The reference for locomotives and railcars
Pennsylvania class Q2
United States | 1944 | 26 produced
Nr. 6180 at Crestline, Ohio
Nr. 6180 at Crestline, Ohio
collection Taylor Rush

The Q2 was created after the duplex prototype of the Q1 class with three driving axles at the front and two at the rear. This was only intended for freight transport and the number of driving axles in the first and second chassis groups was reversed compared to the Q1. As with the Q1, all the driving axles were mounted in the frame and the engines were divided to avoid too long connecting and coupling rods

Since the front chassis group had only two axles, the cylinders here were smaller than in the rear. In contrast to the Q1, the rear cylinders were still in front of the associated driving axles. Each group was prevented from slipping by an automatic apparatus. A booster was also installed in one axle of the trailing bogie

Overall, the Q2 is considered the largest non-articulated steam locomotive of all time. In static testing, one of the locomotives achieved an output of almost 8,000 hp. This made it possible to pull 125 loaded freight cars at a speed of 50 mph. On the other hand, maintenance was very complex.

In addition to the prototype, 25 production locomotives were built, making the Q2 the most successful duplex locomotive. However, the PRR fleet also included the class J1 with the 2-10-4 wheel arrangement which, with a nominal output of 5,650 hp, achieved almost the same starting tractive effort and was significantly easier to maintain. In addition, more and more diesel locomotives were added. This resulted in the Q2 being out of service by 1951.

Axle config4-4-6-4 (Duplex) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length124 ft 7 1/8 in
Wheelbase53 ft 5 1/2 in
Fixed wheelbase20 ft 4 in
Total wheelbase107 ft 7 1/2 in
Service weight619,100 lbs
Adhesive weight393,000 lbs
Total weight1,049,100 lbs
Axle load79,780 lbs
Water capacity19,000 us gal
Fuel capacity75,000 lbs (coal)
Power sourcesteam
Indicated power7,987 hp (5,956 kW)
Optimal speed63 mph
Starting effort100,816 lbf
Booster15,000 lbf
Power Plant
Driver diameter69 in
Boiler pressure300 psi
Expansion typesimple
Cylindersfour, front: 19 3/4 x 28 in
rear: 23 3/4 x 29 in
Grate area121.7 sq ft
Firebox area725 sq ft
Tube heating area6,000 sq ft
Evaporative heating area6,725 sq ft
Superheater area2,930 sq ft
Total heating area9,655 sq ft
Calculated Values
steam locomotive
last changed: 07/2023

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