Big Boy 4014 is 133 feet long, weighs about 1.2 million pounds and runs at 300 psi. Here is what the specifications actually mean.
Numbers on a spec sheet only mean something if you can picture them. Here is what each of Big Boy 4014's main specifications means, using Union Pacific's published figures.
Size and Weight
- Length: engine and tender together measure 132 ft 9⅛ in, about 133 feet. The engine alone is 72 ft 5½ in.
- Weight: about 1.2 million pounds with the tender loaded. The engine alone is 762,000 lb and the loaded tender is 427,500 lb.
- Weight on the rails: 540,000 lb sits on the driving wheels, 97,000 lb on the leading wheels and 125,000 lb on the trailing wheels.
Power
- Boiler pressure: 300 psi, in a boiler 106 9/16 inches across.
- Cylinders: four of them, each 23¾ in wide with a 32 in stroke, per Union Pacific's fact sheet. Steamlocomotive.com reports that the cylinders were bored out to 24 in during restoration, raising tractive effort to about 138,240 lb.
- Tractive effort: 135,375 lb as built. This is the pulling force at the wheels.
- Horsepower: RailGiants cites a maximum of about 6,290 hp at 35 mph.
- Driving wheels: 68 in tall, 16 of them, in two groups of eight. See Why Big Boy Has a 4-8-8-4 Wheel Arrangement.
Fire and Water
- Grate area: 150 square feet. The firebox is 235 1/32 in long and 96 3/16 in wide.
- Water: the 14-wheel tender holds 25,000 gallons.
- Fuel: 56,000 lb of coal when it ran from 1941 to 1961, and No. 5 fuel oil since 2019.
Speed
RailGiants lists a top speed of 70 mph at retirement. Big Boys were built for heavy freight, not speed, so the point was moving big trains steadily up mountain grades.
What It Means
All of this adds up to the original design goal: pull a 3,600-ton train over Sherman Hill without a helper. For the larger story, read the The Complete Guide to Union Pacific Big Boy 4014 or the Big Boy 4014 History Timeline.
Want to wear the numbers? Check the Big Boy 4014 Shirts & Merch collection.
Shop Big Boy Gear
Love the engine? Wear it. Browse the Big Boy Coast to Coast Tour Commemorative Collection, the full Big Boy 4014 Shirts & Merch collection, or more railfan gear for the railroad lovers in your life. Every design is made by Broken Knuckle Apparel, a veteran-owned small business.
Keep Reading in the Big Boy 4014 Knowledge Hub
- Why Big Boy Has a 4-8-8-4 Wheel Arrangement
- Big Boy 4014 History Timeline
- 4014 vs 4012: Two Big Boys, Two Very Different Lives
- Big Boy Restoration History
- Railroad Terminology Glossary
Start with the complete guide to Big Boy 4014 for the full overview.