The Shop > Metal Stuff
Sawed off cupola
vtsteam:
I removed the charcoal from the bottom. Lining is perfect. No puddle of iron. But a fair number of frozen droplets mixed in ith the bottom charcoal. Here's all the metal removed from the furnace, arranged by melting range. Sifting this stuff out feels a little like an archaeological dig. :borg:
awemawson:
So you were close in temperature but not quite high enough. Either not enough air or possibly too much air over cooling the burn. I suspect the former as you have unburnt charcoal left. Did you get white sparks out of the top or only orange? Many cupola designs pre- heat the blast air using heat lost in the walls.
vtsteam:
Thanks awemawson. Air might have been a factor but the biggest problem was not enough fuel height -- at least that's what I think.
The charge burned through in at most a couple minutes. Didn't time it, but should be more like 5-10 minutes for the iron to drop through.
I measured the furnace and the 2" tuyere is centered 7" above the sand floor, and 11" below the top of the furnace barrel.
So that's only an 11" bed height. From readings, a lidded cupola furnace can get away with a shorter bed height. That may be true, but how much shorter? and charcoal would seem to require a higher bed height normally. So I think it might have worked with either coke, or more bed height.
So, options:
1.) I have a nice strip 10" x 48" of clean steel sheet that I can bend into a furnace extension. That would give me 21" of bed height as opposed to the present 11". It will be less of a "sawed off cupola" however, and I will have to modify the lid lifting mechanism as well as make the new extension. The space for a drop may now be insufficient under the furnace, but I suppose I could raise it on blocks, and or trench a little under it.
2.) I could make an oil burner pretty easily and run it as a waste oil crucible furnace, with no other modifications.
3.) I do not think this furnace will work as a charcoal crucible iron melter -- though I could still try that. But I believe that would require a bigger bore to seat more fuel around the crucible. My crucibles are about 5" in diameter, and with a 7 " bore, most of the charcoal would have to be sitting on top of the crucible, and wouldn't drop past it. A plinth would also block fuel. Wish I'd made the bore larger -- that would have helped the cupola mode as well, I think. I don't know if crucibles are ever set floating, to drop with the fuel -- that would be the only possibility I think, of melting iron with charcoal in a crucible in this furnace.
Rob.Wilson:
So close Steve :(
Stick with it I no you will crack it :thumbup: ,,,,,,,,,,, at least you have had iron and fuel in yours unlike yours truly :palm:
Rob
vtsteam:
Thanks Rob!! I'll keep going. But I'm starting to lean toward oil, just to see some liquid iron without doing another week of work. Feel like that's cheating, but I can always make the charcoal cupola extension, too.
It has also been threatening rain off and on all day -- rained last night. So out of a mixture of curiosity mixed with frustration at the weather, I thought I'd try a quick crucible run with my remaining charcoal and about 2 lbs of iron pieces. It seemed to me that I had more crucible side clearance than I'd remembered. So maybe it would work.
I made a top for the crucible out of sand/fire clay mix -- a patty. I put the iron pieces in the crucible, sprinkled in a small amount of sodium carbonate (aka soda ash, aka washing soda) and filled the crucible to the rim with charcoal pieces and covered with the top.
Then I lit the furnace with about 1/4 full charcoal, applied light blast to get it going, added more charcoal, more blast, etc until almost full. Then added the crucible and surrounded and covered that with charcoal.
Then I put the furnace cover down, applied blast, and after about ten minutes the crucible had dropped to the plinth. I then re-filled with charcoal, applied blast. When that burned down, I then re-filled with charcoal and applied blast. So charcoal three times total. Time was about 30 minutes from start.
The crucible was glowing orange in the furnace. I maneuvered the top off, and the internal charcoal was also bright orange. Couldn't see past that. I pulled the crucible out of the furnace and simply poured the contents out into the ingot mold.
Unfortunately it was just bright orange pieces of iron. No melting, but close, I think. If I hadn't run out of charcoal, a 4th or 5th round might have done it. The furnace did have to start from cold, and it does take an hour to heat the walls up. This was only a half hour, and the walls above the halfway mark weren't glowing. Normally with more time I pre-heat with a wood fire.
I'm pretty sure if it had been bronze it would have been molten even now, so I guess the crucible side of things still has possibilities.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version