The DB Class V 51 (from 1968: DB Class 251) and DB Class V 52 (from 1968: DB Class 252) are classes of almost identical narrow gauge 4 axle diesel hydraulic locomotives built in 1964 for the Deutsche Bundesbahn, being built for 750 mm (2 ft 5 1⁄2 in) and 1,000 mm (3 ft 3 3⁄8 in) gauge lines respectively.Both are outwardly similar to the standard gauge DB Class V 100 and were built ot replace steam locomotives on the narrow gauge lines in Baden-Württemberg.Due to partial line closures the locomotives did not all work for long for the Deutsche Bundesbahn, subsequently working for different private companies in Italy, Spain and Austria.