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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 1x4" core.pdf (244.6 KB, 28 views)
File Type: pdf charger 12 ga 500ft 2.5x4.75 core.pdf (273.7 KB, 22 views)
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  #31  
Old 08-29-2018, 01:39:19 PM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Single Coil Magneto Magnet Charger

Boris I am not an electrical engineer and your figures are baffling. I checked my figures. The dimensions that I gave will give over 400 turns of 12 ga wire compared to your 160 turns. I guess that I am missing something. Ron
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  #32  
Old 08-29-2018, 03:30:57 PM
Boris Boris is offline
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Default Re: Single Coil Magneto Magnet Charger

Ron, sorry to be confusing. 160 turns is for my single 1 x 4" core using 65ft of wire.

If you look at my spreadsheet calculations on line 31, it shows one needs 11 layers of 509ft of wire for a total of 653 turns using 14.7 amps giving a N-I figure of 9618 (I misspoke with a figure of 8000 amp-turns before).

However, this was using a single 2.5 x 4.75 coil. If you make 2 coils with roughly 250 feet each, things look much better. Each coil would generate approx 10,000 amp-turns, (line 24) so if you connected them up in parallel to 12V and observed the polarity, I think they would add giving a total of about 20,000.

However...it would more then double the flux path length and I recall a formula somewhere that shows if you double the path length you will halve the strength. I will try to find that formula again and see if it is applicable in these situations.

Any electrical engineers out there???
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  #33  
Old 08-29-2018, 08:05:23 PM
landreo landreo is offline
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Default Re: Single Coil Magneto Magnet Charger

Boris,
It is great that you want to both look at and consider the theory behind charging magneto magnets. You cannot ignore the basic physics.

I divided my charger into around 5 coils on each pole. What looks like one coil on each pole is really 5 coils that are connected in parallel. That way you can have a lot of turns without the reduction in current due to the resistance of one long wire.

There are on line coil winding calculators that will give the turns and length of wire for a core diameter and length. Your use of THHN wire complicates that calculation slightly but you should still be able to use those calculators by using the real wire size including the insulation as the diameter of the wire. It is then just a matter of looking up the resistance of the calculated lengths of wire to determine the current expected with 12 volts.

There are charts online that will list the magnetic permeability of various metals. I found them years ago and I assume they are still out there. It does not hurt to double check my findings since this is from memory and research I did around 10 years ago.

The magneto magnet has no idea where the magnetic field is coming from, the field can come from an electromagnet but also you should get the same result from an appropriate size super magnet. That may actually be a less expensive way to go but does have some other less desirable features when compared to a large electromagnet.

Folks are free to make whatever they want with what ever size core and electromagnet but would benefit from having some real data posted to help in their designs. Building a large or small electromagnet is not the same as having a well designed magneto charger that will fully charge those magnets.
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  #34  
Old 08-30-2018, 10:39:09 AM
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Default Re: Single Coil Magneto Magnet Charger

Very intriguing design landreo. You have a 10 coil design vs my 1 coil design!

Correct me if I'm wrong but the total current going into your 5 coils in parallel gets divided equally so each coil gets 1/5 the total current. Is this the current value that you use in your N-I calculations?

I have posted our efforts to design a magneto charger to a magnetic engineering forum and they are currently scratching thier heads coming up with a basic equation or two that might be able to predict the performance of our various designs. I'll keep you informed.
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Old 08-31-2018, 08:51:29 AM
landreo landreo is offline
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Default Re: Single Coil Magneto Magnet Charger

I found the magnetics simulation program and will fool with it tonight. I knew finite element analysis was being used for magnetics but I was unaware this program existed. Good find. I am interested to determine if the often repeated 20,000 amp-turns is resonable.

You can use one long wire for a coil but that adds resistance which you can overcome by using a larger wire size or higher voltage. I wanted to use smaller easier to wind wire so I used several shorter coils. Your charger may have 5 layers with one long wire whereas I brought out the ends of each layer to form 5 individual coils. Each layer was a separate coil. Those coils were then connected in parallel so the resistance is low and the current relatively high. The amp-turns is just the number of turns of an individual layer, coil, multiplied by the current draw of that individual layer. The amp-turns of that layer is then multiplied by the number of layers to get the total.

One long wire or several individual wires? Both will work and each method has advantages, it depends on individual preference.

Hopefully some basic guidelines can be developed and posted so others can make a charger of their own design that will charge magnets to the level they need.
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  #36  
Old 08-31-2018, 01:55:22 PM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Single Coil Magneto Magnet Charger

As I said I am no EE When I try to measure the resistance of my windings I come up with 0 resistance. Also I have no way of measuring 100 amps. So my question. If using my suggested design and using a 12 V car battery , What would be the difference in the amp flow on the 500' of 12 ga wire compared to if I put an insulating disc in the middle of the coil and made 2 250' coils side by side wired in parallel? Another interesting thought , supposed one coil 250" were wrapped full length and the second coil 250' were wrapped on top of the first and wired in parallel. What we need is someone with the proper test equipment and lot of time on their hands to build the different designs to see which Is best. Ron
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Old 08-31-2018, 07:18:20 PM
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Default Re: Single Coil Magneto Magnet Charger

There are online calculators for the resistance of different wire sizes. 500 feet of 12 gauge wire will draw around 15 amps with a 12 volt battery. Each 250 foot coil will draw around 30 amps and two in parallel will be 60 amps. I made my charger with coils wound on top of each other. I do not know the magnetic difference between side by side and multiple coils on top of each other but I expect the difference would be small for direct current.

The same 500 feet of wire and what should be the same number of turns of wire will give two different amp-turns if wired as two parallel coils vs one large 500 foot coil. I do not know the size of your coil but assume 1000 turns total, I know that is likely a high number, for the 500 foot coil, with 15 amps, the amp-turns would be 15,000. If divided into two 250 foot parallel coils then each coil would be 500 turns at 30 amps or 15,000 amp-turns each for a total of 30,000 amp-turns since there are two 250 foot coils.

Last edited by landreo; 08-31-2018 at 07:19:29 PM. Reason: spelling
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  #38  
Old 08-31-2018, 07:57:28 PM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Single Coil Magneto Magnet Charger

Landreo That makes for an easy decision. It should be two coils wired in parallel. Ron
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Old 08-31-2018, 08:40:44 PM
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Default Re: Single Coil Magneto Magnet Charger

landreo, I studied your plan and it looks like you have a good idea! By wiring groups of coils in parallel, you increase the number of turns without reducing the current. The magnetic engineering forum guys use FEMM for thier computer sim. There initial run found that my 1" steel core was very near saturation. I'm hoping that going with a high puriety iron core will help that.

Ron, its easy to find the resistance of your wire. 12 guage solid wire is 0.0016 Ω/ft, so your 500 feet will have 0.8Ω, too small to be read by most meters. !2 v into that wire length will draw about 10A, not much. So yes, use landreo's plan of wiring groups of your coils in parallel. We nowadays have tons of current available to us, so use it.
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Old 09-01-2018, 10:01:32 AM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Single Coil Magneto Magnet Charger

Yes it looks like multiple coils are the way to go. It is very simple to make 2 , 3 , 4 , or 5 coils wrapped one on top of the other and wired in parallel. am now thinking 4 or 5 because it is so easy to do. I was just thinking of another way if making multiple coils (2 to 5) by starting all of the wires at once side by side and ending at the top with them side by side and wired in parallel. Altho handling that many at one time would be difficult. Also a wood base will work just fine. Ron

Last edited by Ronald E. McClellan; 09-01-2018 at 10:27:34 AM.
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