Cannonballs

[PeteH]

Actually, shells.

The question came up on another forum I follow: How did they cast hollow spherical cannon shells, back in the 1700-1800s ? Obviously they'd use a regular sand mould, but how'd they get the hollow ?

One poster said they used a wooden peg wrapped in string that then was coated in clay; the peg fitting into a recess in the bottom of the mould. After casting, the peg was pulled out of the shell, the string pulled out, and the clay residue rinsed out.

Seems a bit unlikely, since the temperature would be high enough to fry the string, even with a layer of clay over it.

So... HOWDEYDOIT ??

[hammermill]

the ball inside a mold on a post will work fine. into todays world I would use waterglass to make my sand insert.
as it was invented/discovered in the 1600,s it may well have been used for mold making back then.


string back then would more than likely be hemp or leather. but then again even using clay and a iron probe to crumble the clay inside the ball would be doable.

[steamin10]

Ya, and horse manure with sand added and pressed out in wooden carved ball molds. The mostly dried balls would sit on a stick and the mold closed up. The problem was to overcome floating of the core. The hole in the hollow ball was used for the slow fuse of nitrated paper, that would ignite on firing the cannon shell. Earlier mortor shells were of the 'bomb' type that had a timed fuse. The Grenadier would light the fuse, and time so many seconds to light the main charge with a slow match, so the 'bomb' would go off in the air for maximum effect. The cannon balls had a paper fuse was that marked, and punched with a cannon prick, to set the delay time. Exploding round shot took over for hard shot and grape loads. (Canister, was a tin can shot shell. Canister was fired directly in front of approaching troops, to glance off the ground, and break the load apart into a devastating swath of projectiles). Hollywood's visual interpretations are wrong, on the way things really worked. Great gouts of dirt were thrown from furrows cut in the ground by direct fire cannon shot, dismembering anything in its path. Exploding cannon shot were low and high elevation rounds meant to explode in the air to pelt whatever was beyond with high speed fragments. Such shot buried in the ground from high angles, were a waste, as the blast and shrapnel were forced upward and caused little damage except for the spirit and nerves of the shelled troops. Dependable contact fuses were not available until the 1880's-90's, with shaped shells.

The wound rope method was used in many applications, where a hollow was needed, from cast kettle with spouts, to iron 'bean pot' types of castings. Non baking muds and clays were used for the finish with flour or sugar based glues (sorghum) that decayed with the heat. Some water and a few pebbles made for a good cleaner inside. Much of the rope was able to be reused, as the clays and fillers insulated the rope from much of the heat. It was important to not bake a clay into brick, inside a casting. Horse manure was an important and cheap material for centuries in bronze and iron casting.

'Ropes', are mentioned, but could be of common cording, that could be hemp, waste flax, linen or cotton cloth (rag) twisted in strips and dipped in muds and squeezed out by hand in the winding and forming. Large cores could be formed by tied straw, that would promote venting, a problem in heavy castings.

[hammermill]

so for a first step you need a horse, oats and grass hay, so assembly required.

[steamin10]

Yep. It worked for many hundreds of years in casting items like swords, points, horse bits. The Chinese used blast furnaces to smelt tin and copper ores, in no more than a clay pit and a bellows. One example of horse bits found at a site cast a dozen at a time with clay pottery finger molds stacked together. Production in a highly skilled and protected art.