The Shop > Metal Stuff
Sawed off cupola
awemawson:
Years back I had an oil fired furnace. A Morgan No. 5. The burner was simple in the extreme. I used a central heating circulating pump to push red diesel through a small jet (0.8mm if I remember correctly, but it was a long time ago. The air blower produced 150 inches water gauge pressure, and if tested running on the foundry floor had a habit of sucking up small bits of grit and embedding them in my ankles! - it was powered by a 2HP motor. Fan was a 'shrouded radial blade type' of about 28" diameter and 4" wide. Lighting consisted of dumping an oily rag into the pit having lit it, turning on the fan, heavily choked back (simple gate valve) and slowly opening the oil feed. Then it was a case of adjusting the oil and air just as you would the gas and air with a bunsen burner to get the right flame colour. Flame was maintained by the glowing furnace and crucible.
Had to stop using it when my neighbour sold the bottom of his garden and a house was built 10 foot from my foundry :(
vtsteam:
Wow, awemawson, that's heavy duty! Too bad about the neighbor. :(
I happened to have just about everything needed for a Kwiky style burner so I'm making one up right now. We'll see if it's man enough to do the job :dremel:
awemawson:
Mine was like this only slightly bigger and oil fired:
http://www.canfieldjoseph.com/foundry/furnaces/mms/gasoroilliftoutcruciblefurnace.pdf
Some useful data in that link
vtsteam:
Nice furnaces!
I guess mine would be about 1/4 the smallest capacity listed. Though I think the warm up time (from experience) is about the same -- you need an hour to get my furnace up to temp with its traditional refractory 4" thick lining.
Among other problems so far, I don't believe I've properly warmed up the furnace in my last few tries. I should plan on at least an hour of full blast to get the walls glowing. Once it is up to temperature, It will become more economical of fuel, and more than one melt would probably be a good idea once it's hot. It takes a long time to cool down afterwards. It just needs to be handled and thought of in a more old fashioned way. Particularly with charcoal.
vtsteam:
Small things completed on the furnace today - it threatened rain most of the day.
First, I drilled out the rivets holding the cupola tuyere plate on, and removed the tuyere. This will be held on with screws in future so I can substitute an oil burner here, now, yet convert back when operating as a cupola, which I still intend to do (and with charcoal.)
A couple problems re. this oil conversion presented themselves -- the tuyere hole is centered 7" above the bottom, and it is also directed 90 degrees to the bore. Ideally for an oil burner it would be near the bottom and directed tangentially to the bore.
I didn't want to put another hole in the casing and lining. It would be difficult to make a diagonal (tangential) hole through firebrick on edge without really tearing up the lining. Also I don't want additional holes to fill when used as a cupola. That inner surface and well need to be tight.
After thinking for awhile, I solved both tuyere position problems (I hope) by simply adding about 3" of sand to the bottom, and using a half fire brick oriented vertically as a plinth. The brick is located and oriented so that it acts as a deflecting vane to give a tangential swirl to the burner flame. The furnace is tall enough that raising the bottom and adding the brick puts the crucible right where it should be with clearance under the lid and supported just above the burner entry. So that looked good.
I also completed the burner jet -- several parts needed to be silver soldered. I then tested and adjusted the atomization of the burner jet with water, and briefly with waste oil @ 30 lbs of air pressure. No attempt at fire yet, but it draws oil very well and atomizes it. I'm confident it should flame.
I still need to locate the burner jet assembly into a pipe casing and then mount that to the furnace Also, connect the blower, which will probably be my small shop vac.
The only drawback I can see to this kind of oil burner is that it requires an air compressor as well as a blower. But mine is on wheels so not a big problem to bring to the site. There are simpler burners out there, but just thought I'd try this one.
I would really like to put the heat on tomorrow but we have 100% rain predicted tonight and tomorrow, as well as severe thunderstorm warnings. So it's unlikely I can.
I may make the 10" cupola extension ring tomorrow indoors, for use when I try to melt with charcoal again as a cupola.
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