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View Full Version : Why a 97 or a 100 Cube tank really holds 87


critter99
01-27-2017, 07:14 PM
http://courses.washington.edu/bhrchem/c456/vdwgas.pdf

http://courses.washington.edu/bhrchem/c456/vdwgas.pdf

"When considering real gasses, this equation of state needs to be modified. It is
interesting to think about how the modification should be done. The first person to
suggest how to modify it was van der Waals. He proposed two modifications of the I.G.
equation to include molecular interactions. The first modification is to realize that
molecules take up space. This means that the accessible volume is reduced by the
amount of space each molecule takes up. The first correction to the I.G. is to try an
equation of state of the form:"



The math is way over my head ....I am practical they aint gonna make a non fire industry standard tank size for a small air rifle market dealer even in Korea

I never get the predicted amount they fill tank 4500 PSI it loses 250 PSI over night from cooling. Fill calulators dont account for fill fittings and hoses etc. I never get what they say

Remember you do this for fun ....just makes me sorta of mad that people get deceived that one is bigger than another by some mythical significant amount when between brands of tanks the the variance is negligible.

Next one get the USA one size and pricing is the same and the quality is better and it employs Americans

critter99
01-27-2017, 07:18 PM
internal volume/water volume is the only one you can compare

The main column label ya want on the other post is the second from left....compare that to the below major sources of tanks in US

So the INOCOM chart lists an internal volume of 416/418 how does that compare to the Big 3 stated capacities?? It has nothing to do with reserve capacities of air. Air does not compress like the simple math shows above 3000 psi. Multiplying internal volume times fill pressure and converting to cubic feet does not get you accurate capacity above 3000 PSI. That is why the biggest tank maker in country says 65 cubic feet of air fits into a 418 CI internal volume tank.

At least INOCOM is from Korea not China but I can easily get a US made one from a tank specialist and not an air rifle dealer that started the capacity wars to try and grab market share. I see they now list 550 CI tank at 100 cubic feet now on their website....Do you think INOCOM changed the production line to make them exclusive oddball sized tanks?? I will point out they fail to show the DOT spec label in their ads. Post a shot of your "75" tank DOT Label I bet the REE hydro test number is the same as my 66/45 min SCI tanks label


Think of it like the nonstandard audio amplifier power wars lies in 70S....yea the amp makes 125 watts but at 25% THD....really at usable THD levels the amp was 63 watts or so...


LUXFER


http://i941.photobucket.com/albums/ad257/critter99/cascade/joe4luxfer_zpsc54d7d94.jpg

SCI
http://i941.photobucket.com/albums/ad257/critter99/cascade/joe5sci_zpse5e3e46c.jpg



Cobham
http://i941.photobucket.com/albums/ad257/critter99/cascade/joe6cobham_zps930a3ccc.jpg

critter99
01-27-2017, 08:03 PM
550 CI is the internal volume 87 or 88 is the capacity of air that fits inside 550 CI once you account for how air compresses above 3000 PSI

the inflated 97 or 100 cube feet is because they do simple math and do not account for the way air compresses above 3000 PSI

One dealer ignored the real calculation and the rest(the guy selling quality USA tanks) followed suit to not lose sales to the 1st dealer whom claimed to have a 74 Cubic Feet tank

You guess who started the questionable non standard statement of tank sizes they sold this brand of tanks



http://i941.photobucket.com/albums/ad257/critter99/cascade/inocom_zpsninzizke.jpg

http://i941.photobucket.com/albums/ad257/critter99/cascade/Document2_2_zpsa2a5b785.jpg

grumpy
01-27-2017, 08:49 PM
Thanks for the most informative post sir. If you won't name the companies, I will :)