4-8-8-4 "Big Boy" Locomotives

During the late 1930s, the Union Pacific often used helpers to move trains from Ogden to Wahsatch. The UP wanted to simplify this move so they asked their "Department of Research and Mechanical Standards" (DoRMS) to design a locomotive that could pull a 3600 ton train unassisted over the 1.14% grade of the Wahsatch.

The designers determined that to pull a 3600 ton train, a tractive effort of 135,000 lbs would be needed. Assuming a factor of adhesion of 4.0, the weight on drivers would have to be 4.0 * 135,000 = 540,000 lbs. Given an axle loading of 67,500 lbs each, this would require 8 drivers or an x-8-8-x wheel arrangement. The designers agreed upon the 4-8-8-4 design. Next, the horsepower and cylinder sizes were computed based on 300 psi boiler pressure. Although they weren't planning to pull these freight trains at 80 MPH, the DoRMS designed them for 80 MPH in order to have a sufficient factor of safety built into the design. What resulted is considered by many to be the most successful articulated steam locomotive ever built. 4000 was delivered to Omaha at 6PM, September 5, 1941.

The 25 Big Boys were built in two groups. The first group, called "class 1", were built starting in 1941. They were numbered 4000-4019. The second group, "class 2", were built in 1944. They were numbered 4020-4024. The last revenue freight pulled by a Big Boy was in July of 1959. Most were retired in 1961. The last one was retired in July of 1962. As late as September, 1962, there were still four operational Big Boys at Green River, WY.

The total mileage of each of the Big Boys from class 1 were roughly the same -- 1,000,000 miles. 4016 had the lowest mileage -- 1,016,124. 4006 had the highest mileage -- 1,064,625. Of the second group, 4024 had the highest mileage -- 811,956.


Big Boy Facts and Trivia

A Big Boy is Not a Mallet

Periodically, I hear the Big Boy referred to as a "Mallet". Technically, this is not true. Anatole Mallet designed his steam locomotive that 1) was articulated, and 2) used compound expansion (high and low pressure cylinders). The Big Boys, as well as many other articulated steam locomotives, used simple expansion, and thus, are not true mallets.

What do those cab markings mean?

Big Boy Cab Markings UP: Union Pacific
4002: Locomotive number
4-8-8-4: Wheel arrangement

NOTE: Some used "4-8-8-4 1" and "4-8-8-4 2" to distinguish between the first and second classes of Big Boys.

68: 68 inch drivers
23 3/4 - 23 3/4: Cylinder diameters (front and rear)
32: Piston stroke
540: 540,000 pounds of weight on drivers
MB: MB type stoker

Are Big Boys Really the Largest Steam Locomotive?

Books and magazines will often state that the Big Boy was the largest steam locomotive ever built. When steam locomotives are compared, many different quantities can be considered. For example, weight, length, horsepower, and tractive effort are all characteristics of how "large" a steam locomotive is. In each of the above categories, a locomotive "larger" than a Big Boy can be found.

If you were to ignore all of the unsuccessful and experimental locomotives, then look at the overall ratings of the remaining steam locomotives in the above categories, it would become clear that the Big Boys (along with the N&W Y6 and A, DM&IR M, and perhaps the C&O H-8 locomotives) were the "largest" among all successful steam locomotives.

What is the Sharpest Curve a Big Boy can Negotiate?

The sharpest curve the Big Boys could negotiate was a 20 degree curve. In HO scale, this would be a 40 inch radius curve.

Will a Big Boy Ever be Restored to Operating Condition?

This question comes up frequently. Many used to laugh at the question because it seemed so ridiculous. However, when the news of the proposed restoration of 4018 for a movie was announced back in 1998, some of us waited hoping it was true. As it turned out, the news about restoring 4018 was only a proposal in its infancy and nothing ever materialized of it.

If one was to restore a Big Boy it would seem to make sense to start with the Big Boy that is in the best condition. At one time, this would have been 4023, currently at Kenefick Park, Omaha, NE. During the end of their careers both Challenger 3985 and Big Boy 4023 were rebuilt and placed in the Cheyenne UP roundhouse. However, 4023 was later placed on display in Omaha and the weather and environment has taken its toll on 4023. Currently, 4014, displayed in Pomona, CA has been kept in immaculate condition by the Southern California Chapter of the Railway & Locomotive Historical Society.

According to many sources, the UP is really not interested in running a coal-fired locomotive on their road any longer (the 3985 (4-6-6-4) was converted to oil in the late 1980's). Naturally, the next question one asks is "why not convert a Big Boy to burn oil?". This was tried back in the 1940s or 1950s on 4005 with a single burner, without success. It has been said that it is not feasible to fire a Big Boy with oil due to the nature of the firebox (which was designed for burning semi-bituminous coal from southern Wyoming) and boiler capacity. However, 3985 was converted to burn oil and its firebox is not all that different from that of the Big Boy's.

Steve Lee (head of UP's steam program) has also stated that it wouldn't make much sense for UP to restore a Big Boy, as there are only two places on the entire system that are large enough to turn a Big Boy, and those places are only a few miles apart. However, the Challenger is often turned using wyes which could also, almost certainly, handle a Big Boy.

Despite the obstacles of restoring and operating a Big Boy, with enough money, anything is possible.

News Flash

In December of 2012 discussion about the possibility of restoring a Big Boy to operating condition emerged. At that time many people who heard about this were hopeful but those who have heard of plans like this come and go before were skeptical. From December 2012 to July 2013 very little, if any, new information was available. Then, on July 23, 2013 the announcement was made that ownership of 4014 was to be transferred from the Southern California Chapter - Railway & Locomotive Historical Society to the Union Pacific for the purpose of fully restoring the locomotive.

More Information:

USA and Canadian Railroads that used 4-8-8-4 "Big Boy" Locomotives

Surviving Examples of 4-8-8-4 "Big Boy" Locomotives

No.ClassF.M. WhyteGaugeRailroad LineLocationStatusBuilder InformationNotes
4005488414-8-8-44'-8½"UP Forney Transportation Museum, Denver, COdisplayALCO (Schenectady) #69576, 10/1941
4006488414-8-8-44'-8½"UP Museum of Transportation, St. Louis, MOdisplayALCO (Schenectady) #69577, 10/1941
4023488424-8-8-44'-8½"UP Lauritzen Gardens, Omaha, NEdisplayALCO (Schenectady) #72780, 11/1944
4012488414-8-8-44'-8½"UP Steamtown National Historic Site, Scranton, PAdisplayALCO (Schenectady) #69583, 11/1941
4018488414-8-8-44'-8½"UP Museum of the American Railroad, Frisco, TXdisplayALCO (Schenectady) #69589, 01/1942
4017488414-8-8-44'-8½"UP National Railroad Museum, Green Bay, WIdisplayALCO (Schenectady) #69588, 01/1942
4014488414-8-8-44'-8½"UP UP engine house, Cheyenne, WYrestorationALCO (Schenectady) #69585, 12/1941To be restored by the UP From Pomona, CA
4004488414-8-8-44'-8½"UP US 30, Holliday Park, Cheyenne, WYdisplayALCO (Schenectady) #69575, 09/1941

Surviving Big Boy Notes

  1. 4004: Holliday Park, Cheyenne, WY

    Big Boy 4004 Big Boy 4004 4004 is displayed in Holliday Park on US 30 in Cheyenne. It was placed there during the summer of 1963.

    One viewer wrote to me stating that in 1973/74 he thought that there was a Big Boy displayed near the Wyoming/Colorado border along I25. It could not have been 4004 (because 4004 was placed in Holliday Park in 1963) and there were no other Big Boys, or any locomotive for that matter, that would have been displayed in this area. If anyone does know of a locomotive that was once displayed in this area, please let me know.

    A 1985 rainstorm caused Holliday Park to flood so that water reached the top of 4004's drivers! [Photo] In 2001 there had been talk about moving 4004 from Holliday Park to the depot about 9 blocks away but this was only a rumor. In 2005, 4004 received some cosmetic work including a new paint job and lettering and new windows which greatly improved the locomotive's appearance. While the external appearance of 4004 is good, the cab interior, at least used to be a mess. Most of the controls had been removed by either wrench or torch, the firebox door is welded shut, and the seats are either gone or have deteriorated to springs.

    Cheyenne is also the home of UP's steam program where both Challenger 3985 and Northern 844 (and a couple others) are housed. The Elesco cold water turbine pump and a Nathon water injector were removed from 4004 for use on Challenger 3985.

    Photos and Information

  2. 4005: Forney Transportation Museum, Denver, CO

    Big Boy 4005 At the end of its career, 4005 had been partially dismantled in preparation for shipment to Argentina. However, the recipients in Argentina were unable raise enough money so 4005 stayed in the US. 4005 was also the Big Boy which was unsuccessfully converted to burning oil (and then converted back to burning coal). Notice the red firebox on this Big Boy. I don't know why it was painted red but I have heard that since my visit, 4005 has been repainted. Despite the new paint job, 4005 is probably in fair to poor condition.

    4005 was displayed outside at the Forney Transportation Museum in Denver for many years. In January 1999, it was temporarily moved next to the Platte River at 15th Street. Later is was moved to 4303 Brighton Blvd. It finally made it back to a location inside the Forney Transportation Museum in 20??. During these moves, to prevent major damage to the cylinder bores, 4005's main rods were removed (rather than cut as is sometimes done) prior to the move. Also, a substantial amount of work was required to repair some critical damage to the trailing truck centering devices. When the engine was originally placed in the Forney Museum someone used a torch to cut off parts of the casting that control the limits of lateral movement of the trailer. These had to be renewed in order for the engine to be able to negotiate curves during its moves.

    The cost of relocating UP 4005, C&NW 444 (a 4-6-0), two 85' passenger cars, a UP derrick and rotary snow plow and a few old, wood passenger cars in various states of disrepair to their temporary location was $600,000. Jack Forney deserves special credit for spending a lot of money and time to preserve and relocate a large amount of historic RR equipment.

    Photos and Information

  3. 4006: Museum of Transportation, St. Louis, MO

    4006 was painted in 1995 and is displayed directly ahead of UP Centennial 6944. Stairs provide access to the cab where most controls are identified.

    Photos and Information

  4. 4012: Steamtown National Historic Site, Scranton, PA

    Big Boy 4012 For many years, 4012 was displayed in the front of the Lackawanna Station Hotel in downtown Scranton. In 1993 after bridges between the Hotel and Steamtown were replaced, 4012 was moved into the yard at Steamtown. Contrary to a rumor once posted on rec.railroad, Steamtown has no plans to partially restore 4012 to working order.

    Photos and Information

  5. 4014: UP Engine House, Cheyenne, WY (Previously at RailGiants Train Museum, Los Angeles County Fairplex, Pomona, CA)

    Big Boy 4014 4014 was donated to the Southern California Chapter of the Railway & Locomotive Historical Society in January, 1962. In 1989/1990 when the chapter was moving its collection from the original display area behind the horse barns to the new location adjacent to the main parking lot, 4014 gave the movers a surprise. During the move, 4014 moved so easy that it got away from them and ran into the tender of AT&SF Hudson 3450. They left things that way over night while planning on repositioning it the next day. When they arrived the next morning they found 3450 had been pushed partly into the dirt after slowly rolling off the end of the temporary track sections they used for the move.

    The original builder plate was stolen before 4014's move to California. A new, correct one will eventually be made.

    1997: Of all the Big Boys I have seen, 4014 appears to be in the best condition. The cab interior gives the impression that all it needs is coal and a fire and it will come to life. When I visited in the mid 90s one of her pistons was removed undergoing some restoration and maintenance work.

    A 2001 report indicated that 4014 almost looked like new. Her paint was in excellent condition and one could smell the lubricants used to maintain her. Her smokebox wasn't just painted. It appeared to have the oil/graphite type of finish typical of "live" steam locomotives. She had been given green marker lights in the front and red ones to the side. Her cab needed some painting but otherwise appeared to be in operable condition. There were plans to repair her whistle and hook it up to an air compressor so visitors could blow it.

    The boiler jacketing has been removed to prevent moisture entrapment. It is covered with a fresh coat of paint. Her state of preservation is such that her bearings are well lubricated.

    4014 was the star in a soda pop commercial where her firebox was lined with foil and soda cans and lit up. Her firebox has also been stuffed with other non-fuel items, namely: school children. The curator stuffed 32 of them in there!

    4014 was maintained by two gentlemen that obviously love her. I have been told that they had the bell and whistle working on 150 psi of air.

    A 2010 report mentioned that the boiler is again in need of paint.

    A 2012 Trains Article about the possible restoration of this Big Boy.

    Latest restoration updates

    Photos and Information

  6. 4017: National Railroad Museum, Green Bay, WI

    Big Boy 4017 4017 is in good to very good cosmetic shape. She was sand blasted and repainted in 1995. The firebox is electrically lighted and viewable by the public.

    In the summer of 2000 the museum began construction of a new "display hall" to provide shelter the 4017 (and other locomotives). 4017 was completely repainted in 2000 including a color match to reproduce the effect of the waste oil/graphite mix used to paint the Big Boy's fire and smoke boxes during normal operation.

    By 2002 4017 had been moved into this new display hall. Visitors can enter both the cab and tender.

    Photos and Information

  7. 4018: Museum of the American Railroad, Dallas, TX

    2000 Photo Wes Barris Photo courtesy Kennedy How Of all the Big Boys I have seen, from the outside, 4018 appears to be in the worst condition. The main reason I say this is because when I saw it, I noticed that the piston rods had been severed by a cutting torch (see photo). This was done when 4018 was moved to the museum back in the late 60s. Evidently, 4018 was being moved from some undisclosed location on a UP line to the museum when the pistons seized. Pressure from the the UP resulted in the cutting of the rods to get 4018 moving again. Also, the boiler jacketing and much of the piping looked to be in pretty rough shape. I saw moss growing through holes in the boiler jacketing which implied that a substantial amount of moisture was trapped against the boiler (see photo). However, the fire tubes and firebox are apparently in relatively good shape and most (if not all) of the appliances inside of the cab are intact (see photo). Because of how 4018 is parked (between two other locomotives) it is difficult to get a good photograph of her.

    In April, 1998 it was announced that 4018 will be restored to operating condition for use in a movie titled Big Boy. During my visit to the Age of Steam Railroad Museum (as it was named back then) in November 2000, I was told that it had been roughly a year since anyone has heard from the person who proposed to use 4018 in a movie. From what I've heard, the cost of restoring this big boy was going to be between $700,000 and $1,000,000. Then, the financing for this proposed movie fell through. As a result, 4018 continues to be displayed at this museum.

    In 2007 4018 was repainted in its original scheme.

    Photos and Information

  8. 4023: Lauritzen Gardens, Omaha, NE

    Big Boy 4023 Photograph courtesy Dave Smith During the end of their careers (1956, I believe) both Challenger 3985 and Big Boy 4023 were given general overhauls so that they could continue to run for a few more years. In 1957, they were placed in storage in the Cheyenne UP roundhouse. However, 4023 was later put on display in Kenefick Park (along with Centennial 6900) in Omaha and the weather and environment has taken its toll on 4023.

    UP Round House Here is a rare photo (from Twilight of Steam Locomotives by Ron Ziel) of both 3985 and 4023 taken sometime after they were overhauled, repainted, retired, and stored in the Cheyenne roundhouse. I have been told that it was actually taken in the early 1960s. 3985 and 4023 were kept inside the Cheyenne roundhouse until late 1974. At that time, 3985 was placed on display outside the Cheyenne depot, and 4023 was placed on display outside the UP's Omaha shops until they closed sometime in the late 1980s. 4023 was then moved to Kenefick park where it sat for many years next to Centennial DDA40X 6900.

    The city of Omaha recently decided to re-design the riverfront area including the old UP shops, local industries, and Kenefick park into a new convention center. 4023 was to be placed on display at the convention center site after construction was completed. However, a change in the convention center plans no longer include the display of 4023 and the DDA40X. The locomotives had been temporarily moved to the Durham Western Heritage Museum in downtown Omaha. In March of 2005, 4023 was moved to a location near the Lauritzen Gardens. 4023 is in good shape. The paint looks great and all the missing parts (headlight etc.) have been replaced.

    Photos and Information

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