PRR P5 Overview
Type and origin
Power type: Electric
Builders: PRR Altoona Works (13)
Baldwin-Westinghouse (54)
General Electric (25)
Build date: 1931–1935
Total produced: 92

Configuration: 4-C-4
UIC class: 2'Co2'
Gauge: 4 ft 8 1⁄2 in (1,435 mm) standard gauge
Leading diameter: 36 in (914 mm)
Driver diameter: 72 in (1,829 mm)
Trailing diameter: 36 in (914 mm)
Wheelbase: 49 ft 10 in (15.19 m) (total); 20 ft (6.10 m) (rigid)
Length: 62 ft (19 m)
Width: 10 ft 6 in (3.20 m) (P5, P5a, P5b); 10 ft 8.25 in (3.26 m) (P5a (modified))
Height: 15 ft (4.57 m) over locked-down pantographs
Axle load: 74,000 lb (34,000 kg; 34 t) (P5, P5a);77,800 lb (35,300 kg; 35.3 t) (P5b); 77,000 lb (35,000 kg; 35 t) (P5a (modified))
Adhesive weight: 220,000 lb (100,000 kg; 100 t) (P5, P5a); 444,700 lb (201,700 kg; 201.7 t) (P5b, all wheels driven); 229,000 lb (104,000 kg; 104 t) (P5a (modified))
Loco weight: 392,000 lb (178,000 kg; 178 t) (P5, P5a); 444,700 lb (201,700 kg; 201.7 t) (P5b); 394,000 lb (179,000 kg; 179 t) (P5a (modified))
Electric system(s): 11 kV AC @ 25 Hz Catenary
Current collection: Pantograph
Traction motors: 6 × 625 hp (466 kW) AC motors; plus 4 × 375 hp (280 kW) motors on the trucks on P5b
Transmission: AC current fed via transformer tap changers to paired motors geared (25:97) to quill drives on each driving axle; plus single motors geared to driving axles on end trucks on P5b (gear ratio: 17:50)

Operators: Pennsylvania Railroad
Numbers: 4700–4791
Preserved: 4700
Disposition: Museum of Transportation in St Louis, Missouri

See also:

Electric Locomotives



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The original boxcab version of the P5a. No. 4761 was built in 1926 by the PRR Altoona Works and General Electric.

The original boxcab version of the P5a. No. 4761 was built in 1926 by the PRR Altoona Works and General Electric.
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Pennsylvania Railroad class P5a (modified) electric locomotive, circa 1946.

Pennsylvania Railroad class P5a (modified) electric locomotive, circa 1946.

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PRR P5 Electric Locomotive
The Pennsylvania Railroad's class P5 comprised 92 mixed-traffic electric locomotives constructed 1931–1935 by the PRR, Westinghouse and General Electric. 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 No. 4700, is at the Museum of Transportation in St Louis, Missouri.

They had a wheel arrangement of 4-6-4 in the Whyte notation, or 2'Co2' in the UIC classification system — three pairs of driven wheels rigidly mounted to the locomotive, with a two-axle un-powered truck at each end.

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

Table of P5 locomotive production

Year: 1931
Builder: Altoona
Bodystyle: Boxcab
Road numbers: 7898-7899
Notes: Class P5, Renumbered 4700 & 4791 respectively in 1933.

Year: 1932
Builder: Westinghouse
Bodystyle: Boxcab
Road numbers: 4701–4732
Notes: 4702 rebuilt to P5b in 1937.

Year: 1932
Builder: General Electric
Bodystyle: Boxcab
Road numbers: 4755–4774
Notes: 4770 rebuilt as Modified in 1945

Year: 1933
Builder: Westinghouse
Bodystyle: Boxcab
Road numbers: 4733-4742

Year: 1934
Builder: Altoona
Bodystyle: Modified
Road numbers: 4780

Year: 1935
Builder: Westinghouse
Bodystyle: Modified
Road numbers: 4743–4754

Year: 1935
Builder: General Electric
Bodystyle: Modified
Road numbers: 4775-4779

Year: 1935
Builder: Altoona
Bodystyle: Modified
Road numbers: 4781-4790

P5 prototypes

Two prototype locomotives were outshopped from the PRR's Altoona Works in 1931. 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). 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. A redesign was undertaken, giving the locomotives a central "steeple 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. 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. 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, differed from previous Modifieds in having an all-welded carbody, the type of construction famously utilized in the production run of the GG1. When the GG1s were put in passenger service, the P5s were re-geared and used in freight service for many years. The last of the class was withdrawn from service in April 1965.

P5b experiment
In October 1937 P5a No. 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, adding 1,500 hp (1,100 kW) to give a total power output of 5,350 hp (3,990 kW). This modification also meant that locomotive's entire weight was carried on driven wheels. Despite these advantages, the experiment was not repeated; #4702 continued in its modified form, however. Staufer & Pennypacker in Pennsy Power state that the experiment was less than successful due to problems in cooling the motors in the trucks.

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.