These units have been retro-fitted with air brakes, in addition to the original vacuum brakes. The WDM-7 locos have a maximum speed of 105 km/h (65 mph),[2] restricted to 100 km/h (62 mph) when run long hood forward - the gear ratio is 94:17.
History
These locos were built from 1987 to 1989. A few were at Ernakulam earlier but later all were transferred to Tondiarpet seen being used as shunters at Chennai Central or for light passenger haulage. Some are at the thermal power station, Chennai.
These Co-Co diesel-electrics were designed for branch-line duties (top speed 105 km/h). They have two 3-axle bogies and are similar to the WDM-2 in appearance. The power-pack is a 12-cylinder Alco 251B unit. They are lower powered version of the WDM-2. They were formerly housed at Erode and Golden Rock also. They are reliable and rugged locomotives even though low powered. They can be easily recognised by the lack of grilles on the short hood. Two locos are running on a mixture of bio-diesel and diesel. All 15 are still in service.