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. 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 National Museum of Transportation in St Louis, Missouri.
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. 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 	Boxcab 	4701–4732 	4702 rebuilt to P5b in 1937
1932	General Electric	Boxcab 	4755–4774 	4770 rebuilt as Modified in 1945
1933	Westinghouse 	Boxcab 	4733-4742 	
1934	Altoona 	Modified 	4780 	
1935	Westinghouse 	Modified 	4743–4754 	
1935	General Electric	Modified 	4775-4779 	
1935	Altoona 	Modified 	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 The last of the class was withdrawn from service in April 1965.
== 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 each 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 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 in February 1944, differed from previous Modifieds in having an all-welded carbody, the type of construction famously utilized in the production run of the GG1.
== 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, 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 [de] 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, the 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.
== Gallery ==
File:Pennsylvania Railroad Class P5 No. 4700.jpeg
Category:Electric locomotives
Category:4-6-4 locomotives
Category:Sole survivor
Category:Pennsylvania locomotives
Category:Locomotives
Category:GE locomotives
Category:Altoona Works locomotives
Category:Baldwin locomotives
Category:Westinghouse locomotives
Category:Standard gauge locomotives
Category:Standard gauge locomotives of the United States
Category:Built in 1931
Category:Built in 1934
Category:Built in 1932
Category:Built in 1933
Category:Built in 1935