Pennsylvania Railroad class D7

Class D7 (formerly Class A (anthracite), pre-1895) on the Pennsylvania Railroad was a class of 4-4-0 steam locomotive.[4] Fifty-eight were built by the PRR's Altoona Works (now owned by Norfolk Southern) between 1882–1891 with 68 in (1.73 m) drivers, while sixty-one of class D7a were constructed with 62 in (1.57 m) drivers.[1]

Pennsylvania Railroad D7
PRR D7a #953 in its builders' portrait
Type and origin Power type Steam Builder PRR Altoona Works[1] Build date 1882–1891[1] Total produced 58 D7, 61 D7a[1]
Specifications Configuration: ​  • Whyte 4-4-0  • UIC 2′B Gauge 4 ft 8+1⁄2 in (1,435 mm) Leading dia. 30 in (762 mm) (D7)[2] 33 in (838 mm) (D7a)[3] Driver dia. 68 in (1,727 mm) (D7)[2] 62 in (1,575 mm) (D7a)[3] Wheelbase 22 ft 7+1⁄2 in (6.90 m)[2][3] Length 58 ft 0.6 in (17.69 m)[3] Height 14 ft 4 in (4.37 m)[3] Axle load 32,650 lb (14.8 tonnes)[3] Adhesive weight 56,700 lb (25.7 tonnes) (D7) [2] 58,700 lb (26.6 tonnes)[3] Loco weight 93,500 lb (42.4 tonnes) (D7)[2] 96,330 lb (43.7 tonnes) (D7a)[3] Total weight 160,880 lb (73.0 tonnes)[3] Fuel type Anthracite coal[1] Fuel capacity 12,000 lb (5.4 tonnes)[3] Water cap. 2,400 US gal (9,100 L; 2,000 imp gal)[3] Firebox:  • Firegrate area 34.75 sq ft (3.23 m2)[3] Boiler pressure 140 lbf/in2 (970 kPa)[3] Heating surface 1,289 sq ft (119.75 m2)[3]  • Tubes 1,134 sq ft (105.35 m2)[3]  • Firebox 155 sq ft (14.40 m2)[3] Cylinders 2[3] Cylinder size 17 in × 24 in (432 mm × 610 mm)[3] Valve gear Stephenson Valve type Slide valves
Performance figures Tractive effort 12,138 lbf (53.99 kN) (D7) 13,313 lbf (59.22 kN) (D6a) Factor of adh. 4.7 (D7) 4.4 (D7a)

The D7 was fundamentally an anthracite-burning version of the PRR D6, with a larger fire-grate in order to burn the slower-burning, harder coal.[5]