DIY Foundry Crucible Furnace




What do you think about this video?

WetCigar: Excellent design, construction, successful completion and choice of music. Well done!

Ron Yerke: Wow, tou sure have a lot of good features built into that furnace. The only things missing are lockable casters, and a way to limit how far the lid swings (minor niceties). Excellent work! :-)

Shai Winzer: How would you explain, how you made the lid lift? does that certain lift have a name?

Kamal AL-Hinai: kick-ass furnace for a first timer ;)

Kamal AL-Hinai: awesome song, i've heard it before, i just don't know where.

SonicScooter: Why the crap music, why not some commentary.?

Potatoe Spudstein: this is pretty amazing, but does it not leak heat without mortar or something?

JOEL T. Ross: Will you share your drawings?

Mark Vyvoda: can I buy one of the burners please? I am building a small mobile foundry now and am in need. thx

F De Mascio: Nice design and build. At least half the enjoyment of this furnace has got to be knowing you crafted it.

Johnny Bravo: Couldn't concentrate on the video because I wanted to break out into singing. Nice build tho

Abel Tripoli: Great crucible with lovely music! What`s the max temperature out of that F16 turbine?

Sean Hirsch: WOW.
I am glad I ran across your video.
Did you build the torch or did you buy it?

Christopher Jones: ugh Queen... I could thumbs down easily just for the music alone... but i wont because this is a sweet foundry and good video demoing how you did it. Thanks for sharing.

Aaron S: I can't watch the video. I'm sure the information and the content is very helpful. But music is a distraction and annoying while trying to read. Idk if it bothers anyone else, but immediately stopped watching and looked for mother video.

Kim Kimsen: You call that a burner??I call it a F36 Hornet...oh thats nice.

Linda Mvungi: Hello! Can you give us a link for the plans for the lifts?

Tim Bradbrook: Very nice build. I had something similar in mind for my next one.
I see your upload was in 2010. How is she holding up?

cfjulian1225: Many of the things you do are correct, however, one major mistake in the construction of this furnace is the lack of a bust out hole 270 degrees from the burner. If you are melting metal, a common problem is that after a while the crucible gets old and sometimes will catastrophically fail. When that metal dumps into the bottom of the furnace, it can snuff out the flame but the hot metal will then reignite it. Foundries have burned down as a result of this kind of explosion and people have been either killed or seriously burned. The solution that all professional furnace builders use, is a hole 270 degrees from the input hole, that is at the very bottom of the furnace. In a catastrophic failure, the metal has a place to come out, therefore, it doesn't snuff the burner (it also make cleaning the furnace a lot easier after a bust out). On a furnace this size, that bust out hole should be at least 2" in diameter. It is OK for some flame to go out that hole. It keeps it hot so that molten metal does not freeze in the hole and plug it in a bust out situation. Below that hole, you want a container full of dry sand. If metal flows into dry sand, it will not pop and is easy to cleanup. If you dump it on your patio bricks, the moisture in the bricks or just the uneven heating of the bricks can cause the metal to fly as the concrete pops. It typically happens after the metal has set on a concrete surface for around a minute. The design that you have for a lift out furnace is OK. One of the things that most operators do is put a thin sheet of fiberglass under the crucible and paint that fiberglass with graphite. That keeps the glaze of the crucible from sticking the crucible down to the pedestal block, assuming you are using a clay/graphite crucible with glaze on it. If you run this furnace a lot, coat the inside of the furnace with Kyanite cement or some other refractory that can be pasted onto the surface. Your castable is only going to be good for around 2000 degrees, 3000 is you buy the expensive stuff. Continual use will wear the face down and the uneven surface will reduce furnace efficiency and damage the crucible. I did not see the relationship of the crucible to the burner. Generally, it is a bad idea to allow the flame from the burner to directly hit the crucible. You want the crucible high enough off the bottom so that the flame hits the furnace wall and then spirals up the wall, giving an even heat and not burning the bottom of the crucible. I always build my furnaces with the burner hole a bit larger than the burner and then pull the burner back so that it just barely goes into the hole. They last much longer that way and are easier to light. Never start a furnace out on high flame. You want to start on a relatively low flame for the first 5 to 10 minutes. You can increase the flame as time goes on. Listening to the flame and the rumbling it makes will tell you if you are running too hard early on. A deep rumble means that the coolness of the wall is causing an incomplete burn. This releases a lot of carbon monoxide and it represents a condition where you can blow out the furnace momentarily then reignite it. That can easily throw the lid right off your furnace if enough gas got in before it reignited. I have built and run these things professionally for 40 years. I'd rather you didn't get yourself hurt.

Cert: Building stuff is always in my family gene. My dad is a new york auto technician and taught me everything I need to know about cars. Now I sell car parts online to suppliment my income. So it does help when there's good guidance.
Rating:
DIY foundry crucible furnace 5 out of 5

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