Caliber vs wall thickness

[BoomLover]

I know that you should have wall thickness equal to the bore, so, retorically speaking, is there a "fudge" factor that might be acceptable? What I'm looking at is a shaft of mild steel 5" diameter by 36" long. Doing the math, a 1.75" bore (times 3) (wall+bore+wall) would equal 5 1/4". How critical is that formula? Is it ok to drop that 1/4" in order to get the Golf Ball Bore in this size of material? Thanks, BoomLover

[dan610324]

of course you can reduce the wall thickness slightly when you make a cannon from a piece of solid steel
the one caliber rule is very old , I have read about it in early 1600 documents
but at that time as a recommendation for cast bronze guns
the cast iron guns were recomended to have 1,25 to 1,5 times the bore diameter in wall thickness
but that was 400 years ago and the quality of the castings wasnt as good back then as they are today .
so my opinion in this subject is : go for it
you still got a much stronger gun then a sleved cast iron gun for example that hold the 1 cal rule in my opinion

[Double D]

Actually the old rule found in Muller is thinner, don't have it at my finger tips right now, I believe it is 2/3rds.  The Current one caliber comes from the N-SSA rules and falls into the overbuild catagory.   The one caliber rule is an established safety rule.  Safety rules don't have fudge factors.

If you want to build a cannon to shoot in N-SSA you must meet this rule to shoot and be safe.  Absent any other creditiable reference the One Caliber rule is the one we cite here.

The engineers can design and build you a gun with much thinner walls.  They will call out a specific grade of steel and construction method. The whole process is controlled and we know of what and how the gun is constructed. 

With the right steel and building techniques you can go thinner.  You just have to know those steels and techiques.

[dan610324]

another idea would be to chamber the barrel slightly
1,5 inch powder chamber and you are at the safe side

[GGaskill]

The bronze M1857 Napoleon 12 pounder is 11" in outside diameter and 4.62" bore and is considered "safe" by the various groups, yet a steel cannon made to the same dimensions would not meet the one caliber wall thickness rule. 

While there is no way one could guarantee only the use of golf balls in a gun of that caliber, they are of such low mass that no significant pressure can build behind them when used with a rational powder charge.  Keep in mind, however, that a one pound lead sphere will fit that bore so they could be used as shot also with a correspondingly higher pressure.

[RocklockI]

are you talking chamber area or bore ?

[Double D]

Chamber and bore would be the same in a cannon.  Chamber would be smaller than bore in a mortar or howitzer, and the one caliber rule would apply to the chamber.

[BoomLover]

If nothng else, I'm all for safety! I'll re-measure to make sure, but I'm pretty sure it is 5". Therefore, the biggest I should attempt would be 1.66" bore, too much of a squeeze for a golf ball. That would be if I were looking at N-SSA rules, which as Double D said, are "over-built" for safety. I could be sure that I would only fire golf balls in it, however, should it ever be sold, ect., who could control the use farther down the line, once out of my hands? I know a 1/4 inch translates to actually 1/8" all around the circumfrence, so we are talking a pretty small amount of side wall thickness. I also don't have any desire to fire it where N-SSA rules would apply. I'll ponder it for a bit more to see what I come up with. It would make a right nice size cannon, and if I did decide to go for it, I could aways make it with a powder chamber, for safety.Thanks for all the imput! BoomLover   

[Double D]

So, it's 1.66 max, get a mould and  move into the next level from shooting sporting goods to real cannon balls.

[Ex 49'er]

So, it's 1.66 max, get a mould and  move into the next level from shooting sporting goods to real cannon balls.

GB's  ......nothing i've tried makes them fly true the sabot helps but not enough to waste them on GB's
gary

It looks like it would be prudent to discount accuracy of any kind when shooting golfballs. I have to agree with DD. Get a
separate mold and roll your own. 

[BoomLover]

Might have the solution...just took a good look at a friends 1 1/2" bore, that is a right nice size, too! And  can find projos and balls that size quite available, wouldn't have to worry about wall thickness, cuz it would be really over-built. Now got to talk to the "bore-borer" and make sure his 7 foot bed lathe can support a 5" X 36" chunk of future barrel! And I know I could always go for a 2.25" bore Howitzer, already have balls (lead!) that big... BoomLover