Things to ponder with how much pressure you need.

[CHK6]

In my learning I questioned what is the lowest pressure need to propell a paintball to 280 fps in 10 inches? Now granted this is the inital baby-step in coming up with a more complex answer. So imagine a system that is open at one end for the paintball to leave and a the PSI level that is constant through acceleration. I haven't figured in friction of gelatin on aluminum/steel/brass. If you happen to know the frction coefficient (u) of gelatin on one of these combinations I would appreciate it if you let me know. I just don't happen to have a block of gelatin and aluminum handy. If I did it's a simple test to gather the friction number.

Onto the fun stuff..... *Note: all numbers are in metric.

Time
t = 0.254000508001 / 85.3444 = 0.002976196 seconds for the ball to travel 10 inches and peak at 280 fps.

Acceleration
a = 85.344 / 0.002976196 = 28675.53078 m/s^2 acceleration for 10 inches

Force
F = 0.003188 * 28675.53078 = 91.41759212 newtons

Area
A = 4(PI)(r^2) / 2 = 0.000468603 m^2 ; this is area (standard .68 ball)

Pressure
P = 91.41759212 / 0.000468603 = 195085.3753 pascals

195085.3753 pascals = 28.294743 PSI

If this is correct, then this is extremely interesting. If I'm correct we can't supply a constant flow of ~28 PSI for 10 inches against an area of 0.000468603 m^2 for 0.002976196 seconds. So the next thing to figure in the PSI volume expansion ratio. That should bump this up to ~100 psi.

[AGD]

Nice job! Looks about right too! Yes somewhere around 28 psi will get the ball going in 10 inches. The problem is you waste the rest of the pressure out the end of the barrel after the ball leaves. empty barrel + 28 psi = wasted energy and low efficiency.

To get best efficiency you need to start with "x" psi and use it all in 10 inches but still get the ball to 280 fps.

For example start with 80 end up with 10 when the ball leaves gives you an average of 35 psi accelerating the ball.

Do some math, I'll monitor the post.

AGD

[Puddleglum]

Wow (you can take this post out if you feel it doesn't belong) That is really impressive. I thought algebra was tough. Keep up the good work.

[Vegeta]

Well, you cant have porting anywhere in that barrel, you know that. And it also depends on hte surface of the barrel, and like you said you couldn't find the friction coefficient. But, problem is, if hte user of this "super-low pressure gun" changes barrels, say, from a creamic to a hoed aluminum, then the pressure will have to go up/down, depending on the switch. Paint travels over certain sufaces much easier than others. But you see this on all guns, so no biggie.

Another I dea is, using an ultra-low pres. gun with a lubed barrel/ ball. I would think you could use lower pressure if hte ball or barrel was lubed to an extent. You barrel would have to be coated evenly (or turbulance could result on the ball), and be about 0.002 bigger than the ball to allow for the thickness of the bit of oil. Then you should be able to drop that psi from your already low 100 or so PSI to about 60. Im not sure how these barrels would be lubed, either by oil, which is rather primitive, or by new, ultraslick materials. Problem with oils is that it rubs off, and onto the ball, cuasing air turbulance, which cuases inaccuracy.

Ultra low psi would mean great things for paintball. more shots per tank.. less money. Of course, fill stations would raise prices most likely becuase of the loss of business due to ppl not coming in as often.

Just some thoughts...

[CHK6]

Integretion

I wouldn't say integretion is my strongest subject, but I do know how to. Integrating over time, PSI, and distance isn't a small task for me. I guess I should have paid more attention in the later parts of calculus II class.

Luckily I picked up some "light" reading. "Fluid Mechanics" by Merle Potter and John Foss. Right now I'm still on chapter 1 and I feel like the Lawn Mower Man in the amount of information each page holds. Eventually I'll hit paydirt in later chapters that talk about compressible fuilds.

Baby steps...and building blocks...no task is to difficult. Eventually, I will hopefully be able to create the building blocks of a Java API paintball simulator; where all paintball markers can be modeled and tested under virtually.

[fenris69]

lunacy

I haven't seem any specs on this yet, but the new 'Lunacy' from splatmaxx section8 is quoted at 25psi operating pressure. Seeing as the original Nova did 90psi no problem this could be interesting.

[pbjosh]

Well,

I have gone off about this topic more than once on other forums, but here it goes.

What is being looked for is not pressure/velocity but ENERGY/velocity.

A mag has about .55 ci chamber with a 400+ input pressure.

So the energy usage is about 220 in3*lbs of energy.

A shocker uses a chamber of 1.8 ci with about 180+ psi input.

So the energy usage is about 324 in3*lbs or better.

Now a tank of 68 ci in size, at 3000 psi is storing about 204,000 in3*lbs of energy. If the gun runs down to 400 psi, then the last 68ci at 400psi can't be used.

Get the picture?

Here is more. If you take the total area used by a dump chamber gun, like a 'Mag or Shocker, from the point that the ball is 10" down the barrel, and include the volume for the dump chamber and the bolt/powertube/valving arrangement, you get a total static pressure of about 40-45 psi.

A Shocker and Matrix are both very in-efficient. Both have very large volumes between the dump chamber and the bolt head. Both have huge dump chambers.

A Mag has a small dump chamber and small bolt/powertube volume.

Hence the effecientcy.

Enjoy,

Josh

[steveg]

Hey pbjosh afraid that I'm going to have to throw a monkey
wrench into your theory, the matrix is inefficient in stock
form because it wastes gas with every shot. The aarvdvark
bolt kit removes this waste and allows the matrix to use
the gas effectively. most users are experiencing about
800 shoots per 68/3000, much the same as a mag.
Oh well back to the drawing board.

[pbjosh]

[steveg]

OUCH you throw a mean gauntlet there pb
I will supply the dump chamber volume for a (my) matrix soon

as for accurate gauges try here http://www.winters.ca/pre_process.html

I bought a 0-300psi 1 1/4" gauge from one of their dealers
for C$ 11.00

[pbjosh]

oh, I already have the gauges, and they are 0-200 and industrial, for use with the 'Shiva'.

And for everybody reading this post, please attach your numbers, for tank size and pressure, plus type of gun. A chart of some such that tells the number of shots per gun and the size of the tank can be produced from that. Let me make some other posts for this so I can get a average number of shots per tank per gun, and then I can post some good numbers for the energy usage of several guns

Later,

Josh

[steveg]

Back again The volume of a matrix dump chamber is
21.5 ml (measured with graduated syringe) or 1.312 cubic in

A handy link for the conversion challenged http://www.onlineconversion.com/

[pbjosh]

VERY NICE! you figured it out with a syringe! smart.

Okay, the matrix does still dump some air, right?

and run at 140 psi?

the 140psi * 1.3ci = 182 in3*lbs which is VERY GOOD.

So, where does the rest of the air go. Some one had built a paintball gun that shot as much air out the back of the gun as shot air out the front of the gun! HAHAHAHAHAHAHA! oh boy, that seems really silly.

LOL- that still gets me.....

Josh

hehehehe

how many shots from a tank do you still get?

Humrph....hehe...giggle....

[steveg]

actually it takes about 180 psi for 280 fps I have to confirm this as It's been about a month since I've last
played so 180psi * 1.3ci = 234 in3*lbs

still not bad

further 204000 in3*lbs/234 in3*lbs =872 shots

That number is of course "ideal" so what happens in real life is different.

As for shots per tank I confess that I haven't had the bolt kit long enough to personally confirm or deny 800
shots, 68/3000 It is what people at pbnation are claiming that they are experiencing. plus I have to use a
scuba tank so I never get a real 3000psi fill.

None the less my original post was to warn you of an incorrect
assumption as to why the stock matrix got lousy
gas mileage. There are no elves involved in the arrdvark bolt
kit merely the correction of a design mistake that allowed
air to be wasted on the return stroke of the bolt
(by chance did you already know this?)

OH and how about some links to those "other" sites

[pbjosh]

As to other sites,

Actully, I have written almost the same thing to most of the other sites out there. I usually hit the Tinker's guild and the pbnation. I just put a survey up in pbnation paintball talk asking for shots per tank adn all that. chaeck it out. And on pbnation in the paintball news section is the 'Shiva' project.

The 'Shiva' is mine.

Josh