The River Don Engine is a 1905-built steam engine used for hot rolling steel armour plate. It is a 3-cylinder simple engine of 40 inches (1.0 m) diameter, 48 inches (1.2 m) stroke. At its operating steam pressure of 160psi, it developed 12,000 horsepower (8.9 MW), and was able to reverse from full speed in 2 seconds. The rapid reverse was an essential feature of an engine used for rolling, as delays would result in cooling of the workpiece. This engine was one of four built to the same design, one going overseas to the Japanese Government, one to John Brown's Atlas plant, and the destination of the final one being unaccounted for.