Union Pacific 4-8-8-4 "Big Boy" Locomotives in the USA

Class Details by Steve Llanso of Sweat House Media

Class Big Boy (4884-1) (Locobase 346)

Data from tables and diagrams in 1947 Locomotive Cyclopedia and UP 11 - 1946 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Many thanks to Kenneth Mileski for his 11 May 2016 email suggesting that Locobase's entry include information on 4014's restoration.) Works numbers were 69571-69575 in September 1941, 69576-69581 in October, 69582-69583 in November, 69584-69587 in December, 69588-69590 in January 1942.

Union Pacific senior manager of Heritage Operations Ed Dickens Jr. said in 2016 that the 4-8-8-4 series originally was to have been called (Wasatchö. After a never-identified UP worker wrote "Big Boy" on one of the cylinders, that nickname stuck.

Firebox heating surface included 111 sq ft (10.3 sq m) in seven inverted-T shape circulators and a combustion chamber extending 9 ft 3 in (2.8 m) forward of the ashpan. One of the heaviest engines in the world, the 25 "Big Boys" were the largest steam engines ever built for regular service. The last five delivered in 1944 were fitted with Type A superheaters; see Locobase 13026 for an analysis of why the change was made.

The Big Boys carried almost 70,000 lb (31,752 kg) more on its relatively tall drivers than did any other engine of comparable driver size. (The DM&IR's M3 2-8-8-4 engines -- Locobase 2405 -- had a higher weight on drivers, but had 63-inch/1,600 mm drivers.) Each one cost $265,000 when delivered.

These engines could maintain 70 mph (113 km/h) and rode quite steadily; see Locobase 338 for a description of the revised bearing design that permitted smooth riding at such speeds.. (The four pistons evacuated 22,700 cu ft/642.8 cu m of steam per minute at that speed.) On the other hand, Farrington (1976) claims they were hard to fire and thought a feedwater heater should have been preferred to the exhaust steam injector they carried.

Over a ruling grade of 1.14% the 4-8-8-4s could move 4,000 tons (3,636 tonnes) of freight at 20-25 mph (32-40.25 km/h). When the ruling grade between Ogden, Utah and Green River, Wyoming (176 miles/283 km) was reduced to 0.82%, the tonnage rating climbed to 5,360 tons (4,873 tonnes). At 45 mph (72.5 km/h), these engines developed 6,000 drawbar horsepower (4,476 kW). Among their many abilities was the flexibility to move around curves of 20 deg.

Also, the online encyclopedia http://www.answers.com/topic/union-pacific-big-boy (visited 14 July 2005) notes approvingly: "They did sterling service in the Second World War, especially since they proved so easy to fire that even a novice could do a fair job. Since many men who were unsuited to combat service were instead drafted into railroad service to replace crewmen who joined up, this proved essential."

See the trainorders.com forum thread that began 1/05/13 (http://www.trainorders.com/discussion/read.php?10,2959319) when KeyRouteKen commented on a recent documentary: "One of the guys talked about shoveling 27 tons of coal "by hand". Stoker must have been inoperable. Then he said they dropped down one time to 165 lbs of steam so they threw some creosoted pieces of crossties in the firebox to raise steam again. That was funny.

"And the best story was the guy who would open the firebox door and hold his shovel there to make a vent. Great, except when the hogger pulled back on the throttle, and the entire shovel was sucked into the firebox ! (grin!) "

Bob3985 replied:"The fireman who hand fired the Big Boy was Dillard Hill and they indeed had broken the stoker auger and could not auto deliver the coal to the firebox so they set their train out and made a run for the Laramie roundhouse keeping the steam up by hand."

Hotwater added:"... hand firing any locomotive equipped with a stoker, it really isn't THAT big of a deal. Just because the stoker auger doesn't work, does NOT mean that the steam distributing table doesn't function. All that is needed is for one or two men (Fireman & Headend Brakeman) to continuously shovel the coal onto the distributing table, and the steam jets will blow the coal to the necessary portions of the firebox. I speak from experience! It works on any steam locomotive equipped with a stoker."

4005 was converted to oil-firing for trials in 1945. Within a year, she was converted back to coal firing and no other Big Boys were converted. According to Chris Hohl, 4019 was fitted with smoke deflectors for tests in 1944-1945; no other members of the class were converted.

Drawing from William Kratville's book Big Boy, Nick Chillianis posted information about tests conducted 3 April 1943 on the Wasatch grade. Pushed at a rate of 9,980 US gallons (37,434 litres) of water and 9.66 tons (8.8 tonnes) of coal consumed per hour, engine #4016 produced 7,157 hp (5,339 kW) at the cylinders while moving 3,883 tons (3,530 tonnes) of train at 41.1 mph/66 km/h (drawbar hp was 6,290.) Other engines in the test produced 5,800 dbhp (4,327 kW) under similar conditions. See http://www.chaski.com/wwwboard/railfan/messages/3993.htm (12 Nov 1998, 8:46 AM).

At Ken Mileski's suggestion, Locobase checked up on 4014's restoration to service. In July 2013, the Union Pacific struck an agreement with the Southern California Chapter of the Railway & Locomotive Historical Society in Pomona, Calif to regain ownership of the 4014, which had been on display at the Rail Giants Train Museum since 8 January 1962. According to the UP, 4014 had run 1,031,205 miles in less than 18 years of service before its final revenue run on 21 July 1959. (That computes to a daily average of 160 miles for every calendar day.)

In exchange, UP transferred title of UP 6-axle diesel SD-40-2 #3105, a boxcar, and a caboose.

After months of careful assessment and preparation, four UP diesels moved the 4014 onto the national rail network on 26 January 2014. Ten freight cars provided additional braking power. Its first stop was Colton, CA, where it remained until its 1,300 mile (2,093 km) journey to Cheyenne, WY. That trip ended on 8 May 2014 with the 4014's safe arrival.

An initial estimate of 3-5 years for the restoration was later revised to 5-7 in part because the steam shop at Cheyenne had to be substantially modified to accommodate 4014. In addition, many systems, such as the entire front engine, were removed to allow better access during their reconstruction. One significant change will be the conversion to oil fuel (#5 fuel oil) from coal burning.

At just under 350 tons (316.3 tonnes), the 4014 is the largest wheeled restoration project ever undertaken.

Class Big Boy (4884-2) (Locobase 13026)

Data from UP 11 - 1946 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. Works numbers were 72777-72781 in November 1944.

Locobase 346 describes the first twenty of these Big Boys. This later quintet is usually described as reflecting the wartime limitations of certain metals, which required the builder to substitute heavier steel components. Even so, their engine weights were still lower than the maximum weights believed to have afflicted the C & O's 2-6-6-6 H-6 Allegheny class (Locobase 304). Firebox heating surface included 111 sq ft (10.3 sq m) in seven inverted-T shape circulators and a combustion chamber extending 9 ft 3 in (2.8 m) forward of the ashpan.

What is not usually mentioned is the change in boiler heating surface area and the substitution of a Type A superheater for the earlier group's Type E. John E. Rimmasch of

Wasatch Railroad Contractors contributed to a Trainorders forum discussion with comments that shed light on the reason for the change (http://www.trainorders.com/discussion/read.php?10,2474974):

On May 25, 2011, Rimmasch lays out the conditions that most likely dictated the change: "On the UP between 1941 and the end of steam, it was not uncommon to see super power get new tubes annually or even every six months. This was due in large to a number of conditions. A.) The water in Utah and Wyoming was hard enough that the flue bundle would clog up and tubes would burn quickly. B.) The UP Super Power was high pressure steam, which means we had a lot more heat. 800's, 300 psi, Big Boy's 300 psi and Challengers 280 psi. C.) The length of the tubes in the 800s, 3900s and 4000 was nearly the maximum allowable tube length for any locomotive (respectively 20-22 feet [6.1-6.7 m] long). It was found that when tube lengths near or surpass 18 feet long [5.5 m] , they had more of a tendency to bounce and tear apart. The stretching effect on these long tubes precluded many of them from being re-used.

"In the case of the UP, when you combine all three symptoms above, you end up having to change tubes more often ... [R]ather than lose a locomotive on tube failure, the UP (and other lines) found it cheaper and better to simply change them more frequently. ...A Big Boy could get new tubes in less than 36 hours."

In a later post, Rimmasch argues that Alco used a Type E superheater, which was harder to maintain because of its more complex steam path, to cover its bets: "I assume that the Big Boy originally had type E's with an increased heating surface area as ALCO was unsure if they had produced enough heating surface area to support the bore and stroke (multiplied by 4) and, after delivery quickly found that they had enough steaming capacity that the locomotive did not require type E's and was therefore reduced to type A's."

Rimmasch implies that the change to Type A superheaters came during the production of the first twenty locomotives, but the 1946 diagrams show only that the 4884-1s had Type E and the 4884-2s had Type As.

Like the earlier batch, these engines served the UP into the 1960s before all of them were retired in 1962--4021 in January, 4022 in February, and 4020, 4023-4024 in July.

Principal Dimensions by Steve Llanso of Sweat House Media
ClassBig Boy (4884-1)Big Boy (4884-2)
Locobase ID346 13,026
RailroadUnion Pacific (UP)Union Pacific (UP)
Number in Class205
Road Numbers4000-40194020-4024
Number Built205
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)18.75 / 5.7118.75 / 5.71
Engine Wheelbase (ft / m)72.45 / 22.0872.46 / 22.09
Ratio of driving wheelbase to overall engine wheebase 0.26 0.26
Overall Wheelbase (engine & tender) (ft / m)117.58 / 35.84117.58 / 35.84
Axle Loading (Maximum Weight per Axle) (lbs / kg)67,800 / 30,75467,800 / 30,754
Weight on Drivers (lbs / kg)540,000 / 244,940545,200 / 247,299
Engine Weight (lbs / kg)762,000 / 345,638772,250 / 350,287
Tender Loaded Weight (lbs / kg)427,500 / 193,911436,500 / 197,993
Total Engine and Tender Weight (lbs / kg)1,189,500 / 539,5491,208,750 / 548,280
Tender Water Capacity (gals / ML)24,000 / 90.9125,000 / 94.70
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)28 / 25.5028 / 25.50
Minimum weight of rail (calculated) (lb/yd / kg/m)113 / 56.50114 / 57
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)68 / 172768 / 1727
Boiler Pressure (psi / kPa)300 / 20.70300 / 20.70
High Pressure Cylinders (dia x stroke) (in / mm)23.75" x 32" / 603x813 (4)23.75" x 32" / 603x813 (4)
Tractive Effort (lbs / kg)135,375 / 61405.14135,375 / 61405.14
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.99 4.03
Heating Ability
Firebox Area (sq ft / m2)704 / 65.43720 / 66.91
Grate Area (sq ft / m2)150.30 / 13.97150 / 13.94
Evaporative Heating Surface (sq ft / m2)5889 / 547.305755 / 534.85
Superheating Surface (sq ft / m2)2466 / 229.182043 / 189.87
Combined Heating Surface (sq ft / m2)8355 / 776.487798 / 724.72
Evaporative Heating Surface/Cylinder Volume179.46175.37
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation45,09045,000
Same as above plus superheater percentage58,61756,700
Same as above but substitute firebox area for grate area274,560272,160
Power L132,74328,743
Power MT1069.42929.82