Pneumatic anti-armor gun (mini football launcher)

[ardrummer292]

Hey all, dunno if this sort of discussion breaks forum rules. If so, I apologize.

 

***Disclaimer: you know that guy that packs for every possible eventuality? The guy that looks like he's moving out when going to a big event more than a few hours away? The guy that owns stuff that can't really be used during the average weekend pickup game? Yeah, I'm that guy.***

 

 

Have you ever been to a bigger op that incorporates vehicles as simulated armor? If you have, I'm sure you've noticed that very few people have the means to defeat such threats. Most event organizers require that anti-armor ordnance is either 40mm TAG rounds or small Nerf pocket footballs fired from a launcher. TAG products and homemade launchers are both pretty uncommon, but I think the latter will be more affordable (and reliable to boot).

 

I've been working on a design for the past week and could use a fresh set of eyes. It's a multi-shot capable breech-loading pneumatic launcher, which I hope to create in a fairly similar form to the Carl Gustav 84mm recoilless rifle. The pneumatic layout is as follows:

 

High pressure source: 20oz CO2 tank @ 800psi

->

Regulator: 800psi down to about 125psi

->

Directional Control Valve (DCV): contains firing solenoid / routes gas to secondary chamber

->

Secondary chamber: holds set amount of CO2 gas @ 125psi for firing

->

Quick Exhaust Valve (QEV): on signal from DCV, releases gas from secondary chamber into...

->

Barrel: 2 inch Schedule 80 PVC

All of the above were taken from here: http://www.instructables.com/id/Versatile-Multi-shot-Pneumatic-Cannon/?ALLSTEPS

 

I'll include drawings, a parts list, and my questions a bit later on today. Watch this space.

[titchikov]

So you'd be able to just chuck another round down the barrel and trip the solenoid again to reload? Clever

[ED-SKaR]

It's a qev air rifle scaled up. I've been meaning to build one of these for multi purpose ammunition.

[ardrummer292]

What do unemployed engineers do? Think up a project, create a conceptual design, get the rough layout on paper, and find some performance analysis software to refine the design specs.

 

[sharedmedia=gallery:images:15975]

Cutaway view of the main launcher body and breech cap sections. The main body will be 6in PVC, which houses all the "worky bits."

 

[sharedmedia=gallery:images:15976]

Loading process. The breech locking mechanism is a cam-in-groove / camlock fitting, similar to those used on fire hoses.

 

[sharedmedia=gallery:images:15977]

Performance analysis using GGDT (Gas Gun Design Tool).

 

 

 

So you'd be able to just chuck another round down the barrel and trip the solenoid again to fire, without having to manually repressurize the chamber? Clever

 

Fixed.

[Roland1014]

Just have a TAG shell rifled section screw into it so you can chuck TAGs at super velocities.

[ardrummer292]

The problem is getting a 27 inch piece of rifled 'barrel' for the TAG round.

[renegadecow]

Not to mention you'll need to calculate for the new rifling pitch if shooting velocities over what regular TAGs do.

[ardrummer292]

Not to mention you'll need to calculate for the new rifling pitch if shooting velocities over what regular TAGs do.

Yup. That said, if I could fabricate a properly spec'd rifled barrel for TAG rounds, I'd do it.

In the meantime, I'll stick with the easier to source (and equally antiarmor effective) Nerf mini footballs.

[ardrummer292]

I've finally knocked out the bulk of the parts list for this build. Here's the screen caps from my Excel sheet:

 

[sharedmedia=gallery:images:15981]

[sharedmedia=gallery:images:15982]

 

My eyes bugged out a bit when I saw the total. 1350 USD is a lot to sink in to something that won't be used that frequently. Does anyone see where I could cut some of the cost?

[mimesis]

Ask NonEx what some of his pistol builds have ended up costing.  That might put things in a different perspective.

[ardrummer292]

As the former owner of an Inokatsu MAG 58 and current owner of a CA-based L110A1, I'm painfully aware of how expensive specialty weapons can become. It's really a matter of justifying the expenditure.

That said, I've come this far. It would be a bit silly to put all this work in and not build it.

[druid799]

Yes it's gonna be buttock clenchingly expensive to manufacture and quite a project .
BUT to have a working Airsoft Charlie G ? WoW !
If and it is a very big financial if (which I know I couldn't couldn't afford) but if you can mate , I say crack on and claim your place in the anoles of Airsoft legends !

[paranoiddroid]

Look at your internals and post them up on spudfiles to see how people like Ragnorok and JSR would simplify the design possibly.

I know they have built repeaters for allot less than that allot will be the intricate machining work in your plans it feels like and i could be way off base but you need a none engineer or another engineer to look over your stuff and go this is more complex than it needs to be or have you thought of this kind of feedback.

I'm slowly working on a mortar I want to have a similar multiple shots without manual pressurisation firing mech though mine will be muzzle loaded (I'm thinking the dropped round triggers the valve opening at the moment)

So good luck and hell a Charlie would be badass. I'm also working on a much simpler drainblaster law using a pump. So i understand the this would be cool and this and this but you end up with something really complicated and perfect because It's your baby, your hard work designing it.

Sorry I can't easily give any detailed feedback because I'm not confident, iv read allot and not built much in terms of guns like this so i don't feel I have the experience to criticise.

[ardrummer292]

Thanks for the input. I think I'll follow your advice and ask some experienced "spudders" for their thoughts.

[renegadecow]

I think what's driving the cost up is having an automatic filling source. If you reload manually, you can cut out a lot of the fittings, change the regulator to a cheaper overpressure relief valve, and just have QD connectors between tanks. Basically you attach the hose until the relief valve blows over then disconnect and reload projectile.

[paranoiddroid]

Honestly im not so sure that his desire for the tank to be auto filling after each shot is the issue just hes going for a fairly expensive at of doing it and simply for safety and field liability id say that having a regulator to monitor the psi is pretty much mandatory really even if just for piece of mind and ranging.

I'd suggest that he looks at his breech design as a sliding breech will be much easier and cheaper to make and iv seen that done on some fairly big guns (there's a guy with a howitzer launching nerf footballs like full size ones on YouTube who uses a sliding recoiling breech for example. The sliding breech would be faster and opens the door to some interesting payload options if you use pvc shells with a stop in the barrel so the shells don't fly out merely using them as projectile holders. Canister shot with tennis balls or foam balls or even a cup of bb's hell iv wondered for a while if the rebelle arrows would work as flechette type ammo. They'd certainly scare the heck out of people whistling on target. Would be expensive though.

I honestly think that the cost will get dropped when the design is reviewed your QD fitting idea RC is an awesome one.

[ardrummer292]

Can you link me to a video of the sliding breech design you mentioned?

[DarkLite]

Can you link me to a video of the sliding breech design you mentioned?

 

Might be this one?

 

https://www.youtube.com/watch?v=odbIbTxocjM

[paranoiddroid]

Yeah the breech shown in the first 30s or so was what i meant by the sliding breech, it's easy to load just dropping a projo into it. His shell issues are more about shell design and length of the breech than anything else.

The second one he showed he field piece is cool but I'm not sure how it works to be honest.

[ardrummer292]

Oooh that second one is cool. I'd love to have a canister of sorts to contain the Nerf rocket. That would mandate removal of the old expended canister (or 'shell,' I guess) like the real Charlie G. It wouldn't auto-eject like his, of course.

[DarkLite]

Is there not scope to make the 'auto fill' function mechanical instead of relying on a very expensive and complex solenoid valve?

 

For example, having a valve that's actuated by the camming action of the breach block?

IE: When you unlock the breach, it trips a lever to open the refill valve, then when you lock the breach it closes the refill valve.

 

If you had it actuated by the locking lever you could then 'top up' the charge on the fly without having to open the breach entirely every time.

[paranoiddroid]

ERN honestly a QEV is probably the cheapest way to do this sort of auto refill thing

And yeah having the foam football in a canister is probably the easiest way for quick reloading just load shell fire clear out the cartridge reload.

[ardrummer292]

Is there not scope to make the 'auto fill' function mechanical instead of relying on a very expensive and complex solenoid valve?

 

For example, having a valve that's actuated by the camming action of the breach block?

IE: When you unlock the breach, it trips a lever to open the refill valve, then when you lock the breach it closes the refill valve.

 

The QEV valve is integral to the design of the launcher, as it performs both the function of refilling the secondary chamber and rapidly releasing the secondary chamber's contents into the barrel. As my design currently stands, the refilling and firing functions cannot be separated.

[DarkLite]

The QEV valve is integral to the design of the launcher, as it performs both the function of refilling the secondary chamber and rapidly releasing the secondary chamber's contents into the barrel. As my design currently stands, the refilling and firing functions cannot be separated.

 

Fairy muff. I was thinking about drastically cutting cost by making everything mechanical, though in that case breach loading would be difficult.

[ardrummer292]

The breech-loading function is going to be a pain. That said, I don't think I'd be satisfied with the design if I couldn't load the launcher in a similar fashion to the real thing.

On a related note, I'm tempted to design a mortar using a similar pneumatic setup to the one I have here. It would fire the larger Nerf Vortex Mega Howler footballs. I could place the pushbutton switch at the base of the barrel so rounds would automatically fire.

'Hanging...'
'FIRE!'

I really shouldn't be re-watching The Pacific. It's giving me all sorts of ideas.