Conceived in the late 1930s as a replacement for the Pennsylvania Railroad's aging fleet of K4 Pacifics, the T1, according to Al Staufer in his book Pennsy Power, "was everything: beautiful, unusual, fast, slippery, success and failure." With the advantage of hindsight, we can see the T1 was a steam engine born when the steam era was virtually over, but that was not apparent to the Pennsy at the time. The T1 incorporated a number of very advanced design features. Although it looked like an articulated, it was actually a duplex: two engines on a single rigid frame. The idea was to eliminate all the moving parts (including flexible steam pipes) required to swivel the front engine of an articulated, yet retain the additional power offered by two pairs of cylinders. Instead of the piston valves used by most steam engines to control the flow of steam to the cylinders, the T1 used poppet valves, a design somewhat similar to the valves in an automobile engine. Based on tests with experimental K4 Pacifics, the Pennsy had determined that poppet valves performed better, especially at the higher speeds required in passenger service. Styled by famed industrial designer Raymond Loewy, the T1 represented the Pennsy's best hopes for a technologically advanced steamer that could compete with diesels.
Extensive testing of the first two T1s, delivered in 1942, indicated the new design was a winner - a single passenger engine capable of hauling a sixteen car train at a hundred miles an hour. Glowing reports from these tests convinced management to place an order for 50 additional engines. Pennsy's Altoona works and Baldwin Locomotive Works split the order, each producing 25 engines in 1945-46.
In actual service, however, the production T1s did not live up to the promise of the test engines. Although they were indeed speedy and powerful, the poppet valves turned out to be a maintenance nightmare. The fact that the mechanism was inside the frame made repairs particularly difficult. And the rigid duplex frame gave the engine an unfortunate tendency to rock back and put most of its weight on the rear drivers, allowing the front engine to slip uncontrollably. It took a very skillful engineer to keep a T1 pulling surely on all eight drivers. Given more time, these problems could perhaps have been solved, but in the late 1940s time was up for the steam locomotive. In the end, the T1 was a grand, handsome experiment that failed.
For 2014 the Pennsylvania T1 returns to the M.T.H. lineup in two Special Edition train sets. Each more sure-footed than the prototype and featuring, for the first time, Proto-Sound 3.0 and Proto-Scale 3-2T 3-rail/2-rail compatibility. Available in freight or passenger configurations, each set includes authentic Proto-EffectsT including the New York-Chicago Broadway Limited Passenger Station sound set for the passenger set. The Premier T1 is the only die-cast O scale model of the original 1942 engines, which bore the full beauty of Raymond Loewy's styling: very angular prow, deep side skirting, front portholes, and fancy tender decoration. Engines 6110 and 6111 looked almost exactly like one of Loewy's original design sketches. In the 50 later production engines, Loewy's styling was compromised with a flatter prow and shorter side skirting; some engines also had a less stylized front end that exposed the cylinders.