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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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Unread postAuthor: boilingleadbath » Fri Mar 09, 2007 5:38 pm

Ah, the recoilless gun.
Comes up every now and then.

The design illustrated by the origional poster <i>may</i> decrease <i>felt</i> recoil - but it certainly won't decrease the total momentum.

Anyway, one might seriously consider the "double gun" idea.
There are a couple reasons for this:
1) It allows you to build a combustion without using any fittings - home made or store bought. Major cost/effort savings there for your large recoilless guns.
2) It's the most efficient of the systems that acctualy reduce the recoil.

Specificaly, I advocate... a section of pipe, open at both ends, with a combustion chamber in the middle, a heavy bag of water (or similar) in one end, and a lighter projectile in the other.
This system will eliminate almost all recoil without the need to pay close attention to any of the specifications.
It will generaly decrease muzzle energy (unless the counter weight mass is more than the effective launcher-firer mass)... but the energy loss isn't too bad in most reasonable cases, and certainly a small cost to pay to be able to use a 6" cannon firing 3 liter water bottles (which DR of spudtech has demonstrated to be basicaly impossible without a recoil system)

Cheap, fast, good.
Succeed where NASA can't.
(yes, it's not rocketry... but I'm aloud to make a joke, right?)
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Unread postAuthor: Hotwired » Fri Mar 09, 2007 5:46 pm

A double cannon's gonna be pretty dam big. I was actually meaning two separate cannons but a tube could still work :P

A tube cut in half with a Tee and a screw cap in the middle :)
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Unread postAuthor: From_Hamsterdam » Fri Mar 09, 2007 10:19 pm

i used recoilless in the context "recoils less"

i did mention it would loose power but that is why i am looking for larger fittings so i can build a bigger chamber.

joannaardway. if you fire a cannon forwards<the>, if you fire a cannon backwards>- the recoil is forwards<if> and forwards<at><- and will cancel each other out. So it will in theory have an effect. yes it dose loose power because some of that power is not used to move the ammo.

I wanted to decrease the recoil because i am launching it off my shoulder. it can help in accuracy because the barrel moves less before the projectile leaves the barrel, but accuracy is not a huge concern with big cannons.

if i remove the buffer for the counterweight i will have to increase the length of that pipe leaving we with a extremely large gun that loses half its energy. by stopping the counterweight i stop some of the air escaping and stop some energy loss. i did think about the counter weight hitting the stop and producing a recoil, but i could not do much about this besides a adding a spring. i did not want the counterweight leaving the gun for safety reasons.

Matheusilla. the second cannon me and a mate built had a 150mm(6inch) chamber and a 50mm barrel the second thing we fired was ammo made from a large fishing weight. I was holding the chamber with both hands he was using the BBQ liter, then BLAM it went flying out my hands hit the ground after bouncing off the edge of my car door about 1m away, lucky i wasn't resiting it on my leg or anything. We haven't used it since. Good times, good times...

LeadBath what do you mean "total momentum"?
I like your idea about the combustion cannon. Also using water as a counter weight is a good idea

i plan on modifying a cannon i already have by adding a T-secretion behind the barrel with a female thread attached so i can have the recoilless attachment or replace it with a plug.

thanks for your ideas/advice, i will try to answer every one.
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Unread postAuthor: boilingleadbath » Sat Mar 10, 2007 10:18 am

"won't decrease the total momentum"
Ok, that's not quite true, because it does decrease the muzzle velocity.
(I was refering to the net momentum that would have to be transfered to the shooter. This is always predicted by "inertia*velocity", no matter what internaly contained schemes you may come up with.)

The goal of keeping the cannon stationary during the firing cycle to increase accuracy is definatly a good idea... one which I have not considered. (I've been in the "consistent recoil" group for the most part.)
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Unread postAuthor: From_Hamsterdam » Sat Mar 17, 2007 8:26 pm

Sorry i have a lot of TAFE work to get done so i will have to postpone this cannon for a while. :cry:
p.s.
I will try to get a AutoCAD drawing of the design so it is easier to understand.
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Unread postAuthor: sjog » Sat Mar 17, 2007 9:26 pm

With shotguns a heavy gun is what you want to shoot when shooting lots of rounds, it's easier on the shoulder. But it's not the gun you want to carry around all day , it gets heavy. When you get a nice light gun it's great to carry but hurts with prolonged shooting.
So it's a toss up.
I know shooting my big spudder there is hardly any kick.It's heavy.
When real hunting I never feel the kick , just keep shooting till the deer is down.
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Unread postAuthor: boilingleadbath » Sat Mar 17, 2007 11:04 pm

Indeed, although that's not the concept we are discussing here.

V<sub>gun</sub>=M<sub>projectile</sub>V<sub>projectile</sub> / M<sub>gun</sub>
E = 1/2 MV<sup>2</sup>

So the recoil energy (that's the relevent measure) is equal to 1/2(M<sub>gun</sub>)(M<sub>projectile</sub>V<sub>projectile</sub>/M<sub>gun</sub>)<sup>2</sup> = 1/2(M<sub>projectile</sub>V<sub>projectile</sub>)<sup>2</sup>/M<sub>gun</sub>

Masses in kg, velocities in m/s, energies in J

...which essentialy means that the unpleasentness of the recoil is inversly porportional to gun mass. (a 1/x relationship)
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Unread postAuthor: From_Hamsterdam » Tue Mar 20, 2007 11:38 pm

I got it finished and there is minimal recoil it just kind of "jumps" when shooting. I only have a small chamber on it right now (50mm by 500mm) for a barrel that is 65mm by 1m, and i am shooting heavy bottels so it didn't have much power to start with. Now With the recoilless rig it has more then halved its range. it is way too long just over 1 1/2 meters but you can remove the recoilless bit.

i suggest only ading this if you build a huge cannon and are firing heavy projectiles.

These guys inspired me to build a recoilless cannon after hearing/seeing the amount of recoil big cannons packed.
http://www.youtube.com/watch?v=2Q7M337HSyk
http://www.spudfiles.com/forums/viewtopic.php?t=5389&
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Unread postAuthor: deusXmachina » Wed Mar 21, 2007 2:29 pm

If you were using combustion, you could just put the cannon in a tube that's larger than the largest fittings, so that the firing of the ammo is countered by the recoil of the cannon, except the cannon is free to move.

For large pneumatics, I think the best approach is a floating suspension system, one that allows the cannon to react to firing, without putting strain on the cannon itself. However, that defeats the purpose of shoulder-launched. Maybe you could make a tray which sits on your shoulder, the cannon sits on top of it free to move, and sections of surgical tubing secure the cannon when it kicks backward.
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Unread postAuthor: ShowNoMercy » Wed Mar 21, 2007 3:48 pm

When I had my first cannon, I filled the barrel up with water, I had been using an unmodded sprinkler vavle :oops: , and shot that off and damn that gun kicked back like no other. I had metal fittings to form the u bend and they cut up my hands and my leg/side of body. Needless to say I did that a few times more :P
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Unread postAuthor: From_Hamsterdam » Thu Mar 22, 2007 10:18 pm

i have fired it some more and the amount of recoil seems to vary.

I decided to see how much recoil it could stop so i loaded two bottles full of water, but i forgot to put the counter weight forward. I prepared for some recoil by tensing my shoulder, so when i fired i took the full recoil and pulled a muscle in my shoulder. :oops:

deusXmachina, i did think of this but not putting it on my shoulder. This can be used on large cannons but i don't like the idea of of having it on my shoulder. it just doest seem safe to me because the recoil would be wired. It would also put lots of strain on any hooks used to attach the springs/rubber because they would be fulled one way then the other. This could producing a a crack where the hooks are attached to the wood and could fail.

ShowNoMercy, you and boiling lead bath gave me an idea, instead of a counter weight fill it with water.

p.s. Are Spud Bux worth anything or are they like Browne Points?
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Unread postAuthor: Hotwired » Mon Mar 26, 2007 4:57 am

You can save them up for a signature or a custom title at the moment. After that they're not important.
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Unread postAuthor: joannaardway » Mon Mar 26, 2007 5:41 am

Unless you want to buy your own Sgort - only 20,000 SpudBux!
Perfect for general spudding advice!
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