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Making a low tension Magnito

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Old 05-17-2005, 10:50:37 AM
Dick Welty Dick Welty is offline
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Default Making a low tension Magnito

Hi Guys and Girls,

After making a couple of suggestions for Tom Jamboretz about his Fairbanks Morse Headless Mag gear Mesh/Lash adjustment problem I launched into an other subject citing my need for an original headless igniter to beg, borrow or buy to make patterns to have some cast.

I also said that I was trying to make a practicle low tension Magnito for this and other engines that are missing the originals magnitos.

I tried the permanent magnet motor which becomes a generator when turned by chucking the shaft in a drill motor. I then hooked the leads to an igniter to test for spark. The results were less than spectacular.

I then hooked the leads in series to an igniter coil and the igniter and got a good spark. Next I will make Brass end and bottom plates to mount the generator and I will fabricate dummy horseshoe magnets to go over the top to make it look like an original type magnito.

I always feel like if the part looks the same and functions the same it is at least good enough untill I get the original part. In this case the original part is a Sumpter 12 magnito which I have heard is problimatic at best so I might not look too hard for one anyway.

Anyone have a spair original Igniter for a headless for sale or loan?


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Old 05-17-2005, 11:10:00 AM
Kevin O. Pulver Kevin O. Pulver is offline
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Default Re: Making a low tension Magnito

Sorry dick, no ignitor from me, but I love the sound of your magneto. Please post photos and let us know how it works. I've been fascinated also by the modelers using a Piezo crystal ignition. It's the push button gas grill lighter sparker thing. They say it works good. I hope you find the parts you need. Kevin
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Old 05-17-2005, 03:52:13 PM
Andrew Mackey Andrew Mackey is offline
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Default Re: Making a low tension Magnito

A number of years ago, Dick Shelly, Who makes museum quality models, had several models he ran on Piezio Electric ignition. They looked like a micro-switch, and could pass for a small WICO EK ! I don't know where he got them, but they worked swell.
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Old 05-17-2005, 06:21:13 PM
Mark Birdeau Mark Birdeau is offline
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Default Re: Making a low tension Magnito

Dick,I have been working on this idea in my head for a couple of months now.I have tested several differant size 12 volt motors and the best I could get was 9.5 volts at 2500 rpm's on the drill,and about 1 volt turning the shaft by hand with a vice grip.This was just on the shaft of these motors.I did find one when turned with the drill to the gear box that the motor runs would put out over 100 volts and over 40 volts by hand with the vice grip.The problem as I see it is how do you get enough voltage at cranking speed but don't blow or burn the unit up at engine speed.I'm sure that at engine speed on the gear box the motor is most likly turning 2-3 times it's normal operating speed.What type of motor are you using and have you checked the voltage out put?How much voltage would be needed? Mark:
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Old 05-17-2005, 11:23:42 PM
Dick Welty Dick Welty is offline
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Default Re: Making a low tension Magnito


The motor that I am using is an industrial quality 19.1 volt dc motor. Even though it is only 2" in diameter and about 3 3/4" long not counting the shaft it weighs about 2 lbs.

When turned with an open circuit it will coast when turned fast with the fingers. When the output circuit is closed it stops dead and gives considerable resistance to turning. I can't lay my hands on any meters right now but I know it will work as I have tested it with the igniter and coil at fairly slow revolutions and it gives a good spark.

The original cam gear that I will probably use is going to turn at twice the crank speed which is not very fast but because the permanent magnets that are built into the motor are very strong and the motor is a 19.1 volt motor I think that it will work fine at running speed and will probably even work at startup.

Only after I get it hooked up to a good running engine will I know whether I will have to use a battery for start up. As I understand most of the original Fairbanks Morse Headless engines with the Sumpter magnitos have to have batteries for startup anyway.

If worse came to worse I can use a battery to start the engine then when the engine is running I know it will work. Being a 19.1 volt motor I won't even have to worry about burning it out by running 6 or 12 volts thru it if that becomes necessary for start up.

The only thing different about using it is that I will have to leave the coil in the circuit all of the time to make it work. Aparently the motor windings don't have enough inductance to induce the hot spark that the coil produces.

Here is a picture of the motor I intend to use.

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Last edited by Dick Welty; 05-17-2005 at 11:36:23 PM.
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