Philadelphia & Reading 2-6-6 Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class 623 (Locobase 16388)

Data from DeGolyer, Volume 17, p. 202; and "Locomotive 623", A century of Reading company motive power, 1832-1941 (Philadelphia: The Reading Company, 1941), p. 61. (Thanks to Chris Hohl for 8 February 2019 email pointing out the disparity between the Baldwin estimate for adhesion weight and the Reading's higher figure.) Works number was 12481 in February 1892.

Two recent innovations in US steam locomotive design caught fire in the late 1880s. One was John Wootten's enormous firebox designed especially to burn hard coal, which required a thin, softly drafted fire to burn anthracite. The other was Samuel Vauclain's four-cylinder compound layout, which appeared in every size locomotive for the next decade or so. Each set of one HP and one LP cylinders was served by a 9 3/4" (248 mm) piston valve.

Chris Hohl's comment on the discrepancy between Baldwin's estimated weight on the drivers of 72,000 lb (32,659 kg) and the Reading's figure of 91,000 lb shown above deserves an explanation. Baldwin's number fell 26.3% short and Locobase doesn't have enough information to figure out where the differences lay.

Bringing them together in this small commuter tank engine seems a forced combination. The 623 would remain the only 2-6-6T of any type to enter service on the Reading. A look at the design suggests that firing the big grate involved dropping the shovelfuls down a good distance. The Reading's Centenary guide notes the Illinois Central tried out the 623 on their commuter lines. Chicago's government put increasing pressure on the railroads to reduce smoke in the city and the relatively smokeless anthracite seemed worth a try.

In 1900, the Reading shops removed the tank and bunker and added a tender, turning the 623 into a 2-6-0. Renumbered 1452 in April 1900, the little locomotive served for almost two more decades. This represents one of the longest careers for a Vauclain compound.

Renumbered 528 in March 1917, the engine was finally scrapped in February 1920.

Principal Dimensions by Steve Llanso of Sweat House Media

Locobase ID16388
RailroadPhiladelphia & Reading
Number in Class1
Road Numbers623
Number Built1
BuilderBurnham, Williams & Co
Valve GearStephenson
Locomotive Length and Weight
Driver Wheelbase (ft / m)11 / 3.35
Engine Wheelbase (ft / m)35 / 10.67
Ratio of driving wheelbase to overall engine wheelbase 0.31
Overall Wheelbase (engine & tender) (ft / m)35 / 10.67
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)91,000 / 41,277
Engine Weight (lbs / kg)158,000 / 71,668
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)158,000
Tender Water Capacity (gals / ML)2000 / 7.58
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)
Minimum weight of rail (calculated) (lb/yd / kg/m)51 / 25.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)61.63 / 1565
Boiler Pressure (psi / kPa)175 / 12.10
High Pressure Cylinders (dia x stroke) (in / mm)12" x 24" / 305x610
Low Pressure Cylinders (dia x stroke) (in / mm)20" x 24" / 508x610
Tractive Effort (lbs / kg)12,267 / 5564.22
Factor of Adhesion (Weight on Drivers/Tractive Effort) 7.42
Heating Ability
Tubes (number - dia) (in / mm)321 - 1.5" / 38
Flues (number - dia) (in / mm)
Flue/Tube length (ft / m)9 / 2.74
Firebox Area (sq ft / m2)150 / 13.94
Grate Area (sq ft / m2)63.40 / 5.89
Evaporative Heating Surface (sq ft / m2)1285 / 119.38
Superheating Surface (sq ft / m2)
Combined Heating Surface (sq ft / m2)1285 / 119.38
Evaporative Heating Surface/Cylinder Volume408.80
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,095
Same as above plus superheater percentage11,095
Same as above but substitute firebox area for grate area26,250
Power L14192
Power MT304.67

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