this post was submitted on 16 Mar 2025
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Why didn't oil fired steam locomotives take off? (lemmy.ml)
submitted 1 day ago by doomsdayrs@lemmy.ml to c/asklemmy@lemmy.ml
14 comments fedilink hide all child comments
 

A steam locomotive is known to be able to pull more then any pure combustion engine locomotive. (Uncited)

Why didn't oil fired steam locomotives take off?

This started when I watched: https://www.youtube.com/watch?v=Hszu80NJ438

During the runtime, it mentioned oil fired retrofits.

I search it up, and found one.

It was an overview video of a modern retrofit, and it seems to not be too difficult to retrofit, even using the same steam blaster to spread the oil in the smoke box: https://www.youtube.com/watch?v=Up1UaMVnv4M

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[–] toadjones79@lemm.ee 6 points 23 hours ago

They did. Diesel steam was the main source of steam over time. Coal was used for a relatively short period of time. Wood for even shorter before that. Jupiter (the engine from Central Pacific that met I. That famous photo of driving the Golden Spike on the Transcontinental Railroad) was wood fired while it's Union Pacific counterpart was more modern, and coal fired. But my grandad ran Diesel Steam his whole career.

Today there isn't much nostalgia for Diesel Steam. So a lot of the working museum pieces are coal fired. I can't remember if Big Boy, from UP, is diesel or coal. I think it's diesel though.

I'm a railroader not a foamer.

[–] jordanlund@lemmy.world 21 points 1 day ago (3 children)

My GUESS, and I have no knowledge of this, but my guess is using oil to generate steam is less efficient than simply running a diesel engine.

Oil -> Steam -> Drives Engine
Diesel -> Drives Engine

[–] aedelred@lemmy.world 22 points 1 day ago (1 children)

I assume it has a lot to do with efficiency, and correct me if I am wrong, but I think it goes Diesel -> Generator -> Traction Motors

[–] NABDad@lemmy.world 18 points 1 day ago (3 children)

You are correct. It relates to the torque (rotational force) that can be produced at different RPM.

Diesel engines have a narrow range of RPM where the torque is highest. At low RPM, the torque of a diesel engine is low. That's why trucks have to shift into a low gear to start moving and shift multiple times to get up to speed. The driver uses the different gears to keep the engine running within the optimal range of RPM.

Electric motors have high torque at low RPM, so they can start a heavy load moving without having to have any complicated gearbox between the motors and drive wheels.

In a diesel-electric locomotive, the diesel generator can be designed to run at an efficient speed without being affected by the mass of the train. The electricity it generates powers the electric motors which have the necessary torque to handle moving the train.

[–] aedelred@lemmy.world 3 points 1 day ago

I'm always interested in learning stuff and your short but detailed explanation rocks! Thanks and keep up the good work.

[–] TBi@lemmy.world 4 points 1 day ago (1 children)

I always wondered why trucks didn’t become diesel electric or have a Prius style drive train (with diesel engine). Would be a lot easier to drive.

[–] superkret@feddit.org 4 points 23 hours ago

A gearbox is much smaller and lighter that what's required for a diesel-electric setup.
Diesel-electric is used for big engines in ships and railroads, where the necessary torque would destroy a gearbox.

[–] JustAnotherKay@lemmy.world 8 points 1 day ago

Electric motors have high torque at low RPM

For anyone scrolling by and curious about this, this is caused by the combination of physical and electrical resistance. In a typical engine, RPM and torque go up together because it requires more force to get to those higher RPMs (IIRC this is called positive correlation). In a circuit, you have to kind of convince the electricity that it would be better off somewhere else (by connecting to a ground, this is due to electrical resistance), so you have to give it a heavy upfront load to get it going which causes a lot of torque due to the physical resistance

[–] ArchAengelus@lemmy.dbzer0.com 9 points 1 day ago (1 children)

That’s definitely part of it. Also not an expert, but I believe you have the gist of it. Diesel engines are more efficient for a couple of reasons, not the least of which is more efficient heat capture to use for Work.

Another factor would be that if you want to do an oil combustion into steam power, you have a few issues:

  1. You now have to lug around a LOT of both fuel and water, instead of just water and dry coal. Water and oil are both heavy by comparison to coal when lugging a train car of it around.
  2. you now have two areas for heat loss to happen. Steam engines require massive boilers, high heat, and run much greater worst case failure risks (I.e. explosions) which are at highest risk when the water runs out. Coal is worse for this than I imagine oil would be, though inertia is a powerful force. Why move to another complicated system that does the same thing when you can use the old one?
  3. Supply lines and training: if coal is already managed logistically, why switch to something else that provides a marginal benefit when coal is both cheap, easily accessed, and your engineers already know how to use it?

I’m sure there are even better reasons out there, but that’s what comes off the top of my head.

[–] NABDad@lemmy.world 6 points 1 day ago* (last edited 1 day ago)

You now have to lug around a LOT of both fuel and water, instead of just water and dry coal. Water and oil are both heavy by comparison to coal when lugging a train car of it around.

I think you're making an assumption there. You would need to consider energy density of the fuel. Diesel fuel has almost twice the energy density of coal. For the same trip, the weight of the diesel fuel you would need for an oil-fired steam engine would be just a little more than half the weight of coal needed for a coal-fired steam engine.

Also, delivering the diesel fuel to the boiler would require a less complex mechanism and/or less workers than coal.

[–] AlternateRoute@lemmy.ca 4 points 1 day ago

I don't even need to do the math, you would have two liquids, one you are boiling for steam and one you are using for fuel.. Replace that ALL with fuel..

[–] HakFoo@lemmy.sdf.org 9 points 1 day ago* (last edited 1 day ago)

Oil burning was common in some regions. The Southern Pacific had a lot of oil-fired engines. Their famous "cab-forward" steam engines could only make sense as oil burners without fundamental redesign.

Part of it might be that the last holdouts for steam, who made the most technically advanced engines, were predominantly coal-carriers. They didn't have the oil infrastructure, and didn't want to burn relations eith their customers.

[–] davel@lemmy.ml 11 points 1 day ago* (last edited 1 day ago) (1 children)

They’re very heavy, have no wings, and once they get off the ground they lose propulsion.

[–] Azzu@lemm.ee 5 points 1 day ago

You are such a silly goose, I love it