Metal Casting Zone

OK so I got the molten metal bug. So now I am building the first furnace. I am using an old well pressure tank since it already has legs on it, easiter to mount wheels. I am looking for the cubic inch weight of aluminum so that I know how large of a crucible to get to do the largest pour that I can imagine do ing here with out breaking the bank. The well tank is two feet across before I have put refractory in it. I was thinking of a 10-12 inch bore. That should give me more thank six inches of refractory on the outsides. Too much? ... such a thing as too much? Burning waste oil al-la olivers labs so that cast iron is in my future. any hints or warnings before I mix the rocks?

you have it about right. how high is it????? a peice of 4 inch pipe 6 to 7 inches high holds about 2.3 kg of aluminium (5 to 6 pounds.) you could go bigger than that but remember you have to be able to pour it!!! a idea of what you want to cast would be helpful as you dont want to melt more than you need. its like this.... you can melt a couple of pounds with ease but when you get into bigger volumes it consumes more heat and needs more heat to stay molten. its very much linked to the power of your burner.

aluminum is 165 lbs per cubic foot. a little under .1 lb per cubic inch.

My big furnace has a 12" bore. My casing is an old smoker grill, I have about 3" of refractory. My largest crucible is about an A20-25 (not exactly sure, got it off e-bay) and that is about as big as I want to handle by myself, and I am not a small guy. That is aluminum, by the by, I wouldn't handle that much brass or iron by myself. Unless you have nearly free refractory, 6" is a lot. What you can do, however, is make the outer 3" or so a portland/sand/perlite mix, just to take up some space. That is also a LOT of thermal mass to heat up, and the only practical way of heating it up would be a WO burner. If you were using it constantly so it never cooled down it wouldn't be a problem, but just for that one-off weekend pour it will take forever to get to melting temp. Insulating characteristics of the refractory are very important.

aonemarine wrote:
aluminum is 165 lbs per cubic foot. a little under .1 lb per cubic inch.: ????????????isnt this the specs for brass?????my ice cream bowl that i store by ingots in is close to a cubic foot more or less! it stores about 10 to 12 kg of aluminium. there is some small space between ingots so i would estimate it at about 15 kg molten ( 30 to 35 ibs per cubic foot) a cubic foot of aluminium would take a bit to melt! i wouldnt like to have to cut it up by hand for the pot!!lol lol

brass, cast 534 lbs per cubic ft. 1 cubic ft= 12" x 12" x 12"
Im assuming my data is correct.......

...Im a bit confused. I thought that refractory WAS an insulator that kept the heat inside the furnace. Like house insulation... the more the merrier? If that is not the case then Ill happily scale back as it will be cheaper and dealing with the lovely holder of the household checkbook will be a bit easier. I was going to use the sand/pearlite/fireclay mixture as the whole of the furnace lining. I do have a more or less endless supply of waste oil however since there is a truck stop a little way from here and they are more than happy to let me have all the waste oil I can suck out of their tank without making a mess. (this is key)I was shooting for a furnace this big so that no matter what I wanted to pour (100 grams or 10 pounds) I would be able to do it with one tool. Not feasable? Directions please. I do have an overhead cherry picker (crane) that I can use to swing the crucible out of the furnace and over my moulds so un less it is more than 1 ton I should be able to move it pretty easily solo.

I am trying to eventually be able to pour a mill bed (18"x4"x48" 3456 cubic inches of aluminum. plus or minus. Im guessing righ around 330 pounds or so. That is one big pour. I am not exactly sure how I am going to do that since I am still in the process of making the furnace. I say aim high it is easy to lower the sight later.

Oh, the more the merrier, absolutely, but that's like having a house with walls 18" thick. A bit overkill. Refractory can be either insulating or non-insulating, depending on what is added to it. Clay/sand/perlite works okay in a small furnace, as long as you don't push it up much past bronze temps very often. Perlite will work as a flux at higher temps than that and you will have a puddle of slag instead of a furnace. Not to squash your aspirations, it may be better to start a bit smaller and learn sandcasting with smaller molds. The principles carry over to larger stuff, and will be less frustrating when it goes wrong. 18"x4"x48" will require a mold that is probably 24"x8"x60", which is pretty massive for backyard purposes, not to mention heavier than heck.

Agreed. Ok so I have a steel 10 gallon drum that is 11 inches high and 22 inches tall...