Pennsylvania 2-8-8-0 "Consolidation Mallet" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class HC1s (Locobase 309)

Data from "Pennsylvania's New Simple Mallet Type Locomotive," Railway and Locomotive Engineering, July 1919, pp. 193-194.

One-of-a-kind articulated for the Pennsy, who preferred to be the non-Standard Railroad of the World when it came to that kind of engine. Like other Pennsylvania engines, too, it burned its fuel in a Belpaire firebox. (See Locobase 32 for a comment on the unique design of Pennsy's Belpaire firebox.) and admitted steam through 12" (305 mm) piston valves on all cylinders.

The HC-1's boiler had 19-ft-long tubes and a combustion chamber measuring 12' 5 1/2" (3.797 m); the total length of the boiler came to 53' 9 1/2", possibly the longest ever mounted, of which 26 ft included the crown sheet. So long were the boiler and crown sheet that special pipes were led up out of the wrapper sheet at the front of the combustion chamber and continued back to gauge cocks to ensure that the crew would know the proper water level.

The oddness of the layout extended to the tube and flue combination. The superheater had three vertical headers and two superheater steam headers, each unit, says the R&LE, "...being connected to from two to five units, each unit leading and returning to or from one of the larger flues."

This engine is reported to have run well as a pusher in Allegheny Mountain service until it was retired in 1929.

Principal Dimensions by Steve Llanso of Sweat House Media
Locobase ID309
RailroadPennsylvania (PRR)
Number in Class1
Road Numbers3700
Number Built1
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)17.13 / 5.22
Engine Wheelbase (ft / m)54.70 / 16.67
Ratio of driving wheelbase to overall engine wheebase 0.31
Overall Wheelbase (engine & tender) (ft / m)97.31 / 29.66
Axle Loading (Maximum Weight per Axle) (lbs / kg)
Weight on Drivers (lbs / kg)540,000 / 244,940
Engine Weight (lbs / kg)575,000 / 260,816
Tender Loaded Weight (lbs / kg)219,000 / 99,337
Total Engine and Tender Weight (lbs / kg)794,000 / 360,153
Tender Water Capacity (gals / ML)12,900 / 48.86
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)13.90 / 12.60
Minimum weight of rail (calculated) (lb/yd / kg/m)113 / 56.50
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)62 / 1575
Boiler Pressure (psi / kPa)205 / 14.10
High Pressure Cylinders (dia x stroke) (in / mm)30.5" x 32" / 775x813 (4)
Tractive Effort (lbs / kg)167,325 / 75897.43
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.23
Heating Ability
Firebox Area (sq ft / m2)531 / 49.35
Grate Area (sq ft / m2)112 / 10.41
Evaporative Heating Surface (sq ft / m2)6656 / 618.59
Superheating Surface (sq ft / m2)3136 / 291.45
Combined Heating Surface (sq ft / m2)9792 / 910.04
Evaporative Heating Surface/Cylinder Volume122.99
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation22,960
Same as above plus superheater percentage30,307
Same as above but substitute firebox area for grate area143,689
Power L114,692
Power MT479.86