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 ID16,145 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 Wheelbase (ft)19.3319.3319.33
Engine Wheelbase (ft)27.6727.6727.67
Ratio of driving wheelbase to overall engine wheebase 0.70 0.70 0.70
Overall Wheelbase (engine & tender) (ft)58.4558.4558.45
Axle Loading (Maximum Weight per Axle) (lbs)51,270
Weight on Drivers (lbs)200,000221,360200,000
Engine Weight (lbs)220,000248,590220,000
Tender Light Weight (lbs)150,000150,000150,000
Total Engine and Tender Weight (lbs)370,000398,590370,000
Tender Water Capacity (gals)750075007500
Tender Fuel Capacity (oil/coal) (gals/tons)141414
Minimum weight of rail (calculated) (lb/yd)677467
Geometry Relating to Tractive Effort
Driver Diameter (in)5151.5051
Boiler Pressure (psi)190190190
High Pressure Cylinders (dia x stroke) (in)23.5" x 28"23" x 28"23" x 28"
Tractive Effort (lbs)48,96646,44946,905
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.08 4.77 4.26
Heating Ability
Firebox Area (sq ft)192.40212.40211.50
Grate Area (sq ft)52.2068.9052.20
Evaporative Heating Surface (sq ft)419434063599
Superheating Surface (sq ft)611
Combined Heating Surface (sq ft)419440173599
Evaporative Heating Surface/Cylinder Volume298.37252.96267.30
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation991813,0919918
Same as above plus superheater percentage991815,0559918
Same as above but substitute firebox area for grate area36,55646,40940,185
Power L1592412,0725585
Power MT326.50601.15307.82


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