Among the very first articulateds to run on the Union Pacific system were these Mallet Consoldiations.
As the question of quite how to superheat saturated steam was not quite settled, Baldwin experimented with a feedwater heater inserted in the forward part of the long boiler barrel. Saturated steam coming through the dry pipe fed the HP cylinders. Steam generation benefited from 43 sq ft (4 sq m) of fire brick tubes and 118 sq ft (10.95 sq m) in the combustion chamber, but it was still a big boiler to heat.
After 15" (381 mm) piston valves fed the first set of cylinders, the steam then traveled through a large flue nested in the feedwater heater bundle and thence through two more 15" piston valves to the LP cylinders. In this way, the steam was reheated with the hope of giving a little extra power to the lower-pressure steam .
Although the feedwater bundle's heating surface amounted to 1,222 sq ft, it cannot be properly described as a superheater. See the San Diego Railroad Museum's reproduction of a detailed description of the locomotive builder's proprietary design. [external link], accessed 12 March 2006. Baldwin's superheater design differed from those of Schmidt and even Pielock by residing entirely in the smokebox. Two curved bundles of tubes took the steam from a T-head and circulated through the elements, finally letting into the steam passages at the bottom. The design wasn't a big success, its superheating ability being inevitably limited.
Three went to the UP itself and three to the Oregon Short Line. They were relatively short lived, all being withdrawn in 1928.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Number in Class||3|
|Road Numbers||2000-2002 / 3600-02, 3800|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||15.50 / 4.72|
|Engine Wheelbase (ft / m)||50.50 / 15.39|
|Ratio of driving wheelbase to overall engine wheebase||0.31|
|Overall Wheelbase (engine & tender) (ft / m)||87.04 / 26.53|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||50,475 / 22,895|
|Weight on Drivers (lbs / kg)||394,150 / 178,784|
|Engine Weight (lbs / kg)||425,900 / 193,185|
|Tender Loaded Weight (lbs / kg)||157,200 / 71,305|
|Total Engine and Tender Weight (lbs / kg)||583,100 / 264,490|
|Tender Water Capacity (gals / ML)||9000 / 34.09|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||10 / 9.10|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||82 / 41|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||57 / 1448|
|Boiler Pressure (psi / kPa)||200 / 13.80|
|High Pressure Cylinders (dia x stroke) (in / mm)||26" x 30" / 660x762|
|Low Pressure Cylinders (dia x stroke) (in / mm)||40" x 30" / 1016x762|
|Tractive Effort (lbs / kg)||85,039 / 38573.09|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.63|
|Firebox Area (sq ft / m2)||392 / 36.42|
|Grate Area (sq ft / m2)||68.40 / 6.35|
|Evaporative Heating Surface (sq ft / m2)||6395 / 594.11|
|Superheating Surface (sq ft / m2)||655 / 60.85|
|Combined Heating Surface (sq ft / m2)||7050 / 654.96|
|Evaporative Heating Surface/Cylinder Volume||346.89|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||13,680|
|Same as above plus superheater percentage||14,911|
|Same as above but substitute firebox area for grate area||85,456|