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Diesel Locomotive Roster – The WDM (ALCO) Series

️Wed May 25 2016

The WDM class are the general handyman locomotives of the Indian Railways. They are the most basic of all locomotives in India, the most popular, most adaptable and widely used as they have been around the longest and hence have the most number of people qualified to service them. They can it into any schedule as they can haul anything and run anywhere. And except for the WDM4, all of them were ALCOs based on the WDM2, with later models being the same old ALCO with its faithful engine rebuilt and rebuilt to crank more power out of it.

Diesel locomotives are built and maintained in India at the Diesel Locomotive Works (DLW), Varanasi or at the Diesel-Loco Modernisation Works (DMW), Patiala. ALCOs are today a vanishing breed with new EMDs coming in and more lines being electrified. Only two among all ALCO models is in production today.

Here are the 13 WDM series locos. Click here for the WDP and WDG Series engines

WDM1

Supplied by ALCO, USA, all imported
12-Cylinder 4-Stroke Turbocharged Diesel
Rated Power Output: 1900 hp
Production Period: 1957 to 1959
Number Produced: 100
Wheel Arrangement: Co-Co
Top (Rated) Speed: 100 kph

The very first diesel mainline locomotives in India, part of ALCO’s DL500 World Series locomotives. Classic American “butch” good looks with only one forward cab which necessitated a lot of turntables. They were housed at Bondamunda (Rourkela), Vizag, Gonda, Patratu and Gorakhpur, serving present-day NER, ECR, SER, ECoR and SCR. It was relatively underpowered by today’s standards but hauled most of the first dieselized expresses in India. All were imported fully built and some were in service until 2000. Today all are withdrawn and most are scrapped, though many of the same kind are still in service in Pakistan, Sri Lanka, Kenya etc. Their heyday was before the large-scale advent of cameras and hence not much information or pictures are available of them. The very first WDM1 #17000 is on display in the National Rail Museum, New Delhi.

WDM2

12-Cylinder 4-Stroke Turbo Diesel (Alco 251B)
Rated Power Output: 2600 hp
Production Period: 1962 to 1998
Number Produced: 2700+
Wheel Arrangement: Co-Co
Top (Rated) Speed: 120 kph
Supplied by ALCO, USA and later manufactured at CLW, DLW

The WDM2 ALCO is the quintessential Indian locomotive, the picture that comes to the mind of the average Indian when you say “Locomotive”, with it’s Hood Unit cab and long narrow body. The WDM2 is the workhorse that powered the Indian Railways to what it is today and set the standard for all Diesel Locomotives for more than four decades. However, these definitive “Indian” locos are actually American, based on the ALCO 251, imported starting in 1962 and later mass-produced in India. The ALCO was perfect for “Indian conditions”: rugged, very reliable, powerful enough, had simple construction and mechanics and was easy to operate and maintain and was very malleable, enabling engineers to tweak and tinker with the engine to produce different versions of it. ALCOs hauled most premier Expresses, many of them double-headed as a single WDM2 could haul only 12-14 coaches. The seemingly indestructible ALCO engine in its various forms is going strong even today after rulling the Indian Diesel scene singlehandedly for 37 years! It is no longer in production today, the last WDM2 (#16887) rolled out on August 1 1998.

All Diesel Locomotives in India except the WDM4 and WDG4/P4x EMDs are based on the WDM2 ALCO as they use the same old ALCO 251 diesel engine in various upgraded guises, not to mention the looks. WDM2s are still in service though their numbers are fast dwindling as they are either being withdrawn or converted to WDM3A. The very first ALCO, the #18040 is preserved at the NRM, Delhi. The WDM2 has some variants as well:

Jumbos: Locos with a rebuilt short hood with big windows. Looks a bit like an elephant? Here.
WDM2A: WDM2s rebuilt to feature Air Brakes. The initial ones had only vacuum brakes.
WDM2B: WDM2s with Air Brakes as standard equipment. Only few are classified so.
WDM2S: WDM2s relegated to shunting duties when their service life was nearing completion.

WDM2G

Latest, Unique Multi-Genset Locomotives
Has three 800 hp engines (Gensets) in Parallel instead of a single prime mover.
Rated Power Output: 2400 hp (800 hp x 3)
Production Period: 2013 –
2 built (80000 and 80001)
Wheel Arrangement: Co-Co
Top (Rated) Speed: 120 kph
Based on the WDM3D without the ALCO engine
Tremendously energy efficient, multipurpose locomotives fully Made in India

A breakthrough in locomotive technology, the unique WDM2G is a testimony to the brilliant engineers at RDSO and Indian Railways. This is the latest ALCO, based on the WDM3D with it’s same underframe and high-adhesion bogies. The single 3300 hp engine of the WDM3D has been replaced by three 800 hp “gensets” which can work individually in parallel. This means that one, two or three of the Gensets can be operated depending on the situation and power required, translating into tremendous energy-efficiency (two engines can be shut down while running light or idling). It seems under-powered, but it has been developed intentionally as a low-powered loco to address the gap left behind by the WDM2. The WDM2G is ideal for an entire range of low-power duties like hauling small passenger trains and expresses of 10-12 coaches, departmental duties, at many industrial sites and for shunting. The WDM2G can relieve all the higher powered locos wasting away doing these duties currently, bringing about a lot of process streamlining. It is completely indigenous, designed, developed and made in India! Looks only vaguely like the Indian ALCOs and more like some American locomotives (CSX etc). Two WDM2Gs have been produced and are both at Itarsi, the numbering scheme indicates many more are to come. It does not follow the IR naming convention, the “G” probably stands for “Genset”.

WDM3

Imported Henschel & Sohn DHG 2500 BB
Mercedes Diesel Engine
Rated Power Output: 2300 hp
Production Period: 1970
Number Produced: 8
Wheel Arrangement: B-B
Top (Rated) Speed: 120 kph

Not much is known about WDM3 locomotives but they were possibly the result of IR trying out a different manufacturer. There are no details available about what these locos were used for,where they were housed or what they did, not even a photo is available. They were reportedly decommissioned in Gooty in 1995, so they were in service for 25 years. And these locomotives were diesel-hydraulic, an anomaly in India where all other locomotives are diesel-electric! No WDM3x locos in service today has got anything to do with these locos.

WDM3A

16-Cylinder 4-Stroke Turbo Diesel (Alco 251C)
Rated Power Output: 3100 hp
Production Period: 1994 to 1998
158 built, 700+ rebuilt WDM2s (Total 1200+)
Wheel Arrangement: Co-Co
Top (Rated) Speed: 120 kph
Based on the WDM2, upgraded by DLW.

Thanks to “chalta hai” complacency, it took 42 years for the Indian Railways to come out with a new diesel locomotive after the WDM2! Even then, the WDM3A was just a reincarnation of the same old ALCO. The 12 cylinder ALCO engine was rebuilt with 16 cylinders to output 3100 hp. These were initially classified WDM2C but later changed to WDM3A (for 3100 hp) as per the new classification scheme. Though there are around 1200 WDM3As today, only some 150 odd were originally built as WDM3As, most of them “baldies” like the one in the picture. The rest are WDM2s with their engines rebuilt to output 3100 hp. Rebuilt WDM3As can be identified by a “R” at the end of their Road Number. Some of these have DBRs fitted on their short roof which makes it look like they have a “hoodie” covering their short hood top, a predominantly WDM3D feature. The WDM3A also laid the foundation for the remaining WDM3x series. Most of the “ALCOs” seen today are WDM3x series and not WDM2s. All dimensions of the WDM3A are identical to the WDM2, except for the baldies.

WDM3B

16-Cylinder 4-Stroke Turbo Diesel (Alco 251C)
Rated Power Output: 3100 hp
Production Period: 2005 to 2006
23 built. Most rebuilt into WDM3D
Wheel Arrangement: Co-Co
Top (Rated) Speed: 120 kph
Stripped-down version of the WDM3D

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 (road numbers #14144 to #14167), 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 (were) 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.

WDM3C

16-Cylinder 4-Stroke Turbo Diesel (Alco 251C)
Rated Power Output: 3300 hp
Production Period: 2002
54 built, all rebuilds of WDM2 and WDM3A
Wheel Arrangement: Co-Co
Top (Rated) Speed: 120 kph
Just a more powerful WDM3A
All converted back to WDM3A or WDM2.

WDM3Cs 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 WDM3A to squeeze more power out of the ALCO engine, an intermediary that would later lead to the development of the WDM3D. Not many were produced, all of which were rebuilds of the WDM2 or WDM3A and were identical to the ALCOs in every aspect. You cannot find these anywhere today because all have been reverted back to WDM2 or WDM3A.

WDM3D

16-Cylinder 4-Stroke Turbo Diesel (Alco 251C)
Rated Power Output: 3300 hp
Production Period: 2003 to today.
344 built. 20 rebuilds included.
Wheel Arrangement: Co-Co
Top (Rated) Speed: 160 kph
Based on the WDM3A with EMD features.

While still being based on the good old ALCO, the WDM3D was a pathbreaking kind of locomotive for the Indian Railways, the “real” next generation” after the WDM3A. With the WDM3D, 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 lots of 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.

WDM3E

16-Cylinder 4-Stroke Turbo Diesel (Alco 251C)
Rated Power Output: 3500 hp
Production Period: 2008
8? built and all converted to WDM3D
Wheel Arrangement: Co-Co
Top (Rated) Speed: 105 kph
Experimental class based on WDM3D

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 kph. They look exactly like the WDM3D and share all its features.

WDM3F

16-Cylinder 4-Stroke Turbo Diesel (Alco 251C)
Rated Power Output: 3600 hp
Production Period: 2008
4 built and in service
Wheel Arrangement: Co-Co
Top (Rated) Speed: 105 kph
Extremely rare to find.
Based on the WDM3D

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 4 were produced (#11287, #11321, #11325, #11342). #11287 has a unique aerodynamic design where the ends taper upwards (picture above). All WDM3Fs are based at Gooty (GY) 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.

WDM4

16-Cylinder 2-Stroke Turbo Supercharged Diesel
Rated Power Output: 2600 hp
Production Period: 1962
72 all imported
Wheel Arrangement: Co-Co
Top (Rated) Speed: 130 kph
First EMD locomotives in India

The WDM4 was the ALCO WDM2 competitor from GM EMD in 1962, which despite being technically superior to the ALCO lost out because as per the lore goes, GM was not willing to give technological transfer rights to Indian Railways. They were all vacuum braked and faster than the ALCO. All were imported and one was even used to haul the very first Rajdhani from Howrah to Delhi in 1969! Many other prestigious expresses boasted of the WDM4 as their first Diesel link on switchover from steam. All are decommissioned now and one is on display at the National Rail Museum. New Delhi.

WDM6

6-Cylinder Inline, 4-Stroke Diesel (ALCO 251D6)
Rated Power Output: 1350 hp
Production Period: 1982
Only TWO were built.
Wheel Arrangement: Bo-Bo
Top (Rated) Speed: 75 kph
Mainline Loco with Shunter specifications.

The WDM6 is an aberration, a little locomotive that was too diminutive to do anything substantial. Though classified as a mainline BG locomotive, this ALCO had all the specs usually reserved for shunting locomotives including a low powered prime-mover, fabricated Bo-Bo bogies and low top speed. It actually had the same specs as the WDS6 shunter which was already in production. The engine was one with some minor tweaks, the same ALCO used in Meter Gauge diesel locomotives. It also lacked the “ALCO looks” with a high, hooded cab and had only two of its kind produced. One (#18901) is retired the other one (#18902) is supposed to be still puttering around Bardhhaman. Maybe IR was experimenting with low powered locos to pull local trains. (Pictured above, another version of the WDM6 built for export to Sri Lanka). This was not included in the new classification scheme.

WDM7

16-Cylinder 4-Stroke Diesel (ALCO 251D16)
Rated Power Output: 2000 hp
Production Period: 1987-1989
15 were built and all are still in service.
Wheel Arrangement: Co-Co
Top (Rated) Speed: 105 kph
Low powered version of the ALCO.

The WDM7 was another loco that stood out from the rest. 15 of them (#11001 to #11015) were built as a low-powered, “lightweight” version of the original ALCO and were the first “standout” mainline version of the ALCO to be produced after the WDM2, 25 years later! Funny that the first two ALCO models are at the either ends of the naming scheme. Again, like the WDM6, maybe IR wanted a lower powered locomotive to handle small rake local and passenger services. However, all sheds declined them and they ended up at ERS where they were used to handle local and shuttle services (NBR-SRR-ERS-KTYM/ALLP-KYJ-QLN-TVC-NGJ) with good degrees of efficiency. Becoming aware of their abilities, SR moved all the WDM7s out of Ernakulam to Tondiarpet (TNP) where they are housed today. One (#11008) has been modified to run on Bio-Diesel. They look exactly the same as the WDM2 except for the “clean” SHF nose.

The railways are moving away from Mixed type locomotives and is now following the policy of dedicated locomotives for passenger and freight services. ALCOs had been serving as WDPs and WDGs for quite some time now, but as ALCOs were generally getting long in the tooth, IR is now tinkering with the more modern EMDs as WDPs and WDGs. More about those locomotives classified as such in the next part.

More Chapters on Indian Locomotives

Locomotives of the Indian Railways | Locomotives Terminologies and Design

How Locomotives are Classified | How Electric and Diesel Locomotives Work

DIESELS: The WDM Series (ALCOs) | The WDP and WDG Series (ALCOs and EMDs)

ELECTRICS: DC and AC/DC Locos | The WAM Series (AC mixed) | The WAG Series (AC Freight)