Fill calculator

[YEMX]

I feel a bit sheepish asking this, but I have a question.  I know that when dealing with pressure vessels, volume calculation isn't really as straight forward as we'd like...  I can use a fill calculator well enough, to determine how many fills a tank will give you...  If I know what to input.  I typically use Lloyd's fill calculator:

http://www.calc.sikes.us/2/

But I'm wanting to calculate for a 68 cu in, 4500 psi paintball tank.  I converted one using a kit from the UK...  I'm not sure what values to input, and I'm having a hard time finding the threads where it was explained.  I know there's more to it than simply doing a conversion from cubic inches to cubic feet...  I remember having issues when trying to do just that calculation- there's more to the conversion than that...  TIA for any help!

[AlanMcD]

I calculated your tanks capacity at just over 12 cubic feet of air at 4500 psi, and then I went to Lloyd's calculator to play around with it, and I saw he has a table at the bottom that lists common tank capacities - and yours is there.  He lists a 68 cubic inch tank at 12.2 cubic feet.  I think it is a bit less, as air is not an ideal gas at 4500 psi, but it should be good enough for general purposes.

One thing that these calculators typically miss is the lost air in the fill hose, which as they say "ain't nothing" - especially when you consider that you are filling it from zero up to your fill pressure and then venting all of it away every time . . . . so even only 5 ccs will act more like 15 to 20 ccs of added reservoir space for the fill calculations, depending on pressures, and I bet most are more like 10-15 ccs when you consider the space around the SCBA valve (although some dedicated valves probably do better).

[YEMX]

Well now I feel really stupid!    I never noticed that common size conversion table at the bottom!!!  Dang it!  Many thanks!

[YEMX]

Well, if I fill the tank up to 2800 psi, from 1500 I can fill the TalonP tank 7 times using the 68 cu in tank from full.  Of course, this is just a rough idea, I won't know the real numbers until I shoot some pellets through a chrony and see what's what.

[Chickenthief]

This will do everything you want:

https://sye.dk/airgun/index.php

Use @ 0.005liters~5cc~.305cui for fill kit volume, unless you have a looooong fill whip.

As most all calculators it lacks the ability to calculate partial fills.