How do trains pull so much weight? I’ve seem them with hundreds of freight and gas tanker cars.
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It’s all about producing more pulling force than friction will hold you back. A single train car doesn’t produce that much friction, so in order to maintain speed, the engine just needs to match the amount of force that all friction.
In order to speed up (ie starting the train) it doesn’t actually pull the whole train at one, rather all of the train cars are scrunched together slightly so the engine starts, and it pulls the first car, then the second, then the third and so on so it doesn’t have to overcome the initial inertia and static friction of every car at once. Once the last car has started, the engine is already up to speed.
Hills are where trains have trouble. The maximum railroad grade in the world is 13.8%. The ideal maximum grade for a massive freight train is about 1.5%. This means that for every meter the train moves forward, it increases in elevation by 13.8 cm.
If a train does need to go up a steep grade, it gains speed before hand and uses that momentum to carry it up the hill. Freight trains are also long enough that most of the time they need to go up a hill, they aren’t bringing the entire train up the hill at the same time, rather they are pulling a fraction of the cars up, where as the majority of the train is level.
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