magneto vs distributor

I have seen numerous posts on {wico} magneto's and know that they are functionally the equivalent to a distributor. Other than knowing their main task, what are their differences in operating? I also noticed in another post that if you want to change from a mag. to disb., you will need a coil.

Just wanted to become more familiar with other tractor designs and build a little more knowledge.

Thanks in advance,
tom

Thanks
Tony Hardy Boise, ID

regards,
tom

~Mags were used on many of the hand start tractors because many of those tractors didn't have batteries or electrical systems.

~There are many types of both mags & distributors. Most mags use an internal ignition coil that is both mounted & powered internally. Most [but not all] distributors use an externally mounted ignition coil.

~To get a little more technical, most [but not all] mags have fixed running timing [usually in the 20� to 30� range with some type of retard mechanism to reduce the spark advance to around 0� for starting purposes at cranking speeds [usually under 300 RPM's]...Most distributors have a variable spark advance that slowly increases the spark advance as the engine RPM increases [that's it's big benefit].

~Most magnetos also have some type of low speed impulse [a type of hold & let go mechanism] that not only retards the spark at starting speeds but also momentarily holds the rotating internal generator with a spring then lets it go as the impulse TRIPS. That not only retards the spark for starting but also increases the internal generator's speed to produce a hefty spark at low initial cranking speeds, as the mag's RPM increases that impulse quits holding & letting go & the speed of the mag's internal rotor [generator] is then fast enough to run the mag without the impulse tripping.

~Magnetos have been around for years & if kept in good repair will run a tractor within it's designed operating range with plenty of power & reliability. A distributor's main advantage is the fact it has a built in spark advance & is easier to service & understand for most people.

~Most distributors produce a slightly stronger spark but some of the more popular mags can also be built to produce a very strong spark.

~Another way to look at a magneto is it is just a distributor with a generator built into it so it can make it's own power, it still has a coil [just like a distributor], it still has a set of points & condenser [just like a distributor], it still has spark rotor & distributor cap [just like a distributor]..... ..

~Any more technical questions just post back or E-Mail

[email protected]

A Magneto is self powered and requires no external source of energy from a battery. Thats obviously why they were used and still are on equipment such as non battery hand start tractors and all sorts of other manually start engines like lawn mowers etc etc. Battery powered coil distributor ignition systems use the tractors battery to develop the energy necesary to fire the spark plugs.

A Magneto or Distributor still requires a coil which acts as a high voltage step up transformer to convert 12 volts to 10,000 or more necessary to arc jump current across the plugs gap. Its just that mags have an internal versus the external type coil youre used to seeing on battery powered distributor ignitions. Wico did produce a battery powered internal coil distributor ignition that looks a lot like their XH series Magneto.

Magnetos produce their energy from a magnet passing by a coil of wire which induces a voltage potential across the wire ends (low voltage primary winding). That energy is momentarily stored in the coils low voltage primary magnetic field and then when that field collapses, the stored energy is party induced (via transformer action and mutual magnetic coupling) over into the coils high voltage secondary winding at a higher voltage potential which ramps up the voltage to where it arcs current across the plugs gap. A battery powered coil ignition still has a coil that serves the same function, it just gets its energy from the battery versus the magnetos passing a magnet by a coil of wire.

Mags are limited to the amount of spark energy (volts x amps) they can produce by that developed when a magnet passes a coil of wire verus a more abundant energy source (stored in the battery battery) on the distributoir ignitions. Thats NOT to say a magneto cant produce abundant energy, it depends on the size of the magnet and coil and how fast it passes by the coil etc. Its a matter of enginering and economic trade offs.

The faster a magnet passes by a coil of wire, the more energy imparted. However, at slowwwww hand crank RPM's theres insufficient energy developed to fire the plugs. Thats whay mags require the spring wind up and trip assembly which winds then trips a spring to rapidly whirl the magnet past the coil when she snaps over at crank speeds. Then at around 250 RPM or so, the wind and trip drops out (mag stops snapping over) and the rotor is runnign at crankshaft speeds.

Theres whole books on these subjects, but hopefully this will suffice for now. Post back or e mail [email protected] or call 812-824-4608 if you need more in depth descriptions.

Good Luck n God Bless

John T Nordhoff in Indiana