Model T Ford Forum:
By Terry Horlick in Penn Valley, CA on Saturday, April 16, 2016 - 07:29 pm:
I have been doing a bit of work on my 1927 T. I pulled the engine due to low compression expecting to lap valves and change rings. Along the way I found wear and problems with the triple gear bushings and wear on the low speed drum gear. So a complete transmission rebuild is under way.
This has taken a long time as I have been building a machine to dynamically balance the drums, crankshaft and flywheel.
Today I decided to have a bit of fun. Rusty ran well on mag, but I did my usual mag test: With the flywheel on the bench I put a mag ring in contact with the magnet keepers and tried to remove it. All it takes is pressure from a few fingers.
So next I set up the AC/DC welder. I set up to run it on DC 180 amps. That is a nice 50 VDC source.
About 10 years ago I posted a web page on how to do this, so this time I will be brief. Using a compass I verified that I will be charging it up with all magnets getting the same polarity they presented with... careful not to reverse polarity. I do this by magnetizing a nail to verify the polarity.
Next I set the mag (note: an old one which cannot be used in a car without re-winding) on the flywheel and attached the negative cable to the field coil frame. I then attached a wire to the Copper ribbon (which used to go to the mag post contact ... this is where the old mag is broken, you can just use the solder button on a better mag). Then I put a piece of wire in the other lead.
Turn the welder on and you're ready to go. Just tap the wire against the lead to make a spark and as fast as possible release. Repeat... all you need is to do it about 3 times.
I figure if a little is good a little more is better. I flash it about 10 - 15 times getting probably only a few microseconds each time. After 10 - 20 hits everything is still cool to the touch. After this you are done, but just to be sure all magnets are getting hit pretty equally, I turn the mag 2 magnets and repeat the above. Then I turn it again.
Now the test is done again. I try to remove it with my fingers.... Nope can't do that! (Of course I know that already because I tested after the first 3 flashes and of course I had to lift the mag off to rotate it). The only way I can get the charging mag off of the flywheel is with a pry bar.
The magneto is good for another 15 years minimum. I'll be 80 years old then, we'll see if I'm still rebuilding the old guy then!
Yes I know it is good to pull the magnets off and try to break them to be sure you have no cracks. But in this case I just did that about 15 years ago and everything looked good and all the magnets pulled on a wrench equally before and after the charge. So I am going to chance it to save having to re-attach and re-level the magnets.