than the Big Boy, with 7,200 hp and 6,345 hp respectively. The large Belpaire firebox met the Pennsy's standards; its heating surface area included that supplied by seven American Arch circulators. Water passed through 5.5-inch horizontal tube met at the centerline with the other cross tube forming the bottom of the 7-inch vertical tube that sprayed the water up into the steam space above the crown sheet. The lowest set pair of tubes was forward with the side openings of the other six steadily rising toward the back. A large Worthington 6 SA feedwater heater was fitted with a 7 SA pump to handle the enormous boiler's thirst. The six-wheel leading and trailing trucks were added, as the locomotive was too heavy for four-wheel units. The streamlined Art Deco styled shrouding of the locomotive was designed by Raymond Loewy, a design concept based on his earlier streamlining design for PRR K4s #3768 in 1936, for which he received U.S. Patent No. 2,128,490. Raymond Loewy conducted the wind-tunnel test by using the clay model of S1 at Guggenheim Aeronautical Laboratory for the design of its streamlined shrouding, and it was the same laboratory where he conducted testing of the streamlining of PRR K4s #3768. The design of the smoke lifting plate around the smokestack on S1 was improved based on the wind-tunnel test result from Guggenheim. Construction costs and testing The cost of the S1 was $669,780.00, equal to $ today, which was over twice the cost of a PRR T1 4-4-4-4 (#6111 cost $310,676). No. 6100 was completed at Altoona on December 21, 1938 without the streamlined casing. On the same day, it made its first road test with two cars, running backward to Huntingdon and returned to Altoona at speeds up to . During the run, it was stopped and checked for overhang on all tight curves. Assistant Chief of Motive Power-Locomotive Carleton K. Steins (1891-1973) noted superior riding and steaming qualities. During another pre-service road test, the S1 was clocked at towing 90 freight cars. 1939 World's Fair display The S1 was displayed at the New York World's Fair of 1939–40 with the lettering "American Railroads" rather than "Pennsylvania Railroad", as 27 eastern railroads had one combined exhibit, which also included the Baltimore and Ohio Class N-1. To reach the Fair, the S1 took a circuitous route over the Long Island Rail Road. Many obstacles, like some of