The Indian Railways Story 12 – Locomotive Working
Locomotives are very complicated machinery, which they have to be, given the enormous amount of work they are supposed to be doing. Imagine the power and complexity of your car and then multiply it by 100. Diesel engines inside the locomotive have 16 cylinders, (V16) and displace around 150 liters, while an average car engine has 4 cylinders and displaces 1 or 2 liters. Some cylinders are so big that you can put your head in them! Diesel fuel tanks can hold 50000 L of fuel, Superchargers can weigh one tonne, Transformers and Rectifiers can be as big as a hatchback car and traction motors can be as big as a Tata Nano. Everything is enormous about these things which weigh upwards of 20 tonnes and cost around 10 Crores a piece! Just imagine how powerful the damn things are, as they need to pull themselves and the entire train as well!Working techniques of locomotives are basically the same across the World on a macro scale, but on a micro scale, they have to be different. For example, locomotives made to work in Nordic countries or Canada should be created to withstand freezing temperatures while those in India need to be made to work efficiently under rugged, rough circumstances and so they should be made very tough and unrelenting. Which is why our locomotives are more utilitarian and less aesthetic. Let us take a look at some common terminologies associated with Locomotives.
Locomotive Terminology
Bogie – The Bogie is not, as many people wrongly say it to be, a railway passenger vehicle unit. That is a coach, compartment or car. A bogie is a unit under a coach or a locomotive which houses the wheels, suspension etc. Usually there will be two bogies for a coach and two or three for a locomotive.Locomotive – A vehicle that powers a train along the rails, the only “live” part of the train. The coaches of a train are only pulled or pushed along the rails by the locomotive. There are numerous types of locomotives, but most are powered by either diesel fuel or electricity collected from overhead lines or a third rail. The Locomotive and the engine are two different things.
Engine – Locomotives are popularly called “Engines”, though the engine is only a part of the locomotive and electric locomotives do not have engines at all. But the engine is the most important part in diesel locomotives. The engines are huge, usually having 16 Cylinders, 32 Valves and about 100,000 to 150,000 cc displacement.
Pantograph – The arm-like device on the top of the locomotive that extends upwards to collect current from the overhead lines. Usually there are two of them for a locomotive.
Shell – The housing body of the locomotive. A WAG7 in a WAP4 shell means a WAG7 equipment housed in the body that is otherwise used for the WAP4.
Traction Motors – Are electric motors that “actually” drive the wheels of the locomotive and hence the train. These motors are located near the wheels or axles of the locomotive and are directly connected to them. They use the electric power generated by the generator/alternator run by the diesel engine or from the transformers in case of electric locos to output mechanical power, is transmitted to the axles/wheels to which they are connected, turning the wheels and moving the locomotive forward.
Transmission – The method used to transmit the power generated by the engine to the wheels. Differs from the traditional automotive sense that it does not involve gears but traction motors and the power that is transmitted is Electric (usually AC).
Wheel Arrangement – Specifies how many wheels are present in how many bogies in a locomotive. The most common WA today is three wheels on either side on two bogies, 12 wheels in total and all axles are powered, denoted Co-Co. This WA is used for locomotives which are meant to haul heavy loads, which is 80% of all locomotives in India. Two bogies with two wheels on either side and 8 wheels in total all powered is denoted by Bo-Bo, which is good for light, speedy loads. The WAP5 is the only major Bo-Bo locomotive in India.
ALCO – American Locomotive Corporation, Inc. An American manufacturer of Diesel locomotives. ALCO supplied India’s first Diesel Locomotive the WDM1 and later the WDM2 also, which became the mainstay of the Indian Railways. All Indian locomotives except the WDP/G4 are based on the WDM2 and are called “ALCOs”
EMD – Electro Motive Diesel, an American company which manufactures Diesel locomotives and is wholly owned by Caterpillar Inc. It was previously owned by GM (General Motors). EMD supplied the WDP4 and WDG4.
Long Hood Forward (LHF) – This is a driving mode for locomotives when the locomotive is driven with the driving cab behind the longer Hood length of the locomotive body. Visibility might be a problem here and many locomotives have speed controls when driven in LHF. Some like the WDP4 EMDs have been criticized for their too long hoods obscuring visibility.
Short Hood Forward (SHF) – This driving style is the opposite of LHF where the locomotive is driven with the cabin towards the front of the locomotive, behind the shorter “nose” of the loco. This is actually the “forward” operating position of the locomotive, since the long hood is technically the rear of the loco with the radiator, exhaust and all. Dual Cab locomotives do not have LHF/SHF.
Views from ALCO Locomotive Cabin for Locos Driven in LHF and SHF Modes
How Diesel Locomotives Work
A “Diesel Locomotive” is a self-powered railway vehicle that moves along the rails and pulls or pushes a train attached to it using the power generated by engine running on Diesel fuel housed in its body. The diesel engine is the prime mover or the primary supplier of power. It uses this power to pull or push In modern diesel locomotives there is no direct mechanical connection between the engine and the wheels, unlike conventional automobiles but are more like Hybrid automobiles. Instead, the diesel engine turns a huge generator/alternator which produces electricity (earlier Direct Current, nowadays Alternating Current) which is then transmitted to another set of motors called “traction motors” housed near by and are connected to the wheels/axles of the locomotive. These motors use the electric power generated by the engine to produce the actual (rotational) torque that turns the wheels of the locomotive. These locomotives are called “Diesel-Electric”, which include all mainline diesel locomotives in India. Some of the earlier ones had DC transmission, but all the newer models have AC transmissions. Locomotives do not have gearboxes. A control system controls the amount of electricity fed into the traction motors depending on the grade, speed, adhesion factors etc. In modern locomotives, all this done by computers.Diesel Locomotives are very basically said, giant self-propelled electricity generators.
How Electric Locomotives Work
An “Electric Locomotive” is a railway vehicle that can move along rails and push or pull a train attached to it using electric power drawn from an external source, usually overhead cables or a third rail. Electric Locomotives do not have a conventional “engine” in them but use the electricity collected to power traction motors to turn the wheels. Electric Locomotives in India are of three types: Those which can work on DC (Direct Current), AC (Alternating Current) or on both (AC/DC – Bi-current). Electric Locomotives, though high on electrical engineering, work on the single principle of drawing current from external sources and then after sufficiently “modifying” that current feed it to the traction motors. The process of “modifying” the raw current drawn from outside into “usage” power includes a complicated process of conversion, reconversion, smoothening and transformation of the current to varying values of frequency, Voltage, Current etc. This involves a bank of many components like transformers, rectifiers, inverters, capacitors, thyristors, compressors and other such paraphernalia. The “shell” you see actually houses all these equipment, and there is no central “Engine” or prime mover for these. All this has to be done for optimum performance of the traction motors under different conditions and loads. Bi-Current locomotives are the same, only they have more equipment packed inside them to enable them to work under both currents. Each one the Pantographs are used to collect a specific type of current only. The newer three “modern” locomotives in India – the WAP5, WAP7 and WAG9 are three-phase locomotives, which are more efficient than the older WAM-type locomotives. In short,Electric Locomotives are basically giant electrical transformers on wheels.
Image Courtesy: The Physics of Electric LocomotivesLocomotive Designs and Driving
There are three types of locomotive driving structures in India: Single Cab forward, Dual Cab forward and Hood Unit cabs. The Dual Cab Forward type will have cabs or driving cabins at either end of the locomotive and is seen in the new electric and diesel locomotives like the WAP series, WAG9, WDP3A and WDP4D. This type of cab is the most convenient and safest to operate, as it gives the best view for the loco pilots (Drivers) of the way ahead and does not require “turning” locomotives around. The second type will have a driving cab at only one end of the locomotive, seen in WDP4 and WDG4 EMD locomotives. Essentially, this design is intended to be used with turntables where the locomotive is always turned around so that the forward cab faces the direction in which the train is moving or with two locomotivescoupled together so that the cabs of both locos face outwards. However, since India does not have turntables, WDP/G4s are driven in Long Hood Forward mode often where the non-cabbed end faces forward, requiring the loco to have two control stands like the ALCOs.The third type is called the Hood Unit Cab, the most widely seen cab structure found on all ALCO diesel locomotives (except the WDP3A) in India (WDM2, WDM3X, WDG3X etc). In this case, the cab is located close to but not at the exact end of the locomotive, but at around three-fourths of the locomotive length. The body shell of the loco will not be “full” but narrower than the superstructure with walkways around it, to enable visibility from the cab which will extend the full width of the body. The loco will also have two control stands, one each on opposite left sides so that the driver will always be facing forward no matter in which direction the locomotive is going, be it LHF or SHF. So in India there is no “reverse” mode for railway locomotives unlike in some American ones (like the one driven by Denzel Washington in the movie “unstoppable”). All locomotives in India are left hand driven because the signals are located on the left side of the track, and trains always run on the left one of the two tracks, just like on roads.
The Blue TKD WDP1 in LHF mode (driver on the other side) and the Orange WDM3A in SHF mode.
The Diesel vs Electric Question
The “Diesel or Electric?” debate started in India around the end of the 1950s when it had become that the future did not lie in stem traction and it had to be done away with. Diesel won initially but in the long run majority vote seemed to favor Electric Traction. Electric traction is viewed to be cleaner, faster and more “modern” than Diesel, especially so in India and of course, it is. Electric locomotives are far more flexible when it comes to operation and are faster, more efficient and cost less to maintain compared to Diesel Locomotives. But even then arguing for an all-out blanket electrification of all routes in the country is a blind argument made without considering facts. Electrification of railway lines come at a huge, huge cost, and it should be carried out only if the gains and savings are substantial in the long run. Diesel prices may be going up, but even then it makes no sense to electrify branch lines which have only six trains passing daily. Electric traction is best suited for high-volume trunk routes (Bombay-Delhi, Chennai-Nagpur-Delhi, Chennai-Howrah, Kolkata-Delhi, Bangalore-Chennai), suburban commuter lines, lines with high-density long-distance traffic with frequent stoppages (entire state of Kerala, CBE-MAS, Mumbai-ADI, SBC-MYS, Mumbai-Pune) and such. Diesels are the best when volumes are low, or on ghat sections and rainy areas. Many trains whose routes is partially electrified, run diesels under the wire without changing locomotives because it is not worth it. As the saying goes, a non-electrified double line is always better than an electrified single line. The Indian Railways fortunately seems to be headed in this direction which makes sense.Since its formation in 1948 in its present form, the Indian Railways has operated 93 different classes of diesel and electric locomotives. Only four types of Steam engines were widely known to be in service, the WP, WG, YG and YP class locomotives, which were all withdrawn from active service by the late 1980s. Today, the scene is dominated by Broad Gauge AC Electric and Diesel Locomotives. In the next parts, we will check out all these locomotives one by one, starting with the Diesels.
Previous Part (11) – Indian Railways Locomotives Classification Scheme
Next Part (13) – The Locomotive Roster of Diesels-1 (WDM Series)
>> SEE ALL PARTS OF THE INDIAN RAILWAY STORY SERIES HERE
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