El Paso & Southwestern / San Antonio & Aransas Pass 2-10-0 "Decapod" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class D-1 (Locobase 16145)

Data from DeGolyer, Volume 25, p. 212. Baldwin works numbers were 21699 in February 1903, 22293 in June, and 22442 in July.

This trio of Decapods sent built for the EP & SW in February, June, & July 1903 were the only engines of that wheel arrangement ever operated in the entire SP Lines systems. They were rated to pull 1,435 trailing tons (1,302 metric tons) up a 1% grade. These were seriously drag-freight locomotives, although relatively small and possessing a tractive effort only as large as a small Mikado would exert a decade later.

After they entered service, the trio's boilers were either replaced or substantially altered; see Locobase 8680.

Locobase 8681 shows the results of superheating this class.

Class D-1 - superheated (Locobase 8681)

Data from the SP Menke All Time Steam Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

Delivered to the El Paso & Southwestern as the Espee System's only Decapods and later modified (Locobases 16145 and 8680, respectively), this trio was assigned by the Espee to the SA & AP in the 1920s. Locobase isn't sure when they were superheated. Whoever wrought the makeover, they effected a good trade-off between deleting small tubes and installing the larger superheater flues. They also traded in their slide valves for piston valves and increased the driver diameter by 1/2" (12.7 mm). For some reason, the engines gained 15 tons (!) in the upgrade.

The modified engines lasted only about a decade longer before heading for scrap on 23 November 1936 (361), and 2 and 4 June 1937 for the other two.

Class D-1-modified (Locobase 8680)

Data from the SP Menke All Time Steam Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

This trio of Decapods arrived on the EP&SW in 1903.At some point, the railroad dealt with what was apparently an unbalanced design by reducing cylinder volume slightly and cutting evaporative heating surface area by more than 600 sq ft.

Locobase 8681 shows the results of superheating this class.

Specifications by Steve Llanso of Sweat House Media
ClassD-1D-1 - superheatedD-1-modified
Locobase ID16145 8681 8680
RailroadEl Paso & Southwestern (SP)San Antonio & Aransas Pass (SP)El Paso & Southwestern (SP)
Number in Class333
Road Numbers26-28/360-362360-362360-362/897-899
Number Built3
BuilderBurnham, Williams & CoSA&APEP&SW
Valve GearStephensonStephensonStephenson
Locomotive Length and Weight
Driver Wheelbase19.33'19.33'19.33'
Engine Wheelbase27.67'27.67'27.67'
Ratio of driving wheelbase to overall engine wheebase 0.70 0.70 0.70
Overall Wheelbase (engine & tender)58.45'58.45'58.45'
Axle Loading (Maximum Weight per Axle)51270 lbs
Weight on Drivers200000 lbs221360 lbs200000 lbs
Engine Weight220000 lbs248590 lbs220000 lbs
Tender Light Weight150000 lbs150000 lbs150000 lbs
Total Engine and Tender Weight370000 lbs398590 lbs370000 lbs
Tender Water Capacity7500 gals7500 gals7500 gals
Tender Fuel Capacity (oil/coal)14 tons14 tons14 tons
Minimum weight of rail (calculated)67 lb/yard74 lb/yard67 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter51"51.50"51"
Boiler Pressure190 psi190 psi190 psi
Cylinders (dia x stroke)23.5" x 28"23" x 28"23" x 28"
Tractive Effort48966 lbs46449 lbs46905 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.08 4.77 4.26
Heating Ability
Firebox Area192.40 sq. ft212.40 sq. ft211.50 sq. ft
Grate Area52.20 sq. ft68.90 sq. ft52.20 sq. ft
Evaporative Heating Surface4194 sq. ft3406 sq. ft3599 sq. ft
Superheating Surface611 sq. ft
Combined Heating Surface4194 sq. ft4017 sq. ft3599 sq. ft
Evaporative Heating Surface/Cylinder Volume298.37252.96267.30
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation9918130919918
Same as above plus superheater percentage9918150559918
Same as above but substitute firebox area for grate area365564640940185
Power L15924120725585
Power MT326.50601.15307.82


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