Why methanol instead of ethanol (or proponal or butanol, pentanol, etc.)?

On Mon, 19 Feb 2007 12:27:34 -0800, "Ook" wrote in :

Looks like ethanol has more btu than methanol:

I'll bet it's the consumability that restricts production. Folks would have to swear up, down, and inside out that none of the product would be used as a beverage. As soon as the beverage laws come into effect, you've got a zillion food purity inspectors and tax collectors to deal with.

Marty

"Martin X. Moleski, SJ" wrote

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What about the catalytic reaction that allegedly occurs between methanol and one of the precious metals in/on the glow plug element? It is my impression that this is why the glow plug retains its heat once the voltage is disconnected.

Ed Cregger

On Mon, 19 Feb 2007 18:44:48 -0500, "Ed Cregger" wrote in :

GACK!

Right.

And someone mentioned that just last week, too.

The ethanol/methanol page I mentioned is talking about cars with spark plugs, not glow engines.

Marty

(1) Check out the stoichiometric balance of air:fuel for methanol and ethanol, their density, and BTU per pound. I'll do the same at work tomorrow, actually I am interested to see which comes out on top.

(2) 4 ounces of gasoline, salt, drain cleaner, or cough syrup ain't too good for you either. Don't drink glow fuel all I can say.

(3) Don't waste precious ethanol on model airplane engines (hic)!

Methanol is indeed cheap to produce. Ethanol is reasonably cheap too, but is afaik produced in volumes a fraction of that of methanol.

Methanol is made from methane, also known as natural gas. Natural gas is so abundant that they pump it back into the ground in a lot of places.

methanol has the correct catalytic effect with the platinum glo plug: ethanol I think, does not. Methanol is cheaper.

There is one and only one reason to use methanol. That reason is it allows you to stuff more carbon and hydrogen and less air into the combustion chamber then any of the other alcohols thus getting the most power out of your engine. You can get even more power out by going to higher and higher nitro methane contents of course and that is the reason so many fuels contain nitro. So it all has to do with stuffing the most BTU potential into a given volume of cylinder space. With either methanol or nitro you are using the fuel to carry part of the oxygen needed for combustion into the cylinder head thus reducing the volume of air you have to stuff in with the fuel to reach a stoiciometric ratio. Glacial acetic acid would probably make an even better fuel (I have not bother to run the numbers but it is a reasonable guess) but the stink and corrosion would be intolerable. A mix of methanol and formaldehyde would also be a better choice. Now you not only get stink but a lot of toxicity and a fuel that is not very stable on storage.

The glo plug has nothing at all to do with the choice. Glo plugs can easily be made that work with other fuels.

It has nothing at all to do with costs. Yes methanol is less costly then other alcohols. But not much less costly then ethanol made by the least expensive method which is NOT by fermentation. Both cost a buck and a half a gallon or some such. I do not have a current Chemical Reporter to look up the price. But both are far less per gallon then we pay for fuel. Industrial ethanol, which is not produced by fermentation, is quite a bit lower wholesale price then ethanol from fermentation produced for auto fuel. But our government passed laws that dictate that ethanol used as motor fuel MUST be produced by fermentation. The only reason for this law is it is a subsidy to our farmers. There is no scientific reason. Most of the cost of glo fuel is packaging, transportation, advertisement and profits for all the folk that own it before you burn it.

Surely, in the beginning, the catalytic reaction between the glow plug element and the methanol was of importance. Most likely it was discovered by a lay person, not a professional, and it remained popular because of the lack of attention our engines received from those with the funds available to explore alternate fuels/catalysts. Your point may be absolutely correct, today, but I think that initially the reaction was of key importance in the beginning.

It would be nice to be made aware of other possible fuels and the elements with which they react in a favorable manner.

Ed Cregger

Methanol is WOOD alcohol. Ethanol is GRAIN alcohol. Totally different animal!

Ed,

I have honestly not bothered to dig into history and get all the development stuff. I expect glo plugs came right out of diesel engine technology which was all developed by professionals. And at that point the question for models was how do we stuff the most BTUS thru the combustion chamber per cycle and at the same time use a fuel that is dirt easy to handle and store, non toxic as fuels go and shelf stable. Methanol was the easy clear choice to make. Once you pick methanol you go back and optimize the glo plug. etc as needed to run on that fuel.

There are other choices. For instance it would be easier to make a glo plug to run on acetone. You do not even need any precious metal as a catalyst. Plain old copper would work just fine as a catalyst. But you could not cram as many BTUs thru per cycle with acetone as fuel, it is more volatile then methanol so evaporation would be a bigger problem and it is more corrosive then methanol. It also is not any cheaper.

Or you could simply run on plain old gasoline. It should not be hard at all to make a glo plug that would work with gasoline. Again less BTUs per engine cycle so less power output.

In short there is not a thing magic about methanol. Any number of fuels could well be used. You would have to change the carberation, the glo plug characteristics and compression ratios for the different fuels . And in almost every fuel choice you could make you would wind up making less power then you make with methanol. Those few choices that could make more power have real problems from a practical standpoint. Problems such as stability, corrosivity, toxicity and stink. It should not be a big trick to retune an engine to run on 80 or 90% nitro if you need more power output per engine cycle and does not even add toxicity or stink yet no one bothers. Why not? I suppose because shortening engine life, higher fuel costs by a fair margin and less reliability are not worth it.

Why do so many people seem to think they can do better in their garage with stuff from the hardware store then people who know what they are doing and have spent lots of time testing and developing? For anyone who wants to experiment I suggest they first learn to calculate how many BTUs they are going to be able to stuff thru the engine per cycle rather then waste time on things that are going to be second best automatically. When they can stuff more BTUs though per engine cycle then it is time to actually start trying to tune an engine to run on whatever it happens to be. This shortens the list real fast and gets rid of ethanol and all higher alcohols, gasoline, acetone and just about anything you can buy over the counter. You are left with stuff you probably do not really want to deal with such as anhydrous hydrazine or glacial acetic acid or methanol with 35% formaldehyde. But if you really want to try those kinds of things you should be able to make one hot engine. I suspect you could really go like stink on a fuel of 90% hydrogen peroxide and anhydrous hydrazine. And you do not even need a carb as the thing needs no air. Better try the engine development stuff in a bomb room thou as you are going to fragment a few engines before you get one that runs.

Not really. They are actually very similar. Methonal is CH3OH, Ethanol is C2H5OH. It's a bigger molecule in that it has one more carbon atom, and 2 more hydrogen atoms. They can both be used as fuels, solvents, and will both intoxicate you. One major difference is how they are metabolized, in that methonal will break down into formic acid and formaldehyde, cause blindness, and death. Ethanol is not quite as toxic or dangerous.

wrote

Ray Arden "invented" the glow engine in the mid 40's. Nothing I have read about the man leads me to believe that he had any college education. He probably heard someone mention that there was a heat producing reaction between methanol and platinum/iridium (whichever - seems to be blurring over time - once it was thought to be the platinum), and went on from there. Most model airplane manufacturers began as garage/cottage industries. No large corporations existed to fund professional level R&D until Cox and a few others came along, much later.

If this is possible, I wonder why someone didn't pick up on it later, after the methanol burning engines were established. They would have made a fortune.

Because engineers dismiss our needs as being insignificant "small time" technological dead-ends. How many engineers will work for what Duke Fox would have paid them? None. Hell, I'm not an engineer and I wouldn't work for what he wanted to pay his business/shop manager a few years back. If "we" don't do the R&D, it doesn't get done. Yes, professional engineers would do the job much better - but they don't. Meanwhile, there are untapped markets and fortunes to be exploited - for a crafty individual - but not large enough to attract professional talent.

Don't tell folks what they can't do. Tell them what they CAN do...

Ed Cregger

It took me all of about ten minutes in my personal library to learn that precious metal filament glo plugs were used in diesel engines long before model airplane engines were ever invented. So I have no idea where the nonsense about some garage mechanic inventing glo plugs came from and do not really care.

I did tell you several options on what you can do if you want to play. You will not beat the combination of methanol, nitro and oil for any practical model engine and still get good horsepower out of it. But go ahead and try. I really do not care. If you want to try the things that will beat methanol based fuel pay up your insurance and keep away from sane people so you do not injure them. You had best have a good machine shop and the skills to use it also. Why not start with a by weight mix of gasoline and methanol in the ratio of 30 to 70? That is the equivalent of ethanol. It will not give you the power output methanol will give you but it will be cheaper and safe to handle. Just make up the mix, add some oil and you have fuel. I would think an off the shelf engine might run on it. You would probably have to change compression ratio to get it to run good. It will make less heat per unit of time then regular fuel so I think cooling would be ok. Or you might start with acetone. It will not give the power that you get from methanol either. But it is inexpensive, safe and available. Again an off the shelf engine likely would run on acetone without modification.

Now, if I were a pylon racer I would look into a hydrazine fueled engine. Expensive fuel but it is going to give great power. Likely to eat engines fast but that is ok. They only need to run good for a few minutes. Make the engine from ceramics and you might get around the corrosion problem.

The bottom line is real simple. Methanol is the best choice hands down. Want a bit more go add some nitro. If you went and spent fifty million bucks with Honda to do research that is where you will end up. If there were a better choice we would already be flying it. There are more then enough bright people in this hobby to have considered the alternatives many times over. It is very little beyond high school chemistry in terms of complex problem analysis. You basically want the fuel that carries as much of its own oxygen into the combustion chamber as possible or one the produces huge amounts of heat from a very small amount and uses minimal oxygen doing it. A diborane fueled engine would be interesting. Diazomethane would be a great fuel. I could probably come up with a dozen. All of which would either kill you from the fumes, risk an explosion in the fuel tank or eat the engine apart real fast. Liquid hydrogen and liquid oxygen would work well. NASA sends rockets into space with those fuels. They are unbeatable when it comes to energy per pound of fuel burned. Some rockets work well on hydrazine also. So you have lots and lots of choices.

Have fun.

On 20 Feb 2007 20:30:28 -0800, snipped-for-privacy@scn.org wrote in :

LOL!

Thanks for the review of the possibilities, costs, & benefits.

Much appreciated!

Marty

Sorry Ed, First glow plugs for model engines were introduced in the mid to late forties. A troop named Artie Horseblock (not sure of spelling) flew class A Speed UP-Control. At that time all the engines were ignition and the Bantam

19 was the hot eng>>

Oops - getting late and I'm not correcting the spell checker. Artie Horseblock should be Artie Hasselbeck - still not sure of spelling. UP-Control = U= Control. From there you're on your own ;-)

If all the was important was BTU per cycle, we wouldn't use an alcohol at all.

Gasoline or indeed benzene would be the choice..as indeed it has been for high performance racing engines where the more carbon you can cram in a molecule of fuel the better.

There are many reasons why methanol has been used in many engines..its cheap, it produces a lot of water vapour that cools engines down, and it reacts well catalytically with glo plugs.

Ceramic glow plugs in GAS - town gas==hydrogen and carbon monoxide - engines were common at the turn of the last century. They predate spark ignition engines.

There are three ways to ignite an IC engine that I can think of.

Pure compression ignition - diesel

Assisted compression ignition - a glo plug

Spark ignition.

Even a modern car diesel will use a glo plug to help vaporise the fuel for starting..

It so happens that compressing methanol in the presence of a platinum/iridium glo plug helps to keep the plug hot. The gas engine I saw did it just on pure engine heat.

You can get compression ignition in a gasoline engine with red hot carbon on the valves..'run on'

My guess is that methanol just happens to work well with platinum plugs, that's all.

TNP,

Comon TNP! I know you are a lot smarter then this. You were educated past tenth grade. Any engine runs on BTUs. Even a steam engine. All that counts is the BTUs per cycle and the relationships in the Clausius Claperon equations which define maximum efficiency. I am positive you know that.

You can easily make a glo plug that will work with any fuel you choose including plain old gasoline. There is absolutely nothing magic about methanol and glo plugs. Our standard glo plugs would work with a whole variety of fuels. Maybe not optimized for other fuels but they would work without question. After all, they are the same technology as a catalytic converter on your automobile. Cat converters do not burn methanol. All that has happened with our glo plugs is some minor adjustment to optimize performance. Or in the case of some manufacturers they skipped the optimization in favor of making them cheap. As I said before I could make a glo plug for acetone that did not even use precious metals. Something like a monel filament would work just fine. Monel is simply a copper nickel alloy that has excellent heat performance.

For any non believers about how easy it is with acetone here is a fun experiment. Put 25 ml of acetone in a 150 ml erlenmeyer flask. Take a copper penney and make a small hanger for it from copper wire. Heat the penny red hot and lower it into the flask to about an inch above the acetone surface. Sit there and watch the penny continue to glow red hot until the acetone is all used up. It will take maybe 20 minutes or more to burn all the acetone. What is happening? Simple. Air diffuses into the flask and acetone evaporates forming a gas mix that is below the combustable range of concentration. The gas mix will however react in the presence of the copper catalyst and oxidize making a lot of heat which keeps the penny hot.