Verde Tunnel and Smelter Railroad No. 500 and 501
Southern Pacific class MM-3
United States 1920 2 produced
In 1920, ALCO-Schenectady built two 2-6-6-2 Mallets for the Verde Tunnel & Smelter Railroad. It operated a short network to carry copper ore to the smelters in Jerome and Clarkdale, Arizona. The locomotives carried the numbers 500 and 501 and were sold to the Southern Pacific in 1943 for their wartime needs.
The new owner gave them the numbers 3930 and 3931 and created the class name MM-3, where the letters stood for “Mallet Mogul”. There they were used on branches and as helpers, almost exclusively on the Los Angeles division. Since they were not rebuilt to simple expansion, they were among the last compounds in the SP. 3931 was retired in 1951 and 3930 three years later.
Technical data
General
- Built
- 1920
- Manufacturers
- ALCO
- Wheel arrangement
- 2-6-6-2 (Mallet Mogul)
- Gauge
- 1,435 mm (Standard gauge)
Dimensions and weights
- Wheelbase
- 6.30 m
- Service mass
- 202.8 t
- Adhesion mass
- 170.6 t
- Rigid wheelbase
- 14.88 m
- Axle load
- 28.4 t
Boiler
- Grate area
- 6.689 m²
- Firebox surface
- 33.445 m²
- Tube heating surface
- 422.431 m²
- Evaporative heating surface
- 455.876 m²
- Superheater surface
- 105.817 m²
- Total heating surface
- 561.7 m²
Power plant
- Driver diameter
- 1,448 mm
- Boiler pressure
- 15.2 bar
- Expansion type
- compound
- Cylinders
- four, HP: 597 x 813 mm and LP: 940 x 813 mm
Power
- Power source
- steam
- Estimated power
- 2,685 kW (3,651 PS)
- Starting effort
- 367.5 kN
- Starting effort simple
- 441.0 kN
Calculated values
- Factor of adhesion
- 1 : 4.55
- Optimal speed
- 45 km/h
- Power-to-weight ratio
- 13.2 kW/t
- Heating Surface Equivalent
- 834.7 m²
- Cylinder volume/HSE
- 1 : 1,220.41
- Adhesive weight/Total
- 1 : 1.19
- Tractive force/Heating surface
- 1 : 13.67
- Grate area/Heating surface
- 1 : 83.97
- Firebox/Tube surface
- 1 : 12.63
- Total/Superheater
- 1 : 4.31
