OK -- Yeah, I agree, pin and weld the plug. That's the standard protocol. You'll get no argument from me on here on that one.
I'm shooting blanks 99.99% of the time. Not really interested in shooting projectiles.
It's "tubing" -- 3/4" wall on 1" dia. tube. Drawn over mandrel, so it's "forged" and not "cast." No seams, no welds. And it's a steel alloy, although I have no sort of data on what sort of alloy. I swap the terms "tube" and "pipe" a lot. It's not my field.
The plug runs in the breech 2" -- You can see the touch-hole in the photos. The touch-hole sits at the edge of the breech plug. The formula for plug dia. and driving the plug into the breech was provided by a certified structural engineer. There's literally a "weld" on the molecular plane between the plug and the breech.
Trust me on this one. We didn't just "guesstimate" on the dimensions and fitting of the breech plug.
500 gr. charge Fg. That's a BLANK charge. Three to six squares of TP over the powder. The tube is 12" -- less 2" for the plug, less 2" for the charge and wad. So, 8" run on a 1" tube. All the "poop" from the boom shoots out the front end.
There's no "back pressure" to speak of. 3/4" forged wall is going to manage the pressure in any case. We've run cyrogenic and X ray structural analysis on a similar prototype with much, heavier loads (Like 1200 gr. and a half pound column of lead ball.) No strain on the tube, no stress on the breech plug.
DON'T TRY THIS AT HOME! -- We have a structural engineer and some testing facilities to play with on this cannon. Certified structural engineer testing lab, with a certified structural engineer running the show.
I rarely shoot this with a projectile. When I do shoot a projectile, it's a 1" dia. lead ball, and about 200 gr. Fg.
And we don't stand around while the fuse is burning.
-------------------------
Unfortunately, the old carriage got sacrificed to the "Salvage Gods."
I'm looking for a larger cannon. Cannon Mania has some decent looking tubes, but I'm not impressed with their carriages. I just don't like their proportions.
I may buy one of their tubes and then build my own carriage -- but I'm barely set up for carriage production.
This guy from LandFallNavigation sort of appeals, but I'd really like to see something with a tube in the 2" bore range and about 24" length.
http://www.landfallnavigation.com/mbpc1.htmlI'd be willing to run $2,500 on a decent cannon, pre-finished kit would be ideal.