Nitrometan, da boste vedeli.........

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Nitrometan, da boste vedeli.........

OdgovorNapisal/-a ELO » 02.01.2003, 11:34

FACTS ABOUT FUEL No. 3 - Nitromethane, the Mystery Ingredient?

(The following is the third in a series of articles exploring all facets of model engine fuel. The writer is Don Nix, Past owner of Powermaster

Nitromethane…..everybody knows it's there, but few, it seems, really know much about it. Although most seem to know - at least vaguely - that's its primary purpose is to add power, we still get an occasional call or letter asking, "Why do you use it in model fuel?" At best, there is much misinformation regarding this somewhat exotic ingredient. Let's see what we can do to clear some of it up.

Nitromethane is just one of a family of chemicals called "nitroparaffins." Others are nitroethane and 1-nitropropane and 2-nitropropane. Nitroethane can be used successfully in small quantities. (Top fuel drag racers, which generally run on straight nitromethane, sometimes add a little in hot, humid weather to prevent detonation.) At one time, nitroethane was only about half as expensive as nitromethane, but its cost now is so nearly the same, using it to lower cost is hardly worth the trouble. Neither of the nitropropanes will work in model engine fuel. Incidentally, nitromethane is made of propane, in case you didn't know (and I'll bet you didn't).

Yes, NITRO = POWER! But….there are conditions and contingencies. First of all, it doesn't add power because it's such a "hot" chemical. Not at all. This may come as a surprise to most readers, but the methanol (methyl alcohol) in the fuel is by far the most flammable ingredient….nearly twice as flammable as nitromethane. As a matter of fact, if nitro were only 4 degrees less flammable, it wouldn't even have to carry the red diamond "flammable" label!

In actuality, nitromethane must be heated to 96 degrees F. before it will begin to emit enough vapors that they can be ignited by some sort of spark or flame! (I demonstrated this not long ago to a friend by repeatedly putting a flaming match out in a lidful of nitro. I might add that he insisted on standing about 20 feet away during the demonstration.)

So….how does it add power? We all know (I think) that although we think of the liquid part substance we put in fuel tanks (in our automobiles or model airplanes) as the fuel, in truth, there is another "fuel," without which the liquid part would be useless. Remember what it is? Right….just plain old air (in reality, the oxygen in the air).

Every internal combustion engine mixes air and another fuel of some sort….in our case, a liquid…glow fuel. The purpose of the carburetor is to meter those two ingredients in just the right proportions, and every individual engine has a requirement for a specific proportion of liquid fuel and air. Try to push in too much liquid without enough air, and the engine won't run at all. That's the purpose of the turbocharger on full-size engines….to cram in a lot more air than a simple carburetor or fuel injection system can handle.

Now…..suppose we were to find a way to run more liquid through our model engines without increasing the air supply? That would add power, wouldn't it? Well, guess what….we can! An internal combustion engine can burn more than 2 ½ times as much nitromethane to a given volume of air than it can methanol. Voila! More Power! That's how it works, and it ain't all that complicated. Nor do we have to spend a lot of time thinking about it in the course of a normal day's sport flying.

However, there are some factors we do need to consider. As a practical matter, virtually all our everyday sport flying can be done on model fuel containing from 5% to 15% nitromethane. If you're flying something like a trainer or a Cub or similar model, there's probably no reason why 5% won't work perfectly well. Need a little more power? Move up to 10% or 15%. In most of our sport engines today, I really wouldn't recommend going any higher than that. It probably won't hurt anything, but it won't do you much good, either.

We sell more 15% fuel than any other single blend, and for good reason. Most of the popular engines on the market today are built to run on something very near that blend. Typically, European engines will successfully run on lower nitro blends, because they are built to do so. Why? In Europe, nitro can cost between $150 to $200 a gallon! Reason enough?

Nitro does more than just add power. It also helps achieve a lower, more reliable idle. One good rule of thumb for checking to see if a particular engine needs a higher nitro blend is to start the engine, let it warm up for a few seconds, set throttle to full idle and remove the glow driver. If it drops rpm, move up to a 5% higher nitro blend. If there is no discernible drop, you should be fine right where you are.

One of the most popular misconceptions is that by adding substantial nitro, the user will immediately achieve a huge power jump. Just ain't so. Most will be surprised to learn that in the 5% - 25% nitro range, you will probably only see an rpm increase of about 100 rpm static (sitting on the ground or on a test stand) for each 5% nitro increase. In the air, it will unload and achieve a greater increase, and it will probably idle better, too.

My pet rule is this: If you have a model that's doing well, but just isn't quite "there" powerwise, go up 5% in nitro. If that doesn't do it, you need a bigger engine, not more nitro!

Most of our popular sport engines in use today aren't set up to run on much more than 15% or 20% nitro. Increasing the nitro has the effect of increasing the compression ratio, and each specific engine has an optimum compression level. Exceed it and performance will probably suffer, not gain, and the engine will become much less "user friendly."

High performance racing engines, for example, are tuned entirely differently….compression ratio, intake and exhaust timing etc….and are usually intended to run on much higher nitro blends. One exception, of course, are racing engines used in certain international and world competition (FAI). By the rules, these engines are not allowed to use any nitro at all, and they go just as fast as those that run on 60 or 65%! The first question that comes to mind, then, is, "Why aren't all engines designed to run on no nitro, so we can all save a lot of money?" Ask any of the world-class competitors. Those engines are a serious bitch to tune and run, and are definitely not user-friendly! In fact, they are well beyond the skill levels of most average flyers. There's a price to everything.

Another statement we read or hear frequently is that nitromethane is acidic and causes corrosion in engines. It isn't acidic, and the manufacturers say it doesn't happen…..can't happen. However, at least one noted engine expert and magazine writer insists that it does. Flip a coin. (I once asked Dave Shadel, 3-time World Pylon Champion, and a fellow who works on more high performance engines than anyone I know, how frequently he encounters rust in engines that have been using high nitro blends. His answer? "Never.")

Why does nitro cost so much? While I have no clue as to the cost of manufacturing, other than it takes a multi-million dollar investment in a large refinery to produce it, there is one pretty good reason: There is only one manufacturer of nitromethane in the Western Hemisphere. Figure it out for yourself.

Also (and this will come as a big surprise), our hobby industry only consumes about 5% of all the nitromethane produced; and full-size auto racing about another 5% or so. This means we have no "clout" whatever, and simply must pay the asking price. Where does the rest of it go? Industry. It's used for a variety of things - a solvent for certain plastics, insecticides, explosives (yes, it was an ingredient in the Oklahoma City bombing) and I'm told it's an ingredient in Tagamet, a well-known prescription ulcer medication (no wonder that stuff is so expensive!). Please note that while nitromethane is an ingredient in making some explosives, under normal use, it in itself, is not exploseve. (Remember….the guy used fertilizer, too.)

Hardly a month passes that someone doesn't call to ask, "I hear more nitro will make my engine run cooler. Is that true?" Nope. The higher the nitro content, the higher the operating temperature. Fortunately, in most of our sport engines, the difference in operating temps between 5% and 10% is negligible, and there are lot of other factors (proper lubrication, etc.), that are much more important.

Finally, remember in the beginning of this, we said that nitro adds power because we can burn more of it than we can methanol, for a given volume of air? This also means that the higher the nitro content of the fuel, the less "mileage" (or flying time) we will get. In a typical .40 size engine using 15% nitro, we can usually get a minute to a minute and a half flying time for every ounce of fuel. The Formula 1 guys are lucky to get 2 minutes out of an 8 oz. tank!

What's the practical side of this? If you go to a higher nitro blend, be sure to open your needle valve a few clicks and reset before you go flying. Otherwise, you'll be too lean, and could hurt your engine. Conversely, if you drop to a lower nitro blend, you'll have to crank 'er in a little.
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OdgovorNapisal/-a ELO » 02.01.2003, 11:37

ŠE NEKAJ O SINTETIČNEMU IN RICINOVEM OLJU


FACTS ABOUT FUEL No. 2 - Which Oil is Better - Synthetic or Castor?

(The following is the second in a series of articles exploring all facets of model engine fuel. The writer is Don Nix, Past owner of Powermaster, Inc.

Before we get started on the subject heading, I'd like to offer a couple more thoughts on last month's subject, "What's the Oil Content?" - thoughts that have been remembered since writing the original column:

Many modelers who have been involved in the hobby for a long time, including those who've been away for years and recently returned, are very stubbornly remembering when model fuel just about had to contain something in the order of 25% oil - usually all-castor - and have a hard time dealing with the idea that virtually no one runs that much any more in modern engines.

The operative word here, of course, is "modern." The metallurgy in today's engines barely resembles that of a generation ago. The end result, as far as model engines are concerned, is that the engines today simply don't require as much lubricant - not nearly as much. I will be quick to add that those running antique engines in Old Timer events should certainly continue to use the old-time formulas - no doubt about it.

In addition to vastly improved metallurgy, we must remember than manufacturing techniques barely resemble those from years ago, in many ways. Modern CNC machinery has made it possible to routinely and cheaply make 1 or 1 million parts all exactly alike.

Those of you who have come along in later years may be shocked to know that up until the advent of this new technology, every piston was hand fitted to every liner. There was no such thing as simply machining 1,000 pistons and 1,000 sleeves, picking one from each batch and having them fit.

The belief in those days that some engines of the same size and make were markedly hotter than others was no doubt true. We've read that in those days, a .29 for example, might vary from as low as an actual .26 to a .32 - some 23% more displacement! More closely controlled tolerances have resulted in the ability to use much different fuels than a generation ago.

The second thought on the subject of total oil content came from reading the operating instructions included with a new imported 4-stroke engine - the DAMO FS 218 twin. It recommends a fuel containing 94% methanol, 5% nitro and 1% Castor Oil! Clearly, this reinforces my point that "there ain't no such thing as a fixed percentage of oil content." Now….on to this month's subject:

Before we depart the subject of oil in model fuel, let's talk about a point that's argued vehemently all over the land - Which kind of oil is better - synthetic or castor?

Each side has its very strong proponents, and each side is right….to a point. "Old-timers" tend to still favor an all-castor fuel, or at least one containing a liberal amount of castor oil. Modelers who have come to the hobby in the last 15 or 20 years have a strong affection to synthetic oils, or at least want their fuel to have mostly synthetics. Let's take a look at both types statistically:

SYNTHETIC OILS

Strong Points
Weak Points

Good Lubricity (It's "slick") Most tend to cause corrosion if adequate inhibitors aren't added.
Little to no carbon or vanish buildup inside Burns off surfaces at about 100 degrees lower temperatures than castor oil
Leave less oily mess on models Many types and qualities, making it hard to choose the best one
Available in a variety of viscosities Expensive - good ones cost almost twice as much as castor oil, increasing the cost of the fuel.
Totally soluble in nitromethane When used as the sole lubricant, a greater quantity is required, which increases the cost of the fuel.

CASTOR OIL

Great Lubricity Tends to cause carbon and varnish buildup in engine if cheap grade and/or too much is used.
Reduces the amount required, resulting in more power and better idle. Messier on model than synthetics
Will tolerate internal temperatures about 100 degrees higher than any synthetic Somewhat sensitive to extremely cold temperatures - mild separation in solution, residue on model becomes almost "buttery" in consistency.
Almost 50% cheaper than good synthetics -
reduces cost of fuel.
Insoluble in nitromethane. In solutions above 40% - 50% nitro, will separate unless some sort of co-solvent is used.
Great natural rust and corrosion inhibitor Generally available in only one viscosity

I'd like to insert here that there is a "Chicken Little….The Sky Is Falling" rumor making the rounds on the Internet these days that the manufacturers of castor oil have recently changed their methods of making the product, and the castor oil we are getting now is either wholly or partially incompatible with methanol.

I have talked at some length with the "Head Techie" of one of the largest castor oil importers in the U.S., and I want to go on record as saying that, according to the best information I can find, This is total B.S. The Head Techie actually laughed out loud when I told him what was going around. He said, "You know, there isn't much we do to the stuff. We press the oil out, filter it, grade it and package it. As far as I know, nothing has changed." It apparently started with one of the fuel manufacturers. For what reason, I have no idea, unless it's to help them promote their proprietary synthetics. (Incidentally, I have read a response on the 'net from SIG, agreeing with the fact that it's nonsense.)

So…..there you have it. "You pays your money and takes your choice." Actually, it's a little better than that, and the obvious answer is - use a combination of the two, in proportions that will come nearest to enjoying the benefits of each, while minimizing the adverse characteristics.

A few years back, the modeling community was in a "synthetic oil frenzy," and the swing was toward all-synthetic fuels. Happily - at least in this writer's opinion, we've seen a very noticeable swing back toward the center, with the majority seeming to prefer a synthetic/castor blend. We think this makes sense, and many years experience proves it.

The most frequent comment I hear from lovers of all-synthetic fuels is, "Brand XX leaves a lot less oil on my model." My response to that is, "Doesn't that bother you? If you don't see much oil on your model after flying, that tells you one of two things - or both: Either there wasn't enough oil in there in the first place, or the oil is burning off with the methanol. Neither is good. There's no way oil can burn off and properly lubricate at the same time." This is usually met with a puzzled look, then one of the light dawning, having just realized something they never thought of before.

Oil residue in model engines is a natural as barking is to a dog. We have to learn to live with it.

As an aside, not long back a friend sent me a copy of an article published in a European model magazine. In one part, the writer stated, "The Americans are the only ones rich enough and dumb enough to use synthetic oils." Perhaps overstated just a bit, but it has some validity.

There a couple of types of engines that do require an all-castor fuel, or at least one with a considerably higher castor content than most others. One would be the Fox ringed iron piston type, and the other would be the small Cox engines, because of their rather unique ball-and-socket connecting rod-to-piston design.

Pattern flyers traditionally prefer an all-synthetic fuel, for a couple of reasons, I think. One is the fact that pattern flyers practice a lot - hour after hour after hour. That much use, plus the tuned pipe setup that is almost universal with them probably, tends to cause a greater problem with varnish and carbon buildup than in sport types. (At the risk of bombarded, I also think it's largely a state of mind. "Joe Champion uses all-synthetic, so that's what I'm going to use.")

The other area where we have seen all-synthetic fuels gain in popularity in recent years has been with model helicopters, probably for the same reasons. Also, the trend toward 30% nitro fuel for serious competition has led to using a lower viscosity lubricant, and, as shown in the comparison charts above, this necessarily dictates using synthetics.
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OdgovorNapisal/-a 2Fast&2Furious » 02.01.2003, 13:08

Ufffff........ :P :P :P

L.P. HABY :twisted:
2001-Državni prvak v kat 1:8 Rally Junior
2001-Podprvak v kat. 1:8 Junior Off-Road
2002-Podprvak v kat. nacional
2002-Mantua prvak v kat. 1:8 junior rally in 1:8 junior off-road
2003-Državni prvak v kat. 1:10 200mm
2003-Podprvak v kat. 1:8 Off-Road
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OdgovorNapisal/-a 1FastDude » 02.01.2003, 19:30

elo,

še nekaj dni nazaj si govoru da to ni res :?:

hladi motor ??? kje pa to piše

lp Uroš :D
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OdgovorNapisal/-a ELO » 02.01.2003, 19:49

kaj od tistega kar sem govoril ni res???? Povej, da ne umrem zaveden....

a to da hladi?
ker to je namreč res! Hlapenje in to povzroča boljše mešanje, niža se temperatura oz. veča se temperaturna razlika, nekaj se spremeni kompresija (višji srednji tlak),....... vse to pa pripomore k povečanju moči ali izkoristka...
AMPAK, hladi se mešanica goriva, ne pa motor kot celota!



pa še to, baje se v mešanico pozimi dodaja tudi aceton (ne vem v kakem procentu), namreč naj bi svečka bolje žarela pod nizkimi vrtljaji v mrzlem zraku. sam tega nisem sprobal, tako da žal ne vem......
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OdgovorNapisal/-a ELO » 02.01.2003, 20:15

da pa boste sploh vedeli v kaj bezate si dejte najprej malce pogledat sledeče:

kaj se sploh dogaja v motorju:
http://www.rawbw.com/~xmwang/myGUI/OttoG.html
http://www.shermanlab.com/science/physi ... ieselG.php

podkrepljeno z amlce več teorije o termodinamiki:
http://hyperphysics.phy-astr.gsu.edu/hb ... yc.html#c1

tudi to je zelo zanimivo za pogledat:
http://www.ecr.mu.oz.au/~mbrear/436-352 ... ngines.pdf

še nekaj malega o tem iz kje izhaja izkoristek:
http://www.doane.edu/crete/academic/sci ... D/otto.htm

No ja, pa da v določenih zadevah ne boste iskali vaša dva manjkajoča takta :lol:

l.p.
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OdgovorNapisal/-a ELO » 02.01.2003, 20:21

ej, Haby, to je nekaj zate a?

FIZIKA :shock: :shock: :shock: :shock: :shock: :shock:
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OdgovorNapisal/-a 2Fast&2Furious » 02.01.2003, 22:45

:idea: :idea: :idea: ELO res hvala :roll: !!! Lih zame ja :wink: :!:

mej se

L.P. HABY :twisted:
2001-Državni prvak v kat 1:8 Rally Junior
2001-Podprvak v kat. 1:8 Junior Off-Road
2002-Podprvak v kat. nacional
2002-Mantua prvak v kat. 1:8 junior rally in 1:8 junior off-road
2003-Državni prvak v kat. 1:10 200mm
2003-Podprvak v kat. 1:8 Off-Road
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OdgovorNapisal/-a 1FastDude » 02.01.2003, 23:49

ne hladi motorja, sam to sem hotu rečt,

VEČ NITROMETANA --> VEČJA MOČ --> VEČJA TEMPERATURA Se strinjaš ???

velikokrat sem že slišal od različinih modelarjev da nitrometan hladi motor pa je vse skup prešlo v neskončno debato....

luštno branje za mrzle zimske dni.

podobno se dodaja tud peroksid, sam za to pa ne vem čist prave obrazložitve

še kakšen fizik s svojim mnenjem? na plano

lp. Uroš
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OdgovorNapisal/-a ELO » 03.01.2003, 00:30

ja ja, se strinjam!

ampak hudič je v detajlih......

je dobro vedet kaj in zakaj. včasih se vpraši ZAKAJ pa bo.
Nitrometan služi (tudi) za hlajenje. Ampak mešanice, ne pa motorja. Nekdo je to slišal pa si narobe razložil.......

Naj mi nekdo skuša odgovoriti na tole vprašanje:
Motorji se bolj vrtijo in dosegajo večje moči če jim zmanjšamo dotok goriva. Zakaj je to tako????? kaj ni bolj logično obratno???
prosim, da vidimo..... 8)
zdej veste zakaj imajo vaši 1:1 avteki po čip tuningu manjšo porabo goriva...... pa ste se spet nekaj naučili, a ni to lepo?

glede peroksida, pomoje nekaj podobnega kot acetilen v acetonu. ne vem, to je samo moje mnenje.
zaloga kisika----->več dovedenga kisika----->možno dovesti več goriva--->več pridobljene energije--->več moči----->.........---->PREJ TREBA LEŽAJE MENJAT :?

HEHE, sem premalo spil da bi to lahko bolj "fizikalno" razložil.
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OdgovorNapisal/-a Fisher » 07.01.2003, 23:22

Hmm ce jaz prav to razumem in ce se prav spomnim je to posledica redkejse mesanice bencin zrak, posledico prihaja do vecijih temperatur, in vecja kot je razlika v temperaturah vecji je izkoristek. Hmm sam ce pretiravas dobis luknjo v batu tako da to je dvorezen mec :) Popravi me ce sm se zmotil
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OdgovorNapisal/-a 1FastDude » 08.01.2003, 08:07

jep, to bo to ...
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OdgovorNapisal/-a ELO » 08.01.2003, 08:14

moj tanovi motor ima že serijsko dve luknji v batu!
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OdgovorNapisal/-a Fisher » 08.01.2003, 09:31

Ja ma ne na celu :))) pri straneh ma veliko batov luknje
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OdgovorNapisal/-a ELO » 08.01.2003, 10:51

:lol: :lol:

dobr, a ne?
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