India Government Railways 4-6-2 Locomotives in India


Class Details by Steve Llanso of Sweat House Media

Class IGR/ZP (Locobase 4295)

Part of the series of post-World War II designs, this class shared its boiler with the YL Prairies. Unlike most 4-6-2s, however, this engine seems to have been optimized for tractive effort at low speed.

Dr. Jonathan Smith of Iowa State ([] ) for weights, EHS; Hollingsworth (1982) for the rest.


Class IRS/XA (Locobase 2590)

One of three Indian Railways Standard (IRS) locomotives, this was the branch-line passenger variant. (XBs went 17 tons/38,080 lb, XCs were the heaviest with a maximum axle load of 19 1/2 tons). Unlike the XBs and XCs, the XAs had a Belpaire firebox. Most were built at Vulcan Foundry.

See the XC entry for discussion of the IRS design's several shortcomings including poor steaming and cracked frames. It must have been after the modifications suggested by a review committee that the XAs became the engine described by OS Nock (RWC V, pl 157) as "simple and straightforward, both for operation and maintenance, and have proved very successful in service."

See also [] notes.

Dr. Jonathan Smith of Iowa State ([] ) for data on this design.


Class IRS/YB (Locobase 4277)

Part of a series of designs created in the mid-1920s to meet Indian railway requirements.

[] notes that these had "...a wider firebox and other improvements to handle low-grade coal." The smaller of the two metre-gauge Pacific designs.

Data from builder Nasmyth & Wilson's diagram in C Hamilton Ellis The Lore of the Train (1971). Firebox heating surface includes 12.8 sq ft of arch tubes.


Class IRS/YC (Locobase 4278)

Data from No. 54, "'YC' Class Standard Passenger Engine and Tender for the Indian State Railways", Vulcan Foundry Locomotive Catalogue found on Flicker's Historical Locomotive Images website at [], last accessed 26 June 2021. See also Vulcan Magazine, Spring 1948, pp 14-16 (reproduced on [], visited 26 November 2004) for data and full description. (Many thanks to Jorge Cerezo Toledo for his 26 June 2021 email containing links to several sites including the Vulcan Catalogue referred to above.)

Part of a series of designs created in the mid-1920s to meet Indian railway requirements.

[] notes that these had "...a wider firebox and other improvements to handle low-grade coal." The larger of the two metre-gauge Pacific designs, it was still relatively small compared to other narrow-gauge 4-6-2s.

Although the article describes an order of 10 YCs for Burma, the design is identical to that of the IRS engines. The firebox heating surface includes 16 sq ft (1.49 sq m) from three arch tubes.


Class WP (Locobase 2480)

Data from "Class WL-Type 4-6-2 Light Passenger" locomotive diagram; "Indian Railway 5 ft 6 in Gauge-1955-4-6-2 (WL) brochure, Vulcan Foundry; and Shankar (members.tripod.com/shankaronline/wpglorymain.htm), dead link last checked 27 October 2018. Wayback machine url is [][], last accessed 13 December 2019.

Max axle load of 45,500 lb (OS Nock, RWC VI, Pl 98, says 41,440 lb).

The first sixteen of this ubiquitous express passenger design were built by Baldwin in 1946. They were an immediate success as a standard design that combined useful capacity with simplicity in operation. describes their graceful line that were led by the hemispherical cap which, often adorned with a silver star, became their hallmark. He then adds:"All beauty and no brains? Dear me, no. The WPs were good steamers and good pullers, with excellent steaming capabilities for efficient time keeping. They were ideal for the heavy and densly packed, but moderately paced trains."

Shankar says that the design goal was to improve on the XC class, but at a lower axle loading. Reducing the driver diameter to 67" and moving the driving axles as far back as possible accomplished this as well as generating the most horsepower at 45 mph. The firebox had a thermic syphon and two arch tubes to take full advantage of the capacious grate. Shankar also notes the 12 " (305 mm) diameter piston valves that travelled 7 1/2" (1/4" lead and 1 11/16" lap). WPs could hit 120 km/h (75 mph) and were booked at 105 km/h (65 mph). Burning "good coal", the engines were credited with 1,680 hp ; bad coal limited their output to 1,400 hp.

Baldwin delivered a total of 100 engines (73408-73423 in 1947.

Montreal Locomotive Works (120 - 77200-77259, 77345-77390 in 1949; 7576-77580 in 1950),

100 from the Canadian Locomotive Works, 30 from Austria's Vienna Lokomotiv Fabrik, 30 from Poland's Fabryka Locomotywim in Chrzanow and , beginning in 1963, from India's own Chittaranjan Works. The Indian-built WPs (WP/1) were heavier by 5 tons.

The [] (Indian Railways Fan Club website) notes that some refurbished WPs were exported to the Middle East.

NB: Direct heating surface is an estimate


Class X S1 (Locobase 20929)

Data from No. 56, "'X S1'' Class Fitted with 'Caprotti' Valve Gear Standard Passenger Engine and Tender for the Indian State Railways" and No. 57 same engine with Lentz valve gear, Vulcan Foundry Locomotive Catalogue found on Flicker's Historical Locomotive Images website at [], last accessed 26 June 2021; and Vulcan Foundry's brochure:"North Western Railways - Pakistan 4-6-2 X S1 and X S2", archived on the Vulcan Foundry website at [], last accessed 9 August 2021. For a full description of Paxman's promotion and production of Lentz gear for British and overseas customers, see "Lentz Valves for Locomotives" on Richard Carr's Paxman History Pages at [], last accessed 9 August 2021.

(Many thanks to Jorge Cerezo Toledo for his 26 June 2021 email containing links to several sites including the Vulcan Catalogue referred to above.)

These were modified XC-class ISR Pacifics (Locobase 2588) produced for the North Western Railways of India (in what later became West Pakistan).

At the time (1928), railroads across the globe explored several ways to increase performance and reduce fuel and water consumption by varying the number and size of cylinders (e.g. fitting three or four simple-expansion cylinders instead of the usual two) and trying out new types of valve gear.

The four engines in this order used Caprotti (S1) or Lentz rotary cam valves (S2). Caprotti's gear used a cam-actuated train to open and close poppet valves in the valve chests. Adopted widely in Italy, its success in Britain and the Raj proved much more limited. Lentz gear used a rotary drive to open and close poppet valves; see Locobase 20738 for a description of the setup.). Like the Caprotti, Lentz installations soon were removed once railways established that any difference in fuel economy could be reduced by revising existing Walschaert gear.

All four .The outside cylinders turned the second pair of coupled wheels and the inside cylinders drove the leading coupled axle. In addition the NWR set up one engine of each valve type with "the inside and outside cranks arranged in the usual way (i.e., the inside are at 180ñ to the outside), but the second engine of each class has the inside cranks at 135ñ to the outside, thus producing eight beats per revolution of the driving wheels."


Class XB (Locobase 2589)

Data from [] . One of three Indian Railways Standard (IRS) locomotives -- Most were built at Vulcan Foundry. Also see No. 47, "'XB' Class Standard Passenger Engine and Tender for the Indian State Railways", Vulcan Foundry Locomotive Catalogue found on Flicker's Historical Locomotive Images website at [], last accessed 26 June 2021. (Many thanks to Jorge Cerezo Toledo for his 26 June 2021 email containing links to several sites including the Vulcan Catalogue referred to above.)

Dr Sundar comments that the XB's design had many modern features, but manifested many shortcomings in service. The frame was prone to fracturing. "One specimen had 9 frame fractures in nine years. The 18 XBs in the East Bengal Railway spent 3 out of 8 years in the repair shop!" The XB was a fragile beast: "All X series Pacifics in another railway were pulled off their duties because of chronic coupling rod failures. The firebox tubeplates had to be frequently changed due to cracking in the radius of the top flanges."

And they weren't kind to the track either. Their tendency to hunt from side to side wracked the rails.

But the low heating surface to cylinder volume ratio points to the design's poor steaming capability. When tested, an XB was unable to pull a 350-ton trainload at 60 mph (97 km/h).

It was an XB derailment in 1937 at Bihta (more than 100 lives lost) that showed up the design's shortcomings. The derailment led to a detailed investigation, which led to an effective solution, according to [] sh (18 April 2003):

"It was a Frenchman Robert Leguille who came up with the solutions that eliminated the XB's derailing propensities. He and Cox examined the flange forces measurements made by two British engineers and decided that the leading and trailing bogies needed much stiffer side control springs with better damping. Experiments proved them right. The XBs belonging to the BB&CIR and the M&SM railway companies were modified according to their recommendations and no more derailments happened. XBs in other railways were relegated to slow trains. Many of them survived into the 1980s proving that they had become useful locomotives."

(XAs went 13 tons/29,120 lb, XCs were the heaviest with a maximum axle load of 19 1/2 tons).

See also [] notes.


Class XC (Locobase 2588)

Data from "Mountain (4-8-2) Type Locomotive", Superheater Company, Ltd Brochure, p. seventeen [sic]. p. sixteen [sic]; and "Standard Passenger Engine and Tender for the Indian State Railways", Vulcan Foundry Locomotive Catalogue, No. 50, found on Flicker's Historical Locomotive Images website at []. See also Brian Hollingsworth, The Illustrated Encyclopedia of the World's Steam Passenger Locomotives (London: Salamander Books, 1982). (Many thanks to Jorge Cerezo Toledo for his 26 June 2021 email containing links to several sites including the Vulcan Catalogue referred to above.)

One of three Indian Railways Standard (IRS) locomotives, XCs were the heaviest with a maximum axle load of 19 1/2 tons. (XAs went 13 tons/29,120 lb, XBs weighed in at 17 tons/38,080 lb). Most were built at Vulcan Foundry.

Although much was expected of them, Hollingsworth wrote, they fell well short. They steamed badly despite their large grate, substantial direct heating surface area that included four arch tubes. They offered large boilers and generous superheater area and valve events in their 12" (305 mm) piston valves that should have been satisfactory. Instead they were known for their sluggish performance. IRS engines rode badly "to the point not of discomfort but of danger." The boiler often showed cracks and both the frame and motion suffered breaks as well.

Much of this was easily remedied once the problem was identified, but only after 11 years of construction and a serious derailment was anything done.

See also [] notes.


Class YP (Locobase 2603)

Data from Hollingsworth (1982) and the Benin Tourist Railway Project, Http://www.livesteaming.com/Benin-Togo.htm, last accesssed 5 July 2009.

A prolific and successful metre-gauge designed by Baldwin, which had done so well with the broad-gauge WP. Indeed, Hollingsworth (1982) comments that YPs are essentially 2/3-scale replicas of a standard US Pacific. The firebox heating surface included a thermic syphon contributing 33.14 sq ft.

Simply designed, these engines were built in large numbers by Krauss-Maffei (200), North British (100) and Tata Engineering & Locomotive Co of Jamshedpur (571). The last rolled out only in 1970 and many remain in service all over India. The Benin Tourist Railway Project was a 21st-Century plan to use 2 YPs (2257 and 2684) stored after overhaul in Lome, Togo to boost revenue for the tiny West African nation of Benin (formerly Dahomey)

Principal Dimensions by Steve Llanso of Sweat House Media

ClassIGR/ZPIRS/XAIRS/YBIRS/YCWP
Locobase ID4295 2590 4277 4278 2480
RailroadIndia Government RailwaysIndia Government RailwaysIndia Government RailwaysIndia Government RailwaysIndia Government Railways
CountryIndiaIndiaIndiaIndiaIndia
Whyte4-6-24-6-24-6-24-6-24-6-2
Number in Class113755
Road Numbers7000-7754
Gauge2'6"5'6"MetreMetre5'6"
Number Built113755
Builderseveralseveralseveralseveralseveral
Year1927192519251946
Valve GearWalschaertWalschaertStephensonWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m) / 4.0110.50 / 3.2010.50 / 3.2012.25 / 3.73
Engine Wheelbase (ft / m) / 10.2427.83 / 8.4828.33 / 8.6336.25 / 11.05
Ratio of driving wheelbase to overall engine wheelbase 0.38 0.37 0.34
Overall Wheelbase (engine & tender) (ft / m) / 20.3050 / 15.2453.29 / 16.2468.25 / 20.80
Axle Loading (Maximum Weight per Axle) (lbs / kg)29,120 / 13,20926,88040,785 / 18,500
Weight on Drivers (lbs / kg)47,040 / 21,33787,360 / 39,62664,960 / 29,46580,640 / 36,578121,501 / 55,112
Engine Weight (lbs / kg)82,880 / 37,594150,080 / 68,075116,480 / 52,835130,480 / 59,185227,360 / 103,129
Tender Loaded Weight (lbs / kg)94,304 / 42,77687,920 / 39,880161,200 / 73,119
Total Engine and Tender Weight (lbs / kg)244,384 / 110,851218,400 / 99,065388,560 / 176,248
Tender Water Capacity (gals / ML)3600 / 13.647199 / 27.27
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)9 / 816.50 / 15
Minimum weight of rail (calculated) (lb/yd / kg/m)26 / 1349 / 24.5036 / 1845 / 22.5068 / 34
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)36 / 91461.50 / 156257 / 144857 / 144867 / 1702
Boiler Pressure (psi / kPa)210 / 14.50180 / 12.40180 / 12.40180 / 12.40210 / 14.50
High Pressure Cylinders (dia x stroke) (in / mm)12" x 18" / 305x45718" x 26" / 457x66016" x 24" / 406x61017.5" x 24" / 445x61020.25" x 27.99" / 514x711
Tractive Effort (lbs / kg)12,852 / 5829.5820,957 / 9505.9516,492 / 7480.6519,729 / 8948.9330,579 / 13870.42
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.66 4.17 3.94 4.09 3.97
Heating Ability
Tubes (number - dia) (in / mm)75 - 2.25" / 5792 - 2.25" / 57116 - 2.25" / 57
Flues (number - dia) (in / mm)18 - 5.375" / 13721 - 5.25" / 13338 - 5.5" / 140
Flue/Tube length (ft / m) / 5.6415 / 4.5715.5017.08 / 5.21
Firebox Area (sq ft / m2)136.80 / 12.71164 / 15.24255 / 23.69
Grate Area (sq ft / m2)18 / 1.6732 / 2.9723.10 / 2.1531 / 2.8846.05 / 4.28
Evaporative Heating Surface (sq ft / m2)525 / 48.791399 / 129.971169 / 108.641448 / 134.572357 / 218.97
Superheating Surface (sq ft / m2)130 / 12.08348 / 32.33265 / 24.63322 / 29.93725 / 67.35
Combined Heating Surface (sq ft / m2)655 / 60.871747 / 162.301434 / 133.271770 / 164.503082 / 286.32
Evaporative Heating Surface/Cylinder Volume222.82182.69209.31216.72225.91
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation37805760415855809671
Same as above plus superheater percentage453669124906658411,991
Same as above but substitute firebox area for grate area29,05634,83466,402
Power L112,97613,22222,829
Power MT1321.141084.431242.69

Principal Dimensions by Steve Llanso of Sweat House Media

ClassX S1XBXCYP
Locobase ID20929 2589 2588 2603
RailroadIndia Government RailwaysIndia Government RailwaysIndia Government RailwaysIndia Government Railways
CountryIndiaIndiaIndiaIndia
Whyte4-6-24-6-24-6-24-6-2
Number in Class49972871
Road Numbers
Gauge5'6"5'6"5'6"metre
Number Built49972871
Builderseveralseveralseveralseveral
Year1930192719271949
Valve GearCaprottiWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)13.17 / 4.0113.17 / 4.0113.17 / 4.0110 / 3.05
Engine Wheelbase (ft / m)35.42 / 10.8033.33 / 10.1635.08 / 10.6929.62 / 9.03
Ratio of driving wheelbase to overall engine wheelbase 0.37 0.40 0.38 0.34
Overall Wheelbase (engine & tender) (ft / m)67.17 / 20.4766.37 / 20.2376.12 / 23.2053.59 / 16.33
Axle Loading (Maximum Weight per Axle) (lbs / kg)38,080 / 17,27323,634 / 10,720
Weight on Drivers (lbs / kg)144,480 / 65,535114,240 / 51,818132,160 / 59,94769,269 / 31,420
Engine Weight (lbs / kg)241,920 / 109,733202,160 / 91,698217,280 / 98,557126,788 / 57,510
Tender Loaded Weight (lbs / kg)143,360 / 65,027145,197 / 65,860174,72090,940 / 41,250
Total Engine and Tender Weight (lbs / kg)385,280 / 174,760347,357 / 157,558392,000 / 98,557217,728 / 98,760
Tender Water Capacity (gals / ML)5400 / 20.457200 / 27.277200 / 27.273604 / 13.65
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)11 / 1016.50 / 1516.50 / 1512.30 / 11
Minimum weight of rail (calculated) (lb/yd / kg/m)80 / 4063 / 31.5073 / 36.5038 / 19
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)74 / 188074 / 188074 / 188054 / 1372
Boiler Pressure (psi / kPa)225 / 15.50180 / 12.40190 / 12.40210.30 / 14.50
High Pressure Cylinders (dia x stroke) (in / mm)16" x 26" / 406x660 (4)21.5" x 28" / 546x71123" x 28" / 584x71115.24" x 24.02" / 387x610
Tractive Effort (lbs / kg)34,404 / 15605.4126,761 / 12138.6032,326 / 14662.8418,467 / 8376.50
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.20 4.27 4.09 3.75
Heating Ability
Tubes (number - dia) (in / mm)121 - 2.25" / 5795 - 2.25" / 57129 - 2.25" / 5767 - 2.008" / 51
Flues (number - dia) (in / mm)32 - 5.5" / 14022 - 5.5" / 14030 - 5.5" / 14026 - 5.236" / 133
Flue/Tube length (ft / m)18.50 / 5.6418.50 / 5.6418.50 / 5.6413.12 / 4
Firebox Area (sq ft / m2)207 / 19.23198 / 18.39229 / 21.27195.62 / 18.18
Grate Area (sq ft / m2)51 / 4.7445 / 4.1851 / 4.7427.98 / 2.60
Evaporative Heating Surface (sq ft / m2)2397 / 222.691840 / 170.942429 / 225.661112 / 103.35
Superheating Surface (sq ft / m2)688 / 63.92463 / 43.01636 / 59.09331 / 30.76
Combined Heating Surface (sq ft / m2)3085 / 286.612303 / 213.953065 / 284.751443 / 134.11
Evaporative Heating Surface/Cylinder Volume198.08156.39180.40219.27
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,475810096905884
Same as above plus superheater percentage14,000972011,7257238
Same as above but substitute firebox area for grate area56,82242,76852,64750,601
Power L122,07013,20216,18218,919
Power MT1010.30764.32809.821806.40

All material Copyright © SteamLocomotive.com
Wes Barris