What was the most powerful steam locomotives ever built? The Big Boy? Nope. What was the heaviest steam locomotive ever built? The Big Boy? Well, maybe, maybe not. Read on to find out the answer.

In the 1930s, the C&O improved its railroad by boring new tunnels and enlarging others. The Class T-1 "Texas" type 2-10-4s also arrived in the early 1930s and seemed to be the choice for hauling its coal trains over the 80 miles of track from Hinton, WV east to Clifton Forge, VA. This run included a 13 mile .577% grade to the 2,072 foot summit of an Allegheny mountain and then a descent down a 1.14% grade to Clifton Forge. Its 2-6-6-2s were getting old and the 2-8-8-2s, delivered in the 1920s, (which used simple expansion because of tight tunnel clearances) were not up to the task. On the brink of ordering more 2-10-4s the C&O was approached by the Lima Locomotive Company with a new and more powerful locomotive design:

This design was a six-coupled, single-expansion articulated with 67" diameter drivers for speed, a 9' x 15' firebox with a very large boiler for steaming and 778,000 pounds of locomotive weight to assure tractive effort. The large fire box was placed behind the drivers and required a six-wheel trailing truck to support it. This gave the design a wheel arrangement of 2-6-6-6. With four 22.5" diameter x 33" stroke cylinders, a 260 psi boiler pressure and the 67" diameter drivers it could exert 110,200 pounds of tractive effort.

The C&O agreed and placed an order for ten of these 2-6-6-6 locomotives and Lima delivered them in December, 1941. They were designated Class H-8 and assigned road numbers 1600 through 1609. With a new wheel arrangement came a new name. The C&O selected the name "Allegheny" for the mountain range that this new locomotive would do its work. An article by King in "Trains" in the early 2000s stated that the C&O Alleghenies cost around $270,000.00 each.

The tenders for these new locomotives were of the largest type used on the C&O, with a 25,000 gallon water tank and a 25 ton coal bunker. In order to keep the overall length of the locomotive and tender within the limit that existing turntables could handle it was necessary to make the rear section of the tender higher, thus causing more weight to be at the rear than the front. The tender had a six-wheel leading truck, but an eight-wheel trailing truck was needed to carry the weight in the rear.

In operation, one "Allegheny" leading and one pushing could move a 140 car loaded coal train up the mountain from the Hinton terminal. At the top the pusher would be taken off, turned around and sent back to the Hinton terminal. The single leading "Allegheny" could handle the decent down the mountain to Clifton Forge where it would be turned around for a return trip with a train of empty coal cars.

The C&O had 23 of its "Alleghenies" equipped with steam heat and signal lines for passenger service, but they were used sparingly, pulling an occasional heavy mail train or a troop train during World War II. The "Allegheny" may have been the ultimate freight locomotive. They were able to achieve a very impressive record even though they were used in a manner that didn't fit perfectly with their design. The Allegheny boilers were capable of delivering up to 8000 HP! This was far greater than any other reciprocating steam locomotive could develop. However, the C&O used the H-8s in "coal drag" service where they were unable to realize their full potential as high speed locomotives. The C&O Alleghenies were designed to haul 5,000 tons at 45mph, but unfortunately were used to haul trains of 10,000 or more tons at 15mph. C&O's 2-6-6-6s were very impressive locomotives. However, they were never used to their full potential. The "Allegheny" was truly magnificent in its role, but as good as it was it could not win the battle with the diesel. The C&O's "Alleghenies" were taken out of service beginning in 1952 with the last fire dropped in 1956.

It should also be noted that the Alleghenies were some of the most powerful steam locomotives ever built. At 40 MPH they could generate 7,500 HP. This power was only exceeded by the PRR Q-2 Class (7,987HP). By contrast the UP Big Boy could generate a maximum of 6,200 drawbar HP.

Fortunately, two of the C&O "Allegheny" type locomotives survive today, number 1601 at the Henry Ford Museum in Dearborn, MI and number 1604 at the B&O Railroad Museum in Baltimore, MD.

After 1601 was retired, she was steamed to Detroit under her own power, and placed in storage inside (indoors) the Henry Ford Museum. Having been stored indoors has kept 1601 in immaculate condition. She is still leaking lube oil!

Upon retirement, 1604 was sent to the scrap lines behind the diesel shops at Russell, KY. It was donated to the Roanoke Transportation Museum circa 1969. At Roanoke, 1604 was displayed next to N&W 1218. On November 4th, 1985, it was partially damaged in a flood (N&W 1218 was gone by this time). During that flood, it almost turned over when the ground was washed out from under it! Fortunately, it leaning up against an overhead bridge pier which prevented it from falling any further. The NS did a cosmetic overhaul on 1604 at the Roanoke Shops before for it was sent (around 1987) to Baltimore to be displayed as the centerpiece of the Mt. Clare Junction shopping center which was adjacent to the B&O Museum. The shopping center was literally built around 1604. In 1989, the failing shopping center decided that 1604 was too big and decided to donate her to the B&O Museum. 1604 was moved from the mall onto B&O Museum property in early 1990 by SW-1 Pere Marquette 11. During the early 1990s, there was a rumor going around that the CSXT was considering starting their own steam excursion program. They reportedly sent some mechanics to check the condition of 1604 to see if it was feasible to restore it to operating condition! Apparently, those plans never came to fruition. Today, the cab has been cosmetically restored and lighting has been placed in the firebox so that it can be viewed.

Numbers 1600, 1602, 1603 and 1605-1659 scrapped between 1952 and 1956.

The Virginian was the only other railroad to have bought the 2-6-6-6. They needed more power during World War II and ordered eight 2-6-6-6s. They took delivery of them from the Lima Locomotive Works between March and June of 1945. These locomotives were designated as Class AG and assigned road numbers 900 through 907. On the Virginian these copies of the C&O "Alleghenies" were called "Blue Ridge" type locomotives. They used them for hauling coal trains well into the 1950s. All of the "Blue Ridge" locomotives were retired by 1955 and were scrapped by 1960.

Come on guys, debate with me!

3580867 I honestly don't think anything's up for debate. The 2-6-6-6s are the most powerful steam locos, at least in terms of horsepower.

3581421 Ah.

3581552 It probably would be nice to see one steamed up again, perhaps it could run on the new NS steam program.

Or (though it's not very likely at all) if CSX changes its policy and decides to allow steam locomotives to run on its tracks, 1601 or 1604 could be restored.

If a Big Boy of all locomotives can be restored and be allowed to steam again, anything's possible.

3581599 Seeing as that 1601 was placed indoors immediately, she is probably in the best shape. Like the article says, she is still leaking oil!

3581421 there were locomotives with a pretty large wheel combination.

3581790 Besides, The Big Boy, The Challenger, and the NW Class As, there was also the Erie triplex, and the Virgnian's 2-10-10-2s.

3581599 The problem is that the 2-6-6-6s caused a lot of wear and tear on the tracks due to their weight.

3581974 That was supposedly a reason why no one thought a Big Boy would be restored, in addition to the lack of turntables that could hold them.

3581968 add and extra set of drive wheels to a locomotive.
three sets of driving wheels.

3581996 3581968 True, but the Triplexes weren't successful because they couldn't keep pressure up, the rear set of drivers exhausted from a separate stack behind the tender, therefore not contributing any draft to the fire, and the rear set of drivers lost traction as the coal and water was used. The 2-10-10-2 was a drag loco, sure, but there were only 10 of them built.

3576717

Now, if you're talking about power in terms of tractive effort, Norfolk & Western's C-C-C-C Jawn Henry steam turbine had a starting tractive effort of 175,000 lbf.

3584699 I take it that locomotive didn't last long, even though the N&W was the last Class 1 American railroad to convert to diesel power.

3585477 Water leaks shorting out the traction motors, coal dust and fly ash clogging everything up, not to mention that the turbine blades were easily damaged if the locomotive was backed into a train too hard. This led to the Jawn Henry being used mainly as a "pusher" locomotive for its four-year lifespan.

3585477 most steam turbines didn't work well. The C&O's M1 had the same issues as Jawn Henry. On the other hand, the Pennsy's S2 6-8-6 steam turbine worked GREAT at high speed, but at low speed, it was too inefficient.

By all accounts, it was a great locomotive, since it was a direct steam drive, not an electric drive like the M1 and Jawn Henry.It used two Westinghouse turbines, one for forward motion, and one for backward motion. From Wikipedia:

The Pennsylvania Railroad's class S2 was a steam turbine locomotive. One was built, #6200, delivered in 1944. The S2 was the sole example of the 6-8-6 wheel arrangement in the Whyte notation, with a six-wheel leading truck, eight driving wheels, and a six-wheel trailing truck. The S2 used a direct-drive steam turbine; the turbine was geared to the center pair of axles with the outer two axles connected by side rods. The disadvantage was that the turbine could not operate at optimal speeds over the locomotive's entire speed range. The S2 was the largest direct-drive turbine locomotive design ever built.

The locomotive was to be a 4-8-4, but wartime restrictions on light steel alloys increased weight until six-wheel leading and trailing trucks were needed. Two turbines were fitted, one for forward travel and a smaller one for reversing at speeds up to 22 mph. A large boiler with a Belpaire firebox and long combustion chamber was fitted. The turbine exhaust was piped through a set of four nozzles in the smokebox, providing an even draft for the fire and exiting through a unique quadruple stack. A Worthington-pattern feedwater heater was fitted for increased efficiency. Twin air pumps for train braking were fitted below the running boards beside the smokebox front, and a large radiator assembly at the nose cooled the compressed air. The large 16-wheel tender was similar to that used on the PRR's other large passenger locomotives, the T1 and S1.

The locomotive proved to be powerful and capable, with reserves of power at speed and reasonable fuel economy. The turbine drive was easy on the track and allowed more power at the rail. While economical at speed, the locomotive was highly uneconomical at lower speed. The turbine used less steam than conventional locomotives above 30 mph; below that, the locomotive used too much steam and fuel. The boiler normally operated at 310 PSI, but at low speed the pressure could drop as low as 85 PSI. The increased fuel usage at low speeds caused the firebox to run hotter, which sometimes caused stay bolts to break.

3587220 Indeed. The UP had Gas Turbines, and those were taken out of service after a while because they weren't very fuel efficent.

3587220 As I mentioned several times already, the only successful steam turbines were the Turbomotive and the Swedish M3t-class, the latter of which still survive today. GE's steam turbines had a number of problems, but they were reportedly fixed before it was decided to scrap them for the war effort.

3587874 That's a shame. Just as much of a shame as when the NYC decided not to preserve any of its Dreyfus Hudsons, or 4-8-4 Niagras.

3580867
ok, have a couple of contenders:

The LNER P1s (at the very least, they were two of the most powerful in Britain, too powerful in fact, they were never used to their full potential)

The LNER U1 (a locomotive that's longer than the big boy without its tender, need I say more)

at the very least, they are in the top ten list of most powerful locomotives

oh, I almost forgot:

the Russian AA-20 4-14-4 (we never found out how powerful it was, as it kept derailing, straightening curves and wrecking points

3590193

too powerful in fact, they were never used to their full potential)

How so?

3590345 they were only cost effective pulling trains of 100+ wagons, any less and they were metaphorical gas guzzlers (well, coal guzzlers but you get the idea), there was only one schedualed 100+ wagon train a day on their route (Peterborough to London), plus due to the length of the train, if they were late leaving, they had to wait until the next day.

that's one of the reasons I can think of off the top of my head, more info can be found here

3590371 Such a shame. It looks like they just came at the wrong time.

3590382 wrong country more like, our (UK's) longest route is about 400 or so miles, most coal trains were made up of 4 wheel wagons that could only take between 10 and 12 tons of coal each:

at least they were colourful:

that is why I'm planning a model railway set in the 1920's-1940's.

there is was so much colour

now everything is so uniformed in colour, it's boring from a modelling perspective

3590193 The Allegheny's were never used to their full potential, either. They could have been as successful as the Big Boys if they were used on fast freights, but the C&O and Virginian only used them for drag service. Really, the only "get it there ASAP" cargo the Allegheny hauled was troops during WWII, and that was only if nothing else was available.

3590397 That is why I want to model teh late 30's-early 40's Ice reefers were in use, and you had the colorful "billboard" reefers.

3581785 And the museum hasn't corrected it because?

3638236 what scale do you model? N, HO, American OO, S or O

3638869 HO (1:87) I believe it is the same as your OO
3638427 They have internal storage tanks for oil that are quite large. Plus, I think it preserves the history of the locomotive. I wonder if she still has remnants of that last fire in her firebox!

3638985 OO is slightly larger, OO is 4mm/ft. HO is 3.5mm/ft.

OO is actually quite complicated, as there are two sizes used

1:72 is used for model cars and plastic kits, and came before 1:76
1:76 is used for actually railway related stuff, and is the most used out of the two now a days.

generally unless you're a rivet counter you won't notice a difference between the two unless you get two of the same thing in the different scales, but then it's in terms of millimetres difference

3639188 OK, thanks for clearing that up. So across the pond HO is HO.

3639238 yep, you often find layouts at British exhibitions with American or European Ho layouts

On the contrary. The 2-6-6-6 was used to its full potential at its very slow, lumbering pace of around 30mph. Any faster and they became inefficient due to the fact they were compound articulateds. The Big Boy as well ass the challenger and N&W Class As were simple types, both sets of cylinders using fresh boiler steam meaning they could reach faster speeds without everything going out of wack.

3706159 Nope, the Allegheny's were simple articulateds. The only used the steam once. The N&W Class Y's were compounds, but to get the train moving, they could operate as simple articulateds for speeds under 10mph, IIRC.