Tasmanian Government 4-6-2 Locomotives in Australia


Class Details by Steve Llanso of Sweat House Media

Class M (Locobase 8580)

Data from [link], and [link], all accessed 14 July 2007.

Pipe-festooned Pacific based on the Indian Government Railway's YB class that fulfilled all the requirements for this twisting, hilly narrow-gauge line. Like the Vulcan Foundry H-class 4-8-2s described on Locobase 8579, these Pacifics (works #7421-7430) had cast-steel SCOA-P drivers and roller bearings on every axle including the 4 under the tender, the main (connecting) rod, and the side (coupling) rods. Unlike the Hs, however, these engines had Belpaire fireboxes.

The Hobart-Launceston passenger service needed light but powerful engines, notes OS Nock (RWC VI, pl. 106), so this design used welded construction for such components as the inner steel liner to the Belpaire firebox, ashpan, and parts of the tender's tank. Line curvature is as tight as 330 ft radius, "and personal observation from the footplate has confirmed that they do ride these severe curves both smoothly and comfortably."

Four were rebuilt as MAs for freight work; see Locobase 2872.

Retirements came in the early 1960s, although M5 remained in service until 1971 as a suburban-traffic, special-service engine.


Class MA (Locobase 2872)

Data from [link], and [link], accessed 14 July 2007.

In 1957-58, four of the M-class Pacific engines were retrofitted with 48" drivers taken from Garratt locomotives and smaller pony-truck wheels. A change in weight distribution added a little more than 1 long ton to the adhesion weight. Tractive effort went up, but they were had a significantly lower factor of adhesion.

These were designated MA 1-4 and were the ex-M8, M1, M6, and M2, respectively. They tackled the more challenging North East line.

Principal Dimensions by Steve Llanso of Middle Run Media
ClassMMA
Locobase ID8580 2872
RailroadTasmanian GovernmentTasmanian Government
CountryAustraliaAustralia
Whyte4-6-24-6-2
Number in Class104
Road NumbersM1-M10MA1-MA4
Gauge3'6"3'6"
Number Built10
BuilderRStephenson & HawthornsTGR
Year19521957
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)10.50 / 3.2020.75 / 6.32
Engine Wheelbase (ft / m)27.92 / 8.5161.83 / 18.85
Ratio of driving wheelbase to overall engine wheelbase 0.38 0.34
Overall Wheelbase (engine & tender) (ft / m)51.54 / 15.7168.50 / 20.88
Axle Loading (Maximum Weight per Axle) (lbs / kg)22,848 / 10,36423,520 / 10,669
Weight on Drivers (lbs / kg)67,732 / 30,72370,000 / 31,752
Engine Weight (lbs / kg)121,268 / 55,006120,960 / 54,867
Tender Loaded Weight (lbs / kg)94,976 / 43,08090,846 / 41,207
Total Engine and Tender Weight (lbs / kg)216,244 / 98,086211,806 / 96,074
Tender Water Capacity (gals / ML)4800 / 18.18
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) 6.60 / 6
Minimum weight of rail (calculated) (lb/yd / kg/m)38 / 1939 / 19.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)55 / 139748 / 1219
Boiler Pressure (psi / kPa)180 / 1240185 / 1280
High Pressure Cylinders (dia x stroke) (in / mm)16" x 24" / 406x61016" x 24" / 406x610
Tractive Effort (lbs / kg)17,091 / 7752.3620,128 / 9129.92
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.96 3.48
Heating Ability
Tubes (number - dia) (in / mm)68 - 2.25" / 5768 - 2.25" / 57
Flues (number - dia) (in / mm)18 - 5.25" / 13318 - 5.25" / 133
Flue/Tube length (ft / m)15.15 / 4.6215.15 / 4.62
Firebox Area (sq ft / m2)136.50 / 12.69136.50 / 12.69
Grate Area (sq ft / m2)23.10 / 2.1523.10 / 2.15
Evaporative Heating Surface (sq ft / m2)1109 / 103.071109 / 103.07
Superheating Surface (sq ft / m2)265 / 24.63265 / 24.63
Combined Heating Surface (sq ft / m2)1374 / 127.701374 / 127.70
Evaporative Heating Surface/Cylinder Volume198.57198.57
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation41584274
Same as above plus superheater percentage49485085
Same as above but substitute firebox area for grate area29,23830,050
Power L112,33911,067
Power MT1204.871045.65

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