The search for a high-speed, powerful freight locomotive led the Pennsylvania Railroad to the duplex-drive Q-1 of which only one example, No. 6130, was built by the railroad's Juniata Shops in Altoona in 1942. The unusual 4-6-4-4 configuration had the rear engine facing "backwards," with cylinders smaller (19½x26 inches) than the front cylinders (23x28 inches) because they powered only four driving wheels. The reverse position of the rear engine was required to shorten the locomotive's wheelbase, which because of the high 77-inch drivers would otherwise have been too long for it to fit on railroad's turntables. The Q-1 sustained 300 p.s.i. of boiler pressure, developed 81,800 pounds of tractive effort, and weighed 593,500 pounds. A large 122-square-foot grate area was coupled with 5518 square feet of evaporative heating surface, plus 2290 square feet of superheating surface, to create a high steam-producing capacity.
The Q-1 was built semi-streamlined, as revealed by this railroad publicity photo, but as this image (from a Flickr site discontinued in 2008) reveals the locomotive later received a more conventional front end appearance and also lost its side skirting. Taken in Chicago in 1948 by an unnamed photographer, this image belonged to the Harold Vollrath collection and also appears on the North East Rails site. The Q-1 was an experiment that paved the way for the more successful Q-2 4-4-6-4.