Adriatico / FS 4-6-0 Locomotives in Italy

Class Group 500/Gruppo 670 (Locobase 1472)

Data from See also Gustav Reder (Michael Reynolds, trans), The world of steam locomotives (New York: Putnam, 1974), pl 259; and [] (visited 30 June 2005). See also Dr. R. Sanzin, "Die Lokomotiven auf der Intertionalen Austellung in Mailand 1906, 18. 3/5 gekuppelte vierzylindrige Verbund-Schnellzuglokomotive der italienischen Staatsbahnen ...", Zeitschrift des Oesterreichischen Ingenieur- und Architeckten-Vereines, Vol LVIII Nr. 50 (14 December 1906), p 697-699. (Thanks to Alexander Blessing for his 10 September 2019 email reporting the bunkers' coal capacity.)

The latter site credits the class with a maximum speed of 110 km/h (68 mph).

Among the first of the cab-forward designs, the engine was designed by Giuseppe Zara to allow the large grate to sit over the leading truck, which placed it lower than a conventional design would have allowed. In a departure from typical four-cylinder compound design, a Plancher layout put both HP cylinders on one side (the right), LP cylinders on the other. This created problems in equalizing the force between the two sets, but engineers used the "simpling" valve (which admitted live steam to all cylinders for starting tractive effort) to balance the forces.

The first in the class was shown at the Paris Exhibition in 1900. Unlike the later Southern Pacific "back-ups", these engines burned coal carried in side bunkers. They were nicknamed "Muccas" (cows) and operated successfully through the 1930s. When superheated, they became Class 671.