The Nilgiri Mountain Railway in Southern India had 17 miles of adhesion track and 12 miles equipped with a rack rail of the Abt system. As they needed more powerful locomotives, they ordered the first six X class 0-8-2RT locomotives which were delivered by the Swiss SLM in 1914. Four followed in 1920 and two in 1925.

They had a rack drive of the Winterthur system, what promised savings in coal of up to 35 percent. This meant that the high and low pressure cylinders were on top of each other. The low pressure cylinders turned the two rack wheels via a 1 to 2,1 reduction gear. The position of these rack wheels can be seen in the long distance between the second and third driving axles. To allow for more flexibility in curves, the first and fourth driving axles were movable sideways.

Original appearance

flickr/Historical Railway Images

When the NMR saw the requirement for additional locomotives in 1952, SLM delivered an additional five. In 2002, the first X class locomotives were converted to run on diesel fuel, which can be distinguished by the additional saddle tank. To reduce wear and tear on the existing locomotives, the Golden Rock Railway Workshop built four new between 2011 and 2014. Two more were built in 2021 and 2022, of which one is coal fired.