Northern Pacific classes W-3 and W-5
Spokane, Portland & Seattle class O-3
United States 1913 160 produced
The class W-3 was created in 1913 as an enlarged successor to the W class. It was fitted with a superheater from the start and, from the second batch, also with a combustion chamber. This made it possible to increase the train weight by almost 30 percent. 135 W-3 were built in 1913 and 1917 to 1920. Ten made it to the Spokane, Portland & Seattle where they became class O-3. In 1922 another 25 W-5 followed, which were almost identical but had a higher boiler pressure.
Technical data
General
| Property | W-3 | W-5 |
|---|---|---|
| Built | 1913, 1917-1920 | 1922 |
| Manufacturers | ALCO | |
| Wheel arrangement | 2-8-2 (Mikado) | |
| Gauge | 1,435 mm (Standard gauge) | |
Dimensions and weights
| Property | W-3 | W-5 |
|---|---|---|
| Wheelbase | 10.74 m | 11.05 m |
| Total wheelbase | 20.78 m | 22.25 m |
| Service mass | 145.2 t | 155.5 t |
| Adhesion mass | 109.1 t | 113.9 t |
| Total mass | 233.1 t | 247.3 t |
| Rigid wheelbase | 5.03 m | |
| Axle load | 29.2 t | 28 t |
| Water capacity | 37,854 l | |
| Fuel capacity | 14.5 t (coal) | |
Boiler
| Property | W-3 | W-5 |
|---|---|---|
| Grate area | 6.54 m² | 6.531 m² |
| Firebox surface | 30.194 m² | 28.521 m² |
| Tube heating surface | 303.422 m² | 305.187 m² |
| Evaporative heating surface | 333.615 m² | 333.708 m² |
| Superheater surface | 78.596 m² | 78.503 m² |
| Total heating surface | 412.2 m² | |
Power plant
| Property | W-3 | W-5 |
|---|---|---|
| Driver diameter | 1,600 mm | |
| Boiler pressure | 12.4 bar | 13.8 bar |
| Expansion type | simple expansion | |
| Cylinders | two, 711 x 762 mm | |
Power
| Property | W-3 | W-5 |
|---|---|---|
| Power source | steam | |
| Estimated power | 2,013 kW (2,737 PS) | 2,237 kW (3,041 PS) |
| Starting effort | 254.1 kN | 282.3 kN |
Calculated values
| Property | W-3 | W-5 |
|---|---|---|
| Factor of adhesion | 1 : 4.21 | 1 : 3.96 |
| Optimal speed | 48 km/h | |
| Power-to-weight ratio | 13.9 kW/t | 14.4 kW/t |
| Heating Surface Equivalent | 641.8 m² | 633.3 m² |
| Cylinder volume/HSE | 1 : 943.35 | 1 : 955.95 |
| Adhesive weight/Total | 1 : 1.33 | 1 : 1.36 |
| Tractive force/Heating surface | 1 : 12.87 | 1 : 14.30 |
| Grate area/Heating surface | 1 : 63.03 | 1 : 63.12 |
| Firebox/Tube surface | 1 : 10.05 | 1 : 10.70 |
| Total/Superheater | 1 : 4.24 | 1 : 4.25 |
