Tank vs direct fill confusion

[javpcp]

Bare with me, I’m a newbie to the self filling of air technique:

So I’m trying to understand the use of 75 cu.ft. tanks. If I fill the 75 cu.ft. tank to 4500psi andI have a 580cc carbon fiber tank, at 3000psi and want to fill to 4350psi,the AOA calculator says I’d only get 1.3 fills. Not sure if I’m doing the calculation correctly.

1.) So for this situation, it seems as though having a 75 cu ft. tank provides the benefit is having 1 full fill readily available. Am I missing something?

2.). Seems like from an economy standpoint an compactness , having a second 580cc bottle may be a better idea. Again am I missing something with this rationale?

BTW. The pcp I’m basing this discussion on is a 25 RTI Prophet.

 

[cmatera]

Your numbers look correct to me. Couple questions: Do you have more than one 75 cu/ft tank, and how do you fill it (them)? ie do you have a compressor or do you go to a dive shop?

 

[dc8cappie]

You had a slight miscalculation. How about 11 times filling from 1450 psi to 3000 psi in a 580cc tank from a 75 cu. ft. Tank filled to 4500 psi.or 310 bar.

 

[javpcp]

Cmatera:I will be filling my own bottles, I bought a tuxing double cylinder. just trying to decide if a large air tank make sense for me. Do no own one yet.

Dc8crappie: so I was wanting to fill the 580cc from 3000 to 4350 psi.

 

[2fast2furious]

You are confusing us. Cause one minute you said you want to fill to 3000 psi. Then next minute you want to fill to 4350 psi. So which is it? If you going to fill to 4350 psi, then yes you will get 1 to 2 full fill from a 75cf tank. Cause each time you fill, the tank will drop in pressure. Meaning you will get less and less psi each fill, so you won't get that full 4350 psi fill. If you only want to fill your gun tank to 3000 psi, then a 75 cf 4500 psi tank will get about 10 or so full fill. Usually those 480cc and 580cc bottle are rated for 3600 psi. On my impact, it use a 480cc bottle and I get about 8 to 10 full fill from a 75cf tank. 

 

[javpcp]

Actually no I never said I wanted to fill to 3000psi, read my initial post what I said was: “ I have a 580cc carbon fiber tank, at 3000psi and want to fill to 4350psi” meaning I want to fill from 3000psi to the service rating printed on the bottle 300bar/4350psi, of the carbon tank. The one mistake I made was I may have mis-quoted the tank volume, I’ve seen it quoted as a 580cc tank but the bottle say 0.5L/500cc.

 

[Roachcreek]

Remember, although your filling tank pressure may drop below your targeted fill of 4350, you will have many more fills at a lesser psi, ie 4250, 4200, 4150 etc,you just get fewer shots. Having a compressor you can top it off at anytime.

Since you are filling your own bottles, you might also consider, as so many of us have, used fireman bottles on ebay, I bought a 30 minute bottle for $34.95 yesterday.

Regards, ,

Roachcreek

 

[JohnnyPDX]

wtf

 

[B]

Why you filling your bottle up to 4350 psi , Is prophet rated that high? Most of the guns are rated at 3600 psi. 
also why you start refilling at 3000 psi ,this is like 210 BAR , is your regulator set that high?

B

 

[javpcp]

Factory Bottle says is rated to 300bar/4350psi. Factory regulator is set at 150 Bar/2175 psi. The fill from 3000 psi was just a starting point for discussion. Is it a better idea not to fill to full service capacity from a safety standpoint?

 

[RWC123]

javpcp, I have an RTI Priest 2. As others have stated, you are only going to get 1-2 full fills from a 75 CF bottle. However you are not going to need to fill your gun until it gets down to 2175psi or so (less if you lower the reg pressure and have the gun set up for efficiency/shot count). When filling from a bottle the majority of your fills are going to be partial fills. You will find that if you choose a lower "fill to" number such as 230-250 bar to enter into the air consumption calculator, you will get much higher number of partial fills. Keep in mind if you are just shooting from a bench you can tether your gun to the tank. The reality is only some guns are 300bar guns (most are 230-250 max fill) so you only see the benefit of the extra 50-70 bar max fill capacity on the RTI when you are filling the gun directly from the compressor or the first fill from an external bottle. Hope this helps. 

 

[B]

Ok so looks like prophet is rated up to 300 BAR (someone please confirm) I was thinking that you over filling your gun, always fill to manufacture recommended pressure

You "should" refill your gun somewhere around regulator set point so around 150 BAR ,and yes you will only have one full fill from 75cu/ft tank and probably two more usable fills. 

B

 

[javpcp]

Thank you RWC123! I appreciate you taking time to explain this to me. makes sense for me to follow this rationale.

 

[javpcp]

I can confirm that it is a 300 BAR service rated PCP.

 

[2fast2furious]

You want to top off/fill your tank on your gun when it reaches same pressure or lower as your reg is set to. You can fill it back when its at 3000 or at any pressure. Doesnt really matter. But to get the most shots per fill, you want to at least bottle pressure to reach reg pressure. So if 150 bar is reg, you want to refill when bottle pressure is 150, back to 300 bar. But since the 75cf tank is only max at 300-310 bar, you will get 1 full refill back to 300 bar on your gun. Then after each refill, it will be like 280 bar, then 260 bar, then 240 bar. Thats just an estimate, exact numbers will be different. You want to top your 75 tank back to 300-310 bar when it gets to like 250 bar.

 

[javpcp]

Thanks 2fast2furious, I had gotten all hung up with filling to max pressure. After all the education from the great forum members I finally understand the big picture. Thanks you for your concise explanation and for sharing this definitely helped me!