1/10 scale 1779 - 24 pounder build

[Musketeer]

Even lining the barrel leaves a question of safety. The liner will swell on discharge. Sooner or later the outer skin may fracture and become dangerous shrapnel. Tick, tick, tick...

That's too bad. Such beautiful work.

 

[Paul Buchel]

Even lining the barrel leaves a question of safety. The liner will swell on discharge. Sooner or later the outer skin may fracture and become dangerous shrapnel. Tick, tick, tick...

That's too bad. Such beautiful work.

Thanks for all the compliments and information. I am however, very depressed. I am not new to firearm balistics, I have reloaded thousands of rounds for my P14 .45 and 9mm most of my life.

I will post more pics soon, when I get there.

Thanks again Paul.

 

No need to be depressed. As my Mother and Grandmother would have said, "This Too Shall Pass." And/or "Where there's life, there's hope." Besides, practice makes perfect.

If this is the worse that happens to you this year, count your blessings!

 

[Zonie]

When a childhood friend swallowed a marble that's just what his mother said.

"This too shall pass."

:rotf:

 

[Musketeer]

Look at the bright side, Paul. At least you came here and found this out. Had you not, you may have been out happily blasting away with it one day and BOOM! Razor sharp bits of bronze flying everywhere. :shocked2: You can also use what you learned making this one to help you out on the next one. An all around good learning experience. :thumbsup:

 

[Wes/Tex]

When a childhood friend swallowed a marble that's just what his mother said.

"This too shall pass."

:rotf:

Then, sometimes I feel like Congress...can't pass anything either! :shocked2:

 

[davec2]

Claypipe and Musketeer VB,

I have worked as a rocket propulsion engineer for the last 33 years and am often involved with highly stressed materials operating near their mechanical property limits. We do a fair amount of analysis during the design of rocket engine parts to make sure we know the limits of the materials and of the design before we proceed to manufacturing and testing very expensive hardware. I also work as a gunsmith and have followed this particular thread with some considerable interest.

I have noted your recommendation to Velocity that he spike the touch hole and never fire this beautiful model gun because it is made of PB1 alloy bronze rather than SAE 660. Can either, or both, of you answer a few specific questions for me?

1) What is the yield and ultimate strength of PB1 bronze and for 660 in psi?
2) What pressure, in psi, will be generated in a .44 caliber bore with 40 grains of black powder behind a .44 round ball?
3) Can you calculate for me both the thick and thin wall hoop stress in a .44 caliber barrel at the breech if the breech diameter is approximately 1.5 inches ?
4) Can you show, by calculation, how much permanent deformation (i.e. yield in inches) is expected at that pressure in the bore and what the increase in bore diameter will be for a barrel made of both alloys?
5) Can you explain why bore liners that are designed in themselves not to fail during firing would cause the outer jacket, of what then really amounts to decorative metal, to fail catastrophically?

I just want to be clear I understand why 660 would be OK but PB1 is not and your recommendation to Velocity that he scrap this model because of your certainty that it will eventually, but surely, fail in firing. I am assuming that your certainty that the gun will fail is based on something more substantial than personal conjecture. (i.e. Examples of similar PB1 cannon barrels that have actually failed? Stress calculations that show the actual working stress exceeds the yield and / or ultimate strength of the PB1 material? Or ?????

Thanks.

 

[F.G. Ford]

Great looking project.
Fred

 

[F.G. Ford]

Great job!
I have long experience in metal fatigue and I doubt very much that you will ever have any problems in shooting your fine cannon.
Others will disagree.
But I would assume your intentions are not to compete with a rail gun for velocities, and will shoot only black powder.
If you do decide to part with the gun, I would spike the touch hole and plug the barrel to prevent some idiot from using shotgun or pistol powder to shoot the gun.
With the thickness of your barrel at the breech, I doubt that 30-40 grains of 2f will ever cause problems.
When ever we make these toys, it is always a concern what some one will do with these items after we tire of them.
Many of us have seen replica cannons for sale on the net or at yard sales with no information, as to who or how they were made.
That is scary, and that well justifies the concerns of other posters here.
Fred

 

Claypipe and Musketeer VB,
I have worked as a rocket propulsion engineer for the last 33 years and am often involved with highly stressed materials operating near their mechanical property limits. We do a fair amount of analysis during the design of rocket engine parts to make sure we know the limits of the materials and of the design before we proceed to manufacturing and testing very expensive hardware. I also work as a gunsmith and have followed this particular thread with some considerable interest.

I have noted your recommendation to Velocity that he spike the touch hole and never fire this beautiful model gun because it is made of PB1 alloy bronze rather than SAE 660. Can either, or both, of you answer a few specific questions for me?

1) What is the yield and ultimate strength of PB1 bronze and for 660 in psi?
2) What pressure, in psi, will be generated in a .44 caliber bore with 40 grains of black powder behind a .44 round ball?
3) Can you calculate for me both the thick and thin wall hoop stress in a .44 caliber barrel at the breech if the breech diameter is approximately 1.5 inches ?
4) Can you show, by calculation, how much permanent deformation (i.e. yield in inches) is expected at that pressure in the bore and what the increase in bore diameter will be for a barrel made of both alloys?
5) Can you explain why bore liners that are designed in themselves not to fail during firing would cause the outer jacket, of what then really amounts to decorative metal, to fail catastrophically?

I just want to be clear I understand why 660 would be OK but PB1 is not and your recommendation to Velocity that he scrap this model because of your certainty that it will eventually, but surely, fail in firing. I am assuming that your certainty that the gun will fail is based on something more substantial than personal conjecture. (i.e. Examples of similar PB1 cannon barrels that have actually failed? Stress calculations that show the actual working stress exceeds the yield and / or ultimate strength of the PB1 material? Or ?????

Thanks.

Yield strength is misleading in this application.

Elongation is the true test:

932 (SAE 660)= 10% Min

PB1= 6% Min

And yes, see pinned post at the beginning of Cannons.

And I have seen a NASA Electrical Engineer replace a fine thread machine screw with a coarse cut wood screw in the ignition system for a Triumph motorcycle.

And the video of heat tiles falling off the space shuttle.

Btw, I was certified as a cannoneer by the Commonwealth of Massachusetts, for what it is worth.

 

[Musketeer]

davec2, I'm not an engineer or expert of any sort, but I respect Claypipe's opinion on these matters. Aside from having experience with cannon of various sorts, he used to make and sell handgonnes as well and has lots of experience with them. I trust that he knows what he's talking about. That's why I agreed that Paul should follow his advice in this case. No more and no less than that. :thumbsup:

 

[davec2]

Claypipe,

To respond;

You state, "Yield strength is misleading in this application. Elongation is the true test:
932 (SAE 660)= 10% Min PB1= 6% Min"

Elongation properties are only of interest if the material in question yields. If there is no yield (i.e. the yield stress is not exceeded under load and the material remains within its elastic limits) there is NO ELONGATION and no fatigue. The calculations I asked about in my previous post will show that even at unrealistically high chamber pressures, the hoop stress in the PB1 barrel is less than 1/3 of the minimum yield stress. And if you double the completely unrealistic pressure, you are only at two thirds of the minimum yield stress. That means that the material does not yield, it does not elongate, and it does not fatigue. So whether the material has 6% or 10% elongation, in this case, makes no difference. As a case in point, grey cast iron has an elongation of 0.5% and has been used successfully for cannon for centuries. By the theory of "less than 10% elongation will result in a catastrophic failure of the gun" every cast iron gun in history should have eventually failed.

"And yes, see pinned post at the beginning of Cannons."

I see not a single applicable instance of someone who carefully made and correctly fired a cannon barrel from PB1 that failed in service. The cannon disasters noted are a collection of loading accidents, dumb mistakes, and people attempting to fire charges in all manner of pipes, tubes, and lawn ornaments never intended to be serviceable cannons.

"And I have seen a NASA Electrical Engineer replace a fine thread machine screw with a coarse cut wood screw in the ignition system for a Triumph motorcycle."

Well, because an electrical engineer makes a mechanical engineering mistake does not invalidate the hoop stress calculations that tell you specifically that Velocity's barrel is perfectly safe to fire.

"And the video of heat tiles falling off the space shuttle."

This is a thermal issue with a glue bond joint under extreme heat conditions on the skin of a space craft. Sighting this as justification for telling Velocity that his barrel will fail is tantamount to saying that because professional engineers designed the Ford Pinto and it had safety issues, the hoop stress calculations are wrong and Velocity's barrel will fail as predicted.


Velocity - Your barrel is perfectly safe to fire as is. Claypipe has expressed his unsubstantiated opinion and I have sent you the hoop stress calculations by PM that should make you feel comfortable that the barrel is fine as is made out of PB1 bronze alloy. I predict that Claypipe will respond by telling you that you can go ahead and blow yourself up if you want to, he has warned you based on his gut feel that PB1 is not a suitable alloy for your barrel. I will leave it up to you, but if you decide he is correct, I would love to buy the barrel from you so I can shoot it. I would have no problem with firing it at all.

P.S. for Claypipe - You answered not a single one of my questions in my original post on this topic with any factual information. I would ask that if you want to continue this discussion, you first answer them directly and not with oblique references. They define the engineering required to substantiate your concerns about this barrel.

Thanks

 

[Zonie]

For what it's worth, elongation by itself means little.

If it were truly the only thing that matters when it comes to barrel safety, the barrel would be made from lead (elongation = 16-75 depending on alloy).

Yield strength, Tensile strength and elongation are all important properties that are critical to the life of a pressure vessel such as a cannon or gun barrel.

davec2: Although it doesn't list data for a .40 caliber patched roundball, the Lyman "BLACK POWDER HANDBOOK AND LOADING MANUAL" Vol 2 does show the breech pressures for a .36 caliber barrel with a .40 grain 2Fg black powder load.
The pressure was found to be 9,400 psi.
This is going to be higher than the same powder load in a .40 caliber barrel.

For instance, the same 40 grain 2Fg powder load in a .45 caliber bore shooting a patched roundball was found to be 5,400 psi.

I have no feel for the barrel wall on the cannon in the OP but if this information was known it wouldn't be difficult to calculate the strength of the barrel.

Of course, being a gun barrel that is subjected to explosive pressure rises must be considered in the final answer.

 

[davec2]

Zonie,

You are exactly correct, "elongation by itself means little.....Yield strength, Tensile strength and elongation are all important properties that are critical to the life of a pressure vessel such as a cannon or gun barrel."

The pressure I used for the hoop stress calcs I sent Velocity was 10,000 psi. And then I doubled it to 20,000 psi - far beyond what would be possible in a .44 cal tube with 40 grains of BP. And at that ridiculous pressure, the hoop stress does not even approach 65% of what would be required to yield the barrel. In reality, the pressure will be much more like 5,000 psi and the hoop stress would only be 1/6th of the minimum yield strength. Claypipe's concern about the safety of this barrel is completely unfounded.

And I am glad to note that Old Ford notes that, "I have long experience in metal fatigue and I doubt very much that you will ever have any problems in shooting your fine cannon."

 

[F.G. Ford]

Once again to repeat my self, GREAT LOOKING barrel.
Very fine workmanship. You should be proud!
Would you mind if I copied your design?
All the best!
Fred

 

The firing of a tube places repeated sudden shock to the material it is manufactured from. PB1 is not up to this. Even tubes made of the proper materials have a given life.

So you advocate ticking time bombs? There are countless numbers of pieces, made from improper materials, out there. And not everyone who owns one is going to take the time to carefully, and properly, load them. Many of these were passed down family lines and bought and sold at estate sales, garage and yard sales, and let's not leave out flea markets.

Many will be loaded with a wide variety of powders, from match heads, powder gleaned from fireworks, shotgun shells, rifle and pistol cartridges. And now, you want to add tubes made from improper materials to the mix. I'd say that is a recipe for disaster.

My grandfather was a tool and die maker. He worked for the Government during WWII. He impressed on me, the right material and the right tool for the job.

Now, show me any legitimate manufacturer of salute cannons that uses PB1. You'll find the industry standard is 660.

 

[Paul Buchel]

Hi all.

Firstly, I would like to thank Davec2 for the PM, he put a lot of effort into his calculations making it easy to understand. So I have to go with Dave on this one, unless someone can prove otherwise.

But I would assume your intentions are not to compete with a rail gun for velocities, and will shoot only black powder.
No Fred, Black powder only, and I will remain conservative.

128 grain round ball, 25 grains fff = 730 f/ps
128 grain round ball, 40 grains fff = 840 f/ps

I don't think 100 f/ps makes a huge difference, so I will take it from there. I can't import fuse , so I have to make my own. The deck carriage is coming on nicely.

It has been very valuable joining this forum and I thank you all for you input.

Regards Paul.

 

For what it's worth, elongation by itself means little.

If it were truly the only thing that matters when it comes to barrel safety, the barrel would be made from lead (elongation = 16-75 depending on alloy).

Yield strength, Tensile strength and elongation are all important properties that are critical to the life of a pressure vessel such as a cannon or gun barrel.

davec2: Although it doesn't list data for a .40 caliber patched roundball, the Lyman "BLACK POWDER HANDBOOK AND LOADING MANUAL" Vol 2 does show the breech pressures for a .36 caliber barrel with a .40 grain 2Fg black powder load.
The pressure was found to be 9,400 psi.
This is going to be higher than the same powder load in a .40 caliber barrel.

For instance, the same 40 grain 2Fg powder load in a .45 caliber bore shooting a patched roundball was found to be 5,400 psi.

I have no feel for the barrel wall on the cannon in the OP but if this information was known it wouldn't be difficult to calculate the strength of the barrel.

Of course, being a gun barrel that is subjected to explosive pressure rises must be considered in the final answer.

I beg to differ, elongation is a major safety factor.

To Davec2, I ask:

Which, of PB1 and 660:

Would be more likely to fracture into shrapnel, during a catastrophic failure?

Which would be more likely to split with little or no shrapnel, during a catastrophic failure?

Which would be less likely to burst, resulting in a bulge when over pressured?

Which would burst into shrapnel without warning due to metal fatigue from repeated discharges?

Here you will find the properties you requested:

http://www.metals4u.co.uk/SAE-660-Bronze.asp

http://www.metals4u.co.uk/PB1-Bronze.asp

Though, you being an rocket propulsion engineer, familiar with highly stressed materials operating near their mechanical property limits, why you wanted me to look up, what you should have in a reference guide on your desk, or could have easily called up on your computer, puzzles me.

 

[Paul Buchel]

Once again to repeat my self, GREAT LOOKING barrel.
Very fine workmanship. You should be proud!
Would you mind if I copied your design?
All the best!
Fred

Thanks very much Fred, I bought the plans from Outpost Enterprises in Ohio. www.outpostenterprises.com. I think I paid $17. They are plans from Jerry E. Howell, they include the carriage. I would gladly send you mine, but it would be a copy right infringement.

All the best too Fred.

 

[davec2]

Claypipe,

This has been fun !!! I ask specific engineering questions like, “why is PB1 with an elongation of 6 to 8% not good for a cannon but cast grey iron with an elongation of 0.5% has been used successfully for centuries?” And you answer with a quote from your grandfather about using “the right tool and right material for the job.” Your grandfather was correct, of course, but that quote has answered none of my specific questions about your condemning Velocity’s cannon to the scrap heap over a 2% difference in elongation properties.

Since I do not have time to continue these entertaining forum exchanges, I concede your point. You win. However, I would like to enumerate what I have learned from you in this discussion;

1) Yield and ultimate strength of materials, although used extensively in the engineering world, are completely unimportant in cannon barrel design. Only elongation is important. Therefore, as mentioned by Zonie, lead is one of the best materials for cannon barrels because of its fantastic elongation properties.

2) SEA 660 is OK for cannon barrels at 10% elongation, but PB1 is not at 6 to 8%. Therefore, since grey cast iron has an elongation of only 0.5% (!!!!! i.e. one twentieth of 660), ALL cast iron guns should be immediately spiked and filled with concrete as they will ALL surely burst. (This may take a while to accomplish because cast iron has been successfully used for centuries to cast God knows how many cannon.)

3) Even though barrel liners are required by the National Safety Rules and Procedures For Shooting Muzzleloading Artillery, barrel liners really do no good at all. To quote you exactly, “Even lining the barrel leaves a question of safety. The liner will swell on discharge. Sooner or later the outer skin may fracture and become dangerous shrapnel. Tick, tick, tick...” (By the way, confusingly enough, the material requirement in the “Rules” for the liner quotes a yield strength and does not quote an elongation”¦..????)

4) Hoop stress calculations, used every day in pressure vessel, piping, hydraulic, and even modern gun barrel design work is apparently meaningless. Even if the calculations say a particular design and material are OK, don’t believe it. Otherwise you are, again to quote you, “advocate(ing) ticking time bombs”¦”

5) Contrary to all material science rules (and even the definition quoted by Musketeer VB in an earlier post), materials don’t need to yield to elongate. How that works, only you seem to know. However, I am at a loss to explain how that might work. ?????

6) Even cannon made from “Claypipe Approved” materials will undoubtedly be eventually used by idiots who will load them improperly and / or load them with improper propellants up to and including flash powder ( i.e. firecracker filler) and smokeless powders”¦.perhaps even C4 or TNT. Therefore, even well made cannons fabricated of “approved” materials should immediately be destroyed to keep future numbnuts from screwing up and killing themselves and others. (As a matter of note, this provision should probably be applied to ALL firearms”¦How many of us have seen or heard of idiots who carelessly got mud in a barrel or chambered the incorrect ammunition and blew up a perfectly good and properly made gun by being stupid.) Of course, you can attempt to make a barrel “idiot proof” by using, not SAE 660, but something REALLY good and expensive like INCO 718 or CABOT 214. The only problem is that as soon as you make something “idiot proof” someone will undoubtedly come up with a better idiot.

7) So, as we have now concluded that all badly made and even well made guns should be destroyed or made completely inoperable for safety reasons, there really is no longer a point to having the “Cannon” sub forum active on this site. Unless, of course, we just want to change the heading to “Cannon Look-a-Like Door Stops”.

One last point. Since there are no facial expressions or voice inflections on the computer screen, I need to tell anyone who may have missed it while reading this that I am saying everything in this post “tongue-in-cheek” and with a fair dose of humor. I apologize to all of you for taking up valuable Forum time and space with something as mundane as engineering science. I have enjoyed our exchange, Claypipe, and I genuinely know your heart and concern are in the right place. We are just disagreeing on how much, from a material point of view, is “good enough”. One of my engineering principles is not to over engineer something. (Most of what I build has to fly). It needs to be robust and safe, but as the adage goes, “better is the enemy of good enough.” Is 660 better for a barrel”¦..probably. Is PB1 safe for Velocity’s .44 cal barrel with a 1.5 inch breech diameter”¦.absolutely.

Thanks”¦And as I said, it’s been fun.

Respectfully,
Dave C