5 ms·

> 131.4-liter, single-turbo diesel V12s making some 1,950 horsepower I'm sure this engine has been optimized for different factors, and it's likely a fairly ol

by harg 6y ago

> 131.4-liter, single-turbo diesel V12s making some 1,950 horsepower I'm sure this engine has been optimized for different factors, and it's likely a fairly old locomotive, but that's about 14hp/litre which seems pretty inefficient. Modern diesel cars can usually get >60hp/litre.

marshmallow_12 6y ago
i think the engine is optimised for torque not raw power. BUT... 1950hp..? There are cars with more power! How is it enough to pull 1000 ton trains at any speed? Any engineers here?
- Ensorceled 6y ago
  It's torque. If you see a freight train starting up it is excruciatingly slow to get going. Also, rolling stock has a lot less friction than trailers/cars with tires; so once up to speed, a lot less hp per pound is required to maintain that speed compared to something like a semi trailer.
- metiscus 6y ago
  The only production cars reaching anything like that power level are electric super cars. As to how it works: rolling resistance. A typical coefficient of rolling resistance for a railcar is somewhere around 0.0015. Let's guess that a typical train is somewhere around 5000 tons so you only need to be able to exert 8 tons of pulling force to accelerate that train.
- jeromenerf 6y ago
  TLDR: HP = torque x RPM / 5252 Such big engines runs at low RPM, below 1000 (I have not looked at this particular model). It's common for boats to run at 500. In comparison, my 2.2 liters 2007 diesel mercedes runs at around 2400 RPM at cruising speed of 65mph, which is its max torque. Max HP (150) is achieved at 3500 RPM. It's by no mean a sporty car but it's low RPM torque allows to pull the horse van easily. The freight carrier boats can feature impressive diesel engines, of thousands of liters, producing millions of Nm of torque, hundred of thousands of HP, at ~100RPM.
  - marshmallow_12 6y ago
    so the goal here is to minimise revolutions per minute. Is this to increase stability or efficiency? Or is it just so the engine won't shake itself to pieces?
    - lmm 6y ago
      The engine is probably designed for fixed RPM, because that way it can be tuned specifically to that RPM. High RPM (past a certain reasonable level) makes all the mechanical engineering harder, so you'd choose a level that's high enough for the power you need, but no higher. There's a tradeoff because to increase power you can either increase the RPM or increase the physical size of the engine, so you do whichever is easier based on the constraints of how it's being used.
    - jeromenerf 6y ago
      It’s always a trade off of many dimensions. Usually, if you are looking at resistance (pulling weight, navigating water, ...) more than speed, a bigger and slower engine provides the torque you want at low engineering costs, more resilience, less cooling constraints ... For some cultural reasons, American muscle cars featured big relatively slow but torquey engines compared to their Italian counterparts.
- Symbiote 6y ago
  The video at the end of this page, and the discussion before it, show how little force is required to keep a train moving. A very strong man can move a 70-ton locomotive: https://www.nscale.net/forums/showthread.php?26818-Could-an-adult-push-a-real-rail-car-on-a-level-track https://www.nscale.net/forums/showthread.php?26818-Could-an-... Or a person can start a single rail vehicle moving using a lever under a wheel, by hand: https://www.aldonco.com/store/p/198-Manual-Car-Mover-with-guard.aspx https://www.aldonco.com/store/p/198-Manual-Car-Mover-with-gu... Using one: https://www.youtube.com/watch?v=7W8c_jMVYAs https://www.youtube.com/watch?v=7W8c_jMVYAs
- bluGill 6y ago
  There are cars with more power, but that engine can deliver 1950hp all day without stopping. Try to pull that much power out of a car and it will overheat / self-destruct in a few minutes. Which isn't a problem for a car because at that power output you are at the maximum speed in a few seconds and then back off to more normal output. The engineers could get 10x more horsepower out of that engine, but the customers don't want that because the engine wouldn't last as long and so it isn't cost effective overall.
- johnwalkr 6y ago
  Well, they can be 6,000hp or more depending on the model. And 20,000 ft-lbs of torque. The actual torque at the wheels might be much higher or lower because there is not a mechanical transmission, there's a generator and electric motors called traction motors and like most motors they have peak torque at slow speeds. You can probably look up the output of those. The engines are designed for running at peak power for a long time, which a car engine cannot do. They run at a low rpm and last 30 years; millions and millions of miles. They run on low quality fuel. There's basically no weight constraint, in fact locomotives are required to be really heavy for the sake of wheel friction. Finally, most power is needed at startup, not for maintaining speed. One locomotive can't actually pull an entire fully loaded train from zero. There is slack between each car, and they are accelerated from zero one by one, from front to rear of the train.
lmm 6y ago
That's displacement, not fuel. It's running at low RPM and likely significantly more fuel-efficient than a car engine. You could make an equally powerful engine with lower displacement (by building it to run at higher RPM), but that would likely be a much less efficient engine; car engines have to do that because they have to be physically small, but that's not such a problem for rail engines.

by harg 6y ago

marshmallow_12 6y ago

i think the engine is optimised for torque not raw power. BUT... 1950hp..? There are cars with more power! How is it enough to pull 1000 ton trains at any speed? Any engineers here?

Ensorceled 6y ago
It's torque. If you see a freight train starting up it is excruciatingly slow to get going. Also, rolling stock has a lot less friction than trailers/cars with tires; so once up to speed, a lot less hp per pound is required to maintain that speed compared to something like a semi trailer.
metiscus 6y ago
The only production cars reaching anything like that power level are electric super cars. As to how it works: rolling resistance. A typical coefficient of rolling resistance for a railcar is somewhere around 0.0015. Let's guess that a typical train is somewhere around 5000 tons so you only need to be able to exert 8 tons of pulling force to accelerate that train.
jeromenerf 6y ago
TLDR: HP = torque x RPM / 5252 Such big engines runs at low RPM, below 1000 (I have not looked at this particular model). It's common for boats to run at 500. In comparison, my 2.2 liters 2007 diesel mercedes runs at around 2400 RPM at cruising speed of 65mph, which is its max torque. Max HP (150) is achieved at 3500 RPM. It's by no mean a sporty car but it's low RPM torque allows to pull the horse van easily. The freight carrier boats can feature impressive diesel engines, of thousands of liters, producing millions of Nm of torque, hundred of thousands of HP, at ~100RPM.
- marshmallow_12 6y ago
  so the goal here is to minimise revolutions per minute. Is this to increase stability or efficiency? Or is it just so the engine won't shake itself to pieces?
  - lmm 6y ago
    The engine is probably designed for fixed RPM, because that way it can be tuned specifically to that RPM. High RPM (past a certain reasonable level) makes all the mechanical engineering harder, so you'd choose a level that's high enough for the power you need, but no higher. There's a tradeoff because to increase power you can either increase the RPM or increase the physical size of the engine, so you do whichever is easier based on the constraints of how it's being used.
  - jeromenerf 6y ago
    It’s always a trade off of many dimensions. Usually, if you are looking at resistance (pulling weight, navigating water, ...) more than speed, a bigger and slower engine provides the torque you want at low engineering costs, more resilience, less cooling constraints ... For some cultural reasons, American muscle cars featured big relatively slow but torquey engines compared to their Italian counterparts.
Symbiote 6y ago
The video at the end of this page, and the discussion before it, show how little force is required to keep a train moving. A very strong man can move a 70-ton locomotive: https://www.nscale.net/forums/showthread.php?26818-Could-an-adult-push-a-real-rail-car-on-a-level-track https://www.nscale.net/forums/showthread.php?26818-Could-an-... Or a person can start a single rail vehicle moving using a lever under a wheel, by hand: https://www.aldonco.com/store/p/198-Manual-Car-Mover-with-guard.aspx https://www.aldonco.com/store/p/198-Manual-Car-Mover-with-gu... Using one: https://www.youtube.com/watch?v=7W8c_jMVYAs https://www.youtube.com/watch?v=7W8c_jMVYAs
bluGill 6y ago
There are cars with more power, but that engine can deliver 1950hp all day without stopping. Try to pull that much power out of a car and it will overheat / self-destruct in a few minutes. Which isn't a problem for a car because at that power output you are at the maximum speed in a few seconds and then back off to more normal output. The engineers could get 10x more horsepower out of that engine, but the customers don't want that because the engine wouldn't last as long and so it isn't cost effective overall.
johnwalkr 6y ago
Well, they can be 6,000hp or more depending on the model. And 20,000 ft-lbs of torque. The actual torque at the wheels might be much higher or lower because there is not a mechanical transmission, there's a generator and electric motors called traction motors and like most motors they have peak torque at slow speeds. You can probably look up the output of those. The engines are designed for running at peak power for a long time, which a car engine cannot do. They run at a low rpm and last 30 years; millions and millions of miles. They run on low quality fuel. There's basically no weight constraint, in fact locomotives are required to be really heavy for the sake of wheel friction. Finally, most power is needed at startup, not for maintaining speed. One locomotive can't actually pull an entire fully loaded train from zero. There is slack between each car, and they are accelerated from zero one by one, from front to rear of the train.

lmm 6y ago

That's displacement, not fuel. It's running at low RPM and likely significantly more fuel-efficient than a car engine. You could make an equally powerful engine with lower displacement (by building it to run at higher RPM), but that would likely be a much less efficient engine; car engines have to do that because they have to be physically small, but that's not such a problem for rail engines.