TargetTalk

I would like to calculate how much the pressure in my 200 bar 15 L scuba tank decreases every time I refill my LP10 air tank.
This will not be perfect, since I am treating air as one ideal gas, not a gas mixture.
What I need is the volume of the LP10 tank, which I can not find. I also need the pressure when the needle goes from green to yellow. Can anyone help me ?

I'll be surprised if you get a good answer to this one.

I guess it only matters if you're deeply concerned with the number of shots you'll get per fill.

I have a gauge for my tank and I refill it at around 1800 PSI; still enough to easily get me through a match.

With the gauge on your cylinder you'll easily be able to count shots (save shot targets) when you think you're getting low, and then take a reading off your main tank when you get too few shots to be satisfactory.

Thank you very much for replying.

I am doing this to play around with gas equation pv=nRT, and I don't expect it to be very useful or practical for my practise with Steyr LP10.

We start with a certain amound of gas molecules in a container at a certain temperature. Every time I hook the tanks together number of moles ? decreases, and so does the pressure. It will no be linear with number of fillings I think. So what I need is the volume of the air tank og pressure when it is yellow (when I refill).

So it is maths just for fun .

To a certain amount this will depend on whether you refill the LP10 cylinder after you have shot 120 or 160 shots and it is probable that you will refill at any point in between.
All I know is that when I have my 232bar 12litre dive tank filled up, I can refill the LP10 cylinder between 50 and 60 times and the dive cylinder will then be registering about 170 to 180 bar. This pressure would still be more than enough to fill the LP10 cylinder to be good for 100 shots.
When I get to this point, I get the dive cylinder topped up.
Never really bothered to calculate anything as that would probably be about once a year.

Try Chairgun2 - which will help by doing the maths for you.

You'll not only need the bottle size, but the deadspace volume of your filling apparatus.

sacrifice a cylinder, disassemble and remove the gauge, machine and use fittings to lead to an actual pressure gauge, fill tank with 3000 psi air, shoot 140 shots, (or however many shots you usually take before refilling) and record pressure. then disassemble and remove gauge, replace original gauge, take an accurate hypodermic syringe, fill tank with water, record amount of water inside tank.

pressure on mine when the needle is centered over green/yellow is 80bar.

I know I have forgot to fill a cylinder and shot down to 50bar without any noticeable difference.

Scott

To answer the original question directly, engraved on one of my cylinders with the rest of the mfg data: "VOLUMEN .068L"
-David

Greetings,

Long time ago, I wrote to Steyr and asked the volume of the cylinders. They replied quickly.

I use this calculator to determine tank refills...

http://www.airrifle.com/freebies/tankfills.htm

Cheers,

Dave

This is easy, weigh the tank. Weigh an empty tank, weigh a full tank, divide the delta by the pressure (in bar), now you know the weight of the air in the tank at one bar. You can figure the volume, and even use the gas law if the tank is hotter.

Steve