Pennsylvania Railroad class D6

Class D6 (formerly Class K, pre-1895) on the Pennsylvania Railroad was a class of 4-4-0 steam locomotive.[3] Nineteen were built by the PRR's Altoona Works (now owned by Norfolk Southern) between 1881 and 1883. They were equipped with 78-inch (1,981 mm) drivers.[1] Seven were later converted to 72-inch (1,829 mm) drivers and classified D6a.[1]

Pennsylvania Railroad D6
PRR D6 #317 in its builders' portrait
Type and origin
Power typeSteam
DesignerTheodore N. Ely
BuilderPRR Altoona Works[1]
Build date1881–1883[1]
Total produced19[1]
Specifications
Configuration:
​
 • Whyte4-4-0
 • UIC2′B
Gauge4 ft 8+1⁄2 in (1,435 mm)
Leading dia.33 in (838 mm)[2]
Driver dia.78 in (1,981 mm)[2]
Wheelbase22 ft 8+1⁄2 in (6.92 m)[2]
Length58 ft 0.3 in (17.69 m)[2]
Height15 ft 0 in (4.57 m)[2]
Axle load32,900 lb (14.9 tonnes)[2]
Adhesive weight58,800 lb (26.7 tonnes)[2]
Loco weight96,700 lb (43.9 tonnes)[2]
Total weight153,000 lb (69.4 tonnes)[2]
Fuel typeSoft coal
Fuel capacity12,000 lb (5.4 tonnes)[2]
Water cap.2,400 US gal (9,100 L; 2,000 imp gal)[2]
Firebox:
 • Firegrate area		34.76 sq ft (3.23 m2)[2]
Boiler pressure140 lbf/in2 (970 kPa)[2]
Heating surface1,240 sq ft (115.20 m2)[2]
 • Tubes1,085 sq ft (100.80 m2)[2]
 • Firebox155 sq ft (14.40 m2)[2]
Cylinders2
Cylinder size18 in × 24 in (460 mm × 610 mm)[3]
Valve gearStephenson
Performance figures
Tractive effort11,170 lbf (49.69 kN) (D6)
12,800 lbf (56.94 kN) (D6a)
Factor of adh.5.3 (D6) 4.6 (D6a)

The D6 was one of the first American 4-4-0s to place the firebox above, rather than between, the locomotive's frames.[4] This added about 8 inches to the possible width of the firebox, enabling a larger, easier to fire and more powerful locomotive; the maximum fire grate area increased to about 35 sq ft (3.25 m2) from the previous maximum of about 18 sq ft (1.67 m2).[5]

The innovation was not wholly new, having been first seen on the Philadelphia and Reading Railroad's 1859 Vera Cruz, designed by James Milholland of that road and built in their own shops; the Reading used this design until the invention of the Wootten firebox in 1877.[6] It was subsequently adopted by the Baldwin Locomotive Works in 1881 for six locomotives constructed for the Central of New Jersey; these were followed by the Pennsylvania Railroad locomotives, which garnered more attention for this design feature, in addition to having larger drivers than most previous 4-4-0s.

References
  1. "PRR Steam Roster". Northeast Rails. Retrieved December 31, 2007.
  2. Pennsylvania Railroad. "D6 Diagram". PRR.Railfan.net. Retrieved December 31, 2007.
  3. Staufer, Alvin F. & Pennypacker, Bert (1962). Pennsy Power: Steam and Electric Locomotives of the Pennsylvania Railroad, 1900–1957. Staufer. LCCN 62020878.
  4. Gunsaulus, Frank W. (ed.) (1906). Modern Engineering Practice. American School of Correspondence. {{cite book}}: |author= has generic name (help)
  5. "Mechanical Stokers for Locomotives". Cassier's Magazine. Vol. XXXII, no. 1. New York: Cassier Magazine. May 1907. p. 75.
  6. Report of the Proceedings of the Nineteenth Annual Convention of the American Railway Master Mechanics' Association in Convention at Tremont Temple, Boston, Mass., June 15th, 16th and 18th, 1886. Cincinnati, Ohio: Aldine. 1886.
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