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Recoilless air cannon, possible?

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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Recoilless air cannon, possible?

Unread postAuthor: Alex345 » Mon Dec 26, 2016 2:53 pm

I'm thinking about building a launcher that can lob large projectiles from the shoulder with the least amount of recoil possible.

I know that adding any of these systems to an air cannon (Assuming a QEV/piston cannon) adds a large amount of weight, complexity and loss of efficiency. I don't mind this, but i'd like to know if some of these theories can work;

Counterweight: After the piston valve a 90° elbow goes to a T fitting with each end having an adapter piece to fit a barrel on the left and right end of the T fitting. The front end would have the actual barrel and the rear end would have half the length of the front barrel.

The longer front barrel would hold the projectile, whilst the shorter rear barrel would hold a counterweight that's the same size as the projectile; but twice the weight, to match the shorter barrel. When the cannon fires it would perfectly divide it's power to fire both projectiles, thus eliminating recoil. This is the most complex and cumbersome method, but it's one of which I'm certain would work.

Venturi nozzle: This idea i got from the Carl Gustav recoilless rifle; It has a big bore barrel with a venturi breach at the rear to create just enough back pressure to negate the recoil from firing the shell.

A piston valve would be fitted with a 90° elbow piece that goes to a T fitting. The rear side would have a union fitting with a washer inside of it to reduce airflow. That union fitting would go to an adapter piece at least twice the size of the T fitting to create the venturi effect. The front side of the T fitting would connect to the barrel and hold the projectile.

Whilst i do think this one might work, i doubt that gas powered cannons can provide the amount of gas needed to make the venturi system work. Maybe this would work on a powerful hybrid?

Any other ideas?
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Re: Recoilless air cannon, possible?

Unread postAuthor: jankokes » Mon May 22, 2017 4:41 am

The first option would work. As for second option, I don't see any reason why Venturi effect wouldn't work. Something like this would work, too:
samopal.jpeg

But it requires more then plumbing equipment. So does the adapter piece.
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Re: Recoilless air cannon, possible?

Unread postAuthor: jackssmirkingrevenge » Mon May 22, 2017 8:24 am

Venturi nozzle: This idea i got from the Carl Gustav recoilless rifle; It has a big bore barrel with a venturi breach at the rear to create just enough back pressure to negate the recoil from firing the shell.


Not really practical, you would literally need a chamber about 4-5 times larger in volume before sufficient air was available for this to happen.

I think it's a better idea to incorporate a system that spreads the recoil, ie allowing the barrel some dampened movement on a fixed mount, something like this:

Image
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Re: Recoilless air cannon, possible?

Unread postAuthor: jankokes » Mon May 22, 2017 1:29 pm

Here is another suggestion (blue arrow up, green arrow towards target):

ustovaBrzda.png
ustovaBrzda.png (21.19 KiB) Viewed 530 times


This option lacks the drawbacks of already stated options:

1/ Nobody behind you will get blast of gases as in second option, or get hit by an object twice the mass of your bullet as in fist option

2/ It will be much easier to make (standard plumbing equipment), easier to clean (if joints are threaded) and less likely to suffer permanent damage than Spagin

Otherwise it will keep the benefits of Spagin, preventing both recoil and muzzle jumping up. The pinhole may or may not be required however it will make it less likely you will shoot the whole appendix off.
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Re: Recoilless air cannon, possible?

Unread postAuthor: Alex345 » Mon May 22, 2017 5:10 pm

Oh wow, I posted this like 5 months ago and i haven't visited the forums in a while now. Yet just tonight i was thinking "i wonder if there's anything new on spufiles" and saw this topic at the top of the recent posts list haha! I still have all the parts lying around and i occasionally think about building this thing, i might just mess around with this idea a bit more in the near future.
jackssmirkingrevenge wrote:Not really practical, you would literally need a chamber about 4-5 times larger in volume before sufficient air was available for this to happen.
What about using high pressures? Or actually narrowing the nozzle to create more back pressure? More like a Laval nozzle rather then the Gustav's "venturi" nozzle? Like adding a union fitting at the back and using washers with different sized holes until you find a sweet spot? More like the design of an RPG-7:
rpg10.jpg
rpg10.jpg (11.43 KiB) Viewed 515 times

jackssmirkingrevenge wrote:I think it's a better idea to incorporate a system that spreads the recoil, ie allowing the barrel some dampened movement on a fixed mount, something like this:

Image
Hah! I remember that thing, high impulse weapon something, from France if i remember correctly. You forgot the second part where the other guy got his ass kicked by that thing! :D Not exactly low recoil tho :p I had been thinking of building a stock from an old pneumatic cylinder to absorb some of the kick. All made the thing a lot more bulky and heavy tho, which i guess also helps with recoil, but i'm not Joerg Sprave :mrgreen:

jankokes wrote:Here is another suggestion (blue arrow up, green arrow towards target):

The attachment rpg10.jpg is no longer available


This option lacks the drawbacks of already stated options:

1/ Nobody behind you will get blast of gases as in second option, or get hit by an object twice the mass of your bullet as in fist option

2/ It will be much easier to make (standard plumbing equipment), easier to clean (if joints are threaded) and less likely to suffer permanent damage than Spagin

Otherwise it will keep the benefits of Spagin, preventing both recoil and muzzle jumping up. The pinhole may or may not be required however it will make it less likely you will shoot the whole appendix off.
How would all the air not just simply escape from the back instead of pushing the projectile out? Your design is kinda what i had in mind with the counterweight, but the green arrow would be where the weight was sitting and the projectile would be in the longer barrel. I guess i could use a bag of water as a counter weight to reduce the risks of damaging something or someone standing behind it.

I don't get the PPSH reference tho? It's a big heavy gun firing a small pistol round, that's why it has so little recoil, i have a semi auto conversion on license and it still kicks tho :p Or are you referring to the barrel shroud acting as a crude muzzle brake?
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Re: Recoilless air cannon, possible?

Unread postAuthor: farcticox1 » Mon May 22, 2017 5:39 pm

Image

Did something actually come out of the other end :shock: it's hard to tell
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Re: Recoilless air cannon, possible?

Unread postAuthor: jackssmirkingrevenge » Mon May 22, 2017 9:45 pm

Hah! I remember that thing, high impulse weapon something, from France if i remember correctly. You forgot the second part where the other guy got his ass kicked by that thing! :D Not exactly low recoil tho


Yes, the Lacroix "Samourai":

Image

A lot of recoil but consider that it's firing a projectile that weighs about 1.5 kilograms out to more than half a kilometer, presumably you're planning something slightly lower spec...

What about using high pressures? Or actually narrowing the nozzle to create more back pressure? More like a Laval nozzle rather then the Gustav's "venturi" nozzle? Like adding a union fitting at the back and using washers with different sized holes until you find a sweet spot?


It will still be disproportionate to the amount of gas you need to balance out the recoil - rule of thumb with recoilless guns is about only 20% of the propellant pushes out the projectile, the rest is countering the recoil. I don't think it's worth the waste really.

Another system to consider is "soft recoil", like the 105mm "Hawkeye" demonstrator:



Basically the barrel starts in its full recoiled position, at the moment of firing it is released and the projectile is timed to fire right before the barrel reaches its rest position. You have to time it right of course, but it definitely does make a huge difference.
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Re: Recoilless air cannon, possible?

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Re: Recoilless air cannon, possible?

Unread postAuthor: GalFisk » Sun Jun 18, 2017 12:16 am

How about launching water out the back? That can be made as heavy as you like and is relatively harmless.
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Re: Recoilless air cannon, possible?

Unread postAuthor: jackssmirkingrevenge » Sun Jun 18, 2017 6:05 am

relatively


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Re: Recoilless air cannon, possible?

Unread postAuthor: Alex345 » Fri Jul 28, 2017 9:12 am

jackssmirkingrevenge wrote:
relatively



If i was rich I'd buy two of those, put wheels and a chair on them and drag race them with friends and a few beers :D Seems like a small chamber tho, what valve does that beast use?

Maybe a dual burst disc hybrid would work with a Venturi breach? Tho one disc might fail to break, either breaking your shoulder or throwing the whole cannon forwards out of your hands... Don't like that thought.

I'm currently finishing up on a new cannon setup, using my large piston valve that i normally opened using a 1/4 ball valve with a string. This time i modified the push valve of an old CO2 extinguisher to make a a crude but very high flow hammer valve. If all goes well i should be able to test it today :) If that shoots well... Who knows i might try the counter weight method. And yes water (possibly with salt) has also crossed my mind, just need way to contain it but that's the least of my worries for now :)
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Re: Recoilless air cannon, possible?

Unread postAuthor: jackssmirkingrevenge » Mon Jul 31, 2017 9:04 am

Seems like a small chamber tho, what valve does that beast use?


Here's the manufacturer's page, no details about the valve but I guess it's an exhaust valve of some description.

Who knows i might try the counter weight method. And yes water (possibly with salt) has also crossed my mind, just need way to contain it but that's the least of my worries for now


Worth mentioning the Armbrust:

Image

It not only launches a plastic countermass but is also a "closed circuit" system that completely contains the propellant gasses meaning it has negligible noise and flash signature.
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Re: Recoilless air cannon, possible?

Unread postAuthor: Dig_Gil » Tue Aug 01, 2017 11:45 am

Maybe I'm late to this thread, but here's my two cents:
A truly recoiless weapon must eject something at the rear. Having a contained counter-balance like a counterweight that moves inside the gun will not eliminate recoil, only delay (like the AEK models of AK rifle) or redirect it (as in the Kriss Vector). So these aren't true recoiless weapons. They can be made more ergonomic by extending the duration of the recoil, so that it is less force at any one moment and less abrupt, tho. Remember that adding features to a gun will make it heavier. Fundamentally, heavier guns have easier recoils inherently, so a recoil managing system might be a thing with diminishing returns where it quickly is too complex and helps very little compared to just making the gun heavier.

Man handed rocket launchers exhaust gas. For effective compensation, half of the energy produced by discharging must be released in both ways. Because gas is much lighter than the projectile, you have to push it faster through the rear. That is rather inefficient for air launchers because it means you are dumping more than half of the chamber's pressure away from the projectile.

An obvious solution is to make as if duct-taping two launchers that share the same trigger. Each shooting the same mass at the same gas pressure. This would make an extremely effective solution, but also a danger in most shooting ranges.
Here's a small caveat you can exploit: your rearward launcher doesn't have to shoot the same mass as the front facing one. It only has to eject the same kinetic energy equivalent. Maybe a much heavier mass with lower speed doesn't have to travel as fast and thus don't eject as fast. But here again comes into play the issue with diminishing returns in recoil delaying systems.

jackssmirkingrevenge, as always, gives an interesting alternative. Don't contain the counterweight, but the gas. I you can have a two-ended barrel (as in gas exhausting systems), but the rearward exhaust is made to push on a piston which is trapped when it reached the rear end of the launcher. This piston will act as platform that transmits the energy to an actual ejecting mass. Once the piston is stopped, you'll feel some added recoil as the trapped gas is pushed forward, but it will be greatly delayed recoil. This is kinda of an hybrid of all the other ideas, if you think about it. Maybe allowing the trapped gas to escape perpendicularly will help dissipating the late recoil.

If I wanted to manage recoil in a launcher of mine, I'd built it like a Kriss Vector. It isn't recoiless, but aligning the barrel with the wrist (thus having a low bore axis) will prevent the recoil from having any negative effects but the fact that it hurts. If you have large launcher that needs to be shoulder mounted, you'd better mount it on the ground instead.

In any case I want to present this idea and you tell me what you think:
Recoiless.png
Launcher within a launcher


Maybe this could be improved by instead of having the fixed barrel extension segmented off from the interior launcher, make it enveloped as in arrow shooters, but whatever...
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Re: Recoilless air cannon, possible?

Unread postAuthor: jackssmirkingrevenge » Tue Aug 01, 2017 6:18 pm

Why not just use the launcher itself as the countermass :D As silly as it sounds, this is exactly what the Germans did with the SG500 Jägerfaust.

Image

By launching the shell one way and the barrel the other, it was able to fire a 1 kilogram projectile at supersonic speeds with zero recoil on the aircraft.

Image

I can imagine a valve feeding into a ported barrel that weighs the same as the projectile and is free to fly off in the opposite direction.
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