DarZeelon

Randy,


In regards to the great Ray Arden...

Those first Ni-chrome coil glow plugs did work, but only because they were energize all the time by a power source...
...Or they were large enough for the coil to absorb and to retain enough heat from combustion, to perpetuate the ignition.

If you use power all the time with a contemporary, platinum glow plug, it will not last very long either.

And, even that article states the importance of the catalytic effect.

DarZeelon

And, Randy,


The mixture strength is the method we use to control the 'ignition advance' in our glow engines...
It determines when the maximum combustion will occur, since the leaner the mixture, the faster it burns and the more easily it ignites.

If you run a glow engine on gasoline based fuel, you could also find a setting that would not cause the glow element to pre-ignite the mixture.

speedster 1919

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Dar --In away you admitted your wrong and the argument had nothing to do with plug size. This was with noooooooooo platinum.
And DAR -- think about before you write. There are plenty of planes flying around with part and full time on board glow. The secret is limited voltage. The plugs can last a long -long time.

w8ye

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POST EDIT While I was composing this post there were three post added and a couple say the same thing that I did. So I have just repeated what has already been said without knowing it? -w8ye



Platinum was in use in high performance spark plugs long before 1947. I remember in the early 50's of my Dad speaking of the Platinum plugs used in the airplane engines of WW II. He was an aircraft mechanic during the war.

I read all the articles in the link posted above and observed the following... The early glow plugs were boosted full time. I remember early glow plugs being rather short lived and the coils would distort out of shape and break. That the platinum iridium was used to help solve this problem and the post war "auto reaction" observance came later?

IMHO assume the platinum iridium element was first used in an effort for extended durability and the catalytic reaction was soon observed afterwards.

Take note that if present day glow plug elements become coated with the dreaded "white stuff", or with metal particles, they no longer continue to glow and the fire soon goes out if the battery is removed.

Speedster, you are not a liar but the URL you presented is not a "technical paper" and is only a recollection. You need to read the book published about modern two stroke model engines recommended to you by others. Some "others" posting in this thread are notable people in model aviation in their own right.

JNorton

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Speedster,
All current modern glow plugs use platinum and are capable of self sustaining reaction. Nothing else to my knowledge does. Every modern commercial glow plug uses a platinum element. Why are you saying a glow plug doesn't need platinum when I can't buy one that does not use it? You are doing a great disservice to many people who read this thread and take you at your word. Just my opinion.
John

Harry Lagman

Speedster, I second W8YE's statement: none of us intended to portray you as a "liar". The recommendations for further reading were genuine.

Although I haven't tried it myself, I will take your and anyone else's word for it that a glow engine can run on a non platinum group glowplug, but it will need to be kept hot with externally applied electrical current.

The key point we are putting forward is that platinum is a catalyst for the oxidation of methanol. So, in a way, it is a bit of a "secret ingredient" in a modern glowplug.

Check out this abstract from an SAE paper on how the presence of platinum or platinum/rhodium can reduce the glowplug temperature required for stable combustion in experiments using methanol as fuel.

http://www.sae.org/technical/papers/911737

Sport_Pilot

Keep in mind that glow plugs work without constant power on all nitro and all gas fuel as well an methanol. There are some problems with idle and with gas attaining full power, but a constant power source is not needed. The first Arden plugs with ni-chrome elements did not need constant power. Those were not put in production, only the platinum Arden plugs were in production, so if you remember using constant power with early glow plugs, it was not because the plugs were not platinum. Most likely you were looking at early racers using exotic fuels that did not use methanol and something other than nitro.

Also keep in mind Arden discoverd the glow plug effect when center electrode was glowing on a plain gasser engine. I know of no model engine plugs with platinum negative electrodes. However he experminted with ni chrome and I suppose that may have had some catalytic effect, even iron may, but IMO there needs to be some heat retainage for even the high catalytic reaction plugs. There is little to no catalytic effect when the plug and fuel is cold, and even the heat of compression is usually not enough.

Sport_Pilot

Why is it so hard to believe that a glow plug can stay hot between strokes without a catalytic reaction? Anyone who has had an automobile engine that continues to run can tell you that a spark plug can stay hot enough to ignite the fuel. This is in fact the same thing that Ray Arden discovered.

w8ye

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Sport, I think you will experience the non platinum engine to not have the throttle ability that you now enjoy?

Sport_Pilot

I'm guessing that this glow plug in 1907 or 1908 did not have a platinum element.

Sport_Pilot

Check the gasser forum, their experiments are that the problem is top end power more so than idle. By using hot plugs and a small amount of methanol they can achieve near spark performance. But the early glow engines could not idle no matter what the plug was made of. I think you may be thinking of iridium in plugs which made them last longer and helped the idle. I think Duke Fox did this first, not Arden.

speedster 1919

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W8ye Gee thanks for being polite too. I have not read the 2 cycle book ' but it is probably full of recollections. I guess these recollections are better. Our modern glow plugs are a compromize and a price point offering like every thing we buy. A better longer lasting plug could probably be made , but would most modelers pay the price ? Say it was $25 --how many would you get. I have read that Platinum was originally a goverment property and not to be sold or offered to civilians..........I have also read where 100% platinum wire was tried and did not work well....

w8ye

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Speedster you will find that C. David Gierke has all the proof and there are no recollections.

http://www.modelairplane.org/museum/bio/Gierke.pdf

You honestly should read the book whether you already know this or not?

Here you can read the important part without shelling out any coins for the book?

http://findarticles.com/p/articles/m..._n9433814/pg_2

And here's what it says.....

NM2K

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There was a time when any comment made by Mr. Davis of DDD was considered as written in stone by the model mags and many modelers.

Mr. Gierke seems to have also been blessed with the ability to walk on water as far as many modelers are concerned. I have heard his name mentioned in reverent tones for many years now. I do not recall ever reading any of his utterances that I disagreed with. Not once. Ditto Mr. Davis.

Is Dave a licensed/degreed mechanical engineer? Knowing several people that I consider to be engineers that do not hold degrees in said field(s), I'm not one demanding that he have a degree in engineering, but it would help me understand how he arrives at his conclusions. This is not meant as an attack on Dave personally (or Bob).

Does anyone know Dave personally? If so, can you tell us a bit about him?


Ed, NM2K

w8ye

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He is something at a college around the Buffalo NY area. He is an instructor or professor of internal combustion engines to the best of my knowledge.

Here are some other articles he has written for Model Airplane News

http://findarticles.com/p/search?tb=...%2C+C+David%22

I guess he must be a high school trades teacher or was at one time? this quote is from the Model Aviation Hall of Fame epistle (1978)He is 66 years old now and probably retired?

NM2K

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


Before my Dad moved the family from southwest Virginia (Marion) to Pennsgrove, NJ, he used to work at a sawmill that was powered by a Ford flathead V-8 car engine. The engine was started when the foreman arrived at work in the morning and stayed running all day long, sawing up lumber.

He said that when it came quitting time, they used to turn off the ignition, but the engine just kept running. They would have to stall it by running it into a larger than normal log, just to turn it off for the night. Next morning, it would fire right up again with the ignition on.

I have never seen anyone successfully start a glow plug equipped engine on gasoline and oil fuel. I've seen quite a few folks try. I've also seen the engines catch fire from their efforts. I'm not saying it can't be done - just that I've never seen it. An electric starter might make it a lot easier to accomplish.


Ed Cregger

NM2K

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Thanks, Jim. That was a big help.


Ed, NM2K

speedster 1919

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This will be my last post here. You read the hypes here and there and it sounds like a manufacturer purposely added iridium and rhodium to the alloy when in realality they are natural part of industrial grade platinum. The highest platinum content I could find was 60% in a 4 stroke plug. The way I look at the glow plug is if it was a true catalytic reaction . That I would take a platinum glow plug and drop in a gallon of new glow fuel and run like mad to get away from explosion or massive fire. I deal with body shop paints, resins , glues that use true catalytic reactions. I look at a glow plug as an ignition source that glows and produces heat to ignite the glow fuel. And a stainless steel element would work fine for an element but would oxidize and disintagrate faster and not last as long. The quote I found above says nothing about a catalytic reaction and the 300 degree less temp was in a full fledged diesel engine and we are dealing with semi diesel engines , so It may not be a good comparison..........

DarZeelon

Randy,


The higher the ambient temperature, the faster and more intense any chemical reaction becomes.

I am talking about VERY much faster and more intense.... not percentage points.


If you do as you described and put a glow plug into a jug of fuel at room temperature, it may take the plug about a week to increase the fuel's temperature by 1°F...
So, you don't need to run that fast...

The plugs glow element is ~0.05 mm in diameter and its stretched length is about 2 cm, so it is about 0.00002 cubic centimeters in volume and its weigh, even with platinum's high density of about 19, is just 0.0004 grams. A gallon of fuel weighs about 3,000 grams, or 7,500,000 times heavier than the glow element.

Even in a higher ambient temperature, with the resultant accelerated catalytic reaction, it will take very long for the fuel to reach its spontaneous ignition temperature...

... Even a flooded engine, with just a minuscule amount of fuel in the chamber, will not fire on its own. The rich mixture will dowse the element and not allow it to glow, or even to heat up noticeably.
Even if the mixture is perfect, an engine is unlikely to self-start (except for very rare cases).
The glow-driver is required to provide initial ignition AND to bring the glow-element to a temperature that would bring the reaction intensity to such a level, that the glow will be self-sustaining, in the presence of very hot methanol vapors.