I disagree Eagle Flyer. Just looking at bottle fillers, most are timed fill, or optical sensor filled. Either way, the margin of error regarding quantity filled per gallon jug will never be the same between two jugs. Is it accurate for filling jugs- yes, the machines are set to fill at least a gallon . So the possibly does exist where you get a little bit more.
Other filling machines exist but the ones mentioned are the most common.

If they are accurate and filling the SAME jugs with the SAME amounts of SAME ingriedients how can they be different? Are you saying they all contain the SAME EXACT amounts as they should but the jugs still come filled to different levels? If I were selling a product like this I would have equipment that does it right. Every time. Or I wouldn't have it. My opinion.

Are you guys trying to say that all 1 gallon jugs of the "same type" are dimensionally the same? I doubt it, just another error factor.

i know different manufacturing processes do have errors involved which cause "plastic" and fiberglass products to be dimensionaly different after all is said and done. Does this include the common fuel jug? Ok let's assume it does. Then that rules out the idea that all jugs are going to be filled the same. Also throws a monkey wrench into the process for the companies that use the optical sensors to control volume. So that means for it to be consistently accurate when going by volume it would have to be measured before it goes into the jug. If using timers then the preasure in the system has to be the same all the time. Also it takes longer for a bigger volume (expansion) of something to flow thru the same size controls compared to smaller volume(contraction) of the same ingredient at the same preasure.. Are these systems adjusted for different temperatures as to deliver the same volume at a given temp? Alot of things involved. Seems to me the bottom line is two things. Exactly how does a particuliar company control their bottling process and exactly what is the expansion and contraction rates of the ingredients being used? The later being the original question here. It's a Chevy Ford thing. But then we all know that Dodge beats them both anyway!

Why would anyone assume that the fuel mixing is done in the jug?? Whether by weight or by volume, this would be exceedingly difficult to get a reproducable mixture on a mass production basis. I would assume that batches of fuel are measured into a large mixing tank. After thorough blending, a bottling run would be done. Jugs may be filled by weight, by volume or by optical sensor. In the latter case, there could be some minor volume errors, but the composition would not be an issue.

There are lots of devices used to accurately measure liquid volumes - easier than by weight although possibly not quite as precise. Certainly it is possible to measure volumes accurately enough to produce mixes that are correct to within a fraction of a percent for individual components. I would also assume that if fuel component density varies significantly as a function of temperature, they would simply compensate for the differences on the basis of known (or measured) coeffecient of expansion. If a manufacturer did not have this basic level of control, I would suggest that they would produce a product that is inconsistant with respect to quality and concentration.

Bottom line - if it works for you, don't worry whether it is blended by weight or by volume; it can be done very well either way. If you get a "bad" jug of fuel due to reasons other than inappropriate storage (by you or your LHS), then steer away from that manufacturer!

Ross

We're assuming the company cares wheather the containers are all filled with exactly 1 gallon. This material is not that rare or expensive. I would geuss the margin for error is between .5 and 1%. The indutry has no critical regulation such as mil-spec or FDA to warrant the manufacturer to place such precise controls on the process which increases cost. Byrons costs more because they charge more and they make more profit. It could be better than the stuff I buy, but not twice as good. Byrons cost is double the brand I fly, Does my fuel have 14.99745% nitro or 15.00328%? I don't care, neither does my wallet.

Folks,
I was meerly pointing out that filling equipment is not necessarly "laboritory exact". I was not trying to stir things up. I disagreed with Eagles comment on placing a mark on the bottles for his above mentioned reasons.
Simple fact of the matter is that variences do exist, weather it be in the botteling equipment or the flex of the bottle if using optical measuring.
I would even venture to guess that at least one manufacturer puts an ounce or two more in the bottle just to make it look fuller than the competitions and to account for any fractional variences' in botteling machines or inconsistencies in bottles from batch to batch.

Bottom line is fellow fliers: whatever the variences involved, expansion coefficients, botteling, tempreture, etc... none of it will have a great enough effect on the finished product (assuming the manufacturer has consistent practices or quality controls in place) to tell the difference in the way an engine runs.

I've mixed my own fuel on and off for years and I can not tell the difference (and neither could the engines) between 19.75% oil and 20% oil or 20% nitro and 20.25% nitro. How does this relate? - Any fuel maker out there that puts their name on a bottle (or can) is certainly going to make sure that the tolerances in their product line are going to be within a certain fixed percentage, and I would assume that the variences' would be so fractionally small that anything but an extremely expensive laboritory test could determine the varience. I'm talking small fractions here such as .001%.

Now back to the original question of coeficients of expansion.
I searched a bit then got on the phone to a relative who is a chemical engineer. Although he did'nt have any data at his fingertips, he did mention that the compounds in question would have such a small expansion rate in the liquid form that it would be nearly impossible to measure in the tempreture ranges that blending would occur at (told him the temp ranges of 40-100 degrees farenheight). He did mention in his line of work, they are only interested in molecular weights (rathar than volume) since they are constant.

Sorry to ramble on guys. I guess I got a little caught up in the "off subject" part of the thread.

Dr. Nitro's on the money.

Somebody always has to be looking at the forest when the rest are looking at the trees....thank goodness!!!

There is only one reason as to why you pay twice as much for Byrons fuel. The lhs is charging that much for it. It doesn't cost that much anywhere else that I've ever seen and I travel all over the country and shop in a lot of those places. I have already seen where Byrons was the least expensive in the store. Retail prices on fuel are not set by the whole saler, only suggested retail prices are. And I'm sure they give price breaks for volume purchasing. Who doesn't these days. It only makes sense to. Helps keep the lhs loyal to a particuliar brand. there's a lot that goes on behind the doors in the land of buisiness that the public doesn't know simply because the less the consumer knows the easier it is for the companies to make a profit. I know, I work for a manufacturer.

Dr. Nitro, I couldn't agree more with your comments. I'd like to also add the following:

Do you think anybody can tell a noticeable difference between a fuel that contains 99.9% pure methanol or one that contains 99.5% pure methanol?

Do you think an engine will run noticeable better or different if the nitro is 99.95 pure or 99.7% pure?

I honestly can say I couldn't tell the difference and think that the best thing you can do to your engine is learn how to tune it and never run it lean.

Hauckf,

Had an idea... did you try emailing the various companies who make fuels and asking them for the coef.?

Cp140: I've asked two fuel manufacturers for that information. One replied that he didn't have the information, and one answered another question, but ignored the question about coefficients of expansion. If I knew who manufactured the methanol, nitro, etc. I would contact them, but I don't.

I don't know how much variation there is in the fuel we buy. As a manufacturing engineer with 37 years of experience, I do know that there is variability in every process involved in manufacturing fuel or any other product. That's why process and quality control are so important. I suspect that the variations caused by temperature differences in the blending process of glow fuel are insignificant, but it is an interesting question, and one that I thought I could answer to satisfy my curiosity. I'm still curious, and an still looking for those coefficients!

Regarding temperature, I'm pretty sure that the temperature of the air that the model flies in has far more impact on the performance of the engine than the temperature at which the fuel was blended, and I agree with the last few posters that a variation of a tenth of a percent or so in the percentages of nitro and/or oil in the fuel would have no significant impact on engine performance or longevity. My guess is that the quality and uniformity of the fuels from all of the the major manufacturers are good.

If I do have a ax to grind, it is with the one manufacturer who advertises and labels his product as 15% nitro and 18% oil, when the actual content is about 11.3% nitro and 15.6% oil by volume. Those differences I do think are significant. But then, that's just my opinion; I could be wrong.

At the risk of appearing maudlin, I'm going to also say this: I can remember a time when I would think twice about making a long distance call across the state to discuss an issue like this because of the expense. Now I can have discourse with people around the world (thanks for your input downunder!) for practically nothing. This is a freedom that is worth protecting. Let's all thank Al Gore for inventing the internet and RC Universe for providing this forum. Thanks to everyone who has responded, and keep those opinions coming!

Oh ya, I'M STILL LOOKONG FOR THOSE COEFFICIENTS!

And this I think is the point to the whole thread. Seeing I mix my own fuel (and being an Aussie anyway so I've never seen the brands mentioned) I can quite imagine someone buying a gallon of fuel that's cleary marked 18% oil and 15% nitro...but hidden right down the bottom in fine print it might say "calculated by weight". And that to most people wouldn't mean a thing.

As for the coefficients of expansion, that should be fairly easy to get a close idea by simply filling a length of clear tubing with about a metre of each fluid. If it's a cold day outside then leave it out there until it stabilises to the outside temp and measure the height of the fluid. Bring it inside and again let it stabilise and remeasure. It'll work just like a thermometer. All you need to know is the temp of the ambient conditions or if you've got a wire thermocouple then you can check the actual temp of the fluid. I think I might even try this

Al Gore has those coefficients I bet! In fact, I think he invented the internal combustion model engine too!!

:-)

Today, when I flew, it was cold. Is that why it seemed to take longer to fill the tank? Cause of that co efficient thing.

Downunder: I've also been trying to figure out a way to determine the coefficients experimentally. I think that the method you are suggesting would be complicated by the fact that the dimensions of the tube itself (length, diameter, etc.) would change with temperature, and the methanol and nitro would start to evaporate as soon as they were put in an open tube.

By the way, I put together a Microsoft Excel spreadsheet that does fuel calculations such as % by weight to % by volume, how much oil, nitro, etc. to add to up the percentage, combining two fuels, etc. I have a versions for Windows ME, and one for older windows versions. If anyone wants a copy, E-mail me direct.

Hauckf,

I thought you might have, but thought I'd suggest it anyway... I'm going to email my brother-in-law(an engineer in the oil industry)... see if he has any ideas.....

found it Thanks

Far too much misdirected energy.

Hauckf,
No luck asking my brother-in-law....