Class A 2-6-6-4 Norfolk & Western

The prototype

Norfolk & Western - Class A 2-6-6-4

(I am a lazy writer, this description originates from FineArt Models but has disappered since)

Among the finest steam power ever used in heavy coal train or high-speed freight service and perhaps, even the finest freight steam locomotives of all, were 43 homemade single-expansion articulateds built, not by a commercial builder but, by the railroad that owned and operated them. So perfectly suited for the conditions under which they ran, that the road continued producing them for fourteen years, until the end of steam.  These “thinking man’s articulateds” were known on the Norfolk and Western not by a nickname, but simply as Class A.

Impressive recording of the Class A's working, in fast freight, pusher and double heading services.

The best way to remember the old Norfolk and Western is as a railroad with enlightened management, focused on delivering a specialized product—coal—using specialized locomotives under specialized operating conditions.  Since World War I, the road had already upgraded many older locomotives, which gave it an opportunity to study their productivity very carefully.  When the depression hit, it retained its experience base by shortening work weeks rather than laying off people.  But management had already been thinking ahead to a new, higher-capacity locomotive so, as the depression eased in 1934, the design staff set to work on this new project.

They had two important factors in their favor: (1) the N&W’s superlative track and roadbed, which made slipping less likely even for a locomotive with a low factor of adhesion (i.e. relatively low weight for its starting tractive effort); and (2) the availability of high-heat content coal from the Pocahontas fields which, in a firebox of a given size, could maintain steam pressure in a relatively larger boiler.  Thus they designed the largest firebox that could be supported by a four-wheel trailing truck and mounted entirely behind the drive wheels, and then mated it to a huge boiler (larger even than the one on the road’s gutsy class Y compound 2-8-8-2s).  Twelve large 70-inch drive wheels fit perfectly underneath.  Yet their new locomotive was not intended to exceed 70 mph, so it could make do with only a two-wheeled pony (front) truck— hence a 2-6-6-4.

Maintenance considerations also affected their design in many ways. For example: (1) with the pony truck, there was no extra axle inserted behind the front cylinders (as on a 4-6-6-4), so front and rear engines could interchange running gear parts; and (2) while other roads switched from alligator crossheads to single-guide designs (which in many instances had heavy shoes that required two mechanics to remove), the N&W saw that it could better handle high piston thrust by switching back to the alligator arrangement (which, in the bargain) a single mechanic could maintain, working alone.

The designers did their homework well.  The resulting Class A locomotive was exceedingly efficient for its 573,000 lb. weight (some 200,000 lbs. less than either the Allegheny or Big Boy designs of 1941, with which its performance has since been compared).  Its continuous power curve reached a very high 6325 drawbar horsepower maximum at 40–45 mph, measured at the original boiler pressure of 275 psi, so the N&W used it mainly in bread-and-butter heavy coal service on flat terrain (east from Roanoke to the tidewater terminal at Norfolk and west from Williamson, West Virginia to Columbus, Ohio) where it could cruise at this speed (except for the helper district over the Blue Ridge just east of Roanoke, all the mountainous territory was left to the 2-8-8-2s).  Yet the boiler never ran out of steam, even after pressure was raised to 300 psi, so the A also made an exceptional mountain passenger engine (the first two, Nos. 1200 and 1201, were normally assigned to passenger service on the Roanoke, Virginia–Bristol, Virginia-Tennessee run before the advent of the famous Class J streamlined 4-8-4s).
 
Nos. 1200 and 1201 were out-shopped in 1936 and were quickly followed by eight sisters.  Wartime brought 25 more and then, in 1949–50, after all three major commercial builders had permanently abandoned steam locomotive production, the N&W built a final eight.  The last five of these, Nos. 1238–1242, were equipped with Timken lightweight roller-bearing drive rods, the only articulated locomotives ever built with this feature.

Throughout the ’50s, the N&W continued to increase the productivity of its engines.  In 1951, for example, studies showed that adding an auxiliary water tender could eliminate the need for some water stops and increase gross ton-miles per train hour (GTM) 31 percent on the 112-mile Kenova District between Williamson and Portsmouth, Ohio.  So the railroad rebuilt many older 16,000 gallon tenders for this purpose and increased the As’ tonnage ratings from 13,000 to 14,500 there, and by a comparable amount everywhere else across the system (virtually all photos taken after 1951 show them trailing this auxiliary tender).

One of the last group, No. 1239, was fresh out of the shops in 1952 when the Electro-Motive Division of General Motors came calling with its latest diesel locomotive, seeking to convince the N&W that it should buy their product.  In multiple test runs over the same Kenova District, the 1239 matched the diesel in all respects—tonnage, speed, and economy.  On one westbound trip with a 175-car train in October of that year, it achieved a whopping 518,700 GTM (i.e. an average of more than 32 mph hauling 16,042 tons).  Thus maintained in state-of-the-art condition and having vanquished the diesel once, the As continued as mainline power until they were withdrawn from service en masse in 1958 and 1959.  Yet to this day, thanks to the proliferation of photos that show them at their best and renovation of class A No. 1218 for excursion service in the late ’80s and early ’90s, they have retained their reputation as members of the “Elite” of steam

The model