Why Are Rails Shaped Like That?

Love spotting infrastructure? Pre-orders are still open for Infrastructure Road Trip Bingo! store.practical.engineering/ Love not shopping for groceries? Use code PRACTICAL16 at bit.ly/3Ws1PYm for 16 free meals with HelloFresh!

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!

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

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.

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! 🙏✨

Babe wake up! Practical Engineering posted 🥵

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

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.

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. 👏👏

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!

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.

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. 🙂

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.

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!

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.

Great video! I have been a railroad designer for about 7 years now and am always excited to see great railroad content. It’s an interesting industry that often gets taken for granted. Looking forward to the rest of the series!

I am one of those guys that doesn't mind waiting at a railroad crossing. I love the vibration of those huge diesel engines! The raw power is mesmerizing to me. Love your focus on the railroad lately!

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.

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?

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.