Soldering and brazing.

[napoleonb]

There are several things you want to avoid when you shoot with BP.

Assuming the construction of the barrel is adequate and can hold the pressure involved and you know HOW to load and WHICH load you have to use for your projectile (even a to light load for your projectile weight can result in the explosion of your device)
Using a wrong type of blackpowder (grain size FG, FFG etc.) even the " correct amount" (given for your projectile weight, barrel length and weapon type) will inevitably cause you failure and sorrow.


1
Assuming the construction of the barrel is adequate and can hold the pressure involved after shooting you have to clean out the barrel. The chemical reaction of the explosion leaves among other things sulphuric acid and saltpeter behind which have to be removed. Any voids, cracks, clearances will be filled by explosion gasses and start to corrode IMMEDIATELY, weakening the material and thereby making it a time bomb each time you use it.

Cleaning BP rifle's, pistols, shotguns etc. is generally done by mixing some detergent with hot water. After the water stops discoloring the barrel is rinsed with plain hot water removing all left over detergents. The water also wants to fill voids etc. and start corrosion the same as the gasses would. So the barrel must be completely free from all moist and gas residue after which a good gun oil is used to prevent corrosion.

2
In case of a misfire (charge will not go off) you have got a serious problem. BP is friction sensitive, highly instable, hygroscopic and very easy to set off (but just not in this case when you want it to be). EG poking a stick with a screw on top (non ferrous) to remove whatever obstruction (bullet, wads, cardboard) is in the barrel is what it normally takes to let the screw "bite" the obstruction. And could set of your charge whilst holding on to the stick, and yes I've seen it all happen.

The bigger the bore the more difficult it is to remove the charge because of the force it takes to remove the obstruction.
Making a screw-in breech eliminates most of the danger if great care is taken in making sure the BP can NEVER EVER get in between the threads (friction sensitive)

3
The bore should be even and smooth along the entire barrel, a hiccup of some sort will lead to peak pressures and the possible destruction of your barrel. DOM is the material to go by for this (and the material strength is uniform of course) (also chokes on shotguns are an exception when your load and design match)


If you want a bang, you have to make sure there's a real snug fit or there will be no pressure buildup. This generally makes it just as lethal as a normal bullet would. Difference being that because there is less weight involved in the projectile it loses energy quite fast and the reach is less as a result.

EDIT: perhaps I have to add a disclaimer to everything I say for it is never complete and there could be mistakes as English isn't my mother tongue and I sadly do not have all wisdom

 

[napoleonb]

Realizing I gave you no hints as to how to construct a barrel a little addendum.

If for some reason your barrel has to be decorated, structurally stiffened or strengthened make sure it is on the OUTSIDE only of a smooth and continuous bore. The breech should have more material around it because of the higher pressures, which drops towards the muzzle of the barrel. And preferably be screwed in. But make sure that by applying heat and or press fits the bore diameter doesn't change!

The screw-in breech can contain a smaller chamber than the bore diameter for the blackpowder. Giving more material and strength but a possible hazard when using to light a load or volume. Between charge and projectile there should be NO AIR or free space whatsoever!!!!!
(a possible solution is to use a filler of some sort, any fine grained stuff softer then your barrel will do e.g.. coffee, baking powder etc.)

The breech should be able to withstand the force in circumferential direction and should stop the barrel from moving (or in this case the breech from moving out of the barrel) A load positioned in a chamber in the breech tightens (by the force of the explosion) the connection making it a bit harder to be removed.

The trunnion leads all force to a carriage of some sort and should be sufficient in diameter not to shear off or bend. The attachment to the barrel is often done by boring in the side of the barrel and welding it together. As the trunnion is further from the combustion a reduced wall thickness of the cannon is permitted but still not preferred.

EDIT: perhaps I have to add a disclaimer to everything I say for it is never complete and there could be mistakes as English isn't my mother tongue and I sadly do not have all wisdom

 

[BronxFigs]

Thank you for all the added information. When constructing a cannon barrel, careful consideration should be given to the selected materials, or you will be making nothing but a fancy pipe-bomb, especially if you have no understanding about the differences between smokeless and black powders.

Only a total idiot would make and load one of these barrels without doing a lot of research on how to load and maintain one of these guns. Safety is always the first consideration when firing, and it is up to YOU to make sure no one can be hurt. A curious moron , or worse, a child, who walks in front of a muzzle as a charge goes off will be YOUR problem.

The first barrel that I made was cast in solid iron, then bored, and sleeved with a steel tube, for strength. Blank charges can be just as dangerous as the charges used for ball loads.

Sorry if this topic has now taken over a soldering/brazing thread. My original questions revolved around soldering and brazing techniques, and how they might be applied to this specific fabrication.

Someone who knows just a little about black powder cannons is actually the same as a total imbecile. Check: "Black Powder Cannons" on You-Tube for perfect illustrations of this penultimate sentence.

Frank

 

[BronxFigs]

A perfect tutorial about what not to do when shooting a black powder cannon....go to, You-Tube: "Black Powder Cannon the Coolest". A text book example of a very dangerous, and reckless dope. Notice how he hammers the powder and wadding....notice how close his face gets to the muzzle. His wife may become a widow, and worse, his little kids could be maimed by shrapnel if that barrel bursts.

Frank

 

[Entropy455]

Here’s the cannon I built. The barrel is constructed of 3” 1028 mild steel. The whole assembly weighs just under a ton. I do not fire projectiles. It's only for making a few big bangs on the fourth. It’s road-towable. There are no brazed joints on this cannon. . . .