MTFCA Forum

The later mag rings have insulators like this under the coils. The only double stack mag ring I've inspected is the one I'm rebuilding, and it was done before, maybe fifty or sixty years ago. It didn't have them. Should I use these? What are they supposed to do? The coils are already insulated with tape and varnish, so why these?

Yes but not like you might be thinking. I just went down and looked at the 2 I have. When the pair of coils are assemble, there is a insulator placed under the bottom coil and one in between the two. Then each pair of coils are wrapped as unit, not individual coils, so the insulators are in the wrapped pair, not on the outside that I could see. If you didn't put the insulator between the coils at minimum, don't think it would work because they would be touching each other. For the bottom of the stack, think placing one under should work the same as in the wrapped package.

Steve: I haven't done double stack but I would use the washer if I were doing it, more as a cushion when coils are pressed against the back of the stator, PROVIDED the paper washer does not move the coil face too close to the magnets. I'm kinda a belt with braces guy when it comes to this. I'm sure Andre or Toon will have good advice here, they are experts.

Steve,
The insulating shield under each coil and the insulating between each single coil in the double coils are the most important.
The insulating shield between each single coil make the double coil working. If the insulation is no good the coil will make in the future an internal short and the loop will stop working.

The shield under each coil, between the coils and the coil frame, prevent a possible short of the coil to the frame.
Most of the time this short is due to debrit that is blocked at the coil out comming strip.
The photos are from a good looking coil ring that I tested as shown in the other post. During the test, in front of one coil the compass needle set parallel with the coil not pointing North or South. As soon as I shorted the coil ring (12V over the loop without the 21W light) at that coil a lot of smoke came with some flames.
The good looking coil loop was just good for a rebuild.
In that coil ring there were no washers between the coils and the frame.
On the photos you can see the "bad " coil and the damage.

So YES this shield is needed.
I make it out off 0.5mm gasket paper.
Snyder is selling them, I didn't use them jet ( made a few hunderds some time ago) but they will be part of my next order.

After assembled and tested the coil ring use a good coating to insulate it all from the oil and the engine debrit.

Good luck
Andre

Here is an other one without the shields.

Andre
Belgium

Insulation between coil halves: Yes, I have that. Each half of the double coil has a layer of Kapton™ so that when the two halves are joined they have two layers of insulation between them.

The only place current can go from one half to the other is where the inside ends are soldered together.

Each double coil is wrapped in ½" fiberglass tape and coated with clear insulating varnish.


I don't understand why the cardboard is needed between the coil and the flat surface of the ring and not around the core that's part of the ring, but I'll go ahead and install it. The cardboard isn't thick enough to put the coils past the ends of the cores. The coils will be safely out of the .025" to .040" mag gap.

I hope you'll all pardon my uninformed advice, given I've never rebuilt a coil ring. However, in my experience with other things electrical, my experience has been that more insulation is better than less insulation.

The paper insulating washers are insulating in two ways: As an insulator and also as a gap. There occasionally can be quite a bit of very fine metal suspended in T engine oil. That oil can wick into the coils and the paper spacers help to reduce leakage between coils and to ground. A pinhole in a very thin insulator is an easy path to ground, but a thicker insulator also provides a gap. It’s sort of a double “fail-safe”.

Put this in the I don't know but sounds good! Why no thick insulation around the inside; Could maybe have something to do with directing the transfer more to the post and not to the frame. Adding insulation under the coils might have been thought to be a barrier to the field build up in the frame, only the wrapping was used between the coils putting the coils in close proximity to the post for better transfer.

Question
Were the mag rings coated with some type or varnish, paint or anything that we know of before they were assembled at the factory?
Nowadays when rebuilding them it seems to me using some type of coating and or thin shield for insulation wouldn’t hurt a thing. And it wouldn’t make it to high over the pole.
The ones I’ve had rebuilt seem to have a coating under the coil winding.
The more the better it would seem to me. Why not.

I've only tried this once but I used two paper insulators, one on each side, inside the wraparound tape, not external.
First I cut an aluminum template and then made insulators in mass from a gasket roll. Eventually, they were covered in red varnish.

I used thin amphinol for insulators on mine. So far no problems with either of them for at least 20 years. I bought it at an electronics supply store.
Norm

Vern, how did you cut these? They look neater than mine.

Steve,
Found these pics to help refresh my memory.
I literally cut the aluminum template from scrap and ground the edge smooth.
Traced around it and cut with plain utility blade and cheap but sharp snips.

WARNING: DON'T DO IT!

Last night I received an email from a forum member who was kind enough to give me a heads-up on what I had done wrong. I'm posting it here because I don't want anybody to see what I did ignorantly and think it's a good idea:


I cannot overstate the fact that tinning butter is highly acidic and very difficult to properly clean and neutralize. Copper should all but tin itself and if it's clean a simple RMA no-clean flux should be all that is needed.

Tinning butter is meant to prep not-so-clean steel for the application of body solder which has a very wide plastic temp range and a very small liquid range.

Be really careful with the parts you have done and give serious thought to changing flux products.

Steve Jelf wrote: ↑

Sat Jan 09, 2021 11:53 am

WARNING: DON'T DO IT!

Last night I received an email from a forum member who was kind enough to give me a heads-up on what I had done wrong. I'm posting it here because I don't want anybody to see what I did ignorantly and think it's a good idea:


I cannot overstate the fact that tinning butter is highly acidic and very difficult to properly clean and neutralize. Copper should all but tin itself and if it's clean a simple RMA no-clean flux should be all that is needed.

Tinning butter is meant to prep not-so-clean steel for the application of body solder which has a very wide plastic temp range and a very small liquid range.

Be really careful with the parts you have done and give serious thought to changing flux products.

Steve,

Can you elaborate on what exactly "tinning butter" is? I have used rosin core solder, which is made for electrical connections, there is also acid core solder, which is NOT for electrical, there is the grease-like soldering paste which I use for soldered, non-electrical assemblies and there are the fluxes used for auto body work, like Ruby Red. Are any of the above considered tinning butter? BTW, I don't see where you ever stated what you used.

Can you elaborate on what exactly "tinning butter" is?

Here you go, Jerry.

I bought it to use with body solder and mistakenly figured it would be OK for soldering mag coils, not realizing that it's corrosive to copper. It's not OK for that, as our friend explains. I mentioned it here viewtopic.php?f=2&t=18219, and I'm glad I did, or I would have put the car together with that stuff eating away at those coils.

That stuff reminds me of the dangers of mixing ammonia and bleach.

Steve Jelf wrote: ↑

Sat Jan 09, 2021 2:38 pm

Can you elaborate on what exactly "tinning butter" is?

Here you go, Jerry.


IMG_5824 copy.JPG


IMG_5825 copy.JPG
I bought it to use with body solder and mistakenly figured it would be OK for soldering mag coils, not realizing that it's corrosive to copper. It's not OK for that, as our friend explains. I mentioned it here viewtopic.php?f=2&t=18219, and I'm glad I did, or I would have put the car together with that stuff eating away at those coils.

Thank you Steve!