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Recoilless Cannon

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 Cannon

Unread postAuthor: From_Hamsterdam » Fri Mar 09, 2007 2:27 am

Recoilless Cannon

Image
Key: A= ammo(red) B= barrel Ch=chamber H= holes S= spring Green= counterweight

After building a gun to fire 390ml coke bottles I decided to come up with an idea to dampen the recoil. I used the idea from actual recoilless rifles as a base for my design. I have a “prototype” that decreases the recoil quite well by using a counter weight.
Here is the general idea:
The counter weight (in green) is pushed back when the cannon is fired, at the same rate as the ammo (in red) is moving forwards. When the counterweight reaches the back of its pipe it is stopped by a spring.

In depth look:
The force required to move the ammo is also applied to the gun. So if the ammo is say 500g then there is roughly 500g of pressure acting in the other direction on the gun. (Not taking in to account acceleration or friction). The counter weight has to weigh as much if not more then the ammo. With the counter weight added the force to move the counter weight in the opposite direction to the ammo counters the force of moving the ammo. Thus less recoil force.

Their is still some recoil because the counterweight stops before the ammo leaves the barrel. Also when the counterweight stops it will produce some force but this is dampened by the spring.

The counter weight has more effect if it travels further but a long gun is not much use. Having the counter weight travel a short distance (300mm-400mm) counters the force required to accelerate the ammo (which is a large chunk of the overall force). The pipe the counter weight is in is blocked by a clean out plug with a spring attached and a few holes in it.

Their is a loss of power but that is the same with all recoilless cannons. The loss of power depends on how far the counterweight moves and the diameter of the pipe. Tip: Having the counterweight airtight so no air can escape around it will also help with power.

Hope this helps any one planning on building a larger cannon or any one trying to launch heavy ammo. I also hope this post was understandable, despite my drawing I am more of a drafter then an engineer(and a hell of a long way from a english teacher).Depending on any tips/advice i plan on finishing the gun in about two weeks.

P.S.
Does any one know where in W.A. Australia I can buy PVC pressure rated parts that are over 50mm?
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Unread postAuthor: TwitchTheAussie » Fri Mar 09, 2007 3:05 am

Im a bit confused with your diagram but I understand the theory alright. Are you planning on adding this to your cannon? Also many people here sell parts. Some are Australian. Just ask around.
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Re: Recoilless Cannon

Unread postAuthor: MrCrowley » Fri Mar 09, 2007 3:54 am

From_Hamsterdam wrote:P.S.
Does any one know where in W.A. Australia I can buy PVC pressure rated parts that are over 50mm?


Private Message these members(note:username may not be correct just use * as a wildcard when searching)

killagorilla99
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rna_duelers
urban ninja

there are loads more members from aussie,those are just of the top of my head.
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Unread postAuthor: joannaardway » Fri Mar 09, 2007 4:28 am

This won't benefit you at all. It'll lose power, will probably break, and will have precisely no benefical effect.

Momentum laws prove this. Your cannon HAS to recoil with the same momentum as the ammo, excepting gas momentum. There is no way around this.

There is only one workable recoilless system - using rocket-propelled ammo in long tube, uncapped at either end, so there is no force on the launcher in the first place.

There is also a reduced recoil design, which redirects the gasses backwards with a muzzle brake, but that requires a similar mass of gasses to projectile mass - which isn't the quite the case in a spudgun. Although, using this method might have a minor effect, but not to the degree you seem to be looking for - also this only nullifies the recoil speed after the shot.

There is also little need to reduce recoil on a spudgun - there isn't enough in the first place that it will be a problem.

Although a spudgun may not be able to reduce the quantity of recoil, you can reduce the effect it has on aim. By putting a stock directly behind the line of the barrel, the recoil has no turning effect on the launcher as it fires.

So, by combining a stock, and a muzzle brake, you can get the vague effect you are searching for, but trying what you've desgined is going to be a problem.
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Unread postAuthor: MrCrowley » Fri Mar 09, 2007 4:51 am

Or make something similar to pimp's(Pimpmann22) recoil stock:
Image

For full details:
http://www.spudfiles.com/forums/viewtopic.php?t=745&
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Unread postAuthor: joannaardway » Fri Mar 09, 2007 4:58 am

That still won't reduce recoil. It'll just spread the "force" over a longer time.
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Unread postAuthor: MrCrowley » Fri Mar 09, 2007 5:02 am

But the recoil shouldn't be as bad on the shoulders as the springs will absorb some of the 'force'. Yes there will still be recoil but it will be softer. Well pimpmann claims it works anyway.

I see what you mean now...you know more then me but it seems thats the basic concept behind it unless the springs do what you say and just spread the force out over a longer time period making it seem softer and not such a quick hard blow
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Unread postAuthor: Hotwired » Fri Mar 09, 2007 5:26 am

Recoilless anythings have to shove something out the back with equal force to the projectile leaving the front. Otherwise it will have recoil.

By shove I mean whatever is counteracting the recoil has to completely leave the cannon.

I know of two recoiless systems (I don't include rocket launchers): One directs part of the blast of a shell backwards through a venturi nozzle to produce a conteracting force and the other is literally two cannons back to back and when fired at once have zero recoil. (one fires a shell, the other fired grease and lead equivalent to the weight of the shell).

You're not actually doing that here, you're weakening the force behind the projectile but you're also trapping the counterweight so when it hits the end you will get the recoil albeit dampened by the spring and travel of the counterweight. You might as well put external spring dampening on and leave the projectile at full power.

Recoiless anythings always lose power, the first way with gases means the projectile doesn't go as far and the second means you're having to have a rather bulky double cannon and use twice the energy.
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Unread postAuthor: joannaardway » Fri Mar 09, 2007 7:07 am

Spring damping won't change the amount of recoil significantly*- it'll only change how "hard" it is.

*It will actually increase it slightly, because the cannon can move more freely, more energy is transferred to the cannon when you fire. This also reduces the energy of the projectile as well.
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Unread postAuthor: iknowmy3tables » Fri Mar 09, 2007 8:40 am

it takes away energy have you ever seen shells for recoilless rifles (their more like canon artillery) the gun is way lighter than non-recoilless counter part canons, making them usable for infantry, but the shells are friggen huge to create enough energy set the blast in two directions. Simply their is too much wasted energy,
And did you think about what would happen when the counter weight hit the bumper after gaining momentum, the impact will create a delayed but huge recoil, so this is will probably produce erratic changes in recoil
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Unread postAuthor: Matheusilla » Fri Mar 09, 2007 11:15 am

IF I were to make a recoilless canon like F-H's idea, I would do it backwards. I would use the counterweight as a hammer for a firing pin. I would make it so that the counterweight fires forward instead and hits a firing pin somewhere before the end of it's travel. It would reduce the recoil a bit I'm sure (it would also have a funny type of recoil, forward then backward).
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Unread postAuthor: Hotwired » Fri Mar 09, 2007 11:49 am

I'd not be too happy about putting a cannon under shock tension if it has the kind of force needing a recoiless system.

I'd rather not bother and would just keep the force down to manageable levels or have it ground based.

It isn't worthwhile to make a recoiless system for a cannon.

They're designed for firing large shells without needing a bloody great tank or field gun and to do that they reduce the range and power. Its not feasable to waste that much energy with a pneumatic system.
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Unread postAuthor: Matheusilla » Fri Mar 09, 2007 12:30 pm

I once built a combustion canon that was about 2 foot long and 3 inch dia. One of the first things that I fired outta it was a 1 liter plastic bottle filled with water. The recoil almost knocked me on my a$$! I wouldn't say recoilless is useless, some people (me) like a bit of recoil.
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Unread postAuthor: CS » Fri Mar 09, 2007 12:41 pm

For clarification purposes:

Yes, the pictured 'recoil system' works, but the cannon did not generate near the power necessary to compress the springs. It was more or less for aesthetic purposes, although I had hoped that it would have functioned a bit better.

I hope one day to return to the design, and work with it in portraying a more accurate in appearance 'rifle'. There is a issue with having the two though. It will require that the force put on the 'slip repair coupling' to be considerably proportional to the other. As when the movement starts to strife from the original axis of travel the previously free flowing movement becomes 'choppy' as non-lubed PVC surfaces rub.
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Unread postAuthor: Brian the brain » Fri Mar 09, 2007 2:32 pm

Chappy nearly dislocated my knee at 9 bar with a 1300 gram projectile.
I would have fallen sideways ( because of the way I held it) but my brother caught me..It kinda shocked us both.
I had placed the 90 bend on my leg for support...The kick was so bad I don't feel like ever trying it again..It did however disintegrate the cinderblock I shot...

Recoilless sounds sane to me...
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