Pennsylvania Railroad class P5

The Pennsylvania Railroad's class P5 comprised 92 mixed-traffic electric locomotives constructed 1931–1935 by the PRR, Westinghouse and General Electric.[1] Although the original intention was that they work many passenger trains, the success of the GG1 locomotives meant that the P5 class were mostly used on freight. A single survivor, prototype #4700, is at the Museum of Transportation in St Louis, Missouri.

PRR P5/P5a
PRR P5a #4761
Type and origin Power type Electric Builder PRR Altoona Works (13) Baldwin-Westinghouse (54) General Electric (25)[1] Build date 1931–1935 Total produced 92
Specifications Configuration: ​  • Whyte 4-6-4  • AAR 2-C-2  • UIC 2′Co2′ Gauge 4 ft 8 ^1⁄2 in (1,435 mm) standard gauge Leading dia. 36 in (914 mm)[2][3][4] Driver dia. 72 in (1,829 mm)[2][3][4] Trailing dia. 36 in (914 mm)[2][3][4] Wheelbase 49 ft 10 in (15.19 m) (total); 20 ft (6.10 m) (rigid)[2][3][4] Length 62 ft (19 m)[2][3][4] Width 10 ft 6 in (3.20 m) (P5, P5a, P5b);[2][3] 10 ft 8.25 in (3.26 m) (P5a (modified))[4] Height 15 ft (4.57 m) over locked-down pantographs[2][3][4] Axle load 74,000 lb (34,000 kg; 34 t) (P5, P5a);[2] 77,800 lb (35,300 kg; 35.3 t) (P5b);[3] 77,000 lb (35,000 kg; 35 t) (P5a (modified))[4] Adhesive weight 220,000 lb (100,000 kg; 100 t) (P5, P5a);[2] 444,700 lb (201,700 kg; 201.7 t) (P5b, all wheels driven);[3] 229,000 lb (104,000 kg; 104 t) (P5a (modified))[4] Loco weight 392,000 lb (178,000 kg; 178 t) (P5, P5a);[2] 444,700 lb (201,700 kg; 201.7 t) (P5b);[3] 394,000 lb (179,000 kg; 179 t) (P5a (modified))[4] Electric system/s 11 kV AC @ 25 Hz Catenary Current pickup(s) Pantograph Traction motors 6× 625 hp (466 kW) AC motors;[2][4] plus 4× 375 hp (280 kW) motors on the trucks on P5b[3] Transmission AC current fed via transformer tap changers to paired motors geared (25:97) to quill drives on each driving axle;[2][4] plus single motors geared to driving axles on end trucks on P5b (gear ratio: 17:50)[3]
Career Operators Pennsylvania Railroad Numbers 4700–4791 Preserved 4700 Disposition One P5 prototype preserved. Remained scrapped.

They had an AAR wheel arrangement of 2-C-2, or 2′Co2′ in the UIC classification system — three pairs of driven wheels rigidly mounted to the locomotive, with a two-axle unpowered truck at each end. This is an equivalent to a 4-6-4 in the Whyte notation.[2][3][4] The PRR did not have any 4-6-4 steam locomotives, so the P5s were the only 4-6-4 type locomotives owned by the PRR.

The first P5s were built with box cabs. A grade crossing accident in which the crew were killed led to the substitution of a central cab to give better crash protection, a streamlined steeple type, in later production, a design which was also applied to the GG1.

Table of P5 locomotive production

Year	Builder	Bodystyle	Road numbers	Notes
1931	Altoona	Boxcab	7898-7899	Class P5, Renumbered 4700 & 4791 respectively in 1933
1932	Westinghouse		4701–4732	4702 rebuilt to P5b in 1937
	General Electric		4755–4774	4770 rebuilt as Modified in 1945
1933	Westinghouse		4733-4742
1934	Altoona	Modified	4780
1935	Westinghouse		4743–4754
	General Electric		4775-4779
	Altoona		4781-4790

When the GG1s were put in passenger service, the P5s were regeared and used in freight service for many years. The last of the class was withdrawn from service in April 1965.[5]

P5 prototypes

Two prototype locomotives were outshopped from the PRR's Altoona Works in 1931.[1] They were essentially the PRR's 2-B-2 O1 design lengthened by adding another pair of driving wheels; while the O1 was an "electric Atlantic" equivalent to the E6s steam locomotive, the P5 was an "electric Pacific" designed to match or better the performance of the PRR's ubiquitous K4s Pacifics.

These prototypes had electrical equipment from both Westinghouse and General Electric; the design was by both companies and the PRR's electrical department, and the equipment from either manufacturer was identical.

P5a production locomotives

Orders were placed for 90 production locomotives classified P5a due to minor changes from the prototypes (notably, larger traction motor blowers).[1] Production was split between General Electric and Westinghouse; the GE examples were assembled at GE's Erie, Pennsylvania facility, still a locomotive assembly plant today, while final assembly for the Westinghouse order was subcontracted to the Baldwin Locomotive Works.

P5a (modified) steeplecabs

A fatal grade crossing accident on the New York Division confirmed traincrews' concerns about safety when the crew were killed after colliding with a truckload of apples.[1] A redesign was undertaken, giving the locomotives a central cab, raised higher, with narrower-topped, streamlined "noses" to the locomotive to enable the crew to see forward. The final 28 locomotives were built to this design, which was not given a separate class designation since it was mechanically and electrically identical; they were called class P5a (modified), and colloquially Modifieds.[1]

P5a (modified) #4780

Documentation published in 2010 disproved the decades long belief that the modified P5's new shell design came first and was then applied to the GG1, R1, and eventually the DD2. Instead, it was revealed that the GG1 project, under the direction of industrial designer Donald R. Dohner, was the first to receive the center cab design, and that soon afterward it was applied to the R1 and P5.[6]

The Modified units (along with the R1 and prototype GG1) were built with riveted carbodies. However, unit #4770, rebuilt to a Modified appearance in January 1945 after being wrecked in February 1944,[7][8] differed from previous Modifieds in having an all-welded carbody, the type of construction famously utilized in the production run of the GG1.[9]

P5b experiment

In October 1937 P5a #4702 was rebuilt with motors in its trucks to become the only locomotive in subclass P5b. Each truck axle was given a 375-horsepower (280 kW) motor,[3] adding 1,500 hp (1,100 kW) to give a total power output of 5,250 hp (3,910 kW) and a wheel arrangement of B-C-B or Bo′CoBo′. The main drivers had used double traction motors on each axle, but the trucks were a single motor per axle. This modification also meant that locomotive's entire weight was carried on driven wheels. Despite these advantages the experiment was not repeated, however #4702 continued in its modified form.

Visually, class P5b could be distinguished from a boxcab P5a by having a lower row of ventilation grilles on the sides of the superstructure, and by having outside brake cylinders on the trucks.[1]

See also

• PRR locomotive classification

References

1. Staufer, Alvin F.; Pennypacker, Bert (1962). Pennsy Power: Steam and Electric Locomotives of the Pennsylvania Railroad, 1900-1957. Research by Martin Flattley. Carollton, Ohio: Alvin F. Staufer. p. 298. ISBN 978-0-9445-1304-0.
2. Pennsylvania Railroad. "P5 & P5a". PRR Locomotive Diagrams. Retrieved 2008-08-29.
3. Pennsylvania Railroad. "P5b". PRR Locomotive Diagrams. Retrieved 2008-08-29.
4. Pennsylvania Railroad. "P5a (modified)". PRR Locomotive Diagrams. Retrieved 2008-08-29.
5. Pennsylvania Railroad Technical and Historical Society (August 2004). "PRR Chronology 1965" (PDF). Retrieved 2008-08-30.
6. Wayt, Hampton C. (Fall 2010). "Update on the GG1's genesis". Classic Trains (Kalmbach) 11 (3): 86–87.
7. "2 Killed as 90 Car Freight Speeds Past Flagman and Plows Into Standing train". Philadelphia Inquirer. February 14, 1944. p. 1.
8. Interstate Commerce Commission. Investigation no. 2774 The Pennsylvania Railroad Company report in re accident near Roxton, Pa., on February 13, 1944. OCLC 947002343.
9. Volkmer, William D. (1991). Pennsy Electric Years. Edison, New Jersey: Morning Sun Books. pp. 26–27. ISBN 1-878887-01-7.