Chesapeake & Ohio 2-6-6-6 "Allegheny" Locomotives of the USA

An Allegheny Locomotive

Class Details by Steve Llanso of Sweat House Media

Class H-8 - 1600 (Locobase 304)

Data above from Locomotive Cyclopedia 1947, amended and corrected by C&O 4 -1947 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

Built in several batches: 1600-1609 in 1941 (works numbers 7820-7823 in December 1941, 7824-7829 in January 1942), 1610-1619 in 1942 (works numbers 7883-7892 in September), and 1620-1644 in 1944 (works number 8613-8622 in July, 8799-8813 in October-November).

The 1948 locomotives--1645-1659--were copies of the Virginian's AGs (Locobase 421), which had less heating surface and were a bit lighter; see Locobase 11065.

Firebox had three syphons and arch tubes combining for 162 sq ft of heating surface as well as a huge combustion chamber. Each cylinder was served by a 12" (306 mm) piston valve. All engine and tender axles turned inside Timken roller bearings. A Worthington Type 6 1/2 SA feed water heater raised the temperature of incoming boiler water.

H-8s could operate 11,500-ton coal trains at speeds up to 45 mph (72.5 km/h). Probably the heaviest twelve-axle locomotives ever built, with certainly the highest axle load ever put on rails. Average axle load was 84,650 lb (38,397 kg) and the first driving axle bore 86,700 lb (39,327 kg).

C&O Power gives higher weight on drivers (507,900 lb for the first batch, 504,010 lb for the 1948 engines), and heavier engine weights (771,300 lb and 751,830 lb, respectively.) The answer is that Cyclopedia weights were as designed, which specified 471,000 lb on the drivers, 724,500 for the engine. C&O Power weights came from C&O drawings.

Bob Quehl ( from Pittsburgh, PA offered considerable detail on the difference as well as other information ( Feb 4 2000, 4:06) " In the December 1998 issue of Trains Magazine there is a very interesting article that suggests the first 10 H-8s delivered in December 1941 to January 1942 weighed actually weighed in the area of 775,330 lbs in "working order". This was just the engine weight including water in the boiler, 12,000 lbs of sand in the domes an a two man engine crew. This is interesting because the specifications for the order between the C&O and Lima called for a weight of 726,000 lbs."

Quehl implies that it was the Virginian's order of eight in 1945 that finally exposed the disparity. "One engineer at Lima gave the H-8's weight as high as 778,200 lbs. For the engine and tender combined weight I have seen several references in other sources around 1,200,000 lbs."

There are many (including Eugene Huddleston and Thomas Dixon, Jr in their book Allegheny: Lima's Finest) who contend that C & O's oversight of the design by its Advisory Mechanical Committee contributed mightily to the problem. One example cited is four different changes to the design of the connecting rods, each of which made them heavier. According to Huddleston and Dixon, Lima later paid the C & O a $3 million penalty for missing the weight targets by so wide a margin.

But did the C & O get what it paid for, whatever the cost in weight? It appears so, although the coal traffic they served didn't require the Challenger-like 67" drivers and massive tenders that this class deployed. To cope with an adverse grade of about 0.6%, the C & O would marshal 100 loaded coal cars, place one H-8 at the front and one at the rear and put the whole thing in motion. Once the train crested the summit, the pusher would drop off and the front H-8 would manage the train by itself.

23 were equipped for passenger operation, but if they were so used, it was to pull troop trains.

Class H-8 - 1644 (Locobase 11065)

Data above from Locomotive Cyclopedia 1947, amended and corrected by C&O 4 -1947 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. Works numbers were 9390-9323 in December 1948.

See Locobase 304 for comments on the serious weight miscalculation in the original H-8 design. When adding to the stud, the C & O adopted the smaller design sold to the Virginian in 1945 (Locobase 421). The big change from the 1941 Alleghenies was a 21% cut in the number of flues for the Type E superheater, which was only partially offset by an increase in the 2 1/4" tubes of 10.

Firebox had three syphons and arch tubes combining for 162 sq ft of heating surface as well as a huge combustion chamber. Could operate 11,500-ton coal trains at speeds up to 45 mph.

Specifications by Steve Llanso of Sweat House Media
ClassH-8 - 1600H-8 - 1644
Locobase ID304 11,065
RailroadChesapeake & Ohio (C&O)Chesapeake & Ohio (C&O)
Number in Class4515
Road Numbers1600-16441645-1659
Number Built4515
Valve GearBakerBaker
Locomotive Length and Weight
Driver Wheelbase (ft)11.8311.83
Engine Wheelbase (ft)62.5062.50
Ratio of driving wheelbase to overall engine wheebase 0.19 0.19
Overall Wheelbase (engine & tender) (ft)112.92112.92
Axle Loading (Maximum Weight per Axle) (lbs)86,70085,480
Weight on Drivers (lbs)507,900504,010
Engine Weight (lbs)771,300751,830
Tender Loaded Weight (lbs)428,100431,710
Total Engine and Tender Weight (lbs)1,199,4001,183,540
Tender Water Capacity (gals)25,00025,000
Tender Fuel Capacity (oil/coal) (gals/tons)2525
Minimum weight of rail (calculated) (lb/yd)141140
Geometry Relating to Tractive Effort
Driver Diameter (in)6767
Boiler Pressure (psi)260260
High Pressure Cylinders (dia x stroke) (in)22.5" x 33" (4)22.5" x 33" (4)
Tractive Effort (lbs)110,211110,211
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.61 4.57
Heating Ability
Firebox Area (sq ft)762762
Grate Area (sq ft)135.20135
Evaporative Heating Surface (sq ft)72406795
Superheating Surface (sq ft)31862922
Combined Heating Surface (sq ft)10,4269717
Evaporative Heating Surface/Cylinder Volume238.37223.72
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation35,15235,100
Same as above plus superheater percentage46,04945,630
Same as above but substitute firebox area for grate area259,537257,556
Power L137,97235,276
Power MT988.94925.82

About the H-8 Weights

The engines of earlier H-8s (1600-1644) were listed as weighing 778,000 pounds. Engines of later H-8s (1645-1659) were listed as weighing 751,830 pounds. There has been much disagreement on the "778,000" number. The original C&O H-8 design, as agreed by Lima and the "Advisory Mechanical Committee" of the Van Sweringen roads, called for a total weight of engine (no tender) of 724,500 lbs. This was, in part, due to the 726,000 weight restriction of the C&O. During construction, the weight escalated to 778,500 lbs. (Other sources, including some C&O records show 775,330 lbs. as the "calculated working order weight"). In either case, Lima claimed the weight to be 724,500 lbs. Are you confused yet? It has been reported that Lima re-weighed numbers 1600 and 1630 and reported that they weighed 770,910 lbs and 771,670 lbs respectively. We will probably never have a definitive answer to this weight question or whether the Allegheny actually did weigh more than the Big Boy. For further research on this subject, one would have to reference:

The Virginian 2-6-6-6s came it at about 754,000 lbs, still overweight, but less so than the C&O engines. The final 15 C&O engines came in at 757,830 lbs. Lima ended up paying the C&O a penalty, perhaps as much as $3,000,000 because of this overweight problem.

No matter the actual locomotive weight, this weight makes the Allegheny the heaviest of any reciprocating steam locomotive built in North America, even heavier than the Big Boy.



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