New Zealand Government Railways 4-6-4 Locomotives in New_Zealand


Class Details by Steve Llanso of Sweat House Media

Class Wab (Locobase 2490)

Data from John Garner's comprehensive site at http://www.trainweb.org/nzsteam ... (October 2002). See also "New Superheater Tank Engine No. 686, New Zealand Gov't Rys", Locomotive Magazine, Volume 24, No. 312 (15 August 1918).

Basically a tank-engine variant of the Ab Pacifics (Locobase 2489) designed by the NZGR's chief mechanical engineer H H Jackson, these were used in suburban commuting service in Auckland and Wellington. Some also operated between Taihape and Taumarunui on the North Island. Others were used in short-haul mainline service on the South Island between Dunedin and Oamaru, where the grade could reach 2%.

In addition to the large side tanks, the boiler had an extra sand dome for more sanding capacity. As the tank engines were replaced by larger 4-8-2 tender engines, those on the South Island were converted to 4-6-2 Abs.

One preserved engine -- 794 -- racked up 837,400 miles in demanding service before it was retired.


Class We (Locobase 5189)

Data from John Garner's comprehensive site at http://www.trainweb.org/nzsteam ... (October 2002).

These three tanks were rebuilt from B-class 4-8-0s (Locobase 9568) for helper service over the Rimutaka Incline between Upper Hutt and Cross Creek.


Class Wg (Locobase 5191)

Data from John Garner's comprehensive site at http://www.trainweb.org/nzsteam ... (October 2002). supplemented by diagrams supplied by NZGR's general manager T Ronayne in "Locomotive Building in New Zealand", Railway Engineer, Volume 34, No 5 (May 1913), pp. 183-186.

Handsome follow-ons to the Wfs, all from Hillside. These were slightly larger, but more important, they put more than 6,000 additional pounds on the drivers. Again the size and arrangement proved quite useful and these engines served for years as both commuter locomotives and mail-train engines.


Class Wg (Locobase 20576)

Data from "New Engines for the New Zealand Government Rys", Locomotive Magazine, Volume XXIII [23] (15 February 1917), p. 20.

Locobase 5191 shows the original Wg class engines with saturated boilers.


Class Ws (Locobase 5192)

Data from John Garner's comprehensive site at http://www.trainweb.org/nzsteam ... (October 2002).

Like the 1917 Wabs, these were also tank-engine variants of the Ab Pacifics, but designed from the outset for suburban service. Note the difference in superheat. The class was later (1932-1933) redesignated Wab and grouped with the others.


Class Ww (Locobase 5193)

Data from John Garner's comprehensive site at http://www.trainweb.org/nzsteam ... (October 2002).

Essentially superheated Wg engines, these had the usual differences of larger pistons and lower boiler pressure. They served Wellington and Auckland suburban traffic and some main-line and branch-line runs as well. They were rebuilt in the 1950-1960 era with higher-pitched boilers.

Principal Dimensions by Steve Llanso of Sweat House Media
ClassWabWeWgWgWs
Locobase ID2490 5189 5191 20,576 5192
RailroadNew Zealand Government RailwaysNew Zealand Government RailwaysNew Zealand Government RailwaysNew Zealand Government RailwaysNew Zealand Government Railways
CountryNew ZealandNew ZealandNew ZealandNew ZealandNew Zealand
Whyte4-6-4T4-6-4T4-6-4T4-6-4T4-6-4T
Number in Class30322113
Road Numbers166, 170, 479-496491
Gauge3'6""3'6""3'6""3'6""Std
Number Built162213
BuilderseveralNZGRNZGRNZGRseveral
Year19171902191019171923
Valve GearWalschaertWalschaertWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)10 / 3.059 / 2.7410 / 3.0510 / 3.0510 / 3.05
Engine Wheelbase (ft / m)33.08 / 10.0829.09 / 8.8729.62 / 9.0329.62 / 9.0333.09 / 10.09
Ratio of driving wheelbase to overall engine wheebase 0.30 0.31 0.34 0.34 0.30
Overall Wheelbase (engine & tender) (ft / m)33.08 / 10.0829.09 / 8.8729.62 / 9.0329.62 / 9.0333.09 / 10.09
Axle Loading (Maximum Weight per Axle) (lbs / kg)31,360 / 14,225
Weight on Drivers (lbs / kg)94,080 / 42,67478,400 / 35,56266,528 / 30,17769,440 / 31,49782,432 / 37,391
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)160,160123,648112,000112,000160,160
Tender Water Capacity (gals / ML)2040 / 7.732400 / 9.091680 / 6.361680 / 6.362040 / 7.73
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT) 3.30 / 3 2.20 / 2 2.20 / 2 2.20 / 2 3.30 / 3
Minimum weight of rail (calculated) (lb/yd / kg/m)52 / 2644 / 2237 / 18.5039 / 19.5046 / 23
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)54 / 137242.50 / 108045 / 114345 / 114354 / 1372
Boiler Pressure (psi / kPa)200 / 13.80180 / 12.40200 / 13.80200 / 13.80200 / 13.80
High Pressure Cylinders (dia x stroke) (in / mm)17" x 26" / 432x66016" x 22" / 406x55914" x 22" / 356x55918.5" x 22" / 470x55917" x 26" / 432x660
Tractive Effort (lbs / kg)23,655 / 10729.7420,275 / 9196.6016,290 / 7389.0328,445 / 12902.4523,655 / 10729.74
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.98 3.87 4.08 2.44 3.48
Heating Ability
Firebox Area (sq ft / m2)123 / 11.4388 / 8.1888 / 8.18
Grate Area (sq ft / m2)33 / 3.0717.50 / 1.6316.90 / 1.5716.90 / 1.5733 / 3.07
Evaporative Heating Surface (sq ft / m2)1146 / 106.471037 / 96.38738 / 68.56560 / 52.031148 / 106.69
Superheating Surface (sq ft / m2)277 / 25.73258 / 23.97183 / 17.01
Combined Heating Surface (sq ft / m2)1423 / 132.201037 / 96.38738 / 68.56818 / 761331 / 123.70
Evaporative Heating Surface/Cylinder Volume167.78202.55188.2881.82168.07
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation66003150338033806600
Same as above plus superheater percentage78543150338044627524
Same as above but substitute firebox area for grate area29,27417,60023,232
Power L111,21045087280
Power MT788.07448.16693.39

Principal Dimensions by Steve Llanso of Sweat House Media
ClassWw
Locobase ID5193
RailroadNew Zealand Government Railways
CountryNew Zealand
Whyte4-6-4T
Number in Class51
Road Numbers
Gauge3'6""
Number Built51
BuilderNZGR
Year1913
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)10 / 3.05
Engine Wheelbase (ft / m)29.62 / 9.03
Ratio of driving wheelbase to overall engine wheebase 0.34
Overall Wheelbase (engine & tender) (ft / m)29.62 / 9.03
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)66,528 / 30,177
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)115,360
Tender Water Capacity (gals / ML)1680 / 6.36
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT) 2.20 / 2
Minimum weight of rail (calculated) (lb/yd / kg/m)37 / 18.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)45 / 1143
Boiler Pressure (psi / kPa)180 / 12.40
High Pressure Cylinders (dia x stroke) (in / mm)15.5" x 22" / 394x559
Tractive Effort (lbs / kg)17,971 / 8151.52
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.70
Heating Ability
Firebox Area (sq ft / m2)
Grate Area (sq ft / m2)16.90 / 1.57
Evaporative Heating Surface (sq ft / m2)526 / 48.88
Superheating Surface (sq ft / m2)131 / 12.17
Combined Heating Surface (sq ft / m2)657 / 61.05
Evaporative Heating Surface/Cylinder Volume109.48
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation3042
Same as above plus superheater percentage3650
Same as above but substitute firebox area for grate area
Power L1
Power MT

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