This right-side view of PRR T-1 No. 5526 was taken at Chicago's Englewood Union Station on May 14, 1946. Carl Weber supplied the image, by an unidentified photographer, from his collection. The PRR T-1 was equipped with oscillating-cam poppet valves for more precise timing of steam admission to, and exhaust from, the cylinders. Their dual drive, plus the absence of valve gear cranking on the drivers, meant their reciprocating parts were lighter than those of a conventional 4-8-4. The dual drive also made possible a shorter piston stroke for the same power output. At the same time, the T-1s were placed in regular service before all their "bugs" had been worked out. They were known for hard-to-control driving wheel slippage, not only while starting a train but also at speed. (Some authorities, however, claim this was due to poor throttle handling by inexperienced engineers.) The PRR tried to fix the slippage problem by outfitting one engine, No. 5547 reclassified T-1a, with conventional Walschaerts valve gear, while No. 5500 was given rotary cam poppet valves. But the engines began to be placed in storage around 1948, and thus were not in service long enough to correct the defects. For their specifications, see the commentary on No. 5527.