Paintball

[pizzadude]

Hi again,

I have another one of those LP questions...

Do any of you guys know how to work out what volume of air would be required to run a marker at 60psi firing and still put out a paintball at 275-300fps.

I know that this is a loaded question, but assume that I'm running on air, have a predetermined volume of air to expel (what I'm trying to calculate) and valve is open for 'x' period of time (what I also need to calculate), I can acheive 275-300fps.

What is valve open time in relation to expelled volume, does one dictate the other?

[Al Ray]

Basicly its impossible to tell, well not really. There are just far to many variables involved and I doubt that any manufacture thats actualy invested the reasearch will give you the formula. Tom KAy however once stated that there is never more than 125psi behind the ball when fired. What youd need to kno is the volume of air at a givin pressure that it takes to fire the ball, and then design the valve to flow that amount of air. Onyl way I can think of doing it (ie designing a valve) is by trail and error. Ive got a design for a valve that Ive been tweaking (on paper) for about 4 years, and the only thing that stops me from building it is knowing that Ill probly have to bbuild several just to get it right and currently lack the time or money to do so.

[pizzadude]

Thanks for your reply Al - and you're right I do need to know the variables. I know two, just need the third (or equation to solve the third)...

I am trying to find the volume of air at 60psi to acheive 275fps (min).

Google is currently my best friend; and as soon as I have a workable equation, I'll post it here for free access. I may also be reading too deep into this?

As for the valve - I'm kinda thinking that I'll pass that headache onto one of my friends...

I just want to number crunch at this stage.

[flyweightnate]

I was told a good rule of thumb is (pressure * volume) = 100psi*in^3, so 60psi, needs 1.6 cubic inches or so. Course, there's a lot that leaves out. But I think that formula is dervied from Spoolies, where there is a constant volume available, no more no less.

[pizzadude]

Thanks Nate - I spent a whole night on the net getting loads of formulas and equations... and came up with about 24 cubic centimters (which is close to 1.6in^3) for my load volume.

Of course what I was originally asking doesn't take into account atmosheric pressure, outside temperature etc... I was just looking for a rough starting point to begin the design.

This follows on from my previous thread about having a bunker gun running off a generator - I'm thinking that something along the lines of an ICE Epic design would work very well.

Thanks to you both for your input - I'll keep posting as I develop the idea.

regards

Brendan

EDIT: forgot to say that I'd also calculated the rough barrel volume (16in, 0.689) into the design... don't know if I need to at this stage, but what the hey?