The Shop > Metal Stuff
Sawed off cupola
vtsteam:
Here's an ark, of sorts, I built 22 years ago in Vermont. Took it 1700 miles down the coast and across the center of Florida. Lived aboard, off and on for 10 years in Florida and later Louisiana. Finally towed it back to Vermont, and used it as a base camp on land while building my present house.
Launch day, November 1991:
Interior:
Base camp ten years later back in VT, October 2001. Frost is on the field again.
vtsteam:
Tried the cupola on charcoal today. Even with the extension the charcoal burned down very quickly. A few minutes and it was down 18 inches. Melting was more thorough than last time but not good enough. The melt froze in the well -- never went completely fluid. I did have one small stream of metal start out the tap hole before freezing . \
Here I'm getting ready to chip out the blockage. I never did get to bod it off. The bod rods are at the ready in the cinderblock in this picture, and the ladle is heating on top of the cupola. The flame had been impressive out the top, but by the time this picture was taken it had died down as the cupola had burned most of its fuel.
I did try a second charge after refilling with charcoal, but had no better results. In the end I dropped the bottom and chiseled the slag off the barrel.
vtsteam:
When the cupola cooled off enough to remove the extension, I pulled the tuyeres off, plugged up the far one with bod mix on the inside, remade the bottom, installed the new oil burner, and the plinth. Brought up the compressor, the oil and kerosene, and tried an oil burn. Figured I might as well try to fill the mold I'd made while the main furnace body was still hot.
But, no luck there, either. The new burner had an air leak in a silver solder joint, so wouldn't draw the fuel. Just bubbled in the container.
So I took the burner apart cleaned it and re-brazed it. Took two tries to finally get rid of the leak. Tried it again, and it seemed to work, but wasn't drawing fuel as well as the first one had. Not sure why -- maybe there is a blockage in the jet. There was definitely enough draw for kero, but waste oil draw was weak.
I probably could have melted with kerosene, but it was getting late and general discouragement was taking over. Decided to just put everything away and call it a day. :(
vtsteam:
I think I'm going to stop the charcoal cupola experiments for awhile and just melt iron with oil.
My feeling about the charcoal side of things is that it would really need a much larger bore for increasing the heat available to a single charge. You really can't just go upwards -- most cupolas fit several charges in a taller height. That wouldn't work here. You basically need more charcoal between each charge, and the only way to do that is to increase bore.
I think mine might have worked with a much smaller charge than the 6 pounds (x 2) I tried. Maybe 2 or 3 pounds. But then the well is far too large for that quantity (7" dia x 8" high) so it wouldn't be hot enough to keep it fluid.
I'd say that to successfully melt iron with charcoal -- in usable quantity -- I would want something about a foot in bore diameter, minimum, whether a crucible furnace or cupola. The well on a cupola would be short -- the tuyeres much lower than in coke melting practice, and a higher bed height.
I don't think my 7" cupola is going to work with charcoal therefore -- maybe with 2 pounds of iron it might, but that's a lot of work both in construction, pour preparation, and fuel making for such a small quantity of metal. And I bet it would pour cold.
I'm pretty certain it would work with coke, and it is proven as a crucible iron furnace with oil. Aluminum and the copper metals should be doable with charcoal. Or propane.
I'm pretty much "burned out" on furnace experimentation and construction at this point -- other than finishing up the oil burner tank and piping.
Maybe in the fall I may try a short big bore charcoal iron crucible furnace using a half 55 gallon drum -- I would still like to melt iron with charcoal at some point, but I think my cupola days are over.
Rob.Wilson:
Hi Steve ,
Dont be too disheartened , It was a valiant effort too try and get a charcoal fired cupola to melt iron,no one could have done more . :bow: :bow: :bow: , Step back ,take a break, you have been at this project for a wile now , spend a bit time on another project :dremel:
At the end of the day you still have a very capable oil fired furnace :)
Rob
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