Portable Furnaces
The Encyclopedia of Founding (1892)
A French portable brass furnace consists of a furnace with a fixed crucible, and arranged so that the castings may be poured direct from the crucible without removing it from the furnace, the two moving simultaneously from the furnace to the moulds, and vice versa. The metal may be fused by the use of fuel, the ashes of which can be cleaned out of the furnace before casting, or the latter annoyance may be obviated by connecting with a regenerative or a gas-blast system. That part of the furnace which contains the fixed crucible is set in standards provided with bearings for the trunnions to rest in, and the standards being secured to a suitable truck, the whole is run on the tracks for casting, which operation is readily performed by means of a small hoist attached to one of the standards, which tilts the furnace sufficient to allow the metal to flow from the crucible at its upper edge. See GAS-BLAST FURNACE; BRASS FURNACE. A very handy and serviceable portable cupola for melting cast iron or other metals may be made and mounted on wheels, for use on special occasions, such as mixing for tests, or taking off a very light heat occasionally. The shell could be of 1/16 plate, and large enough in diameter to measure about 18 inches diameter when lined with 4-inch bricks. Its height might be 60 inches, with wind-box attached, covering 3 tuyere holes 2 1/2 inches diameter, pierced about 16 inches from the bottom plate. A small fan-blower set back of the cupola could be arranged for running either by hand or power. Made in this manner, the refuse material contained in the cupola, when done melting, would have to be drawn out at the front or spout; but this might be obviated by suspending the cupola on central trunnions, and by this means eject the whole contents at the mouth. The latter method is a great help in cleaning and repairing so small a cupola. With efficient blast and good management such a cupola should melt 1000 pounds per hour. See CUPOLA.
What Has Changed in the Last Century
When The Encyclopedia of Founding described these in 1892, small-scale melting meant fuel: a coke-fired crucible on trunnions, or a wheeled cupola with a hand-or-power fan-blower, good for about 1,000 pounds of iron an hour. Electricity displaced nearly all of it. The coreless induction furnace, developed commercially in the years around the First World War, became the standard small melting unit because it heats the charge directly, leaves no coke ash or slag to be raked out at the spout, and can be tipped and emptied between alloys; gas-fired tilting crucible furnaces took most of the rest of the work. Portable cupolas of the kind sketched here have effectively vanished from industry, pushed out by air-quality rules on particulate and carbon monoxide emissions as much as by economics, and survive mainly among hobby casters and iron-pour artists, who more often build small propane-fired furnaces instead.
Written for this edition, 2026.