New Zealand Government Railways 4-8-0 Locomotives in New_Zealand


Class Details by Steve Llanso of Sweat House Media

Class B (Locobase 9568)

Data from Howell, Comparative Statistics of the Australasian Railways, Journal of the Royal Statistical Society, March 1899, pp. 98-99 and John Garner's [], last accessed 7 September 2008.

Sharp, Stewart of Glasgow contributed 4 (works #4508-4511) in 1899 and the NZR's own Addington shops built 6 (works #24, 26, 43, 54-56 in 1899 to 1903)) of these sizable Twelve-wheelers. Garner's comment about their design summarizes what one can tell from the specs and from a photograph: "Mechanically the 'B' was years ahead of its time, with a new simple design of piston valve and a modified Walschaerts valve gear. For their time the 'B's were powerful brutes and rated to haul 600 ton goods trains on easy grades, and could handle 220 tons over the steep grades north of Dunedin."

They were obviously worth retaining and most put in 6 decades of service, although three were converted to 4-6-4T class We in 1902 (see Locobase 5189). Four were later refitted with a new boiler fitted with a wide firebox over a 18-year period; three more


Class Ba (Locobase 5164)

Data from John Garner's comprehensive site at http://www.trainweb.org/nzsteam ... (October 2002). A rare narrow-gauge 12-wheeler, these locomotives were intended for heavy freight work at speeds no greater than 30 mph. Garner notes, however, that they also hauled passenger trains in the Otago area.

Of the 10, 2 were rebuilt in 1928 with larger fireboxes and boilers to raise steaming capacity to main-line requirements. http://www.websnz.com/mse/ba552.php3 (visited 21 May 2004) notes that this was a substantial effort. The boiler's centerline was raised from 6' 3" (1.9 m) to 7' 4" (2.23 m), the grate area enlarged to 26.4 sq ft (2.45 sq m), and pressure raised to 200 psi (14.06 bar). Tractive effort climbed to 21,200 lb (9,616 kg).

Obviously, this was not an urgent requirement as the other three to be made over were only modified in 1948-1949. Rated to haul 700-750 tons on the level, a wide-firebox Ba could surmount the notorious Mihiwaka Bank (north of Dunedin) with 270 tons, 50 tons better than one of the other members of the class fitted with a narrow-firebox boiler


Class Bb (Locobase 5165)

Data from John Garner's comprehensive site at http://www.trainweb.org/nzsteam ... (October 2002). An obvious follow-on class to the Bas with cylinders 1" larger in diameter, these 12-wheelers had the same small boilers and low factor of adhesion. Garner says that 10 of these engines were given shunting duties, where they were quite successful. That success led to the conversion of the entire class between 1932 and 1938.

Principal Dimensions by Steve Llanso of Sweat House Media
ClassBBaBb
Locobase ID9568 5164 5165
RailroadNew Zealand Government RailwaysNew Zealand Government RailwaysNew Zealand Government Railways
CountryNew ZealandNew ZealandNew Zealand
Whyte4-8-04-8-04-8-0
Number in Class101030
Road Numbers178, 198, 302-309
Gauge3'6""3'6""3'6""
Number Built101030
BuilderseveralAddingtonA G Price
Year189919111915
Valve GearWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)12.5012.33 / 3.7612.33 / 3.76
Engine Wheelbase (ft / m)2322.70 / 6.9222.33 / 6.81
Ratio of driving wheelbase to overall engine wheebase 0.54 0.54 0.55
Overall Wheelbase (engine & tender) (ft / m)44.83 / 13.6645.20 / 13.78
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)71,00872,352 / 32,81872,800 / 33,022
Tender Loaded Weight (lbs / kg)49,280 / 22,35357,120 / 25,90957,120 / 25,909
Total Engine and Tender Weight (lbs / kg)145,376 / 65,941155,456 / 70,514154,560 / 70,107
Tender Water Capacity (gals / ML)2040 / 7.732040 / 7.732040 / 7.73
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT) 4.40 / 4 4.40 / 4
Minimum weight of rail (calculated) (lb/yd / kg/m)30 / 1530 / 1530 / 15
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)42.50 / 108042.50 / 108042.50 / 1080
Boiler Pressure (psi / kPa)175 / 12.10175 / 12.10175 / 12.10
High Pressure Cylinders (dia x stroke) (in / mm)16" x 22" / 406x55916" x 22" / 406x55917" x 22" / 432x559
Tractive Effort (lbs / kg)19,712 / 8941.2219,712 / 8941.2222,253 / 10093.80
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.60 3.67 3.27
Heating Ability
Firebox Area (sq ft / m2)109 / 10.13
Grate Area (sq ft / m2)17.30 / 1.6116.70 / 1.5516.80 / 1.56
Evaporative Heating Surface (sq ft / m2)1048 / 97.40788 / 73.23724 / 67.29
Superheating Surface (sq ft / m2)206 / 19.14208 / 19.33
Combined Heating Surface (sq ft / m2)1048 / 97.40994 / 92.37932 / 86.62
Evaporative Heating Surface/Cylinder Volume204.70153.92125.27
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation302829232940
Same as above plus superheater percentage302835363587
Same as above but substitute firebox area for grate area19,075
Power L13857
Power MT479.00

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