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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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  #31  
Old 08-29-2018, 01:39:19 PM
Ronald E. McClellan Ronald E. McClellan is online now
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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
Boris Boris is offline
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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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  #35  
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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Old 08-31-2018, 01:55:22 PM
Ronald E. McClellan Ronald E. McClellan is online now
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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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  #37  
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 online now
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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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  #39  
Old 08-31-2018, 08:40:44 PM
Boris Boris is offline
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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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  #40  
Old 09-01-2018, 10:01:32 AM
Ronald E. McClellan Ronald E. McClellan is online now
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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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