When I first saw this unusual cannon about seven or eight years ago in an old Victorian-era photo, it was located out in the elements, in a sea-side square location, surrounded by ladies and gentlemen in turn-of-the-century garb. The first thought I had about it was, "How in the world did they ever cast that length of tube?". At first, I thought it must have been cast horizontally, because I thought the bronze would certainly start to 'freeze' before it could reach the breech area of that extra-long cannon. I knew very little about pouring heat, chaplets and sand cores back then.
Now, I am solidly in the vertical-pour camp. Dan's comments about the lack of survivability of a sand core that long, made me think, though. I am betting that they would cast this tube vertically mainly because of the extra complexity of casting it horizontally. Think of how many chaplets you would need to support a core of that weight. Also, you would need a bunch going up into the cope too, as the extreme difference in the density of bronze versus the clay, wood and sand of the core would cause the core to
'float'as the bronze filled the mold cavity. Further, and perhaps fatal complications, would come from the multiple risers needed to feed a mold this long from a central reservoir. If just one of these risers froze, it would cause a complete casting failure.
The core would, of course, have to be very strongly built, especially in the lower section, perhaps using more fired clay as an insulator over a solid timber inner core or a combination of sand and timber of increased insulation and still having the requisite strength.
Sure, the pit would be deep, but they knew how to dig huge footings for those enormous cathedrals back then, and water wells too, so a deep, solitary, hole was really not much of a challenge. One thing is absolutely known here. The weight of all that metal would certainly help fill out all those details in the breech and cascable area shown in the pic below.
Mike and Tracy
