Milwaukee Road class F3
Although the Milwaukee Road had already procured its first few Pacifics in 1893, the Atlantics had still to haul the fastest trains for the time being. However, when they got problems with trains of ten to 14 cars, the 70 class F3 Pacifics were ordered from ALCO in 1910. They were initially operated with saturated steam and were superheated from 1920 onwards. The diameter of the cylinders was increased from 23 to 23.5 inches, and for six of them even to 24 inches.
The locomotives were considered very powerful and well balanced. If necessary, they could reach up to 90 mph or 145 km/h. It wasn't until 1940 and 1941, when the Milwaukee Road was already using Hudsons, that three were rebuilt into the F3-as. The grate was widened and its area was significantly increased, but the direct heating surface of the firebox only grew slightly. Two of them were given streamlined fairing to haul the “Chippewa”.
Technical data
General
| Property | as built | superheated | rebuilt F3-as |
|---|---|---|---|
| Built | 1910 | 1920 | 1940-1941 |
| Manufacturers | ALCO | Milwaukee | |
| Wheel arrangement | 4-6-2 (Pacific) | ||
| Gauge | 1,435 mm (Standard gauge) | ||
Dimensions and weights
| Property | as built | superheated | rebuilt F3-as |
|---|---|---|---|
| Wheelbase | 10.85 m | ||
| Total wheelbase | 20.47 m | 20.54 m | |
| Service mass | 112.2 t | 119.7 t | 129 t |
| Adhesion mass | 71.3 t | 76.8 t | 86.8 t |
| Total mass | 174.8 t | 190.4 t | 199.7 t |
| Rigid wheelbase | 4.27 m | ||
| Axle load | 23.8 t | 25.6 t | 28.9 t |
| Water capacity | 26,498 l | 32,176 l | |
| Fuel capacity | 9.1 t (coal) | 10 t (coal) | 11.8 t (coal) |
Boiler
| Property | as built | superheated | rebuilt F3-as |
|---|---|---|---|
| Grate area | 4.534 m² | 5.556 m² | |
| Firebox surface | 24.712 m² | 25.548 m² | |
| Tube heating surface | 339.747 m² | 244.428 m² | 234.952 m² |
| Evaporative heating surface | 364.459 m² | 269.14 m² | 260.5 m² |
| Total heating surface | 364.5 m² | 326.7 m² | 318.1 m² |
| Superheater surface | 57.6 m² | ||
Power plant
| Property | as built | superheated | rebuilt F3-as |
|---|---|---|---|
| Driver diameter | 2,007 mm | ||
| Boiler pressure | 13.8 bar | ||
| Expansion type | simple expansion | ||
| Cylinders | two, 584 x 711 mm | two, 597 x 711 mm | |
Power
| Property | as built | superheated | rebuilt F3-as |
|---|---|---|---|
| Power source | steam | ||
| Estimated power | 1,417 kW (1,927 PS) | 1,641 kW (2,231 PS) | 1,790 kW (2,434 PS) |
| Starting effort | 141.8 kN | 148.0 kN | |
Calculated values
| Property | as built | superheated | rebuilt F3-as |
|---|---|---|---|
| Factor of adhesion | 1 : 4.93 | 1 : 5.09 | 1 : 5.75 |
| Optimal speed | 61 km/h | 68 km/h | 74 km/h |
| Power-to-weight ratio | 12.6 kW/t | 13.7 kW/t | 13.9 kW/t |
| Heating Surface Equivalent | 488.0 m² | 507.9 m² | 503.4 m² |
| Cylinder volume/HSE | 1 : 781.26 | 1 : 783.68 | 1 : 790.62 |
| Adhesive weight/Total | 1 : 1.57 | 1 : 1.56 | 1 : 1.49 |
| Tractive force/Heating surface | 1 : 8.12 | 1 : 9.46 | 1 : 9.72 |
| Grate area/Heating surface | 1 : 80.38 | 1 : 72.06 | 1 : 57.25 |
| Firebox/Tube surface | 1 : 13.75 | 1 : 9.89 | 1 : 9.20 |
| Total/Superheater | 1 : 4.67 | 1 : 4.52 |
