Tank Size/Weight

[caleqs]

Hi. I just picked up a 68/3000 flatline for myself. I want to get my son an air tank as well so that I can fill his bottle from my scuba tank. But I'm not sure what to get him. I want something light and not too bulky. Should I go for a 68 fibre or a 47 alum? How does the weight of a small alum tank compare to the larger wrapped tank? I'm guessing full they might be about the same weight, so it would come down to which is less bulky, which means the 47.

Thoughts?

[caleqs]

Oh, btw, I plan on getting him a PMI Eforce, if that makes any difference to the discussion.

[mykroft]

why not a 45 fibre? Lightest option out there

[FalconGuy016]

47/3000 dont last very long for shots, a 45/4500 fiber however will get you around 800 I think (?)

Even if you cant fill to 4500, just having the capability might be a good idea if you ever need to fill at a field or something. It is also much lighter. And mabye sometime in the future you can get a booster or compressor :) (if you are rolling in cash)

[PsychoBaller]

Lol......

Buy my Geddon that is for sale.... its 68/4500 and its almost 5lbs filled, hehhehe...... jk... it's one of the heaviest tanks on the market for a 68.

~da baller

[xen_100]

why do people keep making the distinction of what thier tank wieghs "filled" vs empty? we are talking about air here not co2..........68 cubic inches of compressed air couldn't be weighed by the best of scientific scales.

[caleqs]

Hmm, seems I recall my scuba tanks being heavier when they're filled v. not filled.

I don't believe they make a 45 fiber.

So the question is still unanswered, which is heavier, a 45 alum or 68 wrapped?

[CobraC]

http://www.actionvillage.com/031-3006.html - 45/45 fiber wrapped. Nice tank, a friend at the field has one. Very compact and light. The only thing with it is that I don't know if it will work with the stock asa adapter on an eforce, My nitroduck wont work on my friends and we've never tried to use another hpa tank. I say go 45/45, small and light.

[caleqs]

Yowza! Cool tank, but I'm not going to pay $200 for a tank for my son to plink around the backyard with. Guess I should have said that my son's only 8 and we'll just be goofing around in the back yard. So I'm not looking for anything expensive or feature-rich. Just a tank he can manage and I can fill from scuba. Worst case I'll just stick with CO2 for price.

Thanks for the heads-up on the Eforce. I'll check compatability.

[halB]

well as a product of dade county schools i can tell you this, a 68/3k tank, when filled, will weigh 204000 pounds more. since it has 68 cu inches and its 3000 pounds per square inch. but wait, thats squares, not cubes! o well

its heavier but the difference is negligible. dont buy crossfire, theyre very heavy

[xen_100]

put them on a scale next time......

I would be interested to know.

your average 80 cubic foot scuba tank will hold 2265 liters of air.

1 mole of air takes up about 22.4 liters.
1 mole of air weighs about 26 grams.
your 80 CF tank will hold 101 moles of air.

that will make your 80CF tank (wieghing about 50 pounds emtpy) about 5 lbs heavier. (theoretically.) that is using the ideal gas law.

[joeyjoe367]

That's all at STP (Standard temperature and pressure) which is 0* celcius, etc...

I think a 47/3000 will be fine for your son to plink around with. I don't think you want a 4500 psi tank, seeing that you're going to be fillling off of a scuba, which are generally 3000 psi, unless you're shellin' out the big bucks.

[xen_100]

that is true......there are alot of other variable that will effect it. but that will give a close approximation.(the ideal gas law is not perfect either. but it is a nice start.)

[NiteWolf1138]

Originally posted by caleqs
Hmm, seems I recall my scuba tanks being heavier when they're filled v. not filled.

Considering the scuba is measured in cubic feet and the PB tanks are measured in cubic inches, you'll notice a difference in filled vs empty for scuba a lot easier than PB-HPA.

Air has weight, for a fixed volume of a particular gas a higher pressure weighs more, but its not as easy to measure since gas is WAY lighter than say... steel.

NiteWolf1138

[FalconGuy016]

47/3000 sounds fine then for just backyard play I suppose, and you can fill it many times :) and they are $70-80 new

edit: actually those $70-80 are steel, ive never heard of alluminum air tanks. Steel is HEAVY