I was thinking that it might be possible to replace batteries at rail stations. What might not be possible for consumer grade might work for professional grade. Basically, I’m trying to think of a ‘minimal infrastructure change’ electric train. Electrifying every foot of rail in the US would be expensive… so can we look at it another way?
I could be wrong but IIRC I once asked about why bother having a diesel-electric rather than just leave it a diesel engine around here once. It seemed to me there would be some inefficiencies that would creep in by making it a two-step process.
The answer, again IIRC, was that a diesel engine would require a transmission if it powered the locomotive directly. An electric motor needs no transmission.
So, they are the way they are not for efficiency but practicality. A transmission sufficient to handle the stress a locomotive would put on it would be difficult and impractical.
Nah, it just means diesel fuel is cheap. A diesel-electric system converts diesel fuel to heat, heat to motion, motion to electricity, electricity back to motion. There’s energy loss at every step. Energy-wise, it makes much more sense to eliminate two steps and drive the wheels directly with the diesel.
Why don’t they ? Your guess is as good as mine. I know why they do it on submarines (i.e. because diesels can’t run under water, and batteries don’t make noise) but not on trains. WAG : safer and easier to route electricity from a central generator to a bunch of identical traction motors than it is to have a bunch of more or less independent diesel engines for each set of traction wheels, each with their own reservoir, mechanical problems, synchronization problems…
You don’t want to pony up to electrify the tracks, but you want each podunk station to have a brand new hangar housing a reserve of spare batteries, a big hulking crane to put them in and out, and presumably a small power station to fill them up as well ? 
Not sure it’s a minimal investment either way.
Already answered this just above you.
Found my (very old) post where this is answered here: Locomotives and Diesel/Electric Engines - Factual Questions - Straight Dope Message Board
Correct.
Things have improved a bit since diesel-electrics first became the standard, but it’s still about the best way to do things like that. This is actually a source of frequent debate among the experts in the industry. Personally I don’t know the best answer.
Well, in the old days, each station had a waterhouse to refill the steam engine with, as I recall. But no, I wouldn’t say each. I was thinking maybe strategically significant switching points. That’s why I was asking if you could get an electric to go as far as a diesel on one tank of fuel. If not, how far could we get one to go?
Now, I’m not calling it a minimal investment, but I’m thinking as much about maintainability and repair as anything. And transmission loss.
Now I’m imagining a steampunk/postapoc movie in which the old, rusted, half-fallen down waterhouses are repurposed as battery changers.
Actually, something very much like that is being used in a few places…but it seems to be limited to short-distance streetcars and people movers. The railcar runs on batteries, at each station stop a moveable shoe drops down from the bottom of the car to make contact with a connector between the rails, and the batteries are given a quick mini-recharge - enough to get to the next stop. They also add charge by using the dynamic braking principle, changing over the traction motors to generators while going down-grade or braking for stations. As to why the system hasn’t been used in line-haul railroading, it’s probably because the batteries required for that kind of heavy-duty output would be impossibly massive and heavy.
Actually, the old-fashioned steam locomotive is not an entirely dead technology. The traditional recriprocating steam locomotive was a very inefficient machine in terms of BTU’s consumed per ton/mile, as well as being extremely maintenance-intensive but there have been some interesting experiments in that direction. A man named L.D. Porta, working in Argentina in the 1960’s made massive changes in the combustion and drafting patterns of steam engines and improved the effeciency considerably, but didn’t solve the heavy maintenance issues.
In the 1980’s an American inventor named Rowland sunk a great deal of his own and others’ money into a powdered-coal powered locomotive called the ACE3000, but ran out of funds before a prototype could be fully developed. Basically it utilized most of Porta’s ideas and a few others to improve the efficiency, but had the misfortune to come along at a time when everyone thought railroads themselves were on the verge of extinction - at least in the U.S.
One of the most intriguing developements in steam locomotive technology was just prior to WW 2, by a British company called Sentinal Waggon Works (so spelled). They built a completely radical type of locomotive, powered by a vertical water-tube boiler (essentially a flash boiler), and instead of the large drive wheels and massive side rods, mounted it on swivelling bogies (wheelsets) fore and aft, just like a modern diesel. A small 4 or 6 cylinder steam traction motor was mounted above each axle with a direct gear drive to the axle. A total of seven were built, 3 went to Belgium, and 2 each to Argentina and Columbia, where they proved very efficient and successful. Unfortunately, the company’s manufacturing facilities were so severely damaged by German bombing during the war that they never recovered, and advancements in diesel-locomotive technology following the war diverted any further interest in developing the concept.
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