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rapid fire mortar

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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rapid fire mortar

Unread postAuthor: quiggly17 » Sun Dec 30, 2007 10:54 pm

well i was searching on youtube today and i saw this does any one know how it works or have an idea

[youtube]http://www.youtube.com/watch?v=FVaPVzxFj4k[/youtube]
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Unread postAuthor: hi » Sun Dec 30, 2007 10:57 pm

it looks like it works off of co2, uses a qev, and the trigger is pop off valve, but im not sure. i am pretty sure its a qev though.
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Unread postAuthor: MrCrowley » Sun Dec 30, 2007 11:08 pm

Yeah looks like what hi said, the only problem the guy would have is he would need an ammo feeder, or someone to load it.

He gets quite a few shots off, not sure how powerful but I doubt it would be much as he would be limited to under 200psi for the QEV.
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Unread postAuthor: Killjoy » Mon Dec 31, 2007 2:36 am

I just checked the website. It does run off of regulated co2, regulated hpa, or pumped up with a bike pump. Thats definantly a qev, but I'm not sure what the triger valve is, looks kinda wierd.

Heres a picture of it
http://milsimlabs.com/mortar1.jpg
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Unread postAuthor: MrCrowley » Mon Dec 31, 2007 2:58 am

Trigger valve looks like a schrader in the pic, but he uses it like a pop-off in the vid.
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Unread postAuthor: grumpy » Mon Dec 31, 2007 4:12 am

that is a slide-check valve, that the quick connect is screwed into, it will vent the qev without having to turn the pressure on and off , sort of a oneway pressure relief valve.
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Unread postAuthor: mark.f » Mon Dec 31, 2007 10:17 am

I think I get it.

He fills the chamber to a certain (relatively high, I'm guessing in the ballpark of 250 PSIG) pressure, and then triggers the slider valve. The valve only releases a certain volume of air or a certain amount of pressure before it reseals, which I do believe is a real-life version of slide valve, (have to check out some sites to see). This opens the Q.E.V. for only a short moment, before resealing it, (which he probably modified it to do that, by making an equalization hole in the rather well-sealing piston).

That's just my postulation, though. I could email the guy with it and see how close I am. Of course, proprietary information usually isn't disclosed just because somebody emailed an operating theory that was "close".

My clues as to this operation were:

1.) Lack of air input, suggesting a fixed volume of air at decreasing pressure.

2.) Sound of firing, which suggests a small volume of air at high pressure expanding through the barrel. This operation results in decreased performance, (think a paintball gun, where a small volume of gas at high pressure is let through a small porting valve to expand through the barrel), and a good choice for nerf rockets.

3.) Construction. Metal is more expensive than PVC, and if a manufacturer can get away with making the whole thing out of PVC, they will. The metal of the chamber is meant to withstand the high chamber pressures, whereas the barrel can be made of PVC because it's not subjected to high pressure once that small volume of gas expands.

Critiques?
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minimortar.gif
Note the addition of an equalization hole to the Q.E.V. piston.
minimortar.gif (8.28 KiB) Viewed 876 times
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Unread postAuthor: Skywalker » Mon Dec 31, 2007 10:50 am

I dunno. Those shots seemed really consistent, too consistent for him to be running off only a pressure chamber: I wonder if what we don't see is a line from a regulator snaking in from behind the fellow. OR else maybe there is liquid CO2 in that chamber (unlikely, though).

I did some experiments with a diaphragm valve gun, and what I found was that in order for the valve to reseat, the pressure in the chamber had to drop a certain percentage, say 10%, at each shot, so that only a handful of good shots resulted, with a noticeable power loss from one to the next. It would be extremely difficult to make a power drop so insignificant that you wouldn't notice it over the course of that video.

I say it's basically like clide's slider, and the air source is hidden for the vid.
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Unread postAuthor: grumpy » Mon Dec 31, 2007 11:07 am

no it was not modified, the slide valve will vent pressure as long as it is open. he was simply opening and closeing the valve quickly for effect. i realy don't think you could get an effective rate of fire this way, it would not be as impressive if he had actually been firing rounds out of it.
and with making a equalization hole in the qev you would no longer need to fill from the pilot valve, you could put a schraeder or quick connect in the chamber and get the same results. not all that impressive for the price, you could build your own alot cheaper and nicer looking.

Weight 6.5 pounds
Height 20"
Muzzle energy 40 Joules @ 120 psi
Ammo Nerf “Pocket Vortex” foam footballs, BB and Balloon SABO rounds
Range 400' with nerfs, 350'-375' with 100CC water ballons
ROF 20 RPM, that’s not a typo...a round every 3 seconds
Power Source Co2/HPA tank or bike pump (11 strokes)
MSRP $200
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Attachments
mortar1.jpg
notice the quick connect attached to the slide check valve.

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Unread postAuthor: pizlo » Mon Dec 31, 2007 12:28 pm

Weight 6.5 pounds
Height 20"
Muzzle energy 40 Joules @ 120 psi
Ammo Nerf “Pocket Vortex” foam footballs, BB and Balloon SABO rounds
Range 400' with nerfs, 350'-375' with 100CC water ballons
ROF 20 RPM, that’s not a typo...a round every 3 seconds
Power Source Co2/HPA tank or bike pump (11 strokes)
MSRP $200
I find a few of those figures hard to believe, he must be using a pretty hefty bike pump. This guy obviously does know what he is doing.
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Unread postAuthor: Killjoy » Mon Dec 31, 2007 6:37 pm

Well if I had 200 bucks as wall decorations I'd buy it just to see for certain how it works, but that seems unneccasary. I think we have the basic idea of how it works, so someone just needs to try it.
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Unread postAuthor: Novacastrian » Mon Dec 31, 2007 6:52 pm

350 feet with water balloons does sound a tad optimistic.
It would be uber fun if a magazine could be attached, you could have like 5 or so projectiles flying towards your target before the first one hit. I wonder how a cluster of paintballs would go.
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Unread postAuthor: POLAND_SPUD » Mon Dec 31, 2007 6:53 pm

I've always wondered... does slide valve is difficult to open/vent as the pressure increase ? you know like with quickdisconnect fittings - it really hard to disconnect them while pressure is > 300 psi.
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Unread postAuthor: Novacastrian » Mon Dec 31, 2007 6:56 pm

POLAND_SPUD wrote:I've always wondered... does slide valve is difficult to open/vent as the pressure increase ? you know like with quickdisconnect fittings - it really hard to disconnect them while pressure is > 300 psi.


In the vid it appears that he is holding onto the mortar rather tightly, it also looks as though he is having to pull the mechanism with quite a bit of force.
I would say that your assumption is correct.
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Unread postAuthor: Hotwired » Mon Dec 31, 2007 7:06 pm

It can't be using the semi-auto method I posted here about partially venting a QEV pilot. Theres too few components for a start.

I see a quick connection, a slide valve, a QEV, a metal pipe chamber and a plastic/metal pipe barrel.

There'll be an airline hidden behind his wrist. It's a simple slide valve venting QEV dumping the whole chamber of air each time and refilling from the airline when it's reset. Just as a slide valve is meant to be used. Except it's meant to have a pneumatic cylinder system instead of a QEV there.

No big secrets required.
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