So i'm hooked!!!

[Jax]

Went out for the first time to shoot cannons and yep, im gonna need more   

  I even shot the Brass one that I have and it shot like a champ!  I know many thought it was too thin to shoot, but I had no issues. 
The smart guy that I am I forgot to use wad with the first shot, so it was less than impressive.  I didnt go above 200 gr with that one and it still put out a nice bang.  My father in law had a 1 in bore brass cannon there as well and we got up to 350gr with that one and that was very impressive!  I just cant wait to get a golf ball cannon and shoot some balls.  I did make a video with my camera, BUT I cant seem to load it on anything except my laptop...  I did a freeze frame on the blast point, but thats giving me trouble too

[RocklockI]

Yea the first ones free ....  after that you gotta pay .  same ol story ......WELCOME TO THE CLUB !

[Asron87]

I'm not going to lie, I'm new to the sport too and I'm hooked as well. I got my first cannon about a month ago and I'm hooked. The other day I was talking about my next cannon, they replied "you already have a cannon". I commented "Well, it's only my first cannon." He just laughed. My next cannon will be a golf ball cannon and I can't wait, after that I plan on making my own 1/2 scale cannon.  

On another note, don't push the limits of your cannon. Know what you can and can not do before you do it. Be safe and have fun.

Hopes & dreams,
Aaron

[Double D]

Yep you are hooked now!!! Great!

Time to move beyond smoke and noise.  Go to the Safe loads sticky at the top of the forum and you will find guidelines and for developing loads for projectiles including a chart for guns smaller than 2 inches.  

I even shot the Brass one that I have and it shot like a champ!  I know many thought it was too thin to shoot, but I had no issues.  

And you may never have problems, and I wouldn't  expect problems from the first shot...where you using a projectile?  Any problems you have will subtle but progressive and probably sudden.  

I went back and looked at the original post on this gun.  I have some questions and the purpose of my question is to consider a means of salvaging what you have. I don't really think you are that far off.

The bore 1 1/16 inches.  What is the OD diameter of the barrel over the chamber just in front of the vent.

[Jax]

I shot it a total of 8 times.  started with 100gr.  With the amount of bp I used, it didnt even recoil that much.  Maybe an inch at most. 
   The Bore is 1  1/16 in all the way back.  The wall thickness is a lot greater at the powder chamber.  Its just shy of 1 inch thick all the way around the powder chamber.  And no I didnt shoot any thing but powder and wad.  I wont ever shoot a ball with this one. 

on a side note, I got the video to post on my facebook page, but it wont upload onto here.  I'll have to join youtube and try to upload there.

[Double D]

I shot it a total of 8 times.  started with 100gr.  With the amount of bp I used, it didnt even recoil that much.  Maybe an inch at most.  
   The Bore is 1  1/16 in all the way back.  The wall thickness is a lot greater at the powder chamber.  Its just shy of 1 inch thick all the way around the powder chamber.  And no I didnt shoot any thing but powder and wad.  I wont ever shoot a ball with this one.  

on a side note, I got the video to post on my facebook page, but it wont upload onto here.  I'll have to join youtube and try to upload there.

What is the outside diameter over the powder chamber?

If you don't have calipers to measure diameter use a soft tape measure ,even a piece of string and measure the circumference. We can get the dimaeter from that.

I really don't think you are that far out.

[Jax]

The powder chamber is 2 3/4 inches wide.  So its a little thinner than I thought.  I was going based on vision.  I poked a stick thru the fuse hole and when I saw it in the barrel id mark it and measure.  I got 15/16 when I did that. 
  But it seems like a heavy duty barrel. 

[JeffG]

WELCOME TO THE CLUB !

+1 on that, it's a great group here!!

[Double D]

Okay, now we are getting some where.

Barrel diameter 2.75/3 = .917 equals the safe wall thickness  from the guidelines.

Your barrel is 2.75 - 1.0625 =  1.6875 /2 = .84375.  minimum.

This also turns out to be a good example to show why Barlow's Formula should not be used with muzzle loading cannon.

To keep it simple, here is a link to a Barlow's Formula's Calculator.

http://www.aerocomfittings.com/barlows.html

Your barrel diameter is 2.75 inches.

We don't know what type of brass you gun is made from so I will just use the numbers for C360 brass.  Which as a yield strength of 45,000 PSI.

I don't know what the actual pressure of blackpowder in you gun would be but a number often referenced for black powder in cannons is 25000 psi.

Barlow's Formula Calculator
Barlow's Formula - An equation which calculates the relationship of internal pressure to allowable stress, nominal thickness and diameter of pipe.

The formula is: P = (2*S*t) / D, where:
P = internal pressure, psig
S = unit stress, psi
t = nominal wall thickness, in.
D = outside diameter of pipe, in.

P (internal pressure):  25000 psig
S (unit stress): 45000 psi.
t (nominal wall thickness): 0.7639 in.
D (outside diameter of pipe): 2.75 in.

This gives a thinner wall thickness than safety guidelines.  

Even though I missed the s factor in the Barlow formula, I knew it wasn't valid for this application, this proves it.
 

[gulfcoastblackpowder]

As I said in the other thread, all equations will give you the results they are meant to give, not including any factor of safety, which is something the designer is supposed to add.  Almost all designs are overbuilt.  Many are overbuilt by a large margin.  The lowest factor of safety you'll find is usually in racecars, which have some components designed with a FOS of around 1.2, meaning the particular part is only 1.2 times stronger than it has to be to not fail.  In that case, it's for weight savings.

Just because you input numbers and they don't give you the same results that a design rule of thumb gives doesn't mean it's invalid, but that you are calculating something different.  Barlow's formula, well suited or not to cannon type pressures, is only going to give you a minimum design requirement, unless you add some amount of FOS.

I agree that this particular cannon is not quite ideal.  The trunnions are especially undersize, and the bore is slightly oversize.  I wouldn't use this example as evidence that a tried and reliable formula is invalid - it's just not being used according to it's purpose.

[Double D]

The formula is not invalid. It is very valid.  

It's the application that is invalid.

It's perfectly valid in engineering environment where an understanding exists of the other factors involved.  

In an environment such as this where whe have a such a great diversity of knowledge it is to easy for a less knowledgeable person to grasp such  a tool to rationalize ignoring established safety guidelines.  

It to hazardous to assume every one here has an engineer's knowledge.

[gulfcoastblackpowder]

You're absolutely correct.  In fact, it's always bad to assume any knowledge on a subject when discussing it with an unknown audience (like an internet forum), and generally bad to assume knowledge even when discussing it with so called experts.   Assumptions lead to mistakes, and in dealing with cannons there's absolutely no room for mistakes.

[Victor3]

You're absolutely correct.  In fact, it's always bad to assume any knowledge on a subject when discussing it with an unknown audience (like an internet forum), and generally bad to assume knowledge even when discussing it with so called experts.   Assumptions lead to mistakes, and in dealing with cannons there's absolutely no room for mistakes.

 Along the lines of assumptions and no room for mistakes...

 To be of use to ensure reasonable safety when we apply the "one caliber rule," we must be positive that the material surrounding the chamber will be strong enough to repetedly and indefinitely withstand the highest BP pressures the barrel should ever see.

 It's interesting to me that many cast barrels I've seen discussed on this board that met the one caliber rule generally haven't raised an eyebrow if they appeared to be sound upon visual inspection (meaning an assumtion that the casting didn't have any hidden defects).

 None the less, multiple examples of cast iron and bronze barrels that met the one caliber rule have been shown to fail.

 Even with a liner (unless it's able to withstand maximum pressure by itself), why would any cast barrel be assumed to be safe unless voids or other hidden defects are ruled out by non-destructive testing?

[Double D]

 Along the lines of assumptions and no room for mistakes...

 To be of use to ensure reasonable safety when we apply the "one caliber rule," we must be positive that the material surrounding the chamber will be strong enough to repetedly and indefinitely withstand the highest BP pressures the barrel should ever see.

 It's interesting to me that many cast barrels I've seen discussed on this board that met the one caliber rule generally haven't raised an eyebrow if they appeared to be sound upon visual inspection (meaning an assumtion that the casting didn't have any hidden defects).

 None the less, multiple examples of cast iron and bronze barrels that met the one caliber rule have been shown to fail.

 Even with a liner (unless it's able to withstand maximum pressure by itself), why would any cast barrel be assumed to be safe unless voids or other hidden defects are ruled out by non-destructive testing?

Yes you bring up something that we all seem to forget, I know I do.  One of the element of the one caliber rule is the liner.  In order for for the one caliber rule to be valid you have to include the liner made to at least the minimum specs laid out in the N-SSA regulations.  Your barrel doesn't have to have a liner but may exceed the specs--the complete barrel is the liner.   Here is the wording-bore liner of extruded seamless steel tubing of a minimum ANSI standard and of a minimum 3/8-inch wall thickness.  At one time, I thought we had posted the ANSI standard for extruded tubing posted in the references section, but apparently we don't.

I got out my 1981 Pacific Machinery and  Tool Steel Co. reference manual  looked up seamless tubing; seamless not electro welded DOM.  They list  mechanical properties  for seamless in hot rolled, normalized, soft annealed, medium annealed, finished annealed and hard drawn.  The manual say the regular  grade carried in stock is finish annealed.  Finished annealed is listed at 75000 psi Tensile strength, 55000 psi yield and elongation of 20 % in 2 in.

Any one with better source, please post.

In comparison, everdur bronze  is 92000 psi tensile and 55000 psi yield with elongation of 22 % in 2 in.


 

[dan610324]

yes victor you are correct
its many of the cast barrels thats doubtful , especially the cast iron barrels
personaly I would never fire a cast iron barrel without a liner , ok if it was x-rayed and hold minimum 1,5 times the bore diameter in wall thickness
cast iron is very unforgiveable, when you get an catastrophic failure it shatter as a grenade
bronze is far more forgiving, it will most probably just crack along the axis of the bore

what cast bronze barrel are you thinking about ??

[oyvind]

Hello,
My personal opinion. It costs nothing to use a good steel, but the price to pay if you build too weak is very "high."

Oyvind

[Jax]

Barrel diameter 2.75/3 = .917 equals the safe wall thickness  from the guidelines.

Your barrel is 2.75 - 1.0625 =  1.6875 /2 = .84375.  minimum.

Thanks for all the good info.  Im trying to follow all the calculations here.  So if the safe thickness of my barrel is .917, BUT mine is only .84375, thats only a difference of .07325. That is just over a 1/16 of an inch.   Is that really that big of difference to make it unsafe?   Im not doubting you guys, but I know what im looking at, and its just seems that this barrel is thick and safe. 

[dan610324]

if it is 2.75" outer diameter the largest safe bore diameter should be .917"

[Cat Whisperer]

Jax -

Facts are your tube doesn't fit the rule.
OK, so now it's guess work as to what the maximum safe load should be.  Just that, guesswork.

SO, start with the max load for that diameter (ID and the should-be OD) -- you know that's too much.  How much too much?  Again guesswork.

The choices are now - reinforce what you have or .....

[RocklockI]

Isn't this a salute only type gun ?

[dan610324]

even blanks are known to blow up cannons

[Double D]

No, don't dumb down loads for noise, put barrel liner in it.   

[Victor3]

 Along the lines of assumptions and no room for mistakes...

 To be of use to ensure reasonable safety when we apply the "one caliber rule," we must be positive that the material surrounding the chamber will be strong enough to repetedly and indefinitely withstand the highest BP pressures the barrel should ever see.

 It's interesting to me that many cast barrels I've seen discussed on this board that met the one caliber rule generally haven't raised an eyebrow if they appeared to be sound upon visual inspection (meaning an assumtion that the casting didn't have any hidden defects).

 None the less, multiple examples of cast iron and bronze barrels that met the one caliber rule have been shown to fail.

 Even with a liner (unless it's able to withstand maximum pressure by itself), why would any cast barrel be assumed to be safe unless voids or other hidden defects are ruled out by non-destructive testing?

Yes you bring up something that we all seem to forget, I know I do.  One of the element of the one caliber rule is the liner.  In order for for the one caliber rule to be valid you have to include the liner made to at least the minimum specs laid out in the N-SSA regulations.  Your barrel doesn't have to have a liner but may exceed the specs--the complete barrel is the liner.   Here is the wording-bore liner of extruded seamless steel tubing of a minimum ANSI standard and of a minimum 3/8-inch wall thickness.  At one time, I thought we had posted the ANSI standard for extruded tubing posted in the references section, but apparently we don't.

I got out my 1981 Pacific Machinery and  Tool Steel Co. reference manual  looked up seamless tubing; seamless not electro welded DOM.  They list  mechanical properties  for seamless in hot rolled, normalized, soft annealed, medium annealed, finished annealed and hard drawn.  The manual say the regular  grade carried in stock is finish annealed.  Finished annealed is listed at 75000 psi Tensile strength, 55000 psi yield and elongation of 20 % in 2 in.

Any one with better source, please post.

In comparison, everdur bronze  is 92000 psi tensile and 55000 psi yield with elongation of 22 % in 2 in.

 Let's run the numbers (Barlow's formula) using your tubing's tensile spec for what the N-SSA would consider an acceptable liner for the 12# Napoleon...

 The 3/8" wall liner OD would be 5.37". With a 75 ksi tensile, I get 10,475 psi. So less than 50% of what we assume might be an internal pressure of 25 ksi.

 Is that really a safe liner, installed in an only visually inspected cast iron barrel, considering that they allow 20oz of powder and a 192oz projectile? I guess it must be since that's what's on their chart.

 The N-SSA rules give no indication of what type of steel should be used. It could be assumed (from their wording) to be any type as long as it's "extruded seamless steel tubing of a minimum ANSI standard and of a minimum 3/8-inch wall thickness." What "minimum ANSI standard" are we talking about here? They're hardly the same for all types of seamless steel tubing.

 Also, their breech plug specs are nebulous; "sweat-fitted into the liner and welded." We of course assume that to mean shrink-fitted, but no indication is given as to either the interference fit tolerances nor what manner of welding should be employed. They require pictures of before and after welding (only on barrels manufactured after 3/1/86 though), but pictures show next to nothing as far as the soundness of a shrink fit or weld. They say that the plug must be a minimum of 1" thick, but we know that the force applied to a 4" diameter plug is far greater than that of a 2" plug at the same internal pressure.

 They don't even require a liner or the "one caliber rule" on original CW era barrels (probably more subject to failure than most modern-made guns) or reproductions approved prior to 3/1/86 unless they fail some "inspection" which isn't defined in the text. Is it done by a guy with a flashlight or are more sophisticated methods employed?

 Although their record of safety speaks for itself, I'm not all that impressed with the N-SSA's wording on how to construct a uniformly safe liner/barrel.

[Double D]

Have you consider posting this on the N-SSA board.

You have one number wrong.  The wall thickness of a Napoleon chamber  is not 3/8 inch.  

On the other hand the wall thickness of a Napoleon chamber is not one caliber either.

Absent any better guidelines, I will stick with N-SSA guidelines.   It's an individuals choice what guidelines to use.  

FWIW using Barlows to determine what steel you need to make a 12 PDR cannon with 3/8 walls you need something with 175000 PSI tensile strength.

OTOH, using Barlow the material need to construct a Napoleon barrel only needs a tensile strength of 21552 PSI.

 

[dan610324]

what bronze barrel ??

[GGaskill]

Cast iron is not without tensile strength (25,000 psi per Wikipedia.)  But its elongation is very low (0.5%) which means it fails almost immediately when its tensile strength is exceeded 

If you want the liner to carry the entire load, a 3/8" liner is adequate in a small bore gun (say 1" and less) but is well less than prudent for even a 6 pounder (3.62" bore.)  South Bend Replicas used thicker liners in larger bore guns (I can't find my SBR catalog which has the numbers in it) in response to this fact.  I can only believe that most lined cast iron guns with 3/8" liners aren't fired much or are used mostly for salutes.

Frankly, Barlow's formula is stated to be useful for finding bursting pressures for pipe, which is only partially relevant to what we a looking for in cannon barrel design.  We aren't looking for the thickness that the tube will burst at, but a thickness where the material stresses are within a range that we consider safe.  This safe state must include all the known sources of failure, especially what is commonly called "fatigue" failure. 

There are curves that relate internal stress and repetitions for most metals; for steel, the stress needs to be about 20% of ultimate to have unlimited fatigue life.  Now we don't really need unlimited fatigue life (unlimited is considered to be above 10 million repetitions) in cannon barrels.  Take a look at high power rifle barrels; since they typically wear out before 10 thousand repetitions, it makes no sense to give them an unlimited fatigue life.  Take a look at modern artillery barrels.  They are replaced at about 5,000 rounds, and less if they have been fired with mostly full power loads.

I can't speak to the N-SSA standard and its provenance.  My guess is they are satisfied with it based on experience (no KaBooms) but it is not satisfying to me.  But I don't make cast iron barrels.

[VA Rifleman]

Jax,

  If it will help your decision making. I'm talking with a supplier linked to this site. His barrels are made from good 1144 steel but the one I am looking at  is lacking .18" of material at the powder chamber to meet the 1 caliber rule. So in negotiation to see if he can turn a different profile that meets the 1 caliber rule. If he can't make it, I won't buy.  Brass is a marginal material for cannon barrels. No brass muzzle loaders out there for example and the few times brass was used for frames in smaller arms such as in the Henry repeating rifles and in some single action revolvers, it was quickly replaced with better material.  A better example was the transition from brass to bronze way back when.  

This is a great site and all these guys want to help you with your safety foremost. Sort of like the priorities when I go deer hunting. 1, don't shoot anyone, 2, don't fall out of the tree 3, don't wreck the truck. 4. shoot big deer

Edit was to fix poor spelling

[Double D]

Sort of like the priorities when I go deer hunting. 1, don't shoot anyone, 2, don't fall out of the tree 3, don't wreck the truck. 4. shoot big deer

That's why I like my part of Montana, no trees to fall out or or block my cannon balls.

[RocklockI]

ol Mike H from Gunsmith school was from arizona with a jeep comando . This was a machine of the desert , the thing barley got warm in the summer here in Co . in the winter ,,,,,you froze .

Anyway he was famous for saying "The trees just block the veiw"

No trees to block a shot in Arizona either ! Cannons !

[Victor3]

You have one number wrong.  The wall thickness of a Napoleon chamber  is not 3/8 inch.  

 No, the 3/8" is for the N-SSA specified liner wall thickness. Nothing to do with the chamber...