Vent?

[treeman]

I don't understand why I would need a vent, if I use a seamless liner. Can anyone explain? Another question, how much pressure should a seamless 1.75 bore with 9/16 wall thickness handle?

[GGaskill]

The vent is the passage through which the fuse or other ignition system enters the charge.  What probably is meant is you need a vent liner to bridge the joint between the tubing and the external barrel.  This is to prevent fouling from entering that joint and causing corrosion.

Regarding the capacity of the liner, I cannot say because I don't have the tensile strength of the material available.  However, for a 20000 psi chamber pressure, the liner by itself would see about 43,600 psi stress.  Because the liner will expand from the pressure, the external barrel will share some of the load.

[seacoastartillery]

     Treeman,    Looks like George gave you the technical reasons for installing a vent liner.  We install these in every seacoast gun re-creation that we build even though we do not use liners, but rather 4150 steel at 32 Rc.  We have not had any problems drilling the liner hole, threading it or screwing in the liner.  The slightly tricky part is drilling the liner material with the small drills that we use to maintain as close to a 1/6th scale as we can.  We drill .078" dia holes in a pure copper rod, thread it, square the end for a wrench and install it in the threaded vent after bluing the tube.  The square part is then carefully filed off with three layers of masking tape protecting the blued steel around the vent. The photo below demonstrates that the appearance is also improved by installing a vent.





     Historically, both sides during the Civil War used vent liners to reduce vent erosion, especially on the high pressure, heavy projectile seacoast guns.  During our research on the 7 Inch Treble-Banded Brooke Seacoast and Navy Rifle, we learned that CSN Commander John M. Brooke and his assistants had a devil of a time keeping the vent liner of solid copper from collapsing near it's intersection with the bore.  They tried everything, but had no luck until they had a Confederate spy in Connecticut obtain some platinum and then pass it along to contacts who brought it to Richmond where Brooke's workmen at the Tredegar Foundry plated the copper liner and installed it. They had some failures, but the platinum seemed to help.  The pressure in this seacoast rifle has been estimated as being upwards of 50,000 Lbs./Sq.In. when an Ironclad Penetration load of 20 Lbs. of BP and a 120 Lb. wrought iron bolt was used.  8" of wrought iron plates was penetrated by this load at 285 yards during testing.  Brooke believed if they could lure the Federal Monitors within 500 yards, they would have a chance.  It never happened. 

     You can see, in the photo below, the head of the stainless steel bolt that we use to simulate platinum plated copper in the Confederate guns we are building now.  In our experience, most stainless steel used for no-rust bolts is fairly soft and can be drilled easier than pure copper.





Good luck,

Mike and Tracy


     

[treeman]

If I just use the 9/16 wall seamless, how much pressure will it handle? Approximately how much BP for the 1.75 bore?

[Double D]

The American Artillery Association Rules now specifically state "The bore should be lined with seamless steel tubing with a minimum 3/8-inch wall thickness and a yield strength of 85,000 psi or greater."

[GGaskill]

If I just use the 9/16 wall seamless, how much pressure will it handle?

Thought I answered that in post #1 above; can't tell you without knowing exactly what material is used for the liner.  If you used 85000 psi steel for the liner, it would take a chamber pressure of about 39000 psi to reach 85000 psi stress in the liner if used alone.  However, lliners are only needed if the barrel is made of cast iron or bronze.  It would be absurd to require a liner in an all steel barrel.

However, generally we do not recommend loading to maximum possible pressures as it gives range beyond which you can control the landing of the shot (see the Mythbusters thread) as well as adding the danger of bursting the barrel, which is an event you do not want to witness in person.

[Double D]

All steel barrel is the liner, a profiled liner as long as it exceed 3/8" wall

[RocklockI]

If I just use the 9/16 wall seamless, how much pressure will it handle? Approximately how much BP for the 1.75 bore?

Here is the answer .... 'NoBody Knows' (the trouble I seeed ) ,Really there is no "answer" to that question . You must watch for pressure signs. What is the Barrel made of How is the liner breeched ? "plug wise" .
 
Just start low !!!   no kidding start with 200 grains of powder . I would work up ..with long fuses...To whatever you think you need . What ammo will you use ? THAT makes a huge differance ! With GB's you can't over load it ! If you put a Fox Ball in it you better be very carefull ! Start all over olow and work your way up . Good Luck !
 
And after you are happy ,that only means that is the load FOR THAT CANNON no other !
 
Just be carefull and aware ..... you'll be fine .
 
Personally I do NOT put vent liners in my Bronze guns , Some people may but I don't believe it is necessary . George does your Bronze howie have a liner ? My mentor Dan never mentioned that they are needed .
 
Gary
 
 

[GGaskill]

All of my bronze pieces are unlined so they have no vent liners.  However, if they get shot to the extent that the vent gets too large, I will drill and tap them and insert a replacable vent liner.  At the rate they are being fired, that will not happen in my lifetime even if I live to be 90.

[treeman]

We are wanting to build it to shoot golf balls, but I wanted to make it extremely safe. Thanks for all the help guys, it's appreciated.

[Zulu]

treeman,
What type of barrel is your liner going in?
Zulu

[Double D]

Solid barrels had vent liners to address the issue of vent erosion form repeated firing.   

Here is the vent of an original Mountain Howitzer---The Big Hole Cannon.  The vent is lined.

[treeman]

treeman,
What type of barrel is your liner going in?
Zulu

We had planned on a liner, but now we're thinking the 9/16 wall will be the barrel, no liner.

[Zulu]

treeman,
What type of barrel is your liner going in?
Zulu

We had planned on a liner, but now we're thinking the 9/16 wall will be the barrel, no liner.

So you are just going to have a straight piece of pipe for a barrel?  Is it going to be mounted on a carriage?  Is it going to have trunnions?
Zulu

[seacoastartillery]

treeman,

What type of barrel is your liner going in?      Zulu

We had planned on a liner, but now we're thinking the 9/16" wall will be the barrel, no liner.     

     We will let the Robot from "Lost in Space" speak for us.  "Danger, Will Robinson! Danger!"

M&T

[Double D]

I don't understand why I would need a vent, if I use a seamless liner. Can anyone explain? Another question, how much pressure should a seamless 1.75 bore with 9/16 wall thickness handle?

If you make a cannon from solid piece of steel then you don't need a liner.   But the the walls over you powder chamber need to be one caliber thick to meet minimum recommended safety standards.

A 1.75 inch bore need walls over the powder chamber 1.75 thick.

[treeman]

Can I use the seamless for the liner, then add 1/2 inch wall over that, and another 1/2 inch wall over that. In other words, I would be using 3 pipes, stepping down toward the muzzle...

[Zulu]

Can I use the seamless for the liner, then add 1/2 inch wall over that, and another 1/2 inch wall over that. In other words, I would be using 3 pipes, stepping down toward the muzzle...

And your gun will just look like a pipe?  Will it have trunnions?  Will it be mounted on a carriage?
Zulu

[treeman]

Will be mounted on a carriage. Not sure what trunnions are :-)

[subdjoe]

Will be mounted on a carriage. Not sure what trunnions are :-)

ADDED:

May I respectfully suggest that you thoroughly peruse the stickys here, along with other sources on muzzle loading cannon, or civil war cannon, and become very familiar with the parts, construction, and operation before you start building anything.  While this can be very fun and addicting, it can also be VERY dangerous.  A catastrophic failure would not be pretty.  Nor would a premature ignition of a charge while loading.  And it may "only" be a golf ball, but one out of a cannon can go through walls, or people, or, I think, cars.  These are not toys.

[Double D]

Treeman,

I think we all get the impression you don't know much about cannons and cannon construction.  But what  I like about you, is you are asking questions.  That is important, ask questions an learn.  Keep it up.

We all started like you learning by asking questions.  We now are all willing to share that knowledge we gained, with you.

[treeman]

Your impression is correct, I know zero about building cannons :-)  We are more into antique and military firearms, but decided to build a cannon for the fun of it. It's a good thing we did not go with our initial "gut feeling" idea, but decided to research and ask questions. I'm thinking that, for the charges we will use, the specs are overkill. On the other hand, though we will use low charges and golf balls, I would like to build it so that it is capable of firing real charges and ammo. I do appreciate all the information, and certainly acknowledge my ignorance on the subject.

[Cat Whisperer]

treeman -

Keep us posted.  Lots of pics too.  This is going to be a FUN adventure!

You are persuing a path that some of us don't - some are into just shooting, others into accuracy, and still others who are more into the histerical side of artillery.  We ALL learn from the discussions.

DD and I established this forum so that WE could learn!

[flagman1776]

I think you are wise to build your cannon to solid specifications...  You might know that you have only built a blank gun.  You you not want to leave a bomb for your heirs & assigns forever...  as your legacy. 

[Double D]

Your impression is correct, I know zero about building cannons :-)  We are more into antique and military firearms, but decided to build a cannon for the fun of it. It's a good thing we did not go with our initial "gut feeling" idea, but decided to research and ask questions. I'm thinking that, for the charges we will use, the specs are overkill. On the other hand, though we will use low charges and golf balls, I would like to build it so that it is capable of firing real charges and ammo. I do appreciate all the information, and certainly acknowledge my ignorance on the subject.

The majority of the busting accidents we see reported here are from shooting  blanks.  Blank loads are not no pressure loads.  Do not build a gun for how you will use it, build if for how the next guy will use it.

[Zulu]

Can I use the seamless for the liner, then add 1/2 inch wall over that, and another 1/2 inch wall over that. In other words, I would be using 3 pipes, stepping down toward the muzzle...

I also like that treeman is asking questions.
This is an important question and no one has addressed it yet.
Zulu

[Double D]

Can I use the seamless for the liner, then add 1/2 inch wall over that, and another 1/2 inch wall over that. In other words, I would be using 3 pipes, stepping down toward the muzzle...

Yes you could do that but why would you want to do that?   What cannon are you replicating?

Most cannon profiles are not step downs but tapers. 

 

[treeman]

I'm not replicating any actual cannon, just want to build a cannon that will fire a golf ball. The main reason for the stepped idea is that it's hard to find (and expensive) really heavy wall pipe that has the correct ID. We (my brother, myself, and my nephew) normally just shoot,and restore, antique and military rifles. We were bored, and got the idea of building a cannon....
By the way, the guys on a show called "American Guns", built, and sold, a bowling ball cannon that was basically nothing more than an oxygen tank with the bottom cut off. How safe could that be? The show is what gave us the cannon idea, but the more I research, the more I think the "American Guns" cannon is an accident waiting to happen.

[subdjoe]

Treeman, good for you, sticking around and asking questions.  We really aren't trying to beat you up or scare you off.  We just don't want to read about you in the next account of a cannon mishap. 

There are some guns that fall within the scope of this forum that have the stepped appearance you would get with the multiple sleeves.

As others have mentioned, there are many paths to the Tao of Cannon, but safety is paramount. Better to overbuild by double than to underbuild by 1%.

[Zulu]

There are way too many folks out there that show up here for the first time with a cannon they made and are as proud of as a new Papa.  Only to find out that they neglected to follow some basic safety rules that easily could have been avoided if they came here first.
After learning that their pride and joy is a pipe bomb, we usually never hear from them again.  But I'd be willing to bet they are still shooting their barrel.
Good for you treeman for coming here before you went through the trouble and expense.
Zulu