I'm a newbie who wants to make a beer can cannon!

[frankgg]

Hello everyone!

I'll start off by saying I'm a newbie here and to the cannon world.  My day job is a mechanical engineer, so I do have some background in design, but I'm only 5 years out of college and haven't really been working on anything that can be related to cannon making, but I'd love to learn.

So I've seen a lot of beer can mortars, but have yet to see a beer can cannon, is there a reason for this?

I've been thinking I would like to make it about 24" or so long, 2.65" ID/Bore (for concrete-filled beer cans), maybe 4.5" or 5" OD?  I'm not sure what internal pressures it would see so I can calculate if that's a thick enough wall or not. 

I can make a model & drawing in SolidWorks once I figure out the specifics...

If anyone wiser than I would like to help me, I guess my basic questions are:

1.  The FAQ says not to go over 3 oz. FFA per inch of bore diameter, so I'd be sizing my Powder chamber for max about 7.5 oz. of FFA?  Too much or too little?  Anyone know what oz. of FFA translates into volume (like 1.5" Dia x 1.5" deep)?

2. I've seen a few references to 4000 series steel, is that what people are using?  Is it safe to start with a seamless tube or should I be making this out of full round?

3. Does anyone know what type of internal pressures I'd see or any reference available to calculate it?  I can run some FEA at work to make short work of the pressure calcs.

I'm sure I'll have some more questions, but for now, thanks everyone and I'm excited to have found this forum!

[Double D]

You can engineer it all you want or you can make a cannon.  The engineering has been done already, so no need to reinvent the wheel

First I suggest you visit our sticky at the top of of the forum called  Safe loads and cannon plans. The is a link the to N-SSA Rules.  Read their safety rules for cannons and you will find all the information  you need to construct a safe gun.

First beer can cannons. Why bother.  At best a cement can mortar round is entertaining.  It is pretty neat to see the big can fly through the air, tumbling and flipping then the big whack when it hits. But where it hits is not consistent.  One of the first things I did was get a round ball mold for my beer can mortar and cast up some zinc round ball...I know pretty close to where the the round ball will land, a lot closer than the beer can.

A cannon for a beer can  will need to be at minimum, 7.95 inches at the breech.  That's pretty big for a 24 long inch bbl.  You could go smaller by making a howitzer.  But it still would have be pretty big.  Then you have the issue of bore, smooth bore and long beer can projectile don't go hand in hand.   The long projectile will have the tendency  to tumble and fly all over the place---satisfaction level will drop real fast.

Besides if you are going build a gun that big why not build the real deal

What I suggest you do is get a set of plans from Antique OrdnancePublisher  and build a gun for a known round object.  

If you have the skills you could also find the post here on the board about building a rifling machine and build a rifled barrel.  You can shoot long bolt like projectiles then.

If you still have the engineer in you burning to build, then I suggest an even better challenge.  Get a copy of John Muller's "A Treatise of Artillery 1780"  Muller discuss the design of a late 18th century artillery and expresses all dimensions as part of the caliber. For example, Muller says this:

General dimensions of brass guns
The caliber of the gun is divided into 16 equal parts.
The thickness of the of the metal at the base ring from the bore is 16 parts.
At the end of first reinforce ring 14.5 parts
At the same place, for the beginning of the second reincorce  13.5 parts
At the end of the second reinforce 12.5 parts
At the same place for the beginning of the chase 11.5 parts
At the end of the chase or muzzle, the moulding excluded 8 parts..

Lots of of discussion on barrel length, but Mullers preferred length was 21 calibers.

The length is divided in 7 parts.  
The length of the first reinforce is 2 parts.
the second reinforce is 1 part.
The chase is 4 parts

Using Muller your beer can bore gun would have to  55.65 inches long and 7.95 inches in diameter at the first reinforce or breech.  Muzzle diameter would be 3.975 inches.  The first reinforce would be 15.9 long, second reinforce 7.95 inches, and chase is 31.8 inches long.

I have plans to build a gun to Muller's design in the future..  His treatise also use the ratio system to build carriages for the gun.

[GGaskill]

The basic problem with designing a black powder muzzleloading cannon from first principles is that a critical factor in the design process is unknown, namely the chamber pressure.  I use 20,000 psi for a number when I am exploring designs but I have no documentable source for it.  You can make other assumptions or use figures from other sources but neither are really sufficient to make the calculations using them be completely satisfying.

The forum rule of thumb is chamber wall thickness equals bore diameter.  If you get some of the relevant AOP plans, you will find that some original guns meet that rule, and some fall short of it.  Generally, the cast iron guns are thicker than otherwise similar bronze guns. 

Assuming you would make your own gun from at least mild steel (1018, for example), you would be using a material superior to anything used during Civil War times (although the wrought iron rifle used a material similar to mild steel.)  This would give you a stronger than original design where the original design was considered adequate.

The reason you don't see beer can bore cannons is that they would be proportionately larger than something that would be 24" in length.  I have a beer can bore cannon under construction but it is 66" long and will be over 400 pounds when finished.  A mountain howitzer scaled to beer can bore would be about 21 3/8" long and 4.6" over the base ring (the largest diameter.) 

My large gun is seamless tubing but all my other smoothbore tubes were drilled from solid.  But that depends a lot on what machinery and tooling is available.

I think you should look at the various types of pieces available from AOP and get the appropriate plan folio and study that before cutting any metal.

[Ex 49'er]

frankgg   Welcome to the board. Sit down for a spell and absorb what these guys say.
There is a wealth of info here. I learn something new almost everyday.

[Double D]

George brings up a very interesting point, I would like to hear the answer to.  The N-SSA rules for the safe design of cannon state:

Actual or exact scale replicas of Civil War artillery pieces may be fired. The term “Civil War” applies to any artillery piece whose model antedates April 26, 1865. Replicas of artillery pieces must duplicate original pieces.

and

No reproduction barrel shall be approved after March 1, 1986, which does not have one caliber's thickness of metal surrounding the bore at the breech. (See figure 10.2 for example.)

I wonder how N-SSA deals with new reproduction exact replica of Napolean's.  They do not meet the one caliber rule.

This one caliber wall thickness rule serves as a  safety quide line here on this board.  Absent any other credible source we have relied on the experience and knowledge of the N-SSA as our source.  Until some other more credible source is found, N-SSA will continue to be the authority we point to.

At last summers Montana Cannons shoot braai, this issue of wall safety was discussed.  At this gathering were at least 5 accredited gunsmiths, a farmer, and Mike RC....sorry Mike, I'm not sure, beyond a pretty face and heck of a cannonmaker what your credentials are.

We discussed that modern smokeless powder cartridge firearms have much thinner walls and are rated at much higher chamber pressures. The discussion covered a realm of items.  Total pressures based on the total volume of the chamber, type of steels etc were discussed.  It was the consensus that because of the vast difference in skill and knowledge that on the board we would continue to recommend the N-SSA one caliber wall thickness rule.

Frank asked about the 4000 class steels, I think what he means is the medium carbon alloy 414-4150 classes referred to as ordnance steel. This is some strong steel that machines fairly well, works well with mechanical joining; threading, pinning, pressing etc. Medium carbon steels require special welding techniques such as controlled preheating to avoid hardening and brittlement in the weld area. 

Mild steel like 1018 is much easier to work with in the hobby environment, especially in the area of welding and still retains sufficient strength for use in black powder guns.

Powder.  Start with Cannon grade powder.  Leave the FFa for advance skills, you really don't need it.  You will find Cannon grade easier to find than FFa anyway. The only advantage I have seen FFa has over Cannon grade is price.

Pressures are known for cannons and discussed from time to in The Artilleryman magazine and in Switlik's book, The More Complete Cannoneer.  Switlik did actual pressure testing and has some interesting information to share. 

I am going too do some pressure gun work this summer with some black powder cartridge rifles.  I may run some cannon test also.  It will be for small model cannons, so I am not sure the the relevance to larger guns.   If you do any pressure tests on FFa, we sure would like too see the results, especially comparisons with Cannon, Fg and FFg.

[dan610324]

please explain what FFa is

[Double D]

Dan it is a fireworks powder.  http://powderinc.com/blackpowder.htm

[dan610324]

ok

[Cat Whisperer]

frankgg  -

WELCOME to the board.

In addition to the responses thus far, let me toss out that you need look at not just tensile strength but the repetitive hammering of firing - so look at the Charpy notch test.  Mild steel (1018 and others) works fine!  In the 1870's or so it revolutionized cannon making (from cast to steel).  It still works VERY well.

Cannon eh?

7 oz of powder will put quite a buzz on a beer can full of concrete!

What do you have lined up for a range where in to launch these guys?