These were, says Drury (1993), the best "(or least unsuccessful)" of the small roster of articulateds on the Santa Fe. Although they had the "preheater" that was in brief vogue among US articulated builders, they avoided the jointed boilers of the later 2-6-6-2s. Still, deploying a boiler, 10 ft 9 in (3.28 m) long "intermediate combustion chamber" containing both a Jacobs superheater and Santa Fe reheater, and a front boiler housing the big bundle of feedwater heater tubes made for a long locomotive.
Baldwin and the Santa Fe calculated evaporative heating surface area using the firebox, tube heating surface area, and the feed water heater's 417 tubes of 2 1/4" diameter and 6 ft 8 (2.03 m) in length, which contributed 1,617 sq ft (150.22 sq m). The 1,201 sq ft (111.58 sq m) of the reheater, which added heat to the exhaust coming from the HP cylinders before it entered the LP cylinders, didn't figure in the overall calculation.
HP piston valves measured 13" (330 mm) in diameter and were set up for inside . LP valves were 2" (50.8 mm) bigger and were set up for outside admission.
The pair also deployed the stayless Jacobs-Shupert firebox; see Locobase 463 for a description of this unusual firebox design. A Booth oil burner was mounted in the front of the firebox.
In 1924, the engine units were removed and placed under separate boilers, creating two Mikados each.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Railroad||Santa Fe (ATSF)|
|Number in Class||2|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||16.50 / 5.03|
|Engine Wheelbase (ft / m)||59.83 / 18.24|
|Ratio of driving wheelbase to overall engine wheebase||0.28|
|Overall Wheelbase (engine & tender) (ft / m)||98.44 / 30|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||54,900 / 24,902|
|Weight on Drivers (lbs / kg)||412,384 / 187,054|
|Engine Weight (lbs / kg)||462,448 / 209,763|
|Tender Loaded Weight (lbs / kg)||233,520 / 105,923|
|Total Engine and Tender Weight (lbs / kg)||695,968 / 315,686|
|Tender Water Capacity (gals / ML)||12,000 / 45.45|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||4000 / 15.20|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||86 / 43|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||63 / 1600|
|Boiler Pressure (psi / kPa)||220 / 15.20|
|High Pressure Cylinders (dia x stroke) (in / mm)||26" x 34" / 660x864|
|Low Pressure Cylinders (dia x stroke) (in / mm)||38" x 34" / 965x864|
|Tractive Effort (lbs / kg)||92,937 / 42155.56|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.44|
|Firebox Area (sq ft / m2)||236 / 21.92|
|Grate Area (sq ft / m2)||68.50 / 6.36|
|Evaporative Heating Surface (sq ft / m2)||6621 / 615.11|
|Superheating Surface (sq ft / m2)||544 / 50.54|
|Combined Heating Surface (sq ft / m2)||7165 / 665.65|
|Evaporative Heating Surface/Cylinder Volume||316.90|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||15,070|
|Same as above plus superheater percentage||16,276|
|Same as above but substitute firebox area for grate area||56,074|