The Western Pacific used its "Challengers" for freight service across the desert between Elko, NV and Salt Lake City, UT until they were retired in 1952.
There are no surviving Western Pacific "Challengers".
|Class||Qty.||Road Number||Year Built||Builder||Notes|
|M-100||7||401-407||1938||ALCO||Numbers 410-407 scrapped in 1952|
Little-remarked group of Challengers for the WP that ran across the desert from Elko, Nevada to Salt Lake City, Utah. The data convey in many ways just how big a Challenger truly was. The Western Pacific's diagram book contains a few more: boiler water capacity with 1 gauge of water was 7,750 US gallons (29,334 litres). 2 gauges full equated to 8,310 gallons (31,453 litres), and 3 gauges meant 8,840 US gallons (33,459 litres). Locobase can't resist comparing those oceans of water to a swimming pool and calculates that a 3-gauge boiler would fill a oval pool 40 feet long, 8 feet wide, and 9 feet deep (12.2 x 2.44 x 2.74 m).
Four thermic syphons contributed 151 sq ft (14.03 sq m) to the direct heating surface. Each cylinder was fed by its own 12" (305 mm) piston valve. The four wheels of the leading truck turned ASF roller bearings, while the six-wheel trailing truck used SKF rollers.
Very similar to the Clinchfield and D&H locomotives running on this wheel arrangement. See Locobase 338 for a description of the revised bearing design that permitted smooth riding at much higher speeds than usually reached by articulated locomotives. Even before that update, S Kip Farrington, Jr's note in a 29 May 1940 engine log said the 402 hauled 57 cars aggregating 2,780 tons (2,527 tonnes) "extremely well taking the Wendover hill, 68 miles (109 km) of 1%, with ease."
Each of these engines cost $181,762 on delivery in 1938. Fourteen years later, supplanted by diesels, their scrap value amounted to $13,762 apiece in May and June 1952.
|Principal Dimensions by Steve Llanso of Sweat House Media|
|Railroad||Western Pacific (WP)|
|Number in Class||7|
|Locomotive Length and Weight|
|Driver Wheelbase (ft / m)||12.17 / 3.71|
|Engine Wheelbase (ft / m)||59.92 / 18.26|
|Ratio of driving wheelbase to overall engine wheebase||0.20|
|Overall Wheelbase (engine & tender) (ft / m)||106.54 / 32.47|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||66,500 / 30,164|
|Weight on Drivers (lbs / kg)||399,000 / 180,984|
|Engine Weight (lbs / kg)||590,000 / 267,620|
|Tender Loaded Weight (lbs / kg)||401,500 / 182,118|
|Total Engine and Tender Weight (lbs / kg)||991,500 / 449,738|
|Tender Water Capacity (gals / ML)||22,000 / 83.33|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||25 / 22.70|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||111 / 55.50|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||70 / 1778|
|Boiler Pressure (psi / kPa)||265 / 18.30|
|High Pressure Cylinders (dia x stroke) (in / mm)||22" x 32" / 559x813 (4)|
|Tractive Effort (lbs / kg)||99,676 / 45212.33|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.00|
|Firebox Area (sq ft / m2)||692 / 64.29|
|Grate Area (sq ft / m2)||108.20 / 10.05|
|Evaporative Heating Surface (sq ft / m2)||5666 / 526.38|
|Superheating Surface (sq ft / m2)||1724 / 160.16|
|Combined Heating Surface (sq ft / m2)||7390 / 686.54|
|Evaporative Heating Surface/Cylinder Volume||201.22|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||28,673|
|Same as above plus superheater percentage||35,268|
|Same as above but substitute firebox area for grate area||225,557|