At the end of the 1930s, modern super power steam - which took the form of 4-8-4s and high-speed articulateds on many other Class 1 railroads - was nearly nonexistent on the Pennsy. Outside of its electrified divisions, the self-proclaimed "Standard Railroad of the World" was still moving tonnage with massive fleets of steam engines largely designed in the World War I era. As a waning Depression and looming war brought the prospect of greatly increased traffic, Baldwin Locomotive Company approached the Pennsy with a design it claimed was far superior to conventional 4-8-4s. In Baldwin's "duplex" design, an engine's eight or ten drivers were split into two groups, each powered by its own pair of cylinders. Unlike an articulated, all drivers on a duplex were mounted on a single rigid frame. With shorter side rods and thus lighter moving parts, a duplex was supposed to be easier on the track, have lower maintenance costs, and be more stable at high speeds than a conventional locomotive. In the end, however, most production duplexes would deliver few, if any, of these benefits.
Perhaps the Pennsy's greatest mistake was ignoring the practice that had made its existing fleet so successful and long lasting: exhaustive testing of each new design before committing to mass production. Four duplexes of three different types were tested only briefly in the early 1940s before orders were placed for 50 class T1 passenger engines and 26 class Q2 high-speed freighters. In actual service, the 4-4-4-4 T1s proved prone to slipping at startup and at speed, with one or both sets of drivers unpredictably losing their footing and then suddenly regaining adhesion. Needless to say, this resulted in a less-than-acceptable ride for passengers on the premier Pennsy expresses the T1 was designed to pull.
With smaller drivers and more weight on each driver, the 4-4-6-4 Q2 freight engine was the least prone to slippage of all the duplexes, and in fact might have become a successful design - but for the onslaught of the diesel. Aware of the slippage problems with duplexii, the Q2's designers incorporated a wheel slip controller that automatically cut off steam to a set of drivers that was beginning to slip. On the Pennsy's stationary test plant in Altoona, a Q2 recorded an astounding 7,987 hp, the highest reading ever. Out on the road, crews generally liked the big engines, despite their huge appetite for water. But in the shops and on the balance sheet, unusually high maintenance costs and superior diesels were the Q2s' undoing, and in 1951 they were among the first classes of steamers to be retired.
The massive Q2 returns to the Premier lineup for 2010, upgraded with wireless drawbar and cab-to-tender deck plate. Our model replicates the prototype's tremendous pulling power but, thanks to M.T.H. engineering, it runs smoother and more dependably than the real engines ever did.
Did You Know?
The 26 class Q2 engines were built at the Pennsy's Altoona shops in 1944-45. They replaced a canceled order for 25 2-10-4 locomotives that had been placed with Lima in 1943, which would have been similar to the road's J1 class.