The "E2b": PRR’s Experimental Freight Electrics

Published: October 12, 2026

Pennsylvania Railroad class E2b was six experimental freight electrics from General Electric, numbered 4939 through 4944. Each was a B-B rated at 2,500 horsepower. The wire was the railroad’s 11,000-volt, 25-cycle catenary, and a transformer with a tap changer fed that current to alternating-current traction motors. Engines 4939 through 4942 arrived in 1951–52. General Electric built 4943 and 4944 as demonstrators to show the Great Northern, and the Pennsylvania bought them in March 1953. All six were scrapped in 1964.

The class letters E2b had already been used on a Pennsylvania 4-4-2 Atlantic. The locomotives on this page are the freight electrics of the early 1950s. Freight under the wire was still a P5a boxcab, and these six were General Electric’s half of a ten-engine experiment aimed at a replacement. They were built to multiple with the alternating-current engines already on the property, and the six were commonly made up as three pairs. The freight electric the railroad later bought in quantity is the E44.

A pair of Pennsylvania Railroad E2b electric locomotives with a freight train at North Philadelphia, about 1956, the lead engine's forward pantograph raised

A pair of Pennsylvania Railroad class E2b freight electrics with a freight at North Philadelphia, about 1956. The lead engine carries two pantographs, with the forward one raised. Photographer unknown. American-Rails.com collection.

On this page: At a glance · Ten experimentals · Straight alternating current · Specifications · Roster · On the railroad

At a glance

Item	Detail
Railroad	Pennsylvania Railroad
Class	E2b. Experimental freight electric
Road numbers	4939–4944. Six locomotives, numbered straight through
Builder	General Electric
Built	4939–4942 in 1951–52. Demonstrators 4943 and 4944, purchased March 1953
Wheel arrangement	B-B. Four axles, each motored
Line current	11,000 volts, 25 Hz AC, overhead catenary
Horsepower	2,500 per locomotive. A pair is 5,000
Work	Freight. Commonly three pairs. Able to multiple with a P5a
Disposition	Scrapped in 1964

Ten experimentals

The passenger motor under Pennsylvania catenary was the GG1. Freight was the P5a, a 2-C-2 from the electrification into Washington and Harrisburg. On the modified engines the crew sat back from the nose. By the early 1950s the P5a was an old locomotive for the job it was still doing. The railroad went looking for a freight electric it could order in quantity. What it bought first was a comparison.

Ten locomotives came out of that comparison. General Electric’s six are this class. Baldwin-Westinghouse delivered the other four in 1951, and those four tried the electrical path the next production engine would use. An ignitron rectifier took the alternating current off the wire and supplied direct current to the traction motors. Class E3b, numbers 4995 and 4996, rode on three two-axle trucks, a B-B-B, and was rated 3,000 horsepower. Class E3c, numbers 4997 and 4998, rode on two three-axle trucks, a C-C, from the same order. The full class list is on the electric roster.

All ten were scrapped in 1964. Baldwin-Westinghouse had left the locomotive business. The rectifier stayed. General Electric built it into the E44, delivered from 1960 through 1963, and that is the freight motor the experiment was reaching for.

Straight alternating current

An E2b looks like a step toward the diesel. Robert S. McGonigal’s note on the class makes the distinction that matters: the cab and the running gear followed diesel practice, and the motors were conventional alternating-current machines, the family already under a P5a and a GG1. Line current at 11,000 volts and 25 cycles came down through the pantograph to a transformer. The tap changer set what the motors saw, and the motors took that current as alternating current.

That choice is why an E2b could run in multiple with the electrics the Pennsylvania already owned. The partner in those mixed sets was generally a P5a boxcab. On their own, the six were commonly kept as three pairs, each pair a 5,000-horsepower freight locomotive. The lead engine in the North Philadelphia photograph carries two pantographs, with the forward one against the wire.

The published class figures are 2,500 horsepower, 35,400 pounds of tractive effort, and 65 miles an hour. The class table gives the tractive effort as that single figure.

Specifications

Item	Detail
Class	E2b
Type	Experimental freight electric
Wheel arrangement	AAR B-B. Four axles, all powered. UIC Bo-Bo
Quantity	6
Road numbers	4939–4944
Builder	General Electric
Order engines	4939–4942, delivered 1951–52
Demonstrators	4943 and 4944, built for General Electric to show the Great Northern, purchased by the Pennsylvania in March 1953 and numbered into the class
Line current	11,000 volts, 25 Hz AC
Current collection	Pantograph, from overhead catenary
Transmission	Transformer tap changer to AC traction motors
Horsepower	2,500 per locomotive
Tractive effort	35,400 lb, published as a single class figure
Maximum speed	65 mph, the published class figure
Multiple-unit	With the railroad’s other straight-AC electrics. Commonly paired with a second E2b, and also run with a P5a
Disposition	All six scrapped in 1964

Roster

Six locomotives, 4939 through 4944. Every engine is General Electric, class E2b, B-B, 2,500 horsepower, and every engine was scrapped in 1964. The four from the railroad’s order arrived in 1951–52. The two demonstrators were purchased in March 1953.

Road no.	Builder	How it joined the class	Disposition
4939	General Electric	1951–52 order	Scrapped 1964
4940	General Electric	1951–52 order	Scrapped 1964
4941	General Electric	1951–52 order	Scrapped 1964
4942	General Electric	1951–52 order	Scrapped 1964
4943	General Electric	Demonstrator. Purchased March 1953	Scrapped 1964
4944	General Electric	Demonstrator. Purchased March 1953	Scrapped 1964

On the railroad

The published record of the class is a handful of trains, which is about what six engines leave behind. In February 1954 Trains & Travel ran H. N. Proctor’s photograph of 4943 and 4939 at Potomac Yard, Severn, Maryland, ready to leave with train EC-5. The demonstrator and one of the order engines were already a pair in through freight. On July 5, 1955, a Fred R. Kern slide shows 4939 and a mate near Frankford Junction, on the Philadelphia electrification. The photograph at the top of this page is another pair at North Philadelphia, about 1956.

They were still at it late. A color slide dated August 15, 1960, shows 4944 at Enola, Pennsylvania, coupled to P5a 4733, the mixed multiple-unit set the class had been built to allow. The E44s were in delivery by then. The six E2bs were scrapped in 1964.

Sources

Robert S. McGonigal, “Pennsylvania Railroad electric locomotives,” Classic Trains, January 14, 2021. Class E2b: General Electric, 1951, B-B, 4939–4944, six locomotives, 2,500 horsepower, 11,000-volt AC catenary, conventional AC traction motors, cab and running gear following diesel practice, all scrapped. E3b 4995–4996, B-B-B, and E3c 4997–4998, C-C, Baldwin-Westinghouse, 1951, 3,000 horsepower, ignitron rectifiers.
Alvin F. Staufer and Bert Pennypacker, Pennsy Power: Steam and Electric Locomotives of the Pennsylvania Railroad, 1900–1957 (Carrollton, Ohio: Alvin F. Staufer, 1962), pp. 300–301. The class accounts cite these pages for the experimental program, the March 1953 purchase of demonstrators 4943 and 4944, operation in three pairs, straight-AC power, and multiple-unit service with the P5a.
William D. Middleton, The Pennsylvania Railroad Under Wire (Milwaukee: Kalmbach, 2002). Cited with Staufer for the class.
William D. Volkmer, Pennsy Electric Years (Edison, N.J.: Morning Sun Books, 1991), pp. 30 and 126. Cited for the class in the same accounts.
H. N. Proctor photograph, Trains & Travel, February 1954, p. 16. Numbers 4943 and 4939 at Potomac Yard, Severn, Maryland, with train EC-5. The issue’s article is Henry F. Dimmler, “Pennsy’s New Juice Jacks,” pp. 15–21.
The electric class list on this site, which follows the Classic Trains grid and places 4939–4942 in 1951–52 and the demonstrators in 1953.

Facebook X Pinterest Tumblr Reddit WhatsApp Messenger