This Broadway Limited Class Q2 4-4-6-4 Duplex steam locomotive is based on a unique Pennsylvania Railroad engine. 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, the PRR built a second prototype, changing the wheel arrangement to a 4-4-6-4 and creating class Q2. This was followed by 25 production Q2 steam locomotives in 1945. These rigid-frame four cylinder locomotives may have been the epitome of superpower steam locomotive design. At 115,800 lbs of tractive effort and nearly 8,000 horsepower, the Q2s 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 Pittsburg, 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. This Q2 model has full Paragon4 sound and DCC for realistic, reliable sound and motor control. The Paragon4 sound system works with all Broadway Limited Rolling Thunder(TM) advanced sound systems. Other features include a smooth-running flywheel-equipped drive, synchronized puffing smoke and integral GoPack capacitor, roadname-appropriate and era-appropriate detailing and magnetic knuckle couplers. The Class Q2 4-4-6-4 can be operated on all DCC systems as well as on standard DC railroads (with limited sound functionality). This model has wheels profiled to operate on Code 70 and larger rail and curves of 18" radius but larger curves are recommended. The Class Q2 4-4-6-4 Duplex is one of many