Subject: Helium marker
From: Michiel N.
Dear Ydna,
I’m a Dutch engineering student working a school project and I would like to ask some of your advice. I hope I don’t bother you with this, but you might find this interesting. To give you some of the background: as I said I’m a student in Holland, studying at the Academy for Engineering in The Hague. My current project concerns a single stage gas gun with the goal of trying to upgrade the current design. We’re launching small (metal) projectiles with pressurized helium up to 20 MPa. The current design has some flaws and isn’t all that effective. After some research I got the idea of using the principle of a paintball gun, since the basics are alike. While I was looking for pictures of the inner workings of paintball guns, I quickly stumbled upon your website. I must sincerely thank you, for your website is the best on the web imho and is very useful! Anyway, my question. I noticed you’re quite knowledgeable when it comes to the subject of paintball guns. Do you think it’s possible and effective to apply the principle of a paintball gun on helium gas guns? First of all, helium atoms are smaller than air or carbon dioxide. To maintain pressure, the design need better seals and I wonder whether o-rings would do the trick. Secondly, it would mean the forces increase on the moving parts in the design, which might cause them to stop working properly. Of all the marker-animations on your site, I find the "spool valve, balanced shocker-based" design very interesting and I was thinking using this type of design. Among other reasons, the gas flow seems much smoother in > contrast to designs where the pressure chamber is located under the barrel. Do you think a smooth gas flow has much effect on the speed of the projectile? I’d very much like to know what you think of all this. Is this ludicrous and should I abandon the idea, or do you think it might just work? Hopefully you can give me some feedback and share some of your insights.

I hope you understand I will not use this information to upgrade existing markers or use it for paintball and/or on persons. This project is for research purposes only. For my project I’m researching multiple options and this is only one of them.
Sincerely,
Michiel N.

Re: Helium marker
Well, as you noticed, from a design standpoint the Shocker marker is one of the more basic systems out there. I make a big deal of the pressure chamber placement being so close to the breech, since other markers (such as the "Matrix") have the opposite layout, and as a result they loose quite a bit of energy per shot. In the paintball world this translates to getting less shots per tank fill, which you're probably not worried about, but it's worth mentioning anyways.

The other thing about the spool valve type systems is you'll probably find them much easier to fabricate. There's less components involved, certainly fewer moving components, so it should be quite reliable so long as you get the seals to function correctly. Paintball's spool valve systems are totally reliant on their o-rings, and even use them for physical support/stability in some situations.

I'm not sure about the issue of the o-rings using helium though. I haven't worked much with helium myself so I don't have much experience with it. That said, I would assume a few things...you can always go for a tighter seal with the moving components (put some crush on the o-rings, which is how they're used in most industrial situations) but the o-ring material can also be changed to something else pretty easily. As it is we use urethane o-rings most often but a stronger material might function better with the more energetic helium.
Are you thinking about retrofitting an existing marker to fire your projetile, or build a new one from scratch using a marker as template? The idea of retrofitting one for use with helium is really interesting to me...
-from Andrew "Ydna" DuBuc - [ZDSPB.com]

Re: Re: Helium marker
From: Michiel N.
Thank you for your response. To start with your last question, for the project we will make a design from scratch, based on existing markers. Indeed this is why I try keep it as simple and basic as possible. For more moving parts could mean more potential defects. And because of the usage of helium and the therefore tighter seals and fittings would mean more attrition. The projectiles are 0.2 inches in diameter, so I have to design the apparatus from scratch anyway.

Actually I was thinking about testing an existing marker with helium and higher pressure, just to see how it will react and where gas leaks might occur. But this would mean a lot more pressure would be applied on the paintball itself. I wonder whether a paintball would actually be fired or just burst open inside the barrel. The basis of my question lies in various websites that explicitly state that markers are not be tempered with. Since you have repaired a lot of markers I imagine you would know what can go wrong, or what the limitations are per design. Every form of feedback on this subject is more than welcome.
Sincerely,
Michiel Nederlof

Re: Re: Helium marker
For the most part I would assume warnings about tinkering with the markers are out there to avoid costly repair work from "homebrew" modifications. The biggest problem I have as an engineer is keeping people from breaking things on their own (either from improper regular use, or from improper maintenance). Of course the legal side of it is, companies don't want you to mess with the gun, because they won't honor the warranty afterwards.

The biggest issue with marker pressures would probably relate to the operating pressures for the internals. All markers that use a pneumatic solenoid will have some kind of set max pressure on the solenoid itself (usually between 100-200 psi depending on the solenoid manufacturer). If the marker design requires a firing valve pressure higher than the solenoid pressure, then an additional regulator is added for the solenoid...we refer to this as an LPR. Some markers use an LPR but not all, it really depends on the scope of the firing valve. For instance the Shocker solenoids can work at a max of 200-psi, and require 180-psi to fire the ball, so they don't have an LPR. But a Matrix uses a solenoid with max pressure of 100-psi, and they require a firing valve pressure of 150-psi...so they add an LPR to protect the solenoid.

In terms of testing, it'd probably be easier to use a marker with an LPR. They tend to be the more complex marker designs, but there's often more potential for tweaking. And in this case you'd be able to keep the solenoid LPR pressure low and increase the firing valve pressure higher than the marker is designed for (say, 300-psi) So, if you're going to fabricate a system yourself, you may wish to add a secondary regulator for the solenoid just to have that extra tuning ability. Regardless of the pressures, as long as the valve pressure is higher than the solenoid pressure, it'd be useful to use an LPR.

From a design standpoint, myself I tend to prefer the designs that isolate the bolt/loading mechanism from the valve. Something like the "Excalibur" or "Shocker Sport" animations listed on the anim page. The downside to these is the added pneumatics make the system take unusually long to fire (so they have a limited rate of fire) but you shouldn't be worried about that. But the other problem is those designs are larger and therefore require a higher number of new parts to be fabricated. They're not as simple as the integrated spool valve designs so it can be more complex to build. Myself I've never even undertook the task of fabricating a customized marker like that....all my projects are single-bore markers with minimum parts. It just takes too long to put that much work into it (lol)
-from Andrew "Ydna" DuBuc - [ZDSPB.com]

That's a very interesting project.