Do bronze tubes need to be lined

[Soot Sucker]

I know we are talking cast iron but What about Bronze? Does it need to be lined?

Cannon LTD states (in part) on their website that:

"Cast gray iron tubes have a pressure rating of about 40,000 pounds per square inch; mild steel tubes have a rating of about 60,000 pounds per square inch and Naval bronze tubes have a rating of 65,000 pounds per square inch. So, as you can see, bronze tubes are the strongest."

Also, Jim from "Beaufort Naval Armorers" states his high manganese bronze mortars have a 90,000 lb per sq inch tensile strength.

Do bronze cannons have to be lined in N-SSA competitions?



Soot

[Double D]

While looking ofr something else I came across this  post that never got answered.  Anybody want to take a shot at it.







 

[GGaskill]

The opening 7 sentences of the N-SSA rules for cannon Section 10.2 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. All reproduction barrels must be made of iron, steel or bronze. All reproduction barrels and those original barrels failing inspection must be lined with a bore liner of extruded seamless steel tubing of a minimum ANSI standard and of a minimum 3/8-inch wall thickness. The liner must be closed at the breech end with a steel plug, sweat-fitted into the liner and welded. The breech plug must have a radius of at least 25 percent of the bore radius and be at least 1 inch thick at its thinnest point."  (My boldface.)

If you want to shoot N-SSA events, this is your guide.  While I have some quarrel with some of the details of the rule, that is what they are.

On the other hand, bronze was used without steel liners for a long time because it was not brittle like cast iron.  If you are duplicating a design of the past that was bronze in bronze, I see no reason why you need a steel liner, assuming qualified manufacture, but it does provide some additional safety, although you shouldn't be loading in the realm of danger anyway.

[Artilleryman]

It depends on how you read the sentence, "All reproduction barrels........."   It sounds like all reproduction barrels period, but I believe it means all barrels original or reproduction "failing inspection" must be lined.  I know of a bronze reproduction Napoleon that is being used in the N-SSA without a liner.

[GGaskill]

I certainly don't want to get into an argument over this, and I don't know what the N-SSA inspectors actually do, but the the grammar undeniably says that all reproduction barrels must have a liner.  Whether that is what they mean, I don't know either.  If they wanted to mean only those barrels failing inspection need a liner, the rule should be written, "All barrels failing inspection must be lined ..." 

They should also rephrase the next sentence with a generally understood description of what "sweat-fitted" means.  I assume they mean shrink fitted as I have never seen the term sweat-fitted used anywhere else.

I'm sure this kind of equivocal rule gets easily explained at the one-on-one level but it is hard to determine the exact meaning from just the written rules.

[Artilleryman]

GGaskill, No argument from me.  I like rules to be clearly stated and applied.  It reminds me of papers I corrected that my students wrote.  I would mark something wrong and their argument would be "well you know what I meant".  My reply would be that they had to write what they meant because I wasn't going to guess at it.  I just know from past experience in the N-SSA artillery competition (27 years) what is being done.  The rules need to be clarified.

[Cat Whisperer]

I know we are talking cast iron but What about Bronze? Does it need to be lined?
...
 So, as you can see, bronze tubes are the strongest."
...
Soot

Two factors:  one, strength.  Agree.  Two, the ability to withstand repeated stressing - without becoming brittle. 

One discovers the inability to do the second not early-on but at the point of catestrophic failure.  This is a function of both amount of the size of the  charge and of repeition.

In the US artillary a log book is kept where EVERY round and charge is documented.  (They've got the process down!)  I've talked with a half-dozen folks that have been using the howizers at the end of tube life (4,000 full-charge equivalent rounds) and they inspect the tube muzzle at EVERY round when close to the 4,000 mark.  Several have told stoires of cracks appearing and grapefruit sizes of metal breaking out - right at the end.

[cannonmn]

That brings back a story I was told by an artilleryman who served in 155mm Self-propelled howitzers. 

There was a special round in the inventory where the drill was this:

Load it, fire it, and abandon the vehicle.  The reason was because that round was about 120 lbs,, which was more than their usual 100-lb. or less rounds, and also because it had a special hotter charge (zone 8?) to kick it as far as it needed to go.  That one round put enough stress on the barrel to consider it fully expended and not capable of any further firing.

[Cat Whisperer]

The rounds we fired (1972) were all about 64 lbs.  Charges 1 through 7 (firing charge 7 had all of them) charge 7 was only about 1/2" thick, charge 1 being 4 or 5 inches thick.

The tube of the 155SP would recoil 36-42" back (leaving only about 6" behind it - one ALWAYS stood to the side).  At the same time the tracks at the front would clear the ground - great fun inside.

[cannonmn]

If you want to know what's acceptable and not within the NSSA, you can post on NSSA forum and their official inspector, J. West, may answer it.  He answered one just yesterday regarding the need for a liner on cast iron guns.

[Artilleryman]

Rob West is the N-SSA National Artillery Officer, James West is his brother.