Newbie with come questions regarding a pressure cylinder

[brohan76]

Hello everyone.  Thank you for taking the time to look at this post, any info would be greatly appreciated.

A few years ago on the 4th of July a neighbor of mine was using a cannon that he had made.  It looked quite nice, and was adequately loud.  We got to talking and he told me he had made it out of a small compressed gas cylinder (stubby welding cylinder), some schedule 80 steel tubing, and some plate (As well as oak for the holder).  As luck would have it I came across a stubby cylinder like he had.  I also have access to some 2.25 OD x 1.125 ID seamless steel tubing.  I would like to make a similiar cannon to his. Unfortunately he has since moved out of the neighborhood and I have no other info than what I have mentioned here.  What is the best way to go about making a cannon from these materials? 

My best guess is to thread one end of the steel tubing in order to cap it, then of course, make a cap for it.  My brother-in-law is a professional welder so I am considering having him weld the cap in place as well.  To mount the inner tube into the cylinder I thought I would make 2 round "doughnuts" from .25" steel plate.  I would first weld the first disk towards the bottom OD of the inner tube, then place the tube into the cylinder so the cap is touching the back (threaded end that held the valve), then weld the OD of the "doughnut" to the inside of the cylinder.  The 2nd "doughnut" would be put in in similiar fashion, but to cap off the cannon.  I would like to use a striker to ignit the cannon instead of a fuse so that 1.) I can use a long lanyard to keep myself away from the fire and 2.) a striker goes off instantly, reducing the risk of someone walking in front of a lit cannon.  How do I get the fire from the striker to the inner tube?  My thought is to drill a hole through the tube and the outter cylinder and connect the two with  another welded tube, making the vent, which will have the striker on top of it.  Is this the way to go about this project or am I way out of line?

I am going to use this cannon only for its noise and smoke factor, it isn't intended in any way to launch a projectile.

Brian

[GGaskill]

First, you should take a look at some real muzzle loading cannons.

Second, how about providing dimensions and a rough drawing of what you are proposing?

Third, regarding "I am going to use this cannon only for its noise and smoke factor, it isn't intended in any way to launch a projectile," how are you going to guarantee that this is true?  While you may never fire a shot from the gun, what about someone else?  What about when it finally leaves your hands?  I consider it bad practice to design cannon on the premise they will never be used to fire projectiles as this condition cannot be guaranteed and it instantly becomes a dangerous situation if used with shot.

It is better practice to plug the tube versus capping it.  A cap will have much greater force on it than a plug.

Do you have machining experience and/or facilities?

[brohan76]

Thank you very much for your reply.

I will make a drawing with some dimensions and post it on here, hopefully tonight.

Fortunately I am a machinist by trade with over 10 years experience with steel, aluminium and plastic.

[Michael Az]

I am also new to this cannon building. As you are a machinist, I am going to suggest finding a print on this site and go with that. I think it is maybe better to build what has already been built and tested by many people at least until you get your feet wet. Oh, I have to believe that shooting a projectile has got to be a lot more fun than a blank!
Michael

[brohan76]

Does anyone have a good dxf to jpg converter so I can upload a drawing of the print?   The outter diameter of the cylinder is 7 inches with a .1875 wall.  The length of the cylinder is 12.5 inches then it has a full radius on the end with a port at the tip of the radius.  The tube I am tryin to use is 2.25 OD and 1.125 ID, I can make it any length, but it should be about 15.75 long to fit inside the cylider nicely

[Rickk]

From what you are describing, the pressure cylinder is just for show, and the seemless is doing all the work.

The vent hole may be a bit tricky to pull off.

[brohan76]

Exactly.  Sorry I didn't convey that. Basically the seamless steel tube is where the action will happen, the outer cylinder is for looks.  I also failed to mention that on the end of the outer cylinder in the existing port I will weld a trailer hitch to make it look somewhat more realistic, and to close that end of the outer cylinder.  My own real issue is getting the fire from the outter cylinder to the inner tube via some kind of vent

[Double D]

First if you are making a mortar, forget the trailer ball hitch, mortars didn't have balls on there cascabals.  Cannon barrels did.

George is dead on when he says design this to fire projectiles.  Dead is a good word, as just this past 4th of July there was a fatality reported from  a cannon "I am going to use this cannon only for its noise and smoke factor, it isn't intended in any way to launch a projectile".  Blank loads kill.

Here is a plan for a bowling ball mortar that was posted on the board here some time ago, made by a fellow down in Florida.

[Double D]

Here is the chamber detail



This mortar has a design flaw.



The Trunnion is to far back in the base and the gun tends to flip over backwards. I hop after teh ball leaves the barrel

[GGaskill]

The Trunnion is too far back in the base and the gun tends to flip over backwards.

Looks like you could turn it around in the mount and you would not have the flipping problem.

[GGaskill]

Does anyone have a good dxf to jpg converter so I can upload a drawing of the print?

If your CAD software can save/export as a bmp file or gif file, they would be better than a jpg.  If only a bmp, Paint can convert from bmp to gif.   A gif is smaller and is better resolution than a jpg.

[dougrunnels]

I am building bowling ball morter as we speak.  I found an O2 cyinder  that a bowling ball fits perfecly with the right amount of windage.  It measure about 29.5" in circumference unlike what I have read here in theses forums:ie 10.125" circumference.  I wasted an O2 cyinder that measured 10.125".  A bowlling ball just wont fit in it.  I was planning on using the "Florida Bowling Ball Morter"  plans to build this thing.  My Uncle, who owns a Tool & Die shop suggested using 1018 steel for the powder chamber, as it welds easier.  He has 4140 steel that I wanted initally but he caustioned againt it due to the welding problems.  Preheat and TIG welding is no problem to acounplish  (excuse my spelling) .  What do you guys think? 
dougrunnels@sbcglobal.net   if you want to respond directly!


Thanks

[GGaskill]

What's the wall thickness on your cylinder?