In this article I will go through the process I used to make my field artillery type Black Powder Cannon. I built this back in high school in wood and metals shop. Unfortunately I do not think any school would ever let a student build any thing like this at all today. I built mine in 1973, so it has been around for awhile.
First thing you should do is either make or buy a barrel. Make sure that there is plenty of metal on the walls back where the charge sits. Mine is 2 3/8″ thick at the back and tapers down to 11/2 inches at the muzzle. It has a 1 1/8″ bore leaving 5/8″ on a side. Also either use 4140 or similar steel. This is stronger than 1008/1010 type steel. This is the main focus of your Black Powder cannon.
My barrel is 11 inches long, and the trunnions are welded in the middle at 5 ½ inches. The bore is 1 1/8 inches with a 1/8 inch touch hole. As you can see by the picture the taper job done was by hand. I did not get to use a lathe with a taper attachment, and computer numeric control ( CNC ) was still just starting out then. If you buy a barrel, make sure it is made of good steel. In reality 1008/1010 will work if you have a good wall thickness at the breach. But I always try to be very safe.
Once you have you barrel you can start to lay out your carriage size. To do this you can get on the Internet and look at pictures of the type you would like to build. Then you can just scale it to the size you need for your Black Powder Cannon. To make the main beam, I glued 6 – ¾ inch thick Poplar wood boards together. Grain will run with the length of the carriage. The two outside boards were the hight I needed for mounting the trunnions. All other inside boards were only the thickness I wanted at the point for mounting the barrel and wheels. After the glue was dry, I band sawed the carriage to the shape and size I needed.
How I made mine here was to glue 2 – ½ inch thick Poplar wood boards together with their grain going in opposite directions. This gives them strength. I laid out spokes and cut the scrap areas out using a scroll saw. Then drilled the axle hole 3/8 inches.
Putting it All Together
To mount the axle, I took a 1 inch by 1 inch piece of Poplar and split it on a table saw. Then I cut a channel in each half so the 3/8 inch axle would slip through it. I sawed a channel in the carriage to set this axle mount in. I glued it so both haves are mounted permanently.
I laid out my trunnions and drilled them by clamping and piece of scrap wood on top of the carriage. I ran long wood screws from the bottom to the top of the carriage. I did this in front and in behind the slots were the trunnions would set in. This will reinforce the wood were the barrel mounts.
To mount the barrel I used copper strips with wood screws. You might want to use steel with wood screws instead. The copper has a tendency to stretch out after firing. Steel will not do this. To mount the wheels I drilled each end and used pins. After you get every thing mounted and are happy with the fits you can take it apart to stain and finish. I used copper on the wheels and tail of the carriage.
To Fire Your Cannon
With the barrel size I have, I use 200 to 250 grains of 2F (FF) black powder. I only will use aluminum foil to hold the powder in place. I do tamp it down real good though. If you use news paper, be careful of starting fires with the smoldering paper. Do not put any kind of projectile on top of your powder. First it will made the recoil be very violent. Your cannon would go fling back. Mine with just foil will roll back 12 inches or more in grass. Also if you shoot a projectile and it does damage to property or even worse hits someone, you will be in big trouble with the law. Always be safe.
If you would like to see more pictures of this cannon you can go to Black Powder Gun . You will also find some of my other black powder fire arms there.