[link=http://www.allstar.fiu.edu/aerojava/faq_princ_flight.htm#impulse]Read this FAQ on inpulse couplings.[/link]


The fact that you should replace a faulty ignition switch, or secure the ground wire when a ground run up reveals that the magneto will not go off is not the point. The point is that this is often intermitant and may not show up during a run up. For example a loose ground wire may vibrate enough to maintain enough contact during runup to cause the RPM to drop on one mag, yet be an open circuit when off failing to ground out the mag.

Hello; The very first self starter I had any experience with, was on an old laFrance fire engine, around 1911. All it would do is fire all four spark plugs at the same time. The hope is that at least one of the cylinders would have a combustible mixture in the cylinder, and that everything was in the proper position to fire in the right direction. If it didn't fire and continue running, you would have to get out and deal with the hand crank hanging off the front of the engine.

It's easy to see that an engine could start with everything in the right position.

Easy for most. Then there are those who don't pull the plug wire off their lawn mower engine when removing it to sharpen, because, after all, it always takes three pulls to get it started anyway ... And there are those who lose fingers or worse, from time to time.

Well if I remember right as a kid my dad had a 1936 Stinson and he would lean engine to quit first and then hit kill switch. If the switch was bad he wouldn't know it because the leaning would kill the engine first. Just as engine was dying he would put fuel back to normal. A couple of members in my Model T club have good running but wore out engines . When warmed up and shut off will self start just by turning on key. This is not magnito but battery fired coils. This will not happen on a fresher (higher compression engine) I could see a big person lean on a prop of a well worn airplane engine and turn it just fast enough to create a spark.
There is no such thing as a 200 lb catfish in the USA. Record is about 100 lb but if you caught that on 2 lb test line you'd be famous. This is just an old urban legend around if your a fisherman...............

Well I could see a man proping his leg on a Model A crank at the 3 O'clock position with enough force on a worn engine to turn over the engine with enough speed to fire engine. We have a couple of members start their T's with light foot action. Total mag 1914 and 1912.........Just like propping foot up on a log...........

During the run up he should have checked the mags then, switch from both to l then R and back to both. A drop in RPM is an indication that the switch is working, however it could work during the runup but because of vibration causing contact still fail when the engine is not running.

I have had 2 starts in the last 40 years with no glow ignitor just after a refuel. THEY WILL START not often but they will. Jim

>>> Jeesh, my engines are reluctant to start when primed, glow plug powered, and using an electric starter. >>>

After a long serious day of all kinds of work around here, and then reading through this very serious, safety minded thread...... that REALLY got me to laughing. I'm still laughing and needed that badly. Thanks loads!!!

Ernie

I'm not buying the strories about model engines starting all by themselves without the glow igniter attached.

Yeah, right.

FBD.

FBD:
You sure know how to bring a conversation to a screeching halt. I would have thought as a "moderator" that you would strive to encourage input, not stop it. Why don't you find other people's experiences real? It may never have happened to you, but that doesn't mean it hasn't happened to someone else.

Now, I'm no engineer, but it seems logical to me that the glow igniter is attached to the motor to create a spark and start the engine. Once the motor is warmed up, we pull the glow igniter OFF the motor, yet it still runs, I guess because there is enough heat in the engine to keep the glow plug igniting. No one leaves the igniter on the engine when they fly. So, if the engine is still hot enough from a previous flight, there's combustible vapors in the carb and compression in the motor rotation, it seems perfectly reasonable that the motor could start without the ignitor in place. Doesn't that make sense to you?

I've heard, and read that....

"In glow fuel the catalytic reaction is generated between the methanol and platinum only".

If this were the case, we wouldn't need to get the coil of wire red hot with the glow
igniter so the engine will fire.

Have you ever tried to fire up an engine John, and forgot to connect the glow igniter ?
I have, several times....and the engine won't fire, or even pop. Fact is....without the
glow igniter hooked up, the liquid fuel will drown (wet) the plug and make it harder to
start....and if too much fuel gets on the platinum coil....

....it will become impossible to start....flooded engine. You can believe anything you want
to John....so can I.

I've flipped engines over a million times....I've never had one fire, even "bump" without
the glow igniter connected.

FBD.

Two comments. First the original statement, and mine also, was about an engine starting when the glowplug was connected. Others said they had it happen to them without the glowplug. Should also comment that no one said it was a common occurrence, and I am sure many people have run engines for a long time without it happening.

Edit: Inflamatory remark removed by Moderator.

I must admit when I first heard about this my first reaction was the same as Dave's...Yeah, right. This was based on the huge amount of time I've spent flicking over engines and never having heard of it from any modeller I've been around. But there was a similar thread some time ago over on SSW (CL stunt mainly) and a few there said it had happened as well so there must be something in it. The only difference I can think of between my own experiences locally and others overseas is the use (or lack of) of nitro. I wonder if there's some correlation between the amount of nitro used and the occasional start? Nitro isn't good at handling compression which makes me wonder if possibly it can act a bit like ether in model diesel fuel if the circumstances are exactly right. We use very little, if any, nitro in Australia which may be why I've never encountered this problem.

I have posted earlier in this thread, that I had one "pop" on me, and still have the scar on the back of my finger to remind me

It was back in the mid 70's and an old "mentor" (you might call him ) gave me a couple of his control line engines from the 50's...
The engine was quite stiff and gummy from castor residue... I put some fuel in it to loosen it up, and as I was holding it in my left hand, and flipping the prop w/ my right (as I have done many many times before ) it popped on me and cracked me on the back of the index and middle fingers...and surprised the heck out of me!

Edit: obviously, that does not fit the description of the thread title...but something did happen, without any battery attached to the plug.

I think there is, the catalytic reaction is stronger with methanol than with nitro, and engines made for low nitro tend to have higher compression ratios. I suspect that this along with some built up varnish insulating the glow plug element can combine to create the rare unlit plug start phenomena.

Ether works in model diesel fuel because it has a very low ignition temperature. Not so with nitro, it detonates after it has ignited from compression of its rapid flame front, which is more rapid than that of methanol. Nitro is actually more difficult to ignite than methanol. With very rich mixtures it is also more difficult to ignite than gasoline which is why the AA fuel dragsters have such large magnetoes, in fact the electronic magneto gave a huge power boost to those engines because it allowed them to run even richer mixtures of nitro.

Ignorance is bliss. Absolute knowledge is reserved for those of us not of this Earth. And the graveyards of the world are filled with folks that say 'Huh?'

Hope you never get your come uppins brother, it'll smart.

Now leaving batteries on a concrete floor and having it suck the life out of them, that IS bogus.

Clean,
I think you replied to the wrong post. Philip agrees with you.

I wasn't dis-agreeing with Phillip either, but this thread is looooong. I would have used a quote, but I really don't see the need to propagate erroneous information. I know, in an ideal world the mag switch works as advertised, the engine does shut down without enough fuel to fire one more time and everything is wine and roses. And I understand where he's coming from, it's supposed to be safe, but it isn't and that's really all there is too it.

As far as the engine starting without an igniter or when you put the igniter on, when the non ignitor thing happens to your Fox 35, man that is suprising. I'm more used to it pushing the piston back when it is overprimed and spitting burning fuel onto the ground, your plane, yourself. You wonder why the paint is blistering on the nose of your Goodyear and also why your hand is getting hot. If you're in the middle of a Foxberg race and have just doused the engine with fuel to cool it off a bit, then you're really in for some fun. You can't see the flames, but man are they there.

----------------


If I'm not mistaken, the old, ancient Fords did not use breaker points in a distributor to fire the spark plug. The ignition coil was set up with enough capacitance to go into resonance (self oscillation - producing sparks continuously). The compression in the engines was low enough that the piston had to be a fare way up the cylinder bore before the continuously sparking spark plug would ignite the mixture. It was similar to glow operation in that the plug was always lit. Later, they became more sophisticated and used a distributor as we know it. If I am wrong, please let me know. But be forewarned that the pulsejet guys were using these old spark systems to ignite their pulsejets, so I know these ignitions existed for a fact. Although it is possible that they had to be modified to operate in the "constant on" mode.


Ed Cregger

Twice in the past 6 years I've had a Nelson .40 start without touching the prop. However, glow was applied.

Having one of these fire up untouched is a bit scary, I always make sure someone is holding the plane before I apply glow power.

As to them firing without glow, I struggle with that one, but I've seen stranger things to discount it.

I personally have had glow engines start WITHOUT the glow igniter being connected. I must clarify, however, that this happened around 7 or 10 seconds after the engines have quit; this without using nitro mix in the fuel.


Regards,

Misterpanda

I also have had this happen on glow engines a few times over the years. Always after the engine had just quit. In fact I've even done it intentionally(after seeing it work on accident) when a engine died right after I removed the glow driver. on a good running engine(not rich idle) you can even "kill" it by dragging your electric starter on it and relight about a second later fairly often(safety geeks use your safety cage and steel mesh gloves please). As Far as the full scale issue, there is a video on the web that shows starting a Sopwith Camel by turning backwards to prime, positioning at TDC, the flipping the mag on. So it could be as little a "wiggling" a intermitent ground. One thing I've learned in being a mechanic for 20 years is (myself included) Don't assume that your gonna "see it all" in a lifetime, much less in 20-40 yrs. I've had to eat my words before on units I've rebuilt 1000's of! Ever heard of greasy shop rags spontaneously combusting in low humidity? Ynow those funny red triangle "hampers" you have to put them in?? Todd

If I had a dollar everytime and old codger said "I thought I saw it all!", I would be a billionaire!

This is one I have heard about, I have even heard about people trying to get this to happen on purpose. I suppose the humidity was not low enough, or the ambient temp not high enough, or not enough oily rags used, or oil of poor combustability, because you still hear of this happening from time to time.

Oily rags catching fire by themselves: It's called "spontaneous combustion". We learned about it as kids in science class, way back. It also happens to be a rather frequent phenomenon with cotton bales, all which requires a special treatment for insurance coverage purposes.

Misterpanda

It do go way back, I believe Mr Wizzard showed an example on his show. Course I think it was a rag with Mineral Spirits or something that goes through an Endomorphic reaction while drying. Back in 93 we had a little October surprise that killed just tons of trees with snow damage. So our city had collection points where they turned all the wood into wood chips. Mountains of them. 3 of which caught fire when the chips started to decompose. Hey, if my 4 x 4 x 4 compost pile can get hot enough to steam on a early spring day, what else could catch on fire.