Dirt cheap refractory.& big aluminum furnace ideals

[Fred Beagle]

Ok here's my little forge/furnace that I melt small amounts of aluminum in. And as you can see it only does a small amount. And here's the new furnace and old propane tank I had got off an old man who had pretty much butchered the tank so it is what it is and hopefully someday this new furnace will allow me to take whole small engines/2 stroke engines,Car engine heads and allow me to melt them without having to break them down into smaller pieces. All my forges/furnaces burn raw wood with air blast from squirrel cage fans. I do have a propane burner but I live way off the country and fire wood and scrap wood is abundant. I also have some commercial grade fire bricks but they are rather expensive and I when I make my refractory for my forges it usually goes something like this one part sand ,one part portland cement ,one part fire clay. I'll get back to these in a minute.

A few more thoughts on the big furnace is this: There will be a hot water heater tank as a big crucible and there will be a down spot with a mud valve for pouring during the melting process.

The inner crucible will have big steel pins that lock it into place so it doesn't move around during the firing and mid way up there will be a serious grating bars that  the Hot water heater tank ~"Inner crucible"sits on as well. On the outside of the  main tank there will be a swing arm that removes the heavy  inner crucible but it's just for dumping out the crucible when everything has cooled the following day. and this is what the upper door in the tank will facilitate. It will allow me to take out the inner tank to dump it and I will have to allow for the drain pipe and both these doors will get a serious amount of refractory/fire bricks on them as well

The lower door is the fire box door and it's where I'll be loading wood in and I'll have to turn off the fan before I open this door or it will be Nebuchadnezzar and the three amigos revisited! Yikes

Now the very top will have a removable donut type insulated hinged heavy steel plate lid that lets out the smoke and fumes and I can skim off the slag as well out of the crucible as well.

Other things I will probably get is a ceramic blanket to wrap around the inner crucible as well to help retain the heat.

Now here's my question and it's probably going to sound crazy as I try to go cheapest way possible as usual. But I was thinking of instead of lining out this big tank with high dollar fire bricks why not either use old Red clay bricks like they would use in an old style pizza oven. Or go 3rd world even and make mud bricks "dirt" and use that instead. I mean I expect it to crack and break any how. Why do we want to spend hundreds of dollars on a commercial insulation that's rating up to 3000 degrees F or higher when all we really need is to get it to about 1200 degrees F for aluminum. Oh it would be cool to be able to throw a waste oil burner in it and melt something like brass... But I'd have to get a graphite crucible and total rework the pouring aspect as well.

But yeah I was thinking either home made dirt bricks or line it with red bricks and then plaster that with fire clay. Of course this things gonna weigh a ton but I think it will be a fun project. Now tell me what am I missing that I've not thought of. I'm just soliciting opinions before I get serious with this project. Hey it may be spending a couple of hundred dollars is the best way to go.