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What fuel companies blend by weight instead of volume? - 3/30/2007 7:30:23 PM   
STG



Posts: 3498
Joined: 7/3/2003
From: New Richmond, WI, USA
Status: offline 		I am wondering what fuel companies measure nitro and oil on weight rather than volume & how to convert the weight blends to volume for comparison?



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RE: What fuel companies blend by weight instead of vol... - 3/31/2007 2:29:24 PM   
Hobbsy



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Joined: 12/2/2001
From: Colonial Beach, VA, USA
Status: offline 		To my knowledge only Byron's does it by wieght.

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RE: What fuel companies blend by weight instead of vol... - 3/31/2007 4:49:57 PM   
STG



Posts: 3498
Joined: 7/3/2003
From: New Richmond, WI, USA
Status: offline
quote:

ORIGINAL: Hobbsy

To my knowledge only Byron's does it by wieght.


Thanks, do you think both the oil and the nitro is blended by weight or just the nitro?

http://www.byronfuels.com/pages/about_oil_and_nitro.html

-------------
Here are the specific gravities I have found for the blends. I do not know that they are 100% correct.

Nitromethane is 1.13

Castor oil .96

Methyl alcohol 0.79

Synthetic oil?




< Message edited by STG -- 3/31/2007 5:02:23 PM >

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RE: What fuel companies blend by weight instead of vol... - 4/1/2007 12:03:16 AM   
Jim Thomerson



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Joined: 10/9/2002
From: Austin, TX, USA
Status: offline 		It is interesting, don't you think, that the high dollar components also have the highest specific gravity? Makes economic sense to blend by weight rather than volume. And if you say on the container that you blended by weight, it is in no way deceptive.

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RE: What fuel companies blend by weight instead of vol... - 4/1/2007 7:10:41 PM   
STG



Posts: 3498
Joined: 7/3/2003
From: New Richmond, WI, USA
Status: offline
quote:

ORIGINAL: Jim Thomerson

It is interesting, don't you think, that the high dollar components also have the highest specific gravity? Makes economic sense to blend by weight rather than volume. And if you say on the container that you blended by weight, it is in no way deceptive.



Well, if I did not see any mention that the blends were mixed by volume on the web site? I must be missing something? My largest concern is that there my be miss knowledge about % of oil.

quote:


Byron airplane fuels:
These fuels feature a wide range of nitromethane and oil percentages and are available in your choice of synthetic/castor blends or straight synthetic lubrication. Generally, a 16% total oil content is more than adequate for optimum performance and minimal parts wear. For those who feel more comfortable with higher oil percentages, we manufacture our Traditional Blends with 20% total oil content and our Premium 18 Blends with a total oil content of 18%.


If the specific gravity of the oil bend that they are using is close to 1 and they are only running 16% by weight, then by volume it is quite a bit less than most other companies and special 20/20 blends for YS users are not really what they are looking for?


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RE: What fuel companies blend by weight instead of vol... - 4/2/2007 10:54:49 PM   
jetpack



Posts: 1462
Joined: 10/2/2002
From: Portage, IN, USA
Status: offline 		What is the quality difference if they are making their batches by weight or volume? Does each individual ingredient fluctuate by its weight vs. its volume and thinking this is affecting the final percentage?

Are you asking if they check each basic ingredient before mixing for specific gravity to adjust thier mix ratios?

If mixing by weight, the varience from the specific gravity of 1 is compensated for in the mixing ratio percentage, and the end result is always put into volume units of a percent. The jug is sold in units of volume, and the label stays in those units when listing percentage. Mixed by weight it will be converted to its equal volume units.

There should be no difference in final percentages if a scale is used or a measured vat, just the mathimatical formula changes to compensate for its specific gravity.

What is more accurate between a scale reading or a volume measurement in final outcome is only dependent on its calibration accuracy.

Mixing by wieght or volume is a null point, unless you know either your scale or your vat is out of calibration makes you decide which one to use. The only thing is you have to compensate for the varience of its specific gravity, if that ever changes.

Measuring by weight is more accurate if the specific gravity is tested before each batch is mixed to allow for deviances in supply quality.

If a scale is used without testing gravity first before each batch, it is no more accurate than by volume.

< Message edited by jetpack -- 4/2/2007 11:22:37 PM >

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RE: What fuel companies blend by weight instead of vol... - 4/3/2007 12:31:05 AM   
Jim Thomerson



Posts: 2778
Joined: 10/9/2002
From: Austin, TX, USA
Status: offline 		jetpack, suggest you think about this some more. Read up on specific gravity, for instance, and do the math. This subject has been discussed many times on this and other forums, and people have run tests of oil content and verified that stated percentages were either by weight or by volume, depending on the manufacturer. As for me, I run fuel from a manufacturer who measures by volume, not weight. I was at the factory and I asked some one I trust.

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RE: What fuel companies blend by weight instead of vol... - 4/3/2007 1:30:21 AM   
jetpack



Posts: 1462
Joined: 10/2/2002
From: Portage, IN, USA
Status: offline 		So there's manufactures that assume each ingredient is the same weight and just use a 1:1 proportion in comparing and allowing the volumes to be different?

< Message edited by jetpack -- 4/3/2007 1:32:18 AM >

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RE: What fuel companies blend by weight instead of vol... - 4/3/2007 2:54:49 AM   
downunder



Posts: 3117
Joined: 10/10/2002
From: Adelaide, AUSTRALIA
Status: offline 		Mixing by weight is the slightly more accurate way given that when mixing by volume there'll be a tiny difference caused by expansion/contraction of the different ingredients in the small temperature range any sensible person would mix fuel. If the aim of mixing by the more accurate method is to get a resultant volume that we're familiar with at, for instance, 60F then that's fine. But if the aim is to mix by weight and simply state those percentages on the label to mislead into thinking it's the volume of each then that's bordering on criminal (IMO).

Specific gravities (densities) are always given at a certain temperature, usually either 20C (68F) or 60F (15.55C) based on pure water being SG=1 at 4C (it's maximum density).

As Jim mentioned, oil content has been tested on some suspect fuels and they've come up short on what would be expected if the label led you to believe it was the volume. Byron was one of them and where the label said it had 18% oil there was only something like 14% oil left after the volatiles (methanol and nitro) had evaporated away. Now going on STG's figures where oil has an SG of .96 and methanol is .79 then .79/.96 = .82 and .82 of 18% is 14.8% so an evaporation test is a good indicator.

Obviously you can't do an evaporation test to find out the actual volume of nitro but if the oil test is an indicator then a fuel with supposedly 15% nitro (SG=1.13) then it'll only have a volume of around 10.5%.

Things could really even be worse than this if the methanol is also prepared by weight because of its low SG. A certain weight of methanol would give a much larger volume than the same weight of oil and especially nitro.

There's a quick and easy way to get a rough idea of how much oil there is in a particular fuel as I found out some time ago. Pour some fuel into a graduated container like a medicine glass or burette to an exact mark (100cc is ideal) then add a small amount of water (it'll probably only need less than 5cc) and the oil will suddenly fall out of solution to the bottom. If the oil level is at the 20cc mark then it has 20% oil by volume. If it's markedly different to what the label indicated then it's likely been mixed by weight.

< Message edited by downunder -- 4/3/2007 2:56:00 AM >

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