Verde Tunnel & Smelter 2-6-6-2 Locomotives of 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 Raildata collection. 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.

Specifications 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)10.33
Engine Wheelbase (ft)48.83
Ratio of driving wheelbase to overall engine wheebase 0.21
Overall Wheelbase (engine & tender) (ft)
Axle Loading (Maximum Weight per Axle) (lbs)62,700
Weight on Drivers (lbs)376,000
Engine Weight (lbs)447,000
Tender Loaded Weight (lbs)
Total Engine and Tender Weight (lbs)447,000
Tender Water Capacity (gals)
Tender Fuel Capacity (oil/coal) (gals/tons)
Minimum weight of rail (calculated) (lb/yd)104
Geometry Relating to Tractive Effort
Driver Diameter (in)57
Boiler Pressure (psi)220
High Pressure Cylinders (dia x stroke) (in)23.5" x 32"
Low Pressure Cylinders (dia x stroke) (in)37" x 32"
Tractive Effort (lbs)82,623
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.55
Heating Ability
Firebox Area (sq ft)360
Grate Area (sq ft)72
Evaporative Heating Surface (sq ft)4907
Superheating Surface (sq ft)1139
Combined Heating Surface (sq ft)6046
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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