Coil winder

doc1955 · Jan 26, 2019

Well started winding my first coil I wound the primary which went pretty good and started on secondary (12,500 wraps).
I've got a plan for the vacuum chamber in mind and going to start as soon as I get the first one wound up. The wider that I built is working well.

tornitore45 · Jan 27, 2019

Hats off to anyone tackling a 12,500 turns winding with a hair sized wire.
My experience with HV suggest to use a multi section bobbin to lover the gradient.

doc1955 · Jan 31, 2019

Well did get my first coil done AND IT WORKS. I now need to incase it I'm planning on a box a smaller version of a model T coil. Here is a pic I took from the video.

Ghosty · Jan 31, 2019

Doc, it looks good, this is what I use as a vacuum chamber, made from a glass dome from an old outdoor weather proof light fitting. Made the base of some alloy plate, with a rubber seal glued to it.
I have an old Robinair vacuum pump to run it.
Cheers
Andrew

doc1955 · Jan 31, 2019

How do you keep a constant temp? With the process I'm doing I have to hold a temp between 185F to 205F depending on the vacuum pulled.

Ghosty · Jan 31, 2019

I use it to pull the lacquer into the coil and than bake separate. You could set the whole thing in an old oven to keep the temp.

doc1955 · Jan 31, 2019

I don't think the wife would allow that LOL. Plus the temp boils off any moisture the reason for trying to get wax sucked in mainly to keep out moisture.

Ghosty · Jan 31, 2019

Doc, put a glass of cold water under vacuum and see what happens, moisture is not a problem.

Ghosty · Jan 31, 2019

doc1955 said:
I don't think the wife would allow that LOL. Plus the temp boils off any moisture the reason for trying to get wax sucked in mainly to keep out moisture.

I did say old oven, not the good wifes one

doc1955 · Feb 1, 2019

Yes you did but I would have to use hers and that would go over like a lead balloon LOL
The crock pot actually worked great for what I wanted and now that I have that setup thats the route I'm taken the only thing I might change is get a longer hose for the pump.
I'm going to wind another coil and shoot for 3 to 4 volt and see if I can get it that low and work ok.

WOB · Feb 1, 2019

You are overthinking the vacuum chamber. A simple Mason style canning jar with a hose barb in the lid makes a perfectly good one. If you need temp control, simply immerse the jar in a water bath.

WOB

doc1955 · Feb 1, 2019

Yes I do that some times LOL. But I have it all set now.
Thing is with a jar I would like to know the vacuum value and to get a gauge on it it would have to be a small gauge or a hose to a gauge.

barryc · Feb 1, 2019

When I used to wind HV coils for vehicle Capacitor Discharge electronic ignitions units back in the 60's, I'd immerse the coils in a jar of lacquer then put it into a depressurisation chamber. (The chambers were used to calibrate altimeters - I was in the RAF at the time - so they were pretty handy!) The reason for employing a vacuum is to remove all the air from between the windings to prevent movement ("singing") of the coils during use. It has nothing whatsoever to do with moisture!

doc1955 · Feb 1, 2019

That might be but I am going by the book Bob Shores and he sounds like he was a much smarter individual than I when it comes to mags and coils. So that is what I was going by it is a very interesting book that he wrote and I did learn a lot by reading it like figuring out the length of wire needed to obtain the resistance of a primary winding. Before I read the book I had no clue.

tornitore45 · Feb 1, 2019

The vacuum is pulled to remove the air so the varnish can reach every place trapped air would impede the impregnation. At that level of vacuum moisture boils off and leaves with the air. If any air is left a corona discharge takes effect, not a spark just corona. Corona is ionizing and leads to early failure, then you get a real spark inside.
To test for presence of corona we used to connect the shorted secondary to the HiPot AC 60Hz and the secondary to the HyPot return by means of a 1kohm resistor. Then we look at the V across the resistor with a scope. The 60 Hz is hardly visible but the presence of corona is indicated by high frequency burst appearing on the top of the 60Hz crests. If you see that the coil or transformer is going to fail prematurely in continuous use. A model engine coil may not fail during the few hour the engine is run if that is how long one runs his engines.

dsage · Feb 2, 2019

Tomitore45 - You wrote:
To test for presence of corona we used to connect the shorted secondary to the HiPot AC 60Hz and the secondary to the HyPot return by means of a 1kohm resistor. Then we look at the V across the resistor with a scope. The 60 Hz is hardly visible but the presence of corona is indicated by high frequency burst appearing on the top of the 60Hz crests.
Was there a typo in there? I'm not understanding that setup. You said you shorted the secondary and connected it to the Hipot tester than you also connected the secondary to the Hipot tester. I'm confused. I'd like to try this test. Could you elaborate.

tornitore45 · Feb 2, 2019

My bad. The second word "secondary" should read "Primary".
In other words the HyPot is connected BETWEEN primary and secondary to stress the insulation between them. With this method there is no stress between layers of the secondary, to do this would require a HF induced voltage.
The idea is that if one does not detect corona in the insulation between primary and secondary there is good hope that the varnish has penetrated the secondary as well.

mohavegun · Feb 2, 2019

Made my vacuum chamber as a "bell Jar" using a sheet of rubber mounted on an aluminum plate. I bought a large clear glass bowl like one would use in the kitchen. A hose barb was fitted through the bottom of the aluminum and rubber plate and hooked to my vacuum pump receiver. ( I use a receiver to build a vacuum reserve) It works very well for degassing investment plaster used for lost wax castings and would be perfect for the coil builder as well. The spherical shape of the heavy bowl is safe enough to support the vacuum. Will send some pics later.

doc1955 · Feb 14, 2019

Here are some pics of the finished coil. It puts out a nice spark at 6V. The primary resistance is 3.0 ohm and the secondary is at 5600 ohms. I'm happy with the way it turned out one more thing I can cross off my would like to build if I could.

mayhugh1 · Feb 14, 2019

Your photos didn't show up here, but I found them on the other forum. Interesting project and nice final result. I noticed your comment about wanting to rebuild a Model Z buzz box. While watching some of your videos I bumped into one by a guy who showed how he rebuilds the 100 year old Model T boxes. He claims the most common failure is the internal capacitor, and shows where it's at under the tar and how he digs it out. There is also a glass separator plate that has to come out to accommodate the size of a modern replacement cap. I can't begin to recount the number of high voltage projects I built around those boxes when I was in junior high school. Even today the smell of ozone brings back fond memories of those days. - Terry

Coil winder

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