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

[nicad]

Josh- your alive!

I wouldnt go assumeing that AGD has tried and thought of everything. Last I talked to Tom about decreasing the dump chamber size, he said that that would be something to look into and that he wanted to know what numbers I come up with.
just havent had the time to strip down a valve and give full attention to to the project.

out!

[pbjosh]

Colin! How is it going?

I personally do not thing the blowforward design has been optimized yet. Maybe in the new ICD gun, but we have had quite a few guns (desert fox, equalizer, badger) that used the design, and while it works great for higher pressure applications, it doesn't have the same effecientcy as other guns at any lower pressure.

The blowforward design = high pressure operation.

Not the dump chamber. The dump chamber designs can now almost equal the AKA poppet setups.

But the operation of the bolt being blow forward, and the related air paths, and related action, seem to almost always end up with a high pressure application. In the equalizer, which had no sear, the valve chamber could be ran at 300 psi or 600 psi by inserting a tube/spacer to run at higher pressure. The energy usage differential between the two pressures was very high. The low pressure used nearly twice the air.

I would like to see an effecient blowforward, the design is a great one, simple and elegant, but it is a (relative) high pressure operation.

Though I would like to be proved wrong.

While I would LOVE to show you guys the internals of the Shiva and how I get the energy usage I do, you will have to wait a few months yet,

Josh

[QUINCYMASSGUY]

Shiva?

The Shiva? Oh come on, give me a little clue, never heard of this. Whole new marker design? Blowforward? A vague detail at the least would make my day

[hitech]

Originally posted by pbjosh
While I would LOVE to show you guys the internals of the Shiva and how I get the energy usage I do, you will have to wait a few months yet...

And I would love to see it! Maybe you should show me your ideas so I can "verify the validity" of your design. Tom did say to me at AO SE II, and I quote, "You already know more about gun design than most manufactures". I am the "perfect" person to “verify the validity”. You buying any of this?

BTW, Tom really did say that to me.

[pbjosh]

Well,

Shiva notes are on pbnation:

http://pbnation.com/showthread.php?s=&threadid=36097&highlight=%2Bshiva

and:

http://pbnation.com/showthread.php?s=&threadid=42476&highlight=%2Bshiva

Though it had changed a bit here and there. It is currently Open bolt, 110 psi operation, and a couple other neat tricks I have up my sleeve.

hitech-

Same here buddy. While not 'validated' by Tk myself, I have had quite a few conversations with manufactures, especially when I was doing the Racegun thing, and I can easily say I know more than alot of manufacturers myself. It doesn't take much actually. Hurt my brain to try and tell Shocktech anything about tuning a cocker, infact the WGP bolt is larger, now .683" instead of .679" because of my indirect input.

As much as you would like to, you can 'validate' my design when everybody else can also.

I have discarded Mayhem, the new ICD, and the 03Shocker design cues in the pursuit of the Shiva, so wait and see-

And since this thread is about energy usage per shot, any more input, or should we start another thread? How to improve Blowforward design. That is how the Shiva was started anyways.

I have a drop in close bolt kit for a mag floating in my mellon somewhere-

Josh

[hitech]

Originally posted by pbjosh
hitech- Same here buddy... As much as you would like to, you can 'validate' my design when everybody else can also.

I’m not sure, but I think you might have misunderstood me. I was joking. Completely; didn’t mean it at all. My meaning must not have come across. Sorry for the misunderstanding.

[pbjosh]

Oh, I did take it as a joke!

I didn't take a lick of offence to it at all!

I think I wasn't clear. As it sits- NOBODY else will get to see how the Shiva works till more paperwork gets done....

....then, yep, come on over! I really can't wait to get the new version finished, and when I done I will let whoever test till it breaks. I am fairly confident it will take quite a bit.

Josh

[hitech]

Originally posted by pbjosh
Oh, I did take it as a joke!

Okay, good.

Originally posted by pbjosh
As it sits- NOBODY else will get to see how the Shiva works till more paperwork gets done....

Probably a VERY wise move.

[SLICEnDICE]

Decreasing dump chamber

Isn't that the same idea as the hypermag that was out a few years ago. Small chamber size, higher pressure, increased efficency?

[pbjosh]

Yes, the idea is the same.

I think the Bolt/Dump action, where the two interact, should be looked at. I think we can get the Blowforward design to work at lower pressures, and not use so much energy per shot.

Looking at how the bolt transfers air, how the spring affects the action, are going to require some serious thought, and we might never know.

I am willing to put my noggin into the fray though-

Josh

[hitech]

As I see it there are two problems with the blow-forward-dump-chamber design as implemented in the automag.

1 The airflow is restricted. The power “piston” provides too much airflow restriction and the power tube diameter is too small. This necessitates “long” acceleration times. The longer the acceleration time, the more volume behind the ball, the more air is needed.

2 The bolt doesn’t return and close off the dump chamber fast enough. Air is still being “dumped” from the dump chamber after the ball is gone. All of this air is being wasted.

If you could accelerate the ball in two inches or less and either use all the air in the dump chamber or close it off after the ball has reached the desired velocity you would see a dramatic increase in efficiency.

A thought I had was for a boltless “blow-forward” design. A “door” would travel forward in the same manner as the bolt does now and seal the breech. The dump chamber would be opened as it reached the door sealed. The opening would be huge and the dump chamber would be small. How fast the air could be delivered to the paintball is the key to this design. It needs to be an almost “all at once” delivery. Haven’t worked out the details as I’m not really going to do anything with the idea. Just food for thought.

[bjjb99]

Yes, I'm still here... just lurking and thinking.

A very interesting topic. I've been noodling on variable pressure and volume dump chamber designs for almost two years now. My initial post to this forum on the subject can be found here:

http://www.automags.org/forums/showthread.php?threadid=22414

... though there's not much there, just the beginnings of some thought experiments. At one point I had a basic Excel spreadsheet floating around that allowed folks to compare different pressure/volume settings versus the barrel length, the paintball's exit velocity, and the residual pressure in the barrel. That spreadsheet did seem to indicate that efficiency increased when one used a high pressure, low volume dump chamber and delivered the gas as quickly as possible.

Aside from frictional effects from a longer barrel, I'm not entirely convinced that accelerating a ball to 300 fps in six inches with zero residual pressure at the ball's exit is any more efficient than accelerating a ball to 300 fps in 12 inches with zero residual pressure at the ball's exit. The acceleration distance may be a natural result of delivering high pressure, low volume air to the ball. I think this is going to require me to dig up that old spreadsheet and try some different barrel lengths.

I really, really wish I had the space for a decent set of machine tools so I could actually fabricate some of the stuff I've got around here on paper... paper paintball guns just aren't as fun to fire.

BJJB

[athomas]

I have to agree that there is probably several combinations of efficient conditions to accelerate a paintball to 300fps.

I also agree very much with hitech in his thoughs. I bet we could keep a fairly small chamber and a lower pressure if we could release all the air pressure at once. It would be a precise, measured amount of air with none "seeping" out after the ball is gone because the bolt/valve wouldn't be closing off an air source. The entire air source would be used and instantly (at least as instantly as possible) available.

[KRAKMT]

Just a spark not fully thought out but what would be the result if someone were to remove the bolt spring on a lx mag and replace the return force with a pneumatic ram? Thus decreasing some of the pressure in the chamber necessary for loading the spring. Using the levelx the bolt would gently as necessary blow forward more efficiently and return faster?

[cledford]

Instead of producing inserts to reduce the size of the valve chamber, has anyone thought of drilling a honking large hole directly into the valve chamber (from the outside) the threading it to accept a large set screw? Then you could just "dial" in the set screw to reduce the air chamber size.

-Calvin