Question on compressed Air

Keith S said:
The psi has nothing to do with bottom time.
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As Don said, yes it does. More pressure in the same area equals more volume.

Cubic feet (or inches) are measured at 1 atm. An 80in^3 tank olds 80in^3 of air at 1 atm. If you have 200atm (bar) in a 80in^3 tank there will be twice the volume as 100bar in a 80in^3 tank.

As far as rifles go, the Theoben E-type are exceptional rifles for the price. I've shot several with a dealer friend of mine and they are freekishly accurate out to 60 yards (longest shooting of the day). If I wasn't tickled to death with my EV2 I'd get one for sure.


Regards,
MM
 
How many cubic feet of air does one of the 4500psi tanks hold?
 
Sorry, meant ft^3.

Tanks come in all sizes. Check http://airhog.com/cf_tanks.htm.

An 80ft^3 tank rated at 4500psi will hold 80ft^3 of air at 4500 psi.

An 80ft^3 tank rated at 3000 psi will hold 80ft^3 of air at 3000psi

BUT, the 4500psi tank is smaller, OR, if you prefer,comparing equal size tanks, tanks that are of the size that hold 80ft^3 at 3000 psi will hold 120ft^3 if rated for 4500psi.


Regards,
MM
 
How many refills???

How many refills will a tank of this size and pressure supply? Seem like pressures that high could be dangerous when rolling around in the back of your pick up or trunk. Maybe I'm just used to CO2 and just filling at home from my supply tank I keep there.
 
I had a neck O ring (between bottle and valve) blow on a fresh 4500lb tank in the floorboard of my pickup once..while driving down a freeway with heavy traffic...it was exciting for a while. I got the window open and it took about 10 minutes after I got to the shoulder for the thing to bleed down all the way.
 
Quite a while...you don't move too fast walking stifflegged. The thing I learned from this was that the cheap way is not always the best way. I had cut a deal with the local fire department to fill the tank. This was before I had bought my compressor. The first fill I was present for and I showed them how to hook it up and fill it. The second fill, I was told they were busy and to leave the tank and they would get it later. When I returned, it was full and I thought all was well. After the blowout, I did some questioning, and the fireman said that he could not understand it, he had removed the valve and "inspected" the tank himself. He had, I'm sure, pinched the O ring when he reinstalled it.
 
Dive Shop Is sue

My local dive shop will not fill a tank unless you provide proof of Diver Certivication. I explained it was for air rifle and they could not care less.
Fortunately I went home and got my card from 1970 proving certification and they had never seen one so old (the card that is).
 
fire house

I didn't see anyone mention your local firestation or firehouse supplier. I have a firehouse supplier in my area and he fills my 4500psi carbon fiber tank for as little as $5.00. Check um out. Nitrogen can be used but i don't think the pressure is great enough. The 4500 tank is great.
 
I shot air in the old BR50 days. If I remember right we would fill the rifle to 2400 psi, that is were the best accuracy was. I have a 100 cu ft tank and I shot the nationals at St Louis the last year BR was there, it lasted both days. Tank pressure is around 3200 psi. You can get around 25 good shots per fill and it will take a few sighters to settle down after a fill. Used 10 grain round nose pellets and sprayed them down with Slick 1 Lube.
 
question

I am coaching air rifle in our local 4H chapter and I recently bought some new CO2 rifles for our kids to use. I had been planning on just having the local welding supply house to refill them for me but lately decided on buying an Avanti adapter to hook up to my CO2 tank for my MIG welder.

Is there anything that anyone can tell me other about other than having to turn the tank upside down to fill the tanks? Do they need to be weighed or can I just use my gauge to fill them to the required psi?

Also, now that I found this particular post, since I am a retired fireman, I have access to the compressors for filling the SCBA's. What would be required to change the Avanti rifles over to run on compressed air?

Thanks for any help with this issue.

Jeff
 
cntryboy1289 said:
Also, now that I found this particular post, since I am a retired fireman, I have access to the compressors for filling the SCBA's. What would be required to change the Avanti rifles over to run on compressed air?

Thanks for any help with this issue.

Jeff
Click to expand...

Jeff,

I also have a few of the Avanti rifles from a junior program I used to run, and I don't think they can be converted. The head pressure of liquid Co2 is aound 700-900 PSI (if I remember correctly, depending on temp of container and contents) and filling a Avanti tank with 750-900 PSI air would yield very few consistent shots.

The Avanti does not use a "regulator" but relies on Co2 "head" pressure for somewhat consistent pressure. As the head pressure drops, the liquid Co2 gassifies and returns the pressure to near former level. BUT as the Co2 boils off, it also reduces the temperature of its container (that's how your airconditioner works), thereby further lowering the head pressure. Kinda of the chicken/egg syndome.

But with air at the same pressure, you are not replacing the lost pressure through gasification, therefore each shot would be a lower velocity.

High end PCP rifles use regulators set around 1000 -1200 psi. So, until the tank pressue falls below that, you have a consistent velocity.
 
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Thank you very much for the information. I had been very curious about it before I found the post and didn't have anyone locally to ask. If you or anyone else could help me with the proper procedure for filling the CO2 tanks, that will be greatly appreciated as well. I will be using my CO2 tank from my MIG welder to refill the tanks using the Avanti refill kit.

I think if I remember correctly that the guy that fills my son's paintball gun tank has to weigh it on scales. Is that correct by chance?
 
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cntryboy1289 said:
I think if I remember correctly that the guy that fills my son's paintball gun tank has to weigh it on scales. Is that correct by chance?
Click to expand...

Well...sort of.

2 things to keep in mind:

#1 He probably sells CO2 filling by weight, therefore he weights them for pricing

and

#2 If you were to be able to get the cylinder completely full, and if the cylinder temperature were increased, the blow-off seal would probably pop.

Therefore, it's best to slightly fill the cylinder, then bleed it off to cool the cylinder. Then fill it to your recommended capacity (Fl Oz of Co2). I don't remember what the tanks are rated for.

Having said that...I filled them with the cylinders at room temp, that way some of the liquid CO2 would boil off enough during filling that you couldn't get "too much" in them to pop the seal if the tank was heated (closed car, in the sun, etc.)

I have a tank with a dip tube so I didn't have to fill upside down.

Good luck.
 
thanks, sorry was gone for a few days. I talked with Daisy and they told me what you just did.

Jeff
 
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