Would the Polar Express EXPLODE on Glacier Gulch?!?

Don't use me as a heat transfer professor.
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[@604Oaks]

A friend an I once had this conversation. Those engineer and fireman are by far the greatest engineer and fireman in the entire world and the polar express is the most pampered locomotive. Despite the insane wheel slip, black smoke never came out of the stack, only steam. Sand was never used, even on ice. And the coal didn’t even have any coal dust. The fireman wasn’t trying to think of a solution after losing the cotter pin, he was debating whether or not he should put something as dirty as his hairpin into such a well manicured machine

[@PowerTrain611]

iT's A mAgIc tRaIn!

[@firstnamlastnam2141]

Considering the route, pampering makes a lot of sense.

[@AdrianMannino]

The engineer literally drifted a train on ice.

[@firstnamlastnam2141]

@@AdrianMannino and it got rerailed again

[@AdrianMannino]

Yup, every single coach somehow.

[@AzaleaGP30]

Fun fact: I did the math a couple of years ago and it would’ve taken the Polar Express 46 HOURS to travel to the North Pole in real life if it was going at an average speed of 70mph! Guess that’s why there’s a flux capacitor in the cab.

[@blakebrooks4314]

"It was 5 minutes till midnight 4 minutes ago" EXACTLY!

[@CharlesCanary]

Why did I read math as meth💀

[@DionDPR]

​@CharlesCanaryhigh

[@Cpoll2011]

@CharlesCanarybro what💀

[@matthew_natividad]

Great Scott!!!

[@train0996]

“Considering the fact that we have lost communication with the Engineer, we are standing totally exposed on the front of the Locomotive, the train appears to be accelerating uncontrollably, and we are rapidly approaching Glacier Gulch, which just so happens to be the steepest downhill grade in the world, I’d suggest that we all hold on TIGHTLY” *roller coaster screaming ensues*

[@sirenlover100]

"I want to go on Polar Express again!"

[@amandajorangervale695]

You missed the opportunity to do it lengthened like "TIGHTLYYYYYYYYYYYYYYYYYYYYYY"

[@zacherymartin3515]

My absolute favorite line in the entire movie, and the only scene I like more over the glacier gulch bit is the ice lake itself.

[@Johndoe-jd]

If I remember how gravity works at high speed at angles, it probably wouldn't explode. At that rough of an angle at that speed, the water would be pushed back to the rear most of the boiler. (Think about filling a bucket with water and spin it in a circle. When the bucket is upside down the water is still in the bucket despite gravity.) Or at that speed and angle the interior of the boiler would be at or around 0g. (This seems to be what happens as the men seem to fly). The water would stay what it was at before it went down the grade. Now here is the real question: how much damage is done to the boiler after that much water movement.

[@SkorjOlafsen]

Welcome to the world of rocket ship ullage. Air resistance means the water would still slosh forwards, but mostly stick to the outer walls of the boiler due to whatever spin is picked up (and there'd be a lot of spin since the whole thing just tipped 90 degrees). It's a real problem for any liquid fueled second+ stage of a rocket: how to get the darn fuel down to the bottom center of the tank so that the engines don't suck air and explode. You've got essentially no adhesion on the drive wheels at that angle, so no real thrust to work with. Fun fact, when the Saturn V separated the first stage, and before the second stage could ignite, the first stage had 8 solid retro-rockets firing to keep it from bumping the rest of the rocket (the front half of the rocket had a lot more drag, so the first stage would ram it otherwise), and the interstage ring had 4 little solid fuel rockets attached, firing to get enough thrust to overcome air resistance and settle the fuel. Only once the second stage is going does the interstage ring drop away so cinematically. Ah, the other kind of steam propulsion, even more complex.

[@SkorjOlafsen]

OK, now I'm wondering: with the engine working as hard as it is, if you point the stack exhaust backwards would that provide enough thrust to settle the water at the back of the boiler and protect the crown sheet. I think it might!

[@44R0Ndin]

@@SkorjOlafsen Likely it would! You really don't need "a lot" of ullage thrust, just "enough" to overcome air resistance and then enough to settle the tanks in a short enough time period. EDIT: The thrust produced might not be all that EFFICIENT, as far as rocket engines go, but a low specific impulse (fuel efficiency, but for rockets) usually means a higher thrust potential, assuming you can increase the mass flow rate to compensate for the lower exhaust velocity (and exhaust velocity is directly proportional to specific impulse). END EDIT But speaking of ullage, there's another way to settle the tanks during staging: Use the engines of the previous stage! How do you do that? Easy, you start up the next stage's engine(s) while the previous stage is STILL FIRING. The name for this really tells you pretty much all you need to know about the process, it's called "Hot Staging". There's really only a couple extra requirements for hot staging, but as always they do add mass. 1. The previous stage needs to be able to withstand the forces and temperatures of having the next stage's rocket engines firing at it for a few seconds WITHOUT having a structural or thermal failure. Not so easy when your rocket's made of Aluminum, but the Russians seem to like it well enough (makes the rocket simpler, less ways for things to go wrong is a good thing). The SpaceX Starship/SuperHeavy also uses hot-staging. 2. The interstage needs to be similarly durable, but ALSO needs to have an open structure to allow for escape of the rocket exhaust while the next stage is firing while still attached to the previous stage. The Russians like to do this by making the interstage out of high-strength steel struts (or maybe girders, haven't seen pictures of the interstage of Proton or Soyuz with high enough detail to differentiate) instead of solid panels of formed metal, but SpaceX seems to fabricate their hot-staging ring (what they call the interstage) out of the same sort of stringers they use to reinforce the tanks in other places, which makes a lot of sense since it means you don't have to make as many different kinds of parts to make a complete launch vehicle.

[@kevinpark1]

there's a couple year old video that explains that it would not explode on Glacier Gulch but rather on the downhill before flat top tunnel as that would have left the crown sheet uncovered for about a minute before shocking it with the water slosh after the tracks flattened out edit: found the video kzbin.info/www/bejne/mKmzp6uNiMmff7M

[@JaneDoe-dg1gv]

@@SkorjOlafsen the stack thrust would help regain a small amount of traction at the drivers by pushing the engine into the tracks. Perhaps that extra acceleration would settle the water.

[@Railman1225]

1:49 Fun fact about Pere Marquette 1225: she also served as the inspiration for the original book by Chris Van Allsburg, who played on the locomotive as a kid while it was outside Michigan State University. That, I believe, was one of the main reasons they wanted 1225 for the movie design(and also, yes, number for both occasions).

[@bostongeis5123]

Its weird he illustrated a PRR K4 instead of PM 1225 for the book since that’s the case

[@a_steinman]

Railman is correct, that is where the 1225 comes from. I never actually held the book so I can't speak to the wrong loco being illustrated.

[@bostongeis5123]

@@a_steinman Bad phrasing on my part. I don’t disagree that 1225 was the inspiration, thats why I think it’s weird he didn’t illustrate it. Especially since he’s also the illustrator.

[@Railman1225]

@@bostongeis5123 Well, creative liberties/artistic license and all that. Might I add, it looks more like a generic steamer(albeit with D&H style headlight) than a K4. If that'd been the case, it would've had a Belpaire firebox and high-mounted headlight.

[@bostongeis5123]

@ Thats a good point. What makes me think its a K4 is the running board, the tanks on the top and bottom, the wheels (not the wheel basis) and especially the bell. The pilot and headlight, and the weird sand dome are the things that don’t make it look like a standard k4. Some K4s did have the headlamp in the middle at some point, but idk if that matters lol. Also, its hard to say what the wheel basis is in the illustration with the bush in the way lol. I think you’re right about generic steamer/creative liberties, cause even if was a K4, it’s very stylized. Regardless, 1225 is the polar express

[@ShadowHawkProductions]

I'd like to see your take on the scene where the Polar Express pretty much spaghetti noodles up the mountain shortly after the ice scene.

[@chasogamo]

FINALLY SOMEBODY NOTICED THE TRAIN LITERALLY BENDING LIKE A SNAKE

[@atshinkansen7439]

Yeah, watching the train do that really takes me out of the scene. Looks like the train’s made from a foam pool noodle.

[@DukeOfTrains]

Gotta remember most boiler explosions were caused by splash back or putting cold water from tender over already exposed crown or low enough where the cold water coming in contact with extremely hot steel of the crown sheet

[@ITrooper089Productions]

Simple, it’s one of those Bendy Boiler Locomotives the Santa Fe had

[@susanlua4792]

@@ITrooper089Productionsyou mean THOSE cursed engines….?

[@strasburgrailfan90]

You forgot to mention the coal that would have been floating around, like the engineer and fireman, allowing cold air to enter and help cool the firebox.

[@nathanharrison2]

not if the fire door wwas shut, and we do see its spring loaded with a foot switch

[@lukereyes6266]

​@@nathanharrison2 it looked like the one with the holes drilled I to it, so air still could've gotten in

[@ChrisSpringer-d1r]

Cold air is dense air, my friend. It would only supercharge the fire in the firebox, making our problem worse.

[@lukereyes6266]

@@ChrisSpringer-d1r too much air too little fuel = less heat...

[@ShadowDragon8685]

@@lukereyes6266 The problem is that the coal would all float and knock around, crumbling, increasing the surface area, in an oxygen-rich environment, meaning that coal-fire is going to _flash._

[@t-12productions15]

Could you imagine the poor souls who have to service this choo choo?

[@callsignapollo_]

Considering the working conditions of the other elves, and the shop crew having ~363 days to service 1225 between her madcap cannonball run every year, it might be leisurely compared to the turnaround time of the army of boilermakers working for UP's engine shops to keep the freight moving in the 40s/50s.

[@t-12productions15]

@callsignapollo_ Yeah, I guess you're right. They have a year to service this thing.

[@Lv-sl3rm]

Also general fact that in the movie they've got magic and all.

[@elijahcuevas3805]

Mechanic: wtf happened to her!? The engineer and fireman in unison: two words, Glacier Gultch!

[@trevorv3478]

@@elijahcuevas3805Don’t forget, THE PIN!

[@AuraKnightTheLucario]

the other day i came across an even sillier version of the polar express ice skid scene. The polar express ice drift - unhinged version. was hilarious.

[@TheOutlaw2.0]

Welcome to Landons Animation Wheelhouse lol

[@roadtrain_]

... it's quite literally next to your comment in my feed.

[@OttoMatson]

I've seen that. Omg I was crying laughing.

[@SteamPower-kr6ui]

Three ideas for polar One when the kid in yellow says they’re gonna toss her off the end of the car, maybe a broader “what happens if you lose your ticket” And do cotter pins actually hold throttles on and can something like that actually happens And is it really possible to ski on a train, could be more math intensive but yk it’s a major part of the movie I’d argue

[@Hyce777]

that's three ideas... lol, but all decent shouts

[@SteamPower-kr6ui]

@@Hyce777 thank you, sorry about that!

[@James-the-idiot]

I'm pretty sure the only way to make a steam locomotive go anywhere you want it to on ice is if it's something like a 0-6-0, 0-8-0, or 0-10-0, only driver wheels, and it would have to be aimed PERFECTLY where you want it to go

[@lukereyes6266]

​@James-the-idiot they're talking about how the main chara and the ghost skied on top of the train to get to the tender before the tunnel

[@randomscb-40charger78]

@@lukereyes6266 I think depending on the speed the train is traveling at as well as how good the suspension is, the oscilliation that occurs with all conventional trains might just send you flying off if you can't stay stable.

[@wolffang-vz2ty]

I know this is all in fun and all but I would have to assume the crew knows that the Gultch is coming and likely would have overfilled the boiler to compensate ahead of time making the exposed crown a moot point

[@Hyce777]

That was the other math I meant to do! I don't think they could have filled it up enough on the uphill.

[@James-the-idiot]

​@@Hyce777 so start before they hit the hill?

[@whatusernameis5295]

​@James-the-idiotthe issue is once water gets high enough you will start pulling it into your cylinders

[@michaelkolano8686]

or probably cutting the fire down since they're going through a large downhill region

[@CDROM-lq9iz]

@@whatusernameis5295 I had this thought too, the dry pipe would be underwater if the boiler was turned like that. So, if the throttle was open, that locomotive would have quickly lost cylinder heads and or running gear.

[@onnelli]

Oh, jeez. The Polar Express is 20 years old? Time isn't real! Edit: Wow, I'm surprised that the crown could actually handle the Hollywood bs of Glacier Gulch. I mean, the crown may have survived, but I do believe they may have vaporized the children in the cars

[@IsaacBaxter]

To real. To real

[@tobinrowe9558]

Next year the book will be 40.

[@west_side_9]

WHY WOULD YOU SAY THAT!?!?

[@musiqtee]

Einstein agrees. (on the before-edit statement…) 😅

[@stuchris]

They're making a sequel now too

[@mattheuston9363]

the very definition of "down hill fast". santa must charter through the ES&D railroad museum.

[@Idaho-Cowboy]

You telling me that Polar Express is more realistic than Derail Valley? But hey that's just a theory, a film, I mean a foamer theory!

[@tatecarlson]

Well I don't work about the specifics, I watch it for the entertainment, but interesting little detail, the Polar Express is set in the year 1957, in Grand Rapids, Michigian and that kind of makes sense of the route the train took, up through Michigan up into Canada on through Glacier Gulch then across the Arctic Ocean to get to the North Pole

[@Empire526]

1:47 Oh, that's why it took so long for my S282 Demonstrator to fill up with water! (almost two entire tenders I think) Because the bottom of the sight-glass is about halfway up the boiler!

[@nielsleenknegt5839]

It's more like only showing when the water is at 80% I would think. Also, cold water: less density.

[@CMDRSweeper]

Well, I guess after that model test of the silly drifting train on an icy lake... The next step is engineering Hyce theorizing modifications as to HOW to make it happen! Then maybe Mark have to do some work in CoS at some point perhaps to make it all fit with crazy Hyce's ideas.

[@Hashtag_Cow]

Train:Kaboom? Hill:Yes Train. Kaboom.

[@kleetus92]

Kowalski! Analysis!

[@wild_lee_coyote]

Not to mention when the train evens out then you get the water flashing into steam as soon as the water sloshes back onto that hot crown. This would cause a pressure spike on top of your softened crown. Good thing it is animated.

[@Hyce777]

That's more of a myth than fact in the case of all documented boiler explosions, as far as I can read.

[@genoobtlp4424]

I‘d be more worried about the water sloshing into the pistons

[@ppheard1254]

Yes it could, but it be more likely on the slope towards Glacier Gulch since that hill took long for it to descend. 1:20 Actually 179° Grade is practically even ground, it would have to like 89° Grade to be a vertical drop.

[@jaelwyn]

But upside down and running backwards... now I'm envisioning as Mobius rail...

[@cartermaloof4980]

This will always be a weird movie for me. I think it was my first time seeing a steam train on the big screen. Yet I haven't seen it since.

[@Voucher765]

The Nickel Plate 765 is actually the cousin of 1225 herself, 1225 and 765 have gotten together several times including most notably with SP 4449 in Michigan in 2009, 765 herself has traveled more places than 1225 has since she only runs mostly in Michigan her home state meeting up with Baldwin built ex GM&N Pacific 425 and Reading T1 2102 for the 1988 NRHS convention in Somerset New Jersey the first time the engine went to the northeast

[@Spud607]

Hyce just gave me PTSD from a train video... *HOW IS THIS POSSIBLE!?!?!*

[@ricardo1885-y7m]

The Force is strong with that intro.

[@RailrunnerRHS]

The boiler might not have exploded, but surely the cylinders would be having A Time. No way you're not drawing water past the throttle valve if it's stuck open, lol. Love these silly train science videos and looking forward to the rest of the series!

[@sabliath9148]

I have to wonder if the sign entering Glacier Gulch was supposed to read '79°' (very steep, but still upright) and someone decided to be a troll and added an extra leading digit.

[@cswvna]

Well... if flat track is zero degrees, wouldn't 179 degrees be inverted? So I think you're right.

[@kevinpark1]

@@cswvna no 180 is straight up and down 181 would be slightly inverted so 179 is just barely not a straight drop you have to remember if you flip the angle around and measure it 181 is the other side of 179

[@Tyrope]

@@kevinpark1 Let's assume the track is 0 degrees, that means, on a 2d circle, it's a left-to-right line. Now rotate that circle 180 degrees, feel free to use whatever image editing tool you have. It's now right-to-left. up-and-down is (+ or -)90 degrees.

[@kevinpark1]

@@Tyrope but grades are based of of what the previous grade was so going from 6 degrees to 4 degrees is a - 2 degree grade

[@Eragor-h5n]

1:55 It should be nited that Pere Marquette 1225 was *not* chosen due to its locomotive number. It was chosen both due to it being available at the time of film production and (more importantly) due to it being the inspiration for the locomotive used in the book the film was based on.

[@TheFlyingSquirrel1225]

As a pilot, we talk about left turning tendencies aircraft experience. (If you want to know why there’s a ton of videos out there) so when I first watched the polar express, and saw the lake scene. This proved to me that trains must also have left turning tendencies as when they go into reverse they go the other way.

[@JaneDoe-dg1gv]

I think that was the coaches dragging themselves back behind the locomotive. Since the locomotive is so heavy, once it is moving in one direction it will keep moving in that direction. the forward and back running could have been them trying to control both the sideways movement (like sideslip) and the swinging oscillation of the train. think about the coaches behind the train like a vertical stabilizer. Nose (locomotive) point left, tail (coaches) push left till the nose is facing forward again. of course this is relying wholly on drag but similar enough concept. then when the engine was facing where the engineer wanted, "give'r the beans!"

[@natetalkscars]

So all the crown sheet calculations make sense, but when you rotate the engine so the headlight is pointing at the ground the primary direction the heat goes is no longer the crown sheet. They would need to put a new fire door and maybe rebuild part of the stoker system every run over the gulch. That would suck needing to clean the remains of coal plugging the flues out after every run.

[@Hyce777]

Mmm. Fair. I'd assume with enough fire it'd still be heating the crown pretty significantly, but yeah, maybe we should've done the math for the backhead. Lol!

[@genoobtlp4424]

Well, if the backing is toast, you don’t go kaboom, you’ll just want to gtfo of the cab and wait until you can see whether you can shovel (or stoker) some more. Might aswell go find the piston caps as I‘m pretty sure they would’ve sucked some significant amounts of water into the pistons

[@coryfriend8325]

​@@Hyce777 In freefall (cotter pin floating), there's no "up"...

[@JaneDoe-dg1gv]

@@coryfriend8325 there may not be an up but the airflow would drag the coal off the grate and out the stack. honestly, nowonder smokey was shoveling like crazy on the ice lake. Dude had to add a whole new firebed back to the grate.

[@macmedic892]

4:03 There are two kinds of people: 1. Those who can extrapolate based on incomplete data. 2.

[@smyset111]

...Those who can't.

[@AresHoax_9]

I know what this means but I always get irrationally angry at this, and yet I think it’s a great joke.

[@j-train13]

I start heat transfer this spring after the Christmas season. Thank you for the prelude Hyce

[@RioGrandeRailfan473]

the math hurts my brain but I still enjoy watching this!

[@VixessRin1702]

I'm genuinely so excited to see more of these Polar myth-busting videos! Polar Express holds a special place in my heart (saw the premier in theaters as a kid and to this day it's still a yearly tradition to rewatch with my family) and I'm glad even proper railroaders aren't too bothered by a little holiday magic C:

[@KnapfordMaster98]

I'd love to see you nitpick the cab controls, not the throttle and brake stands but all the other junk in the background. Smokey's fireman side controls are very nutty looking. Banks of mini-quadrants hanging from the ceiling, chopper handlebars in some sort of submarine periscope configuration? I'd love to see you try and break down what they were actually based on and what they might theoretically do.

[@OttoMatson]

There's a flux capacitor as well.

[@hadinossanosam4459]

13:12 I think there's an easier way to estimate that number: the locomotive could produce around 2.2MW of mechanical power (according to Wikipedia), and assuming an overall efficiency of 10% (an average value for steam engines as far as I could find, but could be adjusted depending on superheat, construction details, Carnot temperature ratio, etc.), the fire would need to produce around 22MW of thermal power in steady-state under maximum load. The distribution over all the heating surface is a little harder to estimate, but the crownsheet accounting for around a quarter of that power feels reasonable - it's probably less than a quarter of the area, but among the hottest regions Also yay metric :)

[@drillboyjenkins5740]

Hyce, you had to integrate the thing, your heat transfer rate varies in the process because the temperature difference changes from (1370 - 207) = 1163 to (1370 - 600) = 770 moments before disaster (insert nerd emoji here). By the model you have the Boiler T vs Time graph should not be a straight line, but rather a curve that gets more shallow. This won't change the results by an order of magnitude, but a lil bit more time. Also I don't like things I have heard for the mass evaluation but I will assume you did multiply the area by BOTH thickness and steel density or used some ready-made data table that lists aerial density of steel vs thickness.

[@jaelwyn]

Came to the comments to point out the need to account for using calc here, thankfully you already did.

[@cmdrbigbob]

Y’all beat me to it. Ironically Thermo and Heat transfer were my best subjects.

[@Ronald.Golleher]

15:50 so THAT'S where Derail Valley got the time for boiler boom after no water going over a hill top!

[@therailfanman2078]

Probably the safest passenger train on the ES&DT

[@484berkshire]

10:43, my sentiments exactly! Even though Thermodynamics was one of my favorite subjects in college, my brain just refused to fully grasp the stuff in my Heat Transfer class. Also, given the events of the movie, the train was supposed to be traveling much more slowly down those inclines were it not for the throttle's cotter pin coming loose; so that likely means on a normal descent, the locomotive would've been pointed down for much longer than ~10s, yet clearly didn't explode before this point. Guess we can chalk that up to magic too.

[@ryansedletzeck]

Love this video! Something to think about: There would’ve been non-negligible G’s pulled at the bottom of each hill, increasing both the weight of the crown sheet and the water above it. The masses would remain the same, so your heat transfer equations wouldn’t change; but, I wonder how hot the steel crown would have to be to fail if it and the water above it temporarily weighed 3-6 times as much? I bet the higher G load would cause a structural failure sooner at a lower crown temp!

[@MichaelAllanFrancisSheaver]

I was just as surprised as you were by the final analysis. But then, I am reminded that air is a very poor conductor of heat, so it is reasonable to learn that steam is much slower than steel at heat transfer. I LOVE this kind of rabbit-hole geeking/nerding out! ♥

[@patricksheary2219]

Hi Mark, after I got over my math PTSD moment, this was an absolutely fun exercise. Like you, I so thought choo choo would have gone boom (that magical cotter pin actually saved everything🤣)! Never thought about the steam factor nor time. Always learning something new from watching your channel, Mark. Brought much giggles! Many thanks for this latest video, Professor. Looking forward to the next installment, and as always cheers to you!

[@inqufox1750]

one thing the youtube engineers forget, because i've seen a few of these videos, is when you're going down that steep of a hill you arent out running the train here, the train is out running you, the water is never going to leave the crown sheet uncovered its going to be out running the water at a fair pace and even when its going up hill as well, the water is going to almost always cover the crown. If you cant out run a roller coaster you cant out run a locomotoive...anyway happy holidays!

[@chasesrailwaylinesrr6447]

19:08 "I'm not taking 491 to a lake" XP

[@alexlail7481]

Just remember while a glacier is made of 'ice' it isn't crystalline ice like an Ice cube it's really more like a very very hard cork gasket. I expect that would have a huge effect on the behavior of said choo-choo

[@ItsTundrian]

1:57 BROOOO BLEW MY MIND. Never thought of that before.

[@pikablob]

OHHH this is the series my question made you mention >:3. I am very much looking forward to more Polar analysis - this was my favourite Christmas movie as a kid and probably my first real exposure to American railroading as a small British girl XD. It's also ended up inspiring a bit of the writing I'm doing atm - as has your channel :))

[@Kateykat]

Ok it wouldn't explode on glacier Gulch part the crown sheet isn't uncovered for long enough, but on the skiing part the water is in the front of the boiler for around 50 seconds. That is more than long enough for the crown sheet to get hot enough for it too *💥*.Meanwhile on Glacier Gulch it's only on that downhill grade for around 5 seconds.

[@EviLincoln]

2:25 Ive been wanting a video like this for a while! I also, as a thought experiment, was wondering how strong the bridge would need to be to withstand those forces and how thick the ice would need to be to not instantly crack under the immense weight

[@cadetkohr5508]

Something I always wondered was if it was actually possible to drift the train like they did. From my perspective, you could sort of use the rest of the train as either a backboard or an anchor, depending on if you're pulling or pushing it. Wonderful video Hyce, can't wait to see more!

[@genoobtlp4424]

I mean, good luck steering. You could maybe get one drift in (and realistically fall over), but any snaking and physics would like to punch you

[@JaneDoe-dg1gv]

If the swinging could be timed one could choose to amplify or dampen the swinging while also trying to pull the train in the desired direction. It could work but would be stupid hard to make actually happen while under control.

[@baltoflyer7503]

"Jumpin' Jeepers! The cotter pin sheared off!"

[@lucaspendley231]

I love this. This was a fun video. I’m ready to see all the other polar express videos!!!

[@professional_fra_violator]

Only a conductor- but my derail valley experience was thinking they might've dumped the pan and flooded the boiler when they're approaching the NS mainline scene. I'm going to hell for this. Sincerely, UP gang.

[@dereksgc]

i will never emotionally recover from the way you draw the number 4

[@salvatoremicciche6895]

This is absolutely a necessary video and I’m glad it was made

[@QuorkQTar]

1:28 - If I'm not totally mistaken, a 179 degree slope would look different and I'm pretty sure this is more like 89 degrees. Except they would define the flat as a 90 degree slope, which I'm pretty sure nobody except mathematicians would agree with. First mistake in the movie! =P 5:28 - Having no comparisons at hand: Is this grate area of 8.4 m² a great area or a not so great area? … I'll see myself out. Though, now that limes are flying anyways, I can re-iterate my dad joke from a stream some time ago: "Given 20 is running Polar Express currently, does she still have plain bearings or does she have polar bear-ings now?" 5:50 - I mean, it's called *British* thermal units and still the Brits won't use it. That should really be a giveaway. 6:05 - Oh so it's actually a great grate area. Neat. (Sorry, I shouldn't have eaten that clown for breakfast. Might not have been fresh enough anymore). 6:40 - 245 psi is just shy of 17 bar (or 1.7 MPa as the official metric unit; but bar is, at least in railway context, the more common [inofficial] metric unit). 6:45 - Oh I shouldn't have paused so immediately to do the conversion, lol! It's 16.89 bars to be more precise, so you're pretty much spot on with your off-the-top-of-your-head conversion. Being a metric engineer in the "Imperial Empire" does things to one, doesn't it. 8:00 - To add some historical reference: According to de.WP the Bitterfeld boiler explosion happend with the following parametres: The crown sheets ruptured at 740 °C (based on metallurgic analysis of the steel). At this point the material strength had dropped from 510 N/mm² at normal operation to less than 88 N/mm². To reach this temperature, the crown sheet had to be exposed for about four minutes. 8:45 - Off topic, but that chart is something fictional media get soooo wrong soooo often, once you start noticing it. The metal being worked might have the correct colour, but not the crucible, the mold or whatever else it might be in contact with. The glow colours are universal. Stuff, whatever material it might be, at a temperature X emits light of wave length Y. 12:25 - For those outside of metric land (i.e. outside nearly all of the world =P), that's not a lucky conicidence. Historically, Kelvin has been developed out of the Celsius scale, just shifting the Celsius scale from 0 = freezing point of water to 0 = absolute zero. The modern definition is the other way round with Kelvin being the scientific base scale and Celsius being defined off it, but that's irrelevant to daily use. 12:45 - My teachers would've subtracted anywhere betwen half and all the points for missing units =P 18:50 - The maths heavy approach is great, if you ask me. There's so many people claiming maths don't matter for normal people. Your video shows how it absolutely is relevant. How it describes our world. How it allows us to assess how physical, real things will go before it happens. And so on, the whole eight point two two nine six metres. Thanks for the video

[@Hyce777]

Appreciate your comment very much my friend - and yes, being an engineer in the imperial world adds to the conversions. I agree it'd be an 89 degree slope, not 179. Lol. Hollywood

[@seankaiser2505]

Now I wonder if the water sloshing back and quenching the crown sheet right after the crown sheet being exposed to steam would cause stresses to form in the steel that would weaken it and then reduce its ability to withstand subsequent periods of exposure

[@John73John]

Hang on... isn't 0 degrees a level track? That would mean almost straight down is 89 degrees. 179 degrees would mean someone built rails on the ceiling of a tunnel that the train magically sticks to.

[@maurice9457]

it would explode for sure. in 1977 there was an accident in Bitterfeld (germany) where the boiler of the pacific 01 1516 blew up when they stopped which was caused by the low water level cuz when the train started braking, the water moved to the front of the boiler exposing large areas of the firebox including the crown sheet which started to glow red hot and when they came to a hold, the water moved back to the firebox and turned quickly into a lot of steam causing the boiler to blow up and fly across the station. the Glacier Gulch scene isnt the only one where this would have happened. theres also the one when they were driving like -45 degree down into the tunnel

[@lukereyes6266]

No, it wouldn't. The same way water stays in a bucket when you swing it around and upside down, the water in the boiler would be pinned to the back, covering the crown

[@maurice9457]

@@lukereyes6266 this would actually require the train to move faster than free fall towards gravity which is 190 - 200 kmh (skydivers speed) and it obviously didnt reach that during the tunnel scene. if it did and exceeded that during the Glacier Gulch scene, the crew would fly out at the rear of the cab while something similar would happen to the 3 at the front. since the water is protected from any air resistance it will ''fall down'' faster than the trains acceleration and ends up at the front of the boiler

[@lukereyes6266]

@maurice9457 each thing has its own free fall. Trains are heavier than water, therefore water will hit its free fall speed first, then the locomotive will hit free fall

[@maurice9457]

@@lukereyes6266 no. in vacuum everything has the same free fall acceleration and speed which is 9.8 m/s2 while weight or even material density does not matter. so when the water is sealed in the boiler and has no air resistance but the train does, the water is falling faster

[@JaneDoe-dg1gv]

Another commenter brought up how the exhaust stack would provide some stack thrust. I realized that thrust toward the track could restore a tiny amount of traction allowing the drivers to pull the engine just slightly faster than the freefall velocity. It would be just a tiny acceleration but in the near zero-g environment (shown by the crew floating) that tiny acceleration would be enough to bring the water against the backsheat and keep it over the crown sheet. Especially since the track has a tiny forward component that would barely keep the water off the roof of the boiler and not getting sucked into the steam pipes.

[@AShadowboxsFSX]

Also Hyce the locomotive is essentially in free fall... While still under acceleration. Since the water isn't actually adhered to the boiler, it would fall at g while the locomotive falls at g + a where a is the locomotives acceleration from the wheels. Therefore the back of the boiler runs into the water and the water stays on top of the crown.

[@Hyce777]

Hmm. I think you're right.

[@JaneDoe-dg1gv]

@@Hyce777 The slight forward component, from the track being not perfect straight down, would also keep the water on the bottom of the boiler and off the roof. A neat thing would be the thrust produced by the exhaust stack (since they act like rocket nozzles) pushing the engine into the track helping it gain some more traction.

[@matthewmiller6068]

If its coal fired...I wouldn't want to be between the coal and the engine in case there's any braking forces that results in all the coal "falling down" into the engineer's cab...

[@baronvandragon2427]

Thought, at that extreme downward angle. The coal and fire would shift to the front of the fire box, and the arch brick. The bulk of heat would be at the backhead and the upper most corner of the crown sheet. If you are worried about sheet failure at that angle. Why not just open the fire door? Wouldn't a hole that size let out a lot of the heat in the first place?

[@Hyce777]

That's how you barbecue our poor crew :D

[@baronvandragon2427]

@Hyce777 Ugh, now I almost want to math that out to see if the cab would heat up to a dangerous point before the end of that 10 second drop. Thanks Hyce lol

[@jaysmith1408]

@@baronvandragon2427but with the cab windows open, going straight off a cliff, i think there would be ample crew cooling air.

[@nielsleenknegt5839]

​@@baronvandragon2427 I would love to hear that result because I was thinking the same thing, but more in terms of that steel being the problem for an explosion

[@JaneDoe-dg1gv]

with how hard the engine was drafting. Are we sure she wouldn't just suck the entire firebed out the stack? That or clog the flues so bad that the fire would be suffocated?

[@iftheseoldbeastscouldtalk7796]

The Polar Express inspo locomotive, 1225 is actually busted right now. The superheaters have something wrong, and the official wording sounded like something straight out of the unclear orders vid, the crew became "increasingly aware" of a superheater problem, and that just sounds so, SO incredibly agitating and expensive to fix considering the recent several-year maintenance. Long story short, 1225 is a static display loco for the time being, and im getting closer and closer to going up to Owosso and working on it myself because broken choo choo=sad.

[@GuukanKitsune]

One thing was left out of the calculation. The brake pin being lost means the Pole Ex was going down that grade WAY FASTER than it normally would be, so it would not have been a matter of seconds on thise drops, it normally it would be MINUTES in going down those drops. So, that being accounted for... if it had been going down those grades as they presumably normally would... yes the Pole Ex ABSOLUTELY would have exploded. It seems that full throttle hell for leather risking derailing like a roller coaster is LITERALLY THE ONLY WAY any train can make it down Glacier Gulch.

[@JaneDoe-dg1gv]

and the full draught in practically zero-g would suck the firebed off the grate; instantly snuffing out any fire in there. either by sucking the coal out or clogging the flues to stop any air getting in.

[@edd17sp74]

I think I learned more about how a steam locomotive’s boiler works from your Paint drawing and explanation that I ever have previously. 😂 And my immediate thought after seeing your drawing and explanation was “Well, the engineer and Fireman (I think their names are Smokey and Steamer, they’re like two of the only characters in the movie with names) are floating around the cab in zero gravity, so I would think the water in the boiler would be sloshed backwards toward the firebox, not running down toward the front of the engine.” I don’t know how you’d calculate out those physics, but…I feel like there’s a chance the crown sheet never gets exposed at all.

[@crazyguy32100]

The scary thing is that is a regular part of the track, regular enough that the conductor recognized they were getting close and there was signage. If the boiler didn't go kaboom when making a pinless, uncontrolled decent, how would it have survived at normal track speed on a regular Christmas run? Maybe that part of track is meant to use Mexican overdrive (the big quiet gear) under usual conditions.

[@SteamfanScott]

I have to admit, haven't actually seen the movie. A fun and informative look into boiler dynamics, and yes, math is hard. It was my absolute worst subject in school, I pretty much hated it and regularly did quite poorly in all my classes. So what did I do? Study engineering of course! I got my degree after much hard work, and I still don't like math... Looking forward to the rest of the series, very intrigued about how a train may steer on ice! My thought is that possibly there is a certain thickness and hardness of ice that would allow the flanges of the wheels to break through and create "tracks" while still able to support the train and thus allow it to steer (assuming the pilot truck is "steerable" in some way)? *shrug* Interesting!

[@MegaLokopo]

I wonder if it worked out that way, because of a train or math nerd being on the production team, or if it was purely by chance.

[@Niklas.K95]

The engine seems to be the least endangered species in those scenes. More important, how much whisky do you need to forget that you run the same route for Santa Clause every year?

[@timothyteo4602]

@Niklas.K95 would 10 barrels be enough?

[@Niklas.K95]

@@timothyteo4602 depends how much time they need to handle them

[@timothyteo4602]

@@Niklas.K95 you’d also have to assume the crew’s not blind drunk to make the run to the North Pole from all that whiskey

[@Voucher765]

The Pere Marquette 1225 in real life can right now only run in home territory despite her iconic status, Her cousin Nickel Plate Road 765 has traveled as far east as Pennsylvania and even New Jersey for the 1988 NRHS convention at Somerset

[@Snow_Empress]

Have to say mark I've been wondering for years if you actually could steer a steam train like they do in polar express but could never get an answer so I'm glad to see you will finally be providing me this answer.

[@MorsCanis]

Thanks for the lesson Professor Choo Choo.

[@buckduane1991]

I was at a Christmas Party yesterday and we had a trivia quiz… level 5 included “identify the Christmas movie by the LEGOs!” and the 6th was… LEGO Polar Express. Out of 8 teams, only ours got it… and in a team of 5, only I got it. After the round, I actually stumped our trivia host by asking him “what real life locomotive inspired Polar Express?” So, I told him about the 1225, including the year it was made, being a Berk, and being a Lima. He was stunned. Train nerd life.

[@jerrysgardentractorsengine2243]

This video cursed 1225 with a case of “bad superheater-itis” Thanks, Hyce

[@Urbanizedatol]

Probably my favorite Christmas movie, and the movie that really got me interested in steam locomotives (that and Thomas and Friends 😂).

[@JaneDoe-dg1gv]

story of... pretty much most of us here. Happy holidays.

[@billyrueckert5113]

"That's what we do. Make assumptions and add a safety factor...DING!" That's my favorite.

[@chasemoon8519]

My brain now hurts

[@glennmcgurrin8397]

There's more than a few complications involved 179 degrees is nearly level upside down the fire and heat source is going to be moved around as well which will change things if it was nearly vertical instead of upside down there would be zero G effects in play from the freefall draft issues from the normally air entry side now being on top of the normal air output any preparation in terms of dropping fire level and raising water and I'm sure there's more, this one is rather complicated.

[@pavelslama5543]

I always assumed that the ice steering was not done by differential left/right propulsion, but by the diagonal pulling force exerted on the zig zagging train consist.

[@JaneDoe-dg1gv]

I'm thinking that the coaches are swaying like a pendulum behind the engine and that drags the nose to sway left to right. then the controls are about making the whole train slide side to side while controlling how strong the swinging is.

[@andrewadams3894]

Tipping the locomotive on end will result in the arch brick and fire bed falling into the combustion chamber quite likely plugging the tubes and flues and killing draft. The total heat content of the heated coal and brick will still be radiating to the exposed steel. Plus, whatever portion of the coal is still burning. I'm of the opinion, that if it didn't blow up on the way down, it would crush the track and punch into the ground -- and then blow up!

[@chcknmr]

I have enjoyed this for sure and i can’t wait to see the next one! Yes you will tackle the ice which is what I would have suggested anyways but I’m also curious if all the couplers would have held during the ice thing or if simply pushing all those passenger cars in reverse would have changed its direction then what we see in the movie.

[@dylanbrookes9501]

aww, that would have been fun to see 491 ice skating! 🤣

[@SteamCraftOfficial]

yay!!! I was hoping you would do this video!

[@gervaisreed4473]

The scary part is that not only if this engine survives the run once and makes it to the North Pole It’s that if u run that engine every year without replacing the crown sheeting it will eventually fail anyways

[@redgray99]

What would the water sloshing around inside be like? Would it cause any issues or would it be fine? Would it slosh forward as it points down hill or would it accelerate fast enough and slosh backwards?

[@Hyce777]

That is a fantastic question.

[@AugustusTitus]

I feel like the next calc needs to be to determine how many Gs the locomotive must sustain in order to keep the water in the right place when going down Glacier Gulch.

[@Katoro101]

You missed something.... After each hill, its levels or does uphill again. The water comes back, so its not just the steam colling the sheet, but the water at intervals.

[@t-12productions15]

10:23 Fun fact the poor dude was HAND fireing this choo choo, meaning that the stoker was broken

[@Hyce777]

well, that or he's getting the corners. :D

[@t-12productions15]

@Hyce777 Yeah, I guess you're right, but on the ice, the poor man is walking from one end of the cab to the other with the shovel, presumably full, or He's getting his steps in

[@enejvizintin4746]

By your math, it really wouldn't have exploded. But have you considered the fact how fast the water would turn into steam as soon as it touched the crown sheet. Wouldn't that have created great pressure on the crown sheet? Plus, the quick contraction from the metal would probably put it under a lot of pressure. But to be perfectly fair, I'm not a mechanical engineer (yet), so my predictions might be completely wrong, but that's what I see happening inside my head.

[@nielsleenknegt5839]

Not to high of a temperature difference? It's a lot of water at 200°C, and the steel shouldn't be anywhere near 600°C.

[@TheAsianGmer]

I got a final soon on HT. This video might just be the reason I pass. Thanks Hyce.

[@JanTonovski]

I am currently in my 1st year of aerospace engineering, so this is a great taste of what is to come 😂

[@rootbeerking2892]

Considering what you showed us in the March devlog update with the squiggly track. I suppose we could try and make some thing similar except on the narrow gauge! Just sending 491 nearly completely vertical straight down. THE ULTIMATE POLAR EXPRESS EXPERIENCE!

[@baileydevries4494]

Putting those mines engineering classes to work! cant wait to get to heat transfer

[@rdreher7380]

For me the Polar Express is not a movie. It's a much more charming children's book that my Dad would read to me when I was little. I don't have incredibly negative feelings toward the movie, but being a movie it of course had to add all this drama and excitement to draw out the story, and personally I think the dreamlike and wondrous feeling of the story worked much better without all that stuff and in the form of a picture book that you read and gaze upon quietly as the snow falls in the black of night beyond your window. It is kind of annoying that somewhat over-the-top movie monopolizes the name of the original work, overshadowing its spirit a bit. Anyway, this silly thought experiment reminds me of when just the other day I made fun of a wonky toy Christmas locomotive in a catalogue that like didn't even have a smoke stack, and my girlfriend was like "It runs on Christmas." Lol.

[@crazysdk]

Oh wow, I literally just got back from the theatre watching The Polar Express (they were showing it as a special event) and saw this video was just posted. Scary timing.

[@TroyHaynes-e1b]

theoretically it is possible for the polar express to get across the ice by applying the throttle to start straightening out but right before you do you you stop applying throttle and lett the cars keep going which turns the locomotive and repeat that alot with a little breaks on the cars and shoving it in reverse it might be possible with one johnson bar instead of to.

[@JaneDoe-dg1gv]

yeah it seems like it could work by controlling how it swings.

[@a_steinman]

The Polar Express 1225 comes from the Pere Marquette 1225. From The Steam Railroading Institute (current owners of PM 1225): "Today the Pere Marquette 1225 is owned, maintained and operated by the Steam Railroading Institute. It’s part of the National Register of Historic Structures and is renowned for its role in the 2004 Warner Brothers Christmas Classic, THE POLAR EXPRESS™. 1225’s blueprints were used as the prototype for the locomotive image as well as its sounds to bring the train in the animated film to life!"

[@lightningwingdragon]

Oh the lake question is fairly easy it's never been a matter of if the driving wheels can turn in different directions. It's always been a matter of the hinges the couplings pushing again it's like trying to push a string The string will turn and bunch up thus allowing the head to rotate and so that forward reverse forward reverse forward reverse CAN STEER

[@JaneDoe-dg1gv]

Yeah! by controlling how the train swings side to side by choosing when to pull or push against the coaches. the coaches are what drag the nose around. The engineer is just controlling how much the engine is pulling on the coaches and then letting the locomotive's forward momentum carry them through the rest.

[@timothyteo4602]

19:00 I already (sort of) know for a fact that the locomotive is not going to survive the ice purely because of its weight. I kind of know this as I have a book by Christian Wolmar on the Trans-Siberian Railway where in the early days before the line around the southern shores of Lake Baikal was completed the track was instead frozen into the ice. There’s at least one account that states that all the passengers were told to disembark so that the train crew would “honourably” go down with the train should the ice give way, whilst the passengers had to trek to the other side of the lake itself. There’s train then followed onto the ice and although there was a few crunches the ice held firm. Now since this was in either the late-Victorian era or right in the Edwardian era, locomotives would be considerably light by European and thus also Russian standards, and given how at any one stage even a train as light as that could still break through the ice, I have a feeling that an 802,500 lb (even though I’m Australian and use metric I still like to try and use Imperial units) locomotive alone would’ve broken through the ice possibly on first contact.

[@JaneDoe-dg1gv]

the ice thickness is our unknown variable. considering how strong ice is. it could hold the weight if the ice was hecking thick. No cool ice breaking as it slid along though.

[@Hyce777]

Wacky... wow. Thank you

[@timothyteo4602]

@JaneDoe-dg1gv I can’t remember well since I first read it in the book, but apparently the ice was somewhere around 3 feet thick. The Russians were also laying the track directly onto the ice and then freezing it into the ice itself with fresh water and just the cold temperatures to do the rest of the work. Having said that, I do have to agree with you that it might’ve supported the weight of such a beast, but I guess it’s up to our own judgment to figure out whether something as large as a Berkshire or a Northern would have survived on the ice, even to the point of drifting on it

[@zacharysiefer8272]

Another thing ive always been curious about is how the boiler withstood the mass of all that water slamming back and forth on the hills. Santa must make some damn good rivets and stay bolts.

[@Fangs-jo4bq]

Can't wait for the next video on the polar Express.