Verde Tunnel & Smelter 2-6-6-2 "Mallet Mogul" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class MM-3 (Locobase 6766)

Data from SP 7 - 1951 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. works numbers were 61536-61537 in February 1920.

[] (visited 19 August 2005) notes that these Mallet Moguls originally operated on the Arizonan mining road headquartered in Jerome (which lies 100 miles north of Phoenix) and working the copper mines at Cleopatra Hill.

After 23 years, the Espee obtained the pair in 1943 to operate on Beaumont Hill near Los Angeles. Still running as compounds, they added eight years (3931) and eleven years (3930) to their service records before retirement.

The Espee diagram notes that the firebox was fitted with five thermic syphons. A Stan Kistler photograph hosted on [] (19 August 2005) shows counterbalancing that filled half the driver disk on the third axle.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID6766
RailroadVerde Tunnel & Smelter
Number in Class2
Road Numbers3930-3931
Number Built2
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)10.33 / 3.15
Engine Wheelbase (ft / m)48.83 / 14.88
Ratio of driving wheelbase to overall engine wheebase 0.21
Overall Wheelbase (engine & tender) (ft / m)
Axle Loading (Maximum Weight per Axle) (lbs / kg)62,700 / 28,440
Weight on Drivers (lbs / kg)376,000 / 170,551
Engine Weight (lbs / kg)447,000 / 202,756
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)447,000
Tender Water Capacity (gals / ML)
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)104 / 52
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)57 / 1448
Boiler Pressure (psi / kPa)220 / 15.20
High Pressure Cylinders (dia x stroke) (in / mm)23.5" x 32" / 597x813
Low Pressure Cylinders (dia x stroke) (in / mm)37" x 32" / 940x813
Tractive Effort (lbs / kg)82,623 / 37477.21
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.55
Heating Ability
Firebox Area (sq ft / m2)360 / 33.46
Grate Area (sq ft / m2)72 / 6.69
Evaporative Heating Surface (sq ft / m2)4907 / 456.04
Superheating Surface (sq ft / m2)1139 / 105.86
Combined Heating Surface (sq ft / m2)6046 / 561.90
Evaporative Heating Surface/Cylinder Volume305.46
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation15,840
Same as above plus superheater percentage18,850
Same as above but substitute firebox area for grate area94,248
Power L18900
Power MT313.10

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Wes Barris