Why Railroads Don't Need Expansion Joints

🎅There's still time before Christmas to pick up an infrastructure bingo pad or a shirt at store.practical.engineering/ 💡 Check out Brilliant for the best way to learn math and science skills: brilliant.org/PracticalEngineering

As a civil engineer, this type of content is therapy

"Stress is what breaks things" is a truth that more people should apply to their own lives

My 14 yo son was telling me about metal expansion he'd learned about in school and we got onto the topic of railroads. I mentioned they don't really put railroad down in sections anymore and he asked how they accounted for expansion. I realized-- I had no idea! So thank you for this great video-- I now know.

As a trained metallurgist and engineer, I found this amazing.... what a way to encourage future engineers, Simply, softly spoken.

As a engineer who works in railway track design, one thing I'd like to point out - especially since you mentioned a video on signaling will be coming soon - is that neutral temperature is typically high not because a broken rail is less dangerous than a sun kink. Yes, its more likely that a train could operate over a pull-apart rather than theough a sun kink, but largely because the signal system will detect a pull-apart as a discontinuity in the rails and thus the signal circuit - automatically turning the signal ahead of that track to red!

I love that the primary solution for buckling is just “do it on a really hot day lol.” It’s the kind of thing that sounds way too dumb to work but is somehow the most genius solution ever.

Builder here. South Florida. I never understood why rail work here was always done in the summer heat! Thanks for clearing that up. We never see rail work in our “winter”.

I really enjoyed this video! Well done!

Railway engineer here! A few points: Not all rail is made of the same alloys, particularly high load areas such as points and crossings. These use harder metals to reduce wear, such as manganese. Adding this into the equation means welding plain line to p&c is a particularly complex job. I am also glad you mentioned track circuit will be covered later on as that is a big downside to CWR with older signalling systems. Aluminothermic welding is spectacular when it goes wrong, search it up!

Fun fact: The problem with 'rock n' roll' (more formally, harmonic rocking) is bad enough that rulebooks disallow travelling at certain speeds on jointed rail. The rulebook I have says this danger zone is 13 to 21 mph, so if your train only has enough power to reach 20 mph (entirely possible, if normal, these days) safety says you'd have to slow to 13 mph on jointed rail. So CWR not only makes maintenance-of-way's job easier, it also makes operating the trains a bit easier and safer too.

As a medium carbon steel rod I find this content traumatic.

People get stressed sitting at a crossing waiting for the train to pass by because they have places to be. I get that. Me, I marvel at the engineering that isn't seen by the casual observer. The whole system from concept to application is mind blowing and has more facets that a jewelry cut diamond. Always enjoy your videos.

If anyone wonders why the odd figure of 39 feet was the standard length of single sticks of traditional jointed rail, it was so that they'd fit into 40-foot gondola cars. Welded rail is now typically manufactured in long lengths (1,320 feet in the USA, which is ¼ mile) and can be welded in the field to be continuous. Such long rails are transported on special rail trains, like the one Grady shows half-loaded at 0:25. The yellow racks hold them in place, and the rails bend as the train goes through horizontal and vertical curves 😮

This is the first question I ever asked on the “internet” - a Compuserve message forum - back in 1989, and it was answered by a Canadian rail worker. That’s when I knew we were in a new era.

as a non-engineer minded person just wanted to say thank you for making this very easy to digest and understand. i truly appreciate learning from people who are able to follow the KISS rule lol

If I remember correctly, what my associates in the track department told me is that in the Northeast where we are, they had to lay the rail at a certain temperature range. This is to mitigate the expansion and contraction which happens in our area because of the swings in temperature across the seasons. When our company was bought out, the new owners decided to lay rail in freezing temperatures and they ended up paying the price. Obviously, in Florida, as you mentioned, they lay the rail at a high temperature for a reason. My knowledge of rail only encompasses running my trains over the tracks and also how the shape of the rail works. Your video was very interesting and informative.

I developed a broken rail detection system at San Francisco BART that used ultrasonic waves traveling miles in the continuously welded rail. As part of characterizing the rail I measured acoustic properties as a function of rail temperature. It was amazing to see the rail temperature exceed 140 degrees F on medium hot days, like air temperature in the 90’s. The peak temperature was in the late afternoon when the rail web caught most of the sunlight. Definitely painful to touch!

Rail is fascinating. I never considered that (fundamentally) you could just hold it in place and force it to not thermal expand and the stress isn't always prohibitively high.

While studying mechanical engineering in college and now as an actual locomotive engineer for a commuter railroad, this is great information and very well presented. I’ve witnessed CWR being installed but your explanation of installing rail at its warmest neutral temperature makes perfect sense! Indeed, a rail pull-apart is much preferred over a heat-kink, not only from a rail perspective, but also the cab-signal code will drop to zero in a broken rail but may still function normally during a heat-kink which could be disastrous.