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Magnetos, Ignition Coils and Spark Plugs Discussion about magnetos, buzz coils, spark plugs, ignitors and low tension coils.

Magnetos, Ignition Coils and Spark Plugs

Single Coil Magneto Magnet Charger


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  #21  
Old 08-28-2018, 01:56:58 AM
Jim Kennedy Jim Kennedy is offline
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Default Re: Single Coil Magneto Magnet Charger

Hi Landreo,
I would like to comment on the P.V.C. insulation being referred to as increased Air Gap. I built this transformer about 12 years ago. I used a 50HP 2 pole motor's lamination stack as the iron core "69kg's" being good silicon steel and I had it. I had a large amount of 2.5mm squared P.V.C. building wire which I wound 3 together in parallel, to achieve the primary winding which I got 1.4 volts per turn so then wound the secondary winding for this autotransformer. Although I wound to achieve about 630 volts which I wanted for another project, I put in plenty of taps where I needed joins and also I needed 415v which is what the 3 phase Line Voltage in Australia is.
Anyway I used a lot of wire, the more turns the longer the turn and also a lot of walking. I have loaded this to 6.5 kW, not much temp rise on winding, obviously the iron warms up. With my loose windings I don't think it makes any difference, they might be better cooled.
In transformer making the first consideration is enough iron mass for the required power then Iron selection and will the windows be large enough for the required voltage current and Wire size, so enameled magnet wire would need to be used.
This transformer has powered my own Phase Converter very successfully for the past 12 years.

Hi Boris,
Hope you don't mind my comments, but I also use building wire for transformers and can't see any problem other than you use more copper.

Jim
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  #22  
Old 08-28-2018, 08:25:37 AM
Peter Holmander Peter Holmander is offline
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Default Re: Single Coil Magneto Magnet Charger

This post has really taken off and that is why I enjoy the SMOKSTAK forums so much. I'm following this topic closely as I am hoping a cost effective design ends up materializing as a result of all the members collective input.

Back in 1989 when John Rex submitted his plans to Gas Engine Magazine for a 2 coil charger, he estimated the materials to cost between $200-$300. Well, here we are almost 30 yrs later and if I could purchase the materials for those numbers, I'd be starting a build tomorrow. Especially, the magnet wire $$$ requirements. Round stock for the core is not too bad, but the square stock has risen in price too.

I wish I was more schooled on the electrical mathematics and design end of it as I have studied a few interesting designs online, or mentioned here that could possibly be cheaper to build.

In my research for building a cheaper charger, I read where in the Model T Ford hobby chargers were being built using Chevrolet car starter windings by removing the armature, and installing a snug fitting iron core. Not sure if that would charge an engine magneto though. Maybe a bigger starter with a larger diameter core? Another poster touched on using multiple coils connecting them in parallel which is another avenue that could be explored. That design intrigues me as maybe some form of a large motor winding could be used. I'm sure someone here can comment on the feasibility of that design.

It would be really neat if someone came up with a design using readily available, reasonably priced surplus materials that worked well. Many of us would surely benefit from that.
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  #23  
Old 08-28-2018, 10:01:32 AM
Boris Boris is offline
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Default Re: Single Coil Magneto Magnet Charger

Thanks for all your comments.
One other point I would like to make about charger design is that one must consider the total circular path that the flux must take. Much has been commented about the small 1" core of this design but I have seen many chargers with 2-3" cores mounted between 1/4" steel plates, which considerably hinders the flux. The massive Rex charger is the only charger that I have seen that used armature plates that are as thick as the core. But then 3/8" holes are drilled in them for assembly. And the total path length of that charger is a good 16". My design is the only one that I have seen that uses armature pieces thicker then the core.
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  #24  
Old 08-28-2018, 01:23:07 PM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Single Coil Magneto Magnet Charger

IMO If it is worth doing , it is worth doing right! 2 1/2" core 1" poles , 4 1/2" to 5" long coil , 500' of magnet wire. Amazon has a 500' roll of 12 ga. enameled magnet wire listed for $102,54 . Use all 500'. Ron

Last edited by Ronald E. McClellan; 08-28-2018 at 01:52:26 PM.
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  #25  
Old 08-28-2018, 04:40:32 PM
Peter Holmander Peter Holmander is offline
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Default Re: Single Coil Magneto Magnet Charger

That's a great price for a 500 ft. roll Ron !
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  #26  
Old 08-28-2018, 05:38:52 PM
landreo landreo is offline
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Default Re: Single Coil Magneto Magnet Charger

Quote:
Originally Posted by Jim Kennedy View Post
Hi Landreo,
I would like to comment on the P.V.C. insulation being referred to as increased Air Gap. I built this transformer about 12 years ago. I used a 50HP 2 pole motor's lamination stack as the iron core "69kg's" being good silicon steel and I had it. I had a large amount of 2.5mm squared P.V.C. building wire which I wound 3 together in parallel, to achieve the primary winding which I got 1.4 volts per turn so then wound the secondary winding for this autotransformer. Although I wound to achieve about 630 volts which I wanted for another project, I put in plenty of taps where I needed joins and also I needed 415v which is what the 3 phase Line Voltage in Australia is.
Anyway I used a lot of wire, the more turns the longer the turn and also a lot of walking. I have loaded this to 6.5 kW, not much temp rise on winding, obviously the iron warms up. With my loose windings I don't think it makes any difference, they might be better cooled.
In transformer making the first consideration is enough iron mass for the required power then Iron selection and will the windows be large enough for the required voltage current and Wire size, so enameled magnet wire would need to be used.
This transformer has powered my own Phase Converter very successfully for the past 12 years.

Hi Boris,
Hope you don't mind my comments, but I also use building wire for transformers and can't see any problem other than you use more copper.

Jim
The problem is not will it work, of course you can use THHN wire instead of magnet wire. The problem is the packing or fill of the coil. You are going to have less effect for the same number of amp-turns because it is essentially a less dense coil fill or pack. You can add more turns but the question becomes how many more turns do you add? If you are shooting for 20,000 amp-turns with magnet wire how many amp-turns do you need for the same effect when using THHN wire? 20,001? 24,000? 30,000? That is the unknown.

I looked at the price of magnet wire compared to stranded THHN wire and the THHN wire is around 1/2 the price. If I build another charger I may use the THHN wire but I will have to find a conversion or do the math myself for the number of amp-turns I would need.

If someone knows of a conversion factor then that would be very useful.

Last edited by landreo; 08-28-2018 at 05:40:11 PM. Reason: amp-turns added
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  #27  
Old 08-29-2018, 02:21:46 AM
cobbadog cobbadog is offline
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Default Re: Single Coil Magneto Magnet Charger

G'day Jim,
Your charger would pull the earth off it's axis if you put it on full strength and Coopernook would end up being too close to Sydney for my liking. What a ripper but not quite portable.

I too am enjoying all the input that can only be constructive in helping us all come up with a good working design for our magneto charging process.

If I followed the design that Boris has kindly posted but wound on extra wire of the same type as used by Boris would this improve the strength of the charger or is there something in doing that, that it would not be beneficial?
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  #28  
Old 08-29-2018, 06:47:00 AM
Jim Kennedy Jim Kennedy is offline
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Default Re: Single Coil Magneto Magnet Charger

Hi Cobber,
I think you've got the dog by the tail, those pictures are of the transformer I
built for my phase converter. To change single phase 240v into 415v 3 phase. Here are some pictures.
Now, about increasing the turns on Boris's design, I can not be sure, maybe Boris experimented to get to the 160 turns, If not I would be continuing the turns until no more would physically fit. They can be easily removed if no improvement, and if you wanted to use shorter pieces of wire you can just strip the insulation a little and solder, don't worry about insulating the joint just keep winding.

Jim
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  #29  
Old 08-29-2018, 12:34:42 PM
Boris Boris is offline
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Default Re: Single Coil Magneto Magnet Charger

Charger design is all about compromise. Going from a 1" to 3" core would use 3 times the amount of wire per turn. For the same number of turns the current would only be 1/3 that of a 1" core. Going with more turns reduces the current even further.

I wrote a computer spreadsheet to calculate the result of various combinations of wire type and core size. It allowed me to find a "sweet spot" for what I thought would be a good design. For example, using 500ft of 12ga magnet wire on a 2.5 x 4.75" core, as Ronald suggested, would result in a charger with only 8000 amp-turns.

My frustration was not being able to find out a figure of when a core saturates given its size and material. That would be a big help in designing one.
If you would like me to calculate a design please let me know. Maybe we can come up with an ultimate charger design!
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  #30  
Old 08-29-2018, 12:39:55 PM
Boris Boris is offline
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Default Re: Single Coil Magneto Magnet Charger

Here are the spreadsheet calculations attached.
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File Type: pdf charger 12 ga 500ft 2.5x4.75 core.pdf (273.7 KB, 18 views)
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