I'm going through my motor. (started with rod bearings getting beat up, but I'm a bit afraid where this is headed . . .) I discovered some mag coils with the wrapped insulation broken/missing. The mag works fine, but this doesn't look particularly good. The insulating "tape" seems pretty dried and brittle. I guess my options are:
1) Ignore it, hope for the best, and put it back together.
2) Figure out an appropriate insulating material and re-wrap the coils.
3) But a rebuilt mag ring - looks to be about $200.
thoughts and advice?
With the wrapping coming off, it could and does end up in your oil line and that will cost you more than $200.00.
http://www.ebay.com/itm/1922-1927-ford-model-t-mag-field-coil-ring/151576070705? _trksid=p2045573.c100033.m2042&_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1 %26asc%3D28797%26meid%3De23b9d9d840c465b9d7b11c52b32fcb5%26pid%3D100033%26rk%3D1 %26rkt%3D4%26mehot%3Dlo%26sd%3D151576070705
We have had success using old mag coils. We degrease them as best we can using mineral spirits. We then dry them well and paint the coils with a few coats of Gylptal insulating varnish, available from Eastwood. Your coil is damaged in the usual area by people trying to remove the starter without removing the drive first. If your mag was functional I would reuse it. Opinions will vary, but we have had no trouble the ones we have patched up. A rewound unit from Total Recoil is the best approach, of course. All it takes is money. Model T's respond well to budget repairs. Go for it.
I've done the repair and the replacement. My '15 has a ring in it that I repaired about 20 years ago in the manner Erik described and it has no problems; of course we could get better (more toxic) cleaners at that time for the degreasing. I was on a tight budget and cleaned and coated it carefully, then tested it before installing. I will install a rebuilt the next time the engine is out because the dollars a little looser, but the repair worked absolutely fine. The most important thing is to clean it very well! When you think it's good enough clean it more....
Chris, you can easily rebuild it yourself watch:
I am most certainly an advocate for doing things yourself, but after rewinding one mag coil, I swore I would never do that again. Luckily, it was for a HCCT and when the failure (grounded coil) occurred, it was easily remedied, but it just reinforced my thoughts on the matter. I'd hate to think I would have had to pull the engine because of my mistake.
As for using an old one.....I would NEVER do that. Yeah, $200 sounds like a lot of money, but as someone else on here says, it only hurts once.
The mag was definitely working but I'm concerned that if I take the degrease/varnish approach, it may not stop the dried up wrapping from breaking off more in the future. I probably don't need to rewind the copper, but I probably should rewrap the coils. Even that seems like a fair amount of work. What is the material used for that wrap?
I probably should just suck it up and spend the $200. I do like doing things myself, but there are plenty of other tasks to keep me bus. On the other hand, I'm a little concerned about how the $$$ total is going to add up as I go through this motor.
The material used for warping the coils are cotton strips. They are about 1m long and 15mm wide. Just re-warping the coils will not work.
In the photos you show the two coils are damaged. On by trying to take out the starter with the bendix on it and one with debris that went by in the passed.
These coils will not work properly because of the probability of shorts between the winding.
You need to replace it or to rebuild without any short cuts. I know I was there once.
Each wrap has to be insulated from each other. Either by a coating on the wire like electric motors or by wrapping with some sort of insulating "tape" between each layer. If two adjacent layers touch, you probably wouldn't notice, but if they are all touching, like you just took raw copper and wound it, the coil would not work. If any one coil shorts to ground none of the others from that one on to the last one will work. In other words, if the last coil in the series were to short to ground, you would only see a minor decrease in mag voltage, but if the first one in the series were to short to ground, you would have practically NO output.
That coil needs to be rewound! No way would I or most any other T guy try to reuse that. The only question is whether to pay someone else to do it, or read up on how to do it yourself. Trying to reuse that coil is false economy.
OK, I get it! :-) I'm an electrical engineer so I understand the theory. Thing is, this motor hasn't had a starter in it for a while, so this is old damage, and the mag works just fine. But I agree - it doesn't make any sense to put it back together like this. So it goes on the list of things I need to deal with.
Can one coil be replaced or repaired?
It looks to me that you can pull out the damaged coil and replace it with a good one. It would be cheaper too.
I have not found anyone that sell individual coils
Years ago when before I had much money to spend on a complete engine rebuild on my 24 T the mag coil had brittle and ragged insulation. I didn't know of anyone that rewound and reinsulated the mag ring.
Someone had told me to remove all the brittle insulation and degrease the mag ring as much as possible and use electric motor spray on insulating varnish or whatever it was.
I rechecked the mag ring with a flashlight continuity checker and didn't find any shorts.
I then put everything back together and the magneto still worked.
I wouldn't do it again now that I know where to buy a nice rebuilt unit but maybe I got lucky when I didn't know any better!
Just send it to Wally. He does great work. Where it is located you don't want to have to go back in if you have a problem. http://totalrecoil.webs.com/
On a related topic, I'm trying to build a magnet recharger & would like to use a capacitor discharge unit to "zap" the thing... do you have any ideas on what to make up?
My previous setup was simply an armature growler (rated at 160watts) that had a bridge rectifier and a momentary switch. It worked well enough but after a few too many magnets the heat buildup killed it.
I now have a larger 240/100volt transformer, with a section of the core removed to make a gap. Can't remember the rough electrical specs but I was going to connect the .060" secondary & .090" primary windings in parallel.
I was thinking a heap of 20uf motor starting capacitors charged from line voltage (240v) dumped via a contactor thru the windings, with a diode to clamp any secondary oscilations/back emf...
What do you think?
I have read some where that for manufacturing magnets, it is used condenser. This is in order to get the maximum of current even in a very short time. You don't need a long time to charge a magnet, just enough to reach the maximum of current.
I think you need a much bigger condenser than 20 µf and 240 v won't help. You also need a condenser than would accept to be short circuited without damage.
Maybe one of these condenser used for high level music for car can do, there are 1 0000 000 µf or more for 12 v only. If you put a diode in the charging circuit, since you are looking for getting a very high current, it should be a very big Diode.
The electrical book from the MTFCA describes how to rewind the coils and rebuild the mag ring. I have done about 5 of them. None of them have failed so far. If you value your time at somewhere above $2.00 an hour it is better to buy one from Wally. Just my .02
I meant a group of capacitors in parallel, total capacitance in the order of 500 or 1000uf...?