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A somewhat significantly sized city is faced with a problem. It currently wants to reduce the smoke from the steam locomotives in the city & build more efficient & compact stations, however it doesn't have the money to electrify it's entire network. Diesels aren't that well established for anything yet in the region at a large scale & there have been bad prior experiences with diesel in the city so a bi-modal diesel isn't really considered in the first place.

So the question becomes how to make a locomotive capable of operating on both a coal or oil boiler or electricity. People have fiddled around with steam-turbine electric locomotives in this world & found out what we did in the real world about them (heavy, complicated, unreliable & expensive) so that isn't considered a viable option.

The locomotives must be able to run even if only at a limited speed & power on electricity alone without burning coal while still being able to run as well as standard suburban steam engines.

the technology available is roughly that of the early 1950s, both 3rd rail electrification & overhead wire electrification are considered viable however 3rd rail is preferred due to other operators in the region also using it. (yes i know diesels were getting quite good in the early 1950s but they weren't very proliferated yet)

What is the best operating principle for an efficient steam electric locomotive under these conditions?

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  • $\begingroup$ Commercial diesel electric trains from 1925. borail.org/collection/cnj-no-1000/…. $\endgroup$
    – Boba Fit
    Apr 21, 2023 at 13:20
  • $\begingroup$ @BobaFit i know those exist, but the city doesn't want diesels for various reasons $\endgroup$
    – OT-64 SKOT
    Apr 21, 2023 at 21:43

8 Answers 8

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The only way to be able to use at will coal, diesel and electricity is having the coal/diesel power a generator which supplies electricity to the electric motor, which then drives the wheels.

When you are getting electricity from power lines, you disengage the power generator and go on direct supply.

For the burning part of the engine, you have two options:

  1. following a steam locomotive design, you either burn coal or diesel to make pressurized water boil and produce the steam
  2. following an internal combustion engine design, you either supply diesel or pulverized coal as fuel for the engine

With the first option you would need to carry along water and fuel, while the second option allows you to save carrying around the weight of the water, since you use the expansion of the combustion gases to move the piston. However pulverizing coal adds a complication.

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Electrify ASAP

The most efficient way is to roll out electrified lines and engines as fast as it can be afforded to replace the steam engines. Banks supplying loans exist.

Centralized power plants will reduce fuel consumption due to be ing able to be higher efficiency. Approximate efficiencies.

  • Well designed steam locomotive 7-8%
  • Diesel are 25-30%
  • Coal fired power plant 30 - 40%

Quartering fuel consumption is pretty big savings. Electrical engines also have drastically lower maintenance then steam.

Upgrading will likely have have positive returns on investment within five years. Meaning getting banks to loan money for upgrades should be pretty easy for most lines.

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  • $\begingroup$ the problem with this is that el ectrical equipment costs a lot to maintain so unless there's a lot of use it's hard to recoup it's cost & the c ity doesn't really have the be st credit rating & a lot of debt already. $\endgroup$
    – OT-64 SKOT
    Apr 20, 2023 at 5:33
  • $\begingroup$ What make you think electrical equipment costs a lot to maintain compared to coal/oil? Because one of the benefits of goint electrical is the decrease in maintenance. And infrastructure itself isn't all that expensive. Steel is cheap. Banks would fund such project in a hearthbeat, as it is very profitable. $\endgroup$
    – Negdo
    Apr 20, 2023 at 15:03
  • $\begingroup$ @Negdo because the wires themselves & other associated equipment costs a significant money to maintain, if there's not enough trains running under the wires they don't make their money back, i don't know the exact economics of it but it's proved true for a very very long time, & in some cases early electrification actually increased costs overall. $\endgroup$
    – OT-64 SKOT
    Apr 21, 2023 at 21:45
  • $\begingroup$ That is not true? Power cables themselves require almost no maintenance, and electric engine has less moving parts (not to mention it operates at lower temperature) so maintenance there is lower as well. There is a good reason why everyone upgraded to electricity as soon as it was possible. $\endgroup$
    – Negdo
    Apr 24, 2023 at 6:44
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Frame Challenge: Folks' main concerns at the time was more about the lack of visibility, particularly in tunnels. Folks didn't like the smoke and steam either, but those were less important.

Smoke was something annoying you lived with everywhere, but visibility is what killed people...

Example: https://en.wikipedia.org/wiki/List_of_rail_accidents_(1900%E2%80%931909), emphasis is mine.

January 8[, 1902] – United States – New York City: A stopped New Haven express train from South Norwalk was rear-ended in the Park Avenue tunnel by a New York Central White Plains local, due to smoke and snow obscuring signals. Seventeen persons were killed and 36 injured, the worst rail accident in New York City history. The accident inspired the State Legislature to pass a law the next year prohibiting steam operation within the tunnels of New York City on the Park Avenue line south of the Harlem River.

...and visibility is not improved by bringing that still-hot steam locomotive. There's still combustion going on (it's still making smoke). There's still hot water in the boiler (it's still making steam). Steam locomotives cannot be "switched off" -- they must cool first. And they take a while to cool.

The usual method for suburban trains was for folks to simply change trains (they got legs) at the end of the electrified area. Changing trains is still done in places for various reasons (Mattapan Line, East Contra Costa BART). Sometimes the change station also meant changing companies or travel modes (Hoboken Terminal)

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  • $\begingroup$ you can dump the contents of a firebox into an ash pit & steam can be condensed $\endgroup$
    – OT-64 SKOT
    Apr 21, 2023 at 12:57
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    $\begingroup$ @OT-64SKOT dumping the firebox of every inbound suburban train simply buys you a flip-side problem for the corresponding outbound trip: Will all the passengers quietly wait 20-30 minutes for the firebox to heat back up? Just as cooling a steam locomotive is not instant, heating one up and building steam pressure is also not instant. You could keep it warm electrically...but that doesn't seem to meet your "efficient" criteria. $\endgroup$
    – user535733
    Apr 21, 2023 at 13:09
  • $\begingroup$ If you are willing to suspend the requirement for "most efficient", you could have massive coal-electric dual-modes with borg-like slant-mounted huge electric condensers and scrubbers, with their own radiators, plus a loco-mounted generator to power the control lines for push-pull operation. You could go to the extreme: Have the third rail merely powering the huge condensers and scrubbers, and keep using steam for motive power. Not a sane nor efficient setup, but completely steampunk-cool. Oh, and your tunnels will need more ventilation, obviously. $\endgroup$
    – user535733
    Apr 21, 2023 at 18:41
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Since your city already has a traditional steam locomotive rail system in place, the least expensive option to electrify only the most urban portion is to purchase or build an additional electric locomotive for each train.

For operations in the countryside, leave the electric locomotive parked at the end of the electrified part of the line, and attach the steam engine to the outbound end of the train.

For operations on the metro part of the network, attach the electric locomotive to the inbound (toward downtown) end of the train and leave the steam engine at the cutout.

Although this means that there is always one parked and idle locomotive for each train, at least you are not dragging useless equipment around all the time.

On the more active lines, with careful scheduling, you can probably increase overall efficiency by re-using one or both locos for another train instead of just parking it. You'll need a through siding at the changeover.

You'll notice that this method is very close to having separate urban and rural networks, except that you don't need to purchase any more passenger cars. Also your passengers can remain seated instead of changing trains.

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Frame Challange

Gasification

I'm going to go slightly different to everyone else. You have your standard electric motors driving the train and your coal powered generators providing electricity but you can run internal combustion on coal, diesel, or even wood in a pinch with gasification.

From Wikipedia

"In 1873, Thaddeus S. C. Lowe developed and patented the water gas process by which large amounts of hydrogen gas could be generated for residential and commercial use in heating and lighting. Unlike the common coal gas, or coke gas which was used in municipal service, this gas provided a more efficient heating fuel.

During the late 19th century internal combustion engines were commonly fueled by town gas, and during the early 20th century many stationary engines switched to using producer gas created from coke which was substantially cheaper than town gas which was based on the distillation (pyrolysis) of more expensive coal.

During World War II, gasoline was rationed and in short supply. Due to the lack of gasoline from petroleum, older people recalled how to build gasifiers for both wood and coal, and how to convert internal combustion engines to run on gaseous fuel, and wood gas generators were in active production. In Great Britain, France, the United States and Germany, large numbers of such generators were constructed or improvised to convert wood and coal into fuel for vehicles. Commercial generators were in production before and after the war for use in special circumstances or in distressed economies. Some World War II era wood gas generators were of the "Imbert" downdraft type, designed around 1920 by French inventor Georges Imbert."

The process is basically heating the fuel in an oxygen less environment to produce flammable gasses which are then injected into a standard internal combustion engine. As long as the fuel is carbon based, the engine will run on it. Rubbish burning generators run on this concept as it's cleaner burning and more efficient. It really doesn't matter the fuel you use.

With gasification, you need neither the boilers nor the water and your trains can run on electricity, wood, coal, diesel or even garbage. It will even burn cleaner than coal fired boilers.

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Well, the first hybrid car was for sale in 1907

https://en.m.wikipedia.org/wiki/Owen_Magnetic

so the power train technology is there, despite there then not being any hybrids from the 1920s until the 90s The trouble with what you suggest us that its rather difficult to heat up n shut down a steam engine, unless you use powderd coal. Even then the thermal mass is a problem

Id point out as far as injecting coal dust into a piston cylinder as per the other answer is concerned, that was the first thing Rudolf Diesel tried. Every attempt at this resulted in the engine siezing instantly. He eventually switched to oil, which we now know as diesel

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Conventional steam engine

All you do is change the heat source to make the steam: burn coal, burn oil, or electric element.

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Frame challenge

No bimodal trains

The suggested bimodal train might seem like a solution, but in reality it'll only make your initial problem much worse. Any transport with multiple kinds of energy sources have a huge problem. Each needs to carry the weight of the other engines, storage spaces and the like. That means that where you first had a regular coal steam train, it'll produce much more exhaust at those times if an oil and/or electricity system is added.

There's two ways to make it better. One is simply reduce the total exhaust by adding the electrified tracks. Each track that doesn't need a steam train is a net gain. It might already be enough. It does need some planning, possibly you need to transfer passengers on some stations for example.the second is where you build it. There's again two ways to go about it. Either you place the electrified trains in areas that require it the most, because if population density. Less exhaust for the masses. The second way is to do it for the rich and powerful first, leaving the masses under the exhaust until you can electrify those parts as well. The rich and powerful often coordinate these projects, so why would they not lift themselves out of the dregs of smoke and leave the inferior masses to their dirty lives?

TL:DR

Bimodal trains would likely increase the problem, as it needs to carry more weight in transport. Electrify the tracks strategically and you can simply reduce by having less steam trains.

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