A Model T Ford owner (left) stops at a junk yard during the great depression to buy a few extra coils for his Model T. The junk yard owner is evaluating the coils.
The heart and soul of the Model T Ford is its ignition system. Very advanced for its day, it is widely misunderstood by many in the car hobby. Many do not comprehend how utterly reliable and trouble free the Model T ignition system is when it is properly serviced. Here we will examine the flywheel magnets and care for them properly during an engine service event.
The main component of a Model T magneto is what we would today call a variable frequency variable voltage permanent magnet alternator. The chart above was published by Ford to show what the typical magneto output should be in a Model T Ford. The output will be lower if the magnets are not fully charged. While the engine is apart the magnets can be charged.
Above we have bolted the flywheel to a workbench holding fixture to speed the job. A large slot head screwdriver is used to break loose the screws retaining the outer end of the magnets. A hammer is used to tap the screwdriver to make sure it is seated properly. The screwdriver has a square shank allowing easy turning of the peened over screws. Sometimes it is necessary to grind off the peened over ends of the brass screws first. In any case, the screws are thrown away and replaced by new ones.
Warning: Original Ford magneto screws and flywheels (or ring gears on later T’s) are tapped for #14-24 screws. Reproduction magneto screws are 1/4 – 24 thread, which is close but not the same. New screws in either thread are available from the T part sellers.
Safety wire is cut on the center row of bolts securing the inside of each magnet. I break them loose with a ratchet. Then they can be removed with a speed handle. The magnets are kept in order as they are removed, with the upper side staying upward. We take a moment with each magnet to inspect for cracks, then whack each magnet soundly against the vice to see if it is weak enough to break in half. You want any marginal magnets to fail now, not in the engine at driving speed!
Our flywheel is from a 1919 or later engine. It is being used with a 1915 engine. The ring gear looks absolutely perfect. It has been started for the past 30 years using a 12 volt battery and an unmodified T starter. It will last another 100 years we think. If the flywheel were from a 1918 or earlier Model T the screws thread into the flywheel itself, there is no ring gear and no provision for a starter on the earlier cars.
A magnet charger is made using one of our magnets clamped in the vice. I put a piece of 1 1/4″ ID Tygon tubing over each end of the magnet. Then I wrap 12 turns of # 10 AWG stranded wire around the Tygon tubing starting at the top of one magnet end, reversing the wire turns at the center of the magnet and continuing up the other side of the magnet with the same number of turns wound in the opposite direction. Some black duct tape is applied to the wire to secure it in place. Our low buck magnet charger is ready for action!
To see the operation take a look at this video from Strong’s Garage