For those who like potato guns

[InigoMontoya]

I've been working on a project for a number of years now. It's *almost* completed. In short, I believe it will be the world's most powerful gun powered by "hardware store-level technology". Not the largest, mind you, but the most powerful. Muzzle energy should be in excess of 2 MJ.

 

In any event, it's a fun project that I figured folks around here might get a chuckle out of. Below is a pic. It's a bit dated; lots has happened since the pic was taken, but it should give you an idea....

 

[vordhosbn]

Wow, looks nice. What kind of projectiles do you fire with? And what kind of distance have you achieved?

[InigoMontoya]

It hasn't been fired yet (as I said, it's *almost* finished). The projectiles are actually intended to be aircraft flight data recorders ("black boxes"). Distances will basically be point blank as the goal isn't distance, but rather to study impact dynamics.

Edited February 27, 2010 by InigoMontoya

[Cap'n Refsmmat]

What kind of "hardware store-level technology"? I've been down to the Southwest Research Institute's air-cannon facility and seen some neat air cannons, but this looks to dwarf them.

[Mr Skeptic]

Years of research and development?

[InigoMontoya]

By "hardware store tech" what I mean is off the shelf parts that are recognizable to virtually anybody. The barrel is sch 40 pipe (not some custom honed, heavy walled gizmo that would cost a mint by itself alone). The ignition system is based on that of an automobile (MSD ignition!). Blah blah blah. There is nothing high tech. Everything about it could be done in the average garage by a teenager were it not for the simple scale of it.

 

 

And yes, it's taken me years to put it all together. I'm afraid that attacking that particular goal isn't exactly a paying gig. I had to beg/borrow/steal to get the parts and services required (ex: I'm not a welder who's capable of doing pressure vessels... Suffice to say it took many favors to get the services of one who was). It's mostly made out of stuff pulled off of scrap piles. So.... While a dedicated team could likely build it in a matter of weeks? Yeah, it's taken me years to pull it off (first came up with the idea in Aug 2002).

Edited February 27, 2010 by InigoMontoya

[Mr Skeptic]

Ah, I see. Just out of curiosity, how long is the barrel? Your picture would be more impressive with a human around for comparison. That chair in the background is about the only thing that I know the size of.

[InigoMontoya]

Barrel is 19" bore, 40' long.

[Cap'n Refsmmat]

When you say "ignition system," I assume that means this isn't a simple compressed air cannon. What sort of propellant will you be using?

[SH3RL0CK]

... The barrel is sch 40 pipe (not some custom honed, heavy walled gizmo that would cost a mint by itself alone). The ignition system is ...

 

I assume you have done the math regarding the expected pressure that this refinery piping will see due to the internal explosion? And that you have compared this pressure with the ratings for "schedule 40" piping?

Do you have any prototype pressure and hydrostatic testing?

 

I wouldn't mind seeing these calculations and/or since I am a bit skeptical that your "schedule 40" piping will sufficiently contain the potential explosion. Which of course, could result in the rupture of the piping and the potential for property damage or even loss of life.

 

Especially considering you stated

 

. It's mostly made out of stuff pulled off of scrap piles.

 

People generally do not throw away quality stuff, making the aforementioned pressure and hydrostatic tests pretty important.

 

After all, playing with fire (or explosions) is fun only until someone gets hurt.

[InigoMontoya]

When you say "ignition system," I assume that means this isn't a simple compressed air cannon. What sort of propellant will you be using?

Propane and air.

 

I assume you have done the math regarding the expected pressure that this refinery piping will see due to the internal explosion? And that you have compared this pressure with the ratings for "schedule 40" piping?

Yes.

 

A quick back of the envelope thin-wall pressure vessel approximation? Yield = 36000 psi = Pressure * 19" / (2*0.5) => Pressure = 1895 psi. Not that I have any intention of running it anywhere near that. And yes, I've run much more detailed numbers but I'm not gonna dig those up for this thread.

Do you have any prototype pressure and hydrostatic testing?

Yes. By controlling precise fuel/air mixture and pre-combustion pressure, post-combustion pressure is pretty easy to control. Plan is to run the gun at 200ish psi. Gun has been hydrostatically tested to 325 psi.

 

People generally do not throw away quality stuff, making the aforementioned pressure and hydrostatic tests pretty important.

I have access to some pretty high quality scrap piles and there isn't a piece in there that I don't know of it's "former life." The problem isn't the quality, but rather, sitting on the sidelines watching/waiting for that [whatever] that I need. Example: The trailer. It took 6 years to get that trailer, but it is a beauty....

 

 

(And for what it's worth, my day job entails playing with much more dangerous toys than this one. I'm well versed in safety protocols and such for energetic systems.)

Edited February 27, 2010 by InigoMontoya

[InigoMontoya]

Ah, I see. Just out of curiosity, how long is the barrel? Your picture would be more impressive with a human around for comparison. That chair in the background is about the only thing that I know the size of.

 

 

I'm giving a presentation on the gun at a conference in a couple weeks so I had some pics taken. I believe they'll answer the question of scale a bit better (and let it never be said that I don't have a sense of humor)....

 

 

Edited December 20, 2010 by InigoMontoya

[Mr Skeptic]

Well I can see its far bigger than I thought. You're really going to have a problem when you try to holster that one.

[InigoMontoya]

Well I can see its far bigger than I thought. You're really going to have a problem when you try to holster that one.

 

That's what she said?

[Newbies_Kid]

whoa... please share the picture when this cannon is 100% finished.. it's really cool

[Cap'n Refsmmat]

What will the target be? I can't imagine flight data recorders surviving launch from that and impact with a very solid target.

[InigoMontoya]

What will the target be? I can't imagine flight data recorders surviving launch from that and impact with a very solid target.

Whatever the customer would like it to be.... Sand. Gravel. Granite ( ). Various types of soil.

[lazygamer]

wow, I got really suprised and excited when I saw the chair in the background XD I thought it was like a normal small car-trailer, not a freakin semi-trailer trailer XD

 

go forth! ^^ and you should definetly do some distance-shooting with it

[chilehed]

Impressive.

 

The big pumpkin guns have muzzle energies of about 1.5 MJ: 10" bore, 3000 psi air, and a 10 lb projectile at 600 MPH muzzle velocity. I've seen one of them shoot a large (like about 12" or more diameter) branch clean off of an oak tree at about 100 yards.

[InigoMontoya]

The big pumpkin guns have muzzle energies of about 1.5 MJ: 10" bore, 3000 psi air, and a 10 lb projectile at 600 MPH muzzle velocity. I've seen one of them shoot a large (like about 12" or more diameter) branch clean off of an oak tree at about 100 yards.

For comparison, my design goal is 100 lbs to 1000 fps (680 mph).

 

 

edit... Something's not right here. 1.5 MJ compared to "2+" MJ for a significantly smaller projectile that's slower as well?

 

PUMPKIN

10 lbs = 4.545 kg.

600 mph = 268.2 m/s

Energy = 0.5 * 4.545 * 268.2^2 = 196 kJ

 

Mine

100 lbs = 45.45 kg.

1000 fps = 304.8 m/s

Energy = 0.5 * 45.45 * 304.8^2 = 2.11 MJ

Edited April 7, 2010 by InigoMontoya

[InigoMontoya]

Haven't had a chance to fire the big gun yet. Won't for a long time unfortunately, as we're booked SOLID at the office and it's a "spare time" project.

 

However, in the name of potato guns, I did have some fun a couple weeks back. At the office we were performing some tests that required the use of a high speed camera and finished up an hour before quitting time. I asked the photographer if he could pan left and take a quick video. And he did.

 

http://www.youtube.com/watch?v=YZdhDNHj1dM

 

 

(And yes, I'd anticipated finishing a bit early and planned ahead...)

[Cap'n Refsmmat]

Awesome. I'm envious of any job that involves making man-portable potato cannons and trailer-mobile potato artillery.

 

Also, I'm surprised that golf ball appeared to emerge unscathed. At that velocity I'd have thought it'd break when it hit the ground. I guess the shallow angle let it survive.

[InigoMontoya]

Awesome. I'm envious of any job that involves making man-portable potato cannons and trailer-mobile potato artillery.

 

LOL... No, my job doesn't involve the making of potato guns. That's just my hobby. My job is the testing of energetic systems of various flavors (yes, including various guns...but generally not potato guns). Thus, the need for high speed photography. I just realized that we were likely to finish that test series early that day and brought in one of my creations for some fun just before quitting time.

 

On that note, an amusing (but true) story.... Those I work with are well aware of my hobby and are always asking/laughing about whatever my latest creation is. The big yellow gun (Vera) that this thread centers on actually started as a joke.... I did most of the design on my own time and pitched the project to managment just to see the look on their faces. I had no expectation that it would get approved. I gave my pitch. Management approved it. I was like, "I'm almost disappointed. The only reason I pitched that was to see the look on your face. I never dreamed you'd approve it." The response was, "Well, I would have laughed but two weeks ago I had a customer ask if we could do the exact type of testing you just pitched."

[InigoMontoya]

Things have been progressing as we've had a "slow period" at the office. Unfortunately, said slow period is over and I'm about to get slammed with a crapload of work, but in the meantime we finished our first test projectile. No, it's not a recorder, it's just a glorified chunk of metal to push out the muzzle to prove that the gun works. And yes, a sabot will be involved before we're done.

 

[Pic removed for space....we've all had time to view it and it annoys me that it takes so much space]

Edited November 18, 2010 by InigoMontoya

[Mr Skeptic]

That looks like it could do some damage! Send us pics of the crater when you make one