PRR DD2

PRR DD2
Type and origin
Power type	Electric
Builder	PRR Juniata Shops[1]
Build date	February 7, 1938[1]
Total produced	1[1]
Specifications
Configuration	4-4-0+0-4-4
AAR wheel arr.	2-B+B-2
UIC classification	(2'B)(B'2)
Gauge	4 ft 8 1⁄2 in (1,435 mm)
Leading wheel diameter	36 in (914 mm)
Driver diameter	62 in (1575 mm)
Trailing wheel diameter	36 in (914 mm)
Length	72 ft 6¼ in (22.10 m)
Width	10 ft 6¼ in (3.21 m)
Height	15 ft 0 in (4.57 m) (pantographs locked down)
Weight on drivers	296,000 lb (134,000 kg)
Locomotive weight	450,000 lb (204,000 kg)
Electric system(s)	11 kV, 25 Hz overhead AC
Current collection method	2 roof-mounted pantographs (normally only one raised)
Traction motors	4 × 1250 hp Westinghouse 428-A traction motor paired sets
Transmission	AC current fed via transformer tap changer to motors geared to a Quill drive
Performance figures
Maximum speed	70 mph (113 km/h)
Power output	5,000 hp (3,700 kW)
Tractive effort	71,500 lbf (318 kN)
Career
Operator(s)	Pennsylvania Railroad
Class	DD2
Number in class	1
Number(s)	5800
Locale	Wilmington, Delaware-Philadelphia, Pennsylvania, latterly Baltimore, Maryland area.
First run	1938
Scrapped	September 1962[2]
Disposition	Scrapped

The Pennsylvania Railroad's class DD2 electric locomotive was a single prototype locomotive never placed into series production.^[3] It was intended as an improved and simplified GG1 for use on the planned, but never built, extension of the PRR's electrification west of Harrisburg, Pennsylvania.^[1] The one locomotive produced was numbered #5800 and used in regular Baltimore tunnel helper service until it was scrapped in September 1962.^[2]

Design, construction and testing

On May 21, 1937, a meeting was held in Philadelphia to outline the design of a new electric freight locomotive. The meeting was attended by the PRR and Baldwin, as well as electrical suppliers General Electric and Westinghouse, and the transportation engineering firm Gibbs & Hill, who were consultants on the proposal to extend electrification to Pittsburgh. The locomotive being designed was what became the DD2.^[4]

Technical details

Although the design specified either passenger gearing or freight gearing, the prototype was only ever used with freight gearing. Its wheel arrangement was 4-4-0+0-4-4 in the Whyte notation, or 2-B+B-2 in the AAR's system.

It had two frames, hinged together in the middle, with the driving wheels and motors mounted directly to each frame, two pairs per side. A swinging four-wheeled, unpowered truck was mounted at the outer end of each frame. The bodywork, mounted above, swivelled on mounts on each of the two main frames. This was an identical layout to the better-known GG1 electric locomotives, but with four driven axles instead of six. Each driven wheel had two electric motors, each rated at 625 hp, giving a total rating of 5,000 hp for the locomotive.

Although it had fewer driven wheels than the GG1, the total power output was slightly greater, thanks to newer and more powerful motors. Weight on the driven wheels was approximately 286,000 lb.,^[5] compared to the GG1's 300,000 lb, meaning that in similar conditions of adhesion the GG1 was slightly at an advantage in terms of applying power to the rail, but the difference was not great. Styling was also similar to the GG1's.

References