What is the VOLUME of air required to go 300 FPS?

[the electrician]

I'm in KC on the kansas side. shawnee, kansas.
nice town. KC has quite a bit of industrial business, so there's alot of stuff available in the way of equipment and tools.

I've thought abput coming up with a gun design that would take throw together a valve actuation and breech design I have but the real world (pregnant wife and such) takes up most of time. but that's the way it goes.

paintball is not just throwing paint to me. it's tinkering that is the most fun. shooting your own invention means more to me than any of it.

[QUINCYMASSGUY]

volume/pressure

OK guys, got the stumper of the day....

What size chamber/psi combo would fire a paintball at 280 or 300 feet per second?

For example, if I had a:

10cc chamber I would need 200psi
12cc chamber I would need 180psi
14cc chamber I would need 160psi

I am talking a chamber setup similar to a mag so not too far for the air to travel and a decent paint-to-barrel match.

And also, what width of a flow chamber would be needed to facilitate it?

[KRAKMT]

QUINCYMASSGUY I think there was a link on warpig regarding the algorithm of the mag which listed something like .54 ci at 450 psi. It has been a couple o years since I read that but it was a figure I have started some of my tinkering with.

[QUINCYMASSGUY]

KRAKMT

KRAKMT, thank you and a belated welcome to AO. I will browse for that thread, it would be interesting to see it and what factors could affect it, hopefully for the positive. Some are:

-More open channel bolt/Venturi-restricted bolt. I think it's proven Venturi is bogus

-Longer channel for air to travel to shoot/shorter channel. My assumption would be if the passage from the air supply to the barrel was more, the gas gets to expand more and would require more to fire and also vent, reducing efficiency. True?

-Heavier bolt like AGD's/Lighter bolt like delrin. Would using a lighter bolt boost efficiency or does it not have a significant enough effect to be worth the hassle?

-What the optimal ratios are: meaning if a mag uses .54 X 450 then it has a total of 243, so does .75 X ? =243 (with ? ending up being 324psi) result in the ball shooting faster or slower? If it goes faster, then the psi can be dropped and more efficiency is achieved. If it shoots lower, less efficiency. This is a tough one to test.


Just some thoughts for the talk....

[KRAKMT]

QUINCYMASSGUY thanks for the welcome- I tried to remain a voyeur but was forced to registered when the site got attacked. But I still try to limit myself on the posting.
I have been curious as to the whole marker efficiency debate. As to the mag the level x and the bolt spring all take energy/psi to operate that robs efficiency. Also I believe people confuse efficiency with depth of usable air but that is for another discussion. A cocker looses some efficiency via the 4way and additional through the force needed to move the bolt. I began to wonder when I read a viking thread where they were able to get up to 2000 shots with bolt mods vs a count of 1000 on a stock viking. Thus sum efficiency is lost to friction and some to valve dwell.
I will be curious to hear more from the electrician. It appears he is working on the valve dwell where as I have a prototype for a frictionless bolt.

[QUINCYMASSGUY]

KRAKMT

KRAKMT, I stay out of alot of the really dumb threads, but stuff like this really interests me (and I'm very happy to give my two cents in other threads when I feel it's needed). I wish I had more technical expertise and resources for fabrication but I have a basic knowledge of the kinetic and pneumatic principles involved in ideas such as this and love brainstorming. I think you and the electrician are the same but with more knowledge.

See, one thing you have to keep in mind with the mag is that although more air and pressure is being used to move the bolt forward and fire than, lets say, a Viking, but that the Mag doesn't use any air to reset the bolt while a Viking, Cocker, etc, does. However, due to the Mag having to operate at 400psi or so to do it, you start running into issues when the tank starts getting near 400psi because the reg starts starving. This is partly why mag efficiency is weak, you can't utilize most of the tank. Also though, I think you can't balance out the air to use just enough to fire the ball and reset in time for the next shot, I think more is used to just be safe. Hence, lower efficiency.

I guess we all have our ideas a-brewing, mine is a combination of things but not what either of you guys are working on. But related. One idea The Electrician and I were punting around a while back was to set a valve with noids on both sides to push it open. Each would only have to go half the distance to open the same as a normal noid/valve like the one he is working on. This open up opportunity for Lower operating pressure or higher cycle rates.

I guess my next question for the masses is.... how efficient is AGD's pre-measured chamber idea? What I mean is, the mag stores a set amount of air in the chamber which is that quickly released when the sear lets go of the bolt and lets it get around the bolt and out the front, while using the on/off to seal the back to prevent leaking or runaway. Is this efficient or is premeasuring in this fashion or is this actually partly why the mag isn't too hot on efficiency? How effective would this design be with a larger chamber and lower pressure? And no, I do not mean with the spring method of bolt return, just in firing in general. Would it work with perhaps a larger diameter in the power tube? I do see benefits of the mag being redesigned for 300psi operation however the key fact of the spring return method making 400psi optimal is understandable (300psi may require too light of a spring and affect firing) and I am sure Tom did his homework to make that decision. The guy knows his stuff, probably more than most of the manufacturers out there.

And I guess a bonus question would be, what type of diameter air passage is needed for recharge in guns with these types of dump chambers? With the on/off pin being so small in the ULT's, does this constrict airflow? What would be the smallest it could be (reducing trigger weight that is) without doing this? Major idea a-brewing on this one and if I get the info I need to be sure on it (a little more than this question, but not by much) I would be happy to elaborate on it and publicize it.

[hitech]

Re: KRAKMT

Originally posted by QUINCYMASSGUY
I think you can't balance out the air to use just enough to fire the ball and reset in time for the next shot, I think more is used to just be safe. Hence, lower efficiency.

THAT is the main reason for the 'mags "inefficiency" (level 10). It keep dumping air from the air chamber after the paintball is gone. I recently confirmed this with Tom.

Originally posted by QUINCYMASSGUY
... how efficient is AGD's pre-measured chamber idea?

The chamber is too big. However, if you decrease the chamber size then you start needing to increase the chamber pressure. That doesn't market well. (Again, confirmed by Tom).

The most efficient way to fire a paintball is with "high" pressure (including the pressure behind the paintball) and as fast as possible. Accelerate the paintball in just a few inches (say three). Tom's research when developing level 10 caused him to believe that the paintball can stand the higher pressure necessary to accelerate the paintball to 300fps in a few inches. Current markers are all in a range of about 40 to 110 psi behind the paintball. Build a marker that can deliver more like 300 psi behind the paintball and you would be amazed at the efficiency. But could you sell that?

I have to credit Tom for some of this. I did come to some of the conclusions on my own, but not all of them.

[QUINCYMASSGUY]

chamber

Hitech, always a pleasure to have you contribute, you know your stuff. And having Tom Kaye in the proverbial shadows is a blessing, I know he is a genius for the work he did in the old days and frankly the reason companies like smartparts ever existed. His technology started it all basically.

So the problem is you have the spring and have to use extra air just to push the spring forward enough and go over just to make sure....hmmmm.... is that what you meant by the chamber being too big? I guess my question is, could that chamber be decreased to prevent the excess and use springs as the variable to find optimal efficiency while still cycling properly? If it's too big already, couldn't a little be cut out and not need the increase in pressure? I'm sure it's something to do with pressure balancing out or something (spring and air pressure that is) but I'd love to hear the logic. Tom's right, higher pressure wouldn't market well.

The mag holds 400psi or so in the back chamber, but how much does that end up being while pushing the paintball? Is that the 110psi?

I think low pressure (not lowest of the low, but like AKA low) holds promise because you have barrels that are 12-14 inches which gives you more distance to accelerate. I know it can't use too much of that or else it would result in shot delay but getting a gun to run shot-to-shot as efficiently as a mag but be able to get down to 150-200psi input would be a huge jump in efficiency for the tank. I hate to say it, but low pressure firing seems to also help reduce kick. I understand it's still firing at 300fps high or low pressure, but distributing the acceleration a little more helps players keep control of the marker.

Just my thoughts, and hitech I'd definitely love to hear your thoughts on the on/off pin question I had and also, if it would starve it, if a smaller chamber/higher pressure would maybe counter the starvation.

[hitech]

Okay, let me first say that I do NOT have special access to Tom. I was at AO Day SE II in Clemson. I had a few question on efficiency and Tom was happy to answer them (as always). He did complement me on my knowledge, which is always nice.

Also, I am not an engineer (software engineer doesn't count). I took one year of physics in college for fun (yes, I'm strange ).

Originally posted by QUINCYMASSGUY
So the problem is you have the spring and have to use extra air just to push the spring forward enough and go over just to make sure....hmmmm.... is that what you meant by the chamber being too big?

The air pressure needing to overcome the spring pressure has nothing to directly do with the efficiency. The biggest problem with the 'mags efficiency is that the paintball is gone and the dump chamber is still releasing air. The bigger the air chamber the more air there is to escape. Making the air chamber smaller would cause the pressure to drop faster and there would be less air to escape after the paintball is gone.

Originally posted by QUINCYMASSGUY
The 'mag holds 400psi or so in the back chamber, but how much does that end up being while pushing the paintball? Is that the 110psi?

Yes, except that the 'mag doesn't build 110psi behind the paintball. Level 7 built about 60psi behind the ball, and level 10 is a little higher (but under 100psi, I think).

Originally posted by QUINCYMASSGUY
I think low pressure (not lowest of the low, but like AKA low) holds promise because you have barrels that are 12-14 inches which gives you more distance to accelerate.

Actually, THAT causes a maker to be inefficient. If it takes 12 inches to accelerate the paintball then you have to fill up that entire volume with air. And the air pressure behind the paintball has to be at a higher pressure than the ambient pressure. The bigger area you have to pressurize the more air it's going to take. If you could accelerate the paintball in just a few inches and cut off the air source then you would be more efficient. Less volume to fill. The problem is that accelerating in a shorter distance requires a higher pressure behind the paintball. And you have to deliver the air very fast. The faster the better. The ability to instantaneously deliver the chamber pressure behind the paintball would be the most efficient.

Originally posted by QUINCYMASSGUY
I hate to say it, but low pressure firing seems to also help reduce kick.

The slower you accelerate the paintball the less "kick" you will get.

Originally posted by QUINCYMASSGUY
I'd definitely love to hear your thoughts on the on/off pin question I had...

I'm not sure what the question was. The UTL on/off pin has the SAME size head as the other on/off pins. That is the size of the opening the air sees when refilling the dump chamber.

[QUINCYMASSGUY]

hmmmm

Hmmm, ok then I goofed it. I guess it is smaller pin then that I was thinking, whatever would make the pull even lighter but perhaps so light it would be impossible not to chuff. Oh well.

Anyways, I'll think a little more on the LP stuff, I guess I'm punting around an idea or two but alot of it I'm still trial-and-error processing. It's tough coming up with something original that makes any major paintball gun better.

[Koosh]

So decreasing the dump chamber size and increasing pressure would increase effeciency?

Need to get someone with an old Screw-in powertube (like mine ) to maybe fill in the dump chamber a little bit (with what, I don't know... Concrete? ) to see if that will work.

Of course, AGD probably already tried this, and I'd be messing up my mag for no reason.

And increasing the pressure (adjusting the velocity) would only go so far before the blow-off valve came into effect.

[hitech]

Putting something in the dump chamber is a fine way to decrease the size. Just make sure you don't block any holes. At some point the over pressure valve would vent, but hopefully with the level 10 pistons it will be high enough. Give it a try and let us know the results.

[QUINCYMASSGUY]

possible

If it works, hey, can't a new spring be used in the release valve? I was designed solely to vent at pressures that would result in speeds greatly exceeding 300fps so if a smaller/higher pressure chamber was being used you could use a heavier spring to allow it to go higher and still maintain the intended functionality.

And a rubber, delrin, or even steel hollow tube could be insterted if the front could be totally unscrewed. thicker the sides then the smaller the volume (customizable?), if it fits snugly to the sides of the cylinder then it would withstand the pressure, and best of all it could be removed and even switched up with cylinders of different thickness, allowing true customization of chamber volume. The whole front of the dump chamber would need to be removable to fit it but it could be something for future XValves.

I'd love to see a dynamics chart on this one.... pressure vs. volume vs. efficiency

[athomas]

Higher pressure in the chamber equals chopping problem on a mag unless you increase the tension of the bolt spring. We have done this on the level 10 and found it to decrease the efficiency, not increase it. The reason is that there needs to be a differential pressure between the chamber and the bolt spring that allows the bolt to go forward at a certain force that is unable to break a ball. The differential is a smaller percentage of the total chamber pressure when the psi is high than when it is lower.

eg; Say the chamber pressure is 400 psi and the bolt spring exerts the equivalent of 350psi. The differential would be 50psi or 12.5% of the chamber pressure. If the chamber pressure is 600psi and the spring exerts 550psi for the same differential of 50psi, then the percentage is only 8.33%.

The differential of only 8.33% results in the air flow being more restricted. The initial blast of air is sufficient to propel the ball, but the added restriction means the chamber bleed down will last longer. Any additional air flow after the ball is away from the barrel or that cant't catch up to the ball is wasted.

Now, all that being said, the results are based on the existing dumb chamber size. If the chamber size were decreased as mentioned, then increasing the pressure would not decrease the efficiency. The pressure would bleed down quicker after a shot resulting in less wasted air.

[QUINCYMASSGUY]

bingo

Bingo, so unless I totally misinterpreted that, by going with a smaller chamber and higher pressure (less restriction by the reg basically) efficiency can be improved, and by offering a screw-on front to the dump chamber for the purpose of being able to insert "de-spacers" for varying volumes, users can customize their operating pressure with a positive effect to efficiency. Maybe a little more kick, but well worth it. AGD has never been about the low pressure fad, they could be groundbreaking and a rebel but doing this and proving it works. But it was devised by non-AGD employees so it won't make it past this thread probably... it's fun thinking of it anyways