The term locomotive is rooted in the Latin word loco – “from a place”, and the medieval Latin term motive which means, “resulting in motion”. First used in 1814, it is a short form of the word locomotive engine. It was utilized to differentiate between stationary steam engines and self-propelled engines.

An engine or locomotive is a rail conveyance automobile that gives the train its motive energy. If a locomotive is competent enough to carry a payload, it is usually addressed by multiple terms like a railcar, power car or motorcoach.

Conventionally, locomotives are used to pull trains on the track from the front. However, push-pull is a very wide concept, where at the front, at each end, or rear, the train may have a locomotive as required. Most recently railroads have started embracing distributors power or DPU.

Locomotives usually function in certain roles like: –

  • The locomotive which is connected to the front side of a train to pull the train is called the Train engine.
  • Station pilot – The locomotive is deployed at a railway station to switch the passenger trains.
  • Pilot engine – The locomotive connected to the train engine on the front side, to facilitate double-heading.
  • Banking engine – The locomotive is connected to the rear side of a train engine; this is possible through tough sharp or start.

Locomotives are used in various rail transport operations such as: pulling passenger trains, shunting and freight trains.

The wheel configuration of a locomotive depicts the number of wheels it has; popular techniques include the UIC classification, Whyte notation systems, AAR wheel arrangement and so forth.

Difference between freight and passenger locomotives

The most apparent distinction is in the shape and size of the locomotive body. As the passenger trains travel faster than the other trains, air resistance plays a bigger role than it does for freight units. Most passenger locomotives usually have a hood along the length of the body; this may be for aesthetic reasons.

On the other hand, freight units tend to have more reasons to halt where the conductor has to get on and off the engine, and are more liable to be moving backwards, and so they have a thin hood around the real power plant. This gives better visibility when running backwards, and provides room to have stairwells rather than ladders, which makes it much more comfortable for personnel who have to climb on and off the locomotive frequently.

Freight locomotives are created for more torque (a twisting force) and passenger locomotives are manufactured for more speed. A normal freight locomotive engine yields between 4,000 and 18,000 horsepower.

The gearing on passenger locomotives is also distinct from freight in that their ratio is lower, so the traction motor whirls fewer times per wheel rotation.

Normally, passenger engines require increased maximum speeds while freight engines need increased starting traction forces because they hurl heavier trains. This results in various gear ratios in the transmission (which, in electric and diesel-electric engines, does not have numerous gears).


World's first Locomotive
World's first Locomotive

The long narrative of railway transport started in the ancient times. The history of locomotives and rails can be categorised into various discrete intervals distinguished by the chief means of the materials by which the paths or tracks were constructed, and the motive power utilized.

200 years of locomotive technology

The railway thrust technology has seen an explosion of the invention in the previous two centuries.

Cornish engineer Richard Trevithick racked his brains and educated the world about railway creation in the Welsh mining hamlet twenty decades ago. The introduction of the railway transformed dynamics for people through the process across the globe.

Cornish engineer Richard Trevithick
Cornish engineer Richard Trevithick

By exemplifying the first operational railway steam locomotive, Trevithick normalised conveyance uprising; the Industrial Revolution stimulated the blaze of the transport uprising which was heightened and facilitated through the 1900s by modern energy sources and a surging worry for environmental performance and productivity.

From the rudimentary steam engines produced during the 19th century to the progressive momentum (the process of pulling and pushing to make an object move forward) notions that have yet to be completely inspected, here we go down the memory lane through the past, the current and expected fate of advancements in the locomotive technology.

1st steam locomotive
1st steam locomotive

It was only in 2004, that Richard’s endeavour was widely acknowledged, after two hundred years of his influential presentation – from the Royal Mint, that circulated a memorial £2 coin having Trevithick’s name and innovation.

In 1804: Richard Trevithick gifts the age of steam power to the world

In 1804, a mining engineer in Britain, explorer and inventor Richard Trevithick, before his massive rail revolution, had been researching steam engines utilizing high pressure for a long time with varied findings; from the triumphant presentation of the steam-powered road locomotive in 1802 called the ‘Puffing Devil’ to catastrophe in 1803, in Greenwich when there were four casualties due to an outburst of one of his fixed pumping engines. His opponents utilized this unfortunate occurrence to ridicule the hazards of high-pressure steam.


However, Trevithick’s hard work was rewarded and his ‘Penydarren locomotive’, attained a prominent position on account of innovations in the locomotive technology as it came to become the first properly functioning steam locomotive in the railways.

Railway electrification - 1879

In the late 19th century, Germany was the nucleus of electric locomotive growth. Werner von Siemens demonstrated the initial testing electric passenger train. He was the creator and father of the wide-ranging engineering organization Siemens AG. The locomotive, which solidified the notion of the insulated third rail to procure electricity, ferried an aggregate of ninety thousand passengers.

Werner von Siemens

Siemens led to assembling the planet’s earliest ever electric tram line in 1881 in the Berlin exurbia of Lichterfelde, building a foundation for similar locomotives in Mödling & Hinterbrühl Tram in Vienna and the Volk’s Electric Railway in Brighton both inaugurated in 1883.

The requirement for environment-friendly rails in underground passages and subways instigated the innovation of electric trains. After a few years, better efficiency and easy building gave rise to the beginning of an AC.

Kálmán Kandó, an engineer from Hungary, played a major role in the evolution of longer-distance electrified lines, comprising the hundred and six km Valtellina railway in Italy.

In the present day and age, electric locomotives persist to have a significant part to play in the rail terrain through high-speed aids such as Acela Express and the French TGV in the United States. Nevertheless, the huge expense of electrifying lines to leverage electric locomotives, such as overhead catenary or third rail, remains to be a setback and hurdle to the extensive application of the mentioned technology.

Dieselisation procedure - 1892 - 1945

Rudolf Diesel
Rudolf Diesel

Dr Rudolf Diesel’s actual copyright in 1892 on his diesel engine rapidly provoked presumptions as to how this current internal combustion technique could perhaps to railroads thrust as well. This required numerous years since the advantages of diesel can be appropriately understood on rail locomotives.


In the late nineteenth and early twentieth centuries, continuous development and growth were seen in the locomotive industry through more efficient diesel engines with increased power-to-weight ratios.

Many of these emanated at Sulzer, a Swiss engineering company at which Diesel laboured for a long time –made diesel the zenith to compose steam locomotives nearly outdated by the increasing possibility of the brink of the World War, the second. By 1945 steam locomotion had become extremely unusual in advanced and progressive nations and by the late 1960s, it became a rare beast.

Diesel locomotives gave multiple apparent functional benefits, comprising multiple-locomotive operations, remote location accessibility became a reality without the need for electrification in difficult areas like mountains & forests, inexpensive sustenance, waiting time, less labour-intensive working procedure and adequate thermal efficiency.

1945 - present: The growth of diesel-electric locomotives

Once the authority of diesel over steam locomotives was confirmed, the period after the war replenished with suggestions – theories and inventions for enhancing rail thrust, with each accomplishing eclectic achievement. Amid one of the many hare-brained bizarre strategies planned by Dr Lyle Borst of Utah University in the initial nineteenth century, is the nuclear-electric train.

Although the extensive protection and safety significance of ferrying a two hundred tonne nuclear reactor around the country at elevated velocities is neglected, the expense of purchasing the uranium and manufacturing locomotive reactors to power them quickly made the scientists and technicians realize that this idea was not practical.

Many different, better and logical ideas, like gas turbine-electric locomotives earned attraction to some degrees over the period after the war, but diesel continues to be the monarch even now.

From the 3 widespread power transmission systems for the power, the transmission experimented for usage on diesel engines – electric, mechanical and hydraulic – by now it was obvious that diesel-electric had become the new ideal in the world. Out of the three systems including electric, mechanical and hydraulic, diesel-electric locomotives – in the working of which a diesel engine runs an AC or DC generator – have till now exhibited the most improvement in the late 20th century and depict maximum of the diesel locomotives in deployment presently.

By the late 20th century, Diesel-electric locomotives had established the stage for fresh, contemporary locomotion systems which acknowledged environmental skepticism beginning to emerge and conquer rail propulsion debates to date. For example, by 2017, hybrid trains had added a (RESS) rechargeable energy storage system to the diesel-electric procedure that entitles the trains inclusive of the numerous locomotives which were erected under the UK’s Intercity Express undertaking to get started by work.

21st-century trends: Hydrail and Liquefied Natural Gas

Diesel powered the development of railroad networks worldwide for most of the 20th century.

However, in the 21st century, the substantial negative effects of diesel train undertakings on our atmosphere, especially the emission of greenhouse gases like CO2 and the toxic emissions such as nitrogen oxides (NOx), dust and soot have resulted in the advancement of increased greener locomotive technicalities. Few of these are functioning while the rest are still being planned.

The shale gas uprising, an endless effort in the US starting to pick up momentum everywhere around the globe, has urged considerable scrutiny when it comes to the prospect of (LNG) liquefied natural gas as a railroad impulsion fuel. The diesel being rated remarkably higher than LNG, and LNG vowing thirty percent fewer carbon emissions and seventy percent less NOx, it can prove beneficial both economically and environmentally. 


Numerous important freight operators comprising BNSF Railway and the Canadian National Railway in recent years have been experimenting with LNG locomotives to make the shift reasonable. Logistical and regulatory issues continue, but if the price of the fuel advantage remains lofty, the issues will probably be resolved.

LNG may implicate some emissions deduction, nevertheless, it links the industry to the hydrocarbon economy after scientific consensus suggests that the civilization start the shift into a post-carbon future immediately to prevent hazardous climate modifications.

Remote control locomotives began to join service in shifting operations, in the latter half of the twentieth century being regulated a bit through an operator exterior of the locomotive. The major advantage is that 1 operator can govern the loading of coal, gravel, grain and so on into the cars. A similar operator can run the train as required.

Hydrail, a modern locomotive notion that pertains to utilizing sustainable hydrogen fuel cells rather than engines running on diesel, exudes only vapour on the operation. Hydrogen can be generated by low-carbon energy derivatives like nuclear and wind.

Hydrail vehicles utilize the chemical energy of hydrogen for propulsion, either by charring hydrogen in a hydrogen internal combustion motor or by getting hydrogen to react with oxygen in a fuel cell to operate electric motors. Extensive use of hydrogen for fueling rail transportation is a fundamental component of the directed hydrogen economy. The term is used vastly by research professors and machinists around the world.

Hydrail vehicles are normally hybrid vehicles with renewable power storage, like super capacitors or batteries that can be used to reduce the amount of hydrogen storage needed, regenerative braking and enhancing efficiency. Likely hydrail applications comprise all the categories for rail transport like rail rapid transit, passenger rail, mine railways, commuter rail, freight rail, light rail, trams, industry railway systems and unique rail rides at museums and parks.


Hydrail model undertakings have been accomplished through an effective research organization in nations such as Japan, the United States, United Kingdom, South Africa and Denmark, all the while little Dutch island of Aruba is intending to debut the first hydrogen tram fleet globally for Oranjestad, the capital of Dutch island of Aruba.

Stan Thompson, a well-known hydrogen economy advocate said, Hydrail will probably be the planet’s leading autonomous railway propulsion technology till the late 21st century, so it might yet substantiate the cleantech invention to eventually kick locomotives running on diesel from its seat.

Locomotives - classification

Before locomotives had started functioning, the operative force for railroads had been created by different less advanced technology techniques such as human horsepower, static or gravity engines that drove cable systems. Locomotives may produce energy with the means of fuel (wood, petroleum, coal,  or natural gas), or they can take fuel from an external source of electricity. Most scientists usually categorize locomotives based on their energy source. The most popular of them include:

Steam Locomotive

A steam locomotive uses a steam engine at its major source of power. The most popular form of the steam locomotive includes a boiler to produce the steam employed by the engine. The water in the boiler is warmed up by charring flammable substances – wood, coal, or oil – to elicit steam.

The steam of the engine moves the reciprocating pistons which are called ‘driving wheels’ adjoined to its main wheels. Both water and fuel, water stocks are hauled with the locomotive, either in bunkers and tanks or on the locomotive. This configuration is called a “tank locomotive”. Richard Trevithick created the primary full-scale functioning railway steam locomotive in 1802.

Steam Locomotive
A Steam Locomotive

Contemporary diesel and electric locomotives are more worthwhile than, and a considerably smaller crew is needed to manage and maintain such locomotives. The rail figures of Britain exhibited the fact that the expense of fueling a steam locomotive is about more than double the expenditure of supporting a comparable diesel locomotive; the everyday mileage they could run was also lesser.


As the 20th century came to an end, any steam power locomotive still running tracks was considered ancestral railway.

Internal combustion locomotive

Internal combustion engine is utilized in internal combustion locomotives, attached to the driving wheels. Commonly, they keep the motor going at an approximately steady momentum whether the train is static or running. Internal combustion locomotives are classified by their fuel variety and sub-categorized by their transmission type.

Kerosene locomotive

Kerosene is employed as the power source in kerosene locomotives. Lamp oil trains were the first internal combustion locomotives globally, coming before electric, and diesel. The primary recognized rail vehicle which ran on kerosene was constructed by Gottlieb Daimler in 1887, but this vehicle was not exactly a locomotive as it was used to heave cargo. The primary triumphant lamp oil train was “Lachesis”, created by Richard Hornsby & Sons Ltd.

Petrol locomotive

Petrol is consumed as their fuel by the petrol locomotives. A petrol-mechanical locomotive was the very first economically successful petrol locomotive and was manufactured in the early twentieth century in London for the Deptford Cattle Market by the Maudslay Motor Company. Petrol-mechanical locomotives are the most popular kind of petrol locomotive, which employs mechanical transmission in the form of gearboxes to transmit the energy output of the engine to the driving wheels, just like a car.

This sidesteps the necessity for gearboxes with the means of transforming the rotational mechanical force of the engine into electrical energy. This can be achieved with a dynamo and afterward by powering the locomotive’s wheels with multi-speed electric traction motors. This encourages better quickening, as it forestalls the requirement for gear alterations even though it is more costly, hefty, and occasionally heavier than mechanical transmission.

Diesel locomotive

Diesel engines are deployed to fuel the diesel locomotives. In the earlier times of Diesel propulsion growth and advancement, numerous transmission frameworks were used with different magnitudes of accomplishment, with electric transmission ending up being the most prominent among all.

There was development among all sorts of diesel trains; the method through which the mechanical force was disseminated to the driving wheels of the locomotive.

When the world was healing itself monetarily after the World War, it did so by broadly selecting diesel trains in different countries. Diesel locomotives gave tremendous performance and flexibility, and were proved better than steam locomotives, as well as needing considerably less maintenance and operating expenses. Diesel-hydraulic was inaugurated in the middle of the 20th century, but, after the 1970s, diesel-electric transmissions were consumed on a higher level.

An early diesel locomotive
An early diesel locomotive

Motorized transmission to disseminate energy to all the wheels is employed by the diesel–mechanical locomotive. Such kind of transmission is normally restricted to low-speed, low-powered shunting locomotives, self-propelled railcars and numerous lightweight units. The initial diesel locomotives were diesel-mechanical. Most of the diesel locomotives nowadays are diesel-electric locomotives.

The most crucial and absolutely vital factors of diesel-electric propulsion are the diesel engines (also called the prime mover), the central generator/alternator-rectifier, a control system consisting of the engine governor and electrical or electronic elements, traction motors (generally with four or six axles), encompassing rectifiers, switchgear other elements, which regulate or alter the electrical supply to the traction motors.

In the most general case, the generator may be directly bound to the motors with only extremely simple switchgear. Mostly the case generator is bound to motors with extreme switchgear only.

Diesel locomotives powered by hydraulic transmission are called Diesel-hydraulic locomotives. In this configuration, they utilize more than one torque converter, in a mixture with gears, with a mechanical final drive to disseminate the power from the diesel engine to the wheels.

The major global user of main-line hydraulic transmissions was the Federal Republic of Germany.

Gas turbine locomotive

A gas turbine locomotive is a locomotive using an internal combustion motor having a gas turbine. Energy transmission is required by the engines to leverage the wheels and therefore must be permitted to keep running when the locomotion is halted.

These locomotives utilize a self-regulating transmission to provide the energy production of gas turbines to the wheels.

Gas turbines deliver certain benefits over piston motors. These locomotives have limited movable parts, reducing the requirement for grease and lubrication. It reduces upkeep expenses, and the power-to-weight ratio is considerably greater. A similar solid cylinder motor is greater than a turbine of given force yield, empowering a train to be exceptionally profitable and effective without being enormous.

Gas turbine locomotive
Gas turbine locomotive

A turbine’s efficiency and power output both decline with rotational speed. This makes a gas turbine locomotive framework supportive mostly for significant distance drives and fast drives. Other issues with gas turbine-electric locomotives involved the extreme loudness and evoked peculiar noises.

Electric locomotive

A train which is powered exclusively by electricity is called an electric train. It is utilized to move trains with a nonstop conductor working along the track that can by and large take one of these: an easily accessible battery; a third rail climbed at the track level, or an overhead line, joined from posts or pinnacles alongside the track or passage rooftops.

Both third-rail systems and overhead wire generally utilize the running rails as the retrieval conductor but some of the structures employ a distinct fourth rail for this objective. The kind of power wielded is either alternating current (AC) or direct current (DC).

Data analysis shows that low ratios are generally found on passenger motors, whereas high ratios are common for freight units.

Electricity is commonly produced in rather big and yielding generating stations, disseminated to the trains and distributed to the railway system. Only a few electric railways have committed production depots and transmission lines but can access maximum buy power from an electricity generating station. The railway normally furnishes its distribution lines, transformers and switches.

Diesel locomotives normally cost twenty per cent higher than electric locomotives; sustenance expenses are twenty-five to thirty per cent higher and amount up to fifty percent more to operate.

Alternating current locomotive

The Diesel-electric locomotives are prepared with a strong diesel “prime mover”, which produces electrical current for usage on the electric traction engines to literally veer around the train’s axles. Banking on the locomotive’s layout, it can either generate Alternating current or Direct current using a generator powered by the diesel motor.

Charles Brown formulated the initial pragmatic AC electric locomotive, then labouring for Oerlikon, Zürich. Charles had illustrated long-distance power transmission, , between a hydro-electric plant, utilizing a three-phase AC, in 1981.

Contemporary AC locomotives manage to maintain better traction and give adequate adhesive to the tracks than earlier categories and models. Diesel-electric trains powered by alternating current are normally utilized for hauling massive loads. Nevertheless, diesel-electric trains powered by direct current are still very prominent as they are fairly inexpensive to build.

Railways of Italy were the pioneers, worldwide in bringing up electric traction for the whole stretch of a mainline instead of only a brief distance.

Battery Electric Locomotive

A locomotive that is charged by onboard batteries is called the battery-electric locomotive; a type of battery-electric automobile.

These locomotives are utilized where a traditional electric or diesel locomotive will be ineffective. For instance, when the electricity supply is not available, maintenance rails on electrified lines have to use battery locomotives. You could use battery-electric locomotives in industrial buildings where a locomotive powered by a locomotive (i.e. locomotive powered by diesel- or steam) could result in safety trouble due to the fire hazards, eruption or vapours in an enclosed area.

Battery electric locomotives are 85 tons and employed on overhead trolley wire of 750-volt with substantial additional range while operating on mortars. The Nickel–iron battery (Edison) technology was used by the locomotives to deliver numerous decades of service. The Nickel–iron battery (Edison) technology was supplanted with lead-acid batteries, and the locomotives were withdrawn from service soon after. All four locomotives were given to the museums, except one which was discarded.

London Underground periodically runs battery-electric locomotives for the common upkeep tasks.

The advancement of very high-speed service gave rise to more electrification, in the 1960s.

Electrification of the railways has continually heightened in the last few years, and nowadays, electrified tracks are virtually more than seventy-five per cent of all the tracks worldwide.

When electric railways are compared to diesel engine, it is observed that electric railways offer much decent energy efficiency, lesser emissions and reduced running expenses. They are also normally silent, stronger, extra responsive and more credible than diesel.

They have no provincial emissions, a significant benefit in subways and municipal sectors.

Steam-diesel locomotive

Steam-diesel hybrid locomotives can utilize steam produced from diesel or boiler to leverage a piston engine.

Steam locomotives need considerably higher maintenance than locomotives powered by diesel, less staff is required to maintain the fleet in service. Even the most promising steam locomotives expended an average of two to six days every month in the garage for basic regular upkeep and operating rehabilitation.

Massive restorations were regular, many times implicating disposal of the boiler from the frame for major rehabilitation. But a normal diesel locomotive needs only seven to eleven hours of maintenance and tune-ups every month; it may operate for several years on end between significant repairs. The Diesel locomotives don’t contaminate the environment unlike steam trains; modern units generate meagre degrees of exhaust emissions.

Fuel Cell Electric locomotive

Some railways and locomotive manufacturers have assessed the prospect of deploying fuel cell locomotives over the upcoming 15–30 years.

The principal 3.6 tons, 17 kW hydrogen (energy unit), in 2002 – controlled mining train was shown. It was smaller than normal by hydrail in Kaohsiung, Taiwan and was employed for service in 2007. The Rail-power GG20B is one more portrayal of a fuel cell electric train.

Environment change is expediting, and it’s time to limit carbon emissions from transportation—immediately.

The report, a study on the ‘Use of Fuel Cells and Hydrogen in the Rail Environment’, deduces that fuel cell trains will play a crucial part in the evolution of a zero-emission economy. In fact, the report states, by 2030, many recently bought train vehicles in Europe could be fueled by hydrogen.

Hydrogen-powered trains are stabilized to disrupt the rail industry as a zero-emission, cost-efficient, high-performance option to diesel.

A recent study exhibits hydrogen trains have actual commercial potential—but more labour has to be done around testing and boosting product availability for shunter and mainline cargo requisitions.

The market stake of fuel cell hydrogen trains may hike up to forty-one per cent by 2030 in Europe, given there are optimistic conditions for market growth and advancement. Ballard is dominating the industry in creating explicit rail solutions.

Advantages of fuel cell electric locomotive:

  • Flexible degrees of hybridization

Formulating composite layouts of batteries and fuel cells rail is crucial to enhance range and performance.

  • Composite fuel cell trains

It can deal with weights of 5,000 tonnes and can traverse at speeds about 180 km/h, completing a long- stretch span of about 700 km.

Adaptable assortments are accomplished by modifying the ratio of fuel cells to batteries.


  • Quickly refuelling, less downtime

Hydrogen-powered rail wagons are refuelled in much less than 20 minutes and can run for more than 18 hours without refuelling again.

  • No functional limitations of a 100% battery configuration

Battery-powered trains have substantial shortcomings, encompassing smaller range and heightened downtime required for restoring batteries. As a result, they’re only suitable for specific passages and routes, which considerably restrict rail operators.

Fuel cell-powered trains can perform effectively on a broader spectrum of paths, with virtually no downtime. Fuel cell trains make the most monetary sense when employed on lengthier non-electrified routes of over 100 km.

  • Lesser cumulative expense of operation

Not only is the catenary infrastructure for 100% electric trains costly to establish ($1-2 million per kilometre), it can also be expensive to regulate and sustain.

On the other hand, hydrogen trains have a promising less gross expense of operation.

A TCO analysis shows that hydrogen-powered trains are the least expensive option in relation to both diesel and catenary electrification when:

The price of diesel surpasses EUR 1.35 per litre.

The electricity rates are lower than EUR 50 per MWh.

  • Extremely high performance

They are just as adaptable and versatile as diesel locomotives with a similar range. They can bear with the requisites of rail transport just as well when diesel will be phased out.


Hybrid locomotives

A hybrid locomotive that utilizes an onboard rechargeable energy storage system (RESS), positioned between the power source (often a diesel engine main mover) and traction transmission system attached to the rotating wheels. Except for the storage battery, maximum diesel locomotives are diesel-electric, they have all the elements of a series hybrid transmission, making this a fairly simple possibility.

There are various kinds of crossbreeds or dual-mode locomotives employing more than two varieties of motive power.  Electro-diesel locomotives are the most prominent hybrids, fueled either by electricity supply or an onboard diesel engine. Hybrid locomotives are utilized to deliver continuous trips along paths that are only partially electrified. Some of the representatives of this category are the  Bombardier ALP-45DP and EMD FL9.

Some interesting fun facts

  • The longest direct locomotive route is found in Moscow.
  • Different types of locomotives can run on for various kinds of sources: – electricity, diesel, steam.
  • Today’s bullet trains can run at a maximum speed of 300 mph.
  • WAG – 9 is the most powerful cargo locomotive of the Indian Railways with a power output of 6120 horsepower and a maximum speed of 120 kmph.
  • The magnetic-levitation locomotive is presently the fastest in the world.
  • New York holds the record of having the greatest number of passenger platforms in one station.
  • Australia has the straightest path in the world.
  • Australia also holds the record of having the heaviest locomotive.
  • State-owned Chittaranjan Locomotive Works (CLW) has bestowed the Indian Railways its fastest ever engine. The altered WAP 5, which is yet to have a title, is anticipated to travel at 200 mph.
  • Seventy-five years ago, a world record, still unpaired, was accomplished by a steam engine called Mallard. For just two minutes, the locomotive thundered along at a speed of 126 miles per hour on a stretch of track, south of Grantham.
  • The Union Pacific locomotive called the “Big Boy” 4014 is the biggest locomotive ever built. It turned into Southern California after a huge restoration program.
  • The only country in the world which is without a railway is Iceland. Although there have been few railway systems in Iceland, the nation has never had a general railway network.
  • Diesel locomotives can run hundred and ten miles an hour.
  • On June 21, 2001, the record of the longest train ever pulled was set on, in Western Australia between Port Hedland and Newman, a length of 275km and the train includes 682 packed iron ore wagons and 8 GE AC6000 locomotives and moved 82,262 tonnes of ore, giving a total weight of nearly 100,000 tonnes
  • In the summer of 1912, the planet’s first diesel-powered locomotive was operated on the Winterthur–Roman’s horn railroad in Switzerland. In 1913, during additional test runs, many issues were discovered.
  • The AC6000CW is globally one of the most important and strong diesel locomotives having a single engine.
  • Indian Railways’ most powerful locomotive, the WAG12B has been assembled and has joined the network of Indian Railways. WAG12B is furnished with 12000 HP and has been developed in partnership with the French company Alstom.
  • There are approximately 12,147 locomotives in India.
  • The first locomotive of the world had a speed of 10mph.
  • The governing United States class one freight railroad company is BNSF Railway producing more than 23.5 billion U.S. dollars in operation income in 2019. The railroad concentrates on transferring freight products such as industrial, coal, cargo or agrarian commodities.
  • The longest and one of the most occupied railway lines in the world is the ld Trans-Siberian Railway (the Moscow-Vladivostok line), stretching a distance of 9,289km.

Working principle of a locomotive

Locomotives (commonly known as train “engines”) are the centre and essence of the Railway network. They give vitality to coaches and carriages, which are otherwise lifeless chunks of metal, by transforming them into trains. Locomotives working are established on a very easy tenet.

Be it electric or diesel, locomotives are really “run” by a bunch of electric AC induction engines called traction motors fastened to their axles. These motors need electricity to operate, and the source that delivers this power is what distinguishes between electric and diesel locomotives.

Traction motors are electric motors that are larger, sculpted, strengthened, more complex and important versions of the traditional electric induction motor seen in pump sets, electric fans etc. The electricity generated by the source is eventually provided to the traction motors, which operate and turn the wheels of the locomotive.

In addition to the energy output of the engine, the locomotive functioning also depends upon several other elements like top speed, traction effort, gear ratios, adhesion factors, the weight of the locomotive, axle load etc. They define the kind of assistance and function the locomotive will be employed for, whether for carrying passenger, cargo or both. This is applicable for both electric and diesel locomotives.

Nowadays all locomotives are microprocessor regulated which enable them to operate methodically and fruitfully. These computers regularly collect, compile and evaluate information to compute the optimum power needed by each axle of the locomotive for its top-notch performance according to the mass, speed, grade,  adhesion aspects and so forth.

They then provide the proper amount of power to corresponding traction motors. Fortifying this is all the supportive functions of the locomotive such as radiators, exhaust, batteries, braking and sanding equipment, dynamic brake resistors, advanced suspension cooling system etc.

Diesel Locomotives are essentially enormous self-propelled electricity generators. A “Diesel Locomotive” is a self-powered railway vehicle that runs along the rails and pushes or pulls a train affixed to it using a huge internal combustion engine running on Diesel fuel as the main mover or the fundamental supplier of power.

Though not like regular vehicles, modern diesel locomotives have no explicit mechanical relation between the wheels and the engine, hence the energy produced by the engine does not actually rotate the wheels. The objective of the diesel engine is not to move the train but to convert a big electricity generator/alternator generating an electric current (initially Direct Current, currently Alternating Current), which is passed through a rectifier to transform the AC to DC if needed. It is then disseminated to traction motors, which can further generate the actual (rotational) torque that rolls the locomotive’s wheels.

Thus, the role of the diesel engine is merely to produce power for the traction motors and auxiliary tools like blowers, compressors etc.

Maximum Indian diesel locomotives have three pairs of traction motors, one for each axle except the WDP4 with only two pairs of traction motors for three pairs of axles. Indian Railway engines have 16 cylinders in V arrangement (V16) except for a few of the lower-powered ones comprising the WDG5 which has a V20 engine and WDM2 with only 12 cylinders.

Unlike the conventional assumption, diesel locomotives are much more modern technology (1938) corresponding to electric (1881). Hence, electric locomotives function on the same precept as diesel locomotives. It wouldn’t be incorrect to say that diesel locomotives operate on electricity, which is why locomotives utilizing this scheme of operation are called “Diesel-Electric”, which encompasses all mainline diesel locomotives in India.

In earlier times there were locomotives which had the diesel engine directly steering the wheels through a bunch of gears like vehicles called the Diesel-Hydraulic locomotives. But, they were not only extremely complex but ineffective and problematic as well and were displaced by Diesel-Electric locomotive engines.

“Transmission” for locomotives, means the procedure or type of electricity disseminated from the engine to the traction motors. Some of the earlier locomotives had DC (Direct Current) transmission, but all the modern models have AC transmissions and all processes within the locomotive are regulated by computers.

The diesel locomotive is quite an intricate and refined piece of equipment. Diesel locomotives are incredibly autonomous, very adaptable, can run wherever and whenever as long as they have sufficient fuel in their tanks. A generator on wheels that elicits its electricity to drive itself!

How does diesel-hydraulic locomotive work?

Diesel-hydraulic locomotives are fairly rare as compared to diesel-electric but are extremely widespread in Germany. It is analogous in principle to a diesel-mechanical variety of locomotive, where the engine’s drive is transmitted by drive shafts and gears to each of the powered axles.

The difference is that instead of a transmission with many fixed ratios, a specialised torque converter is used. This increases torque exponentially as a function of the slip rate between the input and output shafts in a similar manner as that in a car with an automatic transmission. There will be a forward/reverse gearbox to enable the locomotive to run in both directions, but otherwise, no other gearing is wielded.

The major benefit, especially in the early days of diesel, was a pragmatic one. There were no high-voltage electrical networks to transmit power from the engine to the axles, and during the handover from steam to diesel, firms had a huge number of skilled and professional mechanical technicians, but few with HV electrical knowledge and expertise.

This made the keeping of diesel-hydraulics economical and frugal. The mechanical drive could also be theoretically more fruitful than transforming to electrical energy and back.

The disadvantage was more in the moving components as power had to be sent mechanically to each driven axle- diesel-electrics, where it could just have one motor on each axle driving it directly and more efficiently.

Nowadays, with the improvements and progress in electric engines and equipment enhancing the diesel-electric’s efficiency, along with a bigger number of electrical technicians, the diesel-hydraulic is an uncommon beast.

How do Electric Locomotives work?

An “Electric Locomotive” is a railway vehicle that employs electric power drawn from an exterior source to move along rails and pull or push a train fastened to it. This electricity is generally from a third rail or overhead cables.

Whether it is a standalone or the power cars of an EMU train set, all Electric Locomotives operate on the sole doctrine of outsourcing current from different sources and then after adequately altering it to provide the traction engines which spin the wheels.

This “modification” of the electric power is intended to supply the best leverage to the motors for flawless performance under various circumstances and loads, encompassing an arduous process of conversion, reconversion, voltage, smoothing and conversion of current to different magnitudes of frequency, using rectifiers/thyristors, banks of segments transformers, compressors, capacitors, invertors and other such components, lodged within the locomotive body.

It is this procedure of “modification” or adaptation that electric locomotive technology revolves around. One can say that the traction motors are the real ‘engines’ of the electric locomotive as electric locomotives do not have a main ‘engine’ or a primary mover drawing parallels to the diesel.

There are two ways in which electric locomotives can be categorised:

  • One is based on the kind of current they draw from the lines (traction power): AC (Alternating Current) or DC (Direct Current)
  • The other is defined as per the type of traction motors they employ (drives): Those with 3-phase Alternating Current (AC) traction motors or those with Direct Current (DC) traction motors. Both DC and AC motors can function on both DC and AC traction. The central purpose of all the equipment lodged in locomotives is to transform receiving electric power and to render it suitable for traction motors.

Diesel Locomotive Works (Varanasi)

The Banaras Locomotive Works (BLW) is a production unit of the Indian Railways. Banaras Locomotive Works (BLW) ceased the manufacturing of diesel locomotives in March 2019 and was rechristened BLW in Oct 2020.

Established in the early 1960s as the DLW, it launched its very first locomotive on the third of January 1964, three years after it’s launch. The Banaras Locomotive Works (BLW) manufactures locomotives which are models originating from the actual ALCO designs dating to the 1960s and the GM EMD designs of the 1990s.

In July 2006, DLW outsourced dealings of a few locomotives to the Parel Workshop, Central Railway, Mumbai. In 2016, it earned the “Best Production Unit Shield 2015-16” title. The first phase of the development undertaking of BLW was inaugurated in 2016.

In 2017, it again achieved the “Best Production Unit Shield 2016-17” for the 2nd consecutive year. In 2018, it accomplished the “Best Production Unit Shield 2017-18” of Indian Railways for the 3rd continuous year. In the same year, it successfully revamped two old ALCO diesel loco WDG3A into an electric loco WAGC3, the first the all over the globe.

Diesel Locomotive Works (DLW) was the biggest diesel-electric locomotive manufacturer in India. In 2020, it formulated the nation’s first bi-mode locomotive, the WDAP-5. BLW today manufactures primarily electric locomotives WAP-7 & WAG.

Moreover, the Indian Railways, BLW periodically ships locomotives to various territories like Mali, Sri Lanka, Senegal, Vietnam, Bangladesh, Nepal, Tanzania and Angola, also some manufacturers within India, such as steel plants, large power ports and private railways.

Advantages of Diesel Locomotive over Steam Locomotive

  • They can be run safely by one person, making them suitable for switching and shunting duties in yards. The working atmosphere is smoother, totally waterproof and free of dirt and fire, and much more appealing, which is an unavoidable part of the steam locomotive service.
  • Diesel locomotives may be run in multiples with a single crew operating several locomotives in a single train – something not feasible with steam locomotives.
  • As the diesel engine can be switched on and off instantly, there is no wastage of fuel that could happen if the engine was kept on idle to save time.
  • The diesel engine can be left unattended for hours or even days, because almost any diesel engine used in locomotives has systems that shut down the engine if there are problems automatically.
  • Modern diesel engines are engineered to allow the control assemblies to be removed while retaining the main block in the locomotive. This dramatically decreases the time the locomotive is out of revenue-generating operations while maintenance is needed.

Prerequisites to be filled by an ideal diesel locomotive are:

  • The diesel locomotives should be able to exert a huge amount of torque on the axles so as to pull heavier load.
  • It should be able to cover a very wide speed range, and
  • It should be capable of running with ease in both directions.
  • It is fitting to add an intermediate device between the wheels of the locomotive and the diesel engine to satisfy the above operating requirements of the locomotive.

Diesel locomotive disadvantages

No matter how ubiquitous general motor diesel locomotives are, diesel engines have the following drawbacks:

  • It cannot start on its own.
  • It must be cranked at a certain speed, known as the starting speed, to start the engine.
  • The engine cannot be run at anything less than the lower critical speed which is supposed to be 40% of the rated speed on a usual basis. The definition of this speed entails when there is no exhaust released or vibrations caused.
  • The engine cannot function above an abnormal speed limit called the high critical speed. It is supposed to be about 115% of the rated speed. The definition of this speed entails the rate at which the engine cannot operate without self-damage due to thermal loading and other centrifugal forces.
  • Regardless of its rpm, it is a constant torque motor for a specific fuel environment. Only at rated speed and fuel setting can it develop rated power.
  • It is unidirectional.
  • The motor has to be shut down to de-clutch control, or a separate mechanism has to be added.

With all the limitations listed above, a transmission should accept whatever the diesel engine provides and be able to feed the axles in such a way that the locomotive meets the requirements.

Any transmission should fulfil the following requirements:

  • It must relay to the wheels the power from the diesel engine.
  • It must have a provision for connecting and disconnecting the engine from the axles for the locomotive to start and stop.
  • It must include a mechanism for reversing the locomotive’s direction of motion.
  • As the axle speeds are usually very low compared to the speed of the crankshaft of the diesel engine, it must have a permanent speed reduction.
  • In the beginning, it must have a high torque multiplication, which should progressively drop as the vehicle speeds up and vice versa.

The requirements of traction

  • For a jerk free and smooth start, the traction requires a high torque at zero speed.
  • Torque should decrease rapidly, uniformly, and the speed should increase with high acceleration once the train is started.
  • Depending on the road conditions, the speed and power characteristics can adjust automatically & uniformly to ensure that the power transmission is jerk-free.
  • With equal speed and torque characteristics, the power transmission should be reversible, with simple reversibility in both directions.
  • Whenever needed, there should be a power de-clutching provision.

Ideal use of a diesel locomotive transmission

The transmission of the engine should be capable of increasing the torque and reducing the speed to such a degree that it is possible to start the train without a jerk. It should decrease substantially the torque and increase the speed as required when the train has started. The torque & speed specifications of the traction should be consistently varied, depending on the road requirements, so that the power transmission is jerk-free.

With equal torque & speed specifications in both directions, it should be able to reverse the power transmission quickly. It should be light, robust, and there should be very little space to fill it. It should be right and minimal maintenance should be needed. It should be conveniently accessible for maintenance and ask for low minimum consumable quantities.

The obligation of the ideal transmission is that road shocks and vibrations should not be transmitted to the engine. It should have better performance, a good consumption factor, and a good degree of transmission. It should, if necessary, be able to start the engine. And it should be capable of applying brakes if necessary.

Factors relating to diesel-locomotive efficiency

  • Power Utilisation Factor

When viewed as a constant torque engine, the diesel engine is only able to produce its full-rated horsepower when operating at its maximum speed and maximum fuel configuration. The engine must therefore always run at its optimum speed with full fuel configuration to use its full power from zero to a hundred percent of vehicle speed. But in actual reality, this isn’t the case.

The engine speed is directly controlled by the inherent characteristics of the transmission when the engine is connected to the wheels via a transmission mechanism such as a coupling or a multi-stage gearbox, and therefore its strength varies proportionately. The ratio between the horsepower input to the transmission at any moment of the vehicle speed in peak notch service and the maximum horsepower mounted at the site conditions is known as the factor of power utilization.

  • Transmission efficiency

This is known as the ratio at any vehicle speed between the rail horsepower and horsepower input to the transmission.

  • Degree of transmission

In choosing a transmission system for a diesel locomotive, this is a very important consideration. This is established as a result of the power utilization factor and the efficiency of transmission. This is the ratio between the rail horsepower at any moment and the built horsepower at the station, in other words.

Diesel Locomotive Maintenance Manual

In the year 1978, the Indian Railways Maintenance Manual was released for Diesel Locomotive, widely referred to as the “White Manual.” Since then, a variety of technical developments have been made, such as the diesel loco design has been integrated with MBCS, MCBG, PTLOC, Moatti filters, Centrifuges, Air dryers, RSB, mechanically bonded radiator cores, AC motors, bag style air intake filters, upgraded compressors and much more.

These technologically superior locos have a different requirement for maintenance from old conventional locos. The number of diesel locos installed in diesel sheds has multiplied at about the same time, causing different organisations to be created.

A radical change in maintenance philosophy has mandated the installation of such advanced diesel locos on Indian Railways, preserving the essence of mature expertise acquired from years of experience.

This White Manual supplements transport engineers’ long-standing need not only to provide a recorded collection of directions and guidance in line with the current scenario but also to serve as a herald in their search for expertise.

However, the idea of predictive maintenance needs to be adopted by IR to reduce both cost and maintenance downtime. To accomplish this, a list of criteria that need to be remotely monitored and also paid to decide on the next schedule to be given to the loco during the last shed attention must be created. In achieving this aim, remote monitoring is an important requirement. It is proposed that on the predictive maintenance scheme, few locos should be put on trial.

Diesel-locomotive electric maintenance

Very little is involved in the repair of electrical equipment. It is limited to the analysis and inspection of the control cubicle of the brushes and commutators. The minimum time between checks is one month and the duration is approximately four hours. Generally speaking, accepting that the design is capable of improvement is to suggest that a piece of equipment needs modification or inspection at any given time. In certain situations, without any rise in costs, this enhancement can be accomplished. Of course, it is understood that unforeseeable problems can occur, and these must be recognized before they lead to serious outcomes.

Monthly inspection of commutators and brush gear can be assumed to be in this group, but it cannot be agreed that it is appropriate to consider mechanical or electrical issues due to the loose operation of nuts or other fixing arrangements. Total reliability in this regard can be assured. There is no reason why the control equipment should need attention more often than every six months, assuming this is so, and that the different contactors and relays are up to their job. A piece of control equipment has to be worked without any attention for more than this period to test this theory, and the schedule is being progressively adjusted accordingly.

Properly engineered roller bearings can operate for at least three years without re-greasing unless exposed to high temperatures. Self-oiling bushes are capable of removing control gear lubrication. If left alone contacts that break the current should work satisfactorily for at least six months. The silver-faced, cam-operated, butt type should have small contacts. While providing the required ventilation, it is worth going through considerable trouble to remove dust. Careful consideration is paid to maintaining the starting-battery motor. There are satisfactory findings from various workshops with either lead-acid or alkaline batteries, and there is no significant difference between their annual costs. Lead acid batteries are far superior in many respects.

The expense is not as much due to the time spent on the actual job as opposed to the long time it may take to travel. For the same cause, the simplest failure could entail a substantial waste of time by the electrician and, more importantly, a loss of locomotive availability. It stresses the need for continuity, which can be accomplished by simplicity and attention to every detail in architecture.

Unique problems occur in connection with the diesel engine, and the performance of the diesel traction depends on its satisfactory solution. As far as the design attention is concerned, it can be approached in the same manner as electrical equipment, but it is clear that the mechanical and thermal issues to be solved are more precise, and the effects of a failure can be catastrophic. Besides, a greater degree of precision is necessary than in the case of the steam locomotive. Again, unless there is a minimum of eight to ten locomotives involved, a full-time fitter is not justified.

This points again to the need for a stable and simple design. The Diesel engine can be divided into the following sections for consideration of what is involved:

 (a) Very heavily loaded surfaces sliding at large speeds-bearings, pistons, rings, etc.

 (b) Valves and working gear of the valve.

 (c) The process to rule.

 (d) Pumps and injectors for injections.

The standard rate of wear, also the permissible wear, has been identified with the first three items; hence, in general, these items can be forgotten for at least three or four years.

Bearings, where any indication of discomfort is displayed by the white metal, are removed, although this is seldom required. Only three main and nine large-end bearings have been replaced in the running sheds over the last four years, with an average of around 40 locomotives in operation. None of these were in a hazardous state but were identified during periodic inspections.

Big-end bolts and crankshaft alignment are the most critical items to watch from the point of view of avoiding serious trouble, as influenced by the potential loss or undue wear of the main bearing. The large-end bolts are pulled up to an extension of 0-009 and are tested after one month of running to this dimension. A clock micrometer between the webs controls the crankshaft orientation as the crankshaft is pressed down onto the bottom halves of the main bearings with special jacks.

Whether mileage, hours of operation, engine revolutions or fuel consumed should be used as a basis for maintenance cycles is a point of interest. It is noticed that mileage is most convenient when the locomotives are engaged in identical shunting tasks.

The infrastructure of diesel locomotive sheds in India

 Shed layout is defined as a plan for an optimal arrangement to include all facilities, including maintenance dock, types of equipment, storage capacity, material handling equipment, and all other support services, at the same time as the most acceptable structure is planned.

Locomotive shed in India
Image credits: https://www.thehindubusinessline.com/economy/logistics/xh3964/article30469950.ece/ALTERNATES/LANDSCAPE_1200/Wabtecs-locomotivesjpg

The goals of Shed Layout are:
a) streamline the flow of loco and materials through the shed,
b) encourage the repair procedure,
c) reduce the cost of material handling,
d) efficient use of personnel,
e) equipment and room,
f) make effective use of compact space,
g) versatility of operational processes and arrangements,
h) provide employees with ease,
i) security and comfort,
j) minimise the overall time for loco schedules, and
k) maintain organisation structure, etc.

Size and Location of a Maintenance Shed

The prime factors that determine the location and size of a maintenance shed are the prevalent operating conditions. However, it is not necessary to provide sheds at points that correspond with broad traffic yards due to the versatility in service available from diesel locos. If a shed is situated close to a train examination or crew changing stage, it will be enough.

While selecting shed locations, due consideration should be paid to possible future improvements in the technology such as traction mode, the transition from diesel to power transmission. If any traction change takes place, the characteristics of all new and old kinds of traction should be evaluated in a consolidated way, both in terms of the location and size of the shed.

From a technological perspective, the size of a maintenance shed is optimal when the maintenance performance is reliable and effective. Experience has shown that there is a requirement for this personalized focus. Also, during minor maintenance schedules, the complete history of and loco should be readily accessible in the homing shed so that locos requiring further care can be selectively nursed.

Good communication facilities for efficient maintenance should be provided to the maintenance shed. In the case of emergencies, strong communication connections with major industrial centers help to coordinate supplies and components at short notice. From an effective maintenance point of view, all repair schedules M2 (60 days) and higher are invariably carried out in the home shed.

Special Examination of Stressed Parts

The failure of certain parts of the Diesel engine may be attended by serious consequences. Though the possibility is extremely remote, it is considered desirable to examine certain parts when the locomotives are going through the shops. For example, crankshafts, connecting rods, big-end bolts, valve stems, and valve springs are subjected to magnetic crack detection.

In a sample examination, six big-end bolts have shown longitudinal cracks that were not serious and were quite possibly present when new. One valve stem has been found with a transverse crack near the head. Such examinations are even more important on engines on main-line units, where parts are likely to be more highly stressed, and for longer periods than on shunting engines.

Diesel Locomotive Fuel Capacity

Fuel is a significant component of spending on locomotive operations. Therefore, fuel efficiency is a significant factor in bringing down running costs. To avoid loss due to spillage and overfilling of tanks, proper consideration must be paid to the handling of fuel oil. Also, a proper foolproof scheme for the receipt and issue of fuel accounting is in place to take different managerial decisions on records.

On a diesel locomotive, the fuel injection equipment is designed to fine tolerances. Problems in the diesel engine could be caused due to contamination in fuel. Whilst the oil company must deliver commercially clean fuel oil as needed, it is the duty of the loco employees to ensure that water, dirt, gravel, soil, etc. are not contaminated in any way during its handling.

The related features of both locomotive engines are described below. Both engines operate on diesel fuel and are fitted with 16 cylinders in the 45o V segment. One with steel plates is created by the engine and the wet cylinder liners are inserted into the cylinder blocks. The injection of fuel is directly into the cylinder and has one fuel injector pump per cylinder. They essentially have mechanical fuel injection, but there is integrated unit fuel injection in the EMD engine. The turbo supercharger has an intercooler that provides between 1.5 and 2.2 bars of air.

The cylinder liners are wet and have nitrided bearings in the cast alloy crankshaft. Camshafts have replaceable parts with larger diameter lobes and if they are stopped for 48 hours or more, the engines need pre-lubrication.

The components of a diesel-electric engine are:

  • Diesel engine
  • Fuel tank
  • Traction motor
  • Main alternator and auxiliary alternator
  • Turbocharger
  • Gearbox
  • Air compressor
  • Radiator
  • Truck frame
  • Rectifiers/inverters
  • Wheels
Locomotive components
Image credits: https://www.trains.com/
Feature ALCO GM ( EMD) Remarks
Model 251 B, C GT 710 ALCO – 4 Stroke technology GT 710 – 2 stroke technology
Fuel Injector Separate Fuel Pump and Injector Combined Pump and Injector(Unit injection) The high pressure hose connecting the the pump to the injector is eliminated. Thus on line failures are reduced
Cylinder Capacity 668 cubic inches 710 cubic inches Higher cc leads to higher power generation per cylinder
Bore and Stroke Bore 9”, Stroke 10.5” - -
Compression Ratio (CR) 12:1, 12.5:1 16:1 Higher CR leads to higher thermal efficiency
Brake mean effective pressure 13-18 bar Continuous and 4-20 bar standby - -
Turbo supercharger Purely Exhaust driven Initially mechanical drive from engine , later driven by exhaust gas at 538oC In EMD locos we do not find black smoke during initial cranking as the excess air is supplied by turbo for complete combustion of fuel.
Cylinder liners Open grain chrome plated liners - Open grain liners ensure adequate oil film thickness yielding low wear rates and low lube oil consumption
Cylinder head Steel Casing - Stronger casting keeps thermal distortion and mechanical deflection to minimum.
Engine 4 stroke 2 stroke 4 stroke has better thermal efficiency as compared to 2 strokes. 2 stroke engines are easier to crank and start.
Piston Super bowl - Better combustion, increased fuel efficiency.
Valves 2 Valves for Inlet and 2 for Exhaust Inlet ports and exhaust 4 valves There are 2 valves for intake and 2 valves for exhaust in ALCO. In EMD locos 2 valves are for exhaust alone.
Valve operation Push rod Overhead camshaft (OHC) OHC eliminates long pushrods and hence the noise, friction and failures due to push rods are reduced.
Feature ALCO GM ( EMD) Remarks
Engine starting The battery drives the auxiliary generator 2 DC motors with bendix drives which rotate the ring gear on flywheel Easy to start as the two starter motors produce enough torque to crank the engine.
Radiator Floor Mounted Slanted and Roof mounted Easy Maintenance. No coolant stored in radiator tubes when at rest.
Radiator bonding Soldered Mechanically bonded- Stronger Mechanically bonded radiators are stronger than soldered ones and also give better reliability in service.
Specific fuel consumption 160 gm/kWh 156 gm/kWh SFC are very close and in tune with technology in vogue.
Engine rpm maximum 1000 904 Higher rpm results in higher power output with other parameters being the same.
Idle rpm 400 250 Low rpm results in low noise, reduced fuel consumption.
Low idle feature Not available 205 rpm when the the notch is at Zero Low idle feature ensures lean fuel consumption during idling.
Radiator Fan Eddy Current Clutch 86 hp AC motor Less power consumption by auxiliaries.
Maintenance Every fortnight Every three months Higher maintenance periodicity ensures greater availability of loco for traffic use.
Cylinder Capacity - 710 cubic Inches -
Scavenging NA Uniflow scavenging Uniflow scavenging results in better scavenging when compared with conventional 2 stroke engines.
Power Pulse Every 45° Every 22.5° EMD engines develop smooth power, torque and thus less vibrations.
Feature ALCO GM ( EMD) Remarks
Engine Design - Narrow V type -
Crankcase Ventilation Dc motor Blower Eductor System, Mechanical Venturi Eductor system employs venturi system and hence no power is consumed
Air box - Available with Positive pressure The air pressure in air box is positive and above atmospheric pressure.
Crankshaft One piece forged Two piece drop forged joined by flange at centre ( 5 and 6 main bearing) Crankshaft manufacturing cost and complexity is reduced by having a 2 piece crank shaft.
Power Pack - Consists of Cylinder, Cylinder head, piston, carrier and CR Allows dismounting and replacement of the entire power pack.
Piston Forged steel piston crown bolted. Cast Iron alloy phosphate coated -

GE locomotives

While diesel locomotives first arrived in the 1920s on American railroads, the purpose was limited to engine switches, and then to locomotives for passenger trains. It was not until 1940 that the Electro-Motive Division of General Motors (EMD) proved that diesel was virtually able to replace heavy-duty steam locomotives. A pioneer of diesel freight, the “FT,” model, toured the railroads of the nation and changed history. It was styled with a nose and windshield, just like an automobile identical to its sister passenger locomotives of the day; a design that persisted until the late 1950s.

The locomotives are electrically driven, although generally referred to as ‘diesel.’ An alternator powers the diesel engine, which generates electricity to power electric motors mounted on the axles of the locomotive. A dramatic increase in performance over the steam locomotive was the internal combustion engine, allowing huge savings in maintenance and the removal of installations possible.

The fastest locomotive in India

The Indian Railways have been given their fastest ever engine by the state-owned Chittaranjan Locomotive Works (CLW). It is estimated that the updated WAP 5, which still does not have a tag, will travel 200 kmph. It also comes with enhanced aerodynamics and has an ergonomic design that takes care of the comfort and protection of the driver.

The series’ first engine was sent to Ghaziabad, its likely future base. Trains such as the Rajdhani Express, Gatimaan Express, and Shatabdi Express are likely to be used for transport. For these trains, it would cut travel and turnaround time.

Railways have been trying to improve their trains’ average speed. Besides the planned bullet train project and the latest T-18 train, the new engine built by CLW is a step in that direction. The WAP 5 version produces 5400 HP and has a rearranged gear ratio.

The engine has CCTV cameras and voice recorders in the cockpit that will record contact between the driving team members. The recordings will be saved for 90 days and can be analyzed in the event of incidents and emergencies, helping to provide a clear image of what occurred. Owing to a next-generation regenerative braking system, this engine can use less energy than its predecessors.

The new engine was designed at a cost of approximately Rs 13 crore. The new design will, however, help trains reach higher speeds. In addition to decreasing the enormous fuel import bill, the emphasis on electric motors would help decrease the use of diesel and thus decrease the carbon footprint.

First diesel locomotive in India

On 3 Feb. 1925, the first electric train began on the 1500 V DC System from Mumbai Victoria Terminus to Kurla Harbour. It was the pivotal moment for Mumbai City, as well as for other metropolitan cities, in the construction of the railways and the growth of the suburban transport system. In the Southern Railway on 11 May 1931, the Madras was the second metro city to get electric traction. India had only 388 rkm of electrified tracks up to Independence.


The Howrah Burdwan section was electrified after independence at 3000 V DC. On 14 Dec. 1957, Pandit Jawahar Lal Nehru began EMU services in the Howrah-Sheoraphuli section.

At Chittaranjan Loco-motive Works (CLW) in 1960, the construction of electric locomotives was simultaneously taken up indigenously and the first 1500 V DC electric locomotive for Bombay Region Lokmanya was flagged off on 14 Oct. 1961 by Pt. Jawahar Lal Nehru, India’s first PM.

F7 Locomotive for sale

The EMD F7 is a diesel-electric locomotive with 1,500 horsepower (1,100 kW) built by the Electro-Motive Division of General Motors (EMD) and General Motors Diesel between February 1949 and December 1953. (GMD).

F7 was often used as a passenger service hauling train in the models like the Super Chief and El Capitan of the Santa Fe Railway, even when it was originally marketed as a freight-hauling unit by the EMD.

The model debuted immediately after the F3 in the late 1940s and railroads rapidly placed orders for the F7 with EMD’s popularity in the market up to that point. The new F model, once again, proved to be effective, robust, and easy to maintain.

Almost 4,000 units were manufactured on the F7 before production had ended, outselling all the prototypes of all other manufacturers combined. For several railways, the F7 proved so reliable and useful that, through the 1970s and 1980s, hundreds remained in daily freight operation.

Today, numerous F7s remain preserved (partially because it is the last large-scale model of its kind) and some even continue to transport freight, a true testimony to their nature. A fleet operated by Class I Norfolk Southern is the most prominent set (a pair of B units) used as part of its official business train.

F7 Locomotive for sale
Image credits: https://upload.wikimedia.org/wikipedia/commons/1/1d/ATSF_309_%28Flickr_22322834666%29.jpg

A high reliability factor and easy maintenance model; a set of F7s, coupled with a matching 1,500 horsepower B unit, could double the train’s power to 3,000 hp. In principle, whether at the head-end or cut-in throughout the line, you might equip as many Fs to one single train as you wish.

The first true “common” diesel locomotive of its day, the SD40-2, was the EMD F7; thousands were produced and could be found powering nearly any train. When production ended, some 2,366 F7As were produced and 1,483 F7Bs were manufactured only four years after the locomotive was first cataloged in 1953.

For the new Electro-Motive Division, this was also the first instance of the new General Motors Diesel (GMD) subsidiary filling orders. The new factory, located in London, Ontario, has made it much easier for Canadian lines to sell locomotives.

In all, for its line in Southern Ontario between Detroit and Niagara Falls/Buffalo, New York, GMD sold 127 examples to the Canadian National, Canadian Pacific, and the Wabash.

In the F series, the model was EMD’s most successful since no other future design ever came close to matching the sales figures of the F7.

The EMD F7’s robustness and reliability can be seen at present as several remain and continue to operate with a subset of freight trains, especially on short-line Grafton & Upton (now contained) and Keokuk Junction Railway (two FP9A’s and one F9B).

There are still places where one can find f7s, they are:

  • Conway Scenic Railway
  • Reading Company Technical & Historical Society
  • Adirondack Scenic Railroad
  • Royal Gorge Railroad
  • Illinois Railway Museum
  • Potomac Eagle Scenic Railroad
  • Fillmore & Western

Functional Principles and Working of Locomotives

Diesel Locomotive



  • Diesel engine

A diesel engine is the primary source of strength for a locomotive. It consists of a wide cylinder block, with cylinders arranged in a straight line or in a V. The engine rotates the drive shaft at up to 1,000 rpm, which drives the different components used to power the locomotive. As the transmission is usually electrical, the generator is used as the power source for the alternator that provides electrical energy.

  • Main alternator

The engine powers the main alternator that provides the power to propel the train. The alternator produces AC electricity that is used to provide power to the traction motors on the trucks. The alternator in previous locomotives was a DC unit referred to as a generator. It generated direct current that was used to supply power to DC traction engines.


  • Auxiliary alternator

Locomotives used to handle commuter trains shall be fitted with an auxiliary alternator. It includes AC power for lighting, ventilation, air conditioning, seating, etc. on the train. The output is conveyed via the auxiliary power line along the train.

  • Air intakes

The air to cool the engines of the locomotive is drawn from outside the locomotive. It must be purified to eliminate dust and other impurities and its flow controlled by temperature, both inside and outside the locomotive. The air control system must take into account the broad range of temperatures from the possible +40°C of summer to the possible-40°C of winter.

Electric Locomotives



  • Inverters

The output from the main alternator is AC, although it can be used in locomotives with DC or AC traction motors. DC engines have been the conventional type used for several years, but AC engines have been standard for modern locomotives within the last 10 years. They are easier to install and cost less to operate, and they can be very precisely managed by electronic managers.

Correctors are required to convert the AC output from the main alternator to DC. If the engines are DC, the output of the rectifiers is used directly. If the engines are AC, the DC output of the rectifiers is converted to 3-phase AC for the traction motors.

If one inverter dies, the machine is only capable of generating 50% of the traction effort.


  • Electronic controls

Almost every section of the current locomotive machinery has some sort of electronic control. These are normally collected in a control cab near the cab for easier access. Controls will typically provide a maintenance management system of some kind that can be used to download data to a compact or mobile device.

  • Traction motor

As the diesel-electric locomotive uses an electrical transmission, the traction motors are given on the axles to give the final drive. These engines have historically been DC, but the advancement of modern power and control electronics has led to the advent of 3-phase AC motors. The majority of diesel-electric locomotives have between four and six cylinders. A new air flowing AC engine provides up to 1000 hp.


It’s almost straight since the coupling is normally a fluid coupling to give some slip. Higher speed locomotives use two to three torque converters in a series similar to gear shifts in a mechanical transmission and others use a mix of torque converters and gears. Any versions of diesel-hydraulic locomotives had two diesel engines and two transmission systems for each tank.


  • Fluid coupling

In a diesel-mechanical transmission, the primary drive shaft is connected to the engine using a fluid coupling. This is a hydraulic clutch, consisting of an oil-filled case, a spinning disk with curved blades driven by the motor, and another one attached to the road wheels.

When the motor spins the fan, one disk pushes the oil into the other. In the case of a diesel-mechanical transmission, the primary drive shaft is attached to the engine using a fluid coupling. This is a hydraulic clutch, consisting of an oil-filled case, a rotating disk with curved blades driven by the engine, and another one connected to the road wheels. As the engine turns the fan, one disk moves the oil on the other disk.

Some common locomotive engine parts


  • Batteries

A diesel loco engine uses a loco battery to start and power the lights and controls while the engine is turned off and the alternator is not working.

  • Air reservoirs

Air reservoirs containing compressed air at high pressure are needed for train braking and certain other locomotive systems. They are installed next to the fuel tank under the locomotive floor.

  • Gear

The gear can be varied from 3 to 1 in the case of freight engine and 4 to 1 for mixed locomotives.

  • Air compressor

The air compressor is needed to provide the locomotive and train brakes with a continuous supply of compressed air.

  • Drive shaft

The main output of the diesel engine is transferred by the driveshaft to the turbines at one end and the radiator fans and the compressor at the other end.

  • Sandbox

Locomotives often bring sand to aid in the adhesion of poor rail weather.

Diesel Engine Types

There are two types of diesel engines based on the number of piston movements needed to complete each cycle of operation.

  • Two-stroke engine

The easiest one is the two-stroke engine. It doesn’t have any valves.

The exhaust from the combustion and the fuel-efficient stroke is drawn in through the holes of the cylinder wall as the piston hits the bottom of the downstroke. Compression and combustion happen during the upheaval.

  • Four-stroke engine

The four-stroke engine functions as follows: downstroke 1-air intake, upstroke 1-compression, downstroke 2-power, upstroke 2-exhaust. Valves are required for intake and exhaust air, normally two for each. In this respect, it is more similar to the current petrol engine than the two-stroke design.

Diesel engine types
Diesel two stroke engine & four stroke engine

Engine Ignition


The diesel engine is started by turning over the crankshaft before the cylinders begin to burn. The start may be achieved electrically or pneumatically. Pneumatic starters have been used by some engines. The compressed air is pumped into the engine cylinders until there is adequate speed to allow ignition, and then the fuel is used to start the engine. The compressed air is provided by an auxiliary engine or by high-pressure air cylinders borne by the locomotive.


Electric start is now standard. It operates the same way as in the case of a vehicle, with batteries supplying the power to switch the starter motor, which turns over the main engine.

Engine Monitoring


When the diesel engine is working, the engine speed is tracked and controlled by the governor. The governor ensures that the engine speed remains high enough to idle at the proper speed and that the engine speed does not increase too much when maximum power is needed. The governor is a basic mechanism that first appeared on steam engines. It runs on a diesel engine. Modern diesel engines use an integrated governor system that satisfies the specifications of the mechanical system.

Fuel Control


In the petrol engine, the strength is regulated by the quantity of fuel/air mixture added to the cylinder. The combination is mixed outside the cylinder and then added to the throttle valve. In a diesel engine, the volume of air supplied to the cylinder is constant, such that the power is controlled by changing the fuel supply. The fine spray of fuel pumped into each cylinder must be controlled so that the quantity can be achieved.

The volume of fuel used on the cylinders varies by modifying the efficient distribution rate of the piston in the injection pumps.

Locomotive fuel governor

Each injector has its own pump, powered by a motor-driven cam, and the pumps are arranged in a row so that they can all be adjusted together; modification is made by a toothed rack called a fuel rack, operating on a toothed portion of the pump system. When the fuel rack moves, the toothed portion of the pump rotates and allows the pump piston to travel around within the pump. Moving the piston round alters the size of the channel open within the pump so that the fuel will flow through to the transmission pipe of the injector.

Engine Power Control


The diesel engine in the diesel-electric locomotive supplies the main alternator with the power needed for the traction engine similarly ed by the diesel engine is also connected to the power required by the generators. To get more fuel out of the generators, get more power out of the alternator so the generator has to work harder to produce it. Therefore, to achieve maximum output from the locomotive, we must relate the control of the diesel engine power requirements of the alternator.

Electrical fuel injection control is another improvement that has already been implemented for modern engines. Overheating can be controlled by electronic monitoring of the temperature of the coolant and by changing the engine power accordingly. The oil pressure can be controlled and used to manage engine power similarly.


Just as a motor car, the diesel engine must run at an optimal temperature for the best possible performance. Before it starts, it’s too cold, and when it’s running, it’s not allowed to get too hot. A cooling mechanism is provided to keep the temperature constant. It consists of a water-based coolant that circulates around the engine core, keeping the coolant cool by moving it through the radiator.


Like a motor, a diesel engine has to be lubricated. There is an oil tank, generally held in the sump, which must be held filled up, and a pump to keep the oil flowing uniformly around the piston.

The oil is warm by its movement around the engine and must be kept cold so that it passes through the radiator on its travel. The radiator is often equipped as a heat exchanger, where the oil flows into pipes sealed in a water tank that is attached to the engine cooling system. The oil must be filtered to eliminate impurities and monitored for low pressure.

If the oil pressure decreases to a degree that might cause the engine to seize, the “low oil pressure switch” will shut down the engine. There is also a high-pressure escape valve to pump the extra oil down to the sump.

Nomenclature of Locomotives

To identify each locomotive, a certain nomenclature is to be followed by the Indian Railways. The nomenclature system helps to identify various features of the engine and its model as well. The complete name of a locomotive is divided into two parts. The prefix of the code denotes the class of the locomotive or its type. The second part of the numeric suffix represents the model number of the engine. Before the discovery of liquid fuel, one needed only a letter to represent the type of the locomotive.

The meaning of each letter used in the code of the locomotives has been described below.

The first letter

It is used to represent the track gauge for which the engine can be used. There are four variants of the first letter in the nomenclature of locomotives.

  • Broad gauge: W. The broad-gauge track can range up to 1676 mm.
  • Metre gauge: It is represented with a Y.
  • Narrow gauge: Narrow gauge measures to be 2’6’’.
  • Toy gauge: It has a measure of 2’.

The second letter

The second letter is used to represent the fuel system that is used in the engine. During the time of steam engines, this letter was not included in the nomenclature as there was only one possible fuel to be used. The following letters are used to represent different types of fuels that are used in the locomotives in India.

  • Diesel locomotive:
  • DC overhead line for electric locomotive: C. It denotes that the locomotive runs on 1500V of direct current.
  • AC overhead line for electric engine: It runs on a 25kV 50 Hz alternating current.
  • For AC or DC overhead line: Found only in the Mumbai region, this type of locomotive uses 25kV AC power. Note that CA is considered as a single letter.
  • Battery Engine: B.
  • The third letter: This letter is used to represent the function for which the locomotive is aimed. The letter gives an idea about what kind of load the engine is best suited for. These letters are as follows.
  • Goods train: These include freight trains and others used to carry heavy goods.
  • Passenger train: These include express, mail, passenger trains, locals, etc.
  • Goods and Passenger trains (Mixed): M.
  • Shunting or switching: These trains are low powered.
  • Multiple units (diesel or electric): U. Such locomotive engines do not have a separate motor. The motor is included in the rake.
  • Railcar:

The fourth letter

The letter or number represents the class of the locomotive engine. It is used to classify the engine based on its power or version. For diesel and electric engines, a number along with its power. For example, WDM3A represents a broad-gauge diesel engine that is used to carry both passengers and goods and has a power of 3000 horsepower.

The fifth letter

The last letter is for the subtype of the locomotive engine. They represent power rating for diesel engines and for all the others, it represents the variant or model number. Such as in the above example, you can see that the letter A represents that the horsepower is enhanced by 100 horsepower. The letters used are explained below.

  • Addition of 100 horsepower: A.
  • Addition of 200 horsepower: B.
  • Addition of 300 horsepower:

And so on. Note that these letters are applicable for diesel engines only. In some newer engines, this letter can represent the brake system used in the locomotive.

For example, the first diesel locomotive used in India, that is WDM-2 represents that it is used for broad gauge (W), encompasses diesel as fuel (D), and is used to carry passengers and goods (M). The number 2 represents the generation of the locomotive. They are preceded by WDM-1. WDM-1 had to be reversed as it only had the driver’s cab at one end. At the other end, it was flat.

Though, for WDM-2, the structure was changed such that the driver’s cab was present at both the ends. Such a structure can delete the need of reversing the engine. These locomotive engines are manufactured in BLW (Banaras Locomotive Works), Varanasi. They were licensed under ALCO (American Locomotive Company). Similarly, the passenger class locomotive, WDP-1, is a broad-gauge passenger train of generation one. The nomenclature has eased the process of classifying different types of locomotives used across India. 

Locomotive in India

As of the recent data, there are more than 6000 diesel locomotives in India. India has replaced more than half of its locomotives fleet with electric engines, which amount to 6059 as per the count that took place during the fiscal year of 2019. These locomotives are classified among the following series.

Diesel Locomotive in India

WDM Series (ALCO)

Locomotive in India
Image credits: https://qph.fs.quoracdn.net/main-qimg-36daac7effcd3fd405cdaba22e2de300



The first diesel locomotive that came to India was manufactured under ALCO’s DL500 World Series. It was a 12-Cylinder 4-Stroke engine with a power output of 1900 horsepower. The units had an issue with their requirement of frequent reversing due to the driver’s cab present at one side only. Only 100 such models were produced. They had a Co-Co wheel arrangement and could acquire a speed of 100 kph. They were based in Gorakhpur, Patratu, Vizag, Rourkela, and Gonda.

Some of these engines were in service until 2000, though now most have been scrapped. One can find this version of the diesel locomotive still in use in some areas of Pakistan, Sri Lanka, Greece, etc.

One of the models is added to the collection of the National Rail Museum in New Delhi.



This second-generation diesel locomotive aimed for passengers and goods and to be used on a broad gauge line; it had a 12-Cylinder and 4-Stroke Turbo engine. These were produced by ALCO as well as BLW. Originally named as ALCO DL560C, the locomotive engine had a power output of 2600 horsepower.

The co-co wheel arrangement was used in the locomotive. These are the most common locomotive engines used across India, with more than 2600 units produced from 1962 to 1998.

These engines were specially chosen for the Indian climate and environmental conditions. They had enough power and could be used in almost all conditions. The construction technology was straightforward, resulting in mass production of the loco.

Through the 37 years of their production, various variants were produced that included different features. Jumbos were the locomotives that included huge windows with a short hood. Another variant included air brakes and was named WDM2A. For shunting, various such engines were remodelled when they nearly completed their service life. These were named WDM2S.



 These are some of the latest additions to diesel locomotives with their three parallel engines of 800 horsepower each. The two units created have a Co-Co wheel arrangement with a top speed of 120 kph. The series is completely made in India and is well-acclaimed for their efficiency to save energy. The three separate engines, termed as gensets, can be used individually in a parallel combination to get the total pulling power of 2400 hp.

The main advantage of the engine is that two of the gensets can be turned off when the locomotive is not pulling or is idle. Thus, it saves energy and can be used for low-powered jobs. Here, the G stands for ‘gensets’.


After ALCO, Indian Railway reached out to Henschel and Sohn. Originally named DHG 2500 BB, these locomotives had Mercedes diesel engines and were a hybrid of diesel and hydraulic. Though they were in service for around 25 years, nothing concrete is known about these engines. They had a B-B wheel arrangement with a speed of 120 kph.


Mostly based on the WDM-2 locomotive model, WDM3A was the production of the Indian Railway to replace the ageing WDM-2 engines. It has a 16-cylinder 4-stroke turbo diesel engine with a power output of 3100 horsepower. They used the Co-Co wheel arrangement and were no more than an up-gradation of the model used in WDM-2. Out of the 1200 WDM3A, only 150 were originally manufactured. The rest were rebuilt from WDM-2.



Though they were manufactured after WDM3C and WDM3D, the 23 models are based on WDM3D. It had the same structure and working except that it did not have a microprocessor control system. Instead, it used a control system known as E-Type Excitation. Mainly housed in the areas in Uttar Pradesh, including Lucknow, Gonda, Jhansi, Samastipur, etc. The locomotive had a power output of 3100 horsepower with Co-Co wheel arrangement. Most of the models were created by stripping down the features of the microprocessor from WDM3D.


These were the remodelled versions of WDM2 and WDM3A. They had the same structure and wheel arrangement as them, just the power output was increased to 3300 hp. They can acquire a top speed of 120 kph. These were aimed to develop engines with more power. Developed in 2002, none of these engines is available now as they have been stripped back to WDM2 and WDM3A.



These are the upgraded versions of WDM3C. Most of them were originally built-in 2003. They have a pulling power of 3300 hp and can attain the speed of 160 kph. This was the first engine with which the Indian railway could successfully build a system that could provide the power of 3300 hp. They were a hybrid of the basic ALCO technology and EMD. They have a distinct structure with their narrow body and DBRs on the roof of the short hood.

These are the only ALCO models, along with WDG3A that are still under production to date.



These 16-cylinder 4-stroke turbo-diesel engines are also based on ALCO engine design. They were produced in 2008 but were then converted to WDM3D. Having an impressive pulling power of 3500 hp, these loco engines can achieve the top speed of 105 kph. All of these are used as freight trains and have speed restrictions of 85 kph.



These engines were the last effort of Indian Railways towards developing a more powerful version of ALCO engines. Only four of such units were produced containing a pulling power of 3500 hp. They have similar features as WDM3D. Though these could provide a raised power, the Indian railway decided against the development of the engines as they realized that the ALCO technology was too outdated.



A competitor for ALCO DL560C, this General Motors production was selected to find the perfect diesel locomotive for India. Though, in the following years, these were dropped by the Indian Railways in spite of their better technology and speed. It was a WDM4 engine that pulled the first Rajdhani Express from Howrah to Delhi. At present, all of the models imported have been decommissioned.



This locomotive had all the aspects required for a shunting engine with its 6-cylinder 4-stroke engine that provided 1350 hp of pulling power and 75 kph top rated speed. Developed as a part of an experiment to develop low-powered engines, only two such models were manufactured. One of these still runs in the area around Bardhaman.



These are light-weight versions of the ALCO technology. Developed between 1987 and 1989, 15 of such locomotives were built, all of which are still in service. It has the same specs as the other ALCO based engines and provides 2000 hp pulling power with a top-rated speed of 105 kph. They are used in the area of Tondiarpet currently to carry lighter passenger trains and for shuttle services.

After 4 decades spent reworking the same ALCO engine technology, Indian Railways moved on from mixed engines to develop specialised engines for passengers and goods. The difference between engines aimed for passenger trains and freight trains lies in the weight and gear ratios of the locomotive.


The prominent productions under the series are described below:

WDP Locomotive
Image Credits: https://www.irfca.org/apps/locos/show/6271



After WDM7, Indian railways experimented to develop a low-powered engine based on ALCO technology that can be used for short-raked passenger services and provide better speed. The locomotive had a 20t axle load with Bo-Bo wheel arrangement. The structure was perfect for a lighter load, hauled at greater speed. It has a 4-stroke turbo diesel engine with 2300 hp pulling power.

They could run at the top speed of 140 kph, though all the units faced maintenance issues. Due to this, the production was stopped, and the engines were never used for an Express. These locomotives are still in service and are used as local commuter trains.



Originally named as WDP2, these ALCO based locomotives had a completely different shell that supported the modern aerodynamic shape. With 3100 hp output power, the engine could achieve the speed of 160 kph. Though the results provided by the locomotive were favourable, the production was finally stopped in 2002 as Indian Railway decided to develop EDM technology for locomotives. These are still in service and can be spotted in Trivandrum Rajdhani.



Imported as EMD GT46PAC, these V16 2-stroke turbo diesel engines had the power output of 4000 hp with a top-rated speed of 160 kph. Between 2002 and 2011, 102 units were produced. They use the wheel arrangement Bo1-Bo. These units were specially built for the Indian Railways by EMD, USA. Some of the units were directly imported from EMD after which they were assembled here. Later, DLW began to develop units in India.

They had a microprocessor control system with unit fuel injection and self-diagnostics system. The locomotive became the future of diesel locomotives in India as it brought top-notch technology that was years ahead of the original ALCO models. Though the engine has flaws with its single cabin design and Bo1-1Bo wheel arrangement, the former causes visibility issues in LHF mode while the latter results in the low tractive effort of 28t.


The low tractive effort caused wheel slips, which then became the cause of development of WDP4B.



The locomotive has the same features and working as the model it is based on, WDG4. Its development began in 2010 and still continues. The locomotive provides 4500 hp of polling power with 130 kph top rated speed. It has a Co-Co wheel arrangement with 6 traction motors for all six axles. Thus, the tractive effort becomes 40t with an axle load of 20.2t. The locomotive sports bigger windows with an aerodynamic front of the cabin.


The WDP4B model still did not address the issue of low visibility when operated in LHF mode. Thus, Indian Railways had to modify the cabin and add another to EMD. The D stands for Dual Cab. The extra cab makes the locomotive easier to operate and much more comfortable for drivers and pilots to drive faster and safer. These are very powerful locomotives with 4500 hp at 900 RPM and can acquire a speed of 135 kph.


WDG1 is guessed to be a prototype of engines developed for freight. Currently, there is no engine in Indian Railways that is classified as WDG1.


Originally termed as WDG2, this was the first successful freight locomotive that had a V16 4-stroke turbo engine. The locomotive had a pulling power of 3100 hp and provided a top-rated speed of 100 kph. It is deemed to be a cousin to the other two engines developed after EDM2, WDM3A and WDP3a as it has a higher tractive effort at 37.9t compared to WDM3A.

It is the most commonly used locomotive engine in India used for freight trains to date. These are used to drive various heavy goods such as cement, grains, coal, petroleum products, etc. One can find the engine around Pune, Guntakal, Kazipet, Vizag, and Gooty.


After WDG3A, Indian Railways tried to create a locomotive with better output power. The WDG3B was an experiment, though none of the units exists today. There is no specifications or information confirmed about this variant.


Another experiment that was not deemed successful. The one unit produced is currently housed in Gooty. Though the unit is still in service, it is no longer classified as WDG3C.


This locomotive was another one in the line of experiments that were not successful. Only one unit was produced that provided around 3400 hp of output power. It had a microprocessor control system and other favourable specifications.


After four decades of experiments, WDG4 was produced in India after a few units were imported from EMD, USA. The monstrous design of the locomotive was supported with a tractive effort of 53t and axle load of 21 tonnes. The locomotive provides 4500 hp power with all the latest technologies such as self-diagnostics, traction control, radar, autopilot, automatic sanding and various others. It is a cost and energy-efficient freight engine with a mileage of 4 litres of diesel used per kilometre.


The modified version of WDG 4, the locomotive is completely developed in India and sports V16 2-stroke turbo diesel engine with 4500 output power at 900 RPM. It has been named ‘Vijay’ and is India’s first dual-cab freight locomotive. The locomotive is designed keeping in mind the comfort and ease of the pilots along with top-class technologies such as being completely computer-controlled with IGBT.


Named ‘Bheem’, the locomotive is developed by the collaboration of RDSO and EMD. This V20 2-stroke engine provides 5500 hp of output power at 900 RPM. The locomotive also includes all the new features and technologies. Though, the engine has a bad reputation for its LHF system.

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