Designing the S1 Locomotive

In 1937 Pennsylvania Railroad decided to build a new passenger locomotive to replace its venerable K4 4-6-2s, designed in 1914. The company produced the S1, a spectacular 6-4-4-6 and the largest rigid frame passenger locomotive ever built. They hoped the S1 could haul 1,000 tons at an ambitious 100 miles per hour, but it's length limited its use and its axle loading was undesirably high. Loewy's 1978 lithograph shown at top right was based upon the 1937 drawing shown at bottom right. The S1 looked fast even when it was sitting still. The one-of-a-kind experimental model was exhibited at the 1939 World's Fair in New York City, where it was displayed in operation on rollers. The 1933 Chicago World's Fair and the 1939 New York World's Fair both emphasized the "World of Tomorrow" that would define industrial design for much of the 20th century.

Pennsylvania Railroad ordered two revised locomotives, nos. 6110 and 6111, and these became the first T1s. With poppet valves, light-weight motion, roller bearings, disk wheels and styling by Raymond Loewy, they were modern in every respect. On trial runs in 1944, No. 6110 produced an impressive 6,110 drawbar horsepower and 6,552 indicated horsepower at 85 miles per hour. The T1s were magnificent machines and with their 80-inch drive wheels they could average over 100 miles per hour with a train of 1,000 tons. They might have pointed the way toward future developments in high-speed, long-distance passenger service but their complexity worked against them.