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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

Model Engine Coil


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  #1  
Old 01-20-2011, 11:59 AM
Andrew Mackey Andrew Mackey is offline
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Question Model Engine Coil

I have a Super Aero Spark model engine coil, probably used in a spark ignition model plane. It is attached to a square condenser marked DC 200V.300 mmf. The letters OBE are within an oval, and Type DP and USA seem to be cast into the shell. I believe the coil and condenser are from the 1950s. The coil is about 1" in diameter and approximately 1&1/2" long.

My questions for this are: What voltage does the coil need? Is the condenser attached OK for use with the coil? It was run on 2 'D' cells previously.

I also have a more modern coil that says 3 to 6 volts . I plan to use one of the coils to provide ignition for a Wall 30 cc 4 cylinder engine. My second set of questions relates to power supply: I plan to use a 12 volt lead acid battery to power the engine, as it will have a 12 volt water pump for cooling, and a tachometer. How much resistance do I need to knock down the power and voltage to around 4 volts, and to the voltage needed for the Aero spark coil, if it needs lower voltage? Would I be better off getting a small motorcycle coil for the engine?

Thanks for the replies,
Andrew
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  #2  
Old 01-20-2011, 02:29 PM
Ronald E. McClellan Ronald E. McClellan is offline
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Default Re: Model engine coil

If it were mine I would run the coil on 2 D cells. Why take the chance on an accidental short circuit and burning up the coil. Ron
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Old 01-20-2011, 04:11 PM
Dempster Dempster is offline
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Default Re: Model engine coil

Would keep the recommended voltage to the coils you have. I've seen too many of ignitions for large and small engines with step down resistors that just aren't reliable so sooner or later the resistors fail or a short happens as said and it all goes up in smoke and the coil will get fried. If battery is dead and someone jump starts it wrong causing a spike will burn the coil up too. If want to use 12V get a 12V coil.
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Old 03-14-2011, 03:05 PM
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Leadchucker Leadchucker is offline
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Default Re: Model Engine Coil

I've been flying the pre war ignition engines since the early 1970's and here's what I've learned in 40 years
Model airplane coils are run on 2.4 to 3.6 volts depending on the maker. Old coils such as Aero-Spark,Wilco,Model Tech, etc. were designed to run on 2 AA batteries as the flight pack using 2 large dry cell lantern type batteries as boosters for starting.
You'd hook up the boosters to terminals on the plane,start the engine and adjust the timer (spark) or mixture,unhook the boosters the start the engine run timer. Battery quality, or lack of it really in the "old days" were the cause of more model engine trouble than anything else.

Newer coils such as Model Flight use 3.6 volts and are very small compared to the old ones. No one uses dry cells anymore as we have NiMh's and LiPo's which have enough power to dispense with the boosters and will last all day for flying. I'd make up a pack of 3 2500 maH AA cell Nimh's for coil power which would give you 3.6 volts.. They are cheap, easily rechargable and have long self discharge time.

You could use the condensor you have, however there are electronic modules that eliminate the condensor and use the points as a trigger with no load on them. Result is low battery drain, no point arcing or pitting,a bit of dirt on the points won't stop the works from running and you can use 20 gauge wire for all the circuits except your high tension lead. Most have a built in feature that shuts down the power to the coil in case the engine stops with points closed or you leave the ignition idle with power on too long. Hope this helps you some
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Old 03-20-2011, 02:21 PM
Lloyd H Lloyd H is offline
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Default Re: Model Engine Coil

If you want to use 12 Volts the series resistor would need to be 3 times the coil primary resistance to drop coil Voltage to 1/4 of the 12 Volt supply (3 Volts) or 4 times coil resistance for 1/5 of 12 Volt supply (2.4 Volts). Volts across the resistor times Amps thru the resistor give Watt rating required. Lloyd H
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Old 04-21-2011, 08:22 AM
Karl T Schwab Karl T Schwab is offline
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Default Re: Model Engine Coil

Hi Leadchucker! I have a 1946 Champion dual point ignition model aircraft engine that I want to run on an spark plug; currently I run it on a glowplug. I want to return it to its original operating system; I have the original dual timer (points) that came with it. Do you know where I might find a model engine coil for it? Also, would you have any info that you can share with me on the dual point system; i.e. how to wire it up. I am guessing that the dual point system is for varible engine speed, maybe? I would appreciate any info that you send along. Regards, Karl
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Old 04-21-2011, 09:20 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Model Engine Coil

Check with the Davis family website, I believe a sponser here on the Stak. They have a model engine section that lists many suppliers of model engine parts and supplies.
Andrew
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