I’m kind of fascinated by them. It’s one of those things I knew about but never really learned much about them.
From Harley’s to airplanes to tractors. Since they make them for 8cyl engines, what’s the reason they’re not used more often in road-going vehicles instead of distributors? Does it have to do with advancing/retarding?
And with the impulse thingy, they make great spark at low rpms and obviously better at higher rpms.
i think it was a cost thing, why they started going to distributors.
IIRC, magnetos make their own power. Which means you don't need a battery or an alternator.
That eliminates things that cold break from the system- which is pretty important for flying. And it's helpful for off road vehicles, too.
Aren't they very electrically noisy?
Not the strongest spark in the world and fixed timing, with the exception of the impulse coupling, which is a mechanical mousetrap kind of device.
Also, every airplane I’ve flown had dual mags/ignition, which gives some indication of reliability expectations.
Wiring install is very simple though— one wire for each plug and a single P-Lead to ground out the unit to shut it off.
The Jacobs radial engine on the Cessna 195 used a mag and a distributor— you started it on the distributor for the advance and hotter spark, then ran on both.
Fixed timing, outside of starting isn’t a big deal on aircraft engines, as the RPM range at which you’re asking for max power is pretty narrow.
Also, if you’re taking mags to higher altitudes, they need to be pressurized to prevent internal arcing.
In reply to Karacticus :
Even so, it's more reliable than relying on a battery and alternator/generator- if that system fails, the plane still flies. The second one is even more of a back up.
Very noisy. Doesn't play well with EFI since it makes noise. Spark is more amperage and a bit less voltage, so plug wires need to be beefy and plug gaps need to be pretty small.
Not sure if it's the higher amperage, but they do tend to fail more frequently which (as has been mentioned) planes have two. I did have one fail in an Archer 2... fortunately during takeoff and I had time to slow down and taxi back on the second mag.
So... in answer to the original question... yes, but in very limited applications with a specific need. Not really a street thing.
In reply to Curtis :
I understand some of the limitations now. I was and still am intrigued by watching some of the Morris Magneto videos. Of course they’re specializing in V-Twin motorcycles but the simplicity and science behind them is pretty cool. At least for a simpleton like myself.
And speaking of simple, in my world, EFI wouldn’t be an issue because my brain lives in the 70’s!
Illegal in some racing organizations (SCCA) because if the wire breaks the engine won't shut off. McLaren M8 Can Am vintage car I worked on appeared to have a magneto as original, but it was a fake so we could use modern electronics and the owner/driver was more comfortable with his ability to shut it down.
ebonyandivory said:In reply to Curtis :
I understand some of the limitations now. I was and still am intrigued by watching some of the Morris Magneto videos. Of course they’re specializing in V-Twin motorcycles but the simplicity and science behind them is pretty cool. At least for a simpleton like myself.
And speaking of simple, in my world, EFI wouldn’t be an issue because my brain lives in the 70’s!
Me too. Give me a Qjet and points and I'm a happy guy.
Curtis said:Me too. Give me a Qjet and points and I'm a happy guy.
SHHHHHH!
You'll angry up the natives...
Some of the stuff I work on has magneto ignition.
Timing is generally fixed or manual advance.
When they fail, they fail "on" A mag has to be grounded to shut it off.
The faster you spin them, the hotter the spark gets. Pretty much the opposite of points ignition where, because of reduced dwell time, the spark gets colder as rpm increases.
The engine has to spin at a minimum rpm for the magneto to fire. This is why the Jacobs has a distributor, hand-propping the plane generally doesn't spin it fast enough.
Cars that require hand cranking will generally have a storage battery and distributor or timer. You start the engine on the battery and then switch to magneto to run and drive.
Magnetos are self-energising, if you don't have a charging system, you can run a magneto or run a conventional ignition as a total loss system.
Last ones I worked on were a pair in a radial engine WW II tail dragger Navy training plane being restored outdoor at Bridgeport airport in CT. Been 20 years since then, haven't seen one since.
Couldn’t centrifugal advance be incorporated into a magneto? I can’t think of how but I’m no engineer! I thought some tractors, Allis-Chalmers for example, had some centrifugal advance. Or maybe I’m thinking of the impulse coupling?
...and wouldn’t a magneto-powered ignition system survive the inevitable EMP blast where most of our I.C.E. vehicles would be disabled?
(just planning ahead 
)
Karacticus said:Also, every airplane I’ve flown had dual mags/ignition, which gives some indication of reliability expectations.
Wiring install is very simple though— one wire for each plug and a single P-Lead to ground out the unit to shut it off.
I kinda mulled this over a bit, and I think it means the opposite of what you think it means? Aircraft design is all about ensuring the number of landings equals the number of takeoffs. If every plane had magnetos, none had Kettering ignition, that is more of a praise of magnetos than the fact that there are two separate ignition systems.
And I strongly suspect that the lack of electrical connections to fail is a large reason why type certified engines use them.
I know a guy in Nebraska that built a Sportster chopper. He hates electron tubes and stores, so built the entire bike with a battery eliminator circuit and a magneto. The only electrical system wires are for the headlight and brake light. Kick start.
In high school, my friend Randy, later to become the builder of what became Jay Leno's tank car, had an (actual) 32 Ford coupe hot rod. He built it to be a 1950's hot rod (late 70's). Nothing on it was not available in the 50's. Flat head Ford V8, 6 pack, etc. He had a magneto on it. He said he was playing with it one day, holding the mag in his hand and just kinda spinning it until it shocked the E36 M3 out of him.
In reply to Curtis :
Hey Curtis, what do you do for work? You seem to know about a lot of stuffs, deeply. (Unless your a google wizard?) lol.
Interesting that the impulse when turned by hand would produce a spark. Of course that is it's purpose.
Coils seemed to be the biggest failure point on those I fixed.
Heck yes Magneto is awesome.
Sorry had to. I could not have been the only person thinking it.
In reply to Mike924 :
Lol. Every time I see these superhero movies I think how I would defeat them using normal, everyday items. For this guy, I would bring a fridge magnet and repel his old ass back to the senior center.
Dr. Hess said:I know a guy in Nebraska that built a Sportster chopper. He hates electron tubes and stores, so built the entire bike with a battery eliminator circuit and a magneto. The only electrical system wires are for the headlight and brake light. Kick start.
In high school, my friend Randy, later to become the builder of what became Jay Leno's tank car, had an (actual) 32 Ford coupe hot rod. He built it to be a 1950's hot rod (late 70's). Nothing on it was not available in the 50's. Flat head Ford V8, 6 pack, etc. He had a magneto on it. He said he was playing with it one day, holding the mag in his hand and just kinda spinning it until it shocked the E36 M3 out of him.
I love everything about this entire post!
_ said:In reply to Curtis :
Hey Curtis, what do you do for work? You seem to know about a lot of stuffs, deeply. (Unless your a google wizard?) lol.
Sorry Curtis, for “speaking” on your behalf:
Occupation
Theater Technical Director
Interests
gettin' greasy
This place still AMAZES me year after year with the knowledge that spews out of here.
iceracer said:Interesting that the impulse when turned by hand would produce a spark. Of course that is it's purpose.
Coils seemed to be the biggest failure point on those I fixed.
There’s a short YouTube video of a science teacher that built a little hand-crank and had it hooked up so you could crank it and see the spark. But keep in mind, the impulse coupler winds up the mechanism so it suddenly releases with some speed.
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