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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

Magneto charger magnetizer


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  #1  
Old 12-16-2018, 04:20:56 PM
lister man lister man is offline
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Default Magneto charger magnetizer

Hi there from the uk

I have been building a magnetizer i plan to use on mains voltage , When carrying out tests i have found when my coils are connected in series the ohms reading is 35ohms, i have connected them in parallel and i get a 9ohms reading. Would it be better to have them connected in parallel as the amp draw would be higher? Hope someone can help.

Andrew
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  #2  
Old 12-16-2018, 04:48:20 PM
Scotty 2 Scotty 2 is offline
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Default Re: Magneto charger magnetizer

It would all depend on how you wound the coils.
Do yourself a favour and get a book call by David Gingery entitled "How to build a Magneto Magentizer"
Well worth the read.

Cheers Scott
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  #3  
Old 12-16-2018, 05:01:32 PM
neonman neonman is offline
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Default Re: Magneto charger magnetizer

Not sure how many turns your coils have. Assuming rectified mains voltage of 240V, current through the coils in series is about 6.8A. In parallel, the total current would be 26.7A, or 13.35A per coil. So if we assume you have 1000 turns in each coil, you'd have 2000 times 6.8, or 13600 ampere-turns in series. In parallel, each coil would have 13.35 times 1000 or 13350 ampere-turns, or 26700 ampere-turns total.

Connecting them in parallel would definitely provide more ampere-turns, but the current is significantly higher. Also the heat generated would be significantly higher. Since power is current times voltage, each coil in parallel would need to handle 13.35 * 240 = 3204 watts. Not unreasonable for short duty factor.

Given the higher ampere-turns generated in parallel, I'd do that if you can safely supply the current.
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Old 12-16-2018, 06:19:59 PM
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PaulGray PaulGray is offline
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Default Re: Magneto charger magnetizer

The other thing to consider is the saturation magnetization of the pole pieces. This is how efficiently the pole pieces on your charger converts amp turns to magnetism to deliver to the magnet to be charged. https://en.m.wikipedia.org/wiki/Satu...ion_curves.svg
Certain iron alloys support a much higher field strength; cast steel and silicon steel allowing about twice the field for far less amp turns than other ferrous alloys. If your coil saturates the pole pieces, then no additional amp turns will get you more field and higher charge. So bigger is not necessarily better. I made my charger from two truck starter solenoids (several thousand turns) and at 12 volts, both coils wired in parallel and probably drawing like 15-20 amps, Iíd put it up against most other home brew units. Also make sure the bottoms of your poles are connected and fit tightly against the base plate to not have any air gaps which can diminish the total field strength. I havenít read Ron Gs book but I have working schmartz since Iím a materials guy by trade.... still, since the coils are only used momentarily, give them what the mains will handle and what the wire will take without frying the windings...
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Old 12-16-2018, 08:01:01 PM
Molinegb Molinegb is offline
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Default Re: Magneto charger magnetizer

Called the Q of coil or efficiency. Basic electronics formulas. Have most memorized after 43 years.
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  #6  
Old 12-16-2018, 09:21:51 PM
radiodoc radiodoc is offline
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Default Re: Magneto charger magnetizer

I would have thought if both coils had the same resistance that in parallel the resistance would be 17.5 Ohms instead of 9 Ohms.
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Old 12-17-2018, 01:03:01 AM
neonman neonman is offline
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Default Re: Magneto charger magnetizer

The formula for calculating resistance of parallel resistors is

1/Rt = 1/R1 + 1/R2

Going through some basic algebraic multiplication and division, you can end up with

Rt = (R1 * R2) / (R1 + R2)

So if the coils total 35 ohms in series and otherwise close to the same resistance of 17.5 ohms each, you end up with

Rt = (17.5 * 17.5) / (17.5 + 17.5)

which is 8.75, close to the measured 9 ohms.


Saturation of the core material is something I didn't consider, and would certainly factor into the decision to go in series or parallel.
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Old 12-17-2018, 04:21:57 PM
lister man lister man is offline
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Default Re: Magneto charger magnetizer

Regarding the coils they was not wound by me i acquired the coils from someone else who had started the project.
The cores measures 2 3/4 " diameter and length 10" The wire used is 18 gauge enameled wire.

I have run some test on low volts 12v dc battery and there feels a little more magnetic pull/ flux on parallel, the amps drawn on parallel at 12v is 1.3amp and
0.3 amp when wired in series ...
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Old 12-19-2018, 06:23:42 PM
barry ayres barry ayres is offline
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Default Re: Magneto charger magnetizer

look to me as if you have approx 830m of wire per coil this gives approx 3175 turns per coil

therefore in series 6350 turns at 6.8A = 43,000A/T very good for steel based magnets (horse shoe) but not enough for alnico types

or in parallel 3175 x 13.5 x 2 =85,700AT exactly what lucas recommend for charging there magneto,s

unfortunatley lucas also recommend a core area of 9sq inches but that must depend on the material the cores are made from

hope this helps

barry.
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Old 01-28-2019, 05:54:26 PM
lister man lister man is offline
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Default Re: Magneto charger magnetizer

I have now run the magnetizer on mains 240v in both series and parallel and there is a very strong pull in parallel (even the spanners on the wall move!)

One confusing thing when i initially tested it on 12v you could change the polarity of the battery and the north and south poles would switch round , but on the 240v when i switch the + - terminals on the rectifier the poles do not change, I was just wondering why this was??
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Old 02-05-2019, 10:13:18 AM
landreo landreo is offline
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Default Re: Magneto charger magnetizer

Changing the electrical polarity will change the magnetic polarity. Did you use a voltmeter check the polarity of the wires where the power supply connects to the magnet wires?

It is possible to remagnatize your compass if held too close to the charger which may give the impression that the field polarity did not change.

It will be interesting to see what you determined is really happening.
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Old 02-05-2019, 07:05:37 PM
eddie bedwell eddie bedwell is offline
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Default Re: Magneto charger magnetizer

Hi Team,
back in the mid 1960's at The Cat Dealer as an apprentice I used to re-charge magneto magnets with DC voltage from a 24V battery pack used to start big Cat Diesels.

To my not very electrical mind I would think the AC voltage would change the charger pole polarity every half cycle and confuse heck out of the magnet--possibly discharging it.
I do stand to be correct by smarter electrical and magnetic minds.
Cheers,
Eddie B.
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Old 02-06-2019, 12:08:54 AM
neonman neonman is offline
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Default Re: Magneto charger magnetizer

Lister-man did mention that he powered the charger from mains using a rectifier, which should be sufficient to keep from demagnetizing anything. I have wrecked a perfectly good compass by leaving it too close to an electromagnet. I'm still puzzled by the previous post that mentioned not being able to detect a change in polarity of the magneto charger when the + and - were reversed. That can't really happen if DC or rectified AC is used. Unless the rectifier is bad, passing AC to the magneto charger.
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Old 02-10-2019, 06:10:32 PM
lister man lister man is offline
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Default Re: Magneto charger magnetizer

I checked the rectifier with multi meter and it is showing a dc current as it recognises a + and - but it still does not switch the north and south poles when you switch the wires on rectifier.

So i went back to my 12v battery and reversed the wires on the battery and it does switch North and south poles as expected. Maybe my rectified 240v is not giving a clean signal, the rectifier was a full wave one, maybe i have a bad one???
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Old 02-11-2019, 08:36:50 AM
oldgoat oldgoat is offline
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Default Re: Magneto charger magnetizer

Depends whether you switched the AC input or the DC output wires.
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Old 02-11-2019, 11:03:40 AM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Magneto charger magnetizer

Quote:
Originally Posted by oldgoat View Post
Depends whether you switched the AC input or the DC output wires.
****************** I was wondering when someone would discover that loop hole. Ron
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Old 02-14-2019, 04:40:49 PM
lister man lister man is offline
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Default Re: Magneto charger magnetizer

It was the DC wires on the rectifier that I switched
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Old 02-27-2019, 04:07:43 PM
barry ayres barry ayres is offline
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Default Re: Magneto charger magnetizer

are both coil wound in the same direction?
think we need to see a diagram of how its wired.
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Old 03-11-2019, 04:54:06 PM
lister man lister man is offline
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Default Re: Magneto charger magnetizer

Landreo was right my compass got magnetised so was getting a bit confused
All sorted now and working properly .

Is there any consequences if magneto magnet polarity gets reversed?
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Old 03-14-2019, 05:05:39 PM
barry ayres barry ayres is offline
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Default Re: Magneto charger magnetizer

probably not so long as its saturated as most mags produce alternating sparks any way (ie 1 & 3 positive and 2 & 4 negative thats the order of sparks produced not cylinder numbers) ideally you want all negative but very few multi cylinder mags do.
out of interest what current does your charger draw? i hope to get back to building mine soon it should theatricality draw 22A on a 240V rms supply.
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