In 1942, the PRR built an experimental duplex drive freight locomotive, the Q1, with a 4-6-4-4 wheel arrangement. In 1944, after identifying a number of flaws with the Q1, teh PRR built a second prototype, changing the wheel arrangement to 4-4-6-4 and creating class Q2. This was followed by 25 production Q2s in 1945. These rigid-frame four cylinder locomotives may have been the epitome of auperpower steam locomotive design. At 115,800 lbs of tractive effort and nearly 8,000 horsepower, the Q2 were the most powerful ten-coupled steam locomotives ever produced. These monsters were the greyhounds of the PRR, single-handedly hauling tonnage at high speeds over the PRR's lines. Mostly seen on the Pennsy west of Pittsburgh, these locomotives did venture east to territory such as Horseshoe Curve and their birthplace, Altoona. The Q2 was emblematic of the PRR's commitment to on-line coal producers to continue to use steam locomotives to power their trains after World War II. However, the Q2 could not match the maintenance records of the invading diesels and, by 1956, the last Q2 had been retired and scrapped. No example of this titan of the rails was saved for posterity.