Why The Polar Express would Explode

Have you ever watched the movie, The Polar Express? Well, have you ever considered the fact that The Polar Express could potentially explode, completely wiping out everyone on board? If so, sit back and relax as I show you the facts behind why the Polar Express probably wouldn't have been able to make it to the North Pole!

[ChriswithaK]

Thank you for all the comments and support! Apart from a few comments, many of you are very kind and bring up points that I would have never thought of when making this video. Please know that this video in particular was done only for good fun, I didn't expect this video to blow up (but here we are).
Many of you brought up points that disagree with the fact that the Polar Express would explode. It's great to see many of you thinking outside of the box, I love the idea of discussion and responded to many of them already. however, I keep seeing the same points brought up over and over. To make things easier, here is a list of points many of you make that I already responded to:

1. The water would stick to the back of the locomotive due to the engine going downhill
- While it's true that water will stick to a surface if enough force is applied to it, it does not apply to the movie. The only way for water to stick to the back of the engine as it's going downhill is for the Polar Express to be accelerating faster than the velocity of a falling object on earth (aka gravity). There is evidence of this NOT happening in the movie. As the train crests the hill and goes downward, the speed alone would have launched both the Hobo and the Boy off of the roof of the car due to the sudden acceleration. In other words, the locomotive would need to accelerate from its near stopping point at the top of the hill to more than ~9.81 m/s^2 (32 ft/s^2) or 21.8 miles an hour compounding exponentially per second. This would also mean that as the locomotive rushes down the hill, (assuming that the locomotive is attached to the track) both the Hobo and the boy would float away from the train since again, the locomotive would need to be accelerating faster than the velocity of gravity. This does not happen in the movie and therefore we can deduce that the water in the boiler does not stick to the firebox as the locomotive goes downhill.

2. The Engineer and Fireman could have completely filled the boiler with water before going down the hill
- Filling the entire boiler with water would mean there would be no place for steam. The Engineer and Fireman will always leave space in the boiler for steam to pressurize. If there is too much water in the boiler then water might enter the regulator and destroy the cylinders in the process. Water, unlike steam, does not compress and will essentially blow out the cylinder heads if they enter into the cylinder. This is why you will almost always see steam coming out of the cylinders whenever a steam locomotive is starting up. That is the Engineer opening the cylinder cocks to allow for any leftover water to exit the cylinder.

3. It's a Magic Train
- Yes it is, I'm glad we watched the same movie

4. Boiler Fusible Plugs
- Some people were confused in the video since I got a few of my steam locomotive terminology wrong here, thank you for the corrections in the comments. Fusible Plugs are designed to let water (which instantly vaporizes into steam) into the firebox to put out the fire to prevent a boiler explosion. From the information I found online, they worked but usually didn't help much with putting out the fire. It was more used as a warning system that the water level was too low for the engineer and fireman instead of a preventative measure. What I meant to refer to was the Crown Stays. Crown Stays in some boilers can be used to prevent it from exploding by only allowing a certain part of the crown sheet to fail rather than the entire component, leading to a full-on explosion. When this happens, it causes a backdraft inside of the firebox, sending steam from the boiler into the cab. It's not the best situation for the Fireman and Engineer, but it's better than the entire. locomotive blowing up.

Chris with a K is a channel I do for fun on the side. I don't have the time to respond back to all the comments on the videos, but I will try my best to respond to the ones on this thread.

Thank you again for watching, Happy New Years!

[rippersix]

Steam locomotive crews working in the Rockies would routinely raise the water level considerably in the boiler before descending steep grades, to avoid the risk of running a “dry crown sheet”. The crew of the Polar Express ran that run enough to be aware of the danger involved with that grade and act accordingly. Just an observation from a professional boilerman….

[ladiesman]

So in back to the future, part three when the boiler exploded while it was still on the tracks in real life, it would’ve shredded Dr. Brown and Clara?!

[rockinrainbow]

7:07

And that's why mountain climbing engines like the ones at the Mt. Washington Cog have tilted boilers! When climbing up a 27% grade they need their boilers to match the incline of the mountain so the engine doesn't explode

[collin]

In conclusion.



The Polar express is built different.

[hanro]

Since the polar express is made to run that route. It might be possible that some design considerations had been taken to make the train capable of surviving those angles.

[abrr]

the melting plugs in the crown sheet are a warning system to the crew, rather than a preventative measure, as engines have exploded with those things melted through.

[smyset]

the hill is so steep that the 1225 wouldn't have even been able to climb it. still pretty good analysis though.

[anzebeton]

You forgot the tunnel. The boiler would have exploded right as they entered the tunnel amplifying the blast as it had only two directions to travel. The momentum of the wreck would have pulled the unshredded cars inside the tunnel which is now a furnace.

[DZSabre]

This is a fun video. The explosion is not caused by the water instantly turning to steam when reaching the firebox. Since we are talking about a modern (mid 20th century) Berkshire locomotive, the explosion becomes more interesting. What actually causes those explosions is the sudden cooling of the crownsheet which causes a crack. The water in the boiler is already under extreme pressure so it remains in liquid form even past the boiling point. When that crack forms, the pressure has a means of escape and with the sudden decrease in boiler pressure, all of the water, which is already well above the boiling point, instantly turns to steam and escapes through that crack turning the boiler inside out and launching it into the air.

[DonSMDT]

You know, giving that this is a known train with a very reliable arrival time, you probably would have a rescue team sent out pretty much immediately, so realistically you could have a team of elves out in 3-4 hours, allowing for the possible survival of some children.

[doge_sevens]

maybe the engineers prepared for this and filled the boiler with water to its limit so if the water sloshed to the front there would still be enough water to say cover half the crown sheet at least giving enough cooling until the train reaches the bottom of the hill

[sabertoothstudioshq]

Well to be fair during the scene on glacier gulch, the G-force from the engine going down that area would have done somekind of damage.

[Arkay]

Because it's impossible for a Berkshire to go down a 129 degree grade without crashing at the bottom and exploding on impact.

[LeoLeo-qoyw]

But if the crownsheet weakens, that doesn't lead to a boiler explosion. At least, not in the way depicted by the pictures. Remember, for a boiler to explode, the thing that has to fail is the shell. The outer layer of steel. That is the actual pressure vessel. As the water comes back in contact with the firebox, some will evaporate and generate a pressure surge, however, since the water was all at the front, where much less heat is transfered. That means, steam production rate goes significantly low. Since the loco is still using her pistons (that means the steam consumption rate is the same), the pressure will decrease during all the time she's going down. Now as the water sloshes back, it'll create a pressure surge, as i said, BUT, since the pressure inside the boiles has gone down, and the water is pretty difficult to bring to a boil, i'd say the shell would be perfectly fine. Maybe some valve or piston damage, but no explosion.

What COULD happen is that the firebox's top weakens from high temperature changes. Basically, what happens when you pour hot liquids in a cold glass. The fast reduction of heat, combined with the extra stress from the pressure surge and the deformation that could occour while it was overheated, might lead to a failure, but of the firebox.
Which basicallly lets all the pressure from the boiler inside the firebox, and since the only way out of the firebox is directly inside the cabin...

Yeah, it's not a good scenario for the enginneer and fireman...

[danshobbies]

What if, since it’s a magic train, the boiler was 100% full, that the water wouldn’t slosh around? 🤯

[biesifoto]

The Bitterfeld boiler explosion happened in 1977, not 1997. At that time, Bitterfeld still was part of the German Democratic Republic, or simply East Germany, which was a Eastern Bloc state and due to its economical situation was still running steam engines regularly.

[Bearcats]

as a guy ho enjoys steam, this was very informative and correct info on how boilers can explode and the workings of a boiler.

[Shipwright]

Admittedly the grades on the track in the movie are way steeper than anything a real steam locomotive could handle, and the curves are so tight the train literally snakes around the mountain (something no real, and quite rigid, steam boiler could ever do.)

Also a bit of a pet peeve that the throttle is pushed to be opened instead of pulled.

Do I still like the movie? Yup. Who wouldn't want a steam locomotive that was all powerful and could go anywhere? Galaxy Express 999 appeals for the same reason. Steam train in space!

[Uajd-hbqs]

I admire the attempt to explain why a train that ran without a track, could climb 80 degree gradients and was Tokyo drifted on ice would actually explode.