For his senior thesis in mechanical engineering at Cleveland’s Case School of Applied Science (Now Case Western University), undergraduate Norman F Zapf chose to test the feasibility of streamlining a 4-6-4 Hudson type engine. Zapf was familiar with Tietjen’s work at Westinghouse and with tests underway at Canada’s National Research Laboratories, where J.J. Green had, since 1931, been applying drag-reducing shells to steam engines.


Zapf concluded from wind-tunnel test on scale models (with and without shrouds) that a typical top passenger-train speed of 75 miles per hour, with streamlining reduced drag by 91 percent; with crosswind effects the results were even better. By his calculations, a standard steam engine would expend 350 horsepower more than a streamlined locomotive with both operating at top speed, and his graphs showed that streamlining offered some power savings even below 50 mph. The model shroud was altered to facilitate maintenance on the running gear.
Nearly all of Zapf’s suggestions were incorporated in America’s first streamlined steam engine, the Commodore Vanderbilt, which rolled out of the New York Central’s Albany shops in December of 1934. A three-year-old engine had been given a black zephyr-like shroud from which only the handrails protruded. A trough along the top channeled smoke up and over the cab. Preliminary tests indicated that in the 70 to 110 range, streamlining would effect a 2.5 to 12 percent increase in pulling capacity over standard engines. The Commodore Vanderbilt was quickly assigned to one section of the prestigious 20th Century Limited operating between New York and Chicago.