in the car.

[Tim ford]

Thanks for your advice. I start with the easy things first.

[redmodelt]

The coils work on collapsing fields no matter the power supply be it AC or DC. The magneto generates AC current.

[rotorwrench]

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Where you have voltage you also have current so a magdyno actually does both since magnetic fields are constantly building and collapsing. AC current will provide induction without the need of pulsating direct current so it can be fed directly to the trembler coils. Induction can only happen with building and collapsing of the generated fields. Pulsating DC is a half wave current that is similar enough to AC sine waves to cause induction. The trembler coil doesn't have to buzz on AC but it does on DC. The added benefit of the magdyno is that it can also power headlights as long as the bulb can take the generated voltage. The model T Mag puts out near 28-volts if properly functioning. The headlight bulbs have to be wired in series with Mag power.

[redmodelt]

But the coils do fire approx. 2 and 1/2 times each time the roller makes contact with the timer segment on magneto. I said that the coil still requires the field to collapse each time it fires the plug.

[rotorwrench]

I put that out there to add to your statement for other folks that may have further questions on how the model T ignition redundant systems work. I don't disagree with the previous statements. There are enough magnets to make a few sine waves during the timer dwell period so they do make several high tension events during that dwell period for each succeeding cylinder during the four strokes of crankshaft travel while the engine is running.

I was curious about this stuff when I was younger and other folks may be too. Especially when something isn't working properly.