Why Locomotives Don't Have Tires

Friction is the final frontier of vehicle/rail interaction!
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A single modern diesel freight locomotive can deliver upwards of 50 tons of forward force (called tractive effort) into the rails, but it’s somehow able to do that through the tiny contact patches between two smooth and rigid surfaces. It’s just slick on slick.
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[@PracticalEngineeringChannel]

Sorry for the lack of actual F1 cars in the intro! Turns out, very hard to license footage 😄 The finale for the railroad series is now on Nebula! nebula.tv/videos/practicalconstruction-installing-a-water-main-below-railroad-tracks?ref=practical-engineering

[@panchor]

Starting with "Formula One is..." while showing Indycar is a really good way to get a lot of people up in arms. 😄

[@achdubloedesau]

@@panchordid you just copy the top comment?

[@F-Man]

Doing anything with Formula 1 is a recipe for either getting hosed for way too much money, or for having their commercial rights holder come after you with bogus charges of copyright infringement. Ask me how I know 😅

[@RaindropsBleeding]

Well, at least you know they're not F1 cars 😂

[@MarcosElMalo2]

Before I watch the rest of this video, I hope you address the important and often overlooked fact that trains don’t have steering wheels. OK, let’s roll the video.

[@davidphillips5395]

I was a location manager and had a retired train engineer working for me. When I was having a "challenging" day, Brad would see this and say, "David - How do you start a train?" and walk off. One day, I stopped him and asked him what he meant by that statement. "There is no locomotive set that can possibly pull a mile long train from a stand still. The locomotive pulls the first car, which pulls the next car, which pulls the next." The slack in the coupling is crucial to allow this 'chain reaction' to occur. He shared that sometimes, with a green engineer, they'd pull into a stop to change crew while under power, taking all of the slack out of the couplers. No go. The solution was to back the train a distance to re-create the coupler slack. So, the life lesson was, if you have a big challenge you're dealing with, find the solution in a series of small fixes rather than viewing it as one big problem ... one car at a time.

[@attilajuhasz2526]

Well said. Thanks for posting this.

[@serversurfer6169]

Oh. I thought the lesson was, "Back up and get a running start." 😅

[@nickwallette6201]

Hmm.. "How do you start a mile-long train from a stand still? You take the 'R' out of 'rail' and the 'F' out of 'way'." "There is no 'F' in 'way'." "Exactly."

[@SheepInACart]

I think you've misunderstood what was said, you don't back a train up to increase slack before starting, and indeed taking any single bit of rolling stock from 1kph to 2kph takes more energy than taking it from 0kph to 1kph.. common practice on the rail line is to creep forwards in low throttle notches till the rear of the train starts to move, and only then add most of the power, otherwise your being very rough on the rear couplers with all that inertial jerk (there are springs in all couplers but the locomotive to help reduce it, and this will actually cause a stopped train braked only at one end to "equalize" very slowly on low grade track), and on bigger trains will break them outright. But "how do you start a train" is still the correct saying, because it starts slow, you don't feel like your doing much and if you kept going at this rate you'd never make it in time.. but you keep going and as you keep working on the problem you get the means to apply more force and solve the problem faster.

[@vincentpowelliii8964]

One car at a time...Beautiful

[@DavidCaddock]

I'm sure Brady knew the cars at the beginning were not Formula 1 cars, because F1 is very protective of copyright, and he didn't want to deal with the headaches.

[@get2dachoppa249]

Yes, very true, that is exactly what I thought.

[@kngofbng]

So he should have changed the wording to not suggest those were F1 cars.

[@Nebula-qq8sg]

@@kngofbngbut he was talking about something relating to F1 cars. I don’t see the problem, he just needed a visual aid, and he got one. He could’ve drawn a F1 car on a whiteboard and it would’ve done just as well.

[@FunAngelo2005]

But they are the same type of cars, so it gets the point of it bieng a race car

[@PrefaceofDysphoria]

I mean he could use an ai generated image or video of f1 to gray area out of copyright if he really wanted an f1 car 🤷‍♂️ but i agree, saying "race car" would have been a better choice.

[@alexconmy5576]

If Grady ever wanted to lure me in to kidnap me for some reason, all he'd have to say is "Come take a look at these demonstrations in my garage" and I'd follow without a second thought

[@gominosensei2008]

Demo...napping

[@GreenlandRobot]

Hey kid, I've got simplified science experiments in my van wanna see?

[@WyvernYT]

And he gets away with it in the end because there was no abduction or threats, just several weeks of playing with cool engineering in his garage.

[@ddegn]

@@WyvernYT I was in Grady garage for a full week before I figured out I had been locked in.

[@louisianagator95]

​@@ddegn I was too busy playing with the toy construction equipment in the sand table to realize he locked the door

[@mitchelldurward8863]

Grady is just so wholesome. Listening to him talking about engineering is like receiving a big informative hug.

[@Carl_McMelvin]

BUZZWORD ALERT. MASSIVE CRINGE. NPC.

[@cruisinguy6024]

Information hugs are the best

[@danbenson7587]

I like him because he’s balder.

[@luke9834]

Great expression!

[@drew5334]

"A big informative hug" just about sums this channel up lol

[@smeagolplaysgames4517]

6:51 "For longer, heavier trains, you can't just use a single, massive locomotive -" Union Pacific during the transition era: "Wanna bet?"

[@SkyhawkSteve]

yep... this seemed like a good opportunity to include a clip of the recently restored Union Pacific steam locomotive Big Boy #4014. Very impressive!

[@namewarvergeben]

The Big Boy is basically two locomotives in one, albeit with a single cab and firebox

[@jacobwhitecotton]

while true, the challengers and big boys were articulated, and had a lot of wheels, so the weight limits weren't reached

[@mohammadrifqisatriamas7311]

Gas turbine locomotive: Hello there

[@covishen]

It's a shame he didn't include something about the Big boy and the Challenger locomotives. They put the diesels to shame in power.

[@Swindy1794]

I work for Wabtec (former GE Transportation), we build freight locomotives. The sheer weight and power is unbelievable.. they are truly an engineering marvel.

[@Agent1996]

Spend some more time on making sure the rear cab door seals correctly. Thanks

[@muhammadhanifkurnaen6689]

Nah wabtec would likely drop support for legacy loco platform like C20EMP or slightly new CM20EMP. I hear some parts difficulty for these type. They would pushing GEVO to everywhere

[@ErickC]

Here's a good way of putting it into perspective for people: Most people see UP's Big Boy as some kind of measuring stick for locomotive pulling power, but it's effectively 2 large steam locomotives permanently connected to form a single huge steam locomotive, and still has about 30,000lb less continuous pulling capacity than a single ES44AC.

[@theultimatereductionist7592]

Tell Wabtec to stop BULLYING its way into California's trains. Taxpayers in California should use the OPTIMAL system for signaling. NOT just Wabtec because Wabtec is American. You can't preach FREE MARKET ANARCHY i.e. CAPITALISM when it benefits you, but then push ANTIFREEDOM BIG GOVERNMENT NATIONALISM PROTECTIONISM when FREEDOM to choose superior European designs is not in your favor.

[@Swindy1794]

@@ErickC that may be true, however diesel electric engines are by far more efficient. Especially with maintenance costs and environmental impacts.

[@DomyTheMad420]

i swear about 9/10 videos you make could just be called "check out this cool thing i built in my garage" and i'm here for it.

[@Hyce777]

Excellent video, Grady! The "Creep" demonstration was wonderful. This effect actually leads to one of the biggest wheel defects we experience in the railroad - shelling. The creep and deformation actually causes slip dislocation motion in the grain structure of the steel, and atoms start getting peeled out of the wheel, and thrown off - resulting in shelling, which is essentially a "missing chunk" of wheel. Also, Steam Locomotives actually *do* have tires! Different hardnesses as well, depending on the size and weight of the locomotive. They're really neat. The wheel on a diesel locomotive is a much simpler, and standardized part that can just be replaced; so the whole wheel just gets changed out; but with a steam locomotive and their various wheel sizes, castings, etc. - it made sense to have a dedicated tire to replace, instead of a complicated casting.

[@teeboy4158]

Hyce watches this?!

[@majortom4543]

Hey guys this is Ice.

[@majortom4543]

@@teeboy4158 Technology conextras also watches this, and both grady and Technology Connextrass channels have mentioned (phrases) of one another.

[@yorkchris10]

My grandfather was a machinist changing treads on steam wheels. Not just slip, but out of round because of connecting rod. I thought new wheels had hardened 'treads' that could be resurfaced on a lathe if not too worn.

[@jessfucket]

spalling?

[@DaHitch]

starting with "Formula One is..." while showing Indycar is a really good way to get a lot of people up in arms. 😄 But clearly not as many people who seem to read this comment as some sort of insult, indictment or judgement. Ya'll must be fun at parties. Lighten up 🙄

[@I_will_pet_your_dogs]

No such thing as bad engagement metrics. All hail The Algorithm!

[@Racing_Revolution69]

I think its a F2/F3 car

[@BR-lx7py]

I'm guessing it has to do with copyright

[@de-fault_de-fault]

​@@Racing_Revolution69 the second batch of cars appear to be F3 or some other junior formula. But the first shots are Indycar circa 2012-14.

[@Racing_Revolution69]

@@de-fault_de-fault missed that part

[@kiefershanks4172]

Hard to imagine a solid steel wheel stretching and effectively increasing the size of its contact patch to obtain maximum tractive effort. Its actually genius. Once the tractive effort reduces, the contact patch shrinks to its normal size and rolling resistance becomes minimal at cruise. The more I learn about trains, the more respect I have and the cooler I think they are.

[@PsRohrbaugh]

The physics is basically the same with automotive tires, just with rubber and air not solid steel.

[@E1Luch]

Isn't it the exact opposite? Contact patch has two parts, one under static friction (stick), and one under dynamic (slip). Stick area has higher coefficient of friction, slip has lower. Each carries its own portion of the train's weight. But when we try to increase torque to get more tractive effort, stick area decreases, so slip area carries more weight - so shouldn't the effective friction coefficient only go down?

[@ps.2]

I don't think it's the _size_ of the contact patch that provides the extra friction, it's the _shape,_ which alters the effective coefficient of friction. As friction is weight × coefficient, notice how there's no contact area term in that equation at all. All else being equal, _the area doesn't matter._ Think of it this way: with bigger contact patches, the friction is spread out over a larger area - but this is _exactly balanced out_ by the fact that the (gravitational) force pressing the contacts together _is also spread out_ over the same larger area. Of course, in the real world, all else is not equal. A certain size and number of wheels or tires _can_ be helpful. But it's not _directly_ from the size of the contact area. I think the reasons are: ­- Greater contact area, lower pressure. (Pressure, e.g., pounds per square inch, is weight divided by area. So, for example, a 3000-lb vehicle with 30-psi tires will have a total contact area of at least 3000 lb/(30 lb/in²) = 100 in². If contact area is smaller than that, tire pressure will need to be higher.) And at lower pressure, rubber tires deform, increasing their coefficients of friction. (The deformation of the train wheels is the thing you're talking about as well.) - A large contact area is good for averaging out the variable friction of a real-world surface (e.g., ice, oil, gravel, painted lane stripes). - (Not related to friction, but) a lower pressure also means the wheel and the road don't have to be engineered for a higher pressure.

[@trooper5157]

Was a tanker in the Army and this principal reminds me of how tank track moves. You'd think that the tank track, rotating but laid down stationary, under the tank wouldn't move until the rear end of it gets lifted and starts moving up then forward only to get laid down again, in a cycle. The fact is, when a tank is really hustling, all 60+ tons, the track thats in contact with the ground, which may appear not to be moving, is in fact sliding forward with the tank, slightly but evidently. If you watch closely and see video of a tank moving quickly, especially over a hard surface like pavement, you'll notice that the track on the ground is sliding, "creeping", forward as the tank moves. Pretty cool physics going on there too.

[@katie.on.fire.82]

Oh. Thanks. That helps me understand a lot better! 😊

[@schniemand]

4:10 Rolling friction (or rather, rolling resistance) isn't the same as adhesive friction. Adhesive friction is GOOD for rolling, it's what defines it. Rolling resistance is bad, unless you want to brake. This is the distinction people often forget to point out, which usually leads to confusion. Weaker adhesion doesn't help you roll better.

[@andrewharrison8436]

Excellent point - underrated comment. Engine wheels have torque applied to get them moving. Rolling stock* wheels should have minimum turning resistance * there is a clue in the name. Rolling resistance e.g. the friction between wheel flanges and rail is an energy loss and needs to be minimised across both the towed and towing components.

[@scav3155]

You guys are dorks

[@lunathecutest6652]

​@@scav3155don't you have anything better to do with your life?

[@flallana18]

@@scav3155and proud of it

[@scav3155]

@@flallana18 I'm actually a dork myself lol

[@EngineeringMindset]

Me: About to eat lunch, KZbin: Hey Practical Engineering just published a new video about trains. Perfect timing. 👍

[@WatanabeNoTsuna.]

Same! 😇

[@Skiman__]

Me when either of you upload during lunch haha

[@DrLoverLover]

why tell the world?

[@t.a4141]

Bon appetit

[@cianflavin4141]

same here

[@justandy333]

As soon as I saw the title I was thinking..."But many locomotive Do have tyres though" Especially Steam Locomotives! I don't know of a single design that doesn't. Back then, they were well aware of the lack of friction between the driving wheels and the rails, So these hard wearing "tyres" were installed to help increase the friction without affecting the rolling resistance too much. Also alot of steam locomotives were very prone to wheelslip. Some were better than others, but generally, the larger the wheel the more likely it was to slip. Hence why alot of freight locos had relatively small driving wheels. So the reason for tyres on Steam engines was purely cost saving. The Driving wheels are very expensive to mold and machine (Some can be in excess of 6 or 7 foot in diameter), So they put tyres on, these ware out and you just put on a new set. Saving the steel part of the wheel and a truck load of money in the process.

[@douglashanks4189]

The "tires" used in this case are also metal and if I remember correctly some modern trains use the same tech because cost savings.

[@matthewutech5970]

It's kind of an issue with terminology across cultures; the US population (example; me) generally only refers to something as a "Tire" if it's the removable rubber kind.

[@GreenJimll]

Diesel locos had tyres too. I know this because I have shares in ownership of class 20, 31 & 47 BR diesel locos and back when I was a active volunteer we painted white marks across the sides of the tyres and onto the wheel hubs so that it was easy to spot if a tyre had slipped.

[@unepintade]

also lots of metro sets have tyred wheels

[@stewartwyld5180]

@@matthewutech5970 Wheelwrights use the term for wooden cart wheels which have been around since forever. A shrink fit steel tire/tyre that holds the wooden wheel together.

[@johnopalko5223]

"I've set up a demonstration in my garage." Of _course_ you did. That's what we love about you, Grady.

[@Keiranful]

The German high speed rail trains ICE (inter city express) actually started out with rubberized steel wheels to reduce vibrations and thus increase passenger comfort. That stopped when we had a horrible accident at Eschede. What happened was that the rubber sleeve of one wheel started tearing off roughly a few kilometers before a switch and a piece of rubber jammed itself into the switch, forcibly changing the tracks for the rear part of the train. This derailed the entire train that had been going around 200 km/h (~125 mph), which would have been bad enough, but only led to broken bones in most cases. The problem was that a few hundred meters after the switch came an overpass and the sliding train took out the pillars of the bridge, causing the bridge with cars on it to collapse onto the train. All in all, more than 100 people died.

[@namewarvergeben]

Correction: The rubber was just one layer in between the steel hub and a steel outer ring that ran on the rail. The rubber was indeed there to reduce vibration, but it also allowed the outer ring to flex under the weight. This caused fatigue in the outer ring until one finally broke. The steel outer ring is what lodged itself into the carriage and caused the derailment.

[@keithstudly6071]

"Outer Wheel" is the tire! Not all tires are rubber! @@namewarvergeben

[@namewarvergeben]

@@keithstudly6071 Original comment described "a piece of rubber jammed itself into the switch", which is based on a misunderstanding. I specified "steel outer ring" to avoid confusion about the materials involved

[@RogersRamblings]

Many railway vehicles do have tyres. The wheel is a solid block and the tyre is a shaped ring which is heat expanded allowing it to slip onto the cold wheel and when it shrinks grips the wheel firmly. A steel rings then is clipped into place to secure the tyre. This allows the tyre to be scrapped when it reaches its wear limit. More recently there has been a move to monoblock railway wheels where the tyre and wheel are a single piece of steel and when the wear limit is reached the whole wheel is scrapped.

[@simonalexandercritchley439]

Yes I have seen the steel tyres replaced on steam locos.

[@JohnAshworth2023]

Agreed. Steam locomotives definitley have metal tyres. I don't know about modern diesel and electric locomotives.

[@garethjones7182]

@@JohnAshworth2023 I've worked across alot of fleets in the UK, analysing wear patterns, gauging, changing wheelsets and operating wheel lathes and yes modern diesel and electrics do have tyres, Trams too. Most people outside the Railway assume the word 'tyre' means something made of rubber.

[@alimzazaz]

2:20 Roller Coaster Tycoon throwback 😍

[@deino8348]

Thanks, Brady. I live right next to the Main Line of the Pennsylvania Railroad, now the Amtrak line between Philadelphia and Pittsburgh. The line is used by Chesapeake and Ohio and by Philadelphia commuter trains of South East Pennsylvania Transportation Authority (SEPTA). I've learned to recognize the wheel to rail sounds of each.

[@semanticboat]

I used to have a balcony over that line! Stayed up one night watching them replace ties, had never seen anything like it, or had much interest in trains, before seeing 20 something maintenance cars come through for that.

[@RCAvhstape]

By "Chesapeake and Ohio" do you actually mean CSX? I think that CSX's "bright future" paint scheme is a throwback to the Chessie.

[@L00_Cyph3r]

The ad for Nebula at the end was so good. No this isn’t sarcasm. I’ve heard about Nebula since a few years ago, but your way of presenting the platform, and how it compares to other platforms (loved the How it’s made reference) was just so watchable. You might’ve actually convinced me to give it a go, so hats off to you sure for producing such great content!

[@krissp8712]

I had no idea the dragster burnout thing had a practical purpose with warming up the tyres for adhesion. Today I learned!

[@tomstech4390]

Actually the other half is to clean the tires. Tires are soft and you don't want the small stones and powdered concrete picked up by driving from the pits (or return road etc) to be dropped along the track, That could potentially lead to a car traveling at high speed to come unstuck and hit the wall or opponent. -You go through the water to get the tires slightly wet which helps lower traction to help all cars start the burnout. -You don't do the burnout in the water which would spray everyone, you roll just ahead of it. -During the burnout any small stones previously picked up from the pits are flung off and out leaving the tire cleaner and obviously allot warmer. -When done on a street race sometimes water will be used and other times a VeryHighTraction fluid is used by pouring ahead of the wheels and the car moved into it. -As the burnout is done the whole wheel gets coated, VHT is already sticky but it can also help break down the rubber and make it even softer and give yet more grip, As the car moves forward this helps transfer some of the rubber from the tire onto the street for a rubber-rubber contact.

[@ryanwatterson4038]

Also leaves rubber on the track which provides more grip again

[@TheGbelcher]

I have never once wondered why trains don’t have tires. But now I’m curious 😂

[@curiousnomadic]

Haha yeah

[@TRUMAN_THE_TRUE_MAN]

Didn’t ask + my videos are way better than Practical Engineering 💀🤣

[@TheDavidlloydjones]

You didn't listen. The tires of steel wheels are steel.

[@philtheairplanemechanic]

​@@TRUMAN_THE_TRUE_MANi watched the entirety of your catalog while wiping my bungus

[@TheGbelcher]

@@TheDavidlloydjones I’d argue trains have wheels but no tires

[@zfotoguy71]

Several decades ago I was lucky to go on a ride a long in the cab of a diesel electric through the Appalachian mountains on a short line. It started raining lightly as we were going up a mountain and the wheels were slipping. The sander was not functioning. They had me stand at the front of the locomotive sprinkling sand on the track in front of the train so we could ascend. Such a cool experience.

[@ilham7345]

0:00 I think that's Indycar and some sort of junior open wheeler championship, not formula 1 Edit: Hey, since you're working on subject of train. Why don't you do a collab with Hyce? He's on KZbin and his day job is an operator/engineer/fireman of a steam engine and part time mechanic/fabricator at Colorado Railway Museum

[@Xelopheris]

I'm going to guess that licensing F1 footage is expensive as hell.

[@NorthernChev]

At 0:00, yes, that was Formula 1. But then instantly transitions within seconds to the what you suggested.

[@christhompson2006]

F1 is quick to shut down unauthorized use of their video.

[@markclawrie007]

​@@NorthernChev No that was indycar, but no doubt actual F1 footage would be taken down in seconds 🙄

[@DaHitch]

@@Xelopheris 100% Would have been copyright struck instantly too probably.

[@LoremIpsum1970]

Do you mean: Why Locomotives Don't Have *RUBBER* Tires? They might not be rubber, but some have separate, replaceable tires.

[@robinv320]

Came here to say exactly that

[@sirBrouwer]

Some French trains are now sitting sad in a corner sipping there wine out of the bottle. wile looking at its rubber tires. Thinking Am I not a locomotive?

[@cr10001]

@@sirBrouwer I think you're thinking of Metro trains. I don't know of any locomotives with rubber tyres.

[@sirBrouwer]

@@cr10001it sure is. There is one carriage that is also the locomotive. As it houses the bulk of the engine if not all of it. Making it a locomotive with rubber tires.

[@theyruinedyoutubeagain]

Absolutely brilliant video. You can see the improvement over time in your ability to summarise fairly complex engineering concepts and present them in an accessible and engaging way.

[@JesusJuenger]

That brush-on-rug demonstration of creep was amazingly intuitive and clear.

[@johnandrus3901]

Very interesting. Steam locomotives have steel tires on their wheels. When they wear down, they are replaced, just like a car tire. Diesel locomotives have witness grooves in their wheels, which determine when the wheel has to be replaced. The factor of adhesion was always a consideration with steam engines. Too low of a factor and the engine would be limited in its use. Diesel and steam engines are inverse in how they put down power and all of this starts with the factor of cohesion. This is another subject, really, but it is all part of the whole.

[@tubester4567]

Steel tyres can work on slow steam trains and trams but the engineering community has moved away from steel tyres after the Eschede high speed train crash in Germany. When one of the tyres cracked then got caught on some points. The tyre unrolled itself into a spear that penetrated the carriage. Over 100 dead. Anyway steel tyres are more trouble than they are worth with machining, press fitting and the danger of them coming apart. Much easier/safer to make a solid wheel, when they wear recycle them to make new wheels. Its amazing that train technology hasnt changed much in 300 years when it comes to wheels and rails. Other than minor improvements like welded rail its basically the same.

[@johnandrus3901]

@@tubester4567 Yes, I know of this accident. It was caused by the tire separating from the rubber damping ring, between the tire and the wheel. They used this design because of vibrations caused by the original steel wheels, at high speed. They thought that this would mitigate the problem. This design was never meant for high-speed applications. It was never tested for this type of use. Steam locomotive tires were pressed on hot and allowed to cool, shrinking them onto the wheel. This made them an integral part of the wheel This is how they did it in the age of steam. Rubber dampers were never part of the equation on steam locomotives.

[@johnandrus3901]

@@tubester4567 Yes, I know of this accident. It was caused by the tire separating from the rubber damping ring, between the tire and the wheel. They used this design because of vibrations caused by the original steel wheels, at high speed. They thought that this would mitigate the problem. This design was never meant for high-speed applications. It was never tested for this type of use. Steam locomotive tires were pressed on hot and allowed to cool, shrinking them onto the wheel. This made them an integral part of the wheel This is how they did it in the age of steam. Rubber dampers were never part of the equation on steam locomotives.

[@alistairwhite2906]

@@tubester4567 the do still run steel on steel tyres though. That accident had a different design that sparked the failure/accident.

[@tubester4567]

@@alistairwhite2906 Only on trams and slow speed/historic trains. Many modern trains are even moving the brakes from the wheel to a separate brake disc rotor. Most of the wear on train wheels comes from the brakes.

[@paulholmes672]

Excellent lab tools, sir. Have been studying railroad systems, both domestic and international (I lived for two years next to a Japanese rail freight track) for over 60 years as a hobby, and your ongoing series is comprehensive and much appreciated. One point of expansion, steam locomotives do slip more, due primarily to their reciprocating tractive effort, and the uneven rotational wheel force. Steam has much better ' to the wheels' tractive effort, but getting it to the rail is to the Diesel's advantage, and your point of MU operation distributing that force was explained beautifully. Thank You Sir!!

[@alistairwhite2906]

That's one of the biggest things between steam and diesel. Diesel can start a train off better but a steam loco is better for speeds in it's designed speed range, 70-100km/h for a lot of them. That's where steam is actually more efficient than diesel if a modern design of steam loco is used.

[@jeffer1101]

I always like watching your videos on rail topics. The sister company of the company I work for specializes in modernizing locomotives and rail cars to make use of newer technology to improve fuel economy, emissions, maintenance costs and fleet management of rail operators. It is nice to see other people talk about the engineering in the rail industry.

[@engineering_guy]

Nice work in explaining creep! I always find it difficult to explain it to others without involving differential equations and material flow. I never thought about bristles on a rotating disc! That was amazing! Also a small nitpick is the stick slip illustration. The leading edge is always in stick. Only the trailing edge slips within the contact patch. As the creepage increases the slip area completely covers the contact patch as you showed.

[@squeaksquawk4255]

In the UK (And probably elsewhere, idk) trains actually do have tyres, they're just also made of steel, because it's cheaper and easier to replace the detachable band of metal round the edge of the wheel than the entire wheel. Edit: Ok, I spelled it wrong, I get it.

[@keithstudly6071]

In the UK they are tyres. They spell funny. (plough)

[@rsambrook]

Correct. They all have tyres (correct spelling in English), it’s just not vulcanised rubber. Changing a steel alloy tyre is cheaper than scrapping a wheel.

[@karlrovey]

Stream locomotives in the US had the same thing.

[@pras12100]

Trains also get "flat" tyres/tires at times This is usually from brake problems or harsh (emergency?) braking where a wheel skids along the rails for a distance without turning.

[@nounoufriend1442]

Only tyres on older locomotives , even on the 1970's class 56 we started to fit Monoblock wheels , waggons virtually all have Monoblock wheels . We did get problems with tyres if they had been heated due to dragging brakes , the tyres would move on the wheel this is why you often see white pain marks on wheels ,tyres had secondary security the gibson ring on inside of tyre

[@SportyMabamba]

Point of order: they do have tyres, it’s the outer steel of the wheel. They can be ground to restore the desired profile or rotated around the locomotive during maintenance. They can even be replaced during midlife overhaul 😃

[@markjanowski1502]

Great explanation of how wheel creep works. My dad was one of the engineers who worked on the implementation of EMD's Super Series wheel slip/creep system. The EMD 50 series locomotives used a radar system to measure the actual ground speed of the locomotive. I know my dad worked on the radar system design and the high voltage cabinet (where the 50 series control system modules live).

[@MikeHarris1984]

I am already watching next week's construction video and it is awesome!!! I love that these companies and the city invited you to do these!!! Awesome PR for the city too with the growing construction.

[@GeekmanCA]

You mentioned cold welding and how you weren't going to get into it. But honestly, even though I've seen a few KZbinrs mash two pieces of extra-smooth metal together and - seemingly by magic - get them to stick together, I never considered the practical, engineering implications of this phenomenon. I think it would make a great video to talk about this, if only briefly.

[@1a1u0g9t4s2u]

Spent 4 years working on a metro project overseas. As an Interface Manager, now retired, between the three consortiums I had the privilege to read various train to rail test reports. At the time, and due to my background as an electrical engineer, I learned many things but not to a great depth. This video enabled me to connect several dots and several of those reports now make complete sense. Thanks for sharing.

[@Ben786]

Grady, your demonstration/visualizations never fail to impress!

[@davidryder3374]

"Nebula...totally ad-free!" Has there ever been a content platform in human history that didn't start out saying this?

[@rfldss89]

Even on youtube, paid channel subscriptions make a lot more money per viewer than any amount of ad revenue. As a platform very open about not looking to pursue profits at the expense of UX and quality, they'd be foolish to ever include ads on their website.

[@ChevronQ]

we all know you’re from the USA, but maybe you could open with „here in the USA, most locomotives have a diesel electric drive train“ 😂 In Europe diesel is not common, but this is just a small little thing 😊 great video! enjoyed watching it, including the definitely-F1-Cars 😂😊

[@HarshVengurlekar]

Exactly. Even in India a diesel loco is a rare thing nowadays with 94% track being electrified.

[@Soundhound101]

Another hit in the world on free information for all. Thanks as usual Grady. You're truly a scholar in your crafts.

[@johnmarston2616]

I grew up watching How It’s Made all the time. Your videos definitely scratch that itch

[@riograndelocos9639]

i always wondered why locomotives experienced wheelslip if they applied full engine power when starting to move. now i know it happens from the contact patch getting less traction because the train is forcing its full tractive effort at a low speed... even as a long-time railfan im still learning new things and it really brightens my day, grady

[@sensonic6514]

A good example of the stick/slip nature of the wheel/rail contact patch. Congrats for putting it in terms that doesn't bamboozle the audience :)

[@Warhawk76]

Love your channel man!! That demo with the circular brush was great for really showing the effect you were explaining. I am doing my second year teaching engineering to high school kids and my background in the subject is not perfect, so I am always wanting to learn and also find new ways to engage the students.

[@chopper3lw]

What a great explainer. You're so good at this.

[@KnowArt]

great video! The brush wheel demonstration about creep makes perfect sense if we think about the train braking, instead of accelerating.

[@XenophonQ]

I like trains

[@worlds_okayest_pilot_421]

Fascinating.

[@kamakaziozzie3038]

You know who loves and knows more about trains than any other human? Sheldon Cooper

[@unmortal8672]

you always make such clever ways to explain real world mechanisms and it just amazes me

[@ShawnsTrains265]

You're my new favorite youtube channel! Awesome work!

[@jensschroder8214]

Some rail vehicles have tires, for example trams have a rubber ring in the steel wheel. On June 3, 1998, an express train equipped with wheel tires had an accident in Germany. Wikipedia Eschede train disaster The rubber ring in the wheel had caused cracks in the steel tire, high speed, a broken crack, a switch and then a pillar of a bridge led to the catastrophe. The front locomotive and the first car still passed under the damaged bridge. But all the other wagons and the rear locomotive collide with the collapsing bridge. Afterwards, this technology was removed from express trains. The train line was initially shut down and later modified.

[@Derkiboi]

Seems to be the exception to the rule

[@jensschroder8214]

On October 19, 1875, a steam locomotive derailed in the Timelkam railway accident in Austria due to a broken steel wheel tire. Since the coupling broke off, the rest of the train remained on the rails. There was only material damage. The reason was probably that the connections between material strength and brittleness had not been researched.

[@jensschroder8214]

@@Derkiboi Engineers try new concepts. This sometimes goes wrong. In the Enschede case, wrong decisions were made by many responsible people. And then all the bad luck came together. The court could not find the one culprit, but spoke of the failure of many. Ultimately, everything boiled down to monetary payments to those who were in the accident.

[@jamesthemaniac3293]

Because friction…though the Paris Metro would like a word!

[@krissp8712]

Yeah the métro is unique! They planned for lots of hills I think. Good design and planning keeps railway routes flat and straight.

[@kaiserruhsam]

and notjustbikes talked about one in canada recently

[@rayfridley6649]

What about roller coasters, which also use tracks?

[@LMacNeill]

"... I have a couple of demonstrations set up in my garage..." Well, that *is* why I'm here. 🙂 Seriously, your practical demonstrations make these concepts *so* much clearer. Thanks for going to all that trouble!

[@lupuszzz]

Your models get better and better! I particularly like the bearing of the shaft for the brush and how the brush was neatly clamped with an external thread on the shaft - almost ready for series production ;-)

[@TheDavidlloydjones]

Locomotives have steel, rather than rubber, tires because steel is much more elastic than inflated rubber. This means the losses to heat from compression and rebound are much less from the flexing of the steel than they would be from rubber undergoing the same stresses.

[@DB-thats-me]

Finally, someone else who knows train wheels have tyres. Granted most railways are moving to solid wheel systems, but wheel and tyre still exist. Just as rubber tyres come in different compounds, steel wheels are no different. ‘Hard’ tyres last longer but are hard on the outer rail on curves. ‘Soft’ tyres are more gentle on curves but easily get flats if the get into slides. The balance between the cost of maintaining the track verses more regular re-turning the tyres.

[@Poverty-PonyTony]

TL;DL Reduced friction, equals reduced drag. Each wheel contact is less than the size of a US dime

[@Pottery4Life]

Thank you for the discussion between dynamic and static friction.

[@jovetj]

Thank you Grady, this is such a great series!!

[@champignonsmagiques]

Welp. These "formula 1" cars sure as hell were not ...

[@kenzokenzo]

lmao fr

[@arthurmario5996]

well, what were they??

[@jamesreilly5822]

2012/13 Indycars at the very beginning and f4 cars at 0:07

[@Derkiboi]

They mentioned f1 licence footage was the issue. Nonetheless it doesn't affect the video's primary topic on wheels and traction

[@kngofbng]

​@@Derkiboi But it affects the perception of a mistake being made.

[@skeetrix5577]

everybody should know why trains dont use tires lol is this really a serious topic?

[@TheBlazeofSteel]

A lot of people yes, but what about children or those who haven't come across this before. There are also a lot of places in the world with poor education.

[@jamesengland7461]

When you're teaching the fundamentals, it's better to not leave too much out.

[@merickful]

​@TheBlazeofSteel It was a rhetorical statement, and no reply would change their opinion.

[@rpm6085]

Grady, we love when you ‘get into all that’ complexity!

[@Burkhart4192]

Some trains DO have tyres! The derailment at Eschanade in Germany was caused by an ICE (inter city express) train fitting with dual block wheels, meaning they had a layer of rubber followed by a second layer of steel over the wheel. This provided some cushioning to the wheels, minimising sound and vibration before the invention of continuously welded rail. However, poor/nonexistent maintenence led to the outer layer of steel coming loose and getting stuck in the train body, and forcing a derailment when it encountered a junction.

[@cr10001]

That was an unusual design. The majority of wheels (that aren't monoblock) have steel tyres shrunk direct onto the steel wheels. This was universal for steam locos, and probably a majority of diesel/electric locos in Europe. The derailment was at Eschede, by the way.

[@kamakaziozzie3038]

You ARE correct Sir!

[@Elenesski]

Yay! Another wonderfully produced Practical Engineering video :) Made my day!

[@hardlyb]

Love the videos. I've been subscribed to Nebula for a long time, but I rarely go there, because when I start watching, I never stop.

[@realaccount2000]

I know there's an intuitive component to creep, but having it explained this way helps me understand much much more. Thanks Grady!

[@gino.avanzini]

Love to hear that Practical Construction is coming back!

[@meatywarrior6266]

I love this channel so much. Keep up the good work!

[@suzil7687]

Thanks for this video - and your promo of nebula is the first time the commercial (and service) appealed to me - and I've heard it from a ton of my KZbinrs. Signing up now. :)

[@kanadakid147]

I'm so excited about the rail water combo video coming out!

[@tunglam5113]

thanks for sharing as always

[@codediporpal]

Love this channel. You answer questions I didn't even know I wanted the answers to!

[@ScumfuckMcDoucheface]

5:35 I really wish you would "get into all that" man =) that's exactly why we're here! Thanks man, I've always really, really enjoyed your truly fantastic channel. Hope all is well in your world man.

[@rogerbeck3018]

BRILLIANT work Grady, thank you. Educational and entertaining

[@johnhuldt]

Another amazing video. Thank you for all the great content.

[@CONNELL19511216]

When I was very young we lived near railway tracks. At that spot we were near the top of a notable incline. I well remember the struggles of locomotives to pull their loads, particularly as they were nearly all steam driven in those days. In rainy weather they often didn't make it, and the loco's wheels would spin up in a frenzy of rapid and loud huffing and puffing

[@Sabelzahnmowe]

Fascinating Video. Thank you

[@mikezerker6925]

I love your channel and the garage demos!!

[@J3scribe]

Nicely explained, Grady. Steel on steel also offers lower rolling resistance for non-powered wheels, which has contributed greatly to longer trains with more tonnage.

[@tomedgar4375]

Not what I expected from the video name, Steam locomotives had replaceable steel tires. The concept of the steel surface stretching creating creep is fascinating.

[@somebody700]

The more I learn about trains the more I love them. The main reason behind using steel-on-steel and worrying about that friction is, well, efficiency. When the problem is "not enough friction" it means you are bordering the maximum efficiency you can get in land transportation outside of the locomotive aerodynamic design. The most efficient trains can be as efficient as container ships, which are famous for their max efficiency in transportation. A semi-truck is about 10-15 times less efficient in moving weight compared to an average train, and those figures can be as bad as 50 times less efficient.

[@tommy2u]

Grady's presentations are always so interesting and informative helping us understand things in ways we never imagined. Thanks for sharing. :D

[@gaveintothedarkness]

really loving this series!

[@jondukesofhazzard]

6:23 What the heck is that design. Lol. I love it. Its like a diesel but with a smokestack. Reminds me of a switcher unit. Love the video btw.

[@seb2721]

So excited for the new practical construction series!

[@uncipaws7643]

3:28 Friction isn't a horizontal line, it's actually sloping down as approximated by the Curtius-Kniffler formula. At higher speeds you don't have the same adhesion as you have at standstill.

[@lesalmin]

A sophisticated creep control system. I would have often needed that in my life. 🤔

[@Ihatejoebanks]

Hell yeah!!! More Practical Construction!!!

[@seanfitz1234]

excited for the new practical construction series!

[@RetroJack]

I don't often say this about people, but every trip to Grady's garage is a good one!

[@stevem268]

a fascinating series!

[@eitanormand]

Grady, I can't tell you enough how much I enjoy your content. We are your people!💪

[@PacificBird]

Another thing to mention about the steel on steel design is that more flexible materials like tires physically squish under weight, and all the energy that goes into squishing the tire is energy not converted into forward motion. This is one of the reasons why semi trucks are so unbelievably inefficient when compared to cargo rail for moving the same weight.

[@grgfraiser]

Hey Grady, love your work. I would love to see you do a series on drinking water infrastructure like your sewage pump station work. So many places here in the US without clean drinking water.

[@DakarNick]

Awesome! As a locomotive engineer I really enjoy your train videos!

[@macedindu829]

Steel is such an amazing material. Just on its face, it's amazingly versatile, but when you think of rails that trains drive on, it's really mind-boggling what it can do.

[@sarcasticguyz6251]

Im no engineer but i follow Brady and the way he presents these videos with graphics, simply amazing

[@ingolifs]

11:37 You can see the Helmholtz waves in the vibrating violin strings. Strings that are being drawn by a bow don't oscillate like a sinusoid as you'd expect. Instead they vibrate as a triangle wave with a moving apex called Helmholtz waves.

[@MixedGoku]

Lovely videos this is exactly what I love to see in the morning

[@AbuInsights]

I love all your content, i know it takes alot of time and effort to put it together in such an easy engaging way , thank you. Have you ever considered adding some chemical /biochemical engineering side into it?