I am looking for the best way to clean an old mag ring the insulation is all in good shape so I dont want to damage it or have something seep into the windings and cause a problem after it is clean what do you think about the spray insulation that the vendors sell? I plan to test the coil for any shorts to the metal frame I assume an ohms reading should show infinete resistance does the coil need to be load tested or is it good if the insulation is good and there is no short in the past I have bought rebuilts but this project has gone way over budget
thanks in advance
I put mine in boiling water with a generous amount of Oxi-clean and left it for about four hours, then rinsed with clean water and sun dried it.
Any good detergent would work. I have done several that way with good results.
I don't think you will be able to read a short to ground with an ohm meter. One end of the coil is already grounded. You could break that end loose, check to ground, then re-solder the grounded end.
I'd also be surprised if you could get it clean enough for anything to stick to it, but maybe you can.
I don't know why you would want to clean it, it will just be covered in used dirty motor oil in use anyway. There is probably no way to get it clean enough for any makeshift spray insulation to stick to it. You can check it electrically but there is no guarantee how long it will be good.
Then of course if you consider the amount of time and effort it takes to replace a defective mag ring, most folks would recommend not using anything but a fresh rebuilt mag ring.
RV Anderson sells an excellent field coil. His phone number is 716-267-3526. It would be a job to pull your motor again just to fix a bad field coil.
Occasionally you will find a good coilplate which has some damaged insulation, especially near the bendix slot. If the plate tests good, we have thoroughly washed it down and had the local electric motor re-winder dip it in his varnish bath and re-bake it. This re-insulates it and helps to keep the old insulation in place,
Hope this helps.
Allan from down under.
I am also a low budget Model T-er but trying to reuse the old coil ring is no option. It may be ok now but it will go wrong in the future.
With a few dollars you can easy rebuild the coil ring yourself without any shortcuts but you will need to take your time for it. I did it a few times for my projects and followed the MTFCA electric manual to do it.
First and most important is to strip it and clean it very well. During the cleaning you will find a few shorts you didn't find with your Ohm-meter.
To insulate the strips I use oil resistant masking tape. The new insulation discs are made of gasket paper. To finish the coils I wrap them with cotton strips. To turn the coils I use a self-made wooden tool. There are 8 left coils and 8 right coils. Each coil has 25 windings but you will be able to make only 24 winding but don't care your coil ring will work fine.
As all the coils are ready you have to clean the ring. There for I used in the past an old kitchen oven, not the one in the kitchen to make cookies, heat it up to 200°C and put the ring in for about 30 min. All the oil and dirt will come out. Leave it cool down in the oven and take the dirt off with thinner.
Glue with 2K glue first a paper disc than the coils, pay attention to alternate the coils, left right to make the north south.
After testing and soldering all together I use polyester resin to finish the ring.
Before soldering and glueing I put the loop together and test it with a 21W 12V lamp, a 12V battery and a compass to see the alternating north south of the loop.
(Message edited by adminchris on December 30, 2014)
I made that mistake in 1997 when I rebuilt the engine in my '15. The original coil ring looked great, and had worked fine. I put it back in the new rebuilt engine.
During the 2006 All Ohio Tour the mag quit working when a connection came open in the coil ring. So I had to finish the last four days on battery.
There's no reason to paint over an old coil ring. If you are going to re - use it just put it back in. Personally I think you are making a mistake by not rebuilding it while the engine is out.
Thank you for an excellent description and many photos of mag ring reconstruction. I copied and placed your information inside my mtfca electrical system guidebook as reference material.
Andre, do you stretch the copper strips to make up for damaged material cut from the ends of old coils? If so, how much do you stretch the 3.5 meter long strip without it breaking?
It appears you have a removable wood disc on the core of your winding fixture, I assume that is used to assist in pushing the completed coil off the mandrel?
Many thanks for you comments,
To stretch and clean the strips I use a flat piece of plywood and the tool you see on one of the photos.
You put the strip flat on the plywood and the tool straight on the strip than you pull slowly the strip under the tool. (don't know the name of the tool)
The first time you will take off all the mess and dirt from the strip, the second and 3rd time you will see the strip getting straight.
I only once broke a strip and replace it with a coil from a loop that was to far gone.
If a strip have some damage it mostly can be straight up with a little hammer and a body work iron.
The removable wood disc is as you said, it assist in pushing the completed coil off the mandrel. I also use it to keep the left turn coils in its place during the wind up.
the strips you see are for a new challenge; an oval double stack.
(Message edited by adminchris on December 30, 2014)
I agree wholeheartedly with Andre. I have rebuilt 3 coil rings using the method he posted. They work very well and for over 14 years have had no problems. The magneto is hard to get to so when the engine is out it is well worthwhile to replace or rewind the coils. Andre did an excellent job of posting the pictures and giving the description of how to do it.
Thank you, Andre.