Burma Railways classes N and Ns
Burma 1911 22 produced
The class N of the Burma Railways designated 17 Mallets built by North British in four batches between 1911 and 1921. With an 0-6-6-0 wheel arrangement, they had all weight available for traction. Nevertheless, they were not only intended for freight service, but also for passenger service.
Their service area was the Lashio branch and the Southern Shan states. Even though they had a huge pulling power, they had to be assisted by 2-6-2T locomotives on steeper sections. In 1924 Beardmore built five superheated Ns class locomotives and the 17 others were rebuilt in the same form. It didn't take long until they were superseded by the Garratts starting with the GA.I.
Technical data
General
| Property | N | Ns |
|---|---|---|
| Built | 1911-1915, 1921 | 1924 |
| Manufacturers | North British | Beardmore |
| Wheel arrangement | 0-6-6-0 (Erie) | |
| Gauge | 1,000 mm (Meter gauge) | |
Dimensions and weights
| Property | N | Ns |
|---|---|---|
| Length | 18.96 m | |
| Wheelbase | 7.39 m | |
| Total wheelbase | 14.81 m | |
| Service mass | 59.1 t | 61.5 t |
| Adhesion mass | 59.1 t | 61.5 t |
| Total mass | 90.9 t | 159.4 t |
| Rigid wheelbase | 2.52 m | |
| Water capacity | 9,093 l | |
| Fuel capacity | 6.1 t (coal) | 11.2 t (coal) |
Boiler
| Property | N | Ns |
|---|---|---|
| Grate area | 3.066 m² | |
| Firebox surface | 10.684 m² | |
| Tube heating surface | 129.879 m² | 99.499 m² |
| Evaporative heating surface | 140.562 m² | 100.521 m² |
| Total heating surface | 140.6 m² | 129.2 m² |
| Superheater surface | 28.707 m² | |
Power plant
| Property | N | Ns |
|---|---|---|
| Driver diameter | 991 mm | |
| Boiler pressure | 12.4 bar | |
| Expansion type | compound | |
| Cylinders | four, HP: 394 x 508 mm and LP: 616 x 508 mm | four, HP: 406 x 508 mm and LP: 616 x 508 mm |
Power
| Property | N | Ns |
|---|---|---|
| Power source | steam | |
| Estimated power | 597 kW (812 PS) | 746 kW (1,014 PS) |
| Starting effort | 119.1 kN | 124.5 kN |
| Starting effort simple | 142.9 kN | 149.4 kN |
Calculated values
| Property | N | Ns |
|---|---|---|
| Factor of adhesion | 1 : 4.87 | 1 : 4.84 |
| Optimal speed | 31 km/h | 37 km/h |
| Power-to-weight ratio | 10.1 kW/t | 12.1 kW/t |
| Heating Surface Equivalent | 194.0 m² | 221.0 m² |
| Cylinder volume/HSE | 1 : 1,417.94 | 1 : 1,281.19 |
| Adhesive weight/Total | 1 : 1.00 | |
| Tractive force/Heating surface | 1 : 17.69 | 1 : 20.12 |
| Grate area/Heating surface | 1 : 45.85 | 1 : 42.15 |
| Firebox/Tube surface | 1 : 12.16 | 1 : 9.31 |
| Total/Superheater | 1 : 3.50 | |
