You have 7 views remaining.

Home / Train Basics / ABCs Of Railroading / How a Big Boy works

How a Big Boy works

By | September 6, 2018

Get our weekly newsletter delivered to your inbox

Email Newsletter

Get the newest photos, videos, stories and more.

Where does the fire burn? Where does the water boil? Where does it travel? What are all those pipes about? Our simplified drawing of how a Big Boy works shows how this king of the rails made and used steam to pull long freight trains up to 70 mph in Wyoming and Utah from 1941 to 1959.

19 thoughts on “How a Big Boy works

  1. It was built to burn low grade western coal, what we in Virginia call dirt with an attitude. All that magnificent grade area will seem wasted burning oil. I had heard that previous attempts at that conversion had failed. I would like to see an article about the details of what was done this time.

  2. When I visited the Cheyenne Steam Shop last year I asked Ed about the conversion to oil and he said it will not be a problem converting to oil. When you think about it, there is no practical way to use coal due to the amount that Big Boy burns per mile and no longer having coaling stations on the routes.

  3. It was not a failure so much as impractical. Now that UP has had such success converting the 844 and the 3985 to oil plus the availability of the computer technology we have today I am sure the results for 4014 will be much better than the early experiments.

  4. All those moving parts must have been a maintenance nightmare. It is something of a miracle that they could all move so fast and stay together as to get it moving up to,70mph.

  5. The diagram appears to show the word “petticoats” with arrows pointing to the multiple jet blast pipes.
    My understanding is that the petticoat is the curved extension of the stack inside the smokebox. I may have misread the diagram, but it sdidn’t look quite right to me…

  6. With the coal to oil conversion a significant portion of the long firebox will be walled off. Coal burners needed a larger firebox for the coal fire to produce the proper amount of heat. Oil burns hotter than coal so a smaller firebox is used. Oil fired locomotives needed firebox replacement after about 10 years of service while a coal burner would require firebox replacement in about 15 years.

  7. Big Boy 4005 was oil fired from 1946-1948, due to a coal strike. The firebox had issues, and the infrastructure from Cheyenne to Ogden wasn’t set up for oil.

  8. Mr. Humphries, by “Mallet steam cycle,” do you mean a compound locomotive? The Big Boy is not a compound engine; it uses high pressure steam in all the cylinders.

  9. would have really been neat if the downloaded jpg had been animated; showing the interaction between all of the moving parts in both forward and reverse directions. Maybe next month. 🙂

  10. a post on another page asked the Big Boy would go to Atlanta. A recent article by Trains (cannot remember the source) talked about the major problems when on of their steam engines went east on CSX. With all the problems I suspect that the Big Boy will not leave UP tracks.

  11. During ww2at a mine in Coleraine mn they tried some western coal and it took all day to get the locomotive up to steam and out of the pit. Another fallacy us running a machine like this at 70 mph. They ran at 40, on the tour, 4014 ran at50 on a verry new pice of road, on the iron range . A batch of big baldwins boughy during ww one,ran on babbit bearings pulling up to 190 loaded cars at 20 mph . The new batch came in for ww2 ran on roller bearings no faster than 30. They were actually bigger than the up enginez, with 5 thound lbs more traction, they could actuallt START a heavier train.

  12. Mark Berg, Big Boy was designed to have a top speed of 80 mph and balanced to run at 60 mph. In practice though the speed at which BB operated would have generally been lower because of various conditions limiting his operating speed.

  13. Noticed that the diagram on the page is different than the downloadable diagram. The downloadable one added modifications for the switch to an oil burning engine plus the change from “Petticoat pipes” to “Exhaust nozzles”. Peter Clark referenced the proper location of the petticoat pipes in his earlier post.

You must login to submit a comment