I’ve googled it but just can’t seem to grasp it. How do they stay on as well as they do at such high speeds, with so few incidents of crashing or derailing? Especially when anything could be lying across the track waiting to get lodged in the wheels.
I hear so often that trains are so safe, but I don’t think I can get over my anxiety with them until I understand *why* they’re safe.
In: 29
1. Direction of force= direction of track. The railway engine apply force in one direction only. We don’t have any force in any other direction. The direction the engine can apply force is along the track only, called axial direction.
2. Inertia = weight of the train is so so so much. To derail a train, we need a force which is not acting axially, and we need a very large force as the inertia will stop it.
3. Rigid Body = Trains, specially wheels are solid metal and they can’t be bent of reshaped so easily. The wheels on both sides are clubbed together by a rod (called axel) and any movement in one is impossible without moving the other one. Think of the wheel on the both sides as rigid bodies. (They are just opposite of your car wheels, where one wheel can turn/travel at different speeds than the other)
While changing tracks/ turning etc, the railway engineers make sure that atleast one wheel alway stay on track, and as the second wheel is rigidly attached to the first one, the other wheel will stay on track too.
PS: I don’t have a source or quantitative information for this data, but the qualitative info is correct. If we compare the human lives lost/injured for per travel hour spend, for different modes of travel, cars are the worst (as they cause most deaths/injury, per hour of travel) and air travel is the safest mode of transport, railway is right next to air travel when it comes to safety.
Given the not so strict rules when it comes to railways, as compared to airline industry, this is pretty amazing.
On top of how the wheels work and the difference in masses, it turns out that it’s actually pretty hard to derail a train even when you remove chunks of track. The [Army ran tests during WWII](https://www.youtube.com/watch?v=agznZBiK_Bs) to figure out what was required to sabotage a rail line.
Other users have discussed how the wheels are shaped and how the weight keeps it on the tracks, but I wanted to add another bit of information to help soothe your anxieties (courtesy of my dad, who works for the railroad, though I took what he told me and translated it into ELI5).
Trains have a LOT of wheels. Like, a ridiculous amount of them. Each car has at least two sets of ‘bougies’ (which is a set of two axels connected to each other, so four ‘wheels’ in total per bougie), and some have way more than that (like engines, each ‘bougie’ has three axels instead of two, so six ‘wheels’ per bougie and twelve ‘wheels’ overall per engine). If there is something big lying across the track (like a car, or even a semi), it *might* knock the first set of wheels loose from the tracks. Maybe. But because there’s so many wheels and most things that lay across train tracks waiting to get hit by a train is significantly smaller than a full-length train, even if the first pair of wheels gets knocked off the rest can just continue doing their job.
The wheels are shaped like this –/ and the track is shaped like this |__|.
Since the train is really heavy, the wheels never slip out of the track. If the train takes a turn too fast well… even good design has its limits.
ELY5? It’s physics kid. Just enjoy the show or move on😅
People have mentioned flanges, and they help, but that’s a safety feature. If it touches the rail you get a nasty screeching noise.
Train wheels are conical section. If the train veers to the left, the left wheel is effectively larger which causes the train to shift back to the right.
Latest Answers