Join Date: Mar 2006
Location: CSA Consulate, Rm. 101, Glos. UK: p.s. - Real Dogs Have Feathering.
I suspect, (from the video I posted above), that it was a casting flaw. Cooling a casting from the outside in makes the inside softer and changes the crystalline structure. Failure can occur early in it's life, or later after wear. Cannons were apparently NOT proof fired with a large charge.
The iron clad ship: Note the thickness of the gun-port covers. I've been on the HMS Warrior here, the UK's first iron hulled ironclad (after, they built a few for the Southern States navy) - equally thick shutters but the ironclad hull was a lot thicker. constructed from 4 ½ inch thick wrought iron plates bolted to 18" inches of teak, then mounted on the 1 inch thick plating of the hull itself, behind which were the frames and timber lining. In all this represented a total thickness of some 2 feet.