Lost in tank land, need help. Air Venturi/Ninja or Joe B. or...?

[Sfttailrdr46]

  At the end of the day as long as the tanks hold air at pressure and the accessories do the same the way I see it is if they all hold the same amount and the Ivory tower folks have pointed out the math errors or incorrect advertising for the world to see the rest is up to the buyer to follow the path they choose to purchase the product. Since becoming a member last year I have seen just about every product purchased by myself bashed or knocked by others on this forum, and at the end of the day the final decision was mine. Two very fine AG's that I purchased did not end up pleasing me in one way or another and have already been sold or will be sold. That is also MY choice, the threads are informative and serve to help me decide the choices made. So I guess what I am saying in a very long winded fashion is  liking or disliking a particular product  bases on no personal hands on remains opinion and will remain just that  "OPINION" . Once the opinion is based on hands on experience it becomes  reality 

[darrenf]

. Once the opinion is based on hands on experience it becomes  reality.

[Pedant mode] An opinion no matter what it is based on, is still opinion.   [/pedant mode]

[Sfttailrdr46]

. Once the opinion is based on hands on experience it becomes  reality.

[Pedant mode] An opinion no matter what it is based on, is still opinion.   [/pedant mode]

  I stand corrected so lets say it becomes an informed and knowledge based opinion

[PakProtector]

Now I am confused, If you call out Joe for his calculations being misleading:

AirTanksForSale 550 Cu In x 4500 / 14.7 /12/ 12/12 =97.43 Cu Ft.  I round down to 97 Cu Ft.

Why do you not call out Air Guns of Arizona for the same thing:

Airguns of Arizona 417 Cu In x 4500 / 14.7 /12/ 12/12 =73.87 Cu Ft.  They round up to 75 Cu Ft

I have, and by those numbers you posted clearly show AoA is doing the exact same thing. The AoA tank in fact being a 45 mins/66 cu ft tank misrepresented by a mis-use of Ideal Gas Law.

Go on, support dealers who misrepresent their wares...it hurts all of us.
cheers,
Douglas

[darrenf]

I stand corrected so lets say it becomes an informed and knowledge based opinion

There is no like button, so please accept this smiley.

[vigilandy]

Now I am confused, If you call out Joe for his calculations being misleading:

AirTanksForSale 550 Cu In x 4500 / 14.7 /12/ 12/12 =97.43 Cu Ft.  I round down to 97 Cu Ft.

Why do you not call out Air Guns of Arizona for the same thing:

Airguns of Arizona 417 Cu In x 4500 / 14.7 /12/ 12/12 =73.87 Cu Ft.  They round up to 75 Cu Ft

I have, and by those numbers you posted clearly show AoA is doing the exact same thing. The AoA tank in fact being a 45 mins/66 cu ft tank misrepresented by a mis-use of Ideal Gas Law.

Go on, support dealers who misrepresent their wares...it hurts all of us.
cheers,
Douglas

Oh great... I didn't know about AoA.  Until it was mentioned in this thread I had thought the AoA Omega tank I bought was 75CuFt. 

NOW it makes sense why it didn't seem much bigger than the 30minute SCBA tank I bought off eBay.  I looked it up and 30 minute tank = 45 CuFt.  I had figured it would be a lot smaller than a 75CuFt tank.  It wasn't that much smaller and now I know it is because the AoA tank is 66CuFt and not 75 Cu ft!

I had the SCBA tank hydrotested and resold.  Didn't take a loss, but it was a hassle.  I'm new to PCP and count me as one of the people who doesn't like these calculations.  Fool me once....

[Motorhead]

Go on, support dealers who misrepresent their wares...it hurts all of us.
cheers,
Douglas

Hurt 
One's EGO is about it on that one ... makes little difference what side of this debate you side with.  Issue here is that of differing opinion and that POLL of others thoughts on said formulas in question fueling a debate fire.
No safety ... Liability or HURT issues to anyone happening here !!! 

You would think such a heated debate as this would be viewed as POLITICS ... which clearly it is not far off from 
What this boils down too is Public Internet assassination of another persons view point and convictions of standing there ground who differ from others.


Don't mistake this as a Pointing of fingers from any side of this ongoing fight ... Got no dog in this fight, but do as a Member at large get darn annoyed with the bickering and finger pointing from both sides near every time such threads get posted.

I'm done 



*Spell correction made

[William]

The one thing you all forget is.... somebody else builds the tanks for each company and stamps that companies name on them, so if you shop around as far as tanks are concerned a 4500 PSI tank is just as good as the other guys! Fill Stations are generally made the same way! Well besides the point, my air venturi tank (90 CI) with fill station and regulated valve included from Pyramyd Air gets me about 12 fills on my Marauder and 2x that many on my Discovery. I have had no problems with my Air venturi tank or valve at all works great and very portable. I would rather drive 100 miles for a little bit of air than stand around pumping the stupid pump all day, especially on a Marauder at 3000 PSI. I want to enjoy shooting not die of exhaustion! lol

Link to a good tank and well worth the investment...
https://www.pyramydair.com/product/air-venturi-carbon-fiber-air-tank-fill-station-4500-psi-88-cu-in?a=4708

[PakProtector]

Go on, support dealers who misrepresent their wares...it hurts all of us.
cheers,
Douglas

Hurt 

included on edit:
What this boils down too is Public Internet assassination of another persons view point and convictions of standing there ground who differ from others.

Yes, hurt...how much trouble are you going to have to put forth to make sure you are getting what you think you're getting? Are you capable of making the effort? This is one more brick in the wall that keeps me from knowing what I am buying...support the vendors that are doing it and it gets worse.

Fortunately, in this particular case I have an adequate education in physical law that allows me to spot this particular mistake relatively easily. For telling y'all about I get labeled a 'hater', and 'public internet assassin'.

You can differ all you want, in this particular case, it is not about 'differ-ing', air is *NOT* an ideal gas, and treating it as such is entirely wrong. With extreme sarcasm, I say, 'I wait for somebody to differ with me on saying the sun does not shine during the day'. Behaviour of compressed gases is not a newly emerging science, try looking up 'non-Ideal behavior of compressed air' and see what you find.

It is not 'public internet assassination' either. Anybody who has made such claims is wrong, and in at least one of the cases, adequate evidence of their mistake has been provided...and the justification given was, 'somebody else does it'.
cheers,
Douglas

[rsterne]

Hopefully I can clear up this mess about 88 CF tanks being called 97 CF.... Until very recently, I too was miscalculating the volume of air in 4500 psi tanks by using Boyle's Law.... Using that, you do indeed get 97 CF for the volume of air inside a 550 CI tank at 4500 psi.... However, Boyle's Law, while almost 100% correct at 3000 psi, doesn't give the correct answer at 4500 psi, because air doesn't perform as an "ideal gas" as Boyle's Law would predict.... This increases the pressure more quickly than it should according to Boyle when the tank is filled beyond 3000 psi.... Here is a diagram which should help you to understand.... Check out the line for Nitrogen (N2), which is 80% of air.... This diagram is based on the Van Der Waal's equations, which correct for this factor....

[img width= height=]http://www.chem.ufl.edu/~itl/2045/matter/FG10_020.GIF[/img]

Note the value of the mulitplier on the left axis, which is 1.0 at 204 atm. (3000 psi), but is about 1.13 at 310 bar (4500 psi).... What that means is that the pressure at 306 atm. is about 13% higher than if Nitrogen behaved as an "ideal gas", which is what Boyle's Law assumes.... So, for our example, while at 3000 psi, that 550 CI tank would contain 550 x 204 / 1728 = 65 CF, and at 4500 psi (by Boyle's Law) it should contain 550 x 306 / 1728 = 97 CF.... you actually have to divide that 97 CF by 1.13 to get 86 CF.... The difference between that 86 CF for Nitrogen and the 88 CF for air is because of the Oxgen content, which follows a similar, but slightly different curve to the Nitrogen....

So, if you use Boyle's Law (which is inaccurate at 4500 psi) you get 97 CF.... If you correct it to allow for the non-ideal behaviour of air at 4500 psi (which is the correct calculation), then you get 88 CF.... I didn't understand this until very recently, and I thank Pak Protector, and Steve in NC, for clarifying it for me.... The bottom line is, that at 4500 psi, the 550 CI tanks contain 88 CF of air, not 97 CF....

Bob

[darrenf]

For telling y'all about I get labeled a 'hater'.
cheers,
Douglas

People have a hard time accepting that they might have been fooled, and find it easier to attack the messenger than to accept the possibility they were.

[jonnnyboy]

Gentlemen, this thread has gone far enough off the original track.  Hurt feelings and angry responses have no place on the GTA. It's time to step away from the calculators and get back to shooting air guns. Carry on, gentlemen!

Joe