Yesterday a train passed by with like 40 train cars and I was astonished by how these trains can even move with that much cargo behind it. How is this even possible?
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Why it takes such a long time to get to speed and a long time to slow down. A shit ton of momentum helps keep it going and a very powerful engine. Also why the wheels have those things on the outside, it helps with the momentum
The strength of a motor or engine (something that does rotational work) is not just measured in how fast it can turn, but how hard it turns (torque). Goods locomotives produce a lot of torque to overcome the inertia of the loaded wagons and then work carefully with their momentum. They don’t like hills or unnecessary stop/starts. For really really long trains you can sometimes run several locomotives that work as a team, depends on the model and operator
Moving something fo not require energy, that is on a level surface. When you drive a car the engine is there to accelerate you to the speed you drive at. What it does is counteract air resistance and roll resistance.
Ar resistance depends on the shape not the weight of the object. How large it is alos depends on the speed you travel at, charge train tends not to go that fast. It is the front that has more air resistance because has to push air to the side. This will be an advantage if you compare a single train to 40 trucks that pull the equivalent of cart of cargo each
Roll resistance on the wheels and is a lot lower for steel wheels on steel tracks compared to pneumatic tires on a road.
The result is the power needed to overcome air and roll resistance is lower compared to the amount of cargo you transport of a train compared to a truck.
Locomotives alos have very powerful engines/motors. We talk about 1000-10000hp for the one used to transport cargo and you can have multiple of them. compare that to a semi-truck that is at around 500hp.
So the remains you observed could have an engine power of 20 semi-truck and have less rolling resistance.
The train has less engine power per tonne of total mass than a truck, this is why they accelerate quite slowly.
The end result is compared to the cargo a train needs less power to move it compared to a truck and the have engine with a power of many trucks
If you look at numbers for diesel-powered trains vs diesel-power trucks you find results like
>Rail fuel efficiency ranged from 196 to 1,179 ton-miles per gallon while truck fuel efficiency ranged from 84 to 167 ton-miles per gallon.
Trains use engines designed to provide massive torque while stationary.
Your car engine needs to spin fast to generate power, so it’s great at speed but terrible when stopped. You need a complex gearing system to generate any power at all when stationary, and messing up the transition just stalls the motor.
Trains use diesel-electric systems to turn the wheels with electric motors. These can generate enormous force even when the train isn’t moving at all, and that’s enough to get it rolling.
Old-timey steam engines used a similar idea – a steam engine is neither safe nor clean nor efficient, but it can generate tremendous power at a standstill with that steam pressure.
Once it’s moving, keeping it moving is trivial. The metal-on-metal wheel and rail design has very low friction and rolling resistance to a moving train will stay moving without much effort.
I used to think those diesel engines worked like truck engines until someone told me to consider the *clutch* that would be required!
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