Blakney Cupola
The Encyclopedia of Founding (1892)
The Blakney cupola consists principally of a system of tuyeres, by which, it is claimed, the air is so distributed or projected into the furnace as to produce a uniform heat, giving the iron a uniform strength for all kinds of castings. The features peculiar to the above furnace are as follows: The introduction of a combination of curved tuyeres or chutes placed upon the wall or lining of the cupola, and forming a part of the wall, a proper distance from the bottom and nearly surrounding the inner and outer sides of the wall. The tuyeres are made of cast iron and in sections for convenience of handling. A blank space is left in the rear of the cupola two feet wide, through which the slag is blown, if required. A chamber or base extending around the cupola incloses the space in which the air is conducted to the tuyeres. The bottom of this chamber, made irregular in form, hollows at suitable intervals to allow the metal to flow to the escape openings, in case it overflows through the tuyeres. The openings are closed with fusible plugs of lead or other material to be melted out by the molten metal. The blast is conducted to this cupola through one pipe, and, striking the blank space sidewise in rear of chamber, passes all around through the curved tuyeres into the centre of the furnace, the blast striking into the cupola every 7/8 of an inch horizontal, and 3 3/4 inches perpendicular, or according to diameter of cupola. As a producer of a uniform grade of iron for the purpose of casting car-wheels it is just what is needed for the different grades of iron to prevent chill-cracking. This cupola, with its many superior advantages, has also rows of shelves bolted to the shell four feet apart up to the top of the charging-door, so that it will not be necessary to tear out any of the lining except that which is burned out. Blast is air forced into a cupola or furnace by a blowing-engine, blower, or fan for the purpose of increasing combustion. If heated it is then called hot blast, and cold blast when it enters the cupola or furnace direct from the atmosphere. See CUPOLA; BLOWERS; BLAST-PIPES.
What Has Changed in the Last Century
When The Encyclopedia of Founding described this in 1892, the Blakney cupola was one of dozens of patented tuyere arrangements competing to sell foundrymen a "uniform grade of iron," and its main selling point was casting railway car-wheels without chill-cracking. Both the machine and its market are gone: chilled cast-iron car wheels were displaced by forged and rolled steel wheels in the first half of the twentieth century, and iron melting itself has largely moved from the coke-fired cupola to the electric induction furnace, which reaches a controlled temperature without a blast at all. Cupolas do survive in a few large iron foundries, but in a form the 1892 writer would not recognise: water-cooled tuyeres, hot blast, oxygen enrichment and continuous chemical analysis of the tapped iron. The proprietary name Blakney has vanished from the trade entirely, and the entry now reads as a snapshot of an era when a cupola could be sold on the geometry of its air holes.
Written for this edition, 2026.