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AirGunEric · Site Admin

Let me ask this:

Where does this 150psi and such come from? Regulators used in paintball HPA setups are not that precise and can only be adjusted accurately down to about 400-450psi output.

Also, the 150psi is NOT GOING TO WORK with a metal projectile- See SMP's comments above and get off this low-pressure idea, it WILL NOT WORK in this application.

SMP · Silver Status Member

Eric I think the guns have a secondary regulator built into them which allows them to pass equipment check on hot and cold days (300fps max) They can also adjust for close quarter soft shots all the way up to long range, leave a welt on your A$$.

NZShooter
I don't think things are as grim as they seem here. These guns run unregulated CO2 and are UL approved. So they have to have a design pressure of about 1500psi to account for worst case scenario. All of our CO2 driven air rifles run in this pressure range as well. So the idea is not off the rock. All of the work Bob does with springs and hammers these kids use solenoid valves and PLC's (remember the Rogue) same idea. As well I've noticed that these things are made of heat treat aircraft aluminum and chrome moly...we're not talking the plastic paintball marker from 25 years ago.

TheAznInvazn
Eric is conveying a good point here. below 600psi that pellet isn't even going to move so your not going to be able to regulate the gun down to what you would be able to in a paintball scenario. As I said earlier the area against which the force acts means everything less area= more pressure

Good Luck and above all be safe.

PS...You may want to do a little more to explain yourself so these Old Geezers don't have an aneurysm Mr. Green

AirGunEric · Site Admin

rsterne · Moderator

A few points....

Yes, paintball guns have a secondary regulator in them, that is how they can be adjusted to stay under 300 fps.... However, if you rip that regulator out, then you are working with unknown safety factors on the components downstream of it.... Paintball guns run electronic solenoids and triggers.... but to the best of my knowledge, they are only running on relatively low pressures (downstream of said regulator).... in the order of 150-180 psi.... I would seriously doubt if they will work reliably, or more importantly SAFELY if you dump 850 psi into them, let alone 1500-2000....

Don't underestimate what you can do with relatively low pressures.... My non-PAL .22 cal airguns run pressures as low as 450 psi and still achieve 500 fps, and in fact need the hammer spring trimmed to get down to that.... Also, don't underestimate the damage that can occur with an HPA explosion.... The most recent incident involved somebody disassembling a Disco that still had about 1000 psi in it (the gauge was faulty).... The fill fitting on the end of the gun blew threw his ceiling, taking the wrench with it.... and cost the guy a broken ear drum in the process.... Fortunately, he didn't lose his hand.... or LIFE.... The old adage applies here....

HPA IS DANGEROUS - IF YOU DON'T KNOW WHAT YOU'RE DOING - DON'T !!!

Bob

TheAznInvazn · Member

Paintball markers are designed to safely work at over 850psi pressures, such as the same for Spyders and Tippmann's which can run off of unregulated CO2
The marker that I will be modifying is specifically an Odyssey RPM, another marker designed to safely use both CO2 and HPA, and is made of solid billet aluminum with ample wall thicknesses. Its solenoid is actually a simple clapper solenoid that strikes a 3-way spool valve that actuates the ram. Nothing to over pressure, at worst, it would just need a replacement oring. The markers that require lower pressures to operate are;

1. more expensive (Angels, Egos, Dye, Proto, etc.)
2. really expensive... (I'm working with a limited budget and materials on hand!)

I appreciate the safety concern from all you guys, it goes to show that yall are willing to speak up and let me know if you think things can get out of hand. With that said, I'm no stranger to the potential hazards of HPA. After modifying my fair share of paintball markers, I've seen and experienced my fair share of mishaps and have learned from all of them.

If need be, I can run the pressures straight from the tank regulator to get maximum pressure to propel the pellet (850 psi or more), but I would love to see how it would work with a secondary regulator, lower pressures and a long dwell time, just as a type of experiment to sate my thirst for knowledge and just because I can never just take someone's word for anything, which has proven to be a problem in the past. I'm not sure why my setup, if set to under 500psi, can't just keep the valve open for a longer period of time to expel the pellet. Sure it may not go very fast, but I don't see why it wouldn't work at all.

With that all said, the current setup I have in mind will have three regulators! A tank reg, a shooting pressure reg, and a low pressure reg that feeds the air ram assembly that strikes open the valve. If pressures are insufficient, I can then proceed to simply delete regs from the design with minimal effort to reroute the air.

As this idea keeps evolving, and as parts begin to come in, I will keep you guys posted, and before I stick this thing in any kind of stock, I'l be doing a shooting test with just the parts linked together until I can get it to operate the way I'd like it to!

If I've missed something, or if any of you guys would like further clarification on anything, please feel free to ask! i'd like to make things as clear as possible now, and if I've missed or overlooked something, I'd rather find out now as well!

rsterne · Moderator

I have a spreadsheet where I can put in lots of variables and get a rough idea of what is going to happen.... I used as a baseline the following....

24" barrel, .22 cal, 14.3 gr. pellet, 13 CI tank, 60% efficiency (which is high, you are unlikely to achieve this).... and I set up the program for a "dump shot".... ie the valve is open until the pellet leaves the barrel.... producing the highest possible velocity for that pressure....

150 psi - 295 fps - 2.8 FPE
200 psi - 423 fps - 5.7 FPE
250 psi - 488 fps - 7.6 FPE
300 psi - 536 fps - 9.1 FPE
350 psi - 578 fps - 10.6 FPE
400 psi - 616 fps - 12.0 FPE - air used 26 psi per shot

Now using 850 psi with "proper" valve timing to produce the same shot as above at 400 psi....

850 psi - 616 fps - 12.0 FPE - air used 8.5 psi per shot

In this case, the valve is closing when the pellet has only moved about 3.25" down the barrel.... by which time it has reached 375 fps.... It gets the other 240 fps from the "free expansion" of the air already in the barrel.... In other words, you can get the same performance by using a higher pressure and closing the valve sooner and use only one third as much air per shot....

But, like you say, you prefer to do your own thing.... and I'm sure you will have a blast doing it.... Incidently, the remaining pressure at the muzzle using the 850 psi / short valve timing setup is 121 psi.... Using 400 psi and a dump shot it is 374 psi.... Since muzzle blast is proportional to muzzle pressure, having a "blast" will be literal.... the gun will be VERY noisy compared to what could be achieved.... I love seeing somebody excited about a new project.... I just want you to have reasonable expectations, and to stay safe....

Bob

TheAznInvazn · Member

Wow, thanks for that info!
So it seemed like some of yall were saying it would be impossible to move the pellet with pressures below 600 fps, but according to your data, it would just be falling right out the barrel (which was what I was expecting)!

I guess I don't need to test that, and as for the pressure used, if I buy myself a Ninja paintball tank with an adjustable reg, I maybe able to squeeze out a few more PSI out of the regulator (maybe closer to 1000psi max). If I do that though, I'd going to need to use steel braided line instead high pressure nylon tubing like I was thinking of using. Safety is indeed big in my book, so I'd rather over do it than have lines bursting on me.

I also plan on making my own shroud that will be permanently attached to the barrel. I've read up on some laws, and to my knowledge and from what I understand, as long as the shroud cannot be removed from the air rifle, it's legal. If this is incorrect, I will absolutely obey the law and not make this.

rsterne · Moderator

Ninja regulators can be tweaked up to 2000+ psi by changing over to Belleville Washers (disc springs) instead of the coil spring.... Ninja sell high pressure regs already done that way as OEM parts, but at a significantly higher price.... I regularly use them tuned for 1500-1600 psi which is as high as you can go and still keep the 1.8K burst disc on the downstream side.... I like that as a safety feature, as any CO2 gun SHOULD be able to stand that.... because CO2 can reach 1900 psi at 120*F....

Bob

TheAznInvazn · Member

Glad to hear!
Are you running those pressures to get better efficiency, or just because it's needed to get the FPE you want (or both)?

Now I just want to find a 22ci tank and slap a ninja reg on it

SMP · Silver Status Member

Yes sorry about that I should have explained myself better on that 600psi comment. When I said wont move I should have said wont move along at at a at a reasonable clip

Be very aware that what Bob can achieve and what ordinary mortals can aspire to are two entire different matters RazzDouble

I think this is a great topic and if it all works out well we may be calling you Sikes Jr Mr. Green

Your idea is excellent. VVT(variable valve timing) are indeed how ePCP works.

TheAznInvazn · Member

I've been wanting to do this project for a while, so I've had time to think about how things will work
Smile

If this ends up being a success (able to hunt small game), then I'll be quite happy!

rsterne · Moderator

BOTH!....

Bob

radar · Silver Status Member

TheAznInvazn · Member

Thanks for all the input everyone!

I have a few parts on order as of now, and it may take a while to complete this. Mostly going to be worked on the weekends and after I finish a prior project of sorts.

In any case, I'm feeling that I should be able to get a decently accurate air rifle that can hopefully get somewhere around 15 FPE or more!

Bob, I have the option of using a lighter ram and a heavier ram to smack my poppet valve open. What were your findings with different weight hammers? I remember reading something in your thread about that, just don't remember what you ended up sticking to

rsterne · Moderator

Hammer strike must be balanced against fill pressure to get a proper shot curve on a "smack open" valve.... You can increase hammer strike by increasing preload and/or increasing travel, and to a lesser extent by increasing hammer weight.... It takes quite large changes in hammer weight to get much change in valve lift/dwell.... Generally, lighter hammers tend to be more consistent but need more spring preload to make up for the reduced momentum....

Bob