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All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: drewciferpike on March 18, 2016, 12:24:44 AM

Title: Shot calculator/equation?
Post by: drewciferpike on March 18, 2016, 12:24:44 AM
Given a 13ci 3k psi tank with a reg (300 psi), where can I find a calculator/equation to determine how many times I'll be able to fill a given volume, up to 300 psi? Google isn't helping me, as all I'm finding is "Oh, I get this many shots with x rifle" info.
Title: Re: Shot calculator/equation?
Post by: LDP on March 18, 2016, 01:16:52 AM
Here you go.
http://www.calc.sikes.us/2/ (http://www.calc.sikes.us/2/)
Title: Re: Shot calculator/equation?
Post by: drewciferpike on March 18, 2016, 02:15:52 AM
Didn't see a raw formula, and I need to figure out a fill  to 300 psi, refilling  from 0. That Calc requires 500 psi, minimum, at either end,


Thanks for quick response
Title: Re: Shot calculator/equation?
Post by: rsterne on March 18, 2016, 02:34:16 AM
300 psi / 14.5 = 20.7 bar.... times the volume you are filling is the volume required for each fill.... eg. 100 cc you will need 20.7 x 100 = 2070 cc / 16.4 = 126 CI of air at 1 bar....

A 13 CI tank at 3000 psi contains 13 x 3000 / 14.5 = 2690 CI.... When it is down to 300 psi, it would still have 13 x 300 / 14.5 = 269 CI left in it.... so the air available is 2690 - 269 = 2421 CI....

Divide that by the air per fill to get the number of fills.... 2421 / 126 = 19 fills....

HTHs....

Bob
Title: Re: Shot calculator/equation?
Post by: drewciferpike on March 18, 2016, 10:16:05 AM
That helps a lot.

So I understand everything, though (I don't like to plug in unless I know why):

Why the conversion to bar, initially? Is there a relationship between units that I'm missing?
Title: Re: Shot calculator/equation?
Post by: LDP on March 18, 2016, 11:19:46 AM
Quote from: drewciferpike on March 18, 2016, 02:15:52 AM
Didn't see a raw formula, and I need to figure out a fill  to 300 psi, refilling  from 0. That Calc requires 500 psi, minimum, at either end,


Thanks for quick response
Sry Drew I didnt realize it only went down to 500 psi. I always fill before that so never even looked ;D
Title: Re: Shot calculator/equation?
Post by: rsterne on March 18, 2016, 12:51:35 PM
You need a number to multiply/divide the reservoir and tank pressures by to convert psi to bar so that you can compare volumes at different pressures....

1000 cc at 1 bar is the same amount of air as 10 cc at 100 bar (1450 psi), right?.... When you are dealing with two different volumes (tank and gun), you can't just use the pressure, you need to know the amount of air they contain (number of molecules), and the easiest way is to use bar.cc or CI at one bar....

Bob
Title: Re: Shot calculator/equation?
Post by: drewciferpike on March 18, 2016, 12:55:22 PM
Noooooow that makes sense. Thanks for explaining!