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. Works numbers were 18 in 1897; 44-46, 52 in 1902; 56-57 in 1903
These radial tanks were rebuilds of rebuilds. At first, in 1892, the NZR shops enlarged the F class with larger cylinders and side tanks replacing the saddle tank; these were the Fa. In 1897, a new locomotive was built to a modified design that was further modified with a trailing axle and a piston valve set into the slide-valve chest. In 1902, six more followed from Addington.
Thirteen more Fb were created when Fa were modified beginning in 1903, after which all 20 locomotives were designated Fb. Road numbers were 41, 157, 179, 182, 186, 226, 242, 244, 247, 250-251, and 276.
The builder replaced the slide valves with piston valves and internal axles bearings in the trailing truck with outside journal boxes.
| Principal Dimensions by Steve Llanso of Middle Run Media | |
|---|---|
| Class | Fb |
| Locobase ID | 5171 |
| Railroad | New Zealand Railways |
| Country | New Zealand |
| Whyte | 0-6-2T |
| Number in Class | 20 |
| Road Numbers | 9, 315, 372-376+12 Fa conversions |
| Gauge | 3'6" |
| Number Built | 8 |
| Builder | NZGR |
| Year | 1897 |
| Valve Gear | Walschaert |
| Locomotive Length and Weight | |
| Driver Wheelbase (ft / m) | 10.50 / 3.20 |
| Engine Wheelbase (ft / m) | 16.50 / 5.03 |
| Ratio of driving wheelbase to overall engine wheelbase | 0.64 |
| Overall Wheelbase (engine & tender) (ft / m) | |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | |
| Weight on Drivers (lbs / kg) | 56,448 / 25,604 |
| Engine Weight (lbs / kg) | 65,632 / 29,770 |
| Tender Loaded Weight (lbs / kg) | |
| Total Engine and Tender Weight (lbs / kg) | |
| Tender Water Capacity (gals / ML) | |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | 31 / 15.50 |
| Geometry Relating to Tractive Effort | |
| Driver Diameter (in / mm) | 36.50 / 927 |
| Boiler Pressure (psi / kPa) | 160 / 1100 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 12" x 18" / 305x457 |
| Tractive Effort (lbs / kg) | 9658 / 4380.80 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 5.84 |
| Heating Ability | |
| Tubes (number - dia) (in / mm) | |
| Flues (number - dia) (in / mm) | |
| Flue/Tube length (ft / m) | |
| Firebox Area (sq ft / m2) | |
| Grate Area (sq ft / m2) | 10.70 / 0.99 |
| Evaporative Heating Surface (sq ft / m2) | 530 / 49.26 |
| Superheating Surface (sq ft / m2) | |
| Combined Heating Surface (sq ft / m2) | 530 / 49.26 |
| Evaporative Heating Surface/Cylinder Volume | 224.94 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 1712 |
| Same as above plus superheater percentage | 1712 |
| Same as above but substitute firebox area for grate area | |
| Power L1 | |
| Power MT | |