Why Are Rails Shaped Like That?

An overview of the wheel/rail interactions and part of the railway engineering series.
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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This is not engineering advice. Everything here is for informational and entertainment purposes only. Contact an engineer licensed to practice in your area if you need professional advice or services. All non-licensed clips used for fair use commentary, criticism, and educational purposes.
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Video by Grady Hillhouse
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[@j.electric]

Babe wake up! Practical Engineering posted 🥵

[@Door_Casts]

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

[@tlum4081]

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!

[@garou5333]

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.

[@KalebPeters99]

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.

[@fredsalter1915]

I love the way Grady builds mock-up models to help explain what he's discussing!

[@timmallette1888]

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!

[@josephgaviota]

4:30

[@jurjenbos228]

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.

[@Pufferish]

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!

[@drzman6901]

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. 🙂

[@SarahWRah]

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.

[@The1andOnlyWog]

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.

[@neildunhamii4069]

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.

[@fiddley]

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.

[@jamesdoyle5405]

I am a retired locomotive mechanic. Wheel measurements are so important, if the flange gets too low the car or engine can derail in a curve. Flanges that get too narrow can "pick" a switch and send a wheel set down the wrong track. Locomotive have flange lube sticks that lubricate the flange to slow wear. The other important measurement is diameter which needs to be close side to side. Really enjoyed this video explaining rail loads and design.

[@MsCriticalthinker201]

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.

[@BarredCoast0]

I'm really looking forward to more in this series. We railfans are always looking for more answers to unknown aspects of railway engineering. Thanks Grady!

[@timecowx]

My great grandfather had a piece of rail that he used on occasion when he needed something to serve as an anvil, which is a pretty common practice. I held onto that piece, keeping in in the shed or garage for years until I finally had a use for it. It was a rail that had obviously seen a lot of use in its day and since my use was would be better served by a nice flat surface, I took it to a shop to have it machined flat. The machinist said he had done a few before and he would just do it that afternoon and I could pick it up the next day. I was fortunate that he was stubborn (and kind) because when I went to pick it up he only charged me $20. I say stubborn because he said he broke three bits on it, and only managed to slightly improve the top of the rail. According to him he kept trying because he had never had trouble with one before, but he thought it had something to do with the age of my rail and it having seen a lot of use in its time on a track, compressing and hardening it over time. Now I'm wondering if it was one of the harder rail segments you mentioned they use on turns, though I don't know how long they have done that, nor do I know the age of my rail, so hard to know for sure. I just thought it was interesting (if true) that rails might harden as well as wear, over time.