With 70-inch drivers and roller bearings on all axles, the N&W's original class A was capable of handling everything from coal drags and merchandise freight through heavy passenger service. They had four 24x30-inch cylinders, weighed 573,000 pounds, and sustained 300 p.s.i. of boiler pressure. Their massive firebox, large enough to hold an automobile, boasted 122 square feet of grate area. Their boiler had 6645 square feet of evaporative heating surface, and they had 2703 square feet of superheating surface. This Norfolk & Western builder's photo of 2-6-6-4 No. 1238, scanned from the 1951 edition of World Railways, shows the final development of the class A in 1950. Notable in the photo are the roller-bearing side and main rods for further reduction in friction. In addition, the boiler pressure was reportedly raised to 315 p.s.i., the driving wheel diameter was reduced to 69½ inches, and the cylinder diameter increased to 24½ inches. These modifications would have raised their tractive effort from 114,000 pounds to more than 138,000 pounds.