Royal State Railways Beyer-Garratt Locomotives in Thailand


Class Details by Steve Llanso of Sweat House Media

Class 451 (Locobase 797)

Double Mikado Garratts (Works # 21618-21623).

Data from []

(6 September 2005).

An insight into Thai Garratt operations comes from the Thai Railway website's historical pages [], accessed 8 September 2005. Noting that the Hanomag 0-10-0s proved incapable of handling trains up the 2.6% ruling grade between Kaeng Khoi to Pak Chong (55 km/34 miles), the RSR reviewed the successful operation of Garratts in India and ordered six of its own (No. 451-456) from Henschel. The tonnage problem was solved, but the design's firebox proved undersized for steaming up the big hills as was water tankage and fuel bunkerage.

In 1937, the RSR added two more from Henschel; see Locobase 4398.


Class 457 (Locobase 4398)

Data from []

(6 September 2005).

Double Mikado Garratts (works #s 23109-23110) delivered as a supplement to the six supplied by Henschel in 1929. These last two had bigger boilers and grates.

According to the Thai Railway website's historical pages -- [], accessed 8 September 2005 -- "[T]he second batch ... were a much improved version .. due to increased firewood and water capacity and an enormous firebox."

Unfortunately for the crews, wood fuel cannot be automatically stoked, so their workload increased. As a result, the class was "... not a very popular class for Thai railway workers ... so no further orders for Garatte (sic). Instead the railway dropped the tonnage loadings for the trains on that section to a level that allowed the standard Japanese 2-8-2 (for once the appropriately named Mikados) that entered service on the RSR before, during, and after World War II. .

457 was preserved after its 1964 retirement in Bangsue. It was later moved to Kanchanaburi where conditions for exhibition and preservation were considerably more favorable.

Principal Dimensions by Steve Llanso of Sweat House Media

Class451457
Locobase ID797 4398
RailroadRoyal State RailwaysRoyal State Railways
CountryThailandThailand
Whyte2-8-2+2-8-22-8-2+2-8-2
Number in Class62
Road Numbers451-456457-458
GaugeMetreMetre
Number Built82
BuilderHenschel & SohnHenschel & Sohn
Year19291937
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)
Engine Wheelbase (ft / m)
Ratio of driving wheelbase to overall engine wheelbase
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)23,072 / 10,465
Weight on Drivers (lbs / kg)181,112 / 82,151182,985 / 83,001
Engine Weight (lbs / kg)258,496 / 117,252268,965 / 122,001
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)258,496 / 117,252268,965 / 122,001
Tender Water Capacity (gals / ML)4752 / 18
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 5.50 / 5
Minimum weight of rail (calculated) (lb/yd / kg/m)38 / 1938 / 19
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)41.40 / 105241 / 1041
Boiler Pressure (psi / kPa)185 / 12.80185 / 12.80
High Pressure Cylinders (dia x stroke) (in / mm)17" x 21.75" / 432x552 (4)17" x 21.75" / 432x552 (4)
Tractive Effort (lbs / kg)47,750 / 21659.0648,216 / 21870.44
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.79 3.80
Heating Ability
Tubes (number - dia) (in / mm)
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)
Firebox Area (sq ft / m2)151 / 14.03
Grate Area (sq ft / m2)40.70 / 3.7846.27 / 4.30
Evaporative Heating Surface (sq ft / m2)1593 / 148.051808 / 168.03
Superheating Surface (sq ft / m2)458 / 42.57581 / 54
Combined Heating Surface (sq ft / m2)2051 / 190.622389 / 222.03
Evaporative Heating Surface/Cylinder Volume139.40158.21
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation75308560
Same as above plus superheater percentage918610,614
Same as above but substitute firebox area for grate area34,081
Power L17227
Power MT703.78

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