PRR P5

PRR P5
P5a (modified) #4780.
Power type	Electric
Builder	PRR Altoona Works (13) Baldwin-Westinghouse (54) General Electric (25)[1]
Build date	1931–1935
Total produced	92
Configuration	4-6-4
UIC classification	2'Co2'
Leading wheel diameter	36 in (910 mm)[2][3][4]
Driver diameter	72 in (1,800 mm)[2][3][4]
Trailing wheel diameter	36 in (910 mm)[2][3][4]
Wheelbase	49 ft 10 in (15.19 m) (total); 20 ft (6.1 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 (3.2576 m) (P5a (modified))[4]
Height	15 ft (4.6 m) over locked-down pantographs[2][3][4]
Axle load	74,000 lb (34 t) (P5, P5a)[2]; 77,800 lb (35.3 t) (P5b)[3]; 77,000 lb (35 t) (P5a (modified))[4]
Weight on drivers	220,000 lb (100 t) (P5, P5a)[2]; 444,700 lb (201.7 t) (P5b, all wheels driven)[3]; 229,000 lb (104 t) (P5a (modified))[4]
Locomotive weight	392,000 lb (178 t) (P5, P5a)[2]; 444,700 lb (201.7 t) (P5b)[3]; 394,000 lb (179 t) (P5a (modified))[4]
Electric system	11 kV AC @ 25 Hz
Current collection method	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	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	Pennsylvania Railroad
Number	4700–4791
Preserved	4700
Disposition	Museum of Transportation in St Louis, Missouri

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.

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 unpowered truck at each end.^[2][3][4]

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	Builder	Bodystyle	Road numbers	Notes
1931	Altoona	Boxcab	7898	Renumbered 4700 in 1933
1931	Altoona	Boxcab	7899	Renumbered 4791 in 1933
1932	Westinghouse	Boxcab	4701–4742	4702 rebuilt to P5b in 1937
1932	GE	Boxcab	4755–4774	4770 rebuilt as Modified in 1945
1934–1935	Westinghouse	Modified	4743–4754
1935	Altoona	Modified	4775–4790

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

As tests proved the P5 design sound, unsurprisingly since it was an evolution of previous practice, orders were placed for 90 production locomotives, classified P5a due to minor changes from the prototypes (most notably, larger traction motor blowers).^[1] Production was split largely 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 (BLW).

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 "steeple cab", raised higher, with narrower-topped, streamlined "noses" to the locomotive to enable the crew to see forward. This design was carried forward to the GG1, R1, and DD2 designs.

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]

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 5,350 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.^[1]

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. ^ ^{a b c d e f g h} Staufer, Alvin (1962). Pennsy Power. Staufer. p. 298. LOC 62-20878. 
2. ^ ^{a b c d e f g h i j k l m} Pennsylvania Railroad. "P5 & P5a". PRR Locomotive Diagrams. http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=p5_p5a.gif&sel=ele&sz=sm&fr=. Retrieved 2008-08-29. 
3. ^ ^{a b c d e f g h i j k l m} Pennsylvania Railroad. "P5b". PRR Locomotive Diagrams. http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=p5b.gif&sel=ele&sz=sm&fr=. Retrieved 2008-08-29. 
4. ^ ^{a b c d e f g h i j k l m} Pennsylvania Railroad. "P5a (modified)". PRR Locomotive Diagrams. http://prr.railfan.net/diagrams/PRRdiagrams.html?diag=p5b.gif&sel=ele&sz=sm&fr=. Retrieved 2008-08-29. 
5. ^ Pennsylvania Railroad Technical and Historical Society (August 2004). "PRR Chronology 1965". http://www.prrths.com/Hagley/PRR1965%20June%2004.wd.pdf. Retrieved 2008-08-30. 

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