Everything Wrong with the Trains in Back to the Future: Part III

Added: 2026-05-30

[00:00:00]Trains have appeared in many films throughout the years as everything from the setting of the story to being part of a greater action setpiece. As cool as these scenes are, not all of these engines are true to real life, and that gets on my nerves. So, today we're going to take a look at everything wrong with the trains in terror. Before we look at the trains, let's first look at the context. The plot of Back to the Future 3 is, well, let's be real. You already know what it is. Stuck in the Old West, Doc Brown and Marty McFly need to get their broken down Delorean time machine up to 88 mph in order to go >> back to the future. To do this, they decide to steal a train and use it to push the car along a flat piece of track, shoving some magic science fuel logs into the fire to get it burning hot enough to produce enough steam to hit that 88 mph goal. There's some action, suspense, and romance before the Delorean reaches its top speed and zaps away into the future where it reappears on a model bridge. The locomotive, meanwhile, rockets off a cliff and explodes in a ravine.

[00:01:17]The locomotive used for this caper was Sierra Railway number three. Initially built for use on the Prescott and Arizona Central Railway in 1891 by the Rogers Locomotive and Machine Works. It came under the ownership of the Sierra Railway Company of California in 1891 where it helped in the construction of multiple lines and frequently handled mixed traffic services. After several accidents and a long career, number three was eventually put to one side in Jamestown in 1932, where it remained until the late 1940s.

[00:01:50]Producer David Oelsnik came across the engine while looking for a locomotive to destroy in a train wreck for the film Jewel in the Sun, but the railroads master mechanic persuaded management to instead restore the locomotive to be used for charter services and for studios to hire out for movies. Ever since it's appeared in over a 100 different films and TV shows, making it one of the most filmed locomotives in the world. Most of the sets in this movie were built in various places around California. Many of the train scenes being filmed at Railtown 1897 State Historic Park. And for the final train scene, a scale model was built for the pyrochnics and shot where it drives off a cliff. Two Alco S6s belonging to the Ventura Central Railway appear at the end to destroy the Delorean and as far as I'm aware are still in service to this day. But enough about the behind the scenes. Let's look at the scenes themselves.

[00:02:49]When we're introduced to the locomotive, it's dolled up to look like Central Pacific Engine 131 in plain black with white detailing. Whether or not the real 131 wore this exact livery is a bit beyond me since very few pictures of the engine exist, never mind in color, but that's the least of the art department's crimes. 131 was an American 440, while this engine is a 10-wheeler 460. On top of that, it was built in 1891, 6 years after the movie takes place.

[00:03:22]Credit where it's due, the Central Pacific was a major railroad in California at the time. The film is set in California and Sierra number three is an engine that worked in California all its life. So it was far from the worst engine the producers could have chosen for the role. The spark arresttor 2 is different from 131's actual spark arresttor. So another ding there, but such a spark arresttor would be both location and period accurate. At the station, we also see that the train is made up of both goods and passenger cars, a common practice at the time. So, a mixed traffic engine was a very sensible production choice. When asked how fast the engine could go, the driver states that he'd had it up to 55 m an hour himself, and that someone managed to get a similar engine up to 70. 55 mph is plausible enough for an engine of this size, but with 56-in driving wheels, 70 is a stretch. Why does the size of the driving wheels matter, I hear you ask? Put simply, the bigger the driving wheels, the faster you will go, as one full rotation would cover more distance with the same amount of piston travel. Smaller wheels allow trains to start easier and put more power down to the rails, but the cylinders need to work harder to maintain a high speed.

[00:04:37]Bigger wheels make the train harder to start, but can reach and maintain higher speeds much easier. 70 mph alone would be giving the cylinders a hell of a workout. But the driver states that on a long level grade of track, it might be able to do 90. It took a lot of effort to get dedicated express locomotives to reach such speeds going downhill, never mind on a level grade. So a comparatively small wheeled mixed traffic engine like this has little chance. Also, I don't know what the driver is doing with this oil can. And frankly, I don't think he does either.

[00:05:11]When we see the bridge that's under construction, all that's been built thus far is about 40 odd feet that ends in a sudden drop. Now, I don't know much about bridge building, hence why I'm not bridge of thought, but I'm pretty sure you're supposed to complete the bridge before you start laying the rails on it.

[00:05:27]Or at least if you get this far, you keep going. I don't know what kind of decisionmaking would result in something like this, but I'm certain there was a lot of spite directed to someone in upper management. Look how steep those rails are, too, leading down to the bridge. Again, I'm no builder, but I feel even Bob would have his work cut out for him sorting that lot out. Fast forward to our protagonists getting the Delorean on the rails, and I'll mention it here since I know someone in the comments will say something. The Delorean's track width, or how wide the axles are, is 5'3" in. Standard gauge rails, meanwhile, are 4'8 1/2 in, meaning that Doc would have to do some serious modifications to get the car to run on the tracks. We can assume he's already locked off the steering, too, since turning the wheel would probably derail the car. I've watched that episode of Top Gear, and evidently so did he on one of his trips to the future. Later on, Claraara pulls the emergency cord to stop her train. And to my knowledge, passenger cars of this period didn't have emergency pull cords.

[00:06:33]On top of that, the train stops surprisingly quick considering the speed it was going. Emergency stopping is meant to be fast on trains, but that's shockingly fast, even by modern standards. Can I also just point something out? This isn't a train error, but more to do with the plot. The reason Doc and Marty are in a hurry to get back to 1985 is because Bully Guy was out to kill them. They agreed to a jewel at 8:00 to avoid him since they'd be hijacking the 8:00 train and vanishing shortly afterwards. However, Marty beats the guy up anyway, removing the need to get out of dodge. As such, both could have just stuck around for another week or two until they found a more suitable locomotive. It's not a major error or plot hole since Doc and Marty seem to be the ride or die types, but still. Now, on to the actual bit you came here for.

[00:07:25]Firstly, 131's tender is full of wood, yet its funnel belches out black smoke, which is typical of a coal or oil burning engine. Wood burners tend to produce a more pale or lighter gray smoke. But since number three is an oil burner, that explains the black smoke.

[00:07:41]Credit where it's due though, the real 131 was a wood burner, so historically it kind of checks out. When uncoupling the locomotive from the train, we see them connected via Buckeye couplers.

[00:07:53]It's around this time railroads began adopting automatic couplers, but they wouldn't become regulation until a few years later. Seeing how number three was originally built with Lincoln pin couplers 6 years after this movie is set, I think it's safe to say a Californian engine in 1885 wouldn't have been fitted with knuckle couplers yet.

[00:08:14]These presto logs that Doc uses to avoid stoking the fire are a bit dubious. He states that once each one combusts, the sudden increase in heat will cause a sudden burst of acceleration. While a hotter fire will generally improve a locomotive's performance, a sudden increase in temperature won't just give a sudden increase in speed, as it'll take a few moments for the heat from the fire to transfer to the water in the boiler. Green smoke comes out of the engine before Doc puts the logs in.

[00:08:44]Somehow, Doc rigged up a temperature gauge from the locomotive's fire to a little dial in the Delorean. The explosion of the logs causes a huge eruption of fire and sparks to come out of the engine's funnel. If the boiler was hollow, then the explosion probably would erupt from the funnel like this.

[00:09:00]But the blast would have to travel through multiple boiler tubes, which would greatly diminish its strength. So, in order to come out that powerful, it would have to be one hell of an explosion. One that without question would do some damage to the boiler tubes. The only plausible explanation I can come up with is that the logs let out a load of sparks upon combusting and the draft of the boiler combined with the exhaust blast of the cylinders would pull a load of sparks through the boiler tubes and blast them out the funnel.

[00:09:28]Also, good job arresting those sparks, spark artor. With how high the boiler pressure would be at this point, those safety valves should be blowing off like fireworks on bonfire night. A blast powerful enough to blow off the funnel like this would without question rupture something important inside the boiler.

[00:09:46]Best case scenario would be a pipe bursts and the escaping steam would cause the engine to lose power. Worst case scenario, no matter what was happening internally, steam would not be leaking out of the smoke box door like this since the smoke box is hollow and the funnel would allow it to escape before enough pressure built up to make it leak out like this.

[00:10:07]The external rivets that burst out are what holds the boiler casing on, not what holds the boiler itself together.

[00:10:14]So, these shouldn't burst. The fact that steam is coming out of the boiler like this means it should have exploded by now. To summarize, a steam boiler is like a big balloon. The pressure inside it is significantly greater than the pressure outside it. So, if you punch a hole in it, no matter how small, all that pressure is going to try and force its way out as fast as it can. The end result, bang. I would also like to note that steel melts at about 2,200° F. So, when Doc said that the boiler would explode once the needle goes red, he wasn't wrong. Given the state of the engine, the water level in the boiler should have ran low long ago. So, I can assume the only reason the firebox crown hasn't given out is because Doc was smart enough to keep the injectors open as the engine is running to keep feeding the boiler with water, which means the fire would have to be burning hot enough to effectively superheat the water in an instant. The amount of fire pouring out of the funnel is concerning at best. The blasts of steam exhausted from the cylinders would dampen some of the flames or at least cause them to rhythmically increase and decrease with the locomotives puffing. I don't know what Doc put in those logs to get results like this, but I feel like there's a lot of live steam modelers that would like to find out. And then the locomotive goes off the cliff in what I'd consider one of the best train crashes in all of cinema. When hitting the ground, it explodes into a huge ball of steam and fire. The fireball part of the explosion is perhaps the most unrealistic aspect, and there wouldn't be a pause between the engine landing in the ravine and the boiler bursting. As soon as the locomotive makes impact, it would be one big bang and an eruption of steam as opposed to several smaller explosions with fire. Again, the explosion should be less fuel tank going up and more like a balloon popping. Back in the future, when the freight train hits the Delorean, it just falls to pieces like a poorly made airfix kit.

[00:12:17]Really, a car in this situation would be totaled, but it'd stay mostly in one piece. But that's more of a car error, though, and I'm not car of thought. So, instead, let's give a ding to the driver of the engine for not stopping after colliding with a vehicle near a level crossing. Clearly, there's something up with that crossing since it knows to close on its own in preparation for Doc's time train to arrive despite the fact it would have no way of detecting it. And then we have this. I I'm not doing this. Figure it out yourselves.

[00:12:50]I'm tired.

[00:12:57]What more is there to say about Back to the Future? It's the second Robert Zmechus film I've covered on this channel and there's a good reason I like his work. His earlier work. I mean, I watched all three movies back to back and there are so many creative and dynamic shots. The logistics of them boggle my mind. The callbacks, the background details, setups, and payoffs are all so immaculately done. Combined with some terrific performances from Michael J. Fox, Christopher Lloyd, and the rest of the cast. It's that perfect mix of comedy and sincerity that makes these movies lightning in a bottle. If you've not seen these movies before, then this is your sign from the universe to watch them. And if you've already seen them, rewatch them. Train accuracy, I'd give a 7 out of 10. It's not 100% period accurate, and there's some nonsense around the physics and logistics of the railroad, but like the time travel aspect of the movie, it explains enough so that you don't really question it. Like, yeah, you probably could get Sierra number three up to 90 m an hour if you had it flat out with a 2,000 degree fire, but it would require a lot of luck and absolutely ruin the locomotive. Credit where it's due, the stunt does ruin the engine in the film.

[00:14:13]And even though I knew stuff like steam leaking from the smoke box and boiler was utter BS, the acting, music, and cinematography really helped sell the danger of the situation. This isn't the Lone Ranger with its spaghetti track nonsense. The laws of thermodynamics do apply here, and the characters are basically climbing over an 80 mph bomb.

[00:14:34]I could keep gushing, but I think I'll button it there. Good movie, good train, good time. What more could you want?

[00:14:43]That was a rhetorical question.