Indian locomotive class ZDM-2

The ZDM-2 class was designed and manufactured by Maschinenbau Kiel (MaK). The type was specially developed for the Indian 762 mm railway lines.^[1] Locomotive No 600488 was tested on the Kreisbahn Osterode-Kreiensen 750 mm gauge railway line before delivery.^[2][3] The class was initially used on the Kalka–Shimla Railway and the Kangra Valley Railway, then later in Nagpur.^[4] On the Kalka-Shimla line, ten ZDM-2 locomotives partly replaced the ageing steam locomotives and partly the inefficient and failure-prone ZDM-1 diesel locomotives for passenger transport. On the Kalka–Shimla line, ZDM-1 locomotives pulled only three passenger coaches, while ZDM-2 locomotives often pulled seven.^[1] The ZDM-2 and ZDM-1 locomotives that remained on the line were completely replaced by ten ZDM-3 locomotives delivered between 1970 and 1972, the former being transferred to the South Eastern Railway in 1971–1972 and the latter to the Matheran Hill Railway in 1976.^[1][5] The ZDM-2s were fitted with a hydraulic transmission of the Indian "Suri" type, which proved to be highly failure-prone.^[4] The series was equipped with the Maybach "MD 435" diesel engine.^[4][2] On the first ten units these operated at the speed of 1400 min⁻¹ for a power output of 650 metric horsepower (478 kW), while on the latter fifteen at 1700 min⁻¹ for a power output of 700 metric horsepower (515 kW).^[2]

Several members of the type were modified in the 1980s and 1990s; they were fitted with KPC hydraulic transmissions and MaK diesel engines.^[4][6]