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2,395,768 Views • Oct 3, 2023 • Click to toggle off description
Errata: At 6:52, the graphic should show the dimension of the wheel's diameter (not radius).
In the 19th century, railway engineering was all about how to build railroads. Modern rail engineering focuses on getting the most out of the system. It might not look like much when you see a train passing by, but a huge amount of research, testing, and engineering went into the shape of those rails and wheels.
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Video by Grady Hillhouse
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Views : 2,395,768
Genre: Education
Date of upload: Oct 3, 2023 ^^
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RYD date created : 2024-05-07T21:59:52.561227Z
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YouTube Comments - 2,164 Comments
Top Comments of this video!! :3
I'm a retired 73 year old mechanical engineer (stress analysis) also with an electrical engineering degree (computer & SW). I enjoy Grady's videos of civil engineering and related subjects and learning yet more engineering I used to ignore or take for granted. Never too late to learn even more. Thanks Grady!
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The issue about hunting behaviour is really interesting because it comes up in downhill skateboarding as well where they refer to it as "speed wobble" and have some interesting ways of combatting it
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What a masterclass in detailed and efficient science communication! Your script-writing is off the charts to pack so much into 15 minutes without it feeling overwhelming. The delightful animations and physical models make it so digestible, even for a total newcomer.
You're the best, Grady! 🙏✨
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As a steel worker at a rail mill this was very interesting & cool to get better insight on the workings of the stuff we make.
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I love the way Grady builds mock-up models to help explain what he's discussing!
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I was just in Japan and rode the bullet train and I noticed how the top of the rails was rusted over except for one tiny strip down the middle where the wheels actually contact it. Impressive precision for them to let the train go 200mph!
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4:30 That whole wheel segment was FASCINATING.
As a kid, we lived in a house that was three houses from the tracks, so I've heard all the various noises you describe since being a youth, plus the schwing-squeak-schwing sound you mentioned.
And just today, 50 years later, I'm learning why. 👏👏
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In the Netherlands, train wheels have "tires" (also made of steel, of course) that are replaced regularly to combat wheel wear without having to take off the wheels. I guess this is true in other places as well.
The tires are slightly smaller than the wheel, and are heated before mounting so that the stress will firmly keep them put.
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I was an electrical engineer on a project at Griffin Wheel where they make some train wheels. There is a lot that goes into each and every wheel. One of the most interesting projects I got to work on.
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My grandfather was an Engineer for Santa Fe. He started as a Fireman on the ATSF (Atchison Topeka Santa Fe) 3751, a 4-8-4 steam engine when he was 16. He eventually worked his way up the ranks to Engineer. He also went to college and got a degree in Mechanical Engineering along the way, too. That's why I am obsessed with trains. I miss him. He was an awesome guy.
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Fifty years ago my young son became a rail fan, and I developed an interest alongside of him. I'm still fascinated with the complexity of how railroads work, and the incredible cost-per-ton efficiency of the system. I know there's basic physics involved, but it's still magical to me how an engine set can get a huge freight train in motion from a dead stop. Thanks for this great video.
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One of my most interesting experiences learning about trains was when I was touring England and stopped in at the National Train Museum in York. Wow! Just wow! I was so lucky to find a volunteer that really knew his stuff and was willing to spend an hour with me. We started with a longitudinal section of a real steam engine, and he explained how these trains were powered. When he got into the engineering behind the power transmission to the wheels, my jaw hit the floor. If you think it's appropriate, please consider covering these topics. There is some fantastic engineering involved. Better yet, go to York. Find a great volunteer and give us video tour of the museum. 🙂
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I feel like we take for granted a lot of the engineering and design work done in seemingly simple objects and tasks. Awesome vid btw!
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I think one of the factors why trains are so impressive in general is, where else do you see something with the weight of a house move with speeds up to or even above the speed of cars on highways?
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Here in London, they've just opened the Elizabeth Line which also has a bunch of brand new rolling stock. I swear every time I'm on the new section of rail in a new train it feels like a flying carpet. Accelerating up to speed with just a whistle, and a ride that is smooth as butter. Just boggles the mind how they can get 1000 tonnes of steel on steel interacting like that.
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As a kid who lived near railroad tracks, we "played" with the contact patch between the wheels and rails. The train that went thru our neighborhood had to come to a complete stop before crossing an old bridge over the Hudson River. At that moment we'd place coins and other objects under the wheels to see if would flatten or crush them. It resulted in some cool oval shaped coins but mostly crushed and destroyed everything else. Yes I know this was very dangerous behavior but kids in the 1950's & 60's took a lot more risks than children do today. We didn't have video games, we had to seek our entertainment outside in the real world.
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There are three items about the rails that need to be mentioned. First, the rails are not flat on top. The apparent flat surface is actually a gentle radius. Previously it was a 10" radius, new rails are now manufactured with an 8" radius across the head. This, in conjunction with the second item, called cant, keeps the wheel contact patch centered on the rail head.
Cant is induced by the tie plates that support the rails. The plates are flat on the bottom where they bear on the crossties, but the seat that supports the rails is slightly tilted to the inside at a 40:1 pitch. This tips the railheads inward about 1/8" each from a true 90 degree angle to the crosstie.
Third is superelevation. Raising the outside rail to bank the track slightly in curves. In track designed for really high speed running the difference in elevation between the inner and outer rail is as much as 6". This effect also helps the tapered wheel treads self center at speed and keeps the flanges from dragging on the high rail. Excess superelevation where trains are not running fast enough to use it is a disadvantage. Now the low rail receives excess weight and wear. In fact trains can actually tip over at a stop if they are carrying top heavy loads.
Another interesting item is, that despite their huge imposing appearance, the center of mass of a locomotive is actually only about 5' to 6' above the railheads, which are set at standard gauge, 56-1/2" measured 5/8" down the railhead. This gauge dimension puts the webs of the rails at just about 5' even, which varies only slightly depending on which size rail is being used. All the really heavy parts are down low.
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Speaking of wheel rail interfaces one of the more unusual faults I've seen was caused by a loco having a slightly different contact patch to the normal EMU that ran on that track. Because it wasn't touching the narrow unrusted part of the rail head the rust was acting as an insulator and preventing activating it the track circuit's consistently.
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The "hunting" phenomenon reminded me of something that would probably make for an interesting episode idea for you: trailer design and loading.
In a game called Space Engineers, I've built a lot of trucks and trailers of various types for hauling things, and it's taught me a lot about how trailers behave with different designs and load distributions. One of the things I've had to deal with has been similar to "hunting" where, when going downhill, my lack of ability to implement trailer braking causes the trailer to push on the truck. This tends to try to turn the truck, so I steer to correct. Once that steering turns the truck back to the balance point, the forces suddenly flip and I have to correct my steering the other direction. This tends to lead to a progressively violent lashing side to side and can lead to rolling the entire truck and trailer if I'm going too fast for my load or don't reach the bottom of the hill before the progression gets out of hand. It behaves like balancing a stick on end (with the truck being the stick). It's easy for the system to go out of control. All sorts of different hitch methods, trailer designs, and trailer loading can lead to stable or unstable systems. It's a really interesting topic to explore.
That same game has been pushing me towards becoming a railfan, too. I once tried to design a train, and hours and hours of different designs led me to having a truck on each end of each car. I was still having trouble at that point so I started looking up actual trains to get design inspiration. I found it really cool that my own designs so closely resembled reality. My train attempts in the game were eventually stifled by having to admit that the game can't handle the complicated physics when the train gets up to practical speeds, but it's left me with a bit of a craving for trains.
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7 months ago
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