Pennsylvania Railroad Class Q2

Pennsylvania Railroad Class Q2
Front angle view of a Q2.
Technical specifications
Manufacturer(s)	Altoona Works
Build date	1944–45
Total produced	26
Classification	Q2
Rail gauge	4 Foot 8 Inches
Valve gear	Walschaerts
Cylinders	Four
Boiler pressure	300 psi (2.1 MPa)
Bore stroke	Front cylinder: 19+3⁄4 in × 28 in (502 mm × 711 mm) Rear cylinder: 23+3⁄4 in × 29 in (603 mm × 737 mm)
Fuel type	Soft coal
Performance figures
Maximum speed	50 mph with a 125 car train
Continuous power-output	7,987 hp (5,956 kW)
Tractive effort	100,816 lbf (without booster) / 115,816 lbf (with booster)
Factor of adhesion	3.9
Service information
Running numbers	6131 (Prototype) 6175–6199 (Production Locomotives)
Disposition details
Preserved	None Preserved
Disposition	All Scrapped

The Pennsylvania Railroad's class Q2 comprised one prototype No. 6131, and twenty-five production duplex steam locomotives Nos. 6175-6199, which they all operated with a 4-4-6-4 wheel arrangement.

They were all redeveloped and refined from the Pennsylvania Railroad's Q1 Duplex, which the Q1 duplex was a 4-6-4-4.

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.

The Q2 locomotive was 78% more powerful than the locomotives that PRR had in service at the time, and the company claimed the Q2 could pull 125 freight cars at a speed of 50 mph (80 km/h).

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 With dieselization, they were the obvious first targets to be withdrawn since they were only a little more capable than the conventional J1 class 2-10-4s but with far higher operating and maintenance costs. Q2 #6199's power output is 7,987 hp, making the Q2 class the most powerful rigid-frame steam locomotive in terms of horsepower, All 25 of the Q2s were withdrawn from active service, where they all had lingered in scrapyards until 1956. They were all cut up afterwards, leaving none left to be set aside for preservation.

Preserved Number Plates and Builders Plates

Despite none of the Q2s being preserved, two number plates from 6194 and 6130, and builders plate of 6179 still exits.

See also

• Gallery