The WDM-2A is a variant of the original WDM-2. These units have been retro-fitted with air brakes, in addition to the original vacuum brakes. The WDM-2B is a more recent locomotive, built with air brakes as original equipment. The WDM-2 locos have a maximum speed of 120 km/h (75 mph), restricted to 100 km/h (62 mph) when run long hood forward - the gear ratio is 65:18.
Left:18040 WDM-2 diesel loco at National Railway Museum, Delhi, Right:18233 WDM-2 Kundan, first diesel loco assembled at DLW,Varanasi
Left:17212 WDM-2 diesel loco of Vijaywada (BZA), Right:17585 WDM-2 diesel loco of Moulali (MLY)
In the early 1960s Indian Railways began conversion of its mainline from steam to diesel locomotives. For this conversion General Motors Electro-Motive Division (EMD) and the American Locomotive Company (ALCO) were asked to submit designs for new diesel locomotives. Each company submitted prototypes. Indian Railways designated these prototypes the WDM-4 class and the WDM-2 class respectively. Technologically the General Motors WDM-4 was superior to ALCO's WDM-2, but Indian Railways required a transfer of technology agreement that would allow these locomotives to be manufactured in India. General Motors did not agree to the transfer of technology agreement so the ALCO prototype was selected for production. The first few prototype WDM-2s were imported. After Diesel Locomotive Works (DLW) completed construction of its factory in Varanasi, production of the locomotives began in India. The first 12 locos were built using kits imported from ALCO in the United States. After that DLW started manufacturing the WDM-2 locomotives from their own components. Since then over 2,800 locomotives have been manufactured and the WDM-2 has become the most popular locomotive in India.
However, even before the arrival of WDM-2 another type of diesel locomotive was imported from ALCO beginning in 1957. This locomotive was classified as WDM-1.
Later a number of modifications were made and a few subclasses were created. This includes WDM-2A, WDM-2B and WDM-3A (formerly WDM-2C). Now a few WDM-2 locos are being rebuilt by Diesel Loco Modernization Works (DLMW) Patiala, Punjab - These are fitted with Daulat Ram DBR's
The WDM-2 is the diesel workhorse of the Indian Railways, being very reliable and rugged.
Alco 251-B, 16 cylinder engine, 2,600 hp (1,900 kW) (2,430 hp or 1,810 kW site rating) with Alco 710/720/?? turbo supercharged engine. 1,000 rpm max, 400 rpm idle; 228 mm × 266 mm (8.98 in × 10.47 in) bore x stroke; compression ratio 12.5:1. Direct fuel injection, centrifugal pump cooling system (2,457 L/min or 540 imp gal/min or 649 US gal/min at 1,000 rpm), fan driven by eddy current clutch (86 hp or 64 kW at 1,000 rpm)
Eight WDM-2 locomotives were purchased by Sri Lanka Railways, the state run railroad operator in Sri Lanka in 1996. This is was the longest and most powerful locomotive owned by Sri Lanka Railways at that time. These were allocated M8 Class. However some modifications to the appearance were done by SLR.