Why do USA steam trains make smoke, but UK ones don't?

A facebook post spawned a desire to cover this topic of secondary air, and why smoke is made. Hopefully it helps your understanding of locomotives :)

Special thanks to Dynamo Productions for letting me use their footage:

LMS Training Video, uploaded by the Bennett Brook Railway:

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[knightryder]

I also feel like the fact that in the US, our engines chuck everything out the stack, UK engines don't, and that's why they clean their smokeboxes often.

[kristenburnout]

Having taken a few combustion courses in university, there is nothing more satisfying than seeing a steam locomotive produce almost no smoke even under load. Yes, watching huge amounts of black smoke looks dramatic, but it's a sign of inefficiency! Not to mention the huge amounts of particulate pollution: The British steam locomotives often ran in more urban environments, so I would imagine keeping smoke down was a priority, even in the era when people thought cigarettes were healthy.

[wilsonlaidlaw]

Back when steam locomotives were in earning revenue mode, making heavy smoke was regarded by the Norfolk and Southern Railway as a potential disciplinary offence, as it wasted fuel and led to complaints from the public. In the era before tumble driers, washing was commonly dried on a line and being downwind of a smokey locomotive, could ruin the whole wash. In the UK with preserved locomotives, making smoke is regarded as wasteful and anti-social.

[A_person]

I don't know. That's why I'm watching this video.

[kennethhummel]

The wife’s grandfather was a conductor for grand trunk railroad back in the 1940s-50s. He always had a fit when he saw huge clouds of black smoke coming from the trains on TV shows and movies. So we all asked him one day why? He told us that all that smoke was from forcing the engine to run before it was properly warmed up and ready! He went on about air to fuel ratios, air flow and other things. He ended by saying he wanted to go to Hollywood and knock a few heads together and teach them how to properly run a steamer!

[gonvillebromhead]

One very important reason why you don't see black smoke in the UK - it is actually illegal. Cannot recall whether it is the Clean Air Act of 1956 or 1968, but allowing a locomotive to produce black smoke is naughty and can lead to fines. Whilst realistically, a heritage railway wouldn't be fined for a quick "oops, bugger" moment from the fireman, doing it consistently and deliberately for a photographic charter would be a big no-no.
Quite how this will change with the slight coal problems that UK heritage sector has been having recently remains to be seen.

[ardensreeves]

I'm a fireman here in the UK - and I'm very much looking forward to visiting the US and experiencing your behemoths! This was a fascinating video, thank you; I never realised how different US-designed fireboxes were. Secondary air is drilled into us in the UK as extremely important; any large quantity of black smoke, such as at 3:24 in your video, would in the UK draw comments from the driver and frowns from any inspectors present!

[baronvandragon]

Added note on the Oil Burners. As they burn, soot will build up and the tubes and flues insulating from the heat of the fire. So, every now and again, they pour sand in the fire chamber which then bounces around and knocks soot loose. Leading to a big trail of black coming out the stack.

[CatholicSamurai]

There’s an excellent video on YT from someone driving side-by-side on the highway alongside UP4014 at about 60mph, and the Big Boy was running so clean that it barely produced any smoke, despite how hard the locomotive was firing - impressive!

[alanmcgunnigle]

Interesting comments which agree with. In the UK in the 1950's steam era you never saw black smoke coming from operating steam locos. I worked on station shunt locos for a time and you were not allowed to make smoke in the station environment. Even now, in New Zealand, I can fire small steam locos and produce virtually no smoke with crap coal. My job is to show new firemen how to fire so that smoke is kept to a minimum once the loco is operating.

[MightyFineMan]

Your calm demeanor while describing in-depth explanations of these questions, which sometimes we didn’t know we had, is always much appreciated.

[MrHeesbeen]

In Britain, the type of coal used is normally a product called steam coal. This burns very hot (it would quickly burn through a domestic grate) and usually burns cleaner. In the traction engine community at traction engine rallies, owners get very annoyed with organisers who supply normal coal because it creates less heat to drive the engine, burns dirtily and reduces performance.

[Nareimooncatt]

The photography thing is certainly a big reason, and the pic at 2:10 is a perfect example of why. Photographers like action shots of a train, but that one pic looks like it was parked. True, you can demonstrate speed/movement in other ways, like with a panning shot, but that isn't always possible. Even though it's not a true representation, a big cloud of smoke gives the impression of the locomotive working and moving, and makes for a more dramatic shot overall.

[TheClashen]

As a retired engineer I remember having to calculate and analysis how to burn fuels efficiently in my university degree. Think this was the best lab experiments we did. Though I went on to work for a company that designed and tested engines that did not use combustion as its energy source. We still had to maintain the back up diesels and sited heating boilers so they burnt the fuel correctly without black smoke. A term to remember for future discussions on the subject is the Stoichiometric fuel mixture ratio which is when all the fuel is burnt with no excess air (Oxygen) used. Another wee aside, as all the firemen will tell you its the gases that burn and not the solids. Hence the soot. So Stoichiometric is your word of the day and a ratio to remember for your car is 14.7:1

[gregrice]

Not really a train guy, but watched from curiosity. I can't believe how well I former you are, and how quickly and clearly you communicate the facts, history, and physics. I wish you
Well and great success! You stand out from most "sales funnel" videos online, usually overselling something and wasting people's good time to do it.

[stevensainerailfanproductions]

I think you summed it up perfectly in terms of the fuel quality how good the fireman is and coasting.

Ed Dickens one time was asked the same question and he said that they realized when the engine is smoking it’s actually wasting fuel. So they try to keep both engines as clear as possible. Best advice if you want to see a big boy smoke, just chase it in the winter.

Although N&W 611 and any of the locomotives at Cass Scenic Railroad smoke just as much as a power plant most of the time.

[legdig]

In the UK we have dampers set up for directional running too, so you have control the airflow with those depending on the direction of travel relative to the firebox to get a good draft and complete combustion. Not sure how much of a thing that is on American locomotives.

[sclm]

When I first went to work for the railroad in the early 70s (in South Texas) there were still quite a few "old heads" from steam locomotive days left on the railroad. Hearing some of their stories, if a Road Foreman of Engines noticed an unusual amount of black smoke coming from a passing train, it was possible for the fireman to receive demerits "for waste of fuel". All the steam locomotives in use at the time were oil burners. Coal as a fuel in most of Texas had been phased-out by the time of WWI or in the 1920's at the latest. Plentiful cheap oil was too good a bargain for the railroads to ignore.

[jraybye]

Norfolk and Western had stenciled on the front of the tender, right where the fireman could see it, "Black smoke means waste." When the railroad granted permission to O. Winston Link to photograph their engines at the end of steam operations, they requested he refrain from taking pictures of engines emitting black smoke.

[ChrisHaines-kz]

Interesting insightful video! Having been a rail fan (steam mainly) for a long time I have to agree with you that photographer expectations have a big influence on smoke production. My Dad wrote a letter to Lucius Beebe in 1948 complimenting him on his then recent publication of Mixed Train Daily and got a response from the one of the biggest influencers of the time with regard to rail photography. I’ll quote a portion of the letter here where Beebe talks about the photos he used in his book. “The smoke effects were deliberate and calculated on our part. Simply we have seen so many pictures that we know to have been taken at speed but which show no exhaust at all that when we undertook Mixed Train we swore on a stack of Stork Club menus that we wouldn’t run a single action shot that didn’t show all the smoke we could get. We just think that an engine that isn’t visibly working steam has no point whatsoever to it. We worked apart” (referring to his partner Charles Clegg) “and took shots repeatedly over wide terrains to get the most possible exhaust, occasionally asking for it, but usually catching it at places where we knew we would get the greatest volume. We wanted every damn picture to be perfect, and there is hardly a single one we are going to change in the next printing.” If you have any of Beebe’s books you’ll see a lot of smoke being produced for the sake of drama and not efficiency. I thought this was a good data point to corroborate some of you conclusions.