I pulled the transmission and magneto field coil ring from my '23 engine. I have been pleasantly surprised by the overall condition of this car.
The magneto field coil is amazingly good ... no rust and all the coils tightly wrapped ... and I'm thinking it must have been replaced maybe in the 1960s. I cleaned off the old oil with a brush and gasoline and was trying to remove what I thought was hardened oil, but discovered that it was actually an even layer of that reddish electrical varnish. When I allowed the gas to dry ... I found that the entire casting was coated and the windings are firm and also well coated.
So, should I simply use this as is. Was going to have a newly re wrapped one ... but I think this is very sturdy. How should I test it to make sure it's electronically sound.
There are three things which can happen. One is a ground between the coil and the casting The other is a short between windings of the same coil. The other is open connection. The only ones you can check easily would be the ground and open. To do this, unsolder the grounded end of the coil, near the top next to the post. Then take an ohm meter and test from the coil to the casting. It is unlikely that the coil would go open, but you can test for open by putting one probe on the contact and the other on the end which you unsoldered. To test for short between the coils on one winding would be almost impossible to find due to the low resistance of the windings.
Unfortunately, washing with solvent and a brush could damage the insulation, but if it is undamaged, probably still good. You can put it together and be sure to get the gap between the magnets and the posts between 25 and 40 thousandths. You might get lucky and find the magneto is still good, however to replace it after your car is assembled, would require removing the engine and transmission.
It would be a good idea to at least recharge the magnets before you put everything together.
The windings are in perfect shape (no loose or frayed areas) and the protective varnish coating seems undamaged. I went very lightly with the solvent cleaning. I guess I could save this one for the HCCT I'm building and buy a rebuilt one just to be sure. But if I can save $200 it will help me with other areas that need work. On the other hand ... hate to have to pull the engine after getting it all together if there is a problem.
I had planned to recharge the magnets using the technique where you lay the coil ring on the magnets and zap the ring with a battery charger as shown on a popular you tube video.
Mark, Using a coil ring to charge magnets can give you a functional magneto. However the magnet charge is not as strong as charging the magnets individually by other methods which will improve magneto output. I'll probably catch some flak for this post, but that is just my observation.
The other is open connection. What Norm. Is that like an empty Load.
There was a time when I didn't think much of pulling the engine out of the car for a tear-down. Nowadays, I think driving is more fun than pulling wrenches, and I''d as soon take a good beating as have to do that repeatedly. Make sure everything is 100% while you have it down !
But to charge the magnets individually will require dismantling the flywheel completely. What a rabbit hole that is. I never did any recharging on my 1919 (non starter) T and it ran on both mag and battery for over 35 years. Also started on mag.
I suspect I will only need to start on battery and switch over to mag with this '23. The magnets are pretty strong now. I thought I could get away with charging the set by the coil ring method. Is this type of charging prone to becoming weak faster than individual magnet charging?
Rabbit hole or not. it is worth it to find out if you have this situation.
Yes, I see your point. It's the stuff that could keep you up at nights. But how do you actually know if you have cracked magnets. Can you magneflux magnets ... or are you only discovering ones that are actually broken in two when you take your flywheel completely apart?
Take a magnet and hold it loosely by the narrow end and bang one of the legs against something solid (Anvil, workbench, shop floor) and see if rings like a tuning fork or if it comes into two pieces. If it came into two pieces, it wasn't any good to start with so no loss.
I've checked a coil ring for grounded coils by hooking up a D-cell flashlight battery to the coil ring. One side to ground and the other to the solder pile that the mag post contacts when it is in the car. Take a hacksaw blade and check each coil for magnetism starting with the one that is attached to the solder pile. If they all attract the hacksaw blade, none are grounded. If you get to one that doesn't have magnetism, you just found one shorted to ground. None of the others downstream of it toward the grounded end will have any magnetism either. If they all have magnetism, you can sort of get an idea if there are any layer to layer shorts by the strength of the magnetism. Of course that last part is rather subjective, but if they all feel about the same, you are probably alright.
Bear in mind that what you are doing is a direct short on that flashlight battery so work quickly and don't overheat anything. I'm sure some will not like this idea, but I'm just telling you what worked for me.
BTW, If it's really as good as you say and it checks OK, I would probably use it, but that's just me. I'm a hardheaded son of a gun and I'd be willing to take the risk.
On the other end of the spectrum is rewinding my own. I did that once for my HCCT. It worked just fine for about a year then all of a sudden it didn't. Pulled the mag ring and checked it and had a grounded coil. Guess it rubbed through the insulation. This was my first rewind and with that experience, I decided it would be my last and was glad it wasn't in a car. Others have had great success at it.
Ok ... so now I am paranoid about the magnets on my flywheel. Looks like I'm into a much larger project than I expected if I'm removing all the magnets, testing and reassembling. If I'm going to do that .. might as well buy a newly rewound coil ring too. I don't want to putz with removing the engine again once I put it back into the car. Just want to drive it.
I sent my magnets to a well known forum member to have them recharged. He found a cracked one, but had some spares, so he sent me a full set back, asking that I just replace the one he "Loaned" me. So next time I was at a swap meet, I found a guy who was selling magnets. I asked him if I could bang one against something to check for cracks. He said "yes". The first one I tried broke in two.