Cupola Furnace: the Common Foundry Cupola with a Drop Bottom (Bolland, 1893)

The founder's 'common cupola': an upright steel shell lined with firebrick, standing on four columns over a drop bottom, with a wind-box round it feeding the tuyeres and a charging door high up. Coke and pig iron go in at the top in layers; blast at the tuyeres melts the iron, which runs out at the spout. Variable: the inside diameter, 24 to 84 in, which sets height, tuyeres, blower and charges. Fig. 9's 36 in cupola is 12 ft to the charging hole and takes 840 lb coke and 2520 lb iron on the bed, then 302 lb coke and 2718 lb iron per charge. Source: S. Bolland, The Iron Founder Supplement (1893), pp. 34-54. Unknown: shell plate and brick sizes. Picture: Fig. 9 of the book.