PENNSYLVANIA RAILROAD CLASS Q-2 4-4-6-4

A single class Q-1 4-6-4-4 duplex freight locomotive was built by the Pennsylvania Railroad in 1942. That the design was something of an experiment was borne out by the road selecting a proven Lima design for a Chesapeake & Ohio 2-10-4 when World War Two required additional freight power. Nevertheless, as soon as possible another experimental duplex locomotive was built which improved on some of the Q-1's shortcomings. New Q-2 class Number 6131 had a different wheel arrangement (4-4-6-4), smaller driver diameter and a more conventional cylinder arrangement. It should be emphasized that the Q' s were not articulated locomotives, the frames were rigid. No. 6131 proved to be much improved over the earlier Q-1 in service and an order for 25 Lima 2-10-4's was cancelled, and a new order for a like number of Q-2's placed with the road's Altoona Shops instead. Unlike other duplexes and articulated locomotives, the cylinder size of the front and back units were not the same, each set' s dimensions being set by the number of drivers they would power.

The new Q-2's were numbered 6175-6199 and were completed from February through June of 1949. The production series was basically quite similar to the experimental No. 6131 built in 1944. After decades of conservative locomotive practice, the new Q-2's embodied many radical practices to the Pennsylvania, such as Timken roller bearings on all axles, floating bushings on all valve gear pins, Worthington SA feedwater heaters, combustion chambers and Franklin Type E boosters on the trailing engine truck. Except for the passenger T-1 duplex locomotives, few other PRR steam locomotives enjoyed such features. Even a wheel slip controller was fitted to the Q-2's. This device automatically cut off steam to the cylinders when the drivers slipped more than half a revolution. When the slippage stopped, the steam supply was resumed, all automatically. This feature was not entirely successful, but was operational well before EMD and GE put wheel slip control in their most modern diesels in the 1980's. All of the Q-2's were equipped with Class 180-F-2 tenders, which held 422 tons of coal and 19,200 gallons of water.

The new Q-2's were assigned to the lines west of Pittsburgh, and were used particularly on fast freight runs to Chicago and Crestline, Ohio. Their achievements were unequaled, as they were capable of pulling more tonnage faster than any other PRR steam locomotive. In tests, they exhibited a maximum horsepower of 7,987 at 57.4 miles an hour, which was the highest such figure ever recorded for any steam locomotive in the world. The big engines proved to be very popular with crews, as their tremendous power, weight (which gave them a smooth tracking ability) and good coal consumption were considerable improvements over other PRR locomotives.

In use, the Q-2's proved to be hard to maintain, especially with shop crews who were not familiar with the many new accessories not found on older PRR power. While very economical on coal, the big 4-4-6-4's were the opposite with water and after as little as one and half hours of hard use, were in need of replenishment. They were also unfortunate in being built at a time when the diesel-electric freight locomotive had already indicated its superiority in economy over the steam locomotive. With delivery of new diesel freight locomotives, the PRR decided to set aside their most modern and complex locomotives and by the end of summer of 1949, all were in storage, most of them at Crestline, Ohio. They were not used again, while thousands of older steam locomotives continued in service. Number 6131 was dropped from the roster in 1952, with Numbers 6175-6185 following in December 1953. The rest of the Q-2's were officially dropped in late 1955, after spending more time in storage than they saw in service.

SPECIFICATIONS

Drivers: 69" Cylinders: Front: 19¾" X 28" Rear: 23¾" X 29" Total Engine Weight: 619,100 Lbs.

Weight on Drivers: 393,000 Lbs. Boiler Pressure: 300 Lbs.

Tractive Effort: 100,800 Lbs. With 15,000 Lbs. TE from trailing truck booster.