PRR Q2

Pennsylvania Railroad class Q2
PRR Q2 prototype #6131
Power type	Steam
Builder	PRR Altoona shops
Build date	1944–45
Total produced	26
Configuration	4-4-6-4
UIC classification	2'BC2'
Gauge	4 ft 8 1⁄2 in (1,435 mm)
Leading wheel diameter	36 in (0.91 m)
Driver diameter	69 in (1.75 m)
Wheelbase	26 ft 4.5 in (8.039 m) (driving) 20 ft 4 in (6.20 m) (rigid) 53 ft 5.5 in (16.294 m) (locomotive) 107 ft 7.5 in (32.804 m) (locomotive and tender)
Length	124 ft 7.125 in (37.976 m) (locomotive and tender)
Width	11 ft 4 in (3.45 m) (storm windows open)
Height	16 ft 5.5 in (5.017 m)
Weight on drivers	393,000 lb (178,000 kg)
Locomotive weight	619,100 lb (280,800 kg)
Tender weight	430,000 lb (195,000 kg)
Locomotive & tender combined weight	1,049,100 lb (475,900 kg)
Tender type	PRR class 180F84, 8 axles, with conductor "doghouse"
Fuel type	Soft coal
Fuel capacity	39.86 short tons (36.16 t)
Water capacity	19,020 US gal (72,000 l; 15,840 imp gal)
Boiler pressure	300 psi (2.1 MPa)
Front cylinder size	19+3⁄4 × 28 in (500 × 710 mm)
Rear cylinder size	23+3⁄4 × 29 in (600 × 740 mm)
Power output	7,987 hp (5,956 kW)
Career	Pennsylvania Railroad
Number	6131, 6175–6199
Last run	1951

Front angle view of a Q2.

The Pennsylvania Railroad's class Q2 comprised one prototype and twenty-five production duplex steam locomotives of 4-4-6-4 wheel arrangement.

They were the largest non-articulated locomotives ever built and the most powerful locomotives ever static tested, producing 7,987 cylinder horsepower (5,956 kW) on the PRR's static test plant. They were by far the most successful duplex type. The duplex propensity to slip was combated by an automatic slip control mechanism that reduced power to the slipping unit.

Despite overall success, the Q2s were all out of service by 1951. With dieselization, they were the obvious first targets to be withdrawn since they were only a little more capable than the conventional J1 class 2-10-4s but with far higher operating and maintenance costs.

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