Big Boy #4012 is on static display at Steamtown in Scranton. Not the heaviest steam locomotive ever made, but certainly the longest. Sixteen driving wheels on one machine. Built by the American Locomotive Company (Alco) in Schenectady NY to UP design engineers’ specifications.
Union Pacific converted #4014 to oil burning for a number of reasons, among them prevention of track fires by eliminating coal cinders, and of course ease of refueling since they can refuel both diesels and steamers from the same fuel supply. As far as traction is concerned, #4014’s sandbox can hold 8,000 lbs of sand, so plenty is available to put under the driving wheels.
Just to correct myself: Certain websites say that #4014 is set up to burn No. 5 fuel oil (usually in the form of recycled lubrication oil), although perhaps it may be that in a pinch, No. 2 (diesel) would be used.
I don’t think that cinders burning the ties on the mainline is a problem anymore because they use concrete ties. But accidental wildfires would be a problem, I guess.