Union Pacific classes MT-1 and MT-2
The only 4-8-2 Mountain locomotives ever operated by the Union Pacific were the classes MT-1 and MT-2, which were nearly identical apart from their firing method. The first 40 MT-1 were built in 1922 by ALCO, followed by 15 more in 1923 which weighed 3,000 pounds less. These were all coal-fired and had a tender that held 12,000 gallons of water and 20 tons of coal. Five MT-2 delivered in 1924 were oil-fired and had tenders with 15,000 gallons of water and 5,480 gallons of oil.
These locomotives were used to haul important passenger trains over long distances. They ran distances of 500 to 700 miles without major stops. Later, many were fitted with a partial casing. Only 7002 was totally streamlined and got roller bearings on all axles and the rods. It was used to haul the all-Pullman “Forty-Niner” when it was found out that early diesels could not keep up the schedule between Chicago and San Francisco. By 1956, all MT-1 and MT-2 locomotives had been scrapped.
Technical data
General
| Property | MT-1 | MT-2 |
|---|---|---|
| Built | 1922-1923 | 1924 |
| Manufacturers | ALCO | |
| Wheel arrangement | 4-8-2 (Mountain) | |
| Gauge | 1,435 mm (Standard gauge) | |
Dimensions and weights
| Property | MT-1 | MT-2 |
|---|---|---|
| Wheelbase | 12.57 m | |
| Total wheelbase | 24.37 m | |
| Service mass | 157.9 t | 158.9 t |
| Adhesion mass | 105.2 t | 105.7 t |
| Total mass | 265.6 t | 287.9 t |
| Rigid wheelbase | 5.97 m | |
| Axle load | 26.3 t | 26.4 t |
| Water capacity | 45,425 l | 56,781 l |
| Fuel capacity | 18.1 t (coal) | 20,744 l (oil) |
Boiler
| Property | MT-1 | MT-2 |
|---|---|---|
| Grate area | 7.804 m² | |
| Firebox surface | 35.489 m² | |
| Tube heating surface | 426.611 m² | |
| Evaporative heating surface | 462.1 m² | |
| Superheater surface | 115.386 m² | |
| Total heating surface | 577.5 m² | |
Power plant
| Property | MT-1 | MT-2 |
|---|---|---|
| Driver diameter | 1,854 mm | |
| Boiler pressure | 13.8 bar | |
| Expansion type | simple expansion | |
| Cylinders | two, 737 x 711 mm | |
Power
| Property | MT-1 | MT-2 |
|---|---|---|
| Power source | steam | |
| Estimated power | 2,498 kW (3,396 PS) | 2,610 kW (3,549 PS) |
| Starting effort | 243.9 kN | |
Calculated values
| Property | MT-1 | MT-2 |
|---|---|---|
| Factor of adhesion | 1 : 4.23 | 1 : 4.25 |
| Optimal speed | 63 km/h | 66 km/h |
| Power-to-weight ratio | 15.8 kW/t | 16.4 kW/t |
| Heating Surface Equivalent | 870.3 m² | |
| Cylinder volume/HSE | 1 : 696.46 | |
| Adhesive weight/Total | 1 : 1.50 | |
| Tractive force/Heating surface | 1 : 8.82 | |
| Grate area/Heating surface | 1 : 74.00 | |
| Firebox/Tube surface | 1 : 12.02 | |
| Total/Superheater | 1 : 4.00 | |