Indian locomotive class WDM-3A
The Indian locomotive class WDM-3A is a class of diesel-electric locomotive that was developed in 1993 by Diesel Locomotive Works, Varanasi for Indian Railways. The model name stands for broad gauge, Diesel, Mixed traffic engine, with 3300 horsepower. The WDM-3A is a later classification of earlier WDM-2C. They entered service in 1994. A total of 143+ WDM-3A was built at ALCO and Diesel Locomotive Works, Varanasi between 1994 and 2003 with rest of the 1246 units being rebuild from WDM-2 which made them the most numerous class of mainline diesel locomotive until the WDG-4.
The WDM-3A is one of the most successful locomotives of Indian Railways serving both passenger and freight trains for over 26 years. A few WDM-3A units were exported to neighboring countries like Sri Lanka and Bangladesh. Despite the introduction of more modern types of locomotives like WDG-4 and electrification, a significant number are still in use, both in mainline and departmental duties. As of 2020, 1081 locomotives still retain "operational status" on the mainline as WDM-3A, with further examples having been converted back to WDM-2 or WDM-2S. The loco is now widely used across India for long-distance passenger trains due to its ruggedness and high tractive loads and acceleration.
History
The first one was delivered on August 22, 1994, It was then WDM-2C. First 57 units produced till March 1996 had rounded front hood profile similar to contemporary newer classes of locos built by DLW. After that there was a gap of long four years in the WDM3A production line in DLW. These units have been retro-fitted with dual brakes, in addition to the air and vacuum brakes. The WDM-3A locos have a maximum speed of. The gear ratio is 65:18. These new locomotives had their control stand shifted to the left side of the cabin. Meanwhile, Diesel Loco Modernization Works in Patiala started rebuilding the existing WDM2 locomotives, which had reached midlife, with upgraded power-packs. DLMW Patiala re-calibrates the power-pack and upgrades the output power rating to 3100HP. DLW again started building WDM3A from the year 2000 and continued till the end of 2002 with locomotive road numbers in the range 14058–14143. All the locomotives rebuilt by DLMW and later batch from DLW had regular WDM2 type square short hood profile and control stand position. DLW again built WDM3A variant locomotives, during 2005–2006, in the road number range 14144-14167 which were classified as WDM3B due to their difference in bogie design from classic ALCo asymmetrical trimount to HAHS design which was employed in WDG2 and later WDM3D classes too. Most of the WDM3B were later converted to WDM3D. In 2011, DLMW rebuilt locomotive number 16502 as WDM3A and equipped it with an Electronic Fuel Injection system jointly developed by Engine Research Laboratory of IIT Kanpur, Engine Development Directorate of RDSO, and DLMW Patiala. DLMW continues to rebuild WDM2 as WDM3A and recently they have started rebuilding the DLW built WDM3A too when they reach their midlife. Recent rebuilt locomotives are rated at 3300 HP, and from 2009 onward they are equipped with Daulat Ram DBR, and since 2014 they are also equipped with an Auxiliary Power Unit in the short hood. Some rebuilt locomotives have Co-Co-fabricated ATHS bogies instead of ALCo cast-iron type. All the rebuilt WDM3A bear the suffix to their road numbers.In 2012 Bangladesh Railway ordered 26 WDM3A from DLW. They are classified as Class 6500 there. These units, however, lack the dynamic braking which happens to be an essential component in their Indian counterparts.
Sub Class
WDM-3B: The WDM3B diesel locomotive class was developed in 2005 after the WDM3C and WDM3D. It actually is a variant of the WDM3D, though it shares its power rating with the WDM3A. Only 23 numbers were built, making them very rare. It has the same engine as the WDM3D, despite having a power deficit of 200 hp. It also looks the same, shares the same body shell, control cabin, undercarriage and the high-adhesion bolsterless bogies of the WDM3D. The difference is that unlike the WDM3D, the WDM3B is not microprocessor controlled but uses something called “E-Type Excitation” for locomotive control. The WDM3B seems to be the result of the Railways trying to cut the WDM3D down to size by eliminating its troublesome features like microprocessor control. But now 3Bs are being converted into 3Ds. WDM3Bs are housed at UP sheds like Lucknow, Gonda, Jhansi, Samastipur, Patratu etc. and many are famously named “Gajraj”. The WDM3B does not adhere to the hp-based naming convention as WDM3A already represented 3100 hp. IR just assigned the vacant WDM3B class to this type.WDM-3C: They were just upgraded and more powerful WDM3As with the ALCO engine gain rebuilt to output 3300 hp. It was the first follow-up experiment after the WDM-3A to squeeze more power out of the ALCO engine, an intermediary that would later lead to the development of the WDM-3D. Not many were produced, all of which were rebuilds of the WDM2 or WDM3A and were identical to the previous variants in every aspect. They can no longer be found over the railway network as all of them have been rebuilt into the WDM-3A or WDM-2 type.
WDM-3D: While still being based on the good old ALCO, the WDM3D was a groundbreaking kind of locomotive for the Indian Railways, the “real” next generation” after the WDM-3A. With the WDM-3D, IR finally got it right on how to rebuild the old ALCO engine to produce 3300 hp. By this time, EMDs had become a staple of the scene and along with the rebuilt engine, the brilliant DLW and RDSO engineers were now successful at integrating the best features of EMD locomotives like microprocessor control, larger fuel tanks and oil sump, possible fiberglass cabin and improved control stands into the ALCO, making it a kind of EMD-ALCO hybrid! These locomotives can be easily distinguished from other ALCOs by the “narrower” body shell with much walkway space around it, full-length railings, predominant “platform” space extended up front of the long hood, solid cowcatcher and DBRs fitted on the roof of the unblemished, smooth short hood for some later models and rebuilds, giving them the “hoodie” look. Comparing with the WDM3A, the WDM3D can carry 1.5 tonne more axle load and generates 8 tonnes more Maximum Tractive Effort. The engine is classified WDM3D though it outputs only 3300 hp and not 3400 hp as the name should suggest. Earlier WDM3Ds had issues with their electronics which probably led to the interim development of the WDM3B in 2005, basically a lower powered WDM3D without microprocessor control. Their Road Numbers start from #11001. The WDM3D along with the WDG3A are the only ALCO models currently in production and mostly haul express services.
WDM-3E: This was an experimental class developed out of the WDM3D by IR on the ever-lookout for more power, all equipped with High Adhesion bogies and roof-mounted DBRs. However, they never entered serial production. Some suggest that the WDM3E is actually called “WDM3D without Equalizer” or WDM3Ds with 3500 hp power. The known road numbers in service for this class are #11306 to #11311 and #11263. All are marked WDM3D and all are used to haul only freights with speed restricted to 85 km/h. They look exactly like the WDM3D and share all its features.
WDM-3F:The very extremely rare WDM3F was the result of the last and final experiment in IR’s drive for more powerful ALCOs. This one is rated 3600 hp and only four were produced. #11287 has a unique aerodynamic design where the ends taper upwards. All WDM3Fs are based at Gooty and share all the features of the WDM3D including roof mounted DBRs except the #11287. Though high powered, this class apparently didn’t work out well because after the WDM3F, IR realized that it is futile to try and crank more power of the ALCOs as they were too old and outdated and shifted attention to the EMD. This also marked the beginning of the end of the ALCO domination on Indian Railways.
Locomotive sheds
Technical specifications
Technical details are as follows:| Manufacturers | DLW, DLMW |
| Engine | Alco 251-C, 16 cylinder,, earlier with Napier NA2951R/ ABB VTC-304-VG15/ GE 7s 1716 turbo supercharged engine. 1,050 rpm max, 400 rpm idle; bore x stroke; compression ratio 12.5:1. Direct fuel injection, centrifugal pump cooling system, fan driven by eddy current clutch |
| Governor | EDC / Woodward 8574-650 |
| Transmission | Electric, with BHEL TA 10102 CW alternator |
| Traction motors | BHEL TM 4906 AZ/ 4907 BZ |
| Axle load | , total weight |
| Bogies | Alco design cast frame asymmetric trimount bogies |
| Starting TE | at adhesion 27%, continuous |
| Length over buffer beams | |
| Distance between bogies |