P E N N S Y L V A N I A   R A I L R O A D   S Y S T E M  15
Iron City - 1854
Eight-coupled Locomotive for Heavy Freight and Pushing Service 1854. Equipped with Baldwin Flexible Beam Truck and Variable Cut-off 
Cylinders, 19" x 22". Drivers, diam., 43". Weight, total engine, 66,000 lb. 
There were four Locomotives of this class. 
 
the frames--were of rather light construction, and some of the boilers were poorly stayed, so that explosions were relatively frequent. 
     In 1856, two Norris locomotives of improved design, with 16 x 24-inch cylinders and driving wheels 66 inches in diameter, were placed in passenger service on the Pennsylvania. These locomotives had the 		 a sliding block, forming the termination of the upper valve rod, could be adjusted and held at varying distances from the axis, thus producing a variable travel to the upper valve, The first Pennsylvania locomotive to which this device was applied was the "True American," a passenger. locomotive of the 4-4-0 type, with 16 x 22-inch cylinders and driving 
 
Stephenson shifting link motion, and were probably the first Norris engines to be so equipped. Valve gear design was a live topic at this time, and the importance of a simple and yet effective device for varying the point of cut-off at the will of the engineman was becoming fully recognized. Mr. Baldwin, in 1853, had patented a variable cut-off which used a separate valve sliding on a partition plate in the steam chest, and worked by an independent eccentric and rock shaft. The upper arm of this rock shaft was curved to form a radius arm, on which
Baldwin Passenger Locomotive - 1854
Baldwin Passenger Locomotive with Independent Variable Cut-off, as built in 1854 
The "Belie," "Flirt" and other eight-wheeled Pennsylvania Locomotives of the period were generally similar to this design. 

 
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