I built this furnace about 15 years ago. I've only used it a couple of times. I had high hopes to do some large castings, 20 to 40 pounds of Bronze or Cast Iron. I mainly do castings. Most of them are about 5 pounds or less. I have worked with some groups doing Iron smelting and have some plans to do some steel making and wootz.
I designed this furnace with a small ring at the bottom to allow an area where the gas or oil could fully ignite before heading to the top and exit. Trying to keep the heat in the furnace longer without restricting the flow. I just cut a pool noodle in half and cast the refractory around it.
I cast the bottom solid and then the section over to Tuyere and the noodle with some insulation in the mix. The lining of the furnace is made by pouring refractory between 2 sections of stove pipe with the wall being about an inch. Then I put on the outer shell and packed it with ceramic blanket. Capped off the top and poured the lid with a 4-inch exhaust.
It heats quickly and gets very hot. I've used Propane or used motor oil, both heated really well. I've melted Iron with propane. Well, only because my blower quit working with oil, and I had to switch to gas to finish the melt.
I have built 3 other furnaces. One failed after a couple melts. The second one is holding up well and I use it for casting and turn it on its side to use as a forge. The third one is a small well insulated furnace to make steel pucks or cast small amount of Bronze or cast iron. I would like to build a small one with the donut at the bottom to see if it would work as well as the larger one.
Materials for Big Boy: 30 gallon water tank, 2 stove pipes, 7 and 9 inch, 1 of my son's pool noodles, Refractory, Mt Savage Heatcrete 3100 (Great Stuff!), Ceramic Blanket I found in an old foundry, now I would use Kaowool, Plus a few other odds and ends I found in the old foundry... With Permission!
More pictures coming.
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