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Mag Charger windings, expert advice please


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  #1  
Old 04-05-2005, 01:18:00 AM
Kevin O. Pulver Kevin O. Pulver is offline
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Default Mag Charger windings, expert advice please

#1
I've got John Rex magneto charger plans from GEM, and another plan off the web. In winding the coils:
One plan uses more turns of lighter wire, at less amps.
The other plan uses less turns of heavier wire, but more amps.
Both plans have similiar power rating.

If "amp turns" equals number of turns X amps, how critical is wire guage as long as I get the approximately 20,000 amp turns I need?
I'm not trying to skimp on wire, but am having trouble finding a good price on 10 guage and was wondering if the 18 guage the other showed would be OK or is any other combination "best"?

(1b) Is the above answer related to whether I use a battery or AC current with a rectifier to end up with DC?
#2
Johns shows a 3" winding core compared to the 1" in the web plans.
I'm assuming bigger is better up to a point.
#3
John uses C1018 steel for the winding cores. Is that just "soft steel"?
I mean if it's not spring steel or some other hard thing will I be OK.
I was going to try the junkyard for scraps and might not know what it is.

I know some of you are really sharp on this and can clarify the issue for myself and others.
Thanks in advance.
Weakwebster Kevin
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  #2  
Old 04-05-2005, 08:50:41 AM
George Andreasen George Andreasen is offline
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Thumbs up Re: Mag Charger windings, expert advice please

Kevin,
I built a charger using Gingery's plans and faced the same "burning questions" as you. Here's what I discovered....
After you suffer from brain fade and worry about the math, here's what it boils down to: use sufficient size wire and a lot of turns. I managed to find 17 guage wire as called for but would resort to 16 ga. if necessary. When in doubt always lean toward heavier wire and lots of it. 10 gauge is awfully heavy and 18 sounds pretty light to me. It doesn't have to be magnet wire. Regular plastic insulation is fine...your coils will just be bigger.
My cores are just mild steel (2" diameter). You're not trying to permanently magnetize them, so exotic metal simply isn't necessary.
When hooking up the two coils, direction is important. Leave enough wire so you can change your connections if the charger seems weak. If the neigbor's car gets sucked into your shop, the connections are correct!
This is a basic electromagnet, so D.C. must be used. A battery will work fine. If you build a rectifier circuit (easy) use a solid state unit that is over rated for the job. After burning up two that SHOULD have worked, I resorted to a 50 amp unit with no problems. It came from Ebay for five bucks.
PUT IN A FUSE!!!!!! It's cheap insurance. Any pushbuttons or switches should be beefy in nature.
Despite all the discussion on this topic, it really is a simple project and will provide you with a tool that's useful. Mine will make every bit of metal on my bench stand at attention, so remove your wristwatch and credit cards (magnetic strips get ruined) before use!
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Old 04-05-2005, 09:19:17 AM
Orrin Orrin is offline
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Default Re: Mag Charger windings, expert advice please

I'm no expert, but I've had a smidgen of electrical experience, having worked in nuke and hydroelectric power plants of one kind or another all my career.

In answer to #1, wire gauge is critical to this extent: If you use smaller wire the resistance of the coils will be higher and you might not be able to achieve the amperage you want with whatever voltage you plan on using.

#1b) Yes, wire gauge is most certainly related to your voltage source. For instance, if you use 18 gauge wire in combination with a battery power supply, you might not be able to get the needed amperage.

On the other hand, if you use 10-gauge wire with your rectified 120 v ac power supply, you'll either blow your power supply or pop a circuit breaker.

#2) Bigger is better. Here is why: You want to achieve as many magnetic lines of force (magnetic flux density) as possible. Every material has a limit to how many lines of flux it can contain.

In other words, take the windings on the 1-inch iron core and start increasing the amperage (by increasing the voltage). One would think that more amperage would give you more ampere-turns.

Right? Yup, you'll get more ampere-turns, all right. BUT, and it is is a big "but:" a point will be reached when more ampere-turns will NOT increase the magnetic flux density. That tiny one-inch iron core has become "saturated" and more ampere-turns will NOT create a higher flux.

The three-inch core will have the capacity to contain nine times more lines of flux than the one-inch core.

#3) 1018 is low carbon steel. You might call it soft, but it is a compromise between being easy to find and suitability for the job. There are other materials that make better cores, but you won't be able to find them easily or cheaply.

You don't want to use hard steel or spring steel for your core.

I've often thought I'd like to have my own magnet charger, but considering the cost of materials (expecially the runaway high cost in the past year), I've concluded it is much more cost-effective to have our local automotive electric shop do the job for me--they charge $3.50--or go to one of the guys in the club. He'd do it for free, but I flip him a $5 bill for his inconvenience. Besides, he always has a pot of coffee handy and the conversation is priceless.

I figure I've paid out less than $30 for magnet charging, so far. Right now that looks like a better deal than spending ten times that to build my own rig. Besides, I don't have to make room to store the heavy beast.

By-the-way, I do have a commercially-built magnet charger, but it is poorly designed. It's flux path is so skimpy between poles that it saturates and won't get the job done. Someday I'll put it on eBay and advertise it as an antique door stop.

I hope this helps.

Orrin
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Old 04-05-2005, 10:06:41 AM
George Andreasen George Andreasen is offline
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Smile Re: Mag Charger windings, expert advice please

Good reply Orrin! My point was only this: make sure your wire is of sufficient size for the anticipated current and install a safety device (fuse). Other than that, JUST BUILD THE THING. It's a fun project and your fellow engine friends will consider you an electrical "genius".
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Old 04-05-2005, 06:42:29 PM
Rudy Rudy is offline
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Default Re: Mag Charger windings, expert advice please

Hi I built the Rex Heavy Duty charger and it works great. I used #10 Magnet wire. You should use magnet wire and not insulated wire so that the windings are more dense. I used 3 inch cores of C-1018 steel. You want to use this low grade of steel so that the cores don't become saturated.The key to this charger is MASS. the darn thing weighs around 150 pounds. The coils both get wound in the same direction. They then get hooked up in paralell not in series , the key is to hook them up right. If this is not done right then you will have 2 north or two south poles. Also its a good idea to use two diodes to minize switch arching.The copper wire is fairly easy to get . it is around $5.00 a pound, which works uot to $200.00. I run mine on a large 12 volt battery.
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Old 11-18-2014, 09:11:54 PM
Tim Venetis Tim Venetis is offline
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Default Re: Mag Charger windings, expert advice please

Quote:
Originally Posted by Rudy View Post
Hi I built the Rex Heavy Duty charger and it works great. I used #10 Magnet wire. You should use magnet wire and not insulated wire so that the windings are more dense. I used 3 inch cores of C-1018 steel. You want to use this low grade of steel so that the cores don't become saturated.The key to this charger is MASS. the darn thing weighs around 150 pounds. The coils both get wound in the same direction. They then get hooked up in paralell not in series , the key is to hook them up right. If this is not done right then you will have 2 north or two south poles. Also its a good idea to use two diodes to minize switch arching.The copper wire is fairly easy to get . it is around $5.00 a pound, which works uot to $200.00. I run mine on a large 12 volt battery.
In making the rex charger 10 would be too hard for me to wind would 14 gauge wire with more windings do the same job?
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Old 12-23-2014, 11:48:40 AM
Tim Venetis Tim Venetis is offline
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Default Re: Mag Charger windings, expert advice please

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Originally Posted by Tim Venetis View Post
In making the rex charger 10 would be too hard for me to wind would 14 gauge wire with more windings do the same job?
If I use 14 gauge wire but more turns will it work the same as if I used 10 gauge wire?
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Old 12-23-2014, 02:16:26 PM
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oldironcollector oldironcollector is offline
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Default Re: Mag Charger windings, expert advice please

We also built the Rex charger exactly to the plans with 10ga. Magnet wire and the soft cores. It is an excellent charger and is heavy duty. We used diodes from a 300 amp Leece Neville alternator for circuit protection. We had purchased a small charger on line and although it worked, I didn't feel like it saturated the magnets well enough. The charge didn't seem to last for any period of time. I have since bought a Wiedenhoff charger that has a rectifier built onto it so it will operate on AC. So no need to keep a battery around for it.
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Old 12-23-2014, 02:30:51 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: Mag Charger windings, expert advice please

I built a charger using the windings from two large Delco tuck starter solenoids, works fine, never compared it to a "real" charger.
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Old 12-23-2014, 05:07:53 PM
SteveK SteveK is offline
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Default Re: Mag Charger windings, expert advice please

Tim, It probably would not be the same. It would however probably be adequate. The 14Ga wire won't flow as many amps so adding more turns may or may not help, you'll have more turns but more resistance also.

What voltage are you going to use?
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Old 12-23-2014, 05:32:17 PM
Tim Venetis Tim Venetis is offline
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Default Re: Mag Charger windings, expert advice please

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Tim, It probably would not be the same. It would however probably be adequate. The 14Ga wire won't flow as many amps so adding more turns may or may not help, you'll have more turns but more resistance also.

What voltage are you going to use?
I thought I would use a 12 volt battery.
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