A club member brings me interesting models for upgrade. This time, he brought me a very new British model and a very old American model.
My friend and fellow club member collects largely British models. This time, he had me upgrade a stout little 2-6-0 steam locomotive manufactured by UK Bachmann. It was made mostly well, but their use of the 21-pin decoder system annoyed me. These little steamers’ little tenders need room for a decoder, a speaker, and a capacitor. 21-pin decoders are thin but wide, and their connectors make their geometry taller than necessary. I removed that in lieu of a TSU-1100. Doing so left plenty of room for a capacitor. A speaker was already inconspicuously supplied within the bottom of the tender. With plentiful space, the hard wiring was a breeze!
These thin little power wipers bend and break easily. Flexing them back into shape takes care.Real coal pieces were glued to the tender upon receipt by my client, so my work bench was fifty percent covered with it.
My client brought me another model dating to 1975. It is a well-known Tyco Chattanooga, known for little quirks, engine mechanism problems, and general finickiness. It’s a reputation well earned!
These Chattanoogas are tender-driven rather than engine driven. The blocky motor draws power from the tender frame and the engine drivers.To improve electrical continuity, I added custom-formed axel wipers made from Kato N scale diesel truck wipers. There were two springs within the old, dilapidated smoke unit, and they were perfect for pressing the metal axel and wheel against the movable axel frame. These tenders have plentiful space for the PowerTorque pancake motor block.I installed a TCS KA5 in this model since I had ample space. The improved electrical continuity is still only so good, so the largest capacitor I have is appropriate.All that space was great for housing the decoder and capacitor. A metal screw connected a motor brush and spring to the frame, so I removed that and used UV hardening gel to replace the screw and keep the frame and armature mechanism plate together.
There was no working backlight in the tender from the manufacturer, so I melted a hole into the fake backlight to make room for an LED. That’s not bad for a fifty-one year old model!
For many railroad enthusiasts, the Union Pacific Big Boy represents the pinnacle of American steam locomotive design. Its sheer size, remarkable power, and modern-day return to service have made it a railroading icon. Yet the Big Boy did not appear in isolation. It was the culmination of more than two decades of engineering development, during which Union Pacific continually sought to move heavier freight trains over the steep grades of the American West with greater speed, efficiency, and reliability.
Beginning with the rugged Bull Moose in 1918, the innovative 9000 class in 1926, the versatile Challenger in 1936, and finally the legendary Big Boy in 1941, Union Pacific refined the art of heavy freight steam power into what many historians consider the highest achievement of the American steam era.
The Problem
Unlike many eastern railroads, Union Pacific crossed some of the most demanding terrain in the continental United States. Long grades across Wyoming’s Sherman Hill and Utah’s Wasatch Mountains challenged locomotives to haul increasingly heavy freight trains over difficult mountain districts while maintaining efficient schedules.
Each generation of locomotive was another attempt to solve the same fundamental question: how can increasingly heavier trains move faster over the mountains without increasing expense?
The answer evolved dramatically between 1918 and 1944.
The Bull Moose, The Greatgrandparent (1918–1924)
The nickname “Bull Moose” was affectionately given by Union Pacific crews to the railroad’s fleet of 2-8-8-0 articulated Mallet locomotives. Between 1918 and 1924, the American Locomotive Company (ALCO) built seventy-five examples for Union Pacific.
Designed specifically for mountain freight service, these locomotives possessed tremendous pulling power but sacrificed speed. Their primary purpose was to haul long freight trains over steep grades where brute force mattered far more than velocity.
Compound Articulation
The Bull Moose was originally built as a compound Mallet.
Instead of sending fresh boiler steam to all four cylinders simultaneously, steam first entered two smaller high-pressure cylinders before exhausting into two larger low-pressure cylinders. This arrangement extracted additional energy from the steam and improved fuel economy during slow-speed operation.
While efficient, compound operation made the locomotives mechanically complex and somewhat sluggish when accelerating. Acceleration may be only one part of a train’s trip, but it’s a very important part of time spent traveling. “Time is money” to all railroads, be they commercial freight, commercial passenger, or leisurely excursion railroads.
Rebuilding the Bull Moose
Beginning in the late 1930s, Union Pacific modernized much of the fleet.
Major improvements included:
Conversion from compound to simple-expansion cylinders
Larger 59-inch driving wheels
Feedwater heaters
Mechanical refinements throughout the locomotive
Conversion of many locomotives from coal to oil firing
Improved, more efficient application of power
These rebuilt locomotives’ significant upgrade in power application and efficiency made them valuable mountain freight engines through the late nineteen forties.
The “Nines” 9000 Class, A Completely Different Solution (1926–1930)
Rather than constructing an even larger articulated locomotive, Union Pacific engineers pursued a radically different approach known today simply as “the Nines”.
Between 1926 and 1930, ALCO produced eighty-eight 4-12-2 locomotives that remain the only largely successful production three-cylinder steam locomotives built for regular service in North America.
A Worthwhile Note: The 9000s were the most famous example of large, three-cylinder steam locomotives, but they were not the first. Their immediate predecessors are the ten 4-10-2 “Overland” 8000s built in 1925. The Overlands were experimental prototypes of a concept that paved the way for the Nines. They hauled heavy freight trains over the famous Overland Route in addition to the Overland Limited passenger train. The Overlands were overshadowed by the Nines relatively soon, having a service date range of about seventeen years before being converted to two-cylinder operation.
Three Cylinders Instead of Four
Unlike virtually every other large American steam locomotive, the 9000 included an additional inside cylinder located between the locomotive’s frames.
This third cylinder drove the second driving axle, producing smoother power delivery and reducing the stress placed upon the outside cylinders.
The design proved remarkably successful.
Although the Nines generated slightly less starting tractive effort than the rebuilt Bull Moose, it hauled nearly the same tonnage while maintaining speeds approaching 50 mph. Faster trains meant increased capacity because locomotives spent less time occupying valuable main-line track.
The trade-off was flexibility. With twelve coupled driving wheels mounted in a rigid frame, the Nines required exceptionally well-maintained track and generous curve radii.
The Challenger (1936–1944)
Combining Speed with Articulation
The Challenger represented one of the greatest advances in steam locomotive engineering in its time.
Instead of choosing between the flexibility of the Bull Moose and the speed of the Nines, Union Pacific engineers combined both strengths into a single locomotive.
The 4-6-6-4 Challenger was designed from the beginning as a simple articulated locomotive, eliminating the complicated compound steam system used by earlier Mallets.
This reduced maintenance while greatly improving high-speed performance.
A Freight Locomotive That Could Run Fast
Equipped with 69-inch drivers and operating at 255 pounds per square inch of boiler pressure, the Challenger comfortably hauled heavy freight between 50 and 70 mph.
For an articulated locomotive of its size, this was extraordinary.
Union Pacific eventually owned 105 Challengers, more than any railroad ever operated, making the design one of the most successful articulated freight locomotives in history.
The Big Boy (1941–1944)
The Mightiest Steam Freight Locomotive in the West
By the early 1940s, freight traffic continued to increase.
Union Pacific wanted a locomotive capable of hauling 3,600-ton freight trains over the Wasatch Mountains without helper locomotives.
ALCO answered with the now-famous 4-8-8-4 Big Boy.
Although visually similar to the Challenger, nearly every major component was enlarged.
Boiler pressure increased to 300 psi.
The locomotive weighed approximately 772,000 pounds by itself and more than 1.2 million pounds when coupled to its tender.
Starting tractive effort reached an astounding 135,375 pounds.
Despite its enormous size, the Big Boy remained surprisingly fast. In regular freight service it commonly operated at speeds between 45 and 70 mph, with credible reports suggesting somewhat higher speeds under exceptional circumstances.
Only twenty-five Big Boys were built, yet eight survive today. No. 4014 currently holds the distinction of being the world’s largest operating steam locomotive.
Union Pacific Heavy Freight Steam Chronology
1918: The first Bull Moose enters service, introducing large articulated freight power to Union Pacific.
1924: Construction of the Bull Moose fleet concludes.
1926: The first Nine-class locomotive is delivered, becoming the largest successful rigid-frame steam locomotive built in North America.
1930: Construction of the Nines concludes.
Late 1930s: Most Bull Moose are rebuilt from compound to simple articulated locomotives, receiving larger drivers and numerous mechanical improvements.
1936: The Challenger enters service and demonstrates that articulated locomotives can combine flexibility with sustained high-speed freight operation.
1941: The first Big Boy is delivered.
1944: Construction of both the Challenger and Big Boy concludes.
1947: Retirement of the Bull Moose fleet begins.
1953-1956: The Challenger and Nine fleets are gradually retired as diesel-electric locomotives assume their duties.
1959: The final Big Boys leave regular service.
11 August, 2016: Restoration of Big Boy 4014 begins.
1 May, 2019: The locomotive moved under its own steam for the first time since 1959 during test runs in Cheyenne.
4 May, 2019: Union Pacific formally unveiled the restored locomotive during a public ceremony in Cheyenne.
9 May, 2019: No. 4014 departed on its first public excursion, helping commemorate the 150th anniversary of the completion of the First Transcontinental Railroad at Promontory Summit, Utah. This is generally regarded as its official return to service.
Four Different Engineering Philosophies
One of the most fascinating aspects of these locomotives is that each solved the same operating problem in a different way.
The Bull Moose emphasized maximum pulling power. Efficiency and low-speed tractive effort were paramount, making it ideal for mountain grades but relatively slow.
The 9000 class pursued speed through an immense rigid frame and an innovative three-cylinder arrangement. It moved similar freight tonnage more quickly, increasing the railroad’s capacity without requiring additional track.
The Challenger united articulation with speed. It could negotiate mountain curves while hauling heavy freight at speeds previously reserved for rigid-frame locomotives.
The Big Boy refined the Challenger’s concept into its ultimate form. Rather than chasing higher top speeds, it focused on moving heavier trains over mountain grades without helper locomotives, pushing reciprocating steam technology to its practical limits.
Did You Know?
The Bull Moose Wasn’t Originally Called a Class
“Bull Moose” was a railroad nickname coined by Union Pacific crews rather than an official builder’s designation.
The 9000 Was Unique
The 9000 class remains the only successful production three-cylinder steam locomotive built for regular service in North America.
The Challenger Was Designed for Speed
Unlike earlier Mallets, the Challenger was designed from the outset as a high-speed articulated locomotive rather than being adapted from a slower freight design.
Eight Big Boys Survive
Of the twenty-five Big Boys constructed, eight escaped the scrapyard—an unusually high survival rate for large steam locomotives.
Legacy
Viewed together, these four locomotive classes illustrate one of the most remarkable engineering progressions in railroad history.
In just twenty-three years, Union Pacific advanced from the slow but immensely powerful Bull Moose to the Big Boy, a locomotive capable of hauling enormous freight trains over mountain grades at sustained main-line speeds.
Each generation built directly upon the lessons learned from its predecessor. The Bull Moose proved the value of articulation with heavy freight over mountainous terrain. The 9000 demonstrated that immense freight locomotives could also be fast. The Challenger successfully combined those ideas into one versatile design. Finally, the Big Boy refined that formula into what many historians consider the ultimate expression of American steam locomotive engineering.
Today, although only the Big Boy survives in significant numbers, the legacy of every one of these locomotive classes lives on. Together they transformed freight transportation across the American West and helped define the final golden age of steam.
Mulligan made me stop for luvins. I tried peeling away the female connector to directly access the ground and positive pins. That didn’t work. Soldering directly to the motherboard’s decoder connector base was far simpler.
BLI designed the resonating enclosure for its 8Ohm 2Watt speaker very well!
Below is some fun historical information. Skip down to THE FUN STUFF if you already know it!
Union Pacific’s Big Boy No. 4014 is the largest operating steam locomotive in the world and stands as a veritable visage of American railroading’s golden age. Built by the American Locomotive Company (ALCO) in November 1941, it was one of twenty-five “Big Boy” locomotives created at a critical moment in history, when the United States required unprecedented freight capacity to support wartime production and logistics during World War II. These locomotives played a vital role in hauling massive quantities of raw materials, fuel, and military supplies across the nation, particularly over the steep grades of the Wasatch Mountains between Utah and Wyoming, where their immense power proved indispensable.
Weighing more than 1.2 million pounds, or approximately 600 tons, with its tender, the 4-8-8-4 articulated locomotives represented the pinnacle of American steam engineering innovation. Big Boy No. 4014 is capable of approaching 6,290 drawbar horsepower at around 40 mph, with peak output estimates approaching 7,000 drawbar horsepower under ideal conditions. At the cylinders, its indicated horsepower has been estimated at roughly 8,000 to 8,150 horsepower. This immense power was paired with an exceptional tractive effort of over 135,000 pounds, allowing the locomotive to haul thousands of tons over steep grades without assistance. Its advanced design combined brute force with operational flexibility, showcasing the ingenuity and industrial strength that defined the era. The Big Boy class pushed the limits of size, power, and efficiency at a time when railroads were the backbone of the nation’s economy and war effort.
After retiring from regular service in 1961, No. 4014 spent more than fifty years on public display, serving as a monument to a transformative period in transportation history. Its return to the shops in 2013 marked the beginning of an ambitious restoration project, culminating in its triumphant return to operation in 2019. Today, Big Boy No. 4014 runs under its own steam, serving as a living testament to American engineering excellence and preserving the legacy of steam power. It’s history-make excursions allow America’s youth to witness firsthand one of the most significant achievements in railroad history and American intellectual prowess.
Following No. 4014’s tracks, other legendary steam locomotives are experiencing revitalization and resurrection efforts. Union Pacific’s Challenger No. 3985, a 4-6-6-4 articulated locomotive and close relative of the Big Boy, has undergone extensive rebuilding work with the goal of returning it to operation. While slightly smaller, the Challenger class was still immensely powerful, capable of producing roughly 5,800 to 6,000 drawbar horsepower and serving as a versatile high-speed freight and passenger locomotive. Meanwhile, the Pennsylvania Railroad’s T1 class—iconic 4-4-4-4 duplex locomotives known for their striking streamlined design—is being recreated from the ground up by the T1 Trust. The new-build T1 No. 5550 is projected to produce in excess of 6,500 indicated horsepower, potentially rivaling or exceeding the performance of many historic steam locomotives. Together, these efforts highlight a broader movement to preserve and revive the most powerful machines of the steam era, ensuring their stories and capabilities continue to inspire future generations.
America’s largest steam locomotives were each built with a distinct purpose, and their specifications highlight these differences.
The Big Boy was the brute-force specialist. Its monstrous weight, sixteen driving wheels, and roughly 135,000 pounds of starting tractive effort allowed it to move exceptionally heavy freight trains over Union Pacific’s mountain grades.
The Challenger traversed more versatile middle ground. It was smaller and lighter than the Big Boy, but it handled freight at relatively higher speeds. Challengers were also used on some passenger trains, something for which the Big Boy was not initially intended.
The T1 was built for true speed rather than maximum pulling force. Its 80-inch drivers, streamlined body, duplex drive, and approximately 6,500 indicated horsepower were intended for sustained high-speed passenger operation. It produced less starting tractive effort than either Union Pacific locomotive, but it could develop tremendous power once moving at speed.
Together, these three locomotives represent the pinnacle of American steam engineering, illustrating how designers pushed the limits of steam technology in different directions to meet specific operational demands. The Big Boy emphasized sheer tractive force and mass to conquer mountainous terrain with unprecedented freight loads, while the Challenger balanced power and speed to handle a wider range of duties efficiently. In contrast, the T1 prioritized aerodynamic design and high-speed performance by sacrificing raw pulling power to excel in fast passenger service. This clear contrast in design goals—maximum power, operational flexibility, and sustained speed—demonstrates the remarkable adaptability and ingenuity of American locomotive engineering at its peak.
THE FUN STUFF
Girard held a special festival for No. 4014’s visit, and part of that meant cordoning off many roads and whole city blocks. Certain spaces like fields, grassy areas, and a school parking lot were used for specific shuttle waypoints. THAT was a phenomenal idea!!! It offered a safe route to and from the Big Boy site, mitigated traffic of an estimated 1,000 people, and it offered an air conditioned ride on a hot day. There were also smaller transportation modes available, such as golf carts and moderately sized utility vehicles.
Tom and I were early enough to be the first passengers of the day!We found an excellent spot at the base of this grain elevator. There was a dilapidated trailer made with really thick wooden slabs that was heavy enough to not tip with my full body weight at the high end. It provided an nice view above people’s heads and the security fence.Notice in the far background that there are people dangerously close to the tracks. There is a twenty-five foot minimum mandated distance set for people’s safety. There is no winning in contact sports with trains.A few trains passed through Girard before the Big Boy’s arrival. Some passed quickly to remain on schedule while others slowed down to bask in the spectators’ revelry.
An high-speed south-bound Amtrak passenger train ran through well ahead of the Big Boy.
A slower north-bound Amtrak ran through. This is the one moving slow enough for a photograph.
This freight train pulled up to Girard well before the fast Amtrak whizzed by, but it stopped and waited quite a while before proceeding. I can only imagine the potential logistical nightmare excursions pose. Any disturbance in a schedule will suck, but trying to amend something related to a GARGANTUAN, articulated steam locomotive multiple states away from its home shop facility is unthinkable. Years ago, a friend and I rode an excursion on the Cumbres and Toltec narrow gauge railroad in New Mexico. While pulling through a bend in a canyon, it rolled upon some rocks across the track. The locomotive was damaged in such a way that it reversed off the rocks and mechanically stuck in reverse. Another locomotive was sent from the opinion direction to help, and the two crews managed to repair the steam locomotive. Our little three-hour one-way trip became five and a half courtesy of those hidden rocks. That occurred on a regular excursion route with shops less than twenty miles away at either end of the line. We were lucky.
She was forty-six minutes late, but she arrived to much myrth and splendor!
Who doesn’t love that whistle!?
Away she goes, on towards her western home!
Just as the Big Boy departed, a hopperl train came through.
I overheated and had to have my friend Tom drive part of the way home. That gave me a chance to rail fan on the road! We happened upon this mixed freight train heading east to Taylorville, Illinois.
The proximity of the road and rails diverged briefly, so we lost and found the same train passing into Taylorville.
Tom and I had a great day out with the Big Boy. I had never met Tom until that day. He follows the Crawford County Model Railroaders on Facebook, and he responded when I offered to carpool to Girard with club members. He lived an hour north of Charleston, Illinois, and I lived an hour south of Charleston. We met in the Charleston Walmart parking lot and took my truck to Girard. I’m glad we got along well for that two and a quarter hour, one-way drive!
