Idea for Recoless Cannon

Post questions and info about combustion (flammable vapor) powered launchers here. This includes discussion about fuels, ratios, ignition systems and anything else relevant to launchers powered by igniting things like hairspray or propane.

Postby That Guy » Thu Dec 07, 2006 8:27 pm

Hay guys,

I found your site recently, and after a bit of reading, came up with a new idea that is (as far as I know) new. A recoilless rifle (like those used in Vietnam, and today to clear avalanches on ski slopes), use a overgrown bullet with holes punched in the sides of the casing, and an open back to allow the propellant gasses to escape. This means that the energy of the projectile coming out of the barrel is balanced against the exhaust gasses, and you have a very large man portable gun with little or no recoil.
What got me thinking was all the talk of acetylene (very nasty stuff). I was reading some of the articles about people nearly blowing themselves up, thinking that it might be a suitable substitute for black powder in an old Napoleonic canon (civil war type cannons, the indestructible kind), when I got the idea for a recoilless potato cannon. If you made a barrel and expansion chamber out of steel (not cast iron pipe – shatter risk - , I mean mild steel that you have ARK Welded together for strength), and if you put a rear rocket nozzle type opening in the back, you might be able to eliminate both the explosion hazard, and the recoil hazard of a acetylene potato gun.

In more detail:
The idea would be to find an old empty gas cylinder in the 1500 to 3000 PSI range (these can be found at flea markets and estate auctions from time to time), cut a hole in each end with an acetylene torch, and then smooth out the wholes with a grinder. You now have a very sturdy mild steel expansion chamber. Next find a piece of mild steel tubing and weld it onto one end of the expansion chamber, when your done, stand in the middle of the barrel with the two ends supported on blocks. If it holds your weight when you jump up and down on it, your good to go. Now add another piece of pipe to the other end to divert the backblast away from the user (if you really want to go for it, machine a piece of steel into a rocket nozzle (look it up in a text book) and you will get even more recoil cancellation, and more thrust from your propellant. Finally, drill in three holes and thread them to accept the acetylene feed, the oxygen feed, and the compressed air feed (how many people have had detonations when they thought the gun was empty or when it wouldn’t light? Use the compressed air to blow out the chamber after a failed ignition). Make sure you have an on-off valve for all three gasses mounted on the launcher – if you just connected the acetylene hose and fired, the hose would probably explode as well (note acetylene will explode on its own if pressurized to more than about 10 – 15 PSI under normal conditions – even those tanks you have only go up to 250 PSI, and they do this by using a honeycomb of special metal that allows the gas to be compressed that much without igniting – treat acetylene with respect, this is nasty powerful and ornery stuff. Install your valves in each of the three holes to feed in gasses, and drill one final hole for the spark plug. Thread the hole and put in the plug, then wire it up to an ignition module torn out of an old junk yard car destine for the crusher (10, maybe $20?). Now you should be almost set to go. You have a chamber with barrel and open nozzle; the projectile will block the barrel, to block the rear nozzle during gas filling you need something that will seal in, but not be heavy or cause problems when it is blown out the back during firing: use a single paper cup (you will need one per shot so buy a pack at Wal-Mart). You should now have a very strong, and incredibly powerful launcher (kind of like a howitzer is a launcher) The first 5 firings, load, put in paper cup plug and gas, then get something very thick between you and the gun (think trench of dirt, concrete block wall or something else that would stop shrapnel) before firing (connecting the ignition coil inlet wires to a 12 volt car battery). The launcher is vented at two ends, and so even if you mess up and the projectile sticks, the thing should still be fine, all the gas blows out the back, but those first 5 times are just to make dam sure it works as you think it should. After the test faze, you can tripod mount this thing to something solid (the ones use by the ski patrol mount to trucks) and go have some fun. Happy blasting.
That Guy
 
Posts: 1
Joined: Thu Dec 07, 2006 7:47 pm
 

Postby Mr.Plow » Thu Dec 07, 2006 8:37 pm

Interesting idea.

I wonder how it would compare to a well designed muzzle brake. Would the amount of effort in your idea justify the extra expense? How much pressure loss would this modification entail, and what effect would that have on the projectile's muzzle velocity? Would there really be a noticeable increase in velocity over a similarly sized gun firing propane with a normal setup?

Frankly, because spudguns don't typically produce a very large recoil and are not accurate enough to really justify needing a recoiless setup, I'm not sure how effective this idea would be. I would, however, love to see someone make an accurate, smoothbore cannon firing fin-stabilized projectiles over long ranges.
Mr.Plow
 
Posts: 3932
Joined: Fri Aug 29, 2003 11:48 pm
Location: USA
 

Postby boilingleadbath » Thu Dec 07, 2006 9:33 pm

...I don't think we have enough propellent mass to make recoilless launchers of the usual sort, as is presented here.
I mean, a large launcher might have 7 grams of gas in it - and that's not terribly much to counter the recoil of any projectile worth countering the recoil of... it'd have to be expelled at mach 3 to counter even a 70g object at 300 fps - a situation which doesn't require recoil moderation anyway.

As such, I think it be best to augment the reaction mass by essentialy placing a second projectile in a second barrel - a non-consolidated object, of course, like a bag of water.
Such systems (in my estimations) shouldn't have trouble producing 60% of the preformance of a standard combustion launcher.

Just beware of the backblast - don't stand behind it, fire it within enclosed rooms, stuff like that...
boilingleadbath
 
Posts: 763
Joined: Mon Mar 14, 2005 5:22 pm
Location: USA
 

Postby SpudStuff » Thu Dec 07, 2006 10:45 pm

7 grams? I thought on mythbusters the differance between a empty football and one filled to 13.5PSI was like 12g or something? Most launchers have a much larger volume at a higher pressure.
SpudStuff
 
Posts: 789
Joined: Sun Nov 20, 2005 2:06 am
Location: USA
 

Sponsored

Sponsor
 
 

Postby boilingleadbath » Fri Dec 08, 2006 5:22 am

Spudstuff, we are talking combustions here - "higher pressure" doesn't make sence.
As it is, that [7 grams] the mass of a the fuel-air mix in a ~4.5 liter chamber... which is pretty big, although there have been hand-held launchers with as much as 30 grams. (maybe there's a bigger one... I don't remember)

(oh, and as the <i>designated drawer</i>, I provide you with <a href="http://img.photobucket.com/albums/v611/car2/TGrecoillesslauncher.png">this</a>)
From top to bottom:
gas cylinder
holes cut in ends
barrel, nozzle installed; acetelene, O2, and air inputs tapped; sparkplug added
Projectile inserted, fueled, and rear plugged with paper cup
Ignition: projectile goes out one end, gasses the other.

(and for comparison, <a href="http://img.photobucket.com/albums/v611/car2/recoiless_spudgun.png">here</a> is a picture of my concept)
boilingleadbath
 
Posts: 763
Joined: Mon Mar 14, 2005 5:22 pm
Location: USA
 

Postby Kenny_McCormic » Thu Dec 14, 2006 5:18 pm

im pretty sure those guns are really a rocket in a tube the spud fits in the barrel to tight the back plug thing would blow out and nothing more
Kenny_McCormic
 
Posts: 122
Joined: Sat May 13, 2006 4:22 pm
 

Postby Mr.Plow » Thu Dec 14, 2006 6:28 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Kenny_McCormic
[br]im pretty sure those guns are really a rocket in a tube the spud fits in the barrel to tight the back plug thing would blow out and nothing more
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
No, they're not rockets. Check out this wikipedia article:
http://en.wikipedia.org/wiki/Recoilless_rifle
Mr.Plow
 
Posts: 3932
Joined: Fri Aug 29, 2003 11:48 pm
Location: USA
 

Postby boilingleadbath » Fri Dec 15, 2006 12:30 pm

Yeah, kenny... you are thinking of the "bazooka".

(although I've learned that the idea of using a non-gas recoil mass isn't new... see "armbrust")
boilingleadbath
 
Posts: 763
Joined: Mon Mar 14, 2005 5:22 pm
Location: USA
 

Postby Kenny_McCormic » Sat Dec 16, 2006 4:48 pm

ok now i understand but i still think it would be easier to build a muzzle brake
Kenny_McCormic
 
Posts: 122
Joined: Sat May 13, 2006 4:22 pm
 

Postby Navigator7 » Sat Dec 16, 2006 5:55 pm

<blockquote id="quote"><font size="1" face="tahoma,verdana,arial" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Mr.Plow
[br]Interesting idea.
Frankly, because spudguns don't typically produce a very large recoil and are not accurate enough to really justify needing a recoiless setup, I'm not sure how effective this idea would be. I would, however, love to see someone make an accurate, smoothbore cannon firing fin-stabilized projectiles over long ranges.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">


Me too!

Anybody have any definitive thoughts on a length to width ratio for a stable projectile?

I'm thinking 7 to 1 and plenty of weight forward.
Navigator7
 
Posts: 2635
Joined: Sat Jul 17, 2004 12:00 pm
Location: USA
 
 

Return to Combustion Launchers

cron