[kurt98]

I am building a cannon out of 2 inch diameter stock with a one inch bore. That gives me half inch thick walls. I am going to use gunpowder as my fuel. Is it possible that the cannon explodes and throws shrapnel every where? I know it could happen but how much gunpowder would it take to blow through half inch of steel.

[pastera]

Very possible that it will blow up.
The amount of power would depend on type and condition of the steel, the projectile size/mass, wadding, type of powder ... too many variables to safely give you an estimate.


Aaron

[steve323]

Ever notice that cannons are usually really thick near the base. There must be a reason. Be safe.

[Stepper Monkey]

Asking "how thick" is putting the cart before the horse. Thickness is only relevant once you know what the material and the calculated pressures are going to be.

As well, there is consistency. Last time we built a cannon we used forged, seamless, DOM pipe. Most tubing/piping is not going to be consistent due to seaming, internal stresses, heat treating, etc.
No matter how thick, you don't want something becoming embrittled and cracking or splitting on you.

This isn't a hard project to do at all if you just sit down and do the math, and know the alloy and construction method of your tube. Probably find cheap or free scrap that will do the task pretty easy.
If you don't know that math, learn it, find someone who does, or drop the project before you blow your ears loose.

[Fluxion]

I have been intested in small cannons my whole life. I have built a few display models and a few for firing with firecrackers and one carbide cannon. I want to build a black powder cannon. I understand the need for doing the math first and choosing the alloy for the barrel.

For my first black powder cannon I want it to have a 0.440" bore since I have quite a few pounds of 45 cal. lead balls on hand. Can anybody here help out with the math envolved? What alloys are good to use?

[Stepper Monkey]

For the small ones I just cheat and use unturned barrel blanks. The barrels set up for people making flintlock or percussion kits can be pretty thick-walled, leaving plenty of room to turn a cannon to scale proportion and leave plenty of meat. I have a .58 made from a 5-inch chunk of rifle barrel end cut.
The pressures are not that great with smaller bore models, leaving more leeway. Most scale proportions in brass will even work. The trouble comes in when you start trying to move balls way bigger than musket ammo!

[kurt98]

I shot my cannon today. I wrapped an round electrical fuse in paper for my projectile. It shot through a piece of ply wood 100 feet away.

[ImanCarrot]

I made a small cannon with a 1/2 inch bore... made all the chassis out of hand carved wood with little wheels and everything.

I used a ball of plasticine wrapped in paper and talcum powder as shot. I used a shotgun load of gunpowder (was VERY careful cutting up the shotgun shell).

I'd drilled a small hole at the thick end through which I poked a red hot bit of wire to set it off...

Well, the plasticine blew several holes in my living room wall (plastered brick) about 1cm deep with a spread of about 12" diameter as the cannon shot backwards about 9 feet into the other wall (my cat shot off in the other direction at a high rate of knots). The cannon chassis was wrecked and my ears were still ringing an hour later lol.

I consigned the project to my "to do" bin lol, good fun but take care hehe.

[riverrat]

NEVER USE TALCUM POWDER OR FLOUR IN LOADS OF ANY KIND!!!!!!
It compresses and swells in the bore causing an overpressure condition!
Be sure with black powder to use the right granulation, finer powders
like fffg are typically for .50 and smaller ffg is for .50 up to not sure
how big, "thats all I know from muzzleloaders" with cannons please
be careful guys you are throwing out a tremendous piece of lead.
A 1 inch projectile would probably go completely through a home or
a car.
my big ol .02 from growing up with firearms.

[kurt98]

I am thinking of making a 1 inch round steel projectile next. I want to see if i can blow a tree down. Where i will be shooting it there is 5000 feet of woods with no buildings.

[dsharp]

you may want to do some research on the greybeard site so you'll make it to 18.

[dsharp]

http://www.gbocannons.com/ Seriously, be careful what you are using for projectiles and types of powder. Powders produce a wide range of pressures.

[Stepper Monkey]

Be sure with black powder to use the right granulation, finer powders
like fffg are typically for .50 and smaller ffg is for .50 up to not sure
how big, "thats all I know from muzzleloaders" with cannons please
be careful guys you are throwing out a tremendous piece of lead.

General rules of thumb (I own a number of muzzleloaders);
FFFFg is only for priming flintlock flashpans, NOTHING else.
FFFg is generally for pistols and smaller bore sizes.
FFg is indeed good for medium to large bore rifles.
Fg is for Shotguns and other very large bore guns, like cannon.

My 10 gauge throws a .775 inch round ball, and my 12 gauge a .68 round using Fg. This is a very important distinction, as MASS, not bore size, determines safe powder usage. Fg is the only safe alternative for high mass items - even a .50 bore with a longer, heavier projectile (and hence more mass than a round one) can be enough to need the coarser powder charge.
In short, the time it takes to get the higher mass moving requires the use of a coarser, and therefore slower burning powder so as not to get a pressure spike.
Faster powders do not necessarily mean more power or speed. The point is a slow steady push, not a short fast spike - Try to get a bowling ball moving down the lane by kicking it really hard and you'll see what I mean. Both your level of actual success, and your medical bills, will bear some similarity to using too fast a powder in a cannon.

Also, unless you use a cleaner burning Black powder equivalent like Pyrodex, you will need to patch your projectile and soak the patch in a bore solvent, otherwise the buildup of fouling is fast and impressive. This will cause you no end of trouble as after a shot or two you can not only break rods trying to jam successive projectiles into the now tighter bore, they will also have a much tougher time leaving the bore possibly leading again to unsafe pressures.

[gdb]

HI guys,
I built a cannon that shoots golf balls.
I us a brass shotgun shell load of powder. ( Goef) ffg or fffg.
Works great.

Glen

[riverrat]

thank you stepper monkey,
you just put my thoughts into words i couldn't articulate.
mabey somebody won't blow themselves up because of this.
be careful boy's overpressure is NOT!! pretty.
i actually broke a perfectly good 11-87 super magnum once by
not throwing a blank charge before fireing up the progressive
loader. it would seem that gravity over time compresses smokeless
powder, huh, who would of thought.

[Daninwyoming]

In answer to stepper monkey, Wrong! The pressures in a small bore can be just as great as in a big bore. Check out hatchergun.com under black powder cannons.

[riverrat]

dang daninwyoming, i didn't see any post that stepper monkey wrote
that said anything about small bore vs. a big bore pressure variable.
what stepper monkey and i were trying to get out was the difference
in powder granulations of black powder and thier proper use.

smokeless powder is considered a propellant, black powder on the other
hand is an explosive. very different critters, considering controlling
the "explosion" is done by grain size in black powder.
smaller grain sizes ignite VERY rapidly, while larger ones ignite slower.
smaller projectile = smaller grain size.
larger projectile = larger grain size.
if i put ffffg in my .50 smokepole it would most likely blow up in my face,
AND, have VERY! high pressure.

da not blown up riverrat

[Stepper Monkey]

Yeah, I didn't quite understand how that comment relates in context to the information in my posts either. The correct use of black powder granulation is pretty well established.

He did make a fundamentally correct statement however. Pressures can be just as high in smaller bore cannon for assorted reasons, not the least of which is the finer powder used, which goes back to why there are different granulations in the first place - choosing the appropriate safe pressure.