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How does a magneto work?

Discussion in 'Off Topic Threads' started by joe kuhn, Nov 18, 2010.

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  1. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    Can somebody explain how a magneto works? I've wondered that since my lawn mower fixing days of last summer. I know magnetism is on the electro-magnetic spectrum. So the flywheel comes by and taps the magnatism and sends it down the wire and at the spark plug gap it becomes like lightening.

    What's the actual transfer machanics? I'd like to know because it seems like magic to me, but I know it isn't.

    Thanks, Joe
     
  2. timb99

    timb99 Well-Known Member

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    How Stuff Works.

    Nifty website.
     
  3. phirel

    phirel TS Member

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    Joe- A magneto is simply a small electrical generator. Moving a magnet in a coil (usually copper wire) generates electricity. This is the same way the power companies generate electricity for our homes but they use larger generators. Magnetos were used in the old crank telephones and now are restricted to things like lawn mowers, chain saws and airplanes.

    The magneto generates electricity that is carried to the spark plug by a wire. When the voltage is high enough, the potential jumps across the gap in the plug as a spark and ignites the gasoline.

    Pat Ireland
     
  4. shadow

    shadow Active Member

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    You forgot the condenser Pat. It stores the energy until it reaches the point where the ignition points sendit down the wire.
     
  5. AveragEd

    AveragEd Well-Known Member

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    Sprint cars still use them, too. They have no starter or battery, so the mag provides the spark that the plugs use to ignite the methanol fuel.

    Ed
     
  6. Neil Winston

    Neil Winston Well-Known Member

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    Shadow, the small condensor in a conventional magneto is not to store electricity, but rather to suppress sparking at the points and so not only improves the spark but also extends, by a lot, the life of that mechanical component.

    There are alternator-based systems which do use a large condenser to store power, but you need a rectifier to make it work. The Lucas (see EFO's comment above) system, called "Energy Transfer" was actually a good one and provided sound ignition in the absence of a weighty battery. It's Achilles' heel was the big blue condensor which was so unreliable that it actually (possibly designed-in) ) produced, when it failed, a small bump you could see to confirm that yes, you needed a new one again.

    Neil
     
  7. Straight99

    Straight99 Member

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    Everything is made of electrons, protons and newtrons. A magnet will move the electrons in some material, like copper wire. A spining magnet will induce a voltage in the copper wire by moving the electrons. The voltage is not strong enough to jump across the spark plug so we have to use a coil with about 100 turns of wire in the primaty and about 10,000 turns of wire in the secondary. The low voltage made in the primary, about 10 volts, because of the spining magnet is multiplied by the coil to about 1000 volts. Still not enough to fire the spark plug. The points or a transistor on newer models open the primary circuit and collapse the induction in both the primary and secondary circuits. The secondary is connected to the spark plug. The collapsing induced voltage will rise to about 20,000 volts and fire the spark plug at the instant the points are open or the transistor shuts off. The condenser stops a spark from jumping across the points so they do not weld together. The same principle is used in sensors in your auto engine for speed, timing or any moving parts.
     
  8. halfmile

    halfmile Well-Known Member

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    Neil, that big blue 2MC capacitor provided a few hairy moments when a missed shift at night took out the headlight bulb.

    This was a good system for us crashers, we didn't have toworry about battery acid spoiling our custom paint job.

    HM
     
  9. Neil Winston

    Neil Winston Well-Known Member

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    Headlight? What are they for?

    Neil
     
  10. thomaslea1

    thomaslea1 Member

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    Deer hunting.
     
  11. phirel

    phirel TS Member

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    Straight99- Excellent explanation with the exception of your first sentence. There are many more things that make up matter than protons and neutrons. Electrons are probably not matter as diagrammed in some books. More likely they are an electromagnetic wave force. Perhaps Neil can explain what makes up black matter. I can't.

    Pat Ireland
     
  12. EE

    EE Banned User Banned

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    Pat, it's both. The relationship between the energy of the wave and the mass of the particle(matter) is E=MC^2.
     
  13. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    Straight99 - Where do the electrons come from, the magnet or the wire?

    Then you have a multiplier and 'collapsed induction'. What's collapsed induction? You lost me.
     
  14. EE

    EE Banned User Banned

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    The electrons that are already in the wire are made to move when they pass through (cut) the lines of flux around the magnet (the magnetic field).
     
  15. gdbabin

    gdbabin TS Member

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    Straight 99,

    Newtrons... what the hell are they? I know what neutrons "is"... how electricty flows from negitive to positive, ohm's law, and the formula for paraallel and series reactance... but newtrons???


    Perhaps newtrons were invented by a light in the loafers entertainer.....



    Guy Babin
     
  16. twotimer

    twotimer Member

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    Take the magneto out of an old crank phone and take it fishing! It works better than live bait. MIke
     
  17. j2jake

    j2jake Well-Known Member

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    They work really good. If don't think so grab the wire that goes to the plug and spint the daylights out of it. It will be a shocking experience. Almost as much fun as watching my nephew zap himself with his new stun gun. Jake
     
  18. wireguy

    wireguy TS Member

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    Magneto is a color.
     
  19. halfmile

    halfmile Well-Known Member

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    Joe, induction is what makes a transformer work. The wires of the primary and secondary are not in contact with each other, but the inductive field of the primary (created by its voltage) makes a corresponding field in the secondary which is read as the secondary voltage. Think of it as the electronic equivalent of a pair of gears.

    Now, an ignition coil is just a transformer with a spark plug in series in the secondary winding. When the current is interrupted the voltage jumps across the gap in the plug.

    The key to the coil's operation is what happens when the circuit is suddenly broken by the points. The magnetic field of the primary coil collapses rapidly. The secondary coil is engulfed by a powerful and changing magnetic field. This field induces a current in the coils -- a very high-voltage current (up to 100,000 volts) because of the number of coils in the secondary winding. The secondary coil feeds this voltage to the distributor (or plug on a single cylinder motor) via a very well insulated, high-voltage wire.

    In common DC ignition systems (battery/coil) the power source is external. In a magneto the voltage is created within the device itself, since the coil is in the magneto.

    Many vintage motorcycles used magnetos for simplicity and weight reasons, although there were a lot of battery/coil setups too.

    These days we have a variety of systems that use new technology, like energy transfer, CDI (Capacative Discharge Ignition) and God knows what else that I don't know about, since onboard computers run the stuff. Usually the repairs to these involve a shotgun approach of replacing parts till the thing works again. My solution to these is to find a pal with knowledge.

    I like your thirst for knowledge. Keep on truckin.

    HM
     
  20. geeber

    geeber Member

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    They are reliable too. They are still used today on continental and lycoming aircraft engines.
    Gary B.
     
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