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The Pennsylvania Railroad's class E2, E3, E7steam locomotives were of the 4-4-2 "Atlantic" passenger type, frequently called light Atlantics after the introduction of the heavier E6 Atlantics. All were similar in size and boiler capacity but differed in firebox type, valves and valve gear and cylinder diameter. Classes E2 and E3 were built simultaneously. Starting in 1916 a rebuilding program converted ninety class E2a,b,c to class E7s by replacing slide valves with piston valves and increasing cylinder diameter from 20.5 to 22.5 inches (520 to 570 mm). Fourteen class E2 were similarly converted to class E7sa. Ninety class E2a,d, E3a,d were converted to class E3sd. These improvements allowed many of the engines to remain in active service into the 1930s.
The sub-classes differed as follows:[2][page needed]
Class
Firebox
Cylinder size
Valves
Valve gear
Number built
Years built
E2
Radial-stay
20 ½” x 26”
Slide
Stephenson
88
1901-02
E2a
Belpaire
20 ½” x 26”
Slide
Stephenson
93
1902-05
E2b
Belpaire
20 ½” x 26”
Piston
Stephenson
70
1903-04
E2c
Belpaire
20 ½” x 26”
Slide
Stephenson
22
1903
E2d
Belpaire
20 ½” x 26”
Piston
Walschaerts
32
1906-08
E3
Radial-stay
22” x 26”
Slide
Stephenson
8
1901-02
E3a
Belpaire
22” x 26”
Slide
Stephenson
114
1903-05
E3d
Belpaire
22” x 26”
Piston
Walschaerts
56
1906-10
E7s
Belpaire
22 ½” x 26”
Piston
Stephenson
90 conv. fr. E2a,b,c
1916-20
E7sa
Radial-stay
22 ½” x 26”
Piston
Stephenson
14 conv. fr. E2
1916-20
In the first decade of the twentieth century classes E2 and E3 handled all of the fast passenger trains of the Pennsylvania Railroad. As train weights increased due to the switch to steel passenger cars and more cars per train, the “light” Atlantics were usually doubleheaded. Eventually, as Pacific class K2 and K3 became available, they were relegated to secondary service
Engine #7002[]
Main article: PRR 7002
This engine was built in 1902 as a class E2 for the Pennsylvania Railroad as engine No. 7002. On the first westward run of the Pennsylvania Special (renamed the Broadway Limited in 1912) in June 1905 the conductor clocked the train over three miles just west of Lima, Ohio in 85 seconds, at a record speed of 127.1 miles per hour (204.5 km/h). (Many doubt the claim; the train averaged about 68 mph from Crestline to Fort Wayne.) No. 7002 was rebuilt to class E7sa in August 1916 and scrapped in 1935. When the PRR was looking for an E7 class locomotive for preservation, they refurbished No. 8063 (an E2a from the PRR) and substituted No. 7002’s engine number and builder’s plate. No. 8063 is a PRR E2a built in 1905. The engine was donated to Railroad Museum of Pennsylvania in 1979 and put into operating order by Strasburg Rail Road where it ran for a number of years, sometimes doubleheading with PRR D16 No. 1223. It last ran on December 20, 1989.