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French 36 Pounder
Pat:
Now for the second question.
No, they didn't file off the casting seam because there wasn't a casting seam in the first place.
AFAIK, the guns were not cast using re-usable molds but by using a form of casting similar to the 'lost wax' method. This was because the sheer size of the casting and the heat of such a large mass of metal made it difficult to handle and would ruin a mold too quickly to make it of use.
In the lost wax method, they first make a 'cannon' out of wax formed around either wood or straw to make the bore. This wax gun is smoothed and shaped as desired, with any ciphers or flourishes (like that on top of Ernest's gun) cut or pressed on top. After the wax hardens, they coat it with clay or plaster, with straws insterted to provide air release and drains for molten metal.
When the mold hardened, they heated it up over a fire and the wax melted and ran out, leaving a holoow vessel with the inside the shape of the gun.
Most cannons were made out of iron, but the very best cannons were made out of brass because they were more accurate.
Then they poured in the molten metal, and as soon as it was thought to be cool enough to hold it's shape, they'd immerse it in water, which would cause the plaster mold to shatter.
If you look closely at old cannons, you'll see that the sides aren't smooth, but failry rough because of this process, which left no seams but also didn't look like anything a lathe would do.
At this point though, the inside of the bore was also failry rough and wasn't always straight.
there were a couple of methods to drill it out (which is why they called it the "bore", but one of the easiest to explain is when they suspended the barrel over top of long auger by tying a rope around the cascabel (the round ball at the end of the breech) and then using block and tackle, raised it striaght up on sheerlegs.
They turned the auger either by use of a waterwheel mechanism or more frequently, horses or oxen, while the block and tackle was slowly let out and the weight of the cannon itself drove it down over the auger.
This produced a straight hole in the barrel of the correct diameter, with no rifling (which is why they were called 'smooth-bores').
The two longest parts of the process were letting the raw casting cool down enough to work, and the length of time it took to drill out the bore.
It's amazing how much weight they could lift with this methodof blocks on sheerlegs, but that was how they raised the masts to fit in and how they loaded the guns on the ship after launching. Also in some of the stories I've read (for instance "Diamond Rock" where the Brits took the guns off a warship and raised them up the side of a high cliff on an island overlooking a straight in the Caribbean that they knew French fleet would have to sail through. The French couldn't even elevate their guns to shoot back. It might be where the idea for "Guns of Navarone" came from.)
billp51d:
Hi Pat...In addition when it was finally realized that smooth bores had little control over the trajectory they developed the newer "bullet" shaped round. This lead to modern rifling. This is a interesting process also, as is the old method of lowering a cannon onto the auger. If you ever viewed the bore of of a 16" gun and wondered "how the hell did did they put all those grooves (rifling) in the bore ? It's and interesting and simple process. A broaching tool is pulled through the bore from the breech to the opposite end with a long cable thus cutting and forming the rifling itself. I learned this from an old navy yard machinist when I started my own trade "longer ago then I care to remember". ::) Thanks, though for the info on smoothbores..
Cheers/Regards, Bill
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