how much air does it take to shoot?

[BenD]

How many Cubic Inches of air at lets say 3000 psi does it take to fire a ball? could you test that some how (with great precision)??


pick whatever gun you want?

[Kweasi]

I vauguely recall some discussion on the Tinkerer's guild whereby there was some calculation to determine how much energy is required to fire a ball at a given velocity. That was then related to the ammount of energy availble per unit gas.

Unfortunately, I missed the discussion and couldn't get my own mathing to match thier results.

-Kweasi

[BenD]

the tinkerers guild?

[mike e]

the guild is another forum for airsmiths and such its run by doc nickle, anyhoo, what do you need the numbers for? if its just so you know i wont bother but if its important ill try to find them for you

[BenD]

i was just wondering... dont waste your time

[mike e]

ok ask manike he might remember, he is a real frequent poster over there sorry i couldnt be more help, and i already did check once to no avail, with no time reference to when it was posted its near impossible to find somethign

[Redkey]

The guild conversations were based on calculations and not physical testing. If you're really interested in measuring it I could give you some ideas on how it should/could be done.

[Kweasi]

Does anyone have the guild calculations? That's one discussion I wish I hadn't missed.

-Kweasi

[headcase]

pbjosh was the one who did the calculations........aren't they in the rats nest?

[Pand0ra]

It should be quite simple to do:

Measure the real volume of your tank
Measure the pressure before the shot
Shot once
Measure the pressure after the shot.

As you know the volume and the difference of pressure, you can find the volume of air used for the shot.

Of course you'll need accurate sensors with a good resolution, otherwise the measure will be incorrect.

@++

[Cristobal]

Or take lots of shots and divide your volume drop by the nubmer of shots you took. That way you minimize the relative error of the calculation even though the error in the pressure gage is fixed.

I believe pbjosh did this sort of testing on a number of different types of markers. The results are posted on here somewhere and shouldn't be too hard to find with a search.

[confedman75]

lets say it takes 1000 shots to empty a 68/3000 cant you do 68 divided by 1000 equals .068 cubic inches per shot?
68/1000=.068
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divided by

[Cristobal]

You will also have to deal with deal with the fact that not all of the pressure in your 68ci tank will be used up.

I would suggest an approach based on the engergy needed to fire a paintball. Knowing that the energy contained in the tank (or dump chamber) is its pressure times its volume, you can work out the energy you start off with in your tank. When you fire, the pressure in the tank will drop but the volume will stay constant. You can find the change in energy in the tank and divide by the number of shots. I would also suggest not shooting until you run out of air. If you do this you're last few shots may not be full-powered.

You could also calculate the energy needed to fire a paintball by knowing the volume of the automag valve, your operating pressure, and the residual chamber pressure. This result could then be compared to the results from the tank method. This method, of course, would require a measurements not which would not be easy to make. You'd need either precise dimensions or some other test (maybe a fluid fill) to find the volume, and then a pressure gage attatched to the dump chamber.

The most interesting thing about comparing energies is that you will find it varries from paintball gun to painball gun. That's where pbjosh did a lot of investigation in order to come up with a very efficient design (which I wish he would post more info about!) If I recall the mag does pretty well for energy efficiency but his "shiva" marker was able to do even better.

[pbjosh]

This got lost a bit- but I wanted to put something back in here,

Energy values I used were in*lbs.

A tanks volume(in) times the pressure it holds(lbs) give you total energy you can use. Mind you this is from tank that has had a chance to cool down. A rapidly filled tank is too warm, and won't give a correct reading untill it has cooled down.

A 68/3000 tank has about 204,000 in*lbs of energy in it.

Divide that by total # of shots fired- you get a good area for amount of energy used per shot.

Josh

[SlartyBartFast]

Originally posted by pbjosh
A 68/3000 tank has about 204,000 in*lbs of energy in it.

Divide that by total # of shots fired- you get a good area for amount of energy used per shot.

Josh

But are you considering the left over energy in the tank? Can't use the last 400 odd psi.