I've been reading up on building a crucible furnace in order to melt and cast bronze fittings. Although casting involves a lot more than melting metal, it is the necessary first step, after which the patternmaking and casting can follow.
There's quite a range of designs available, from charcoal fueled coffee can machines useful for making jewelry, on upward to gas fired units capable of melting more bronze than you might want to handle without an overhead gantry.
It might be prudent to start simple and make a fairly basic unit to get started, however, the more sophisticated designs incorporate more features that make handling the molten metal a much safer operation.
This design is taken right from David Gingery's book "Building a Gas Fired Crucible Furnace". It seems a well thought out design and I see little reason to modify it.
These various bits of sheet metal will form the body of the furnace itself. The round bits are 16 ga. black iron, rolled at the sheet metal shop to close to their finished diameter. They're heavier than called for, but that's what was available. There's a bit of exhaust pipe from an auto parts store and some galvanized stuff for a temporary form.
T'ain'tmuch, but it's a start. I'll put up a few photos as things progress.