Casting A Cannon Is A Lot Harder Than You Think

We’ve seen backyard casting, and for the most part, we know what’s going on. You make a frame out of plywood or two by fours, get some sand, pack it down, and very carefully make a mold around a pattern. This is something else entirely. [FarmCraft101] is casting a bronze cannon. Sure, it’s scaled down a bit, but this is the very limit of what sanity would dictate a single person can cast out of molten metal.

This attempt at casting a cannon is more or less what you would expect from a backyard bronze casting experiment. There’s a wooden flask and a greensand mold, everything is tamped down well and there’s a liberal coating of talcum powder inside. This is a large casting, though, and this presented a problem: during the pour, the halves of the flask were only held together with a few c-clamps. This ended poorly, with molten bronze pushing against the mold and eventually flowing onto the garage floor. Doing this alone was perhaps a bad idea.

The failure of the mold meant some math was necessary, and after some quick calculations it was found that more than 300 pounds pushing the sides of the mold apart. A second pour, with the sides of the flask bound together with nylon straps, was much more successful with a good looking bronze cannon ready for some abuse with a wire wheel.

This is only the first video in the series, with the next videos covering the machining and boring out of the barrel. That’s some serious craft right there.

23 thoughts on “Casting A Cannon Is A Lot Harder Than You Think

  1. As a foundry person, your defect was definitely air. You need a couple vents on the end to let air escape. Green sand is porous but not enough to let that much air out.

  2. I’ve been watching this series since he started it and was actually able to leave the first comment when he posted it! Go me!

    Anyway… loving this series, learning a ton and enjoying FC101.

    There’s a whole ton of people on YouTube doing the canon casting each with a different approach… it’s been REALLY cool to watch each team take a different path for different reasons…

  3. This is not the first video in the series, he’s been working on it for a while, figuring out the right mix of metals, testing small pours, etc. He’s failed brilliantly a number of times and there’s always something learned from each failure. I highly recommend watching all the videos about his cannon project

  4. I have assisted a professional artisanal iron casting crew of artists at Carrie Blast Furnace in Pittsburgh several times, and they taught me how to make sand molds for casting.

    I learned first-hand how catastrophically tall long molds can explode at the base from the sheer pressure of the iron pouring down into a tall mold of only 4 feet high. It was an art piece shaped like a Constantin brancusi wing and it was a narrow mold, and the Caster had experience but it needed to be held together with more bands of steel strapping, and it didn’t have any air vents from what I remember because the Caster did not want sprues projecting from the cast piece surfaces.

    The mold took maybe only 150 lb of iron if that but it exploded at the bottom because the iron had a four foot drop into a void with no vents and no support around the exterior of the mold. We basically had a volcano of iron explode at our feet in the middle of trying to control a Gantry crane with a crucible of several hundred pounds of molten iron, and had to jump out of the way before our feet caught on fire.

    Moral of the story- vent your molds appropriately, be careful of using knife gate vents on a tall pour spraying the iron inside the mold instead of letting it flow, and absolutely use as much wooden box and iron banding around your mode if it is tall as possible or your mold will explode regardless of the weight of the metal.

  5. It doesn’t matter how experienced he is, or how many times he’s poured before, but standing with one foot balanced on a brick whilst pouring a heavy crucible of molten metal is mind-bogglingly downright foolish. Even more so that his soles are wet from the rain and the lower foot appears not to be flat on the floor. It is essential shop practice that safety always comes first!

  6. Sigh, he was incredibly lucky he did not get seriously burned doing this. Never pour over concrete, that spalling that happened when it spilled could have thrown molten metal all over him and the surrounding area burning him and causing a fire. He talks about it in the video and he is dead wrong. Even “dry” concrete has a significant amount of moisture in it. The spalling proved that.

    “I think people overstate the danger a bit” No, they dont, I have known people that got severely burned from this.

    1. “Even “dry” concrete has a significant amount of moisture in it. The spalling proved that.”

      You should mention, that no matter how much you dry your concrete it will still contain water, because that water is part of concrete. When you subject concrete to high temperatures (like with molten iron), it decomposes releasing water vapor.

    2. I now wear a face shield over my safety glasses when casting, exactly because of having concrete explode and shoot hot aluminum at me. (I also no longer cast on concrete.)

  7. I don’t want to seem to critical, but the safety in this video is appalling. In a vertical mold with that much molten bronze he could have easily make a molten bronze fountain.

    1. Don’t cast on a cement surface.

    2. Wait until it is not raining and do it outside rather than a garage full of flammable items. Watch the video, there are oil containers within a few feet of the mold. You need ventilation especially if you are adding zinc to the mix.

    3. Safety gear, buy a nomex hood, wear a leather jacket, tuck your gloves into the jacket so that molten metal can’t get in the cuff and inside. The aluminized stuff isn’t really necessary at this level since the shiny aluminum coating is really for radiant heat.

    4. Get a two person tools for the lifting tongs and poring shank. That is too much metal to pour with single person tools.

    5. Get a few fire bricks and have a safe place to set the crucible if something goes wrong.

    1. Steve, your first point should have given the solution to the problem just as your following points do.
      Never cast on a wet or damp surface, concrete and cement are always damp, kiln dried sand is as good as it gets for casting on.

  8. Im still surprised there was no “domestic fallout” from the molten garage floor blowout…my wife would never let me melt or pour anywhere near the house again!

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