Rolling Stock - II

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• Freight Wagons
• Brakes
• Couplers
• Power Generation
• Miscellanous

Freight Wagons

Q. What are loading gauge restrictions (maximum dimensions) on IR wagons?

Please see the latest 2004 standards for rolling stock dimensions. The 1971 standards for rolling stock dimensions can be seen here and the older 1929 standards are available here. Also of potential interest in this connection are the dimensions of tracks.

Q. How are freight cars classified by IR?

The following codes are used now for classifying freight cars. The classification scheme is not entirely systematic. Some older wagons especially have codes that are not easily explained in this way. But in general an optional gauge code is followed by a type code which is followed by an indication of the coupler and whether the wagon is air-braked.

Gauge code

• M: (prefix) MG
• N: (prefix) NG

Wagon type code

• B: (prefix) Bogie wagon
• BV: Brake van
• V: Brake/parcel van
• O: Open wagon (gondola)
• C: Covered wagon (boxcar)
• F: Flat car
• FK: Flat car for container transport
• FU: Well wagon
• LA: Low flat car with standard buffer height
• LB: Low flat car with low buffer height
• LAB: Low flat car, one end with low buffers, the other with high buffers
• R: Rail-carrying wagon
• T: Tanker (additional letters indicate material carried)
• U: Well wagon
• W: Well wagon
• K: Open wagon: ballast /material /refuse transport (older wagons)
• C: Centre discharge
• S: Side discharge
• R: Rapid (forced) discharge, bottom discharge
• X: Both centre and side discharge
• X: (also?) High sided
• Y: Low (medium?) side walls
• L: Low sided
• H: Heavy load

Following the type code in the classification code a letter may denote the type of coupler, nowadays optional, as all new freight cars are fitted with centre buffer couplers (CBC). An ’N’ suffix is for ‘pneumatic’, or air-braked wagons. Newer stock that is air-braked also has CBC couplers, so the ‘C’ is usually dropped. E.g., BOXN for air-braked BOX wagons, not BOXCN.

Coupler, brake, and other suffixes

• C: Centre buffer coupler (CBC)
• R: Screw coupling only
• T: Transition coupler (CBC with additional side buffers and screw coupling)
• N: Air-braked
• M: (suffix) Military

BOXNHL, the most common type of open wagon, is made of stainless steel, but otherwise most wagons are constructed using steel. Some special steel alloys are used to reduce corrosion, as on the BOXNCR (with IRS M44 steel), but these are rare and not produced in large numbers.

In late 2004, IR began looking into using steel substitutes, and plans were drawn up for the production of aluminium-body wagons (BOBNAL, BOBRAL). Initial estimates were upto 750 wagons in 2005-2006, including some surprisingly in a 4-wheel design. The tare weight was expected to be reduced by about 4.2 tonnes. Other than some trial wagons, these never enter production.

Recently (12/2018), there has been talk about reviving these aluminium-body wagons, but no actual production has taken place.

As seen in the permanent way section, many BG routes (especially on SER, SECR, ECoR, etc.) have rails that allow axle loads of up to 25t, but most other routes operate with a restricted axle load of 22.5t to 23.9t.

Notes on select freight wagons

Note: The listing here is not exhaustive and omits many minor revisions and variants. For obselete stock and wagons not in use, see below.

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Rare wagons

These wagons were either produced in limited numbers or have been almost withdrawn from wider service. Some may even have been scrapped.

BFKN

Container flat car for ISO containers, with retractable anchor locks. Originally used by CONCOR before switching over to BLCA/BLCB flats. CASNUB bogies. Vaccum braked versions were BFKI.

BCCN/BCCNA/BCCNB

Automobile Carriers. A few wagons also marked BCCN like the older cement carrier. These have a low platform with 840mm wheel diameter and are fitted with air brakes. The explanation of the class code is that they are thought to have been made by taking old BCCN wagons and modifying them. They were built in 1997 by the Golden Rock Workshops based on designs from RDSO, and were intended to carry Maruti brand automobiles.

BCCNR

Automobile carrier wagons introduced in 2004. these are single-deck covered wagons with 10t capacity and 28.5t tare weight, and a low platform with 840mm diameter wheels. Some of these were limited to 65km/h but later were apparently approved for 100km/h. These were designed to capture more automobile traffic, especially from the south where many automobile plants are, following the introduction of different car models by various manufacturers in recent years which could not be carried on the original wagons. BCCNR wagons are not thought to number more than about 35.

BTCS

Bogie tanker car for caustic soda. Width 2.56m, height 4.11m. Inside diameter 2.3m. CASNUB bogies, CBC.

Other variants of the same design include BTSA (for carrying Sulphuric Acid), BTAL (for carrying Anhydrous Ammonia).

HTC

(Non-standard classification code) BG Long Covered Wagon, for defence use. Screw couplers and side buffers, CASNUB 22NLB bogie, air brakes. Has a 'hood transfer mechanism'.

BVZC

Fur-wheeled brake van, with CBC. Once the main type of brake van, these have been superseeded by the BVZI (see above). Some are still found on departmental, engineering and other works trains.

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Old, obsolete wagons

Note: This is a partial list. Please refer to this document for the full list.

BOX

High-sided bogie open wagon. Side discharge arrangement. 55 ton capacity, 25 ton tare. Used for coal and other bulk goods. BOXT, BOXR, and BOXC are the same with transition, screw, and CBC couplers, respectively.

BOXS

BOX wagon with side discharge/flap doors and siding roof.

BCN

Bogie covered 8-wheeler wagon, CASNUB bogies, air-braked, CBC. Originally developed in 1984 for carrying bagged commodities. Original model had entirely riveted construction. Predeccesor to BCNA.

BCX

Water-tight covered high-sided bogie wagon with cast steel bogies. Cartridge taper bearings on newer ones. Snubbers and nested coil springs under bolster, elastomeric pads, with secondary suspension system. Used for foodgrains, cement, etc. (BCXT, BCXR, BCXC are variants with transition couplers, screw couplers, and CBC).

BFK/BFKX

Early version container flat car. The 'X' version had CASNUB bogies.

BTORX, MBTORX

Bogie tanker wagon for vegetable oil, and its MG variant.

BVG, BVGT, MBVG, NBVG

Brake van for non-block rakes. BGVT is the same with a transition coupler. MBVG is the MG version and NBVG is the NG version. 4-wheeled.

MBC, MBCX

MG bogie box wagon, 34 ton capacity, 13.4 ton tare

MBOC, MBOCX

MG bogie open wagon (coal, etc.), 35 ton capacity

MBTW

MG bogie water wagon

MBTPZ

MG bogie petroleum products wagon

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Additional notes

Several of these wagons use ‘CASNUB’ bogies. These are cast-steel bogies with friction-damping arrangements (hence the name, from ‘CAst steel SNUBber equipped’). These come in some variants, e.g. CASNUB HS is a high-speed variant allowing speeds up to 100km/h, CASNUB 22 NLB has additional correction and friction damping mechanisms, CASNUB HA has higher payload capacity, etc.

Milk vans, because of the perishable nature of their cargo, have the curious privilege of being treated as passenger coaching stock with corresponding speed limits. Milk vans are often attached to passenger trains and are rated for 110km/h. The older ones were vacuum braked and were limited to 100km/h.

In the past, some older 4-wheel (non-bogie) tank wagons (TK, TP, etc.) were being re-used in an inventive way: the tank and part of its base was fitted on to a frame that matched the shape of a half-size standard ISO container frame and which was then carried on normal container flat wagons. This allowed the tank and its frame (which still had years of useful life left) to be used even though the original 4-wheeled wagon base was scrapped.

EMU stock has often been converted by IR for use in carrying goods, by sealing the windows and removing all interior fittings.

Special-purpose wagons of various kinds have been used by IR. Some 24-axle threaded beam well wagons and 18-axle well wagons with integral brake vans at either end are used by BHEL for transporting large transformers. BHEL, Trichy, has a 24-axle saddle wagon named ‘Kaveri’ for transportation of large electrical equipment. It also has an 18-axle well wagon.

The Atomic Energy Commission has(d?) some 12-axle and 16-axle saddle wagons as do a few other heavy industrial concerns, power companies, NPC, etc. A 20-axle well hole wagon was built specially for GEC Alstom's use in transporting large electrical equipment. Several of these multi-axled heavy wagons were built by Golden Rock workshops. ‘Merry-go-round’ wagons used at power plants and mines can tilt sideways to unload their contents as each wagon in the rake passes by.

Q. How are freight cars numbered on IR?

In 2003, when freight operations were computerised, IR switched to a 11-digit numbering scheme for all wagons to maintain uniformity and keep track of wagons.

The first two digits denote type of wagon, the third and forth indicate owning zone, the fifth and sixth denote year of manufacture, the seventh to tenth digits the individual wagon number and the last is a Check digit. The Check digit is an additional method to make sure the wagon numbering is truly unique in case of manual errors during overhaul and recommissioning. The method to calculate this digit is complicated and beyond the scope of this document. Readers interested in the details are encouraged to search for the relevant information on various IR websites.

Q. How many freight wagons does IR have in its fleet?

As of 2019, IR had 289,115 wagons.

Q. Where are IR's freight wagons manufactured?

Most wagons today are manufactured by private firms such as Titagarh Wagons, Texmaco Rail & Engineering, Jindal Rail Infrastructure, Hindustan Engineering, Modern Industries, BESCO and Jupiter Wagons.

Public-sector organizations such as Burn Standard Co., Braithwaite, Jessop, Bharat Wagon and Egg. Co used to manufacture wagons in the past, but privatisation, liquidation etc. has meant that only Jessop (now once again privately owned) and Braithwaite make wagons now. (Many of these used to be private concerns but were taken over by the state.)

A small fraction of the wagons come from IR workshops such as those at Golden Rock, Amritsar, and Samastipur. Golden Rock especially has built quantities of many different kinds of wagons over the years, and in the early days of container operations made large numbers of the BLCA/BLCB container flats needed by CONCOR.

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Brakes

Q. What kinds of brake systems do IR coaches and freight cars have?

In both passenger coaches and freight wagons, the continuous braking system consists of air brakes. The guard often has mechanical brakes acting on his van. In addition, each piece of stock has mechanical parking brakes.

Air brakes are of the twin pipe system, with a feed pipe and a brake pipe. In the initial days of air-brake introduction, single-pipe systems were used, but were quickly converted to twin. (The twin pipe system fixes a problem with the single-pipe system where the air in the auxiliary reservoir can be used up faster than the brake pipe can charge it.)

BG EMU rakes have electro-pneumatic (‘EP’) brakes which are essentially air brakes, but where the application is controlled electrically at each brake unit. BG EMUs have had air brakes for many decades. MG EMUs of the Chennai system were vacuum-braked. DMU rakes have standard twin-pipe graduated release air brakes.

Until the late 1970s and the early 1980s, air brakes were rare. Vacuum brakes were the most commonly used continuous braking system on IR. Perhaps the most notable ‘convert’ at the time was the Mumbai Rajdhani which switched to being air-braked in 1984, hauled by twin WDM-2 locos. The Howrah Rajdhani also switched to being air-braked around 1986.

Continuous brakes were tried out by the various railway companies in the late 19th century. North Western Railway was the pioneer with trials of continuous vacuum braking in the late 1880s and early 1890s. Vacuum brakes were chosen for the simplicity of design and lower cost. They also did not have coupling cocks that could fail mid-train.

Early examples of the use of air brakes on IR include the Metro Cammell EMU stock delivered between 1951 and 1953 (and similar stock later delivered by other manufacturers), which featured the Westinghouse twin pipe air brake system and electro-pneumatic application (the 1924 and 1928 EMUs (CR and WR) were vacuum-braked).

Sahyadri, Maharashtra, Koyna, Toofan and the Bokaro/Tatanagar - Alleppey Expresses were among the last trains to run vacuum braked stock (these were converted to air braked during 2003-2004). In early 2005, the Viramgam Passenger was perhaps the longest train to be a holdout and still ran vacuum stock, including a 2AC coach from the late 1960s!

Dual-braked passenger coaches were rare, but some did exist, including sleeper coaches and AC 3-tier coaches; most of these were not for general use but are saloons, inspection cars, or officer's cars, which needed to be attached to either air-braked or vacuum-braked rakes.

MG and NG coaches were predominantly vacuum, but later ones were all converted to air braked.

Air brakes are among the most significant changes undertaken by IR in recent decades. They have allow much higher speeds on most sections as trains can be safely braked in a shorter distance, leading to better track utilization. Earlier, for instance, it was standard practice to begin braking at an Attention signal (double yellow); now most trains speed past an Attention signal at the highest permitted speed and begin braking only when a Caution signal is sighted. Safety has also increased with the power and precision of air brakes.

Changing locomotives is now a matter of minutes - the angle cocks are closed, the locomotive is detached, the new one attached and the cocks are opened once again. Earlier, disconnection of the vacuum hose meant that all the brake pistons under the coaches went into emergency mode and had to be manually released (by pulling a wire loop — usually marked with a star — under the coach). The process of releasing the brakes would easily take around 15 minutes for vacuum-braked stock.

Brake blocks used to be made of cast iron. Later, various other materials were brought into use, including asbestos-based materials. In April 2001, RDSO has developed new kinds of asbestos-free composite materials for use in brake blocks. These are known as the 'L' type brake blocks and after being introduced for BG, were introduced on MG in 2005.

LHB coaches have disc brakes.

Q. What kinds of brake do IR's locomotives have?

Locos in IR have air-brake systems and all new locomotives manufactured since the mid 1990s have only air brakes as the original equipment.

In the transition decades of the 80s and 90s, many locos had dual braking capabilities as there was still a lot of freight stock (and to a lesser degree passenger coaches) that was vacuum braked.

For instance, the original WDM-2 locos were vacuum-braked. As air braked stock came into wider use, many of these locos were retrofitted with air brake systems as well, hence the sub-class WDM-2A which had dual braking capability (this class is now scrapped). Later locos such as the WDM-2B, most WDM-2C(3A) units have only air brakes.

The presence of air brakes or dual-braking capability was indicated by a number of ad hoc means, such as annotations (‘DB’, ‘Dual Braked’) or markings (thin blue stripes running along the bottom of a loco, for instance).

The annotations ‘FP’ and ‘BP’ on a loco indicate the presence of the Feed Pipe or Brake Pipe, respectively.

Various forms of ‘dynamic’ braking are also used as supplementary systems where the kinetic energy of the loco is used to generate electricity which is dissipated in some manner (resistive grids are common (‘rheostatic braking’ or ‘dynamic braking’); some old EMUs in Bombay used electromagnets acting close to the rails; some locos used the extra energy to heat water in tanks).

In some locos dynamic brakes are part of the original equipment, whereas in others they are retrofitted, e.g., some WAP-4 locos have dynamic brakes with dissipation grids mounted on their roofs.

In a variant known as ‘regenerative’ braking, the energy is fed back to the overhead cables; this was done by the DC locos (WCM series, definitely WCM-1 but not all of its successors). Feeding energy back to the cables is more complex with AC power, but the latest WAP and WAG series locos have provision for this.

Q. What are ‘auto-emergency’ brakes?

Many locos used in steep ghat sections also have an ‘auto-emergency’ (‘AE’ or ‘AEB’) brake system, which consists of an additional safety circuit which monitors the speed and applies the brakes to slow down or halt the locomotive if the speed rises above a certain threshold (sometimes 25km/h or so, but this varies with the route and the working rules in effect).

There isn't a separate set of brakes, but rather, the loco brakes are applied independent of the driver's control when the system is armed. The system is armed by using a key that the driver then hands to the guard. If the brakes trigger automatically, the key has to be retrieved from the guard and used again to get the train going (and a lot of paperwork has to be filed as well!).

AE brakes are used especially on locos from Hubballi and Gooty sheds that work the Braganza ghat. The AE brake system is armed when the locos are going in the downhill direction; its use is mandatory as there are no other safety features such as catch sidings on this route.

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Couplers

Q. What kinds of couplers are used on IR's trains?

IR’s passenger stock uses two types of couplers. All LHB stock have tightlock CBC (centre-buffer-coupler). Some newer ICF stock also use CBC, but the majority of ICF stock are equipped with screw couplers and side buffers. Screw coupler passenger stock is no longer being manufactured.

CBC equipped ICF stock started as an experiment in the early 2000s. One rake of the Prayagraj Express was fitted with CBC as a trial. CBC overcome some of the limitations of the screw couplers — limited draft load and energy absorption capacity, lack of anti-climbing feature, etc. CBC would also reduce the inter-coach distance.

All new freight stock and container rake wagons for CONCOR, have CBC (MCB (or 'Janney' or 'knuckle' (US style) couplers). In particular newer freight stock has AAR type 'E' CBC usually with high-capacity draft gear. The older freight stock had hook couplers with side buffers, as well as with screw couplers.

Transition Couplers: There are also ‘transition’ couplers, which have a CBC mechanism for coupling to other CBC, but which also have a central screw coupling provision allowing coupling to wagons which do not have CBC. There are two side buffers provided as well. These were useful when CBC were just being introduced and there was a lot of freight stock that had screw couplers, but they have now gradually lost their importance as more and more of the freight stock is fitted with CBC. These days only locos and brake vans tend to have transition couplers. Older BOX wagons, older diesels (many WDM-2's) and other older rolling stock had Henricot Transition Couplers with a double screw arrangement. Somewhat newer rolling stock had the so-called Alliance or Clevis Transition Coupler. This had a clevis to be locked under the knuckle before using the screw coupling. A locking pin indicates whether the CBC portion is properly coupled or not.

Plate Couplers are temporary or short-run couplers that can be used to couple locomotives without CBC couplers to CBC-fitted wagons. Pocket Couplers, similarly, are used for temporarily coupling incompatible wagons. Both of these types of temporary couplers do not perform well in practice. They were also generally in short supply at marshalling yards and elsewhere. The move to block rakes of CBC wagons in the 1980s greatly reduced the demand for these temporary coupler types. These type of couplers are no longer used on IR.

The Jones Coupler (an adaptation of the Norwegian coupler) is used on MG and some NG lines. Also known as the chopper coupler, this uses a hook (the chopper) which fits into a yoke on the coupler of the next car. A bar behind the yoke controls the tension in the coupler. MG wagons and coaches have the chopper at one end and the non-chopper coupler at the other end, hence a rake of MG wagons has to have them all oriented in the same way.

MG locos have the choppers at both ends. When coupling a loco to a wagon, the loco's chopper is used if coupling to the non-chopper end of the wagon, but the wagon's chopper is used if coupling to the chopper end.

Jones couplers were developed in India and later spread to several East African and South-East Asian railways. Some NG lines used a basic Norwegian (or 'chopper') coupling, which had a square or circular face with a slot coming down about half-way from the top.

Other NG lines used the ABC Patent Coupling (ex-GIPR: Arvi-Pulgaon, Achalpulpur-Murtijapur-Yavatmal, Daund-Baramati, etc.). This had a disk that rotated and latched on to a horizontal loop from the mating coupler. The Darjeeling Himalayan Railway uses a rudder coupling system to deal with the severe curvature on some sections of its route. However, the Kishanganj branch of the DHR used chopper couplers, as can be seen on the DHR C class Pacific at Mumbai and the lone Garratt made for this line.

EMUs use Scharfenberg Couplers which are a centre-buffer type which automatically connect the electricity and air links as well. The coupler face is rectangular (from above) and has semicircular ends. A large pin projects from the end of the coupler, which mates with a corresponding hole in the coupler of the other car. DMUs also use these couplers with regular twin brake pipes, although in some cases (e.g. Jallandhar DMUs) they are modified to have different brake hoses than the integrated ones that are part of the couplers. In IR parlance, these couplers are called ‘Shaku’ couplers.

Buffers

The side buffers typically used on locomotives, coaches, and wagons mostly use helical springs with rubber or synthetic compression elements. Some buffer designs rely entirely on multiple packs of rubber compression packs. Previously, helical springs were the only mechanisms for compression resistance.

Buffer capacity in the past was low, at about 450kgf-m and the standard loco buffer having a capacity of 490kgf-m. Higher capacity buffers of 1030 and 1225 kgf-m have been introduced and RDSO's most recent design is for a buffer of capacity 1225kgf-m.

History of couplers in India

Originally, Indian coupling consisted simply of chains — one in the middle and one on either side as back-ups — and buffers that were extensions of the side structural members of the coaches (“dumb” buffers) for freight cars. Passenger cars often had buffers filled with materials like horsehair.

Spring buffers were employed from about 1850, starting with under-wagon leaf spings, and evolving into the modern coil-spring buffers that contain the spring mechanism inside the buffer body.

Five-link and 3-link chain couplings survived into the 20th century, especially for low-speed (under 40km/h) operations. The linking chains evolved to have a screw mechanism (hence “screw coupler”) to keep buffers of adjacent cars touching and slightly in compression so as to provide a smoother transition on starting a train. By the 1920's chain couplings almost all disappeared, especially as vacuum braking came into wide use.

The only steam class with automatic couplers were the WGx subclass used for heavy freights on SER.

In 1980, IR made the move to using block rakes of CBC wagons as far as possible for goods movement. This meant that the problems of coupler incompatibility among wagons and among locomotives and wagons at marshalling yards and elsewhere were greatly diminished.

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Power Generation - Lighting and Ventilation

Early trains

The earliest passenger coaches had no lighting at all, and passengers were expected to bring their own candles or lamps on board. In the later decades of the 19th century and in the early 20th century, the most common lighting provision was through gas lamps (more common) or vegetable oil lamps. Electric lighting in passenger coaches was introduced starting around 1897, although it had been tried out experimentally a few times before that. The Jodhpur Railway was the first to make electric lighting standard on all its coaches, in 1902, along with an electric bell system to alert an attendant or the guard in case of an emergency. In general, only the first and second class coaches had lights and fans for every compartment, the ‘inter’ or intermediate class had only lights, and the third class coaches had just two lights, one at each end near the door. Provision of lights and fans as standard equipment in all compartments was legislated in 1952.

It has been suggested that on some railways prior to 1950, steam locos were provided with 24V turbine generators to provide power for lighting in the coaches, but it is hard to find confirming evidence for this, and if true, must have remained confined to a few isolated experiments.

Self generating stock

Most ICF design (and a limited number of LHB) coaches are labeled Self-Generation (SG). These are powered by axle-driven generators which charge storage batteries that power lights, fans and other electrical fittings. Coaches have 110V circuitry and use belt-driven 4.5kW, 110V alternators (Air-conditioned LHB stock of this nature use 6.5kW).

Back-up power is provided by banks of 24V batteries (mostly lead-acid batteries of an 1100Ah capacity (800Ah batteries previously)).

Older coaches had 24V (less often 48V) circuitry and had dynamos connected to the axles by belts. These also had 24V battery banks as a back-up. Conversion to 110V circuitry got a big push in the 1990s.

Railbuses such as the ones manufactured by BEML use a 24V electrical system.

Air-conditioned coaches

Air-conditioning equipment is powered by two 25kW 110V alternators, with the voltage being converted to 415v AC. Previously 110v alternators delivering 11-22kW were used, and even before these 11kW/15kW ones were used. Most air-conditioned coaches in the late 90s had just a single alternator. Lights and fans are in AC coaches are often on a separate DC supply from batteries, or stepped down and rectified from the alternators.

End-on Generator stock

In the LHB stock and older ICF stock used on Rajdhani, Shatabdi, Garib Rath etc. electricity is supplied by the use of a separate ‘power-car’ (increasingly replaced by hotel load supply from locomotives, see below) at each end of the rake.

There are usually 2 generators in each power car; each generator (an End-on Generator (EOG)) uses a 750kVA power pack to generate 3-phase 750V AC power, which is then distributed across the train, and stepped down to 415V AC (3-phase) for the air-conditioning, or 110V (single-phase) for other appliances. Each power car at one end of the rake provides power when the train is running in one direction while the other operates in the other direction.

In the past 500kVA and 250kVA sets were used. The 250kVA ones could power upto 18 AC coaches, but their peak efficiency was at a load of 7 to 12 coaches, so for longer trains, both EOG were on simultaneously.

The 250kVA power cars were introduced in 1992. Before that the power cars in use had a capacity of 125kVA and used 440V as the AC distribution voltage. With these, most Rajdhanis and Shatabdis needed three power cars -- one at either end, and one in the middle of the rake, which split the rake into two portions (termed 'Unit I' and 'Unit II'). As the power cars are (were) not equipped for anyone to walk through, there was no way to get from one portion of the rake to the other while the train was in motion.

The two EOGs and the coaches along the length of the train are connected by two independent sets of 3-phase cables so as to be able to handle a failure in a cable. In addition, there are usually 24V batteries in the coaches to power a couple of emergency lights at critical points in the coaches.

Head-on Generation

In this system, power is supplied from the locomotive at the head of the train, hence the term Head-on Generation (HOG). These were under consideration for a long time by IRIEEN and RDSO, but became more common (in fact, now almost all LHB stock is powered this way) when WAP-7 locomotives were fitted with upgraded transformers and hotel load windings. Some WAP-5 locomotives also are HOG capable.

Power is drawn directly from the main 25kV traction transformer. This transformer is provided with two hotel load windings which power the two hotel load converters that supply 750V AC which are then stepped down as in described above.

In the case of diesel locomotives, the three phase converter is mounted on the traction alternator and feeds the hotel load. Only a few WDP-4B locos were fitted with the equipment, but recent reports (02/2021) say these have been removed.

In these rakes, a power car is still part of the consist as a backup. The additional one used in a pure EOG setup is now taken over by a revenue earning coach.

With increasing stock of LHB coaches and electrification, IR plans to eventually run almost all its passenger services using the HOG system.

EMUs/MEMUs/DEMUs

EMUs use the 25kV AC overhead supply, step it down to 110V AC and supply to the coaches. DEMUs are usually powered by auxiliary generators.

DC EMUs in Mumbai used a motor generator to convert the 1500V DC power to 110V AC.

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Miscellaneous

Q. Freight stock often has the words “Not to be loose shunted” –– what does this mean?

In marshalling yards and elsewhere, a common technique of moving a wagon around is “loose shunting”, where the wagon to be moved is not coupled to the shunting loco, and simply pushed to the correct location.

Usually, a rake that is being built up is on one of several sidings branching off from a section of track where the shunting loco is working. The points are set to divert all wagons to the appropriate siding. The shunting loco pushes the wagon and imparts it sufficient speed so that it travels over to the selected siding under its own momentum. Once it reaches the rake that it is to be attached to, the “khalasi” staff couple it up to the rake.

The loco driver has to judge the distances and the weight of the wagon precisely so that the wagon does not stop short of the rake (which would necessitate using the shunting loco again to push it further), and so that the wagon does not have too much momentum which would cause it to crash into the rake being assembled with undue violence. Nevertheless, this process of loose shunting does involve a certain amount of violent impacts on all the wagons involved.

Such impacts are not desirable for wagons that are carrying sensitive cargo, such as cattle, poultry, or even human passengers in the case of sectional carriages being reattached to rakes, and extremely dangerous in the case of cargo such as petroleum products where an impact can cause leakage and ignition of the cargo with disastrous consequences. Hence, such wagons are marked “not to be loose shunted”, implying that they will always be shepherded gingerly into place coupled to a shunting loco.