Pennsylvania Railroad class T1

Pennsylvania Railroad T1
T1 5549 on display.
Type and origin Power type Steam Designer Ralph P. Johnson[1] Raymond Loewy[2] Builder Altoona Works (5500–5524) Baldwin Locomotive Works (5525–5549, 6110–6111) Pennsylvania Railroad T1 Steam Locomotive Trust (5550)[3] Serial number Altoona 4560–4584 BLW 72764–72788 (5525–5519) Build date 1942 (6110–6111) 1945–46 (5500–5549) 2014–present (5550)[3] Total produced 52
Specifications Configuration: ​  • Whyte 4-4-4-4  • UIC 2′BB2′ Gauge 4 ft 8+1⁄2 in (1,435 mm) Leading dia. 36 in (914 mm) Driver dia. 80 in (2,032 mm) Trailing dia. 42 in (1,067 mm) Wheelbase 107 ft 0 in (32.61 m) Length 122 ft 9+3⁄4 in (37.43 m) Width 11 ft 1 in (3.38 m) Height 6111: 15 ft 6 in (4.72 m)[4] Axle load 71,680 lb (32.51 t) Adhesive weight 279,910 lb (127.0 t) Loco weight 502,200 lb (227.8 t) Tender weight Empty: 197,400 lb (89.54 t); Loaded: 442,500 lb (200.7 t) Total weight 944,700 lb (428.5 t) Tender type 180 P 76 (Prototype), 180 P 84 (Production) Fuel type Coal Fuel capacity 85,200 lb (38.65 t) Water cap. 19,200 US gal (73,000 L; 16,000 imp gal) Firebox: ​  • Grate area 92 sq ft (8.5 m2) Boiler 100 in (2,540 mm) Boiler pressure 300 lbf/in2 (2.07 MPa) Heating surface: ​  • Firebox 490 sq ft (45.5 m2)  • Tubes and flues 4,209 sq ft (391.0 m2)  • Total surface 5,639 sq ft (523.9 m2) Superheater: ​  • Type Type A  • Heating area 1,430 sq ft (132.9 m2) Cylinders Four Cylinder size 19.75 in × 26 in (502 mm × 660 mm), 18.75 in × 26 in (476 mm × 660 mm) (some) Valve gear Franklin poppet Valve type Poppet valves
Performance figures Maximum speed 120 mph (193 km/h) Power output 6,500 ihp (4,800 kW) Tractive effort 64,653 lbf (287.6 kN) (85%),[5] 58,271 lbf (259.2 kN) (85%) (some) Factor of adh. 4.33
Career Operators Pennsylvania Railroad Class T1 Number in class 52 original, plus 1 under construction[3] Numbers 6110, 6111, 5500-5549, 5550 Locale Western Pennsylvania, Ohio, Indiana, Illinois First run 1942 Retired 1953 Withdrawn 1952–1953[6] Scrapped 1953–1956[6][3] Disposition All 52 original scrapped, 1 new build (PRR 5550) under construction

The Pennsylvania Railroad (PRR) class T1 duplex-drive 4-4-4-4 steam locomotives, introduced in 1942 with two prototypes and later in 1945-1946 with 50 production examples, were the last steam locomotives built for the PRR and arguably its most controversial. They were ambitious, technologically sophisticated, powerful, fast and distinctively streamlined by Raymond Loewy. However, they were also prone to wheelslip both when starting and at speed, in addition to being complicated to maintain and expensive to run. ^{[citation needed]} The PRR decided in 1948 to place diesel locomotives on all express passenger trains, leaving unanswered questions as to whether the T1's flaws were solvable, especially taking into account that the two prototypes did not have the problems inherent to the production units.

An article appearing in a 2008 issue of the Pennsylvania Railroad Technical and Historical Society Magazine showed that inadequate training for engineers transitioning to the T1 may have led to excessive throttle applications, resulting in driver slippage.^[7] Another root cause of wheelslip was faulty "spring equalization": The stiffnesses of the springs supporting the locomotive over the axles were not adjusted to properly equalize the wheel-to-track forces.^[8] The drivers were equalized together but not equalized with the engine truck. In the production fleet the PRR equalized the engine truck with the front engine and the trailing truck with the rear engine, which helped to solve the wheelslip problem.^[9]