The way a sparkgap works, the breakdown voltage is higher than the sustaining voltage. In other words, to make it go "zap" you have to apply a higher voltage initially for a very short period (in the vicinity of microseconds) before the gap "breaks down." Then, the gap will have a very constant voltage across it while the power source supplies _current_ to it. Breakdown and sustaining voltages are determined by the size of the spark gap (the distance the spark must jump), the physical shape of the gap (sharp corners produce lower breakdown voltages), the gas pressure, and the type of gas.
A secondary consideration is the condition of the plug's
insulator. If the plug is fouled, the mag must supply some
current through the goop in the gap in addition to the gap
itself, before and after the gap zaps.
Another consideration only for starting (but not running) is
how the impulse coupling works mechanically and
electrically. Different designs could easily produce varying
amounts of energy for that first spark at low RPM.
A complex situation presented by the condition of the plugs
and wiring determines the voltage at which they zap, but a
mag with higher available total energy should fire cruddy
plugs better. If your plugs are in good shape or new, and
the wiring is OK, a mag with a better impulse coupling
system could produce a longer, fatter spark. While running,
a mag which produced more energy would fire cruddy plugs
better (more consistently). Once the the gas starts burning,
I'm not sure the plug has much effect, though.
IMHO:
A physically larger, heavier mag would probably produce more
energy than a lighter one. This analogy is generally true
with motors and generators of all kinds - if they are
constructed with the same type of materials, the bigger
heavier ones will start a plane easier or produce more
electric energy. Ya takes yer choice: light weight or more
poop. Aircraft are designed with lots of compromises, a
primary one being weight. If you keep your plugs and wiring
in good shape, it shouldn't matter much which mag you use.
David Smoler | __ | San Jose, CA
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Alon A-2 | \____/ | N6359V
s/n A35 () () () based at RHV
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Steve Dold wrote:
>
> At 02:25 PM 4/28/99 -0700, you wrote:
> >Steve,
> >According to the bench tests I've read...the Slick Mags produce 25,000V
and
> >Bendix, for example, produces 43,000V
> >
> >Keith Bolte
>
> I wonder if the voltage matters? Maybe it's the current
> capability that counts. Isn't the voltage only going
> to rise to the point where the spark occurs?
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