Pennsylvania Railroad class Q1

The Pennsylvania Railroad class Q1, #6130, was a single experimental steam locomotive designed for dual service. The locomotive entered service in 1942, and retired in 1949 after accumulating a relatively low 165,000 service miles.

The Q1 had a 4-6-4-4 wheel arrangement, consisting of a four-wheel leading truck, two sets of driving wheels (six and four) in a rigid locomotive frame, and a four-wheel trailing truck. The first group of six driving wheels were powered by a pair of conventional front-mounted cylinders, while the rear four driving wheels had their cylinders mounted behind them, on either side of the firebox. The driving wheels were 77 in (1.956 m), larger than the PRR's existing dual-service locomotives.

The Q1's streamlined design consisted of a blunt nosecone in front of the smokebox, extended side skirts covering the locomotive's pipework, and a streamlined shape on the tender similar to the PRR's S1, S2, and T1 passenger locomotives. The cab front was set at a rakish angle. While the overall design reduced drag compared to the PRR's existing J1 class, the streamlining was ultimately removed around 1944, due to the minimal benefits at low freight speeds, and increased maintenance costs.

The Q1 was ultimately considered a failure by both PRR and later rail historians. Between design shortcomings and high operational costs, particularly during increasing use of diesel locomotives, it was never approved for series production. Despite being designed as a dual-service locomotive, minimal evidence suggests it ever served in a passenger capacity. However, its design did inspire the moderately successful albeit short-lived PRR class Q2.