The Chicago & North Western bought nine Class E-4 oil burning Hudsons in
1938 from the American Locomotive Company and numbered them 4000 through
Class E-4 (Locobase 180)
Data from tables in 1947 Locomotive Cyclopedia; see also C&NW 10-1952 Locomotive Diagrams. Works numbers ran 68982-28987 in March 1938; 68988-68989 and 69028 in April.
Firebox heating surface included 140 sq ft of thermic syphons and arch tubes. Developed for the Chicago-Minneapolis run (400 miles in 400 minutes) in competition with the Milwaukee Road's Hiawatha, which was pulled by either the A-class 4-4-2s or the F-7 class 4-6-4s. The C&NW locomotives were streamlined and painted green and yellow.
Their "physical attributes" were very similar to the Milwaukee's F-7s, which were also built by Alco in the same year (Locobase 183). One striking internal difference: The E-4 had only eight 2-inch tubes, which together with the 196 3 3/4" flues, made up much of her heating surface. This ratio of tube to flue is almost as far away from the usual balance as a standard boiler could get. By comparison, the F-7s had 220 more square feet, divided among 60 2 1/4" tubes and 164 3 1/2" flues, a more typical arrangement. The E-4s also had a 9% larger grate.
The E-4s used Baker valve gear to operated piston valves (12" or 14" in diameter). In 1946-1947, they were converted to oil-firing and trailed tenders carrying 20,000 US gallons (75,700 litres) of water and 6,000 gallons (22,710 litres) of oil fuel. They weighed 379,500 lb (172,139 kg).
Despite the difference, however, there appears to have been little difference in how these engines steamed, which underscores the custom-build tendency of steam locomotive manufacturers that ill-fitted them to compete with the standardized diesels. In fact, the E-4s were soon displaced by diesels and ran the transcontinental route from Chicago to Omaha.